Add protobuf 2.2.0a sources

This is the contents of protobuf-2.2.0a.tar.bz2 from
http://code.google.com/p/protobuf/downloads/list and
is the base code for the javamicro code generator.

Change-Id: Ie9a0440a824d615086445b6636944484b3155afa

29 files changed, 12559 insertions, 0 deletions

diff --git a/java/src/main/java/com/google/protobuf/AbstractMessage.java b/java/src/main/java/com/google/protobuf/AbstractMessage.java
new file mode 100644
index 0000000..e5bdefe
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/AbstractMessage.java
@@ -0,0 +1,690 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+import java.io.InputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A partial implementation of the {@link Message} interface which implements
+ * as many methods of that interface as possible in terms of other methods.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public abstract class AbstractMessage extends AbstractMessageLite
+                                      implements Message {
+  @SuppressWarnings("unchecked")
+  public boolean isInitialized() {
+    // Check that all required fields are present.
+    for (final FieldDescriptor field : getDescriptorForType().getFields()) {
+      if (field.isRequired()) {
+        if (!hasField(field)) {
+          return false;
+        }
+      }
+    }
+
+    // Check that embedded messages are initialized.
+    for (final Map.Entry<FieldDescriptor, Object> entry :
+        getAllFields().entrySet()) {
+      final FieldDescriptor field = entry.getKey();
+      if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+        if (field.isRepeated()) {
+          for (final Message element : (List<Message>) entry.getValue()) {
+            if (!element.isInitialized()) {
+              return false;
+            }
+          }
+        } else {
+          if (!((Message) entry.getValue()).isInitialized()) {
+            return false;
+          }
+        }
+      }
+    }
+
+    return true;
+  }
+
+  @Override
+  public final String toString() {
+    return TextFormat.printToString(this);
+  }
+
+  public void writeTo(final CodedOutputStream output) throws IOException {
+    final boolean isMessageSet =
+        getDescriptorForType().getOptions().getMessageSetWireFormat();
+
+    for (final Map.Entry<FieldDescriptor, Object> entry :
+        getAllFields().entrySet()) {
+      final FieldDescriptor field = entry.getKey();
+      final Object value = entry.getValue();
+      if (isMessageSet && field.isExtension() &&
+          field.getType() == FieldDescriptor.Type.MESSAGE &&
+          !field.isRepeated()) {
+        output.writeMessageSetExtension(field.getNumber(), (Message) value);
+      } else {
+        FieldSet.writeField(field, value, output);
+      }
+    }
+
+    final UnknownFieldSet unknownFields = getUnknownFields();
+    if (isMessageSet) {
+      unknownFields.writeAsMessageSetTo(output);
+    } else {
+      unknownFields.writeTo(output);
+    }
+  }
+
+  private int memoizedSize = -1;
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) {
+      return size;
+    }
+
+    size = 0;
+    final boolean isMessageSet =
+        getDescriptorForType().getOptions().getMessageSetWireFormat();
+
+    for (final Map.Entry<FieldDescriptor, Object> entry :
+        getAllFields().entrySet()) {
+      final FieldDescriptor field = entry.getKey();
+      final Object value = entry.getValue();
+      if (isMessageSet && field.isExtension() &&
+          field.getType() == FieldDescriptor.Type.MESSAGE &&
+          !field.isRepeated()) {
+        size += CodedOutputStream.computeMessageSetExtensionSize(
+            field.getNumber(), (Message) value);
+      } else {
+        size += FieldSet.computeFieldSize(field, value);
+      }
+    }
+
+    final UnknownFieldSet unknownFields = getUnknownFields();
+    if (isMessageSet) {
+      size += unknownFields.getSerializedSizeAsMessageSet();
+    } else {
+      size += unknownFields.getSerializedSize();
+    }
+
+    memoizedSize = size;
+    return size;
+  }
+
+  @Override
+  public boolean equals(final Object other) {
+    if (other == this) {
+      return true;
+    }
+    if (!(other instanceof Message)) {
+      return false;
+    }
+    final Message otherMessage = (Message) other;
+    if (getDescriptorForType() != otherMessage.getDescriptorForType()) {
+      return false;
+    }
+    return getAllFields().equals(otherMessage.getAllFields()) &&
+        getUnknownFields().equals(otherMessage.getUnknownFields());
+  }
+
+  @Override
+  public int hashCode() {
+    int hash = 41;
+    hash = (19 * hash) + getDescriptorForType().hashCode();
+    hash = (53 * hash) + getAllFields().hashCode();
+    hash = (29 * hash) + getUnknownFields().hashCode();
+    return hash;
+  }
+
+  // =================================================================
+
+  /**
+   * A partial implementation of the {@link Message.Builder} interface which
+   * implements as many methods of that interface as possible in terms of
+   * other methods.
+   */
+  @SuppressWarnings("unchecked")
+  public static abstract class Builder<BuilderType extends Builder>
+      extends AbstractMessageLite.Builder<BuilderType>
+      implements Message.Builder {
+    // The compiler produces an error if this is not declared explicitly.
+    @Override
+    public abstract BuilderType clone();
+
+    public BuilderType clear() {
+      for (final Map.Entry<FieldDescriptor, Object> entry :
+           getAllFields().entrySet()) {
+        clearField(entry.getKey());
+      }
+      return (BuilderType) this;
+    }
+
+    public BuilderType mergeFrom(final Message other) {
+      if (other.getDescriptorForType() != getDescriptorForType()) {
+        throw new IllegalArgumentException(
+          "mergeFrom(Message) can only merge messages of the same type.");
+      }
+
+      // Note:  We don't attempt to verify that other's fields have valid
+      //   types.  Doing so would be a losing battle.  We'd have to verify
+      //   all sub-messages as well, and we'd have to make copies of all of
+      //   them to insure that they don't change after verification (since
+      //   the Message interface itself cannot enforce immutability of
+      //   implementations).
+      // TODO(kenton):  Provide a function somewhere called makeDeepCopy()
+      //   which allows people to make secure deep copies of messages.
+
+      for (final Map.Entry<FieldDescriptor, Object> entry :
+           other.getAllFields().entrySet()) {
+        final FieldDescriptor field = entry.getKey();
+        if (field.isRepeated()) {
+          for (final Object element : (List)entry.getValue()) {
+            addRepeatedField(field, element);
+          }
+        } else if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+          final Message existingValue = (Message)getField(field);
+          if (existingValue == existingValue.getDefaultInstanceForType()) {
+            setField(field, entry.getValue());
+          } else {
+            setField(field,
+              existingValue.newBuilderForType()
+                .mergeFrom(existingValue)
+                .mergeFrom((Message)entry.getValue())
+                .build());
+          }
+        } else {
+          setField(field, entry.getValue());
+        }
+      }
+
+      mergeUnknownFields(other.getUnknownFields());
+
+      return (BuilderType) this;
+    }
+
+    @Override
+    public BuilderType mergeFrom(final CodedInputStream input)
+                                 throws IOException {
+      return mergeFrom(input, ExtensionRegistry.getEmptyRegistry());
+    }
+
+    @Override
+    public BuilderType mergeFrom(
+        final CodedInputStream input,
+        final ExtensionRegistryLite extensionRegistry)
+        throws IOException {
+      final UnknownFieldSet.Builder unknownFields =
+        UnknownFieldSet.newBuilder(getUnknownFields());
+      while (true) {
+        final int tag = input.readTag();
+        if (tag == 0) {
+          break;
+        }
+
+        if (!mergeFieldFrom(input, unknownFields, extensionRegistry,
+                            this, tag)) {
+          // end group tag
+          break;
+        }
+      }
+      setUnknownFields(unknownFields.build());
+      return (BuilderType) this;
+    }
+
+    /**
+     * Like {@link #mergeFrom(CodedInputStream, UnknownFieldSet.Builder,
+     * ExtensionRegistryLite, Message.Builder)}, but parses a single field.
+     * Package-private because it is used by GeneratedMessage.ExtendableMessage.
+     * @param tag The tag, which should have already been read.
+     * @return {@code true} unless the tag is an end-group tag.
+     */
+    @SuppressWarnings("unchecked")
+    static boolean mergeFieldFrom(
+        final CodedInputStream input,
+        final UnknownFieldSet.Builder unknownFields,
+        final ExtensionRegistryLite extensionRegistry,
+        final Message.Builder builder,
+        final int tag) throws IOException {
+      final Descriptor type = builder.getDescriptorForType();
+
+      if (type.getOptions().getMessageSetWireFormat() &&
+          tag == WireFormat.MESSAGE_SET_ITEM_TAG) {
+        mergeMessageSetExtensionFromCodedStream(
+          input, unknownFields, extensionRegistry, builder);
+        return true;
+      }
+
+      final int wireType = WireFormat.getTagWireType(tag);
+      final int fieldNumber = WireFormat.getTagFieldNumber(tag);
+
+      final FieldDescriptor field;
+      Message defaultInstance = null;
+
+      if (type.isExtensionNumber(fieldNumber)) {
+        // extensionRegistry may be either ExtensionRegistry or
+        // ExtensionRegistryLite.  Since the type we are parsing is a full
+        // message, only a full ExtensionRegistry could possibly contain
+        // extensions of it.  Otherwise we will treat the registry as if it
+        // were empty.
+        if (extensionRegistry instanceof ExtensionRegistry) {
+          final ExtensionRegistry.ExtensionInfo extension =
+            ((ExtensionRegistry) extensionRegistry)
+              .findExtensionByNumber(type, fieldNumber);
+          if (extension == null) {
+            field = null;
+          } else {
+            field = extension.descriptor;
+            defaultInstance = extension.defaultInstance;
+          }
+        } else {
+          field = null;
+        }
+      } else {
+        field = type.findFieldByNumber(fieldNumber);
+      }
+
+      if (field == null || wireType !=
+            FieldSet.getWireFormatForFieldType(
+                field.getLiteType(),
+                field.getOptions().getPacked())) {
+        // Unknown field or wrong wire type.  Skip.
+        return unknownFields.mergeFieldFrom(tag, input);
+      }
+
+      if (field.getOptions().getPacked()) {
+        final int length = input.readRawVarint32();
+        final int limit = input.pushLimit(length);
+        if (field.getLiteType() == WireFormat.FieldType.ENUM) {
+          while (input.getBytesUntilLimit() > 0) {
+            final int rawValue = input.readEnum();
+            final Object value = field.getEnumType().findValueByNumber(rawValue);
+            if (value == null) {
+              // If the number isn't recognized as a valid value for this
+              // enum, drop it (don't even add it to unknownFields).
+              return true;
+            }
+            builder.addRepeatedField(field, value);
+          }
+        } else {
+          while (input.getBytesUntilLimit() > 0) {
+            final Object value =
+              FieldSet.readPrimitiveField(input, field.getLiteType());
+            builder.addRepeatedField(field, value);
+          }
+        }
+        input.popLimit(limit);
+      } else {
+        final Object value;
+        switch (field.getType()) {
+          case GROUP: {
+            final Message.Builder subBuilder;
+            if (defaultInstance != null) {
+              subBuilder = defaultInstance.newBuilderForType();
+            } else {
+              subBuilder = builder.newBuilderForField(field);
+            }
+            if (!field.isRepeated()) {
+              subBuilder.mergeFrom((Message) builder.getField(field));
+            }
+            input.readGroup(field.getNumber(), subBuilder, extensionRegistry);
+            value = subBuilder.build();
+            break;
+          }
+          case MESSAGE: {
+            final Message.Builder subBuilder;
+            if (defaultInstance != null) {
+              subBuilder = defaultInstance.newBuilderForType();
+            } else {
+              subBuilder = builder.newBuilderForField(field);
+            }
+            if (!field.isRepeated()) {
+              subBuilder.mergeFrom((Message) builder.getField(field));
+            }
+            input.readMessage(subBuilder, extensionRegistry);
+            value = subBuilder.build();
+            break;
+          }
+          case ENUM:
+            final int rawValue = input.readEnum();
+            value = field.getEnumType().findValueByNumber(rawValue);
+            // If the number isn't recognized as a valid value for this enum,
+            // drop it.
+            if (value == null) {
+              unknownFields.mergeVarintField(fieldNumber, rawValue);
+              return true;
+            }
+            break;
+          default:
+            value = FieldSet.readPrimitiveField(input, field.getLiteType());
+            break;
+        }
+
+        if (field.isRepeated()) {
+          builder.addRepeatedField(field, value);
+        } else {
+          builder.setField(field, value);
+        }
+      }
+
+      return true;
+    }
+
+    /** Called by {@code #mergeFieldFrom()} to parse a MessageSet extension. */
+    private static void mergeMessageSetExtensionFromCodedStream(
+        final CodedInputStream input,
+        final UnknownFieldSet.Builder unknownFields,
+        final ExtensionRegistryLite extensionRegistry,
+        final Message.Builder builder) throws IOException {
+      final Descriptor type = builder.getDescriptorForType();
+
+      // The wire format for MessageSet is:
+      //   message MessageSet {
+      //     repeated group Item = 1 {
+      //       required int32 typeId = 2;
+      //       required bytes message = 3;
+      //     }
+      //   }
+      // "typeId" is the extension's field number.  The extension can only be
+      // a message type, where "message" contains the encoded bytes of that
+      // message.
+      //
+      // In practice, we will probably never see a MessageSet item in which
+      // the message appears before the type ID, or where either field does not
+      // appear exactly once.  However, in theory such cases are valid, so we
+      // should be prepared to accept them.
+
+      int typeId = 0;
+      ByteString rawBytes = null;  // If we encounter "message" before "typeId"
+      Message.Builder subBuilder = null;
+      FieldDescriptor field = null;
+
+      while (true) {
+        final int tag = input.readTag();
+        if (tag == 0) {
+          break;
+        }
+
+        if (tag == WireFormat.MESSAGE_SET_TYPE_ID_TAG) {
+          typeId = input.readUInt32();
+          // Zero is not a valid type ID.
+          if (typeId != 0) {
+            final ExtensionRegistry.ExtensionInfo extension;
+
+            // extensionRegistry may be either ExtensionRegistry or
+            // ExtensionRegistryLite.  Since the type we are parsing is a full
+            // message, only a full ExtensionRegistry could possibly contain
+            // extensions of it.  Otherwise we will treat the registry as if it
+            // were empty.
+            if (extensionRegistry instanceof ExtensionRegistry) {
+              extension = ((ExtensionRegistry) extensionRegistry)
+                  .findExtensionByNumber(type, typeId);
+            } else {
+              extension = null;
+            }
+
+            if (extension != null) {
+              field = extension.descriptor;
+              subBuilder = extension.defaultInstance.newBuilderForType();
+              final Message originalMessage = (Message)builder.getField(field);
+              if (originalMessage != null) {
+                subBuilder.mergeFrom(originalMessage);
+              }
+              if (rawBytes != null) {
+                // We already encountered the message.  Parse it now.
+                subBuilder.mergeFrom(
+                  CodedInputStream.newInstance(rawBytes.newInput()));
+                rawBytes = null;
+              }
+            } else {
+              // Unknown extension number.  If we already saw data, put it
+              // in rawBytes.
+              if (rawBytes != null) {
+                unknownFields.mergeField(typeId,
+                  UnknownFieldSet.Field.newBuilder()
+                    .addLengthDelimited(rawBytes)
+                    .build());
+                rawBytes = null;
+              }
+            }
+          }
+        } else if (tag == WireFormat.MESSAGE_SET_MESSAGE_TAG) {
+          if (typeId == 0) {
+            // We haven't seen a type ID yet, so we have to store the raw bytes
+            // for now.
+            rawBytes = input.readBytes();
+          } else if (subBuilder == null) {
+            // We don't know how to parse this.  Ignore it.
+            unknownFields.mergeField(typeId,
+              UnknownFieldSet.Field.newBuilder()
+                .addLengthDelimited(input.readBytes())
+                .build());
+          } else {
+            // We already know the type, so we can parse directly from the input
+            // with no copying.  Hooray!
+            input.readMessage(subBuilder, extensionRegistry);
+          }
+        } else {
+          // Unknown tag.  Skip it.
+          if (!input.skipField(tag)) {
+            break;  // end of group
+          }
+        }
+      }
+
+      input.checkLastTagWas(WireFormat.MESSAGE_SET_ITEM_END_TAG);
+
+      if (subBuilder != null) {
+        builder.setField(field, subBuilder.build());
+      }
+    }
+
+    public BuilderType mergeUnknownFields(final UnknownFieldSet unknownFields) {
+      setUnknownFields(
+        UnknownFieldSet.newBuilder(getUnknownFields())
+                       .mergeFrom(unknownFields)
+                       .build());
+      return (BuilderType) this;
+    }
+
+    /**
+     * Construct an UninitializedMessageException reporting missing fields in
+     * the given message.
+     */
+    protected static UninitializedMessageException
+        newUninitializedMessageException(Message message) {
+      return new UninitializedMessageException(findMissingFields(message));
+    }
+
+    /**
+     * Populates {@code this.missingFields} with the full "path" of each
+     * missing required field in the given message.
+     */
+    private static List<String> findMissingFields(final Message message) {
+      final List<String> results = new ArrayList<String>();
+      findMissingFields(message, "", results);
+      return results;
+    }
+
+    /** Recursive helper implementing {@link #findMissingFields(Message)}. */
+    private static void findMissingFields(final Message message,
+                                          final String prefix,
+                                          final List<String> results) {
+      for (final FieldDescriptor field :
+          message.getDescriptorForType().getFields()) {
+        if (field.isRequired() && !message.hasField(field)) {
+          results.add(prefix + field.getName());
+        }
+      }
+
+      for (final Map.Entry<FieldDescriptor, Object> entry :
+           message.getAllFields().entrySet()) {
+        final FieldDescriptor field = entry.getKey();
+        final Object value = entry.getValue();
+
+        if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+          if (field.isRepeated()) {
+            int i = 0;
+            for (final Object element : (List) value) {
+              findMissingFields((Message) element,
+                                subMessagePrefix(prefix, field, i++),
+                                results);
+            }
+          } else {
+            if (message.hasField(field)) {
+              findMissingFields((Message) value,
+                                subMessagePrefix(prefix, field, -1),
+                                results);
+            }
+          }
+        }
+      }
+    }
+
+    private static String subMessagePrefix(final String prefix,
+                                           final FieldDescriptor field,
+                                           final int index) {
+      final StringBuilder result = new StringBuilder(prefix);
+      if (field.isExtension()) {
+        result.append('(')
+              .append(field.getFullName())
+              .append(')');
+      } else {
+        result.append(field.getName());
+      }
+      if (index != -1) {
+        result.append('[')
+              .append(index)
+              .append(']');
+      }
+      result.append('.');
+      return result.toString();
+    }
+
+    // ===============================================================
+    // The following definitions seem to be required in order to make javac
+    // not produce weird errors like:
+    //
+    // java/com/google/protobuf/DynamicMessage.java:203: types
+    //   com.google.protobuf.AbstractMessage.Builder<
+    //     com.google.protobuf.DynamicMessage.Builder> and
+    //   com.google.protobuf.AbstractMessage.Builder<
+    //     com.google.protobuf.DynamicMessage.Builder> are incompatible; both
+    //   define mergeFrom(com.google.protobuf.ByteString), but with unrelated
+    //   return types.
+    //
+    // Strangely, these lines are only needed if javac is invoked separately
+    // on AbstractMessage.java and AbstractMessageLite.java.  If javac is
+    // invoked on both simultaneously, it works.  (Or maybe the important
+    // point is whether or not DynamicMessage.java is compiled together with
+    // AbstractMessageLite.java -- not sure.)  I suspect this is a compiler
+    // bug.
+
+    @Override
+    public BuilderType mergeFrom(final ByteString data)
+        throws InvalidProtocolBufferException {
+      return super.mergeFrom(data);
+    }
+
+    @Override
+    public BuilderType mergeFrom(
+        final ByteString data,
+        final ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      return super.mergeFrom(data, extensionRegistry);
+    }
+
+    @Override
+    public BuilderType mergeFrom(final byte[] data)
+        throws InvalidProtocolBufferException {
+      return super.mergeFrom(data);
+    }
+
+    @Override
+    public BuilderType mergeFrom(
+        final byte[] data, final int off, final int len)
+        throws InvalidProtocolBufferException {
+      return super.mergeFrom(data, off, len);
+    }
+
+    @Override
+    public BuilderType mergeFrom(
+        final byte[] data,
+        final ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      return super.mergeFrom(data, extensionRegistry);
+    }
+
+    @Override
+    public BuilderType mergeFrom(
+        final byte[] data, final int off, final int len,
+        final ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      return super.mergeFrom(data, off, len, extensionRegistry);
+    }
+
+    @Override
+    public BuilderType mergeFrom(final InputStream input)
+        throws IOException {
+      return super.mergeFrom(input);
+    }
+
+    @Override
+    public BuilderType mergeFrom(
+        final InputStream input,
+        final ExtensionRegistryLite extensionRegistry)
+        throws IOException {
+      return super.mergeFrom(input, extensionRegistry);
+    }
+
+    @Override
+    public BuilderType mergeDelimitedFrom(final InputStream input)
+        throws IOException {
+      return super.mergeDelimitedFrom(input);
+    }
+
+    @Override
+    public BuilderType mergeDelimitedFrom(
+        final InputStream input,
+        final ExtensionRegistryLite extensionRegistry)
+        throws IOException {
+      return super.mergeDelimitedFrom(input, extensionRegistry);
+    }
+
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/AbstractMessageLite.java b/java/src/main/java/com/google/protobuf/AbstractMessageLite.java
new file mode 100644
index 0000000..489577d
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/AbstractMessageLite.java
@@ -0,0 +1,321 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.FilterInputStream;
+import java.io.InputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Collection;
+
+/**
+ * A partial implementation of the {@link MessageLite} interface which
+ * implements as many methods of that interface as possible in terms of other
+ * methods.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public abstract class AbstractMessageLite implements MessageLite {
+  public ByteString toByteString() {
+    try {
+      final ByteString.CodedBuilder out =
+        ByteString.newCodedBuilder(getSerializedSize());
+      writeTo(out.getCodedOutput());
+      return out.build();
+    } catch (IOException e) {
+      throw new RuntimeException(
+        "Serializing to a ByteString threw an IOException (should " +
+        "never happen).", e);
+    }
+  }
+
+  public byte[] toByteArray() {
+    try {
+      final byte[] result = new byte[getSerializedSize()];
+      final CodedOutputStream output = CodedOutputStream.newInstance(result);
+      writeTo(output);
+      output.checkNoSpaceLeft();
+      return result;
+    } catch (IOException e) {
+      throw new RuntimeException(
+        "Serializing to a byte array threw an IOException " +
+        "(should never happen).", e);
+    }
+  }
+
+  public void writeTo(final OutputStream output) throws IOException {
+    final CodedOutputStream codedOutput = CodedOutputStream.newInstance(output);
+    writeTo(codedOutput);
+    codedOutput.flush();
+  }
+
+  public void writeDelimitedTo(final OutputStream output) throws IOException {
+    final CodedOutputStream codedOutput = CodedOutputStream.newInstance(output);
+    codedOutput.writeRawVarint32(getSerializedSize());
+    writeTo(codedOutput);
+    codedOutput.flush();
+  }
+
+  /**
+   * A partial implementation of the {@link Message.Builder} interface which
+   * implements as many methods of that interface as possible in terms of
+   * other methods.
+   */
+  @SuppressWarnings("unchecked")
+  public static abstract class Builder<BuilderType extends Builder>
+      implements MessageLite.Builder {
+    // The compiler produces an error if this is not declared explicitly.
+    @Override
+    public abstract BuilderType clone();
+
+    public BuilderType mergeFrom(final CodedInputStream input)
+                                 throws IOException {
+      // TODO(kenton):  Don't use null here.  Currently we have to because
+      //   using ExtensionRegistry.getEmptyRegistry() would imply a dependency
+      //   on ExtensionRegistry.  However, AbstractMessage overrides this with
+      //   a correct implementation, and lite messages don't yet support
+      //   extensions, so it ends up not mattering for now.  It will matter
+      //   once lite messages support extensions.
+      return mergeFrom(input, null);
+    }
+
+    // Re-defined here for return type covariance.
+    public abstract BuilderType mergeFrom(
+        final CodedInputStream input,
+        final ExtensionRegistryLite extensionRegistry)
+        throws IOException;
+
+    public BuilderType mergeFrom(final ByteString data)
+        throws InvalidProtocolBufferException {
+      try {
+        final CodedInputStream input = data.newCodedInput();
+        mergeFrom(input);
+        input.checkLastTagWas(0);
+        return (BuilderType) this;
+      } catch (InvalidProtocolBufferException e) {
+        throw e;
+      } catch (IOException e) {
+        throw new RuntimeException(
+          "Reading from a ByteString threw an IOException (should " +
+          "never happen).", e);
+      }
+    }
+
+    public BuilderType mergeFrom(
+        final ByteString data,
+        final ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      try {
+        final CodedInputStream input = data.newCodedInput();
+        mergeFrom(input, extensionRegistry);
+        input.checkLastTagWas(0);
+        return (BuilderType) this;
+      } catch (InvalidProtocolBufferException e) {
+        throw e;
+      } catch (IOException e) {
+        throw new RuntimeException(
+          "Reading from a ByteString threw an IOException (should " +
+          "never happen).", e);
+      }
+    }
+
+    public BuilderType mergeFrom(final byte[] data)
+        throws InvalidProtocolBufferException {
+      return mergeFrom(data, 0, data.length);
+    }
+
+    public BuilderType mergeFrom(final byte[] data, final int off,
+                                 final int len)
+                                 throws InvalidProtocolBufferException {
+      try {
+        final CodedInputStream input =
+            CodedInputStream.newInstance(data, off, len);
+        mergeFrom(input);
+        input.checkLastTagWas(0);
+        return (BuilderType) this;
+      } catch (InvalidProtocolBufferException e) {
+        throw e;
+      } catch (IOException e) {
+        throw new RuntimeException(
+          "Reading from a byte array threw an IOException (should " +
+          "never happen).", e);
+      }
+    }
+
+    public BuilderType mergeFrom(
+        final byte[] data,
+        final ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      return mergeFrom(data, 0, data.length, extensionRegistry);
+    }
+
+    public BuilderType mergeFrom(
+        final byte[] data, final int off, final int len,
+        final ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      try {
+        final CodedInputStream input =
+            CodedInputStream.newInstance(data, off, len);
+        mergeFrom(input, extensionRegistry);
+        input.checkLastTagWas(0);
+        return (BuilderType) this;
+      } catch (InvalidProtocolBufferException e) {
+        throw e;
+      } catch (IOException e) {
+        throw new RuntimeException(
+          "Reading from a byte array threw an IOException (should " +
+          "never happen).", e);
+      }
+    }
+
+    public BuilderType mergeFrom(final InputStream input) throws IOException {
+      final CodedInputStream codedInput = CodedInputStream.newInstance(input);
+      mergeFrom(codedInput);
+      codedInput.checkLastTagWas(0);
+      return (BuilderType) this;
+    }
+
+    public BuilderType mergeFrom(
+        final InputStream input,
+        final ExtensionRegistryLite extensionRegistry)
+        throws IOException {
+      final CodedInputStream codedInput = CodedInputStream.newInstance(input);
+      mergeFrom(codedInput, extensionRegistry);
+      codedInput.checkLastTagWas(0);
+      return (BuilderType) this;
+    }
+
+    /**
+     * An InputStream implementations which reads from some other InputStream
+     * but is limited to a particular number of bytes.  Used by
+     * mergeDelimitedFrom().  This is intentionally package-private so that
+     * UnknownFieldSet can share it.
+     */
+    static final class LimitedInputStream extends FilterInputStream {
+      private int limit;
+
+      LimitedInputStream(InputStream in, int limit) {
+        super(in);
+        this.limit = limit;
+      }
+
+      @Override
+      public int available() throws IOException {
+        return Math.min(super.available(), limit);
+      }
+
+      @Override
+      public int read() throws IOException {
+        if (limit <= 0) {
+          return -1;
+        }
+        final int result = super.read();
+        if (result >= 0) {
+          --limit;
+        }
+        return result;
+      }
+
+      @Override
+      public int read(final byte[] b, final int off, int len)
+                      throws IOException {
+        if (limit <= 0) {
+          return -1;
+        }
+        len = Math.min(len, limit);
+        final int result = super.read(b, off, len);
+        if (result >= 0) {
+          limit -= result;
+        }
+        return result;
+      }
+
+      @Override
+      public long skip(final long n) throws IOException {
+        final long result = super.skip(Math.min(n, limit));
+        if (result >= 0) {
+          limit -= result;
+        }
+        return result;
+      }
+    }
+
+    public BuilderType mergeDelimitedFrom(
+        final InputStream input,
+        final ExtensionRegistryLite extensionRegistry)
+        throws IOException {
+      final int size = CodedInputStream.readRawVarint32(input);
+      final InputStream limitedInput = new LimitedInputStream(input, size);
+      return mergeFrom(limitedInput, extensionRegistry);
+    }
+
+    public BuilderType mergeDelimitedFrom(final InputStream input)
+        throws IOException {
+      final int size = CodedInputStream.readRawVarint32(input);
+      final InputStream limitedInput = new LimitedInputStream(input, size);
+      return mergeFrom(limitedInput);
+    }
+
+    /**
+     * Construct an UninitializedMessageException reporting missing fields in
+     * the given message.
+     */
+    protected static UninitializedMessageException
+        newUninitializedMessageException(MessageLite message) {
+      return new UninitializedMessageException(message);
+    }
+
+    /**
+     * Adds the {@code values} to the {@code list}.  This is a helper method
+     * used by generated code.  Users should ignore it.
+     *
+     * @throws NullPointerException if any of the elements of {@code values} is
+     * null.
+     */
+    protected static <T> void addAll(final Iterable<T> values,
+                                     final Collection<? super T> list) {
+      for (final T value : values) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+      }
+      if (values instanceof Collection) {
+        @SuppressWarnings("unsafe") final
+        Collection<T> collection = (Collection<T>) values;
+        list.addAll(collection);
+      } else {
+        for (final T value : values) {
+          list.add(value);
+        }
+      }
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/BlockingRpcChannel.java b/java/src/main/java/com/google/protobuf/BlockingRpcChannel.java
new file mode 100644
index 0000000..1e81143
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/BlockingRpcChannel.java
@@ -0,0 +1,51 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * <p>Abstract interface for a blocking RPC channel.  {@code BlockingRpcChannel}
+ * is the blocking equivalent to {@link RpcChannel}.
+ *
+ * @author kenton@google.com Kenton Varda
+ * @author cpovirk@google.com Chris Povirk
+ */
+public interface BlockingRpcChannel {
+  /**
+   * Call the given method of the remote service and blocks until it returns.
+   * {@code callBlockingMethod()} is the blocking equivalent to
+   * {@link RpcChannel#callMethod}.
+   */
+  Message callBlockingMethod(
+      Descriptors.MethodDescriptor method,
+      RpcController controller,
+      Message request,
+      Message responsePrototype) throws ServiceException;
+}
diff --git a/java/src/main/java/com/google/protobuf/BlockingService.java b/java/src/main/java/com/google/protobuf/BlockingService.java
new file mode 100644
index 0000000..ecc8009
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/BlockingService.java
@@ -0,0 +1,64 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * Blocking equivalent to {@link Service}.
+ *
+ * @author kenton@google.com Kenton Varda
+ * @author cpovirk@google.com Chris Povirk
+ */
+public interface BlockingService {
+  /**
+   * Equivalent to {@link Service#getDescriptorForType}.
+   */
+  Descriptors.ServiceDescriptor getDescriptorForType();
+
+  /**
+   * Equivalent to {@link Service#callMethod}, except that
+   * {@code callBlockingMethod()} returns the result of the RPC or throws a
+   * {@link ServiceException} if there is a failure, rather than passing the
+   * information to a callback.
+   */
+  Message callBlockingMethod(Descriptors.MethodDescriptor method,
+                             RpcController controller,
+                             Message request) throws ServiceException;
+
+  /**
+   * Equivalent to {@link Service#getRequestPrototype}.
+   */
+  Message getRequestPrototype(Descriptors.MethodDescriptor method);
+
+  /**
+   * Equivalent to {@link Service#getResponsePrototype}.
+   */
+  Message getResponsePrototype(Descriptors.MethodDescriptor method);
+}
diff --git a/java/src/main/java/com/google/protobuf/ByteString.java b/java/src/main/java/com/google/protobuf/ByteString.java
new file mode 100644
index 0000000..c83c335
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/ByteString.java
@@ -0,0 +1,344 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.InputStream;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.FilterOutputStream;
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteBuffer;
+
+/**
+ * Immutable array of bytes.
+ *
+ * @author crazybob@google.com Bob Lee
+ * @author kenton@google.com Kenton Varda
+ */
+public final class ByteString {
+  private final byte[] bytes;
+
+  private ByteString(final byte[] bytes) {
+    this.bytes = bytes;
+  }
+
+  /**
+   * Gets the byte at the given index.
+   *
+   * @throws ArrayIndexOutOfBoundsException {@code index} is < 0 or >= size
+   */
+  public byte byteAt(final int index) {
+    return bytes[index];
+  }
+
+  /**
+   * Gets the number of bytes.
+   */
+  public int size() {
+    return bytes.length;
+  }
+
+  /**
+   * Returns {@code true} if the size is {@code 0}, {@code false} otherwise.
+   */
+  public boolean isEmpty() {
+    return bytes.length == 0;
+  }
+
+  // =================================================================
+  // byte[] -> ByteString
+
+  /**
+   * Empty ByteString.
+   */
+  public static final ByteString EMPTY = new ByteString(new byte[0]);
+
+  /**
+   * Copies the given bytes into a {@code ByteString}.
+   */
+  public static ByteString copyFrom(final byte[] bytes, final int offset,
+                                    final int size) {
+    final byte[] copy = new byte[size];
+    System.arraycopy(bytes, offset, copy, 0, size);
+    return new ByteString(copy);
+  }
+
+  /**
+   * Copies the given bytes into a {@code ByteString}.
+   */
+  public static ByteString copyFrom(final byte[] bytes) {
+    return copyFrom(bytes, 0, bytes.length);
+  }
+
+  /**
+   * Encodes {@code text} into a sequence of bytes using the named charset
+   * and returns the result as a {@code ByteString}.
+   */
+  public static ByteString copyFrom(final String text, final String charsetName)
+      throws UnsupportedEncodingException {
+    return new ByteString(text.getBytes(charsetName));
+  }
+
+  /**
+   * Encodes {@code text} into a sequence of UTF-8 bytes and returns the
+   * result as a {@code ByteString}.
+   */
+  public static ByteString copyFromUtf8(final String text) {
+    try {
+      return new ByteString(text.getBytes("UTF-8"));
+    } catch (UnsupportedEncodingException e) {
+      throw new RuntimeException("UTF-8 not supported?", e);
+    }
+  }
+
+  // =================================================================
+  // ByteString -> byte[]
+
+  /**
+   * Copies bytes into a buffer at the given offset.
+   *
+   * @param target buffer to copy into
+   * @param offset in the target buffer
+   */
+  public void copyTo(final byte[] target, final int offset) {
+    System.arraycopy(bytes, 0, target, offset, bytes.length);
+  }
+
+  /**
+   * Copies bytes into a buffer.
+   *
+   * @param target buffer to copy into
+   * @param sourceOffset offset within these bytes
+   * @param targetOffset offset within the target buffer
+   * @param size number of bytes to copy
+   */
+  public void copyTo(final byte[] target, final int sourceOffset,
+                     final int targetOffset,
+      final int size) {
+    System.arraycopy(bytes, sourceOffset, target, targetOffset, size);
+  }
+
+  /**
+   * Copies bytes to a {@code byte[]}.
+   */
+  public byte[] toByteArray() {
+    final int size = bytes.length;
+    final byte[] copy = new byte[size];
+    System.arraycopy(bytes, 0, copy, 0, size);
+    return copy;
+  }
+
+  /**
+   * Constructs a new read-only {@code java.nio.ByteBuffer} with the
+   * same backing byte array.
+   */
+  public ByteBuffer asReadOnlyByteBuffer() {
+    final ByteBuffer byteBuffer = ByteBuffer.wrap(bytes);
+    return byteBuffer.asReadOnlyBuffer();
+  }
+
+  /**
+   * Constructs a new {@code String} by decoding the bytes using the
+   * specified charset.
+   */
+  public String toString(final String charsetName)
+      throws UnsupportedEncodingException {
+    return new String(bytes, charsetName);
+  }
+
+  /**
+   * Constructs a new {@code String} by decoding the bytes as UTF-8.
+   */
+  public String toStringUtf8() {
+    try {
+      return new String(bytes, "UTF-8");
+    } catch (UnsupportedEncodingException e) {
+      throw new RuntimeException("UTF-8 not supported?", e);
+    }
+  }
+
+  // =================================================================
+  // equals() and hashCode()
+
+  @Override
+  public boolean equals(final Object o) {
+    if (o == this) {
+      return true;
+    }
+
+    if (!(o instanceof ByteString)) {
+      return false;
+    }
+
+    final ByteString other = (ByteString) o;
+    final int size = bytes.length;
+    if (size != other.bytes.length) {
+      return false;
+    }
+
+    final byte[] thisBytes = bytes;
+    final byte[] otherBytes = other.bytes;
+    for (int i = 0; i < size; i++) {
+      if (thisBytes[i] != otherBytes[i]) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  private volatile int hash = 0;
+
+  @Override
+  public int hashCode() {
+    int h = hash;
+
+    if (h == 0) {
+      final byte[] thisBytes = bytes;
+      final int size = bytes.length;
+
+      h = size;
+      for (int i = 0; i < size; i++) {
+        h = h * 31 + thisBytes[i];
+      }
+      if (h == 0) {
+        h = 1;
+      }
+
+      hash = h;
+    }
+
+    return h;
+  }
+
+  // =================================================================
+  // Input stream
+
+  /**
+   * Creates an {@code InputStream} which can be used to read the bytes.
+   */
+  public InputStream newInput() {
+    return new ByteArrayInputStream(bytes);
+  }
+
+  /**
+   * Creates a {@link CodedInputStream} which can be used to read the bytes.
+   * Using this is more efficient than creating a {@link CodedInputStream}
+   * wrapping the result of {@link #newInput()}.
+   */
+  public CodedInputStream newCodedInput() {
+    // We trust CodedInputStream not to modify the bytes, or to give anyone
+    // else access to them.
+    return CodedInputStream.newInstance(bytes);
+  }
+
+  // =================================================================
+  // Output stream
+
+  /**
+   * Creates a new {@link Output} with the given initial capacity.
+   */
+  public static Output newOutput(final int initialCapacity) {
+    return new Output(new ByteArrayOutputStream(initialCapacity));
+  }
+
+  /**
+   * Creates a new {@link Output}.
+   */
+  public static Output newOutput() {
+    return newOutput(32);
+  }
+
+  /**
+   * Outputs to a {@code ByteString} instance. Call {@link #toByteString()} to
+   * create the {@code ByteString} instance.
+   */
+  public static final class Output extends FilterOutputStream {
+    private final ByteArrayOutputStream bout;
+
+    /**
+     * Constructs a new output with the given initial capacity.
+     */
+    private Output(final ByteArrayOutputStream bout) {
+      super(bout);
+      this.bout = bout;
+    }
+
+    /**
+     * Creates a {@code ByteString} instance from this {@code Output}.
+     */
+    public ByteString toByteString() {
+      final byte[] byteArray = bout.toByteArray();
+      return new ByteString(byteArray);
+    }
+  }
+
+  /**
+   * Constructs a new ByteString builder, which allows you to efficiently
+   * construct a {@code ByteString} by writing to a {@link CodedOutputStream}.
+   * Using this is much more efficient than calling {@code newOutput()} and
+   * wrapping that in a {@code CodedOutputStream}.
+   *
+   * <p>This is package-private because it's a somewhat confusing interface.
+   * Users can call {@link Message#toByteString()} instead of calling this
+   * directly.
+   *
+   * @param size The target byte size of the {@code ByteString}.  You must
+   *             write exactly this many bytes before building the result.
+   */
+  static CodedBuilder newCodedBuilder(final int size) {
+    return new CodedBuilder(size);
+  }
+
+  /** See {@link ByteString#newCodedBuilder(int)}. */
+  static final class CodedBuilder {
+    private final CodedOutputStream output;
+    private final byte[] buffer;
+
+    private CodedBuilder(final int size) {
+      buffer = new byte[size];
+      output = CodedOutputStream.newInstance(buffer);
+    }
+
+    public ByteString build() {
+      output.checkNoSpaceLeft();
+
+      // We can be confident that the CodedOutputStream will not modify the
+      // underlying bytes anymore because it already wrote all of them.  So,
+      // no need to make a copy.
+      return new ByteString(buffer);
+    }
+
+    public CodedOutputStream getCodedOutput() {
+      return output;
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/CodedInputStream.java b/java/src/main/java/com/google/protobuf/CodedInputStream.java
new file mode 100644
index 0000000..9125957
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/CodedInputStream.java
@@ -0,0 +1,826 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Reads and decodes protocol message fields.
+ *
+ * This class contains two kinds of methods:  methods that read specific
+ * protocol message constructs and field types (e.g. {@link #readTag()} and
+ * {@link #readInt32()}) and methods that read low-level values (e.g.
+ * {@link #readRawVarint32()} and {@link #readRawBytes}).  If you are reading
+ * encoded protocol messages, you should use the former methods, but if you are
+ * reading some other format of your own design, use the latter.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class CodedInputStream {
+  /**
+   * Create a new CodedInputStream wrapping the given InputStream.
+   */
+  public static CodedInputStream newInstance(final InputStream input) {
+    return new CodedInputStream(input);
+  }
+
+  /**
+   * Create a new CodedInputStream wrapping the given byte array.
+   */
+  public static CodedInputStream newInstance(final byte[] buf) {
+    return newInstance(buf, 0, buf.length);
+  }
+
+  /**
+   * Create a new CodedInputStream wrapping the given byte array slice.
+   */
+  public static CodedInputStream newInstance(final byte[] buf, final int off,
+                                             final int len) {
+    return new CodedInputStream(buf, off, len);
+  }
+
+  // -----------------------------------------------------------------
+
+  /**
+   * Attempt to read a field tag, returning zero if we have reached EOF.
+   * Protocol message parsers use this to read tags, since a protocol message
+   * may legally end wherever a tag occurs, and zero is not a valid tag number.
+   */
+  public int readTag() throws IOException {
+    if (isAtEnd()) {
+      lastTag = 0;
+      return 0;
+    }
+
+    lastTag = readRawVarint32();
+    if (lastTag == 0) {
+      // If we actually read zero, that's not a valid tag.
+      throw InvalidProtocolBufferException.invalidTag();
+    }
+    return lastTag;
+  }
+
+  /**
+   * Verifies that the last call to readTag() returned the given tag value.
+   * This is used to verify that a nested group ended with the correct
+   * end tag.
+   *
+   * @throws InvalidProtocolBufferException {@code value} does not match the
+   *                                        last tag.
+   */
+  public void checkLastTagWas(final int value)
+                              throws InvalidProtocolBufferException {
+    if (lastTag != value) {
+      throw InvalidProtocolBufferException.invalidEndTag();
+    }
+  }
+
+  /**
+   * Reads and discards a single field, given its tag value.
+   *
+   * @return {@code false} if the tag is an endgroup tag, in which case
+   *         nothing is skipped.  Otherwise, returns {@code true}.
+   */
+  public boolean skipField(final int tag) throws IOException {
+    switch (WireFormat.getTagWireType(tag)) {
+      case WireFormat.WIRETYPE_VARINT:
+        readInt32();
+        return true;
+      case WireFormat.WIRETYPE_FIXED64:
+        readRawLittleEndian64();
+        return true;
+      case WireFormat.WIRETYPE_LENGTH_DELIMITED:
+        skipRawBytes(readRawVarint32());
+        return true;
+      case WireFormat.WIRETYPE_START_GROUP:
+        skipMessage();
+        checkLastTagWas(
+          WireFormat.makeTag(WireFormat.getTagFieldNumber(tag),
+                             WireFormat.WIRETYPE_END_GROUP));
+        return true;
+      case WireFormat.WIRETYPE_END_GROUP:
+        return false;
+      case WireFormat.WIRETYPE_FIXED32:
+        readRawLittleEndian32();
+        return true;
+      default:
+        throw InvalidProtocolBufferException.invalidWireType();
+    }
+  }
+
+  /**
+   * Reads and discards an entire message.  This will read either until EOF
+   * or until an endgroup tag, whichever comes first.
+   */
+  public void skipMessage() throws IOException {
+    while (true) {
+      final int tag = readTag();
+      if (tag == 0 || !skipField(tag)) {
+        return;
+      }
+    }
+  }
+
+  // -----------------------------------------------------------------
+
+  /** Read a {@code double} field value from the stream. */
+  public double readDouble() throws IOException {
+    return Double.longBitsToDouble(readRawLittleEndian64());
+  }
+
+  /** Read a {@code float} field value from the stream. */
+  public float readFloat() throws IOException {
+    return Float.intBitsToFloat(readRawLittleEndian32());
+  }
+
+  /** Read a {@code uint64} field value from the stream. */
+  public long readUInt64() throws IOException {
+    return readRawVarint64();
+  }
+
+  /** Read an {@code int64} field value from the stream. */
+  public long readInt64() throws IOException {
+    return readRawVarint64();
+  }
+
+  /** Read an {@code int32} field value from the stream. */
+  public int readInt32() throws IOException {
+    return readRawVarint32();
+  }
+
+  /** Read a {@code fixed64} field value from the stream. */
+  public long readFixed64() throws IOException {
+    return readRawLittleEndian64();
+  }
+
+  /** Read a {@code fixed32} field value from the stream. */
+  public int readFixed32() throws IOException {
+    return readRawLittleEndian32();
+  }
+
+  /** Read a {@code bool} field value from the stream. */
+  public boolean readBool() throws IOException {
+    return readRawVarint32() != 0;
+  }
+
+  /** Read a {@code string} field value from the stream. */
+  public String readString() throws IOException {
+    final int size = readRawVarint32();
+    if (size <= (bufferSize - bufferPos) && size > 0) {
+      // Fast path:  We already have the bytes in a contiguous buffer, so
+      //   just copy directly from it.
+      final String result = new String(buffer, bufferPos, size, "UTF-8");
+      bufferPos += size;
+      return result;
+    } else {
+      // Slow path:  Build a byte array first then copy it.
+      return new String(readRawBytes(size), "UTF-8");
+    }
+  }
+
+  /** Read a {@code group} field value from the stream. */
+  public void readGroup(final int fieldNumber,
+                        final MessageLite.Builder builder,
+                        final ExtensionRegistryLite extensionRegistry)
+      throws IOException {
+    if (recursionDepth >= recursionLimit) {
+      throw InvalidProtocolBufferException.recursionLimitExceeded();
+    }
+    ++recursionDepth;
+    builder.mergeFrom(this, extensionRegistry);
+    checkLastTagWas(
+      WireFormat.makeTag(fieldNumber, WireFormat.WIRETYPE_END_GROUP));
+    --recursionDepth;
+  }
+
+  /**
+   * Reads a {@code group} field value from the stream and merges it into the
+   * given {@link UnknownFieldSet}.
+   *
+   * @deprecated UnknownFieldSet.Builder now implements MessageLite.Builder, so
+   *             you can just call {@link #readGroup}.
+   */
+  @Deprecated
+  public void readUnknownGroup(final int fieldNumber,
+                               final MessageLite.Builder builder)
+      throws IOException {
+    // We know that UnknownFieldSet will ignore any ExtensionRegistry so it
+    // is safe to pass null here.  (We can't call
+    // ExtensionRegistry.getEmptyRegistry() because that would make this
+    // class depend on ExtensionRegistry, which is not part of the lite
+    // library.)
+    readGroup(fieldNumber, builder, null);
+  }
+
+  /** Read an embedded message field value from the stream. */
+  public void readMessage(final MessageLite.Builder builder,
+                          final ExtensionRegistryLite extensionRegistry)
+      throws IOException {
+    final int length = readRawVarint32();
+    if (recursionDepth >= recursionLimit) {
+      throw InvalidProtocolBufferException.recursionLimitExceeded();
+    }
+    final int oldLimit = pushLimit(length);
+    ++recursionDepth;
+    builder.mergeFrom(this, extensionRegistry);
+    checkLastTagWas(0);
+    --recursionDepth;
+    popLimit(oldLimit);
+  }
+
+  /** Read a {@code bytes} field value from the stream. */
+  public ByteString readBytes() throws IOException {
+    final int size = readRawVarint32();
+    if (size <= (bufferSize - bufferPos) && size > 0) {
+      // Fast path:  We already have the bytes in a contiguous buffer, so
+      //   just copy directly from it.
+      final ByteString result = ByteString.copyFrom(buffer, bufferPos, size);
+      bufferPos += size;
+      return result;
+    } else {
+      // Slow path:  Build a byte array first then copy it.
+      return ByteString.copyFrom(readRawBytes(size));
+    }
+  }
+
+  /** Read a {@code uint32} field value from the stream. */
+  public int readUInt32() throws IOException {
+    return readRawVarint32();
+  }
+
+  /**
+   * Read an enum field value from the stream.  Caller is responsible
+   * for converting the numeric value to an actual enum.
+   */
+  public int readEnum() throws IOException {
+    return readRawVarint32();
+  }
+
+  /** Read an {@code sfixed32} field value from the stream. */
+  public int readSFixed32() throws IOException {
+    return readRawLittleEndian32();
+  }
+
+  /** Read an {@code sfixed64} field value from the stream. */
+  public long readSFixed64() throws IOException {
+    return readRawLittleEndian64();
+  }
+
+  /** Read an {@code sint32} field value from the stream. */
+  public int readSInt32() throws IOException {
+    return decodeZigZag32(readRawVarint32());
+  }
+
+  /** Read an {@code sint64} field value from the stream. */
+  public long readSInt64() throws IOException {
+    return decodeZigZag64(readRawVarint64());
+  }
+
+  // =================================================================
+
+  /**
+   * Read a raw Varint from the stream.  If larger than 32 bits, discard the
+   * upper bits.
+   */
+  public int readRawVarint32() throws IOException {
+    byte tmp = readRawByte();
+    if (tmp >= 0) {
+      return tmp;
+    }
+    int result = tmp & 0x7f;
+    if ((tmp = readRawByte()) >= 0) {
+      result |= tmp << 7;
+    } else {
+      result |= (tmp & 0x7f) << 7;
+      if ((tmp = readRawByte()) >= 0) {
+        result |= tmp << 14;
+      } else {
+        result |= (tmp & 0x7f) << 14;
+        if ((tmp = readRawByte()) >= 0) {
+          result |= tmp << 21;
+        } else {
+          result |= (tmp & 0x7f) << 21;
+          result |= (tmp = readRawByte()) << 28;
+          if (tmp < 0) {
+            // Discard upper 32 bits.
+            for (int i = 0; i < 5; i++) {
+              if (readRawByte() >= 0) {
+                return result;
+              }
+            }
+            throw InvalidProtocolBufferException.malformedVarint();
+          }
+        }
+      }
+    }
+    return result;
+  }
+
+  /**
+   * Reads a varint from the input one byte at a time, so that it does not
+   * read any bytes after the end of the varint.  If you simply wrapped the
+   * stream in a CodedInputStream and used {@link #readRawVarint32(InputStream)}
+   * then you would probably end up reading past the end of the varint since
+   * CodedInputStream buffers its input.
+   */
+  static int readRawVarint32(final InputStream input) throws IOException {
+    int result = 0;
+    int offset = 0;
+    for (; offset < 32; offset += 7) {
+      final int b = input.read();
+      if (b == -1) {
+        throw InvalidProtocolBufferException.truncatedMessage();
+      }
+      result |= (b & 0x7f) << offset;
+      if ((b & 0x80) == 0) {
+        return result;
+      }
+    }
+    // Keep reading up to 64 bits.
+    for (; offset < 64; offset += 7) {
+      final int b = input.read();
+      if (b == -1) {
+        throw InvalidProtocolBufferException.truncatedMessage();
+      }
+      if ((b & 0x80) == 0) {
+        return result;
+      }
+    }
+    throw InvalidProtocolBufferException.malformedVarint();
+  }
+
+  /** Read a raw Varint from the stream. */
+  public long readRawVarint64() throws IOException {
+    int shift = 0;
+    long result = 0;
+    while (shift < 64) {
+      final byte b = readRawByte();
+      result |= (long)(b & 0x7F) << shift;
+      if ((b & 0x80) == 0) {
+        return result;
+      }
+      shift += 7;
+    }
+    throw InvalidProtocolBufferException.malformedVarint();
+  }
+
+  /** Read a 32-bit little-endian integer from the stream. */
+  public int readRawLittleEndian32() throws IOException {
+    final byte b1 = readRawByte();
+    final byte b2 = readRawByte();
+    final byte b3 = readRawByte();
+    final byte b4 = readRawByte();
+    return (((int)b1 & 0xff)      ) |
+           (((int)b2 & 0xff) <<  8) |
+           (((int)b3 & 0xff) << 16) |
+           (((int)b4 & 0xff) << 24);
+  }
+
+  /** Read a 64-bit little-endian integer from the stream. */
+  public long readRawLittleEndian64() throws IOException {
+    final byte b1 = readRawByte();
+    final byte b2 = readRawByte();
+    final byte b3 = readRawByte();
+    final byte b4 = readRawByte();
+    final byte b5 = readRawByte();
+    final byte b6 = readRawByte();
+    final byte b7 = readRawByte();
+    final byte b8 = readRawByte();
+    return (((long)b1 & 0xff)      ) |
+           (((long)b2 & 0xff) <<  8) |
+           (((long)b3 & 0xff) << 16) |
+           (((long)b4 & 0xff) << 24) |
+           (((long)b5 & 0xff) << 32) |
+           (((long)b6 & 0xff) << 40) |
+           (((long)b7 & 0xff) << 48) |
+           (((long)b8 & 0xff) << 56);
+  }
+
+  /**
+   * Decode a ZigZag-encoded 32-bit value.  ZigZag encodes signed integers
+   * into values that can be efficiently encoded with varint.  (Otherwise,
+   * negative values must be sign-extended to 64 bits to be varint encoded,
+   * thus always taking 10 bytes on the wire.)
+   *
+   * @param n An unsigned 32-bit integer, stored in a signed int because
+   *          Java has no explicit unsigned support.
+   * @return A signed 32-bit integer.
+   */
+  public static int decodeZigZag32(final int n) {
+    return (n >>> 1) ^ -(n & 1);
+  }
+
+  /**
+   * Decode a ZigZag-encoded 64-bit value.  ZigZag encodes signed integers
+   * into values that can be efficiently encoded with varint.  (Otherwise,
+   * negative values must be sign-extended to 64 bits to be varint encoded,
+   * thus always taking 10 bytes on the wire.)
+   *
+   * @param n An unsigned 64-bit integer, stored in a signed int because
+   *          Java has no explicit unsigned support.
+   * @return A signed 64-bit integer.
+   */
+  public static long decodeZigZag64(final long n) {
+    return (n >>> 1) ^ -(n & 1);
+  }
+
+  // -----------------------------------------------------------------
+
+  private final byte[] buffer;
+  private int bufferSize;
+  private int bufferSizeAfterLimit;
+  private int bufferPos;
+  private final InputStream input;
+  private int lastTag;
+
+  /**
+   * The total number of bytes read before the current buffer.  The total
+   * bytes read up to the current position can be computed as
+   * {@code totalBytesRetired + bufferPos}.
+   */
+  private int totalBytesRetired;
+
+  /** The absolute position of the end of the current message. */
+  private int currentLimit = Integer.MAX_VALUE;
+
+  /** See setRecursionLimit() */
+  private int recursionDepth;
+  private int recursionLimit = DEFAULT_RECURSION_LIMIT;
+
+  /** See setSizeLimit() */
+  private int sizeLimit = DEFAULT_SIZE_LIMIT;
+
+  private static final int DEFAULT_RECURSION_LIMIT = 64;
+  private static final int DEFAULT_SIZE_LIMIT = 64 << 20;  // 64MB
+  private static final int BUFFER_SIZE = 4096;
+
+  private CodedInputStream(final byte[] buffer, final int off, final int len) {
+    this.buffer = buffer;
+    bufferSize = off + len;
+    bufferPos = off;
+    input = null;
+  }
+
+  private CodedInputStream(final InputStream input) {
+    buffer = new byte[BUFFER_SIZE];
+    bufferSize = 0;
+    bufferPos = 0;
+    this.input = input;
+  }
+
+  /**
+   * Set the maximum message recursion depth.  In order to prevent malicious
+   * messages from causing stack overflows, {@code CodedInputStream} limits
+   * how deeply messages may be nested.  The default limit is 64.
+   *
+   * @return the old limit.
+   */
+  public int setRecursionLimit(final int limit) {
+    if (limit < 0) {
+      throw new IllegalArgumentException(
+        "Recursion limit cannot be negative: " + limit);
+    }
+    final int oldLimit = recursionLimit;
+    recursionLimit = limit;
+    return oldLimit;
+  }
+
+  /**
+   * Set the maximum message size.  In order to prevent malicious
+   * messages from exhausting memory or causing integer overflows,
+   * {@code CodedInputStream} limits how large a message may be.
+   * The default limit is 64MB.  You should set this limit as small
+   * as you can without harming your app's functionality.  Note that
+   * size limits only apply when reading from an {@code InputStream}, not
+   * when constructed around a raw byte array (nor with
+   * {@link ByteString#newCodedInput}).
+   * <p>
+   * If you want to read several messages from a single CodedInputStream, you
+   * could call {@link #resetSizeCounter()} after each one to avoid hitting the
+   * size limit.
+   *
+   * @return the old limit.
+   */
+  public int setSizeLimit(final int limit) {
+    if (limit < 0) {
+      throw new IllegalArgumentException(
+        "Size limit cannot be negative: " + limit);
+    }
+    final int oldLimit = sizeLimit;
+    sizeLimit = limit;
+    return oldLimit;
+  }
+
+  /**
+   * Resets the current size counter to zero (see {@link #setSizeLimit(int)}).
+   */
+  public void resetSizeCounter() {
+    totalBytesRetired = 0;
+  }
+
+  /**
+   * Sets {@code currentLimit} to (current position) + {@code byteLimit}.  This
+   * is called when descending into a length-delimited embedded message.
+   *
+   * @return the old limit.
+   */
+  public int pushLimit(int byteLimit) throws InvalidProtocolBufferException {
+    if (byteLimit < 0) {
+      throw InvalidProtocolBufferException.negativeSize();
+    }
+    byteLimit += totalBytesRetired + bufferPos;
+    final int oldLimit = currentLimit;
+    if (byteLimit > oldLimit) {
+      throw InvalidProtocolBufferException.truncatedMessage();
+    }
+    currentLimit = byteLimit;
+
+    recomputeBufferSizeAfterLimit();
+
+    return oldLimit;
+  }
+
+  private void recomputeBufferSizeAfterLimit() {
+    bufferSize += bufferSizeAfterLimit;
+    final int bufferEnd = totalBytesRetired + bufferSize;
+    if (bufferEnd > currentLimit) {
+      // Limit is in current buffer.
+      bufferSizeAfterLimit = bufferEnd - currentLimit;
+      bufferSize -= bufferSizeAfterLimit;
+    } else {
+      bufferSizeAfterLimit = 0;
+    }
+  }
+
+  /**
+   * Discards the current limit, returning to the previous limit.
+   *
+   * @param oldLimit The old limit, as returned by {@code pushLimit}.
+   */
+  public void popLimit(final int oldLimit) {
+    currentLimit = oldLimit;
+    recomputeBufferSizeAfterLimit();
+  }
+
+  /**
+   * Returns the number of bytes to be read before the current limit.
+   * If no limit is set, returns -1.
+   */
+  public int getBytesUntilLimit() {
+    if (currentLimit == Integer.MAX_VALUE) {
+      return -1;
+    }
+
+    final int currentAbsolutePosition = totalBytesRetired + bufferPos;
+    return currentLimit - currentAbsolutePosition;
+  }
+
+  /**
+   * Returns true if the stream has reached the end of the input.  This is the
+   * case if either the end of the underlying input source has been reached or
+   * if the stream has reached a limit created using {@link #pushLimit(int)}.
+   */
+  public boolean isAtEnd() throws IOException {
+    return bufferPos == bufferSize && !refillBuffer(false);
+  }
+
+  /**
+   * Called with {@code this.buffer} is empty to read more bytes from the
+   * input.  If {@code mustSucceed} is true, refillBuffer() gurantees that
+   * either there will be at least one byte in the buffer when it returns
+   * or it will throw an exception.  If {@code mustSucceed} is false,
+   * refillBuffer() returns false if no more bytes were available.
+   */
+  private boolean refillBuffer(final boolean mustSucceed) throws IOException {
+    if (bufferPos < bufferSize) {
+      throw new IllegalStateException(
+        "refillBuffer() called when buffer wasn't empty.");
+    }
+
+    if (totalBytesRetired + bufferSize == currentLimit) {
+      // Oops, we hit a limit.
+      if (mustSucceed) {
+        throw InvalidProtocolBufferException.truncatedMessage();
+      } else {
+        return false;
+      }
+    }
+
+    totalBytesRetired += bufferSize;
+
+    bufferPos = 0;
+    bufferSize = (input == null) ? -1 : input.read(buffer);
+    if (bufferSize == 0 || bufferSize < -1) {
+      throw new IllegalStateException(
+          "InputStream#read(byte[]) returned invalid result: " + bufferSize +
+          "\nThe InputStream implementation is buggy.");
+    }
+    if (bufferSize == -1) {
+      bufferSize = 0;
+      if (mustSucceed) {
+        throw InvalidProtocolBufferException.truncatedMessage();
+      } else {
+        return false;
+      }
+    } else {
+      recomputeBufferSizeAfterLimit();
+      final int totalBytesRead =
+        totalBytesRetired + bufferSize + bufferSizeAfterLimit;
+      if (totalBytesRead > sizeLimit || totalBytesRead < 0) {
+        throw InvalidProtocolBufferException.sizeLimitExceeded();
+      }
+      return true;
+    }
+  }
+
+  /**
+   * Read one byte from the input.
+   *
+   * @throws InvalidProtocolBufferException The end of the stream or the current
+   *                                        limit was reached.
+   */
+  public byte readRawByte() throws IOException {
+    if (bufferPos == bufferSize) {
+      refillBuffer(true);
+    }
+    return buffer[bufferPos++];
+  }
+
+  /**
+   * Read a fixed size of bytes from the input.
+   *
+   * @throws InvalidProtocolBufferException The end of the stream or the current
+   *                                        limit was reached.
+   */
+  public byte[] readRawBytes(final int size) throws IOException {
+    if (size < 0) {
+      throw InvalidProtocolBufferException.negativeSize();
+    }
+
+    if (totalBytesRetired + bufferPos + size > currentLimit) {
+      // Read to the end of the stream anyway.
+      skipRawBytes(currentLimit - totalBytesRetired - bufferPos);
+      // Then fail.
+      throw InvalidProtocolBufferException.truncatedMessage();
+    }
+
+    if (size <= bufferSize - bufferPos) {
+      // We have all the bytes we need already.
+      final byte[] bytes = new byte[size];
+      System.arraycopy(buffer, bufferPos, bytes, 0, size);
+      bufferPos += size;
+      return bytes;
+    } else if (size < BUFFER_SIZE) {
+      // Reading more bytes than are in the buffer, but not an excessive number
+      // of bytes.  We can safely allocate the resulting array ahead of time.
+
+      // First copy what we have.
+      final byte[] bytes = new byte[size];
+      int pos = bufferSize - bufferPos;
+      System.arraycopy(buffer, bufferPos, bytes, 0, pos);
+      bufferPos = bufferSize;
+
+      // We want to use refillBuffer() and then copy from the buffer into our
+      // byte array rather than reading directly into our byte array because
+      // the input may be unbuffered.
+      refillBuffer(true);
+
+      while (size - pos > bufferSize) {
+        System.arraycopy(buffer, 0, bytes, pos, bufferSize);
+        pos += bufferSize;
+        bufferPos = bufferSize;
+        refillBuffer(true);
+      }
+
+      System.arraycopy(buffer, 0, bytes, pos, size - pos);
+      bufferPos = size - pos;
+
+      return bytes;
+    } else {
+      // The size is very large.  For security reasons, we can't allocate the
+      // entire byte array yet.  The size comes directly from the input, so a
+      // maliciously-crafted message could provide a bogus very large size in
+      // order to trick the app into allocating a lot of memory.  We avoid this
+      // by allocating and reading only a small chunk at a time, so that the
+      // malicious message must actually *be* extremely large to cause
+      // problems.  Meanwhile, we limit the allowed size of a message elsewhere.
+
+      // Remember the buffer markers since we'll have to copy the bytes out of
+      // it later.
+      final int originalBufferPos = bufferPos;
+      final int originalBufferSize = bufferSize;
+
+      // Mark the current buffer consumed.
+      totalBytesRetired += bufferSize;
+      bufferPos = 0;
+      bufferSize = 0;
+
+      // Read all the rest of the bytes we need.
+      int sizeLeft = size - (originalBufferSize - originalBufferPos);
+      final List<byte[]> chunks = new ArrayList<byte[]>();
+
+      while (sizeLeft > 0) {
+        final byte[] chunk = new byte[Math.min(sizeLeft, BUFFER_SIZE)];
+        int pos = 0;
+        while (pos < chunk.length) {
+          final int n = (input == null) ? -1 :
+            input.read(chunk, pos, chunk.length - pos);
+          if (n == -1) {
+            throw InvalidProtocolBufferException.truncatedMessage();
+          }
+          totalBytesRetired += n;
+          pos += n;
+        }
+        sizeLeft -= chunk.length;
+        chunks.add(chunk);
+      }
+
+      // OK, got everything.  Now concatenate it all into one buffer.
+      final byte[] bytes = new byte[size];
+
+      // Start by copying the leftover bytes from this.buffer.
+      int pos = originalBufferSize - originalBufferPos;
+      System.arraycopy(buffer, originalBufferPos, bytes, 0, pos);
+
+      // And now all the chunks.
+      for (final byte[] chunk : chunks) {
+        System.arraycopy(chunk, 0, bytes, pos, chunk.length);
+        pos += chunk.length;
+      }
+
+      // Done.
+      return bytes;
+    }
+  }
+
+  /**
+   * Reads and discards {@code size} bytes.
+   *
+   * @throws InvalidProtocolBufferException The end of the stream or the current
+   *                                        limit was reached.
+   */
+  public void skipRawBytes(final int size) throws IOException {
+    if (size < 0) {
+      throw InvalidProtocolBufferException.negativeSize();
+    }
+
+    if (totalBytesRetired + bufferPos + size > currentLimit) {
+      // Read to the end of the stream anyway.
+      skipRawBytes(currentLimit - totalBytesRetired - bufferPos);
+      // Then fail.
+      throw InvalidProtocolBufferException.truncatedMessage();
+    }
+
+    if (size <= bufferSize - bufferPos) {
+      // We have all the bytes we need already.
+      bufferPos += size;
+    } else {
+      // Skipping more bytes than are in the buffer.  First skip what we have.
+      int pos = bufferSize - bufferPos;
+      totalBytesRetired += pos;
+      bufferPos = 0;
+      bufferSize = 0;
+
+      // Then skip directly from the InputStream for the rest.
+      while (pos < size) {
+        final int n = (input == null) ? -1 : (int) input.skip(size - pos);
+        if (n <= 0) {
+          throw InvalidProtocolBufferException.truncatedMessage();
+        }
+        pos += n;
+        totalBytesRetired += n;
+      }
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/CodedOutputStream.java b/java/src/main/java/com/google/protobuf/CodedOutputStream.java
new file mode 100644
index 0000000..d3907a7
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/CodedOutputStream.java
@@ -0,0 +1,1017 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.OutputStream;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+
+/**
+ * Encodes and writes protocol message fields.
+ *
+ * <p>This class contains two kinds of methods:  methods that write specific
+ * protocol message constructs and field types (e.g. {@link #writeTag} and
+ * {@link #writeInt32}) and methods that write low-level values (e.g.
+ * {@link #writeRawVarint32} and {@link #writeRawBytes}).  If you are
+ * writing encoded protocol messages, you should use the former methods, but if
+ * you are writing some other format of your own design, use the latter.
+ *
+ * <p>This class is totally unsynchronized.
+ *
+ * @author kneton@google.com Kenton Varda
+ */
+public final class CodedOutputStream {
+  private final byte[] buffer;
+  private final int limit;
+  private int position;
+
+  private final OutputStream output;
+
+  /**
+   * The buffer size used in {@link #newInstance(OutputStream)}.
+   */
+  public static final int DEFAULT_BUFFER_SIZE = 4096;
+
+  private CodedOutputStream(final byte[] buffer, final int offset,
+                            final int length) {
+    output = null;
+    this.buffer = buffer;
+    position = offset;
+    limit = offset + length;
+  }
+
+  private CodedOutputStream(final OutputStream output, final byte[] buffer) {
+    this.output = output;
+    this.buffer = buffer;
+    position = 0;
+    limit = buffer.length;
+  }
+
+  /**
+   * Create a new {@code CodedOutputStream} wrapping the given
+   * {@code OutputStream}.
+   */
+  public static CodedOutputStream newInstance(final OutputStream output) {
+    return newInstance(output, DEFAULT_BUFFER_SIZE);
+  }
+
+  /**
+   * Create a new {@code CodedOutputStream} wrapping the given
+   * {@code OutputStream} with a given buffer size.
+   */
+  public static CodedOutputStream newInstance(final OutputStream output,
+      final int bufferSize) {
+    return new CodedOutputStream(output, new byte[bufferSize]);
+  }
+
+  /**
+   * Create a new {@code CodedOutputStream} that writes directly to the given
+   * byte array.  If more bytes are written than fit in the array,
+   * {@link OutOfSpaceException} will be thrown.  Writing directly to a flat
+   * array is faster than writing to an {@code OutputStream}.  See also
+   * {@link ByteString#newCodedBuilder}.
+   */
+  public static CodedOutputStream newInstance(final byte[] flatArray) {
+    return newInstance(flatArray, 0, flatArray.length);
+  }
+
+  /**
+   * Create a new {@code CodedOutputStream} that writes directly to the given
+   * byte array slice.  If more bytes are written than fit in the slice,
+   * {@link OutOfSpaceException} will be thrown.  Writing directly to a flat
+   * array is faster than writing to an {@code OutputStream}.  See also
+   * {@link ByteString#newCodedBuilder}.
+   */
+  public static CodedOutputStream newInstance(final byte[] flatArray,
+                                              final int offset,
+                                              final int length) {
+    return new CodedOutputStream(flatArray, offset, length);
+  }
+
+  // -----------------------------------------------------------------
+
+  /** Write a {@code double} field, including tag, to the stream. */
+  public void writeDouble(final int fieldNumber, final double value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_FIXED64);
+    writeDoubleNoTag(value);
+  }
+
+  /** Write a {@code float} field, including tag, to the stream. */
+  public void writeFloat(final int fieldNumber, final float value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_FIXED32);
+    writeFloatNoTag(value);
+  }
+
+  /** Write a {@code uint64} field, including tag, to the stream. */
+  public void writeUInt64(final int fieldNumber, final long value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_VARINT);
+    writeUInt64NoTag(value);
+  }
+
+  /** Write an {@code int64} field, including tag, to the stream. */
+  public void writeInt64(final int fieldNumber, final long value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_VARINT);
+    writeInt64NoTag(value);
+  }
+
+  /** Write an {@code int32} field, including tag, to the stream. */
+  public void writeInt32(final int fieldNumber, final int value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_VARINT);
+    writeInt32NoTag(value);
+  }
+
+  /** Write a {@code fixed64} field, including tag, to the stream. */
+  public void writeFixed64(final int fieldNumber, final long value)
+                           throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_FIXED64);
+    writeFixed64NoTag(value);
+  }
+
+  /** Write a {@code fixed32} field, including tag, to the stream. */
+  public void writeFixed32(final int fieldNumber, final int value)
+                           throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_FIXED32);
+    writeFixed32NoTag(value);
+  }
+
+  /** Write a {@code bool} field, including tag, to the stream. */
+  public void writeBool(final int fieldNumber, final boolean value)
+                        throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_VARINT);
+    writeBoolNoTag(value);
+  }
+
+  /** Write a {@code string} field, including tag, to the stream. */
+  public void writeString(final int fieldNumber, final String value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_LENGTH_DELIMITED);
+    writeStringNoTag(value);
+  }
+
+  /** Write a {@code group} field, including tag, to the stream. */
+  public void writeGroup(final int fieldNumber, final MessageLite value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_START_GROUP);
+    writeGroupNoTag(value);
+    writeTag(fieldNumber, WireFormat.WIRETYPE_END_GROUP);
+  }
+
+  /**
+   * Write a group represented by an {@link UnknownFieldSet}.
+   *
+   * @deprecated UnknownFieldSet now implements MessageLite, so you can just
+   *             call {@link #writeGroup}.
+   */
+  @Deprecated
+  public void writeUnknownGroup(final int fieldNumber,
+                                final MessageLite value)
+                                throws IOException {
+    writeGroup(fieldNumber, value);
+  }
+
+  /** Write an embedded message field, including tag, to the stream. */
+  public void writeMessage(final int fieldNumber, final MessageLite value)
+                           throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_LENGTH_DELIMITED);
+    writeMessageNoTag(value);
+  }
+
+  /** Write a {@code bytes} field, including tag, to the stream. */
+  public void writeBytes(final int fieldNumber, final ByteString value)
+                         throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_LENGTH_DELIMITED);
+    writeBytesNoTag(value);
+  }
+
+  /** Write a {@code uint32} field, including tag, to the stream. */
+  public void writeUInt32(final int fieldNumber, final int value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_VARINT);
+    writeUInt32NoTag(value);
+  }
+
+  /**
+   * Write an enum field, including tag, to the stream.  Caller is responsible
+   * for converting the enum value to its numeric value.
+   */
+  public void writeEnum(final int fieldNumber, final int value)
+                        throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_VARINT);
+    writeEnumNoTag(value);
+  }
+
+  /** Write an {@code sfixed32} field, including tag, to the stream. */
+  public void writeSFixed32(final int fieldNumber, final int value)
+                            throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_FIXED32);
+    writeSFixed32NoTag(value);
+  }
+
+  /** Write an {@code sfixed64} field, including tag, to the stream. */
+  public void writeSFixed64(final int fieldNumber, final long value)
+                            throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_FIXED64);
+    writeSFixed64NoTag(value);
+  }
+
+  /** Write an {@code sint32} field, including tag, to the stream. */
+  public void writeSInt32(final int fieldNumber, final int value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_VARINT);
+    writeSInt32NoTag(value);
+  }
+
+  /** Write an {@code sint64} field, including tag, to the stream. */
+  public void writeSInt64(final int fieldNumber, final long value)
+                          throws IOException {
+    writeTag(fieldNumber, WireFormat.WIRETYPE_VARINT);
+    writeSInt64NoTag(value);
+  }
+
+  /**
+   * Write a MessageSet extension field to the stream.  For historical reasons,
+   * the wire format differs from normal fields.
+   */
+  public void writeMessageSetExtension(final int fieldNumber,
+                                       final MessageLite value)
+                                       throws IOException {
+    writeTag(WireFormat.MESSAGE_SET_ITEM, WireFormat.WIRETYPE_START_GROUP);
+    writeUInt32(WireFormat.MESSAGE_SET_TYPE_ID, fieldNumber);
+    writeMessage(WireFormat.MESSAGE_SET_MESSAGE, value);
+    writeTag(WireFormat.MESSAGE_SET_ITEM, WireFormat.WIRETYPE_END_GROUP);
+  }
+
+  /**
+   * Write an unparsed MessageSet extension field to the stream.  For
+   * historical reasons, the wire format differs from normal fields.
+   */
+  public void writeRawMessageSetExtension(final int fieldNumber,
+                                          final ByteString value)
+                                          throws IOException {
+    writeTag(WireFormat.MESSAGE_SET_ITEM, WireFormat.WIRETYPE_START_GROUP);
+    writeUInt32(WireFormat.MESSAGE_SET_TYPE_ID, fieldNumber);
+    writeBytes(WireFormat.MESSAGE_SET_MESSAGE, value);
+    writeTag(WireFormat.MESSAGE_SET_ITEM, WireFormat.WIRETYPE_END_GROUP);
+  }
+
+  // -----------------------------------------------------------------
+
+  /** Write a {@code double} field to the stream. */
+  public void writeDoubleNoTag(final double value) throws IOException {
+    writeRawLittleEndian64(Double.doubleToRawLongBits(value));
+  }
+
+  /** Write a {@code float} field to the stream. */
+  public void writeFloatNoTag(final float value) throws IOException {
+    writeRawLittleEndian32(Float.floatToRawIntBits(value));
+  }
+
+  /** Write a {@code uint64} field to the stream. */
+  public void writeUInt64NoTag(final long value) throws IOException {
+    writeRawVarint64(value);
+  }
+
+  /** Write an {@code int64} field to the stream. */
+  public void writeInt64NoTag(final long value) throws IOException {
+    writeRawVarint64(value);
+  }
+
+  /** Write an {@code int32} field to the stream. */
+  public void writeInt32NoTag(final int value) throws IOException {
+    if (value >= 0) {
+      writeRawVarint32(value);
+    } else {
+      // Must sign-extend.
+      writeRawVarint64(value);
+    }
+  }
+
+  /** Write a {@code fixed64} field to the stream. */
+  public void writeFixed64NoTag(final long value) throws IOException {
+    writeRawLittleEndian64(value);
+  }
+
+  /** Write a {@code fixed32} field to the stream. */
+  public void writeFixed32NoTag(final int value) throws IOException {
+    writeRawLittleEndian32(value);
+  }
+
+  /** Write a {@code bool} field to the stream. */
+  public void writeBoolNoTag(final boolean value) throws IOException {
+    writeRawByte(value ? 1 : 0);
+  }
+
+  /** Write a {@code string} field to the stream. */
+  public void writeStringNoTag(final String value) throws IOException {
+    // Unfortunately there does not appear to be any way to tell Java to encode
+    // UTF-8 directly into our buffer, so we have to let it create its own byte
+    // array and then copy.
+    final byte[] bytes = value.getBytes("UTF-8");
+    writeRawVarint32(bytes.length);
+    writeRawBytes(bytes);
+  }
+
+  /** Write a {@code group} field to the stream. */
+  public void writeGroupNoTag(final MessageLite value) throws IOException {
+    value.writeTo(this);
+  }
+
+  /**
+   * Write a group represented by an {@link UnknownFieldSet}.
+   *
+   * @deprecated UnknownFieldSet now implements MessageLite, so you can just
+   *             call {@link #writeGroupNoTag}.
+   */
+  @Deprecated
+  public void writeUnknownGroupNoTag(final MessageLite value)
+      throws IOException {
+    writeGroupNoTag(value);
+  }
+
+  /** Write an embedded message field to the stream. */
+  public void writeMessageNoTag(final MessageLite value) throws IOException {
+    writeRawVarint32(value.getSerializedSize());
+    value.writeTo(this);
+  }
+
+  /** Write a {@code bytes} field to the stream. */
+  public void writeBytesNoTag(final ByteString value) throws IOException {
+    final byte[] bytes = value.toByteArray();
+    writeRawVarint32(bytes.length);
+    writeRawBytes(bytes);
+  }
+
+  /** Write a {@code uint32} field to the stream. */
+  public void writeUInt32NoTag(final int value) throws IOException {
+    writeRawVarint32(value);
+  }
+
+  /**
+   * Write an enum field to the stream.  Caller is responsible
+   * for converting the enum value to its numeric value.
+   */
+  public void writeEnumNoTag(final int value) throws IOException {
+    writeRawVarint32(value);
+  }
+
+  /** Write an {@code sfixed32} field to the stream. */
+  public void writeSFixed32NoTag(final int value) throws IOException {
+    writeRawLittleEndian32(value);
+  }
+
+  /** Write an {@code sfixed64} field to the stream. */
+  public void writeSFixed64NoTag(final long value) throws IOException {
+    writeRawLittleEndian64(value);
+  }
+
+  /** Write an {@code sint32} field to the stream. */
+  public void writeSInt32NoTag(final int value) throws IOException {
+    writeRawVarint32(encodeZigZag32(value));
+  }
+
+  /** Write an {@code sint64} field to the stream. */
+  public void writeSInt64NoTag(final long value) throws IOException {
+    writeRawVarint64(encodeZigZag64(value));
+  }
+
+  // =================================================================
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code double} field, including tag.
+   */
+  public static int computeDoubleSize(final int fieldNumber,
+                                      final double value) {
+    return computeTagSize(fieldNumber) + computeDoubleSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code float} field, including tag.
+   */
+  public static int computeFloatSize(final int fieldNumber, final float value) {
+    return computeTagSize(fieldNumber) + computeFloatSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code uint64} field, including tag.
+   */
+  public static int computeUInt64Size(final int fieldNumber, final long value) {
+    return computeTagSize(fieldNumber) + computeUInt64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code int64} field, including tag.
+   */
+  public static int computeInt64Size(final int fieldNumber, final long value) {
+    return computeTagSize(fieldNumber) + computeInt64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code int32} field, including tag.
+   */
+  public static int computeInt32Size(final int fieldNumber, final int value) {
+    return computeTagSize(fieldNumber) + computeInt32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code fixed64} field, including tag.
+   */
+  public static int computeFixed64Size(final int fieldNumber,
+                                       final long value) {
+    return computeTagSize(fieldNumber) + computeFixed64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code fixed32} field, including tag.
+   */
+  public static int computeFixed32Size(final int fieldNumber,
+                                       final int value) {
+    return computeTagSize(fieldNumber) + computeFixed32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code bool} field, including tag.
+   */
+  public static int computeBoolSize(final int fieldNumber,
+                                    final boolean value) {
+    return computeTagSize(fieldNumber) + computeBoolSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code string} field, including tag.
+   */
+  public static int computeStringSize(final int fieldNumber,
+                                      final String value) {
+    return computeTagSize(fieldNumber) + computeStringSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code group} field, including tag.
+   */
+  public static int computeGroupSize(final int fieldNumber,
+                                     final MessageLite value) {
+    return computeTagSize(fieldNumber) * 2 + computeGroupSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code group} field represented by an {@code UnknownFieldSet}, including
+   * tag.
+   *
+   * @deprecated UnknownFieldSet now implements MessageLite, so you can just
+   *             call {@link #computeGroupSize}.
+   */
+  @Deprecated
+  public static int computeUnknownGroupSize(final int fieldNumber,
+                                            final MessageLite value) {
+    return computeGroupSize(fieldNumber, value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * embedded message field, including tag.
+   */
+  public static int computeMessageSize(final int fieldNumber,
+                                       final MessageLite value) {
+    return computeTagSize(fieldNumber) + computeMessageSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code bytes} field, including tag.
+   */
+  public static int computeBytesSize(final int fieldNumber,
+                                     final ByteString value) {
+    return computeTagSize(fieldNumber) + computeBytesSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code uint32} field, including tag.
+   */
+  public static int computeUInt32Size(final int fieldNumber, final int value) {
+    return computeTagSize(fieldNumber) + computeUInt32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * enum field, including tag.  Caller is responsible for converting the
+   * enum value to its numeric value.
+   */
+  public static int computeEnumSize(final int fieldNumber, final int value) {
+    return computeTagSize(fieldNumber) + computeEnumSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sfixed32} field, including tag.
+   */
+  public static int computeSFixed32Size(final int fieldNumber,
+                                        final int value) {
+    return computeTagSize(fieldNumber) + computeSFixed32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sfixed64} field, including tag.
+   */
+  public static int computeSFixed64Size(final int fieldNumber,
+                                        final long value) {
+    return computeTagSize(fieldNumber) + computeSFixed64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sint32} field, including tag.
+   */
+  public static int computeSInt32Size(final int fieldNumber, final int value) {
+    return computeTagSize(fieldNumber) + computeSInt32SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sint64} field, including tag.
+   */
+  public static int computeSInt64Size(final int fieldNumber, final long value) {
+    return computeTagSize(fieldNumber) + computeSInt64SizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * MessageSet extension to the stream.  For historical reasons,
+   * the wire format differs from normal fields.
+   */
+  public static int computeMessageSetExtensionSize(
+      final int fieldNumber, final MessageLite value) {
+    return computeTagSize(WireFormat.MESSAGE_SET_ITEM) * 2 +
+           computeUInt32Size(WireFormat.MESSAGE_SET_TYPE_ID, fieldNumber) +
+           computeMessageSize(WireFormat.MESSAGE_SET_MESSAGE, value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * unparsed MessageSet extension field to the stream.  For
+   * historical reasons, the wire format differs from normal fields.
+   */
+  public static int computeRawMessageSetExtensionSize(
+      final int fieldNumber, final ByteString value) {
+    return computeTagSize(WireFormat.MESSAGE_SET_ITEM) * 2 +
+           computeUInt32Size(WireFormat.MESSAGE_SET_TYPE_ID, fieldNumber) +
+           computeBytesSize(WireFormat.MESSAGE_SET_MESSAGE, value);
+  }
+
+  // -----------------------------------------------------------------
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code double} field, including tag.
+   */
+  public static int computeDoubleSizeNoTag(final double value) {
+    return LITTLE_ENDIAN_64_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code float} field, including tag.
+   */
+  public static int computeFloatSizeNoTag(final float value) {
+    return LITTLE_ENDIAN_32_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code uint64} field, including tag.
+   */
+  public static int computeUInt64SizeNoTag(final long value) {
+    return computeRawVarint64Size(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code int64} field, including tag.
+   */
+  public static int computeInt64SizeNoTag(final long value) {
+    return computeRawVarint64Size(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code int32} field, including tag.
+   */
+  public static int computeInt32SizeNoTag(final int value) {
+    if (value >= 0) {
+      return computeRawVarint32Size(value);
+    } else {
+      // Must sign-extend.
+      return 10;
+    }
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code fixed64} field.
+   */
+  public static int computeFixed64SizeNoTag(final long value) {
+    return LITTLE_ENDIAN_64_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code fixed32} field.
+   */
+  public static int computeFixed32SizeNoTag(final int value) {
+    return LITTLE_ENDIAN_32_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code bool} field.
+   */
+  public static int computeBoolSizeNoTag(final boolean value) {
+    return 1;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code string} field.
+   */
+  public static int computeStringSizeNoTag(final String value) {
+    try {
+      final byte[] bytes = value.getBytes("UTF-8");
+      return computeRawVarint32Size(bytes.length) +
+             bytes.length;
+    } catch (UnsupportedEncodingException e) {
+      throw new RuntimeException("UTF-8 not supported.", e);
+    }
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code group} field.
+   */
+  public static int computeGroupSizeNoTag(final MessageLite value) {
+    return value.getSerializedSize();
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code group} field represented by an {@code UnknownFieldSet}, including
+   * tag.
+   *
+   * @deprecated UnknownFieldSet now implements MessageLite, so you can just
+   *             call {@link #computeUnknownGroupSizeNoTag}.
+   */
+  @Deprecated
+  public static int computeUnknownGroupSizeNoTag(final MessageLite value) {
+    return computeGroupSizeNoTag(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an embedded
+   * message field.
+   */
+  public static int computeMessageSizeNoTag(final MessageLite value) {
+    final int size = value.getSerializedSize();
+    return computeRawVarint32Size(size) + size;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code bytes} field.
+   */
+  public static int computeBytesSizeNoTag(final ByteString value) {
+    return computeRawVarint32Size(value.size()) +
+           value.size();
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * {@code uint32} field.
+   */
+  public static int computeUInt32SizeNoTag(final int value) {
+    return computeRawVarint32Size(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an enum field.
+   * Caller is responsible for converting the enum value to its numeric value.
+   */
+  public static int computeEnumSizeNoTag(final int value) {
+    return computeRawVarint32Size(value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sfixed32} field.
+   */
+  public static int computeSFixed32SizeNoTag(final int value) {
+    return LITTLE_ENDIAN_32_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sfixed64} field.
+   */
+  public static int computeSFixed64SizeNoTag(final long value) {
+    return LITTLE_ENDIAN_64_SIZE;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sint32} field.
+   */
+  public static int computeSInt32SizeNoTag(final int value) {
+    return computeRawVarint32Size(encodeZigZag32(value));
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode an
+   * {@code sint64} field.
+   */
+  public static int computeSInt64SizeNoTag(final long value) {
+    return computeRawVarint64Size(encodeZigZag64(value));
+  }
+
+  // =================================================================
+
+  /**
+   * Internal helper that writes the current buffer to the output. The
+   * buffer position is reset to its initial value when this returns.
+   */
+  private void refreshBuffer() throws IOException {
+    if (output == null) {
+      // We're writing to a single buffer.
+      throw new OutOfSpaceException();
+    }
+
+    // Since we have an output stream, this is our buffer
+    // and buffer offset == 0
+    output.write(buffer, 0, position);
+    position = 0;
+  }
+
+  /**
+   * Flushes the stream and forces any buffered bytes to be written.  This
+   * does not flush the underlying OutputStream.
+   */
+  public void flush() throws IOException {
+    if (output != null) {
+      refreshBuffer();
+    }
+  }
+
+  /**
+   * If writing to a flat array, return the space left in the array.
+   * Otherwise, throws {@code UnsupportedOperationException}.
+   */
+  public int spaceLeft() {
+    if (output == null) {
+      return limit - position;
+    } else {
+      throw new UnsupportedOperationException(
+        "spaceLeft() can only be called on CodedOutputStreams that are " +
+        "writing to a flat array.");
+    }
+  }
+
+  /**
+   * Verifies that {@link #spaceLeft()} returns zero.  It's common to create
+   * a byte array that is exactly big enough to hold a message, then write to
+   * it with a {@code CodedOutputStream}.  Calling {@code checkNoSpaceLeft()}
+   * after writing verifies that the message was actually as big as expected,
+   * which can help catch bugs.
+   */
+  public void checkNoSpaceLeft() {
+    if (spaceLeft() != 0) {
+      throw new IllegalStateException(
+        "Did not write as much data as expected.");
+    }
+  }
+
+  /**
+   * If you create a CodedOutputStream around a simple flat array, you must
+   * not attempt to write more bytes than the array has space.  Otherwise,
+   * this exception will be thrown.
+   */
+  public static class OutOfSpaceException extends IOException {
+    private static final long serialVersionUID = -6947486886997889499L;
+
+    OutOfSpaceException() {
+      super("CodedOutputStream was writing to a flat byte array and ran " +
+            "out of space.");
+    }
+  }
+
+  /** Write a single byte. */
+  public void writeRawByte(final byte value) throws IOException {
+    if (position == limit) {
+      refreshBuffer();
+    }
+
+    buffer[position++] = value;
+  }
+
+  /** Write a single byte, represented by an integer value. */
+  public void writeRawByte(final int value) throws IOException {
+    writeRawByte((byte) value);
+  }
+
+  /** Write an array of bytes. */
+  public void writeRawBytes(final byte[] value) throws IOException {
+    writeRawBytes(value, 0, value.length);
+  }
+
+  /** Write part of an array of bytes. */
+  public void writeRawBytes(final byte[] value, int offset, int length)
+                            throws IOException {
+    if (limit - position >= length) {
+      // We have room in the current buffer.
+      System.arraycopy(value, offset, buffer, position, length);
+      position += length;
+    } else {
+      // Write extends past current buffer.  Fill the rest of this buffer and
+      // flush.
+      final int bytesWritten = limit - position;
+      System.arraycopy(value, offset, buffer, position, bytesWritten);
+      offset += bytesWritten;
+      length -= bytesWritten;
+      position = limit;
+      refreshBuffer();
+
+      // Now deal with the rest.
+      // Since we have an output stream, this is our buffer
+      // and buffer offset == 0
+      if (length <= limit) {
+        // Fits in new buffer.
+        System.arraycopy(value, offset, buffer, 0, length);
+        position = length;
+      } else {
+        // Write is very big.  Let's do it all at once.
+        output.write(value, offset, length);
+      }
+    }
+  }
+
+  /** Encode and write a tag. */
+  public void writeTag(final int fieldNumber, final int wireType)
+                       throws IOException {
+    writeRawVarint32(WireFormat.makeTag(fieldNumber, wireType));
+  }
+
+  /** Compute the number of bytes that would be needed to encode a tag. */
+  public static int computeTagSize(final int fieldNumber) {
+    return computeRawVarint32Size(WireFormat.makeTag(fieldNumber, 0));
+  }
+
+  /**
+   * Encode and write a varint.  {@code value} is treated as
+   * unsigned, so it won't be sign-extended if negative.
+   */
+  public void writeRawVarint32(int value) throws IOException {
+    while (true) {
+      if ((value & ~0x7F) == 0) {
+        writeRawByte(value);
+        return;
+      } else {
+        writeRawByte((value & 0x7F) | 0x80);
+        value >>>= 7;
+      }
+    }
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a varint.
+   * {@code value} is treated as unsigned, so it won't be sign-extended if
+   * negative.
+   */
+  public static int computeRawVarint32Size(final int value) {
+    if ((value & (0xffffffff <<  7)) == 0) return 1;
+    if ((value & (0xffffffff << 14)) == 0) return 2;
+    if ((value & (0xffffffff << 21)) == 0) return 3;
+    if ((value & (0xffffffff << 28)) == 0) return 4;
+    return 5;
+  }
+
+  /** Encode and write a varint. */
+  public void writeRawVarint64(long value) throws IOException {
+    while (true) {
+      if ((value & ~0x7FL) == 0) {
+        writeRawByte((int)value);
+        return;
+      } else {
+        writeRawByte(((int)value & 0x7F) | 0x80);
+        value >>>= 7;
+      }
+    }
+  }
+
+  /** Compute the number of bytes that would be needed to encode a varint. */
+  public static int computeRawVarint64Size(final long value) {
+    if ((value & (0xffffffffffffffffL <<  7)) == 0) return 1;
+    if ((value & (0xffffffffffffffffL << 14)) == 0) return 2;
+    if ((value & (0xffffffffffffffffL << 21)) == 0) return 3;
+    if ((value & (0xffffffffffffffffL << 28)) == 0) return 4;
+    if ((value & (0xffffffffffffffffL << 35)) == 0) return 5;
+    if ((value & (0xffffffffffffffffL << 42)) == 0) return 6;
+    if ((value & (0xffffffffffffffffL << 49)) == 0) return 7;
+    if ((value & (0xffffffffffffffffL << 56)) == 0) return 8;
+    if ((value & (0xffffffffffffffffL << 63)) == 0) return 9;
+    return 10;
+  }
+
+  /** Write a little-endian 32-bit integer. */
+  public void writeRawLittleEndian32(final int value) throws IOException {
+    writeRawByte((value      ) & 0xFF);
+    writeRawByte((value >>  8) & 0xFF);
+    writeRawByte((value >> 16) & 0xFF);
+    writeRawByte((value >> 24) & 0xFF);
+  }
+
+  public static final int LITTLE_ENDIAN_32_SIZE = 4;
+
+  /** Write a little-endian 64-bit integer. */
+  public void writeRawLittleEndian64(final long value) throws IOException {
+    writeRawByte((int)(value      ) & 0xFF);
+    writeRawByte((int)(value >>  8) & 0xFF);
+    writeRawByte((int)(value >> 16) & 0xFF);
+    writeRawByte((int)(value >> 24) & 0xFF);
+    writeRawByte((int)(value >> 32) & 0xFF);
+    writeRawByte((int)(value >> 40) & 0xFF);
+    writeRawByte((int)(value >> 48) & 0xFF);
+    writeRawByte((int)(value >> 56) & 0xFF);
+  }
+
+  public static final int LITTLE_ENDIAN_64_SIZE = 8;
+
+  /**
+   * Encode a ZigZag-encoded 32-bit value.  ZigZag encodes signed integers
+   * into values that can be efficiently encoded with varint.  (Otherwise,
+   * negative values must be sign-extended to 64 bits to be varint encoded,
+   * thus always taking 10 bytes on the wire.)
+   *
+   * @param n A signed 32-bit integer.
+   * @return An unsigned 32-bit integer, stored in a signed int because
+   *         Java has no explicit unsigned support.
+   */
+  public static int encodeZigZag32(final int n) {
+    // Note:  the right-shift must be arithmetic
+    return (n << 1) ^ (n >> 31);
+  }
+
+  /**
+   * Encode a ZigZag-encoded 64-bit value.  ZigZag encodes signed integers
+   * into values that can be efficiently encoded with varint.  (Otherwise,
+   * negative values must be sign-extended to 64 bits to be varint encoded,
+   * thus always taking 10 bytes on the wire.)
+   *
+   * @param n A signed 64-bit integer.
+   * @return An unsigned 64-bit integer, stored in a signed int because
+   *         Java has no explicit unsigned support.
+   */
+  public static long encodeZigZag64(final long n) {
+    // Note:  the right-shift must be arithmetic
+    return (n << 1) ^ (n >> 63);
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/Descriptors.java b/java/src/main/java/com/google/protobuf/Descriptors.java
new file mode 100644
index 0000000..0c162d5
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/Descriptors.java
@@ -0,0 +1,1871 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.DescriptorProtos.*;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.io.UnsupportedEncodingException;
+
+/**
+ * Contains a collection of classes which describe protocol message types.
+ *
+ * Every message type has a {@link Descriptor}, which lists all
+ * its fields and other information about a type.  You can get a message
+ * type's descriptor by calling {@code MessageType.getDescriptor()}, or
+ * (given a message object of the type) {@code message.getDescriptorForType()}.
+ *
+ * Descriptors are built from DescriptorProtos, as defined in
+ * {@code net/proto2/proto/descriptor.proto}.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class Descriptors {
+  /**
+   * Describes a {@code .proto} file, including everything defined within.
+   */
+  public static final class FileDescriptor {
+    /** Convert the descriptor to its protocol message representation. */
+    public FileDescriptorProto toProto() { return proto; }
+
+    /** Get the file name. */
+    public String getName() { return proto.getName(); }
+
+    /**
+     * Get the proto package name.  This is the package name given by the
+     * {@code package} statement in the {@code .proto} file, which differs
+     * from the Java package.
+     */
+    public String getPackage() { return proto.getPackage(); }
+
+    /** Get the {@code FileOptions}, defined in {@code descriptor.proto}. */
+    public FileOptions getOptions() { return proto.getOptions(); }
+
+    /** Get a list of top-level message types declared in this file. */
+    public List<Descriptor> getMessageTypes() {
+      return Collections.unmodifiableList(Arrays.asList(messageTypes));
+    }
+
+    /** Get a list of top-level enum types declared in this file. */
+    public List<EnumDescriptor> getEnumTypes() {
+      return Collections.unmodifiableList(Arrays.asList(enumTypes));
+    }
+
+    /** Get a list of top-level services declared in this file. */
+    public List<ServiceDescriptor> getServices() {
+      return Collections.unmodifiableList(Arrays.asList(services));
+    }
+
+    /** Get a list of top-level extensions declared in this file. */
+    public List<FieldDescriptor> getExtensions() {
+      return Collections.unmodifiableList(Arrays.asList(extensions));
+    }
+
+    /** Get a list of this file's dependencies (imports). */
+    public List<FileDescriptor> getDependencies() {
+      return Collections.unmodifiableList(Arrays.asList(dependencies));
+    }
+
+    /**
+     * Find a message type in the file by name.  Does not find nested types.
+     *
+     * @param name The unqualified type name to look for.
+     * @return The message type's descriptor, or {@code null} if not found.
+     */
+    public Descriptor findMessageTypeByName(String name) {
+      // Don't allow looking up nested types.  This will make optimization
+      // easier later.
+      if (name.indexOf('.') != -1) {
+        return null;
+      }
+      if (getPackage().length() > 0) {
+        name = getPackage() + '.' + name;
+      }
+      final GenericDescriptor result = pool.findSymbol(name);
+      if (result != null && result instanceof Descriptor &&
+          result.getFile() == this) {
+        return (Descriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Find an enum type in the file by name.  Does not find nested types.
+     *
+     * @param name The unqualified type name to look for.
+     * @return The enum type's descriptor, or {@code null} if not found.
+     */
+    public EnumDescriptor findEnumTypeByName(String name) {
+      // Don't allow looking up nested types.  This will make optimization
+      // easier later.
+      if (name.indexOf('.') != -1) {
+        return null;
+      }
+      if (getPackage().length() > 0) {
+        name = getPackage() + '.' + name;
+      }
+      final GenericDescriptor result = pool.findSymbol(name);
+      if (result != null && result instanceof EnumDescriptor &&
+          result.getFile() == this) {
+        return (EnumDescriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Find a service type in the file by name.
+     *
+     * @param name The unqualified type name to look for.
+     * @return The service type's descriptor, or {@code null} if not found.
+     */
+    public ServiceDescriptor findServiceByName(String name) {
+      // Don't allow looking up nested types.  This will make optimization
+      // easier later.
+      if (name.indexOf('.') != -1) {
+        return null;
+      }
+      if (getPackage().length() > 0) {
+        name = getPackage() + '.' + name;
+      }
+      final GenericDescriptor result = pool.findSymbol(name);
+      if (result != null && result instanceof ServiceDescriptor &&
+          result.getFile() == this) {
+        return (ServiceDescriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Find an extension in the file by name.  Does not find extensions nested
+     * inside message types.
+     *
+     * @param name The unqualified extension name to look for.
+     * @return The extension's descriptor, or {@code null} if not found.
+     */
+    public FieldDescriptor findExtensionByName(String name) {
+      if (name.indexOf('.') != -1) {
+        return null;
+      }
+      if (getPackage().length() > 0) {
+        name = getPackage() + '.' + name;
+      }
+      final GenericDescriptor result = pool.findSymbol(name);
+      if (result != null && result instanceof FieldDescriptor &&
+          result.getFile() == this) {
+        return (FieldDescriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Construct a {@code FileDescriptor}.
+     *
+     * @param proto The protocol message form of the FileDescriptor.
+     * @param dependencies {@code FileDescriptor}s corresponding to all of
+     *                     the file's dependencies, in the exact order listed
+     *                     in {@code proto}.
+     * @throws DescriptorValidationException {@code proto} is not a valid
+     *           descriptor.  This can occur for a number of reasons, e.g.
+     *           because a field has an undefined type or because two messages
+     *           were defined with the same name.
+     */
+    public static FileDescriptor buildFrom(final FileDescriptorProto proto,
+                                           final FileDescriptor[] dependencies)
+                                    throws DescriptorValidationException {
+      // Building decsriptors involves two steps:  translating and linking.
+      // In the translation step (implemented by FileDescriptor's
+      // constructor), we build an object tree mirroring the
+      // FileDescriptorProto's tree and put all of the descriptors into the
+      // DescriptorPool's lookup tables.  In the linking step, we look up all
+      // type references in the DescriptorPool, so that, for example, a
+      // FieldDescriptor for an embedded message contains a pointer directly
+      // to the Descriptor for that message's type.  We also detect undefined
+      // types in the linking step.
+      final DescriptorPool pool = new DescriptorPool(dependencies);
+      final FileDescriptor result =
+          new FileDescriptor(proto, dependencies, pool);
+
+      if (dependencies.length != proto.getDependencyCount()) {
+        throw new DescriptorValidationException(result,
+          "Dependencies passed to FileDescriptor.buildFrom() don't match " +
+          "those listed in the FileDescriptorProto.");
+      }
+      for (int i = 0; i < proto.getDependencyCount(); i++) {
+        if (!dependencies[i].getName().equals(proto.getDependency(i))) {
+          throw new DescriptorValidationException(result,
+            "Dependencies passed to FileDescriptor.buildFrom() don't match " +
+            "those listed in the FileDescriptorProto.");
+        }
+      }
+
+      result.crossLink();
+      return result;
+    }
+
+    /**
+     * This method is to be called by generated code only.  It is equivalent
+     * to {@code buildFrom} except that the {@code FileDescriptorProto} is
+     * encoded in protocol buffer wire format.
+     */
+    public static void internalBuildGeneratedFileFrom(
+        final String[] descriptorDataParts,
+        final FileDescriptor[] dependencies,
+        final InternalDescriptorAssigner descriptorAssigner) {
+      // Hack:  We can't embed a raw byte array inside generated Java code
+      //   (at least, not efficiently), but we can embed Strings.  So, the
+      //   protocol compiler embeds the FileDescriptorProto as a giant
+      //   string literal which is passed to this function to construct the
+      //   file's FileDescriptor.  The string literal contains only 8-bit
+      //   characters, each one representing a byte of the FileDescriptorProto's
+      //   serialized form.  So, if we convert it to bytes in ISO-8859-1, we
+      //   should get the original bytes that we want.
+
+      // descriptorData may contain multiple strings in order to get around the
+      // Java 64k string literal limit.
+      StringBuilder descriptorData = new StringBuilder();
+      for (String part : descriptorDataParts) {
+        descriptorData.append(part);
+      }
+
+      final byte[] descriptorBytes;
+      try {
+        descriptorBytes = descriptorData.toString().getBytes("ISO-8859-1");
+      } catch (UnsupportedEncodingException e) {
+        throw new RuntimeException(
+          "Standard encoding ISO-8859-1 not supported by JVM.", e);
+      }
+
+      FileDescriptorProto proto;
+      try {
+        proto = FileDescriptorProto.parseFrom(descriptorBytes);
+      } catch (InvalidProtocolBufferException e) {
+        throw new IllegalArgumentException(
+          "Failed to parse protocol buffer descriptor for generated code.", e);
+      }
+
+      final FileDescriptor result;
+      try {
+        result = buildFrom(proto, dependencies);
+      } catch (DescriptorValidationException e) {
+        throw new IllegalArgumentException(
+          "Invalid embedded descriptor for \"" + proto.getName() + "\".", e);
+      }
+
+      final ExtensionRegistry registry =
+          descriptorAssigner.assignDescriptors(result);
+
+      if (registry != null) {
+        // We must re-parse the proto using the registry.
+        try {
+          proto = FileDescriptorProto.parseFrom(descriptorBytes, registry);
+        } catch (InvalidProtocolBufferException e) {
+          throw new IllegalArgumentException(
+            "Failed to parse protocol buffer descriptor for generated code.",
+            e);
+        }
+
+        result.setProto(proto);
+      }
+    }
+
+    /**
+     * This class should be used by generated code only.  When calling
+     * {@link FileDescriptor#internalBuildGeneratedFileFrom}, the caller
+     * provides a callback implementing this interface.  The callback is called
+     * after the FileDescriptor has been constructed, in order to assign all
+     * the global variales defined in the generated code which point at parts
+     * of the FileDescriptor.  The callback returns an ExtensionRegistry which
+     * contains any extensions which might be used in the descriptor -- that
+     * is, extensions of the various "Options" messages defined in
+     * descriptor.proto.  The callback may also return null to indicate that
+     * no extensions are used in the decsriptor.
+     */
+    public interface InternalDescriptorAssigner {
+      ExtensionRegistry assignDescriptors(FileDescriptor root);
+    }
+
+    private FileDescriptorProto proto;
+    private final Descriptor[] messageTypes;
+    private final EnumDescriptor[] enumTypes;
+    private final ServiceDescriptor[] services;
+    private final FieldDescriptor[] extensions;
+    private final FileDescriptor[] dependencies;
+    private final DescriptorPool pool;
+
+    private FileDescriptor(final FileDescriptorProto proto,
+                           final FileDescriptor[] dependencies,
+                           final DescriptorPool pool)
+                    throws DescriptorValidationException {
+      this.pool = pool;
+      this.proto = proto;
+      this.dependencies = dependencies.clone();
+
+      pool.addPackage(getPackage(), this);
+
+      messageTypes = new Descriptor[proto.getMessageTypeCount()];
+      for (int i = 0; i < proto.getMessageTypeCount(); i++) {
+        messageTypes[i] =
+          new Descriptor(proto.getMessageType(i), this, null, i);
+      }
+
+      enumTypes = new EnumDescriptor[proto.getEnumTypeCount()];
+      for (int i = 0; i < proto.getEnumTypeCount(); i++) {
+        enumTypes[i] = new EnumDescriptor(proto.getEnumType(i), this, null, i);
+      }
+
+      services = new ServiceDescriptor[proto.getServiceCount()];
+      for (int i = 0; i < proto.getServiceCount(); i++) {
+        services[i] = new ServiceDescriptor(proto.getService(i), this, i);
+      }
+
+      extensions = new FieldDescriptor[proto.getExtensionCount()];
+      for (int i = 0; i < proto.getExtensionCount(); i++) {
+        extensions[i] = new FieldDescriptor(
+          proto.getExtension(i), this, null, i, true);
+      }
+    }
+
+    /** Look up and cross-link all field types, etc. */
+    private void crossLink() throws DescriptorValidationException {
+      for (final Descriptor messageType : messageTypes) {
+        messageType.crossLink();
+      }
+
+      for (final ServiceDescriptor service : services) {
+        service.crossLink();
+      }
+
+      for (final FieldDescriptor extension : extensions) {
+        extension.crossLink();
+      }
+    }
+
+    /**
+     * Replace our {@link FileDescriptorProto} with the given one, which is
+     * identical except that it might contain extensions that weren't present
+     * in the original.  This method is needed for bootstrapping when a file
+     * defines custom options.  The options may be defined in the file itself,
+     * so we can't actually parse them until we've constructed the descriptors,
+     * but to construct the decsriptors we have to have parsed the descriptor
+     * protos.  So, we have to parse the descriptor protos a second time after
+     * constructing the descriptors.
+     */
+    private void setProto(final FileDescriptorProto proto) {
+      this.proto = proto;
+
+      for (int i = 0; i < messageTypes.length; i++) {
+        messageTypes[i].setProto(proto.getMessageType(i));
+      }
+
+      for (int i = 0; i < enumTypes.length; i++) {
+        enumTypes[i].setProto(proto.getEnumType(i));
+      }
+
+      for (int i = 0; i < services.length; i++) {
+        services[i].setProto(proto.getService(i));
+      }
+
+      for (int i = 0; i < extensions.length; i++) {
+        extensions[i].setProto(proto.getExtension(i));
+      }
+    }
+  }
+
+  // =================================================================
+
+  /** Describes a message type. */
+  public static final class Descriptor implements GenericDescriptor {
+    /**
+     * Get the index of this descriptor within its parent.  In other words,
+     * given a {@link FileDescriptor} {@code file}, the following is true:
+     * <pre>
+     *   for all i in [0, file.getMessageTypeCount()):
+     *     file.getMessageType(i).getIndex() == i
+     * </pre>
+     * Similarly, for a {@link Descriptor} {@code messageType}:
+     * <pre>
+     *   for all i in [0, messageType.getNestedTypeCount()):
+     *     messageType.getNestedType(i).getIndex() == i
+     * </pre>
+     */
+    public int getIndex() { return index; }
+
+    /** Convert the descriptor to its protocol message representation. */
+    public DescriptorProto toProto() { return proto; }
+
+    /** Get the type's unqualified name. */
+    public String getName() { return proto.getName(); }
+
+    /**
+     * Get the type's fully-qualified name, within the proto language's
+     * namespace.  This differs from the Java name.  For example, given this
+     * {@code .proto}:
+     * <pre>
+     *   package foo.bar;
+     *   option java_package = "com.example.protos"
+     *   message Baz {}
+     * </pre>
+     * {@code Baz}'s full name is "foo.bar.Baz".
+     */
+    public String getFullName() { return fullName; }
+
+    /** Get the {@link FileDescriptor} containing this descriptor. */
+    public FileDescriptor getFile() { return file; }
+
+    /** If this is a nested type, get the outer descriptor, otherwise null. */
+    public Descriptor getContainingType() { return containingType; }
+
+    /** Get the {@code MessageOptions}, defined in {@code descriptor.proto}. */
+    public MessageOptions getOptions() { return proto.getOptions(); }
+
+    /** Get a list of this message type's fields. */
+    public List<FieldDescriptor> getFields() {
+      return Collections.unmodifiableList(Arrays.asList(fields));
+    }
+
+    /** Get a list of this message type's extensions. */
+    public List<FieldDescriptor> getExtensions() {
+      return Collections.unmodifiableList(Arrays.asList(extensions));
+    }
+
+    /** Get a list of message types nested within this one. */
+    public List<Descriptor> getNestedTypes() {
+      return Collections.unmodifiableList(Arrays.asList(nestedTypes));
+    }
+
+    /** Get a list of enum types nested within this one. */
+    public List<EnumDescriptor> getEnumTypes() {
+      return Collections.unmodifiableList(Arrays.asList(enumTypes));
+    }
+
+    /** Determines if the given field number is an extension. */
+    public boolean isExtensionNumber(final int number) {
+      for (final DescriptorProto.ExtensionRange range :
+          proto.getExtensionRangeList()) {
+        if (range.getStart() <= number && number < range.getEnd()) {
+          return true;
+        }
+      }
+      return false;
+    }
+
+    /**
+     * Finds a field by name.
+     * @param name The unqualified name of the field (e.g. "foo").
+     * @return The field's descriptor, or {@code null} if not found.
+     */
+    public FieldDescriptor findFieldByName(final String name) {
+      final GenericDescriptor result =
+          file.pool.findSymbol(fullName + '.' + name);
+      if (result != null && result instanceof FieldDescriptor) {
+        return (FieldDescriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Finds a field by field number.
+     * @param number The field number within this message type.
+     * @return The field's descriptor, or {@code null} if not found.
+     */
+    public FieldDescriptor findFieldByNumber(final int number) {
+      return file.pool.fieldsByNumber.get(
+        new DescriptorPool.DescriptorIntPair(this, number));
+    }
+
+    /**
+     * Finds a nested message type by name.
+     * @param name The unqualified name of the nested type (e.g. "Foo").
+     * @return The types's descriptor, or {@code null} if not found.
+     */
+    public Descriptor findNestedTypeByName(final String name) {
+      final GenericDescriptor result =
+          file.pool.findSymbol(fullName + '.' + name);
+      if (result != null && result instanceof Descriptor) {
+        return (Descriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Finds a nested enum type by name.
+     * @param name The unqualified name of the nested type (e.g. "Foo").
+     * @return The types's descriptor, or {@code null} if not found.
+     */
+    public EnumDescriptor findEnumTypeByName(final String name) {
+      final GenericDescriptor result =
+          file.pool.findSymbol(fullName + '.' + name);
+      if (result != null && result instanceof EnumDescriptor) {
+        return (EnumDescriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    private final int index;
+    private DescriptorProto proto;
+    private final String fullName;
+    private final FileDescriptor file;
+    private final Descriptor containingType;
+    private final Descriptor[] nestedTypes;
+    private final EnumDescriptor[] enumTypes;
+    private final FieldDescriptor[] fields;
+    private final FieldDescriptor[] extensions;
+
+    private Descriptor(final DescriptorProto proto,
+                       final FileDescriptor file,
+                       final Descriptor parent,
+                       final int index)
+                throws DescriptorValidationException {
+      this.index = index;
+      this.proto = proto;
+      fullName = computeFullName(file, parent, proto.getName());
+      this.file = file;
+      containingType = parent;
+
+      nestedTypes = new Descriptor[proto.getNestedTypeCount()];
+      for (int i = 0; i < proto.getNestedTypeCount(); i++) {
+        nestedTypes[i] = new Descriptor(
+          proto.getNestedType(i), file, this, i);
+      }
+
+      enumTypes = new EnumDescriptor[proto.getEnumTypeCount()];
+      for (int i = 0; i < proto.getEnumTypeCount(); i++) {
+        enumTypes[i] = new EnumDescriptor(
+          proto.getEnumType(i), file, this, i);
+      }
+
+      fields = new FieldDescriptor[proto.getFieldCount()];
+      for (int i = 0; i < proto.getFieldCount(); i++) {
+        fields[i] = new FieldDescriptor(
+          proto.getField(i), file, this, i, false);
+      }
+
+      extensions = new FieldDescriptor[proto.getExtensionCount()];
+      for (int i = 0; i < proto.getExtensionCount(); i++) {
+        extensions[i] = new FieldDescriptor(
+          proto.getExtension(i), file, this, i, true);
+      }
+
+      file.pool.addSymbol(this);
+    }
+
+    /** Look up and cross-link all field types, etc. */
+    private void crossLink() throws DescriptorValidationException {
+      for (final Descriptor nestedType : nestedTypes) {
+        nestedType.crossLink();
+      }
+
+      for (final FieldDescriptor field : fields) {
+        field.crossLink();
+      }
+
+      for (final FieldDescriptor extension : extensions) {
+        extension.crossLink();
+      }
+    }
+
+    /** See {@link FileDescriptor#setProto}. */
+    private void setProto(final DescriptorProto proto) {
+      this.proto = proto;
+
+      for (int i = 0; i < nestedTypes.length; i++) {
+        nestedTypes[i].setProto(proto.getNestedType(i));
+      }
+
+      for (int i = 0; i < enumTypes.length; i++) {
+        enumTypes[i].setProto(proto.getEnumType(i));
+      }
+
+      for (int i = 0; i < fields.length; i++) {
+        fields[i].setProto(proto.getField(i));
+      }
+
+      for (int i = 0; i < extensions.length; i++) {
+        extensions[i].setProto(proto.getExtension(i));
+      }
+    }
+  }
+
+  // =================================================================
+
+  /** Describes a field of a message type. */
+  public static final class FieldDescriptor
+      implements GenericDescriptor, Comparable<FieldDescriptor>,
+                 FieldSet.FieldDescriptorLite<FieldDescriptor> {
+    /**
+     * Get the index of this descriptor within its parent.
+     * @see Descriptor#getIndex()
+     */
+    public int getIndex() { return index; }
+
+    /** Convert the descriptor to its protocol message representation. */
+    public FieldDescriptorProto toProto() { return proto; }
+
+    /** Get the field's unqualified name. */
+    public String getName() { return proto.getName(); }
+
+    /** Get the field's number. */
+    public int getNumber() { return proto.getNumber(); }
+
+    /**
+     * Get the field's fully-qualified name.
+     * @see Descriptor#getFullName()
+     */
+    public String getFullName() { return fullName; }
+
+    /**
+     * Get the field's java type.  This is just for convenience.  Every
+     * {@code FieldDescriptorProto.Type} maps to exactly one Java type.
+     */
+    public JavaType getJavaType() { return type.getJavaType(); }
+
+    /** For internal use only. */
+    public WireFormat.JavaType getLiteJavaType() {
+      return getLiteType().getJavaType();
+    }
+
+    /** Get the {@code FileDescriptor} containing this descriptor. */
+    public FileDescriptor getFile() { return file; }
+
+    /** Get the field's declared type. */
+    public Type getType() { return type; }
+
+    /** For internal use only. */
+    public WireFormat.FieldType getLiteType() {
+      return table[type.ordinal()];
+    }
+    // I'm pretty sure values() constructs a new array every time, since there
+    // is nothing stopping the caller from mutating the array.  Therefore we
+    // make a static copy here.
+    private static final WireFormat.FieldType[] table =
+        WireFormat.FieldType.values();
+
+    /** Is this field declared required? */
+    public boolean isRequired() {
+      return proto.getLabel() == FieldDescriptorProto.Label.LABEL_REQUIRED;
+    }
+
+    /** Is this field declared optional? */
+    public boolean isOptional() {
+      return proto.getLabel() == FieldDescriptorProto.Label.LABEL_OPTIONAL;
+    }
+
+    /** Is this field declared repeated? */
+    public boolean isRepeated() {
+      return proto.getLabel() == FieldDescriptorProto.Label.LABEL_REPEATED;
+    }
+
+    /** Does this field have the {@code [packed = true]} option? */
+    public boolean isPacked() {
+      return getOptions().getPacked();
+    }
+
+    /** Returns true if the field had an explicitly-defined default value. */
+    public boolean hasDefaultValue() { return proto.hasDefaultValue(); }
+
+    /**
+     * Returns the field's default value.  Valid for all types except for
+     * messages and groups.  For all other types, the object returned is of
+     * the same class that would returned by Message.getField(this).
+     */
+    public Object getDefaultValue() {
+      if (getJavaType() == JavaType.MESSAGE) {
+        throw new UnsupportedOperationException(
+          "FieldDescriptor.getDefaultValue() called on an embedded message " +
+          "field.");
+      }
+      return defaultValue;
+    }
+
+    /** Get the {@code FieldOptions}, defined in {@code descriptor.proto}. */
+    public FieldOptions getOptions() { return proto.getOptions(); }
+
+    /** Is this field an extension? */
+    public boolean isExtension() { return proto.hasExtendee(); }
+
+    /**
+     * Get the field's containing type. For extensions, this is the type being
+     * extended, not the location where the extension was defined.  See
+     * {@link #getExtensionScope()}.
+     */
+    public Descriptor getContainingType() { return containingType; }
+
+    /**
+     * For extensions defined nested within message types, gets the outer
+     * type.  Not valid for non-extension fields.  For example, consider
+     * this {@code .proto} file:
+     * <pre>
+     *   message Foo {
+     *     extensions 1000 to max;
+     *   }
+     *   extend Foo {
+     *     optional int32 baz = 1234;
+     *   }
+     *   message Bar {
+     *     extend Foo {
+     *       optional int32 qux = 4321;
+     *     }
+     *   }
+     * </pre>
+     * Both {@code baz}'s and {@code qux}'s containing type is {@code Foo}.
+     * However, {@code baz}'s extension scope is {@code null} while
+     * {@code qux}'s extension scope is {@code Bar}.
+     */
+    public Descriptor getExtensionScope() {
+      if (!isExtension()) {
+        throw new UnsupportedOperationException(
+          "This field is not an extension.");
+      }
+      return extensionScope;
+    }
+
+    /** For embedded message and group fields, gets the field's type. */
+    public Descriptor getMessageType() {
+      if (getJavaType() != JavaType.MESSAGE) {
+        throw new UnsupportedOperationException(
+          "This field is not of message type.");
+      }
+      return messageType;
+    }
+
+    /** For enum fields, gets the field's type. */
+    public EnumDescriptor getEnumType() {
+      if (getJavaType() != JavaType.ENUM) {
+        throw new UnsupportedOperationException(
+          "This field is not of enum type.");
+      }
+      return enumType;
+    }
+
+    /**
+     * Compare with another {@code FieldDescriptor}.  This orders fields in
+     * "canonical" order, which simply means ascending order by field number.
+     * {@code other} must be a field of the same type -- i.e.
+     * {@code getContainingType()} must return the same {@code Descriptor} for
+     * both fields.
+     *
+     * @return negative, zero, or positive if {@code this} is less than,
+     *         equal to, or greater than {@code other}, respectively.
+     */
+    public int compareTo(final FieldDescriptor other) {
+      if (other.containingType != containingType) {
+        throw new IllegalArgumentException(
+          "FieldDescriptors can only be compared to other FieldDescriptors " +
+          "for fields of the same message type.");
+      }
+      return getNumber() - other.getNumber();
+    }
+
+    private final int index;
+
+    private FieldDescriptorProto proto;
+    private final String fullName;
+    private final FileDescriptor file;
+    private final Descriptor extensionScope;
+
+    // Possibly initialized during cross-linking.
+    private Type type;
+    private Descriptor containingType;
+    private Descriptor messageType;
+    private EnumDescriptor enumType;
+    private Object defaultValue;
+
+    public enum Type {
+      DOUBLE  (FieldDescriptorProto.Type.TYPE_DOUBLE  , JavaType.DOUBLE     ),
+      FLOAT   (FieldDescriptorProto.Type.TYPE_FLOAT   , JavaType.FLOAT      ),
+      INT64   (FieldDescriptorProto.Type.TYPE_INT64   , JavaType.LONG       ),
+      UINT64  (FieldDescriptorProto.Type.TYPE_UINT64  , JavaType.LONG       ),
+      INT32   (FieldDescriptorProto.Type.TYPE_INT32   , JavaType.INT        ),
+      FIXED64 (FieldDescriptorProto.Type.TYPE_FIXED64 , JavaType.LONG       ),
+      FIXED32 (FieldDescriptorProto.Type.TYPE_FIXED32 , JavaType.INT        ),
+      BOOL    (FieldDescriptorProto.Type.TYPE_BOOL    , JavaType.BOOLEAN    ),
+      STRING  (FieldDescriptorProto.Type.TYPE_STRING  , JavaType.STRING     ),
+      GROUP   (FieldDescriptorProto.Type.TYPE_GROUP   , JavaType.MESSAGE    ),
+      MESSAGE (FieldDescriptorProto.Type.TYPE_MESSAGE , JavaType.MESSAGE    ),
+      BYTES   (FieldDescriptorProto.Type.TYPE_BYTES   , JavaType.BYTE_STRING),
+      UINT32  (FieldDescriptorProto.Type.TYPE_UINT32  , JavaType.INT        ),
+      ENUM    (FieldDescriptorProto.Type.TYPE_ENUM    , JavaType.ENUM       ),
+      SFIXED32(FieldDescriptorProto.Type.TYPE_SFIXED32, JavaType.INT        ),
+      SFIXED64(FieldDescriptorProto.Type.TYPE_SFIXED64, JavaType.LONG       ),
+      SINT32  (FieldDescriptorProto.Type.TYPE_SINT32  , JavaType.INT        ),
+      SINT64  (FieldDescriptorProto.Type.TYPE_SINT64  , JavaType.LONG       );
+
+      Type(final FieldDescriptorProto.Type proto, final JavaType javaType) {
+        this.proto = proto;
+        this.javaType = javaType;
+
+        if (ordinal() != proto.getNumber() - 1) {
+          throw new RuntimeException(
+            "descriptor.proto changed but Desrciptors.java wasn't updated.");
+        }
+      }
+
+      private FieldDescriptorProto.Type proto;
+      private JavaType javaType;
+
+      public FieldDescriptorProto.Type toProto() { return proto; }
+      public JavaType getJavaType() { return javaType; }
+
+      public static Type valueOf(final FieldDescriptorProto.Type type) {
+        return values()[type.getNumber() - 1];
+      }
+    }
+
+    static {
+      // Refuse to init if someone added a new declared type.
+      if (Type.values().length != FieldDescriptorProto.Type.values().length) {
+        throw new RuntimeException(
+          "descriptor.proto has a new declared type but Desrciptors.java " +
+          "wasn't updated.");
+      }
+    }
+
+    public enum JavaType {
+      INT(0),
+      LONG(0L),
+      FLOAT(0F),
+      DOUBLE(0D),
+      BOOLEAN(false),
+      STRING(""),
+      BYTE_STRING(ByteString.EMPTY),
+      ENUM(null),
+      MESSAGE(null);
+
+      JavaType(final Object defaultDefault) {
+        this.defaultDefault = defaultDefault;
+      }
+
+      /**
+       * The default default value for fields of this type, if it's a primitive
+       * type.  This is meant for use inside this file only, hence is private.
+       */
+      private final Object defaultDefault;
+    }
+
+    private FieldDescriptor(final FieldDescriptorProto proto,
+                            final FileDescriptor file,
+                            final Descriptor parent,
+                            final int index,
+                            final boolean isExtension)
+                     throws DescriptorValidationException {
+      this.index = index;
+      this.proto = proto;
+      fullName = computeFullName(file, parent, proto.getName());
+      this.file = file;
+
+      if (proto.hasType()) {
+        type = Type.valueOf(proto.getType());
+      }
+
+      if (getNumber() <= 0) {
+        throw new DescriptorValidationException(this,
+          "Field numbers must be positive integers.");
+      }
+
+      // Only repeated primitive fields may be packed.
+      if (proto.getOptions().getPacked()) {
+        if (proto.getLabel() != FieldDescriptorProto.Label.LABEL_REPEATED ||
+            proto.getType() == FieldDescriptorProto.Type.TYPE_STRING ||
+            proto.getType() == FieldDescriptorProto.Type.TYPE_GROUP ||
+            proto.getType() == FieldDescriptorProto.Type.TYPE_MESSAGE ||
+            proto.getType() == FieldDescriptorProto.Type.TYPE_BYTES) {
+          throw new DescriptorValidationException(this,
+            "[packed = true] can only be specified for repeated primitive " +
+            "fields.");
+        }
+      }
+
+      if (isExtension) {
+        if (!proto.hasExtendee()) {
+          throw new DescriptorValidationException(this,
+            "FieldDescriptorProto.extendee not set for extension field.");
+        }
+        containingType = null;  // Will be filled in when cross-linking
+        if (parent != null) {
+          extensionScope = parent;
+        } else {
+          extensionScope = null;
+        }
+      } else {
+        if (proto.hasExtendee()) {
+          throw new DescriptorValidationException(this,
+            "FieldDescriptorProto.extendee set for non-extension field.");
+        }
+        containingType = parent;
+        extensionScope = null;
+      }
+
+      file.pool.addSymbol(this);
+    }
+
+    /** Look up and cross-link all field types, etc. */
+    private void crossLink() throws DescriptorValidationException {
+      if (proto.hasExtendee()) {
+        final GenericDescriptor extendee =
+          file.pool.lookupSymbol(proto.getExtendee(), this);
+        if (!(extendee instanceof Descriptor)) {
+          throw new DescriptorValidationException(this,
+              '\"' + proto.getExtendee() + "\" is not a message type.");
+        }
+        containingType = (Descriptor)extendee;
+
+        if (!getContainingType().isExtensionNumber(getNumber())) {
+          throw new DescriptorValidationException(this,
+              '\"' + getContainingType().getFullName() +
+              "\" does not declare " + getNumber() +
+              " as an extension number.");
+        }
+      }
+
+      if (proto.hasTypeName()) {
+        final GenericDescriptor typeDescriptor =
+          file.pool.lookupSymbol(proto.getTypeName(), this);
+
+        if (!proto.hasType()) {
+          // Choose field type based on symbol.
+          if (typeDescriptor instanceof Descriptor) {
+            type = Type.MESSAGE;
+          } else if (typeDescriptor instanceof EnumDescriptor) {
+            type = Type.ENUM;
+          } else {
+            throw new DescriptorValidationException(this,
+                '\"' + proto.getTypeName() + "\" is not a type.");
+          }
+        }
+
+        if (getJavaType() == JavaType.MESSAGE) {
+          if (!(typeDescriptor instanceof Descriptor)) {
+            throw new DescriptorValidationException(this,
+                '\"' + proto.getTypeName() + "\" is not a message type.");
+          }
+          messageType = (Descriptor)typeDescriptor;
+
+          if (proto.hasDefaultValue()) {
+            throw new DescriptorValidationException(this,
+              "Messages can't have default values.");
+          }
+        } else if (getJavaType() == JavaType.ENUM) {
+          if (!(typeDescriptor instanceof EnumDescriptor)) {
+            throw new DescriptorValidationException(this,
+                '\"' + proto.getTypeName() + "\" is not an enum type.");
+          }
+          enumType = (EnumDescriptor)typeDescriptor;
+        } else {
+          throw new DescriptorValidationException(this,
+            "Field with primitive type has type_name.");
+        }
+      } else {
+        if (getJavaType() == JavaType.MESSAGE ||
+            getJavaType() == JavaType.ENUM) {
+          throw new DescriptorValidationException(this,
+            "Field with message or enum type missing type_name.");
+        }
+      }
+
+      // We don't attempt to parse the default value until here because for
+      // enums we need the enum type's descriptor.
+      if (proto.hasDefaultValue()) {
+        if (isRepeated()) {
+          throw new DescriptorValidationException(this,
+            "Repeated fields cannot have default values.");
+        }
+
+        try {
+          switch (getType()) {
+            case INT32:
+            case SINT32:
+            case SFIXED32:
+              defaultValue = TextFormat.parseInt32(proto.getDefaultValue());
+              break;
+            case UINT32:
+            case FIXED32:
+              defaultValue = TextFormat.parseUInt32(proto.getDefaultValue());
+              break;
+            case INT64:
+            case SINT64:
+            case SFIXED64:
+              defaultValue = TextFormat.parseInt64(proto.getDefaultValue());
+              break;
+            case UINT64:
+            case FIXED64:
+              defaultValue = TextFormat.parseUInt64(proto.getDefaultValue());
+              break;
+            case FLOAT:
+              defaultValue = Float.valueOf(proto.getDefaultValue());
+              break;
+            case DOUBLE:
+              defaultValue = Double.valueOf(proto.getDefaultValue());
+              break;
+            case BOOL:
+              defaultValue = Boolean.valueOf(proto.getDefaultValue());
+              break;
+            case STRING:
+              defaultValue = proto.getDefaultValue();
+              break;
+            case BYTES:
+              try {
+                defaultValue =
+                  TextFormat.unescapeBytes(proto.getDefaultValue());
+              } catch (TextFormat.InvalidEscapeSequenceException e) {
+                throw new DescriptorValidationException(this,
+                  "Couldn't parse default value: " + e.getMessage(), e);
+              }
+              break;
+            case ENUM:
+              defaultValue = enumType.findValueByName(proto.getDefaultValue());
+              if (defaultValue == null) {
+                throw new DescriptorValidationException(this,
+                  "Unknown enum default value: \"" +
+                  proto.getDefaultValue() + '\"');
+              }
+              break;
+            case MESSAGE:
+            case GROUP:
+              throw new DescriptorValidationException(this,
+                "Message type had default value.");
+          }
+        } catch (NumberFormatException e) {
+          final DescriptorValidationException validationException =
+            new DescriptorValidationException(this,
+              "Could not parse default value: \"" +
+              proto.getDefaultValue() + '\"');
+          validationException.initCause(e);
+          throw validationException;
+        }
+      } else {
+        // Determine the default default for this field.
+        if (isRepeated()) {
+          defaultValue = Collections.emptyList();
+        } else {
+          switch (getJavaType()) {
+            case ENUM:
+              // We guarantee elsewhere that an enum type always has at least
+              // one possible value.
+              defaultValue = enumType.getValues().get(0);
+              break;
+            case MESSAGE:
+              defaultValue = null;
+              break;
+            default:
+              defaultValue = getJavaType().defaultDefault;
+              break;
+          }
+        }
+      }
+
+      if (!isExtension()) {
+        file.pool.addFieldByNumber(this);
+      }
+
+      if (containingType != null &&
+          containingType.getOptions().getMessageSetWireFormat()) {
+        if (isExtension()) {
+          if (!isOptional() || getType() != Type.MESSAGE) {
+            throw new DescriptorValidationException(this,
+              "Extensions of MessageSets must be optional messages.");
+          }
+        } else {
+          throw new DescriptorValidationException(this,
+            "MessageSets cannot have fields, only extensions.");
+        }
+      }
+    }
+
+    /** See {@link FileDescriptor#setProto}. */
+    private void setProto(final FieldDescriptorProto proto) {
+      this.proto = proto;
+    }
+
+    /**
+     * For internal use only.  This is to satisfy the FieldDescriptorLite
+     * interface.
+     */
+    public MessageLite.Builder internalMergeFrom(
+        MessageLite.Builder to, MessageLite from) {
+      // FieldDescriptors are only used with non-lite messages so we can just
+      // down-cast and call mergeFrom directly.
+      return ((Message.Builder) to).mergeFrom((Message) from);
+    }
+  }
+
+  // =================================================================
+
+  /** Describes an enum type. */
+  public static final class EnumDescriptor
+      implements GenericDescriptor, Internal.EnumLiteMap<EnumValueDescriptor> {
+    /**
+     * Get the index of this descriptor within its parent.
+     * @see Descriptor#getIndex()
+     */
+    public int getIndex() { return index; }
+
+    /** Convert the descriptor to its protocol message representation. */
+    public EnumDescriptorProto toProto() { return proto; }
+
+    /** Get the type's unqualified name. */
+    public String getName() { return proto.getName(); }
+
+    /**
+     * Get the type's fully-qualified name.
+     * @see Descriptor#getFullName()
+     */
+    public String getFullName() { return fullName; }
+
+    /** Get the {@link FileDescriptor} containing this descriptor. */
+    public FileDescriptor getFile() { return file; }
+
+    /** If this is a nested type, get the outer descriptor, otherwise null. */
+    public Descriptor getContainingType() { return containingType; }
+
+    /** Get the {@code EnumOptions}, defined in {@code descriptor.proto}. */
+    public EnumOptions getOptions() { return proto.getOptions(); }
+
+    /** Get a list of defined values for this enum. */
+    public List<EnumValueDescriptor> getValues() {
+      return Collections.unmodifiableList(Arrays.asList(values));
+    }
+
+    /**
+     * Find an enum value by name.
+     * @param name The unqualified name of the value (e.g. "FOO").
+     * @return the value's decsriptor, or {@code null} if not found.
+     */
+    public EnumValueDescriptor findValueByName(final String name) {
+      final GenericDescriptor result =
+          file.pool.findSymbol(fullName + '.' + name);
+      if (result != null && result instanceof EnumValueDescriptor) {
+        return (EnumValueDescriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    /**
+     * Find an enum value by number.  If multiple enum values have the same
+     * number, this returns the first defined value with that number.
+     * @param number The value's number.
+     * @return the value's decsriptor, or {@code null} if not found.
+     */
+    public EnumValueDescriptor findValueByNumber(final int number) {
+      return file.pool.enumValuesByNumber.get(
+        new DescriptorPool.DescriptorIntPair(this, number));
+    }
+
+    private final int index;
+    private EnumDescriptorProto proto;
+    private final String fullName;
+    private final FileDescriptor file;
+    private final Descriptor containingType;
+    private EnumValueDescriptor[] values;
+
+    private EnumDescriptor(final EnumDescriptorProto proto,
+                           final FileDescriptor file,
+                           final Descriptor parent,
+                           final int index)
+                    throws DescriptorValidationException {
+      this.index = index;
+      this.proto = proto;
+      fullName = computeFullName(file, parent, proto.getName());
+      this.file = file;
+      containingType = parent;
+
+      if (proto.getValueCount() == 0) {
+        // We cannot allow enums with no values because this would mean there
+        // would be no valid default value for fields of this type.
+        throw new DescriptorValidationException(this,
+          "Enums must contain at least one value.");
+      }
+
+      values = new EnumValueDescriptor[proto.getValueCount()];
+      for (int i = 0; i < proto.getValueCount(); i++) {
+        values[i] = new EnumValueDescriptor(
+          proto.getValue(i), file, this, i);
+      }
+
+      file.pool.addSymbol(this);
+    }
+
+    /** See {@link FileDescriptor#setProto}. */
+    private void setProto(final EnumDescriptorProto proto) {
+      this.proto = proto;
+
+      for (int i = 0; i < values.length; i++) {
+        values[i].setProto(proto.getValue(i));
+      }
+    }
+  }
+
+  // =================================================================
+
+  /**
+   * Describes one value within an enum type.  Note that multiple defined
+   * values may have the same number.  In generated Java code, all values
+   * with the same number after the first become aliases of the first.
+   * However, they still have independent EnumValueDescriptors.
+   */
+  public static final class EnumValueDescriptor
+      implements GenericDescriptor, Internal.EnumLite {
+    /**
+     * Get the index of this descriptor within its parent.
+     * @see Descriptor#getIndex()
+     */
+    public int getIndex() { return index; }
+
+    /** Convert the descriptor to its protocol message representation. */
+    public EnumValueDescriptorProto toProto() { return proto; }
+
+    /** Get the value's unqualified name. */
+    public String getName() { return proto.getName(); }
+
+    /** Get the value's number. */
+    public int getNumber() { return proto.getNumber(); }
+
+    /**
+     * Get the value's fully-qualified name.
+     * @see Descriptor#getFullName()
+     */
+    public String getFullName() { return fullName; }
+
+    /** Get the {@link FileDescriptor} containing this descriptor. */
+    public FileDescriptor getFile() { return file; }
+
+    /** Get the value's enum type. */
+    public EnumDescriptor getType() { return type; }
+
+    /**
+     * Get the {@code EnumValueOptions}, defined in {@code descriptor.proto}.
+     */
+    public EnumValueOptions getOptions() { return proto.getOptions(); }
+
+    private final int index;
+    private EnumValueDescriptorProto proto;
+    private final String fullName;
+    private final FileDescriptor file;
+    private final EnumDescriptor type;
+
+    private EnumValueDescriptor(final EnumValueDescriptorProto proto,
+                                final FileDescriptor file,
+                                final EnumDescriptor parent,
+                                final int index)
+                         throws DescriptorValidationException {
+      this.index = index;
+      this.proto = proto;
+      this.file = file;
+      type = parent;
+
+      fullName = parent.getFullName() + '.' + proto.getName();
+
+      file.pool.addSymbol(this);
+      file.pool.addEnumValueByNumber(this);
+    }
+
+    /** See {@link FileDescriptor#setProto}. */
+    private void setProto(final EnumValueDescriptorProto proto) {
+      this.proto = proto;
+    }
+  }
+
+  // =================================================================
+
+  /** Describes a service type. */
+  public static final class ServiceDescriptor implements GenericDescriptor {
+    /**
+     * Get the index of this descriptor within its parent.
+     * * @see Descriptors.Descriptor#getIndex()
+     */
+    public int getIndex() { return index; }
+
+    /** Convert the descriptor to its protocol message representation. */
+    public ServiceDescriptorProto toProto() { return proto; }
+
+    /** Get the type's unqualified name. */
+    public String getName() { return proto.getName(); }
+
+    /**
+     * Get the type's fully-qualified name.
+     * @see Descriptor#getFullName()
+     */
+    public String getFullName() { return fullName; }
+
+    /** Get the {@link FileDescriptor} containing this descriptor. */
+    public FileDescriptor getFile() { return file; }
+
+    /** Get the {@code ServiceOptions}, defined in {@code descriptor.proto}. */
+    public ServiceOptions getOptions() { return proto.getOptions(); }
+
+    /** Get a list of methods for this service. */
+    public List<MethodDescriptor> getMethods() {
+      return Collections.unmodifiableList(Arrays.asList(methods));
+    }
+
+    /**
+     * Find a method by name.
+     * @param name The unqualified name of the method (e.g. "Foo").
+     * @return the method's decsriptor, or {@code null} if not found.
+     */
+    public MethodDescriptor findMethodByName(final String name) {
+      final GenericDescriptor result =
+          file.pool.findSymbol(fullName + '.' + name);
+      if (result != null && result instanceof MethodDescriptor) {
+        return (MethodDescriptor)result;
+      } else {
+        return null;
+      }
+    }
+
+    private final int index;
+    private ServiceDescriptorProto proto;
+    private final String fullName;
+    private final FileDescriptor file;
+    private MethodDescriptor[] methods;
+
+    private ServiceDescriptor(final ServiceDescriptorProto proto,
+                              final FileDescriptor file,
+                              final int index)
+                       throws DescriptorValidationException {
+      this.index = index;
+      this.proto = proto;
+      fullName = computeFullName(file, null, proto.getName());
+      this.file = file;
+
+      methods = new MethodDescriptor[proto.getMethodCount()];
+      for (int i = 0; i < proto.getMethodCount(); i++) {
+        methods[i] = new MethodDescriptor(
+          proto.getMethod(i), file, this, i);
+      }
+
+      file.pool.addSymbol(this);
+    }
+
+    private void crossLink() throws DescriptorValidationException {
+      for (final MethodDescriptor method : methods) {
+        method.crossLink();
+      }
+    }
+
+    /** See {@link FileDescriptor#setProto}. */
+    private void setProto(final ServiceDescriptorProto proto) {
+      this.proto = proto;
+
+      for (int i = 0; i < methods.length; i++) {
+        methods[i].setProto(proto.getMethod(i));
+      }
+    }
+  }
+
+  // =================================================================
+
+  /**
+   * Describes one method within a service type.
+   */
+  public static final class MethodDescriptor implements GenericDescriptor {
+    /**
+     * Get the index of this descriptor within its parent.
+     * * @see Descriptors.Descriptor#getIndex()
+     */
+    public int getIndex() { return index; }
+
+    /** Convert the descriptor to its protocol message representation. */
+    public MethodDescriptorProto toProto() { return proto; }
+
+    /** Get the method's unqualified name. */
+    public String getName() { return proto.getName(); }
+
+    /**
+     * Get the method's fully-qualified name.
+     * @see Descriptor#getFullName()
+     */
+    public String getFullName() { return fullName; }
+
+    /** Get the {@link FileDescriptor} containing this descriptor. */
+    public FileDescriptor getFile() { return file; }
+
+    /** Get the method's service type. */
+    public ServiceDescriptor getService() { return service; }
+
+    /** Get the method's input type. */
+    public Descriptor getInputType() { return inputType; }
+
+    /** Get the method's output type. */
+    public Descriptor getOutputType() { return outputType; }
+
+    /**
+     * Get the {@code MethodOptions}, defined in {@code descriptor.proto}.
+     */
+    public MethodOptions getOptions() { return proto.getOptions(); }
+
+    private final int index;
+    private MethodDescriptorProto proto;
+    private final String fullName;
+    private final FileDescriptor file;
+    private final ServiceDescriptor service;
+
+    // Initialized during cross-linking.
+    private Descriptor inputType;
+    private Descriptor outputType;
+
+    private MethodDescriptor(final MethodDescriptorProto proto,
+                             final FileDescriptor file,
+                             final ServiceDescriptor parent,
+                             final int index)
+                      throws DescriptorValidationException {
+      this.index = index;
+      this.proto = proto;
+      this.file = file;
+      service = parent;
+
+      fullName = parent.getFullName() + '.' + proto.getName();
+
+      file.pool.addSymbol(this);
+    }
+
+    private void crossLink() throws DescriptorValidationException {
+      final GenericDescriptor input =
+        file.pool.lookupSymbol(proto.getInputType(), this);
+      if (!(input instanceof Descriptor)) {
+        throw new DescriptorValidationException(this,
+            '\"' + proto.getInputType() + "\" is not a message type.");
+      }
+      inputType = (Descriptor)input;
+
+      final GenericDescriptor output =
+        file.pool.lookupSymbol(proto.getOutputType(), this);
+      if (!(output instanceof Descriptor)) {
+        throw new DescriptorValidationException(this,
+            '\"' + proto.getOutputType() + "\" is not a message type.");
+      }
+      outputType = (Descriptor)output;
+    }
+
+    /** See {@link FileDescriptor#setProto}. */
+    private void setProto(final MethodDescriptorProto proto) {
+      this.proto = proto;
+    }
+  }
+
+  // =================================================================
+
+  private static String computeFullName(final FileDescriptor file,
+                                        final Descriptor parent,
+                                        final String name) {
+    if (parent != null) {
+      return parent.getFullName() + '.' + name;
+    } else if (file.getPackage().length() > 0) {
+      return file.getPackage() + '.' + name;
+    } else {
+      return name;
+    }
+  }
+
+  // =================================================================
+
+  /**
+   * All descriptors except {@code FileDescriptor} implement this to make
+   * {@code DescriptorPool}'s life easier.
+   */
+  private interface GenericDescriptor {
+    Message toProto();
+    String getName();
+    String getFullName();
+    FileDescriptor getFile();
+  }
+
+  /**
+   * Thrown when building descriptors fails because the source DescriptorProtos
+   * are not valid.
+   */
+  public static class DescriptorValidationException extends Exception {
+    private static final long serialVersionUID = 5750205775490483148L;
+
+    /** Gets the full name of the descriptor where the error occurred. */
+    public String getProblemSymbolName() { return name; }
+
+    /**
+     * Gets the the protocol message representation of the invalid descriptor.
+     */
+    public Message getProblemProto() { return proto; }
+
+    /**
+     * Gets a human-readable description of the error.
+     */
+    public String getDescription() { return description; }
+
+    private final String name;
+    private final Message proto;
+    private final String description;
+
+    private DescriptorValidationException(
+        final GenericDescriptor problemDescriptor,
+        final String description) {
+      this(problemDescriptor, description, null);
+    }
+
+    private DescriptorValidationException(
+        final GenericDescriptor problemDescriptor,
+        final String description,
+        final Throwable cause) {
+      super(problemDescriptor.getFullName() + ": " + description, cause);
+
+      // Note that problemDescriptor may be partially uninitialized, so we
+      // don't want to expose it directly to the user.  So, we only provide
+      // the name and the original proto.
+      name = problemDescriptor.getFullName();
+      proto = problemDescriptor.toProto();
+      this.description = description;
+    }
+
+    private DescriptorValidationException(
+        final FileDescriptor problemDescriptor,
+        final String description) {
+      super(problemDescriptor.getName() + ": " + description);
+
+      // Note that problemDescriptor may be partially uninitialized, so we
+      // don't want to expose it directly to the user.  So, we only provide
+      // the name and the original proto.
+      name = problemDescriptor.getName();
+      proto = problemDescriptor.toProto();
+      this.description = description;
+    }
+  }
+
+  // =================================================================
+
+  /**
+   * A private helper class which contains lookup tables containing all the
+   * descriptors defined in a particular file.
+   */
+  private static final class DescriptorPool {
+    DescriptorPool(final FileDescriptor[] dependencies) {
+      this.dependencies = new DescriptorPool[dependencies.length];
+
+      for (int i = 0; i < dependencies.length; i++)  {
+        this.dependencies[i] = dependencies[i].pool;
+      }
+
+      for (final FileDescriptor dependency : dependencies) {
+        try {
+          addPackage(dependency.getPackage(), dependency);
+        } catch (DescriptorValidationException e) {
+          // Can't happen, because addPackage() only fails when the name
+          // conflicts with a non-package, but we have not yet added any
+          // non-packages at this point.
+          assert false;
+        }
+      }
+    }
+
+    private final DescriptorPool[] dependencies;
+
+    private final Map<String, GenericDescriptor> descriptorsByName =
+      new HashMap<String, GenericDescriptor>();
+    private final Map<DescriptorIntPair, FieldDescriptor> fieldsByNumber =
+      new HashMap<DescriptorIntPair, FieldDescriptor>();
+    private final Map<DescriptorIntPair, EnumValueDescriptor> enumValuesByNumber
+        = new HashMap<DescriptorIntPair, EnumValueDescriptor>();
+
+    /** Find a generic descriptor by fully-qualified name. */
+    GenericDescriptor findSymbol(final String fullName) {
+      GenericDescriptor result = descriptorsByName.get(fullName);
+      if (result != null) {
+        return result;
+      }
+
+      for (final DescriptorPool dependency : dependencies) {
+        result = dependency.descriptorsByName.get(fullName);
+        if (result != null) {
+          return result;
+        }
+      }
+
+      return null;
+    }
+
+    /**
+     * Look up a descriptor by name, relative to some other descriptor.
+     * The name may be fully-qualified (with a leading '.'),
+     * partially-qualified, or unqualified.  C++-like name lookup semantics
+     * are used to search for the matching descriptor.
+     */
+    GenericDescriptor lookupSymbol(final String name,
+                                   final GenericDescriptor relativeTo)
+                            throws DescriptorValidationException {
+      // TODO(kenton):  This could be optimized in a number of ways.
+
+      GenericDescriptor result;
+      if (name.startsWith(".")) {
+        // Fully-qualified name.
+        result = findSymbol(name.substring(1));
+      } else {
+        // If "name" is a compound identifier, we want to search for the
+        // first component of it, then search within it for the rest.
+        final int firstPartLength = name.indexOf('.');
+        final String firstPart;
+        if (firstPartLength == -1) {
+          firstPart = name;
+        } else {
+          firstPart = name.substring(0, firstPartLength);
+        }
+
+        // We will search each parent scope of "relativeTo" looking for the
+        // symbol.
+        final StringBuilder scopeToTry =
+            new StringBuilder(relativeTo.getFullName());
+
+        while (true) {
+          // Chop off the last component of the scope.
+          final int dotpos = scopeToTry.lastIndexOf(".");
+          if (dotpos == -1) {
+            result = findSymbol(name);
+            break;
+          } else {
+            scopeToTry.setLength(dotpos + 1);
+
+            // Append firstPart and try to find.
+            scopeToTry.append(firstPart);
+            result = findSymbol(scopeToTry.toString());
+
+            if (result != null) {
+              if (firstPartLength != -1) {
+                // We only found the first part of the symbol.  Now look for
+                // the whole thing.  If this fails, we *don't* want to keep
+                // searching parent scopes.
+                scopeToTry.setLength(dotpos + 1);
+                scopeToTry.append(name);
+                result = findSymbol(scopeToTry.toString());
+              }
+              break;
+            }
+
+            // Not found.  Remove the name so we can try again.
+            scopeToTry.setLength(dotpos);
+          }
+        }
+      }
+
+      if (result == null) {
+        throw new DescriptorValidationException(relativeTo,
+            '\"' + name + "\" is not defined.");
+      } else {
+        return result;
+      }
+    }
+
+    /**
+     * Adds a symbol to the symbol table.  If a symbol with the same name
+     * already exists, throws an error.
+     */
+    void addSymbol(final GenericDescriptor descriptor)
+            throws DescriptorValidationException {
+      validateSymbolName(descriptor);
+
+      final String fullName = descriptor.getFullName();
+      final int dotpos = fullName.lastIndexOf('.');
+
+      final GenericDescriptor old = descriptorsByName.put(fullName, descriptor);
+      if (old != null) {
+        descriptorsByName.put(fullName, old);
+
+        if (descriptor.getFile() == old.getFile()) {
+          if (dotpos == -1) {
+            throw new DescriptorValidationException(descriptor,
+                '\"' + fullName + "\" is already defined.");
+          } else {
+            throw new DescriptorValidationException(descriptor,
+                '\"' + fullName.substring(dotpos + 1) +
+              "\" is already defined in \"" +
+              fullName.substring(0, dotpos) + "\".");
+          }
+        } else {
+          throw new DescriptorValidationException(descriptor,
+              '\"' + fullName + "\" is already defined in file \"" +
+            old.getFile().getName() + "\".");
+        }
+      }
+    }
+
+    /**
+     * Represents a package in the symbol table.  We use PackageDescriptors
+     * just as placeholders so that someone cannot define, say, a message type
+     * that has the same name as an existing package.
+     */
+    private static final class PackageDescriptor implements GenericDescriptor {
+      public Message toProto()        { return file.toProto(); }
+      public String getName()         { return name;           }
+      public String getFullName()     { return fullName;       }
+      public FileDescriptor getFile() { return file;           }
+
+      PackageDescriptor(final String name, final String fullName,
+                        final FileDescriptor file) {
+        this.file = file;
+        this.fullName = fullName;
+        this.name = name;
+      }
+
+      private final String name;
+      private final String fullName;
+      private final FileDescriptor file;
+    }
+
+    /**
+     * Adds a package to the symbol tables.  If a package by the same name
+     * already exists, that is fine, but if some other kind of symbol exists
+     * under the same name, an exception is thrown.  If the package has
+     * multiple components, this also adds the parent package(s).
+     */
+    void addPackage(final String fullName, final FileDescriptor file)
+             throws DescriptorValidationException {
+      final int dotpos = fullName.lastIndexOf('.');
+      final String name;
+      if (dotpos == -1) {
+        name = fullName;
+      } else {
+        addPackage(fullName.substring(0, dotpos), file);
+        name = fullName.substring(dotpos + 1);
+      }
+
+      final GenericDescriptor old =
+        descriptorsByName.put(fullName,
+          new PackageDescriptor(name, fullName, file));
+      if (old != null) {
+        descriptorsByName.put(fullName, old);
+        if (!(old instanceof PackageDescriptor)) {
+          throw new DescriptorValidationException(file,
+              '\"' + name + "\" is already defined (as something other than a "
+              + "package) in file \"" + old.getFile().getName() + "\".");
+        }
+      }
+    }
+
+    /** A (GenericDescriptor, int) pair, used as a map key. */
+    private static final class DescriptorIntPair {
+      private final GenericDescriptor descriptor;
+      private final int number;
+
+      DescriptorIntPair(final GenericDescriptor descriptor, final int number) {
+        this.descriptor = descriptor;
+        this.number = number;
+      }
+
+      @Override
+      public int hashCode() {
+        return descriptor.hashCode() * ((1 << 16) - 1) + number;
+      }
+      @Override
+      public boolean equals(final Object obj) {
+        if (!(obj instanceof DescriptorIntPair)) {
+          return false;
+        }
+        final DescriptorIntPair other = (DescriptorIntPair)obj;
+        return descriptor == other.descriptor && number == other.number;
+      }
+    }
+
+    /**
+     * Adds a field to the fieldsByNumber table.  Throws an exception if a
+     * field with hte same containing type and number already exists.
+     */
+    void addFieldByNumber(final FieldDescriptor field)
+                   throws DescriptorValidationException {
+      final DescriptorIntPair key =
+        new DescriptorIntPair(field.getContainingType(), field.getNumber());
+      final FieldDescriptor old = fieldsByNumber.put(key, field);
+      if (old != null) {
+        fieldsByNumber.put(key, old);
+        throw new DescriptorValidationException(field,
+          "Field number " + field.getNumber() +
+          "has already been used in \"" +
+          field.getContainingType().getFullName() +
+          "\" by field \"" + old.getName() + "\".");
+      }
+    }
+
+    /**
+     * Adds an enum value to the enumValuesByNumber table.  If an enum value
+     * with the same type and number already exists, does nothing.  (This is
+     * allowed; the first value define with the number takes precedence.)
+     */
+    void addEnumValueByNumber(final EnumValueDescriptor value) {
+      final DescriptorIntPair key =
+        new DescriptorIntPair(value.getType(), value.getNumber());
+      final EnumValueDescriptor old = enumValuesByNumber.put(key, value);
+      if (old != null) {
+        enumValuesByNumber.put(key, old);
+        // Not an error:  Multiple enum values may have the same number, but
+        // we only want the first one in the map.
+      }
+    }
+
+    /**
+     * Verifies that the descriptor's name is valid (i.e. it contains only
+     * letters, digits, and underscores, and does not start with a digit).
+     */
+    static void validateSymbolName(final GenericDescriptor descriptor)
+                                   throws DescriptorValidationException {
+      final String name = descriptor.getName();
+      if (name.length() == 0) {
+        throw new DescriptorValidationException(descriptor, "Missing name.");
+      } else {
+        boolean valid = true;
+        for (int i = 0; i < name.length(); i++) {
+          final char c = name.charAt(i);
+          // Non-ASCII characters are not valid in protobuf identifiers, even
+          // if they are letters or digits.
+          if (c >= 128) {
+            valid = false;
+          }
+          // First character must be letter or _.  Subsequent characters may
+          // be letters, numbers, or digits.
+          if (Character.isLetter(c) || c == '_' ||
+              (Character.isDigit(c) && i > 0)) {
+            // Valid
+          } else {
+            valid = false;
+          }
+        }
+        if (!valid) {
+          throw new DescriptorValidationException(descriptor,
+              '\"' + name + "\" is not a valid identifier.");
+        }
+      }
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/DynamicMessage.java b/java/src/main/java/com/google/protobuf/DynamicMessage.java
new file mode 100644
index 0000000..c106b66
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/DynamicMessage.java
@@ -0,0 +1,438 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+import java.io.InputStream;
+import java.io.IOException;
+import java.util.Map;
+
+/**
+ * An implementation of {@link Message} that can represent arbitrary types,
+ * given a {@link Descriptors.Descriptor}.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class DynamicMessage extends AbstractMessage {
+  private final Descriptor type;
+  private final FieldSet<FieldDescriptor> fields;
+  private final UnknownFieldSet unknownFields;
+  private int memoizedSize = -1;
+
+  /**
+   * Construct a {@code DynamicMessage} using the given {@code FieldSet}.
+   */
+  private DynamicMessage(Descriptor type, FieldSet<FieldDescriptor> fields,
+                         UnknownFieldSet unknownFields) {
+    this.type = type;
+    this.fields = fields;
+    this.unknownFields = unknownFields;
+  }
+
+  /**
+   * Get a {@code DynamicMessage} representing the default instance of the
+   * given type.
+   */
+  public static DynamicMessage getDefaultInstance(Descriptor type) {
+    return new DynamicMessage(type, FieldSet.<FieldDescriptor>emptySet(),
+                              UnknownFieldSet.getDefaultInstance());
+  }
+
+  /** Parse a message of the given type from the given input stream. */
+  public static DynamicMessage parseFrom(Descriptor type,
+                                         CodedInputStream input)
+                                         throws IOException {
+    return newBuilder(type).mergeFrom(input).buildParsed();
+  }
+
+  /** Parse a message of the given type from the given input stream. */
+  public static DynamicMessage parseFrom(
+      Descriptor type,
+      CodedInputStream input,
+      ExtensionRegistry extensionRegistry)
+      throws IOException {
+    return newBuilder(type).mergeFrom(input, extensionRegistry).buildParsed();
+  }
+
+  /** Parse {@code data} as a message of the given type and return it. */
+  public static DynamicMessage parseFrom(Descriptor type, ByteString data)
+                                         throws InvalidProtocolBufferException {
+    return newBuilder(type).mergeFrom(data).buildParsed();
+  }
+
+  /** Parse {@code data} as a message of the given type and return it. */
+  public static DynamicMessage parseFrom(Descriptor type, ByteString data,
+                                         ExtensionRegistry extensionRegistry)
+                                         throws InvalidProtocolBufferException {
+    return newBuilder(type).mergeFrom(data, extensionRegistry).buildParsed();
+  }
+
+  /** Parse {@code data} as a message of the given type and return it. */
+  public static DynamicMessage parseFrom(Descriptor type, byte[] data)
+                                         throws InvalidProtocolBufferException {
+    return newBuilder(type).mergeFrom(data).buildParsed();
+  }
+
+  /** Parse {@code data} as a message of the given type and return it. */
+  public static DynamicMessage parseFrom(Descriptor type, byte[] data,
+                                         ExtensionRegistry extensionRegistry)
+                                         throws InvalidProtocolBufferException {
+    return newBuilder(type).mergeFrom(data, extensionRegistry).buildParsed();
+  }
+
+  /** Parse a message of the given type from {@code input} and return it. */
+  public static DynamicMessage parseFrom(Descriptor type, InputStream input)
+                                         throws IOException {
+    return newBuilder(type).mergeFrom(input).buildParsed();
+  }
+
+  /** Parse a message of the given type from {@code input} and return it. */
+  public static DynamicMessage parseFrom(Descriptor type, InputStream input,
+                                         ExtensionRegistry extensionRegistry)
+                                         throws IOException {
+    return newBuilder(type).mergeFrom(input, extensionRegistry).buildParsed();
+  }
+
+  /** Construct a {@link Message.Builder} for the given type. */
+  public static Builder newBuilder(Descriptor type) {
+    return new Builder(type);
+  }
+
+  /**
+   * Construct a {@link Message.Builder} for a message of the same type as
+   * {@code prototype}, and initialize it with {@code prototype}'s contents.
+   */
+  public static Builder newBuilder(Message prototype) {
+    return new Builder(prototype.getDescriptorForType()).mergeFrom(prototype);
+  }
+
+  // -----------------------------------------------------------------
+  // Implementation of Message interface.
+
+  public Descriptor getDescriptorForType() {
+    return type;
+  }
+
+  public DynamicMessage getDefaultInstanceForType() {
+    return getDefaultInstance(type);
+  }
+
+  public Map<FieldDescriptor, Object> getAllFields() {
+    return fields.getAllFields();
+  }
+
+  public boolean hasField(FieldDescriptor field) {
+    verifyContainingType(field);
+    return fields.hasField(field);
+  }
+
+  public Object getField(FieldDescriptor field) {
+    verifyContainingType(field);
+    Object result = fields.getField(field);
+    if (result == null) {
+      if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+        result = getDefaultInstance(field.getMessageType());
+      } else {
+        result = field.getDefaultValue();
+      }
+    }
+    return result;
+  }
+
+  public int getRepeatedFieldCount(FieldDescriptor field) {
+    verifyContainingType(field);
+    return fields.getRepeatedFieldCount(field);
+  }
+
+  public Object getRepeatedField(FieldDescriptor field, int index) {
+    verifyContainingType(field);
+    return fields.getRepeatedField(field, index);
+  }
+
+  public UnknownFieldSet getUnknownFields() {
+    return unknownFields;
+  }
+
+  private static boolean isInitialized(Descriptor type,
+                                       FieldSet<FieldDescriptor> fields) {
+    // Check that all required fields are present.
+    for (final FieldDescriptor field : type.getFields()) {
+      if (field.isRequired()) {
+        if (!fields.hasField(field)) {
+          return false;
+        }
+      }
+    }
+
+    // Check that embedded messages are initialized.
+    return fields.isInitialized();
+  }
+
+  public boolean isInitialized() {
+    return isInitialized(type, fields);
+  }
+
+  public void writeTo(CodedOutputStream output) throws IOException {
+    if (type.getOptions().getMessageSetWireFormat()) {
+      fields.writeMessageSetTo(output);
+      unknownFields.writeAsMessageSetTo(output);
+    } else {
+      fields.writeTo(output);
+      unknownFields.writeTo(output);
+    }
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    if (type.getOptions().getMessageSetWireFormat()) {
+      size = fields.getMessageSetSerializedSize();
+      size += unknownFields.getSerializedSizeAsMessageSet();
+    } else {
+      size = fields.getSerializedSize();
+      size += unknownFields.getSerializedSize();
+    }
+
+    memoizedSize = size;
+    return size;
+  }
+
+  public Builder newBuilderForType() {
+    return new Builder(type);
+  }
+
+  public Builder toBuilder() {
+    return newBuilderForType().mergeFrom(this);
+  }
+
+  /** Verifies that the field is a field of this message. */
+  private void verifyContainingType(FieldDescriptor field) {
+    if (field.getContainingType() != type) {
+      throw new IllegalArgumentException(
+        "FieldDescriptor does not match message type.");
+    }
+  }
+
+  // =================================================================
+
+  /**
+   * Builder for {@link DynamicMessage}s.
+   */
+  public static final class Builder extends AbstractMessage.Builder<Builder> {
+    private final Descriptor type;
+    private FieldSet<FieldDescriptor> fields;
+    private UnknownFieldSet unknownFields;
+
+    /** Construct a {@code Builder} for the given type. */
+    private Builder(Descriptor type) {
+      this.type = type;
+      this.fields = FieldSet.newFieldSet();
+      this.unknownFields = UnknownFieldSet.getDefaultInstance();
+    }
+
+    // ---------------------------------------------------------------
+    // Implementation of Message.Builder interface.
+
+    public Builder clear() {
+      if (fields == null) {
+        throw new IllegalStateException("Cannot call clear() after build().");
+      }
+      fields.clear();
+      return this;
+    }
+
+    public Builder mergeFrom(Message other) {
+      if (other instanceof DynamicMessage) {
+        // This should be somewhat faster than calling super.mergeFrom().
+        DynamicMessage otherDynamicMessage = (DynamicMessage) other;
+        if (otherDynamicMessage.type != type) {
+          throw new IllegalArgumentException(
+            "mergeFrom(Message) can only merge messages of the same type.");
+        }
+        fields.mergeFrom(otherDynamicMessage.fields);
+        mergeUnknownFields(otherDynamicMessage.unknownFields);
+        return this;
+      } else {
+        return super.mergeFrom(other);
+      }
+    }
+
+    public DynamicMessage build() {
+      // If fields == null, we'll throw an appropriate exception later.
+      if (fields != null && !isInitialized()) {
+        throw newUninitializedMessageException(
+          new DynamicMessage(type, fields, unknownFields));
+      }
+      return buildPartial();
+    }
+
+    /**
+     * Helper for DynamicMessage.parseFrom() methods to call.  Throws
+     * {@link InvalidProtocolBufferException} instead of
+     * {@link UninitializedMessageException}.
+     */
+    private DynamicMessage buildParsed() throws InvalidProtocolBufferException {
+      if (!isInitialized()) {
+        throw newUninitializedMessageException(
+            new DynamicMessage(type, fields, unknownFields))
+          .asInvalidProtocolBufferException();
+      }
+      return buildPartial();
+    }
+
+    public DynamicMessage buildPartial() {
+      if (fields == null) {
+        throw new IllegalStateException(
+            "build() has already been called on this Builder.");
+      }
+      fields.makeImmutable();
+      DynamicMessage result =
+        new DynamicMessage(type, fields, unknownFields);
+      fields = null;
+      unknownFields = null;
+      return result;
+    }
+
+    public Builder clone() {
+      Builder result = new Builder(type);
+      result.fields.mergeFrom(fields);
+      return result;
+    }
+
+    public boolean isInitialized() {
+      return DynamicMessage.isInitialized(type, fields);
+    }
+
+    public Descriptor getDescriptorForType() {
+      return type;
+    }
+
+    public DynamicMessage getDefaultInstanceForType() {
+      return getDefaultInstance(type);
+    }
+
+    public Map<FieldDescriptor, Object> getAllFields() {
+      return fields.getAllFields();
+    }
+
+    public Builder newBuilderForField(FieldDescriptor field) {
+      verifyContainingType(field);
+
+      if (field.getJavaType() != FieldDescriptor.JavaType.MESSAGE) {
+        throw new IllegalArgumentException(
+          "newBuilderForField is only valid for fields with message type.");
+      }
+
+      return new Builder(field.getMessageType());
+    }
+
+    public boolean hasField(FieldDescriptor field) {
+      verifyContainingType(field);
+      return fields.hasField(field);
+    }
+
+    public Object getField(FieldDescriptor field) {
+      verifyContainingType(field);
+      Object result = fields.getField(field);
+      if (result == null) {
+        if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+          result = getDefaultInstance(field.getMessageType());
+        } else {
+          result = field.getDefaultValue();
+        }
+      }
+      return result;
+    }
+
+    public Builder setField(FieldDescriptor field, Object value) {
+      verifyContainingType(field);
+      fields.setField(field, value);
+      return this;
+    }
+
+    public Builder clearField(FieldDescriptor field) {
+      verifyContainingType(field);
+      fields.clearField(field);
+      return this;
+    }
+
+    public int getRepeatedFieldCount(FieldDescriptor field) {
+      verifyContainingType(field);
+      return fields.getRepeatedFieldCount(field);
+    }
+
+    public Object getRepeatedField(FieldDescriptor field, int index) {
+      verifyContainingType(field);
+      return fields.getRepeatedField(field, index);
+    }
+
+    public Builder setRepeatedField(FieldDescriptor field,
+                                    int index, Object value) {
+      verifyContainingType(field);
+      fields.setRepeatedField(field, index, value);
+      return this;
+    }
+
+    public Builder addRepeatedField(FieldDescriptor field, Object value) {
+      verifyContainingType(field);
+      fields.addRepeatedField(field, value);
+      return this;
+    }
+
+    public UnknownFieldSet getUnknownFields() {
+      return unknownFields;
+    }
+
+    public Builder setUnknownFields(UnknownFieldSet unknownFields) {
+      this.unknownFields = unknownFields;
+      return this;
+    }
+
+    public Builder mergeUnknownFields(UnknownFieldSet unknownFields) {
+      this.unknownFields =
+        UnknownFieldSet.newBuilder(this.unknownFields)
+                       .mergeFrom(unknownFields)
+                       .build();
+      return this;
+    }
+
+    /** Verifies that the field is a field of this message. */
+    private void verifyContainingType(FieldDescriptor field) {
+      if (field.getContainingType() != type) {
+        throw new IllegalArgumentException(
+          "FieldDescriptor does not match message type.");
+      }
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/ExtensionRegistry.java b/java/src/main/java/com/google/protobuf/ExtensionRegistry.java
new file mode 100644
index 0000000..87bbd6e
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/ExtensionRegistry.java
@@ -0,0 +1,261 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A table of known extensions, searchable by name or field number.  When
+ * parsing a protocol message that might have extensions, you must provide
+ * an {@code ExtensionRegistry} in which you have registered any extensions
+ * that you want to be able to parse.  Otherwise, those extensions will just
+ * be treated like unknown fields.
+ *
+ * <p>For example, if you had the {@code .proto} file:
+ *
+ * <pre>
+ * option java_class = "MyProto";
+ *
+ * message Foo {
+ *   extensions 1000 to max;
+ * }
+ *
+ * extend Foo {
+ *   optional int32 bar;
+ * }
+ * </pre>
+ *
+ * Then you might write code like:
+ *
+ * <pre>
+ * ExtensionRegistry registry = ExtensionRegistry.newInstance();
+ * registry.add(MyProto.bar);
+ * MyProto.Foo message = MyProto.Foo.parseFrom(input, registry);
+ * </pre>
+ *
+ * <p>Background:
+ *
+ * <p>You might wonder why this is necessary.  Two alternatives might come to
+ * mind.  First, you might imagine a system where generated extensions are
+ * automatically registered when their containing classes are loaded.  This
+ * is a popular technique, but is bad design; among other things, it creates a
+ * situation where behavior can change depending on what classes happen to be
+ * loaded.  It also introduces a security vulnerability, because an
+ * unprivileged class could cause its code to be called unexpectedly from a
+ * privileged class by registering itself as an extension of the right type.
+ *
+ * <p>Another option you might consider is lazy parsing: do not parse an
+ * extension until it is first requested, at which point the caller must
+ * provide a type to use.  This introduces a different set of problems.  First,
+ * it would require a mutex lock any time an extension was accessed, which
+ * would be slow.  Second, corrupt data would not be detected until first
+ * access, at which point it would be much harder to deal with it.  Third, it
+ * could violate the expectation that message objects are immutable, since the
+ * type provided could be any arbitrary message class.  An unprivileged user
+ * could take advantage of this to inject a mutable object into a message
+ * belonging to privileged code and create mischief.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class ExtensionRegistry extends ExtensionRegistryLite {
+  /** Construct a new, empty instance. */
+  public static ExtensionRegistry newInstance() {
+    return new ExtensionRegistry();
+  }
+
+  /** Get the unmodifiable singleton empty instance. */
+  public static ExtensionRegistry getEmptyRegistry() {
+    return EMPTY;
+  }
+
+  /** Returns an unmodifiable view of the registry. */
+  @Override
+  public ExtensionRegistry getUnmodifiable() {
+    return new ExtensionRegistry(this);
+  }
+
+  /** A (Descriptor, Message) pair, returned by lookup methods. */
+  public static final class ExtensionInfo {
+    /** The extension's descriptor. */
+    public final FieldDescriptor descriptor;
+
+    /**
+     * A default instance of the extension's type, if it has a message type.
+     * Otherwise, {@code null}.
+     */
+    public final Message defaultInstance;
+
+    private ExtensionInfo(final FieldDescriptor descriptor) {
+      this.descriptor = descriptor;
+      defaultInstance = null;
+    }
+    private ExtensionInfo(final FieldDescriptor descriptor,
+                          final Message defaultInstance) {
+      this.descriptor = descriptor;
+      this.defaultInstance = defaultInstance;
+    }
+  }
+
+  /**
+   * Find an extension by fully-qualified field name, in the proto namespace.
+   * I.e. {@code result.descriptor.fullName()} will match {@code fullName} if
+   * a match is found.
+   *
+   * @return Information about the extension if found, or {@code null}
+   *         otherwise.
+   */
+  public ExtensionInfo findExtensionByName(final String fullName) {
+    return extensionsByName.get(fullName);
+  }
+
+  /**
+   * Find an extension by containing type and field number.
+   *
+   * @return Information about the extension if found, or {@code null}
+   *         otherwise.
+   */
+  public ExtensionInfo findExtensionByNumber(final Descriptor containingType,
+                                             final int fieldNumber) {
+    return extensionsByNumber.get(
+      new DescriptorIntPair(containingType, fieldNumber));
+  }
+
+  /** Add an extension from a generated file to the registry. */
+  public void add(final GeneratedMessage.GeneratedExtension<?, ?> extension) {
+    if (extension.getDescriptor().getJavaType() ==
+        FieldDescriptor.JavaType.MESSAGE) {
+      add(new ExtensionInfo(extension.getDescriptor(),
+                            extension.getMessageDefaultInstance()));
+    } else {
+      add(new ExtensionInfo(extension.getDescriptor(), null));
+    }
+  }
+
+  /** Add a non-message-type extension to the registry by descriptor. */
+  public void add(final FieldDescriptor type) {
+    if (type.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+      throw new IllegalArgumentException(
+        "ExtensionRegistry.add() must be provided a default instance when " +
+        "adding an embedded message extension.");
+    }
+    add(new ExtensionInfo(type, null));
+  }
+
+  /** Add a message-type extension to the registry by descriptor. */
+  public void add(final FieldDescriptor type, final Message defaultInstance) {
+    if (type.getJavaType() != FieldDescriptor.JavaType.MESSAGE) {
+      throw new IllegalArgumentException(
+        "ExtensionRegistry.add() provided a default instance for a " +
+        "non-message extension.");
+    }
+    add(new ExtensionInfo(type, defaultInstance));
+  }
+
+  // =================================================================
+  // Private stuff.
+
+  private ExtensionRegistry() {
+    this.extensionsByName = new HashMap<String, ExtensionInfo>();
+    this.extensionsByNumber = new HashMap<DescriptorIntPair, ExtensionInfo>();
+  }
+
+  private ExtensionRegistry(ExtensionRegistry other) {
+    super(other);
+    this.extensionsByName = Collections.unmodifiableMap(other.extensionsByName);
+    this.extensionsByNumber =
+        Collections.unmodifiableMap(other.extensionsByNumber);
+  }
+
+  private final Map<String, ExtensionInfo> extensionsByName;
+  private final Map<DescriptorIntPair, ExtensionInfo> extensionsByNumber;
+
+  private ExtensionRegistry(boolean empty) {
+    super(ExtensionRegistryLite.getEmptyRegistry());
+    this.extensionsByName = Collections.<String, ExtensionInfo>emptyMap();
+    this.extensionsByNumber =
+        Collections.<DescriptorIntPair, ExtensionInfo>emptyMap();
+  }
+  private static final ExtensionRegistry EMPTY = new ExtensionRegistry(true);
+
+  private void add(final ExtensionInfo extension) {
+    if (!extension.descriptor.isExtension()) {
+      throw new IllegalArgumentException(
+        "ExtensionRegistry.add() was given a FieldDescriptor for a regular " +
+        "(non-extension) field.");
+    }
+
+    extensionsByName.put(extension.descriptor.getFullName(), extension);
+    extensionsByNumber.put(
+      new DescriptorIntPair(extension.descriptor.getContainingType(),
+                            extension.descriptor.getNumber()),
+      extension);
+
+    final FieldDescriptor field = extension.descriptor;
+    if (field.getContainingType().getOptions().getMessageSetWireFormat() &&
+        field.getType() == FieldDescriptor.Type.MESSAGE &&
+        field.isOptional() &&
+        field.getExtensionScope() == field.getMessageType()) {
+      // This is an extension of a MessageSet type defined within the extension
+      // type's own scope.  For backwards-compatibility, allow it to be looked
+      // up by type name.
+      extensionsByName.put(field.getMessageType().getFullName(), extension);
+    }
+  }
+
+  /** A (GenericDescriptor, int) pair, used as a map key. */
+  private static final class DescriptorIntPair {
+    private final Descriptor descriptor;
+    private final int number;
+
+    DescriptorIntPair(final Descriptor descriptor, final int number) {
+      this.descriptor = descriptor;
+      this.number = number;
+    }
+
+    @Override
+    public int hashCode() {
+      return descriptor.hashCode() * ((1 << 16) - 1) + number;
+    }
+    @Override
+    public boolean equals(final Object obj) {
+      if (!(obj instanceof DescriptorIntPair)) {
+        return false;
+      }
+      final DescriptorIntPair other = (DescriptorIntPair)obj;
+      return descriptor == other.descriptor && number == other.number;
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/ExtensionRegistryLite.java b/java/src/main/java/com/google/protobuf/ExtensionRegistryLite.java
new file mode 100644
index 0000000..d5288dd
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/ExtensionRegistryLite.java
@@ -0,0 +1,169 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Equivalent to {@link ExtensionRegistry} but supports only "lite" types.
+ * <p>
+ * If all of your types are lite types, then you only need to use
+ * {@code ExtensionRegistryLite}.  Similarly, if all your types are regular
+ * types, then you only need {@link ExtensionRegistry}.  Typically it does not
+ * make sense to mix the two, since if you have any regular types in your
+ * program, you then require the full runtime and lose all the benefits of
+ * the lite runtime, so you might as well make all your types be regular types.
+ * However, in some cases (e.g. when depending on multiple third-patry libraries
+ * where one uses lite types and one uses regular), you may find yourself
+ * wanting to mix the two.  In this case things get more complicated.
+ * <p>
+ * There are three factors to consider:  Whether the type being extended is
+ * lite, whether the embedded type (in the case of a message-typed extension)
+ * is lite, and whether the extension itself is lite.  Since all three are
+ * declared in different files, they could all be different.  Here are all
+ * the combinations and which type of registry to use:
+ * <pre>
+ *   Extended type     Inner type    Extension         Use registry
+ *   =======================================================================
+ *   lite              lite          lite              ExtensionRegistryLite
+ *   lite              regular       lite              ExtensionRegistry
+ *   regular           regular       regular           ExtensionRegistry
+ *   all other combinations                            not supported
+ * </pre>
+ * <p>
+ * Note that just as regular types are not allowed to contain lite-type fields,
+ * they are also not allowed to contain lite-type extensions.  This is because
+ * regular types must be fully accessible via reflection, which in turn means
+ * that all the inner messages must also support reflection.  On the other hand,
+ * since regular types implement the entire lite interface, there is no problem
+ * with embedding regular types inside lite types.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public class ExtensionRegistryLite {
+  /** Construct a new, empty instance. */
+  public static ExtensionRegistryLite newInstance() {
+    return new ExtensionRegistryLite();
+  }
+
+  /** Get the unmodifiable singleton empty instance. */
+  public static ExtensionRegistryLite getEmptyRegistry() {
+    return EMPTY;
+  }
+
+  /** Returns an unmodifiable view of the registry. */
+  public ExtensionRegistryLite getUnmodifiable() {
+    return new ExtensionRegistryLite(this);
+  }
+
+  /**
+   * Find an extension by containing type and field number.
+   *
+   * @return Information about the extension if found, or {@code null}
+   *         otherwise.
+   */
+  @SuppressWarnings("unchecked")
+  public <ContainingType extends MessageLite>
+      GeneratedMessageLite.GeneratedExtension<ContainingType, ?>
+        findLiteExtensionByNumber(
+          final ContainingType containingTypeDefaultInstance,
+          final int fieldNumber) {
+    return (GeneratedMessageLite.GeneratedExtension<ContainingType, ?>)
+      extensionsByNumber.get(
+        new ObjectIntPair(containingTypeDefaultInstance, fieldNumber));
+  }
+
+  /** Add an extension from a lite generated file to the registry. */
+  public final void add(
+      final GeneratedMessageLite.GeneratedExtension<?, ?> extension) {
+    extensionsByNumber.put(
+      new ObjectIntPair(extension.getContainingTypeDefaultInstance(),
+                        extension.getNumber()),
+      extension);
+  }
+
+  // =================================================================
+  // Private stuff.
+
+  // Constructors are package-private so that ExtensionRegistry can subclass
+  // this.
+
+  ExtensionRegistryLite() {
+    this.extensionsByNumber =
+        new HashMap<ObjectIntPair,
+                    GeneratedMessageLite.GeneratedExtension<?, ?>>();
+  }
+
+  ExtensionRegistryLite(ExtensionRegistryLite other) {
+    if (other == EMPTY) {
+      this.extensionsByNumber = Collections.emptyMap();
+    } else {
+      this.extensionsByNumber =
+        Collections.unmodifiableMap(other.extensionsByNumber);
+    }
+  }
+
+  private final Map<ObjectIntPair,
+                    GeneratedMessageLite.GeneratedExtension<?, ?>>
+      extensionsByNumber;
+
+  private ExtensionRegistryLite(boolean empty) {
+    this.extensionsByNumber = Collections.emptyMap();
+  }
+  private static final ExtensionRegistryLite EMPTY =
+    new ExtensionRegistryLite(true);
+
+  /** A (Object, int) pair, used as a map key. */
+  private static final class ObjectIntPair {
+    private final Object object;
+    private final int number;
+
+    ObjectIntPair(final Object object, final int number) {
+      this.object = object;
+      this.number = number;
+    }
+
+    @Override
+    public int hashCode() {
+      return System.identityHashCode(object) * ((1 << 16) - 1) + number;
+    }
+    @Override
+    public boolean equals(final Object obj) {
+      if (!(obj instanceof ObjectIntPair)) {
+        return false;
+      }
+      final ObjectIntPair other = (ObjectIntPair)obj;
+      return object == other.object && number == other.number;
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/FieldSet.java b/java/src/main/java/com/google/protobuf/FieldSet.java
new file mode 100644
index 0000000..93e55f2
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/FieldSet.java
@@ -0,0 +1,712 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.TreeMap;
+import java.util.List;
+import java.util.Map;
+import java.io.IOException;
+
+/**
+ * A class which represents an arbitrary set of fields of some message type.
+ * This is used to implement {@link DynamicMessage}, and also to represent
+ * extensions in {@link GeneratedMessage}.  This class is package-private,
+ * since outside users should probably be using {@link DynamicMessage}.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+final class FieldSet<FieldDescriptorType extends
+      FieldSet.FieldDescriptorLite<FieldDescriptorType>> {
+  /**
+   * Interface for a FieldDescriptor or lite extension descriptor.  This
+   * prevents FieldSet from depending on {@link Descriptors.FieldDescriptor}.
+   */
+  public interface FieldDescriptorLite<T extends FieldDescriptorLite<T>>
+      extends Comparable<T> {
+    int getNumber();
+    WireFormat.FieldType getLiteType();
+    WireFormat.JavaType getLiteJavaType();
+    boolean isRepeated();
+    boolean isPacked();
+    Internal.EnumLiteMap<?> getEnumType();
+
+    // If getLiteJavaType() == MESSAGE, this merges a message object of the
+    // type into a builder of the type.  Returns {@code to}.
+    MessageLite.Builder internalMergeFrom(
+        MessageLite.Builder to, MessageLite from);
+  }
+
+  private Map<FieldDescriptorType, Object> fields;
+
+  /** Construct a new FieldSet. */
+  private FieldSet() {
+    // Use a TreeMap because fields need to be in canonical order when
+    // serializing.
+    // TODO(kenton):  Maybe use some sort of sparse array instead?  It would
+    //   even make sense to store the first 16 or so tags in a flat array
+    //   to make DynamicMessage faster.
+    fields = new TreeMap<FieldDescriptorType, Object>();
+  }
+
+  /**
+   * Construct an empty FieldSet.  This is only used to initialize
+   * DEFAULT_INSTANCE.
+   */
+  private FieldSet(final boolean dummy) {
+    this.fields = Collections.emptyMap();
+  }
+
+  /** Construct a new FieldSet. */
+  public static <T extends FieldSet.FieldDescriptorLite<T>>
+      FieldSet<T> newFieldSet() {
+    return new FieldSet<T>();
+  }
+
+  /** Get an immutable empty FieldSet. */
+  @SuppressWarnings("unchecked")
+  public static <T extends FieldSet.FieldDescriptorLite<T>>
+      FieldSet<T> emptySet() {
+    return DEFAULT_INSTANCE;
+  }
+  @SuppressWarnings("unchecked")
+  private static final FieldSet DEFAULT_INSTANCE = new FieldSet(true);
+
+  /** Make this FieldSet immutable from this point forward. */
+  @SuppressWarnings("unchecked")
+  public void makeImmutable() {
+    for (final Map.Entry<FieldDescriptorType, Object> entry:
+         fields.entrySet()) {
+      if (entry.getKey().isRepeated()) {
+        final List value = (List)entry.getValue();
+        fields.put(entry.getKey(), Collections.unmodifiableList(value));
+      }
+    }
+    fields = Collections.unmodifiableMap(fields);
+  }
+
+  // =================================================================
+
+  /** See {@link Message.Builder#clear()}. */
+  public void clear() {
+    fields.clear();
+  }
+
+  /**
+   * Get a simple map containing all the fields.
+   */
+  public Map<FieldDescriptorType, Object> getAllFields() {
+    return Collections.unmodifiableMap(fields);
+  }
+
+  /**
+   * Get an iterator to the field map.  This iterator should not be leaked
+   * out of the protobuf library as it is not protected from mutation.
+   */
+  public Iterator<Map.Entry<FieldDescriptorType, Object>> iterator() {
+    return fields.entrySet().iterator();
+  }
+
+  /**
+   * Useful for implementing
+   * {@link Message#hasField(Descriptors.FieldDescriptor)}.
+   */
+  public boolean hasField(final FieldDescriptorType descriptor) {
+    if (descriptor.isRepeated()) {
+      throw new IllegalArgumentException(
+        "hasField() can only be called on non-repeated fields.");
+    }
+
+    return fields.get(descriptor) != null;
+  }
+
+  /**
+   * Useful for implementing
+   * {@link Message#getField(Descriptors.FieldDescriptor)}.  This method
+   * returns {@code null} if the field is not set; in this case it is up
+   * to the caller to fetch the field's default value.
+   */
+  public Object getField(final FieldDescriptorType descriptor) {
+    return fields.get(descriptor);
+  }
+
+  /**
+   * Useful for implementing
+   * {@link Message.Builder#setField(Descriptors.FieldDescriptor,Object)}.
+   */
+  @SuppressWarnings("unchecked")
+  public void setField(final FieldDescriptorType descriptor,
+                       Object value) {
+    if (descriptor.isRepeated()) {
+      if (!(value instanceof List)) {
+        throw new IllegalArgumentException(
+          "Wrong object type used with protocol message reflection.");
+      }
+
+      // Wrap the contents in a new list so that the caller cannot change
+      // the list's contents after setting it.
+      final List newList = new ArrayList();
+      newList.addAll((List)value);
+      for (final Object element : newList) {
+        verifyType(descriptor.getLiteType(), element);
+      }
+      value = newList;
+    } else {
+      verifyType(descriptor.getLiteType(), value);
+    }
+
+    fields.put(descriptor, value);
+  }
+
+  /**
+   * Useful for implementing
+   * {@link Message.Builder#clearField(Descriptors.FieldDescriptor)}.
+   */
+  public void clearField(final FieldDescriptorType descriptor) {
+    fields.remove(descriptor);
+  }
+
+  /**
+   * Useful for implementing
+   * {@link Message#getRepeatedFieldCount(Descriptors.FieldDescriptor)}.
+   */
+  public int getRepeatedFieldCount(final FieldDescriptorType descriptor) {
+    if (!descriptor.isRepeated()) {
+      throw new IllegalArgumentException(
+        "getRepeatedField() can only be called on repeated fields.");
+    }
+
+    final Object value = fields.get(descriptor);
+    if (value == null) {
+      return 0;
+    } else {
+      return ((List) value).size();
+    }
+  }
+
+  /**
+   * Useful for implementing
+   * {@link Message#getRepeatedField(Descriptors.FieldDescriptor,int)}.
+   */
+  public Object getRepeatedField(final FieldDescriptorType descriptor,
+                                 final int index) {
+    if (!descriptor.isRepeated()) {
+      throw new IllegalArgumentException(
+        "getRepeatedField() can only be called on repeated fields.");
+    }
+
+    final Object value = fields.get(descriptor);
+
+    if (value == null) {
+      throw new IndexOutOfBoundsException();
+    } else {
+      return ((List) value).get(index);
+    }
+  }
+
+  /**
+   * Useful for implementing
+   * {@link Message.Builder#setRepeatedField(Descriptors.FieldDescriptor,int,Object)}.
+   */
+  @SuppressWarnings("unchecked")
+  public void setRepeatedField(final FieldDescriptorType descriptor,
+                               final int index,
+                               final Object value) {
+    if (!descriptor.isRepeated()) {
+      throw new IllegalArgumentException(
+        "getRepeatedField() can only be called on repeated fields.");
+    }
+
+    final Object list = fields.get(descriptor);
+    if (list == null) {
+      throw new IndexOutOfBoundsException();
+    }
+
+    verifyType(descriptor.getLiteType(), value);
+    ((List) list).set(index, value);
+  }
+
+  /**
+   * Useful for implementing
+   * {@link Message.Builder#addRepeatedField(Descriptors.FieldDescriptor,Object)}.
+   */
+  @SuppressWarnings("unchecked")
+  public void addRepeatedField(final FieldDescriptorType descriptor,
+                               final Object value) {
+    if (!descriptor.isRepeated()) {
+      throw new IllegalArgumentException(
+        "addRepeatedField() can only be called on repeated fields.");
+    }
+
+    verifyType(descriptor.getLiteType(), value);
+
+    final Object existingValue = fields.get(descriptor);
+    List list;
+    if (existingValue == null) {
+      list = new ArrayList();
+      fields.put(descriptor, list);
+    } else {
+      list = (List) existingValue;
+    }
+
+    list.add(value);
+  }
+
+  /**
+   * Verifies that the given object is of the correct type to be a valid
+   * value for the given field.  (For repeated fields, this checks if the
+   * object is the right type to be one element of the field.)
+   *
+   * @throws IllegalArgumentException The value is not of the right type.
+   */
+  private static void verifyType(final WireFormat.FieldType type,
+                                 final Object value) {
+    if (value == null) {
+      throw new NullPointerException();
+    }
+
+    boolean isValid = false;
+    switch (type.getJavaType()) {
+      case INT:          isValid = value instanceof Integer   ; break;
+      case LONG:         isValid = value instanceof Long      ; break;
+      case FLOAT:        isValid = value instanceof Float     ; break;
+      case DOUBLE:       isValid = value instanceof Double    ; break;
+      case BOOLEAN:      isValid = value instanceof Boolean   ; break;
+      case STRING:       isValid = value instanceof String    ; break;
+      case BYTE_STRING:  isValid = value instanceof ByteString; break;
+      case ENUM:
+        // TODO(kenton):  Caller must do type checking here, I guess.
+        isValid = value instanceof Internal.EnumLite;
+        break;
+      case MESSAGE:
+        // TODO(kenton):  Caller must do type checking here, I guess.
+        isValid = value instanceof MessageLite;
+        break;
+    }
+
+    if (!isValid) {
+      // TODO(kenton):  When chaining calls to setField(), it can be hard to
+      //   tell from the stack trace which exact call failed, since the whole
+      //   chain is considered one line of code.  It would be nice to print
+      //   more information here, e.g. naming the field.  We used to do that.
+      //   But we can't now that FieldSet doesn't use descriptors.  Maybe this
+      //   isn't a big deal, though, since it would only really apply when using
+      //   reflection and generally people don't chain reflection setters.
+      throw new IllegalArgumentException(
+        "Wrong object type used with protocol message reflection.");
+    }
+  }
+
+  // =================================================================
+  // Parsing and serialization
+
+  /**
+   * See {@link Message#isInitialized()}.  Note:  Since {@code FieldSet}
+   * itself does not have any way of knowing about required fields that
+   * aren't actually present in the set, it is up to the caller to check
+   * that all required fields are present.
+   */
+  @SuppressWarnings("unchecked")
+  public boolean isInitialized() {
+    for (final Map.Entry<FieldDescriptorType, Object> entry:
+         fields.entrySet()) {
+      final FieldDescriptorType descriptor = entry.getKey();
+      if (descriptor.getLiteJavaType() == WireFormat.JavaType.MESSAGE) {
+        if (descriptor.isRepeated()) {
+          for (final MessageLite element:
+               (List<MessageLite>) entry.getValue()) {
+            if (!element.isInitialized()) {
+              return false;
+            }
+          }
+        } else {
+          if (!((MessageLite) entry.getValue()).isInitialized()) {
+            return false;
+          }
+        }
+      }
+    }
+
+    return true;
+  }
+
+  /**
+   * Given a field type, return the wire type.
+   *
+   * @returns One of the {@code WIRETYPE_} constants defined in
+   *          {@link WireFormat}.
+   */
+  static int getWireFormatForFieldType(final WireFormat.FieldType type,
+                                       boolean isPacked) {
+    if (isPacked) {
+      return WireFormat.WIRETYPE_LENGTH_DELIMITED;
+    } else {
+      return type.getWireType();
+    }
+  }
+
+  /**
+   * Like {@link #mergeFrom(Message)}, but merges from another {@link FieldSet}.
+   */
+  @SuppressWarnings("unchecked")
+  public void mergeFrom(final FieldSet<FieldDescriptorType> other) {
+    for (final Map.Entry<FieldDescriptorType, Object> entry:
+         other.fields.entrySet()) {
+      final FieldDescriptorType descriptor = entry.getKey();
+      final Object otherValue = entry.getValue();
+
+      if (descriptor.isRepeated()) {
+        Object value = fields.get(descriptor);
+        if (value == null) {
+          // Our list is empty, but we still need to make a defensive copy of
+          // the other list since we don't know if the other FieldSet is still
+          // mutable.
+          fields.put(descriptor, new ArrayList((List) otherValue));
+        } else {
+          // Concatenate the lists.
+          ((List) value).addAll((List) otherValue);
+        }
+      } else if (descriptor.getLiteJavaType() == WireFormat.JavaType.MESSAGE) {
+        Object value = fields.get(descriptor);
+        if (value == null) {
+          fields.put(descriptor, otherValue);
+        } else {
+          // Merge the messages.
+          fields.put(descriptor,
+              descriptor.internalMergeFrom(
+                ((MessageLite) value).toBuilder(), (MessageLite) otherValue)
+              .build());
+        }
+
+      } else {
+        fields.put(descriptor, otherValue);
+      }
+    }
+  }
+
+  // TODO(kenton):  Move static parsing and serialization methods into some
+  //   other class.  Probably WireFormat.
+
+  /**
+   * Read a field of any primitive type from a CodedInputStream.  Enums,
+   * groups, and embedded messages are not handled by this method.
+   *
+   * @param input The stream from which to read.
+   * @param type Declared type of the field.
+   * @return An object representing the field's value, of the exact
+   *         type which would be returned by
+   *         {@link Message#getField(Descriptors.FieldDescriptor)} for
+   *         this field.
+   */
+  public static Object readPrimitiveField(
+      CodedInputStream input,
+      final WireFormat.FieldType type) throws IOException {
+    switch (type) {
+      case DOUBLE  : return input.readDouble  ();
+      case FLOAT   : return input.readFloat   ();
+      case INT64   : return input.readInt64   ();
+      case UINT64  : return input.readUInt64  ();
+      case INT32   : return input.readInt32   ();
+      case FIXED64 : return input.readFixed64 ();
+      case FIXED32 : return input.readFixed32 ();
+      case BOOL    : return input.readBool    ();
+      case STRING  : return input.readString  ();
+      case BYTES   : return input.readBytes   ();
+      case UINT32  : return input.readUInt32  ();
+      case SFIXED32: return input.readSFixed32();
+      case SFIXED64: return input.readSFixed64();
+      case SINT32  : return input.readSInt32  ();
+      case SINT64  : return input.readSInt64  ();
+
+      case GROUP:
+        throw new IllegalArgumentException(
+          "readPrimitiveField() cannot handle nested groups.");
+      case MESSAGE:
+        throw new IllegalArgumentException(
+          "readPrimitiveField() cannot handle embedded messages.");
+      case ENUM:
+        // We don't handle enums because we don't know what to do if the
+        // value is not recognized.
+        throw new IllegalArgumentException(
+          "readPrimitiveField() cannot handle enums.");
+    }
+
+    throw new RuntimeException(
+      "There is no way to get here, but the compiler thinks otherwise.");
+  }
+
+  /** See {@link Message#writeTo(CodedOutputStream)}. */
+  public void writeTo(final CodedOutputStream output)
+                      throws IOException {
+    for (final Map.Entry<FieldDescriptorType, Object> entry:
+         fields.entrySet()) {
+      writeField(entry.getKey(), entry.getValue(), output);
+    }
+  }
+
+  /**
+   * Like {@link #writeTo} but uses MessageSet wire format.
+   */
+  public void writeMessageSetTo(final CodedOutputStream output)
+                                throws IOException {
+    for (final Map.Entry<FieldDescriptorType, Object> entry:
+         fields.entrySet()) {
+      final FieldDescriptorType descriptor = entry.getKey();
+      if (descriptor.getLiteJavaType() == WireFormat.JavaType.MESSAGE &&
+          !descriptor.isRepeated() && !descriptor.isPacked()) {
+        output.writeMessageSetExtension(entry.getKey().getNumber(),
+                                        (MessageLite) entry.getValue());
+      } else {
+        writeField(descriptor, entry.getValue(), output);
+      }
+    }
+  }
+
+  /**
+   * Write a single tag-value pair to the stream.
+   *
+   * @param output The output stream.
+   * @param type   The field's type.
+   * @param number The field's number.
+   * @param value  Object representing the field's value.  Must be of the exact
+   *               type which would be returned by
+   *               {@link Message#getField(Descriptors.FieldDescriptor)} for
+   *               this field.
+   */
+  private static void writeElement(final CodedOutputStream output,
+                                   final WireFormat.FieldType type,
+                                   final int number,
+                                   final Object value) throws IOException {
+    // Special case for groups, which need a start and end tag; other fields
+    // can just use writeTag() and writeFieldNoTag().
+    if (type == WireFormat.FieldType.GROUP) {
+      output.writeGroup(number, (MessageLite) value);
+    } else {
+      output.writeTag(number, getWireFormatForFieldType(type, false));
+      writeElementNoTag(output, type, value);
+    }
+  }
+
+  /**
+   * Write a field of arbitrary type, without its tag, to the stream.
+   *
+   * @param output The output stream.
+   * @param type The field's type.
+   * @param value  Object representing the field's value.  Must be of the exact
+   *               type which would be returned by
+   *               {@link Message#getField(Descriptors.FieldDescriptor)} for
+   *               this field.
+   */
+  private static void writeElementNoTag(
+      final CodedOutputStream output,
+      final WireFormat.FieldType type,
+      final Object value) throws IOException {
+    switch (type) {
+      case DOUBLE  : output.writeDoubleNoTag  ((Double     ) value); break;
+      case FLOAT   : output.writeFloatNoTag   ((Float      ) value); break;
+      case INT64   : output.writeInt64NoTag   ((Long       ) value); break;
+      case UINT64  : output.writeUInt64NoTag  ((Long       ) value); break;
+      case INT32   : output.writeInt32NoTag   ((Integer    ) value); break;
+      case FIXED64 : output.writeFixed64NoTag ((Long       ) value); break;
+      case FIXED32 : output.writeFixed32NoTag ((Integer    ) value); break;
+      case BOOL    : output.writeBoolNoTag    ((Boolean    ) value); break;
+      case STRING  : output.writeStringNoTag  ((String     ) value); break;
+      case GROUP   : output.writeGroupNoTag   ((MessageLite) value); break;
+      case MESSAGE : output.writeMessageNoTag ((MessageLite) value); break;
+      case BYTES   : output.writeBytesNoTag   ((ByteString ) value); break;
+      case UINT32  : output.writeUInt32NoTag  ((Integer    ) value); break;
+      case SFIXED32: output.writeSFixed32NoTag((Integer    ) value); break;
+      case SFIXED64: output.writeSFixed64NoTag((Long       ) value); break;
+      case SINT32  : output.writeSInt32NoTag  ((Integer    ) value); break;
+      case SINT64  : output.writeSInt64NoTag  ((Long       ) value); break;
+
+      case ENUM:
+        output.writeEnumNoTag(((Internal.EnumLite) value).getNumber());
+        break;
+    }
+  }
+
+  /** Write a single field. */
+  public static void writeField(final FieldDescriptorLite<?> descriptor,
+                                final Object value,
+                                final CodedOutputStream output)
+                                throws IOException {
+    WireFormat.FieldType type = descriptor.getLiteType();
+    int number = descriptor.getNumber();
+    if (descriptor.isRepeated()) {
+      final List valueList = (List)value;
+      if (descriptor.isPacked()) {
+        output.writeTag(number, WireFormat.WIRETYPE_LENGTH_DELIMITED);
+        // Compute the total data size so the length can be written.
+        int dataSize = 0;
+        for (final Object element : valueList) {
+          dataSize += computeElementSizeNoTag(type, element);
+        }
+        output.writeRawVarint32(dataSize);
+        // Write the data itself, without any tags.
+        for (final Object element : valueList) {
+          writeElementNoTag(output, type, element);
+        }
+      } else {
+        for (final Object element : valueList) {
+          writeElement(output, type, number, element);
+        }
+      }
+    } else {
+      writeElement(output, type, number, value);
+    }
+  }
+
+  /**
+   * See {@link Message#getSerializedSize()}.  It's up to the caller to cache
+   * the resulting size if desired.
+   */
+  public int getSerializedSize() {
+    int size = 0;
+    for (final Map.Entry<FieldDescriptorType, Object> entry:
+         fields.entrySet()) {
+      size += computeFieldSize(entry.getKey(), entry.getValue());
+    }
+    return size;
+  }
+
+  /**
+   * Like {@link #getSerializedSize} but uses MessageSet wire format.
+   */
+  public int getMessageSetSerializedSize() {
+    int size = 0;
+    for (final Map.Entry<FieldDescriptorType, Object> entry:
+         fields.entrySet()) {
+      final FieldDescriptorType descriptor = entry.getKey();
+      if (descriptor.getLiteJavaType() == WireFormat.JavaType.MESSAGE &&
+          !descriptor.isRepeated() && !descriptor.isPacked()) {
+        size += CodedOutputStream.computeMessageSetExtensionSize(
+                  entry.getKey().getNumber(), (MessageLite) entry.getValue());
+      } else {
+        size += computeFieldSize(descriptor, entry.getValue());
+      }
+    }
+    return size;
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * single tag/value pair of arbitrary type.
+   *
+   * @param type   The field's type.
+   * @param number The field's number.
+   * @param value  Object representing the field's value.  Must be of the exact
+   *               type which would be returned by
+   *               {@link Message#getField(Descriptors.FieldDescriptor)} for
+   *               this field.
+   */
+  private static int computeElementSize(
+      final WireFormat.FieldType type,
+      final int number, final Object value) {
+    int tagSize = CodedOutputStream.computeTagSize(number);
+    if (type == WireFormat.FieldType.GROUP) {
+      tagSize *= 2;
+    }
+    return tagSize + computeElementSizeNoTag(type, value);
+  }
+
+  /**
+   * Compute the number of bytes that would be needed to encode a
+   * particular value of arbitrary type, excluding tag.
+   *
+   * @param type   The field's type.
+   * @param value  Object representing the field's value.  Must be of the exact
+   *               type which would be returned by
+   *               {@link Message#getField(Descriptors.FieldDescriptor)} for
+   *               this field.
+   */
+  private static int computeElementSizeNoTag(
+      final WireFormat.FieldType type, final Object value) {
+    switch (type) {
+      // Note:  Minor violation of 80-char limit rule here because this would
+      //   actually be harder to read if we wrapped the lines.
+      case DOUBLE  : return CodedOutputStream.computeDoubleSizeNoTag  ((Double     )value);
+      case FLOAT   : return CodedOutputStream.computeFloatSizeNoTag   ((Float      )value);
+      case INT64   : return CodedOutputStream.computeInt64SizeNoTag   ((Long       )value);
+      case UINT64  : return CodedOutputStream.computeUInt64SizeNoTag  ((Long       )value);
+      case INT32   : return CodedOutputStream.computeInt32SizeNoTag   ((Integer    )value);
+      case FIXED64 : return CodedOutputStream.computeFixed64SizeNoTag ((Long       )value);
+      case FIXED32 : return CodedOutputStream.computeFixed32SizeNoTag ((Integer    )value);
+      case BOOL    : return CodedOutputStream.computeBoolSizeNoTag    ((Boolean    )value);
+      case STRING  : return CodedOutputStream.computeStringSizeNoTag  ((String     )value);
+      case GROUP   : return CodedOutputStream.computeGroupSizeNoTag   ((MessageLite)value);
+      case MESSAGE : return CodedOutputStream.computeMessageSizeNoTag ((MessageLite)value);
+      case BYTES   : return CodedOutputStream.computeBytesSizeNoTag   ((ByteString )value);
+      case UINT32  : return CodedOutputStream.computeUInt32SizeNoTag  ((Integer    )value);
+      case SFIXED32: return CodedOutputStream.computeSFixed32SizeNoTag((Integer    )value);
+      case SFIXED64: return CodedOutputStream.computeSFixed64SizeNoTag((Long       )value);
+      case SINT32  : return CodedOutputStream.computeSInt32SizeNoTag  ((Integer    )value);
+      case SINT64  : return CodedOutputStream.computeSInt64SizeNoTag  ((Long       )value);
+
+      case ENUM:
+        return CodedOutputStream.computeEnumSizeNoTag(
+            ((Internal.EnumLite) value).getNumber());
+    }
+
+    throw new RuntimeException(
+      "There is no way to get here, but the compiler thinks otherwise.");
+  }
+
+  /**
+   * Compute the number of bytes needed to encode a particular field.
+   */
+  public static int computeFieldSize(final FieldDescriptorLite<?> descriptor,
+                                     final Object value) {
+    WireFormat.FieldType type = descriptor.getLiteType();
+    int number = descriptor.getNumber();
+    if (descriptor.isRepeated()) {
+      if (descriptor.isPacked()) {
+        int dataSize = 0;
+        for (final Object element : (List)value) {
+          dataSize += computeElementSizeNoTag(type, element);
+        }
+        return dataSize +
+            CodedOutputStream.computeTagSize(number) +
+            CodedOutputStream.computeRawVarint32Size(dataSize);
+      } else {
+        int size = 0;
+        for (final Object element : (List)value) {
+          size += computeElementSize(type, number, element);
+        }
+        return size;
+      }
+    } else {
+      return computeElementSize(type, number, value);
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/GeneratedMessage.java b/java/src/main/java/com/google/protobuf/GeneratedMessage.java
new file mode 100644
index 0000000..4994faa
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/GeneratedMessage.java
@@ -0,0 +1,1318 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.EnumValueDescriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+import java.io.IOException;
+import java.lang.reflect.Method;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * All generated protocol message classes extend this class.  This class
+ * implements most of the Message and Builder interfaces using Java reflection.
+ * Users can ignore this class and pretend that generated messages implement
+ * the Message interface directly.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public abstract class GeneratedMessage extends AbstractMessage {
+  protected GeneratedMessage() {}
+
+  private UnknownFieldSet unknownFields = UnknownFieldSet.getDefaultInstance();
+
+  /**
+   * Get the FieldAccessorTable for this type.  We can't have the message
+   * class pass this in to the constructor because of bootstrapping trouble
+   * with DescriptorProtos.
+   */
+  protected abstract FieldAccessorTable internalGetFieldAccessorTable();
+
+  public Descriptor getDescriptorForType() {
+    return internalGetFieldAccessorTable().descriptor;
+  }
+
+  /** Internal helper which returns a mutable map. */
+  private Map<FieldDescriptor, Object> getAllFieldsMutable() {
+    final TreeMap<FieldDescriptor, Object> result =
+      new TreeMap<FieldDescriptor, Object>();
+    final Descriptor descriptor = internalGetFieldAccessorTable().descriptor;
+    for (final FieldDescriptor field : descriptor.getFields()) {
+      if (field.isRepeated()) {
+        final List value = (List) getField(field);
+        if (!value.isEmpty()) {
+          result.put(field, value);
+        }
+      } else {
+        if (hasField(field)) {
+          result.put(field, getField(field));
+        }
+      }
+    }
+    return result;
+  }
+
+  @Override
+  public boolean isInitialized() {
+    for (final FieldDescriptor field : getDescriptorForType().getFields()) {
+      // Check that all required fields are present.
+      if (field.isRequired()) {
+        if (!hasField(field)) {
+          return false;
+        }
+      }
+      // Check that embedded messages are initialized.
+      if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+        if (field.isRepeated()) {
+          @SuppressWarnings("unchecked") final
+          List<Message> messageList = (List<Message>) getField(field);
+          for (final Message element : messageList) {
+            if (!element.isInitialized()) {
+              return false;
+            }
+          }
+        } else {
+          if (hasField(field) && !((Message) getField(field)).isInitialized()) {
+            return false;
+          }
+        }
+      }
+    }
+
+    return true;
+  }
+
+  public Map<FieldDescriptor, Object> getAllFields() {
+    return Collections.unmodifiableMap(getAllFieldsMutable());
+  }
+
+  public boolean hasField(final FieldDescriptor field) {
+    return internalGetFieldAccessorTable().getField(field).has(this);
+  }
+
+  public Object getField(final FieldDescriptor field) {
+    return internalGetFieldAccessorTable().getField(field).get(this);
+  }
+
+  public int getRepeatedFieldCount(final FieldDescriptor field) {
+    return internalGetFieldAccessorTable().getField(field)
+      .getRepeatedCount(this);
+  }
+
+  public Object getRepeatedField(final FieldDescriptor field, final int index) {
+    return internalGetFieldAccessorTable().getField(field)
+      .getRepeated(this, index);
+  }
+
+  public final UnknownFieldSet getUnknownFields() {
+    return unknownFields;
+  }
+
+  @SuppressWarnings("unchecked")
+  public abstract static class Builder <BuilderType extends Builder>
+      extends AbstractMessage.Builder<BuilderType> {
+    protected Builder() {}
+
+    // This is implemented here only to work around an apparent bug in the
+    // Java compiler and/or build system.  See bug #1898463.  The mere presence
+    // of this dummy clone() implementation makes it go away.
+    @Override
+    public BuilderType clone() {
+      throw new UnsupportedOperationException(
+          "This is supposed to be overridden by subclasses.");
+    }
+
+    /**
+     * Get the message being built.  We don't just pass this to the
+     * constructor because it becomes null when build() is called.
+     */
+    protected abstract GeneratedMessage internalGetResult();
+
+    /**
+     * Get the FieldAccessorTable for this type.  We can't have the message
+     * class pass this in to the constructor because of bootstrapping trouble
+     * with DescriptorProtos.
+     */
+    private FieldAccessorTable internalGetFieldAccessorTable() {
+      return internalGetResult().internalGetFieldAccessorTable();
+    }
+
+    public Descriptor getDescriptorForType() {
+      return internalGetFieldAccessorTable().descriptor;
+    }
+
+    public Map<FieldDescriptor, Object> getAllFields() {
+      return internalGetResult().getAllFields();
+    }
+
+    public Message.Builder newBuilderForField(
+        final FieldDescriptor field) {
+      return internalGetFieldAccessorTable().getField(field).newBuilder();
+    }
+
+    public boolean hasField(final FieldDescriptor field) {
+      return internalGetResult().hasField(field);
+    }
+
+    public Object getField(final FieldDescriptor field) {
+      if (field.isRepeated()) {
+        // The underlying list object is still modifiable at this point.
+        // Make sure not to expose the modifiable list to the caller.
+        return Collections.unmodifiableList(
+          (List) internalGetResult().getField(field));
+      } else {
+        return internalGetResult().getField(field);
+      }
+    }
+
+    public BuilderType setField(final FieldDescriptor field,
+                                final Object value) {
+      internalGetFieldAccessorTable().getField(field).set(this, value);
+      return (BuilderType) this;
+    }
+
+    public BuilderType clearField(final FieldDescriptor field) {
+      internalGetFieldAccessorTable().getField(field).clear(this);
+      return (BuilderType) this;
+    }
+
+    public int getRepeatedFieldCount(final FieldDescriptor field) {
+      return internalGetResult().getRepeatedFieldCount(field);
+    }
+
+    public Object getRepeatedField(final FieldDescriptor field,
+                                   final int index) {
+      return internalGetResult().getRepeatedField(field, index);
+    }
+
+    public BuilderType setRepeatedField(final FieldDescriptor field,
+                                        final int index, final Object value) {
+      internalGetFieldAccessorTable().getField(field)
+        .setRepeated(this, index, value);
+      return (BuilderType) this;
+    }
+
+    public BuilderType addRepeatedField(final FieldDescriptor field,
+                                        final Object value) {
+      internalGetFieldAccessorTable().getField(field).addRepeated(this, value);
+      return (BuilderType) this;
+    }
+
+    public final UnknownFieldSet getUnknownFields() {
+      return internalGetResult().unknownFields;
+    }
+
+    public final BuilderType setUnknownFields(
+        final UnknownFieldSet unknownFields) {
+      internalGetResult().unknownFields = unknownFields;
+      return (BuilderType) this;
+    }
+
+    @Override
+    public final BuilderType mergeUnknownFields(
+        final UnknownFieldSet unknownFields) {
+      final GeneratedMessage result = internalGetResult();
+      result.unknownFields =
+        UnknownFieldSet.newBuilder(result.unknownFields)
+                       .mergeFrom(unknownFields)
+                       .build();
+      return (BuilderType) this;
+    }
+
+    public boolean isInitialized() {
+      return internalGetResult().isInitialized();
+    }
+
+    /**
+     * Called by subclasses to parse an unknown field.
+     * @return {@code true} unless the tag is an end-group tag.
+     */
+    protected boolean parseUnknownField(
+        final CodedInputStream input,
+        final UnknownFieldSet.Builder unknownFields,
+        final ExtensionRegistryLite extensionRegistry,
+        final int tag) throws IOException {
+      return unknownFields.mergeFieldFrom(tag, input);
+    }
+  }
+
+  // =================================================================
+  // Extensions-related stuff
+
+  /**
+   * Generated message classes for message types that contain extension ranges
+   * subclass this.
+   *
+   * <p>This class implements type-safe accessors for extensions.  They
+   * implement all the same operations that you can do with normal fields --
+   * e.g. "has", "get", and "getCount" -- but for extensions.  The extensions
+   * are identified using instances of the class {@link GeneratedExtension};
+   * the protocol compiler generates a static instance of this class for every
+   * extension in its input.  Through the magic of generics, all is made
+   * type-safe.
+   *
+   * <p>For example, imagine you have the {@code .proto} file:
+   *
+   * <pre>
+   * option java_class = "MyProto";
+   *
+   * message Foo {
+   *   extensions 1000 to max;
+   * }
+   *
+   * extend Foo {
+   *   optional int32 bar;
+   * }
+   * </pre>
+   *
+   * <p>Then you might write code like:
+   *
+   * <pre>
+   * MyProto.Foo foo = getFoo();
+   * int i = foo.getExtension(MyProto.bar);
+   * </pre>
+   *
+   * <p>See also {@link ExtendableBuilder}.
+   */
+  public abstract static class ExtendableMessage<
+        MessageType extends ExtendableMessage>
+      extends GeneratedMessage {
+    protected ExtendableMessage() {}
+    private final FieldSet<FieldDescriptor> extensions = FieldSet.newFieldSet();
+
+    private void verifyExtensionContainingType(
+        final GeneratedExtension<MessageType, ?> extension) {
+      if (extension.getDescriptor().getContainingType() !=
+          getDescriptorForType()) {
+        // This can only happen if someone uses unchecked operations.
+        throw new IllegalArgumentException(
+          "Extension is for type \"" +
+          extension.getDescriptor().getContainingType().getFullName() +
+          "\" which does not match message type \"" +
+          getDescriptorForType().getFullName() + "\".");
+      }
+    }
+
+    /** Check if a singular extension is present. */
+    public final boolean hasExtension(
+        final GeneratedExtension<MessageType, ?> extension) {
+      verifyExtensionContainingType(extension);
+      return extensions.hasField(extension.getDescriptor());
+    }
+
+    /** Get the number of elements in a repeated extension. */
+    public final <Type> int getExtensionCount(
+        final GeneratedExtension<MessageType, List<Type>> extension) {
+      verifyExtensionContainingType(extension);
+      final FieldDescriptor descriptor = extension.getDescriptor();
+      return extensions.getRepeatedFieldCount(descriptor);
+    }
+
+    /** Get the value of an extension. */
+    @SuppressWarnings("unchecked")
+    public final <Type> Type getExtension(
+        final GeneratedExtension<MessageType, Type> extension) {
+      verifyExtensionContainingType(extension);
+      FieldDescriptor descriptor = extension.getDescriptor();
+      final Object value = extensions.getField(descriptor);
+      if (value == null) {
+        if (descriptor.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+          return (Type) extension.getMessageDefaultInstance();
+        } else {
+          return (Type) extension.fromReflectionType(
+              descriptor.getDefaultValue());
+        }
+      } else {
+        return (Type) extension.fromReflectionType(value);
+      }
+    }
+
+    /** Get one element of a repeated extension. */
+    @SuppressWarnings("unchecked")
+    public final <Type> Type getExtension(
+        final GeneratedExtension<MessageType, List<Type>> extension,
+        final int index) {
+      verifyExtensionContainingType(extension);
+      FieldDescriptor descriptor = extension.getDescriptor();
+      return (Type) extension.singularFromReflectionType(
+          extensions.getRepeatedField(descriptor, index));
+    }
+
+    /** Called by subclasses to check if all extensions are initialized. */
+    protected boolean extensionsAreInitialized() {
+      return extensions.isInitialized();
+    }
+
+    @Override
+    public boolean isInitialized() {
+      return super.isInitialized() && extensionsAreInitialized();
+    }
+
+    /**
+     * Used by subclasses to serialize extensions.  Extension ranges may be
+     * interleaved with field numbers, but we must write them in canonical
+     * (sorted by field number) order.  ExtensionWriter helps us write
+     * individual ranges of extensions at once.
+     */
+    protected class ExtensionWriter {
+      // Imagine how much simpler this code would be if Java iterators had
+      // a way to get the next element without advancing the iterator.
+
+      private final Iterator<Map.Entry<FieldDescriptor, Object>> iter =
+        extensions.iterator();
+      private Map.Entry<FieldDescriptor, Object> next;
+      private final boolean messageSetWireFormat;
+
+      private ExtensionWriter(final boolean messageSetWireFormat) {
+        if (iter.hasNext()) {
+          next = iter.next();
+        }
+        this.messageSetWireFormat = messageSetWireFormat;
+      }
+
+      public void writeUntil(final int end, final CodedOutputStream output)
+                             throws IOException {
+        while (next != null && next.getKey().getNumber() < end) {
+          FieldDescriptor descriptor = next.getKey();
+          if (messageSetWireFormat && descriptor.getLiteJavaType() ==
+                  WireFormat.JavaType.MESSAGE &&
+              !descriptor.isRepeated()) {
+            output.writeMessageSetExtension(descriptor.getNumber(),
+                                            (Message) next.getValue());
+          } else {
+            FieldSet.writeField(descriptor, next.getValue(), output);
+          }
+          if (iter.hasNext()) {
+            next = iter.next();
+          } else {
+            next = null;
+          }
+        }
+      }
+    }
+
+    protected ExtensionWriter newExtensionWriter() {
+      return new ExtensionWriter(false);
+    }
+    protected ExtensionWriter newMessageSetExtensionWriter() {
+      return new ExtensionWriter(true);
+    }
+
+    /** Called by subclasses to compute the size of extensions. */
+    protected int extensionsSerializedSize() {
+      return extensions.getSerializedSize();
+    }
+    protected int extensionsSerializedSizeAsMessageSet() {
+      return extensions.getMessageSetSerializedSize();
+    }
+
+    // ---------------------------------------------------------------
+    // Reflection
+
+    @Override
+    public Map<FieldDescriptor, Object> getAllFields() {
+      final Map<FieldDescriptor, Object> result = super.getAllFieldsMutable();
+      result.putAll(extensions.getAllFields());
+      return Collections.unmodifiableMap(result);
+    }
+
+    @Override
+    public boolean hasField(final FieldDescriptor field) {
+      if (field.isExtension()) {
+        verifyContainingType(field);
+        return extensions.hasField(field);
+      } else {
+        return super.hasField(field);
+      }
+    }
+
+    @Override
+    public Object getField(final FieldDescriptor field) {
+      if (field.isExtension()) {
+        verifyContainingType(field);
+        final Object value = extensions.getField(field);
+        if (value == null) {
+          if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+            // Lacking an ExtensionRegistry, we have no way to determine the
+            // extension's real type, so we return a DynamicMessage.
+            return DynamicMessage.getDefaultInstance(field.getMessageType());
+          } else {
+            return field.getDefaultValue();
+          }
+        } else {
+          return value;
+        }
+      } else {
+        return super.getField(field);
+      }
+    }
+
+    @Override
+    public int getRepeatedFieldCount(final FieldDescriptor field) {
+      if (field.isExtension()) {
+        verifyContainingType(field);
+        return extensions.getRepeatedFieldCount(field);
+      } else {
+        return super.getRepeatedFieldCount(field);
+      }
+    }
+
+    @Override
+    public Object getRepeatedField(final FieldDescriptor field,
+                                   final int index) {
+      if (field.isExtension()) {
+        verifyContainingType(field);
+        return extensions.getRepeatedField(field, index);
+      } else {
+        return super.getRepeatedField(field, index);
+      }
+    }
+
+    private void verifyContainingType(final FieldDescriptor field) {
+      if (field.getContainingType() != getDescriptorForType()) {
+        throw new IllegalArgumentException(
+          "FieldDescriptor does not match message type.");
+      }
+    }
+  }
+
+  /**
+   * Generated message builders for message types that contain extension ranges
+   * subclass this.
+   *
+   * <p>This class implements type-safe accessors for extensions.  They
+   * implement all the same operations that you can do with normal fields --
+   * e.g. "get", "set", and "add" -- but for extensions.  The extensions are
+   * identified using instances of the class {@link GeneratedExtension}; the
+   * protocol compiler generates a static instance of this class for every
+   * extension in its input.  Through the magic of generics, all is made
+   * type-safe.
+   *
+   * <p>For example, imagine you have the {@code .proto} file:
+   *
+   * <pre>
+   * option java_class = "MyProto";
+   *
+   * message Foo {
+   *   extensions 1000 to max;
+   * }
+   *
+   * extend Foo {
+   *   optional int32 bar;
+   * }
+   * </pre>
+   *
+   * <p>Then you might write code like:
+   *
+   * <pre>
+   * MyProto.Foo foo =
+   *   MyProto.Foo.newBuilder()
+   *     .setExtension(MyProto.bar, 123)
+   *     .build();
+   * </pre>
+   *
+   * <p>See also {@link ExtendableMessage}.
+   */
+  @SuppressWarnings("unchecked")
+  public abstract static class ExtendableBuilder<
+        MessageType extends ExtendableMessage,
+        BuilderType extends ExtendableBuilder>
+      extends Builder<BuilderType> {
+    protected ExtendableBuilder() {}
+
+    // This is implemented here only to work around an apparent bug in the
+    // Java compiler and/or build system.  See bug #1898463.  The mere presence
+    // of this dummy clone() implementation makes it go away.
+    @Override
+    public BuilderType clone() {
+      throw new UnsupportedOperationException(
+          "This is supposed to be overridden by subclasses.");
+    }
+
+    @Override
+    protected abstract ExtendableMessage<MessageType> internalGetResult();
+
+    /** Check if a singular extension is present. */
+    public final boolean hasExtension(
+        final GeneratedExtension<MessageType, ?> extension) {
+      return internalGetResult().hasExtension(extension);
+    }
+
+    /** Get the number of elements in a repeated extension. */
+    public final <Type> int getExtensionCount(
+        final GeneratedExtension<MessageType, List<Type>> extension) {
+      return internalGetResult().getExtensionCount(extension);
+    }
+
+    /** Get the value of an extension. */
+    public final <Type> Type getExtension(
+        final GeneratedExtension<MessageType, Type> extension) {
+      return internalGetResult().getExtension(extension);
+    }
+
+    /** Get one element of a repeated extension. */
+    public final <Type> Type getExtension(
+        final GeneratedExtension<MessageType, List<Type>> extension,
+        final int index) {
+      return internalGetResult().getExtension(extension, index);
+    }
+
+    /** Set the value of an extension. */
+    public final <Type> BuilderType setExtension(
+        final GeneratedExtension<MessageType, Type> extension,
+        final Type value) {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      message.verifyExtensionContainingType(extension);
+      final FieldDescriptor descriptor = extension.getDescriptor();
+      message.extensions.setField(descriptor,
+                                  extension.toReflectionType(value));
+      return (BuilderType) this;
+    }
+
+    /** Set the value of one element of a repeated extension. */
+    public final <Type> BuilderType setExtension(
+        final GeneratedExtension<MessageType, List<Type>> extension,
+        final int index, final Type value) {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      message.verifyExtensionContainingType(extension);
+      final FieldDescriptor descriptor = extension.getDescriptor();
+      message.extensions.setRepeatedField(
+        descriptor, index,
+        extension.singularToReflectionType(value));
+      return (BuilderType) this;
+    }
+
+    /** Append a value to a repeated extension. */
+    public final <Type> BuilderType addExtension(
+        final GeneratedExtension<MessageType, List<Type>> extension,
+        final Type value) {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      message.verifyExtensionContainingType(extension);
+      final FieldDescriptor descriptor = extension.getDescriptor();
+      message.extensions.addRepeatedField(
+          descriptor, extension.singularToReflectionType(value));
+      return (BuilderType) this;
+    }
+
+    /** Clear an extension. */
+    public final <Type> BuilderType clearExtension(
+        final GeneratedExtension<MessageType, ?> extension) {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      message.verifyExtensionContainingType(extension);
+      message.extensions.clearField(extension.getDescriptor());
+      return (BuilderType) this;
+    }
+
+    /**
+     * Called by subclasses to parse an unknown field or an extension.
+     * @return {@code true} unless the tag is an end-group tag.
+     */
+    @Override
+    protected boolean parseUnknownField(
+        final CodedInputStream input,
+        final UnknownFieldSet.Builder unknownFields,
+        final ExtensionRegistryLite extensionRegistry,
+        final int tag) throws IOException {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      return AbstractMessage.Builder.mergeFieldFrom(
+        input, unknownFields, extensionRegistry, this, tag);
+    }
+
+    // ---------------------------------------------------------------
+    // Reflection
+
+    // We don't have to override the get*() methods here because they already
+    // just forward to the underlying message.
+
+    @Override
+    public BuilderType setField(final FieldDescriptor field,
+                                final Object value) {
+      if (field.isExtension()) {
+        final ExtendableMessage<MessageType> message = internalGetResult();
+        message.verifyContainingType(field);
+        message.extensions.setField(field, value);
+        return (BuilderType) this;
+      } else {
+        return super.setField(field, value);
+      }
+    }
+
+    @Override
+    public BuilderType clearField(final FieldDescriptor field) {
+      if (field.isExtension()) {
+        final ExtendableMessage<MessageType> message = internalGetResult();
+        message.verifyContainingType(field);
+        message.extensions.clearField(field);
+        return (BuilderType) this;
+      } else {
+        return super.clearField(field);
+      }
+    }
+
+    @Override
+    public BuilderType setRepeatedField(final FieldDescriptor field,
+                                        final int index, final Object value) {
+      if (field.isExtension()) {
+        final ExtendableMessage<MessageType> message = internalGetResult();
+        message.verifyContainingType(field);
+        message.extensions.setRepeatedField(field, index, value);
+        return (BuilderType) this;
+      } else {
+        return super.setRepeatedField(field, index, value);
+      }
+    }
+
+    @Override
+    public BuilderType addRepeatedField(final FieldDescriptor field,
+                                        final Object value) {
+      if (field.isExtension()) {
+        final ExtendableMessage<MessageType> message = internalGetResult();
+        message.verifyContainingType(field);
+        message.extensions.addRepeatedField(field, value);
+        return (BuilderType) this;
+      } else {
+        return super.addRepeatedField(field, value);
+      }
+    }
+
+    protected final void mergeExtensionFields(final ExtendableMessage other) {
+      internalGetResult().extensions.mergeFrom(other.extensions);
+    }
+  }
+
+  // -----------------------------------------------------------------
+
+  /** For use by generated code only. */
+  public static <ContainingType extends Message, Type>
+      GeneratedExtension<ContainingType, Type>
+      newGeneratedExtension(final FieldDescriptor descriptor,
+                            final Class<Type> type) {
+    if (descriptor.isRepeated()) {
+      throw new IllegalArgumentException(
+        "Must call newRepeatedGeneratedExtension() for repeated types.");
+    }
+    return new GeneratedExtension<ContainingType, Type>(descriptor, type);
+  }
+
+  /** For use by generated code only. */
+  public static <ContainingType extends Message, Type>
+      GeneratedExtension<ContainingType, List<Type>>
+      newRepeatedGeneratedExtension(
+        final FieldDescriptor descriptor, final Class<Type> type) {
+    if (!descriptor.isRepeated()) {
+      throw new IllegalArgumentException(
+        "Must call newGeneratedExtension() for non-repeated types.");
+    }
+    return new GeneratedExtension<ContainingType, List<Type>>(descriptor, type);
+  }
+
+  /**
+   * Type used to represent generated extensions.  The protocol compiler
+   * generates a static singleton instance of this class for each extension.
+   *
+   * <p>For example, imagine you have the {@code .proto} file:
+   *
+   * <pre>
+   * option java_class = "MyProto";
+   *
+   * message Foo {
+   *   extensions 1000 to max;
+   * }
+   *
+   * extend Foo {
+   *   optional int32 bar;
+   * }
+   * </pre>
+   *
+   * <p>Then, {@code MyProto.Foo.bar} has type
+   * {@code GeneratedExtension<MyProto.Foo, Integer>}.
+   *
+   * <p>In general, users should ignore the details of this type, and simply use
+   * these static singletons as parameters to the extension accessors defined
+   * in {@link ExtendableMessage} and {@link ExtendableBuilder}.
+   */
+  public static final class GeneratedExtension<
+      ContainingType extends Message, Type> {
+    // TODO(kenton):  Find ways to avoid using Java reflection within this
+    //   class.  Also try to avoid suppressing unchecked warnings.
+
+    private GeneratedExtension(final FieldDescriptor descriptor,
+                               final Class type) {
+      if (!descriptor.isExtension()) {
+        throw new IllegalArgumentException(
+          "GeneratedExtension given a regular (non-extension) field.");
+      }
+
+      this.descriptor = descriptor;
+      this.type = type;
+
+      switch (descriptor.getJavaType()) {
+        case MESSAGE:
+          enumValueOf = null;
+          enumGetValueDescriptor = null;
+          messageDefaultInstance =
+            (Message) invokeOrDie(getMethodOrDie(type, "getDefaultInstance"),
+                                  null);
+          break;
+        case ENUM:
+          enumValueOf = getMethodOrDie(type, "valueOf",
+                                       EnumValueDescriptor.class);
+          enumGetValueDescriptor = getMethodOrDie(type, "getValueDescriptor");
+          messageDefaultInstance = null;
+          break;
+        default:
+          enumValueOf = null;
+          enumGetValueDescriptor = null;
+          messageDefaultInstance = null;
+          break;
+      }
+    }
+
+    private final FieldDescriptor descriptor;
+    private final Class type;
+    private final Method enumValueOf;
+    private final Method enumGetValueDescriptor;
+    private final Message messageDefaultInstance;
+
+    public FieldDescriptor getDescriptor() { return descriptor; }
+
+    /**
+     * If the extension is an embedded message or group, returns the default
+     * instance of the message.
+     */
+    @SuppressWarnings("unchecked")
+    public Message getMessageDefaultInstance() {
+      return messageDefaultInstance;
+    }
+
+    /**
+     * Convert from the type used by the reflection accessors to the type used
+     * by native accessors.  E.g., for enums, the reflection accessors use
+     * EnumValueDescriptors but the native accessors use the generated enum
+     * type.
+     */
+    @SuppressWarnings("unchecked")
+    private Object fromReflectionType(final Object value) {
+      if (descriptor.isRepeated()) {
+        if (descriptor.getJavaType() == FieldDescriptor.JavaType.MESSAGE ||
+            descriptor.getJavaType() == FieldDescriptor.JavaType.ENUM) {
+          // Must convert the whole list.
+          final List result = new ArrayList();
+          for (final Object element : (List) value) {
+            result.add(singularFromReflectionType(element));
+          }
+          return result;
+        } else {
+          return value;
+        }
+      } else {
+        return singularFromReflectionType(value);
+      }
+    }
+
+    /**
+     * Like {@link #fromReflectionType(Object)}, but if the type is a repeated
+     * type, this converts a single element.
+     */
+    private Object singularFromReflectionType(final Object value) {
+      switch (descriptor.getJavaType()) {
+        case MESSAGE:
+          if (type.isInstance(value)) {
+            return value;
+          } else {
+            // It seems the copy of the embedded message stored inside the
+            // extended message is not of the exact type the user was
+            // expecting.  This can happen if a user defines a
+            // GeneratedExtension manually and gives it a different type.
+            // This should not happen in normal use.  But, to be nice, we'll
+            // copy the message to whatever type the caller was expecting.
+            return messageDefaultInstance.newBuilderForType()
+                           .mergeFrom((Message) value).build();
+          }
+        case ENUM:
+          return invokeOrDie(enumValueOf, null, (EnumValueDescriptor) value);
+        default:
+          return value;
+      }
+    }
+
+    /**
+     * Convert from the type used by the native accessors to the type used
+     * by reflection accessors.  E.g., for enums, the reflection accessors use
+     * EnumValueDescriptors but the native accessors use the generated enum
+     * type.
+     */
+    @SuppressWarnings("unchecked")
+    private Object toReflectionType(final Object value) {
+      if (descriptor.isRepeated()) {
+        if (descriptor.getJavaType() == FieldDescriptor.JavaType.ENUM) {
+          // Must convert the whole list.
+          final List result = new ArrayList();
+          for (final Object element : (List) value) {
+            result.add(singularToReflectionType(element));
+          }
+          return result;
+        } else {
+          return value;
+        }
+      } else {
+        return singularToReflectionType(value);
+      }
+    }
+
+    /**
+     * Like {@link #toReflectionType(Object)}, but if the type is a repeated
+     * type, this converts a single element.
+     */
+    private Object singularToReflectionType(final Object value) {
+      switch (descriptor.getJavaType()) {
+        case ENUM:
+          return invokeOrDie(enumGetValueDescriptor, value);
+        default:
+          return value;
+      }
+    }
+  }
+
+  // =================================================================
+
+  /** Calls Class.getMethod and throws a RuntimeException if it fails. */
+  @SuppressWarnings("unchecked")
+  private static Method getMethodOrDie(
+      final Class clazz, final String name, final Class... params) {
+    try {
+      return clazz.getMethod(name, params);
+    } catch (NoSuchMethodException e) {
+      throw new RuntimeException(
+        "Generated message class \"" + clazz.getName() +
+        "\" missing method \"" + name + "\".", e);
+    }
+  }
+
+  /** Calls invoke and throws a RuntimeException if it fails. */
+  private static Object invokeOrDie(
+      final Method method, final Object object, final Object... params) {
+    try {
+      return method.invoke(object, params);
+    } catch (IllegalAccessException e) {
+      throw new RuntimeException(
+        "Couldn't use Java reflection to implement protocol message " +
+        "reflection.", e);
+    } catch (InvocationTargetException e) {
+      final Throwable cause = e.getCause();
+      if (cause instanceof RuntimeException) {
+        throw (RuntimeException) cause;
+      } else if (cause instanceof Error) {
+        throw (Error) cause;
+      } else {
+        throw new RuntimeException(
+          "Unexpected exception thrown by generated accessor method.", cause);
+      }
+    }
+  }
+
+  /**
+   * Users should ignore this class.  This class provides the implementation
+   * with access to the fields of a message object using Java reflection.
+   */
+  public static final class FieldAccessorTable {
+
+    /**
+     * Construct a FieldAccessorTable for a particular message class.  Only
+     * one FieldAccessorTable should ever be constructed per class.
+     *
+     * @param descriptor     The type's descriptor.
+     * @param camelCaseNames The camelcase names of all fields in the message.
+     *                       These are used to derive the accessor method names.
+     * @param messageClass   The message type.
+     * @param builderClass   The builder type.
+     */
+    public FieldAccessorTable(
+        final Descriptor descriptor,
+        final String[] camelCaseNames,
+        final Class<? extends GeneratedMessage> messageClass,
+        final Class<? extends Builder> builderClass) {
+      this.descriptor = descriptor;
+      fields = new FieldAccessor[descriptor.getFields().size()];
+
+      for (int i = 0; i < fields.length; i++) {
+        final FieldDescriptor field = descriptor.getFields().get(i);
+        if (field.isRepeated()) {
+          if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+            fields[i] = new RepeatedMessageFieldAccessor(
+              field, camelCaseNames[i], messageClass, builderClass);
+          } else if (field.getJavaType() == FieldDescriptor.JavaType.ENUM) {
+            fields[i] = new RepeatedEnumFieldAccessor(
+              field, camelCaseNames[i], messageClass, builderClass);
+          } else {
+            fields[i] = new RepeatedFieldAccessor(
+              field, camelCaseNames[i], messageClass, builderClass);
+          }
+        } else {
+          if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+            fields[i] = new SingularMessageFieldAccessor(
+              field, camelCaseNames[i], messageClass, builderClass);
+          } else if (field.getJavaType() == FieldDescriptor.JavaType.ENUM) {
+            fields[i] = new SingularEnumFieldAccessor(
+              field, camelCaseNames[i], messageClass, builderClass);
+          } else {
+            fields[i] = new SingularFieldAccessor(
+              field, camelCaseNames[i], messageClass, builderClass);
+          }
+        }
+      }
+    }
+
+    private final Descriptor descriptor;
+    private final FieldAccessor[] fields;
+
+    /** Get the FieldAccessor for a particular field. */
+    private FieldAccessor getField(final FieldDescriptor field) {
+      if (field.getContainingType() != descriptor) {
+        throw new IllegalArgumentException(
+          "FieldDescriptor does not match message type.");
+      } else if (field.isExtension()) {
+        // If this type had extensions, it would subclass ExtendableMessage,
+        // which overrides the reflection interface to handle extensions.
+        throw new IllegalArgumentException(
+          "This type does not have extensions.");
+      }
+      return fields[field.getIndex()];
+    }
+
+    /**
+     * Abstract interface that provides access to a single field.  This is
+     * implemented differently depending on the field type and cardinality.
+     */
+    private interface FieldAccessor {
+      Object get(GeneratedMessage message);
+      void set(Builder builder, Object value);
+      Object getRepeated(GeneratedMessage message, int index);
+      void setRepeated(Builder builder,
+                       int index, Object value);
+      void addRepeated(Builder builder, Object value);
+      boolean has(GeneratedMessage message);
+      int getRepeatedCount(GeneratedMessage message);
+      void clear(Builder builder);
+      Message.Builder newBuilder();
+    }
+
+    // ---------------------------------------------------------------
+
+    private static class SingularFieldAccessor implements FieldAccessor {
+      SingularFieldAccessor(
+          final FieldDescriptor descriptor, final String camelCaseName,
+          final Class<? extends GeneratedMessage> messageClass,
+          final Class<? extends Builder> builderClass) {
+        getMethod = getMethodOrDie(messageClass, "get" + camelCaseName);
+        type = getMethod.getReturnType();
+        setMethod = getMethodOrDie(builderClass, "set" + camelCaseName, type);
+        hasMethod =
+          getMethodOrDie(messageClass, "has" + camelCaseName);
+        clearMethod = getMethodOrDie(builderClass, "clear" + camelCaseName);
+      }
+
+      // Note:  We use Java reflection to call public methods rather than
+      //   access private fields directly as this avoids runtime security
+      //   checks.
+      protected final Class type;
+      protected final Method getMethod;
+      protected final Method setMethod;
+      protected final Method hasMethod;
+      protected final Method clearMethod;
+
+      public Object get(final GeneratedMessage message) {
+        return invokeOrDie(getMethod, message);
+      }
+      public void set(final Builder builder, final Object value) {
+        invokeOrDie(setMethod, builder, value);
+      }
+      public Object getRepeated(final GeneratedMessage message,
+                                final int index) {
+        throw new UnsupportedOperationException(
+          "getRepeatedField() called on a singular field.");
+      }
+      public void setRepeated(final Builder builder,
+                              final int index, final Object value) {
+        throw new UnsupportedOperationException(
+          "setRepeatedField() called on a singular field.");
+      }
+      public void addRepeated(final Builder builder, final Object value) {
+        throw new UnsupportedOperationException(
+          "addRepeatedField() called on a singular field.");
+      }
+      public boolean has(final GeneratedMessage message) {
+        return (Boolean) invokeOrDie(hasMethod, message);
+      }
+      public int getRepeatedCount(final GeneratedMessage message) {
+        throw new UnsupportedOperationException(
+          "getRepeatedFieldSize() called on a singular field.");
+      }
+      public void clear(final Builder builder) {
+        invokeOrDie(clearMethod, builder);
+      }
+      public Message.Builder newBuilder() {
+        throw new UnsupportedOperationException(
+          "newBuilderForField() called on a non-Message type.");
+      }
+    }
+
+    private static class RepeatedFieldAccessor implements FieldAccessor {
+      RepeatedFieldAccessor(
+          final FieldDescriptor descriptor, final String camelCaseName,
+          final Class<? extends GeneratedMessage> messageClass,
+          final Class<? extends Builder> builderClass) {
+        getMethod = getMethodOrDie(messageClass,
+                                   "get" + camelCaseName + "List");
+
+        getRepeatedMethod =
+          getMethodOrDie(messageClass, "get" + camelCaseName, Integer.TYPE);
+        type = getRepeatedMethod.getReturnType();
+        setRepeatedMethod =
+          getMethodOrDie(builderClass, "set" + camelCaseName,
+                         Integer.TYPE, type);
+        addRepeatedMethod =
+          getMethodOrDie(builderClass, "add" + camelCaseName, type);
+        getCountMethod =
+          getMethodOrDie(messageClass, "get" + camelCaseName + "Count");
+
+        clearMethod = getMethodOrDie(builderClass, "clear" + camelCaseName);
+      }
+
+      protected final Class type;
+      protected final Method getMethod;
+      protected final Method getRepeatedMethod;
+      protected final Method setRepeatedMethod;
+      protected final Method addRepeatedMethod;
+      protected final Method getCountMethod;
+      protected final Method clearMethod;
+
+      public Object get(final GeneratedMessage message) {
+        return invokeOrDie(getMethod, message);
+      }
+      public void set(final Builder builder, final Object value) {
+        // Add all the elements individually.  This serves two purposes:
+        // 1) Verifies that each element has the correct type.
+        // 2) Insures that the caller cannot modify the list later on and
+        //    have the modifications be reflected in the message.
+        clear(builder);
+        for (final Object element : (List) value) {
+          addRepeated(builder, element);
+        }
+      }
+      public Object getRepeated(final GeneratedMessage message,
+                                final int index) {
+        return invokeOrDie(getRepeatedMethod, message, index);
+      }
+      public void setRepeated(final Builder builder,
+                              final int index, final Object value) {
+        invokeOrDie(setRepeatedMethod, builder, index, value);
+      }
+      public void addRepeated(final Builder builder, final Object value) {
+        invokeOrDie(addRepeatedMethod, builder, value);
+      }
+      public boolean has(final GeneratedMessage message) {
+        throw new UnsupportedOperationException(
+          "hasField() called on a singular field.");
+      }
+      public int getRepeatedCount(final GeneratedMessage message) {
+        return (Integer) invokeOrDie(getCountMethod, message);
+      }
+      public void clear(final Builder builder) {
+        invokeOrDie(clearMethod, builder);
+      }
+      public Message.Builder newBuilder() {
+        throw new UnsupportedOperationException(
+          "newBuilderForField() called on a non-Message type.");
+      }
+    }
+
+    // ---------------------------------------------------------------
+
+    private static final class SingularEnumFieldAccessor
+        extends SingularFieldAccessor {
+      SingularEnumFieldAccessor(
+          final FieldDescriptor descriptor, final String camelCaseName,
+          final Class<? extends GeneratedMessage> messageClass,
+          final Class<? extends Builder> builderClass) {
+        super(descriptor, camelCaseName, messageClass, builderClass);
+
+        valueOfMethod = getMethodOrDie(type, "valueOf",
+                                       EnumValueDescriptor.class);
+        getValueDescriptorMethod =
+          getMethodOrDie(type, "getValueDescriptor");
+      }
+
+      private Method valueOfMethod;
+      private Method getValueDescriptorMethod;
+
+      @Override
+      public Object get(final GeneratedMessage message) {
+        return invokeOrDie(getValueDescriptorMethod, super.get(message));
+      }
+      @Override
+      public void set(final Builder builder, final Object value) {
+        super.set(builder, invokeOrDie(valueOfMethod, null, value));
+      }
+    }
+
+    private static final class RepeatedEnumFieldAccessor
+        extends RepeatedFieldAccessor {
+      RepeatedEnumFieldAccessor(
+          final FieldDescriptor descriptor, final String camelCaseName,
+          final Class<? extends GeneratedMessage> messageClass,
+          final Class<? extends Builder> builderClass) {
+        super(descriptor, camelCaseName, messageClass, builderClass);
+
+        valueOfMethod = getMethodOrDie(type, "valueOf",
+                                       EnumValueDescriptor.class);
+        getValueDescriptorMethod =
+          getMethodOrDie(type, "getValueDescriptor");
+      }
+
+      private final Method valueOfMethod;
+      private final Method getValueDescriptorMethod;
+
+      @Override
+      @SuppressWarnings("unchecked")
+      public Object get(final GeneratedMessage message) {
+        final List newList = new ArrayList();
+        for (final Object element : (List) super.get(message)) {
+          newList.add(invokeOrDie(getValueDescriptorMethod, element));
+        }
+        return Collections.unmodifiableList(newList);
+      }
+      @Override
+      public Object getRepeated(final GeneratedMessage message,
+                                final int index) {
+        return invokeOrDie(getValueDescriptorMethod,
+          super.getRepeated(message, index));
+      }
+      @Override
+      public void setRepeated(final Builder builder,
+                              final int index, final Object value) {
+        super.setRepeated(builder, index, invokeOrDie(valueOfMethod, null,
+                          value));
+      }
+      @Override
+      public void addRepeated(final Builder builder, final Object value) {
+        super.addRepeated(builder, invokeOrDie(valueOfMethod, null, value));
+      }
+    }
+
+    // ---------------------------------------------------------------
+
+    private static final class SingularMessageFieldAccessor
+        extends SingularFieldAccessor {
+      SingularMessageFieldAccessor(
+          final FieldDescriptor descriptor, final String camelCaseName,
+          final Class<? extends GeneratedMessage> messageClass,
+          final Class<? extends Builder> builderClass) {
+        super(descriptor, camelCaseName, messageClass, builderClass);
+
+        newBuilderMethod = getMethodOrDie(type, "newBuilder");
+      }
+
+      private final Method newBuilderMethod;
+
+      private Object coerceType(final Object value) {
+        if (type.isInstance(value)) {
+          return value;
+        } else {
+          // The value is not the exact right message type.  However, if it
+          // is an alternative implementation of the same type -- e.g. a
+          // DynamicMessage -- we should accept it.  In this case we can make
+          // a copy of the message.
+          return ((Message.Builder) invokeOrDie(newBuilderMethod, null))
+                  .mergeFrom((Message) value).build();
+        }
+      }
+
+      @Override
+      public void set(final Builder builder, final Object value) {
+        super.set(builder, coerceType(value));
+      }
+      @Override
+      public Message.Builder newBuilder() {
+        return (Message.Builder) invokeOrDie(newBuilderMethod, null);
+      }
+    }
+
+    private static final class RepeatedMessageFieldAccessor
+        extends RepeatedFieldAccessor {
+      RepeatedMessageFieldAccessor(
+          final FieldDescriptor descriptor, final String camelCaseName,
+          final Class<? extends GeneratedMessage> messageClass,
+          final Class<? extends Builder> builderClass) {
+        super(descriptor, camelCaseName, messageClass, builderClass);
+
+        newBuilderMethod = getMethodOrDie(type, "newBuilder");
+      }
+
+      private final Method newBuilderMethod;
+
+      private Object coerceType(final Object value) {
+        if (type.isInstance(value)) {
+          return value;
+        } else {
+          // The value is not the exact right message type.  However, if it
+          // is an alternative implementation of the same type -- e.g. a
+          // DynamicMessage -- we should accept it.  In this case we can make
+          // a copy of the message.
+          return ((Message.Builder) invokeOrDie(newBuilderMethod, null))
+                  .mergeFrom((Message) value).build();
+        }
+      }
+
+      @Override
+      public void setRepeated(final Builder builder,
+                              final int index, final Object value) {
+        super.setRepeated(builder, index, coerceType(value));
+      }
+      @Override
+      public void addRepeated(final Builder builder, final Object value) {
+        super.addRepeated(builder, coerceType(value));
+      }
+      @Override
+      public Message.Builder newBuilder() {
+        return (Message.Builder) invokeOrDie(newBuilderMethod, null);
+      }
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java b/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java
new file mode 100644
index 0000000..c68414b
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java
@@ -0,0 +1,539 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Lite version of {@link GeneratedMessage}.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public abstract class GeneratedMessageLite extends AbstractMessageLite {
+  protected GeneratedMessageLite() {}
+
+  @SuppressWarnings("unchecked")
+  public abstract static class Builder<MessageType extends GeneratedMessageLite,
+                                       BuilderType extends Builder>
+      extends AbstractMessageLite.Builder<BuilderType> {
+    protected Builder() {}
+
+    // This is implemented here only to work around an apparent bug in the
+    // Java compiler and/or build system.  See bug #1898463.  The mere presence
+    // of this dummy clone() implementation makes it go away.
+    @Override
+    public BuilderType clone() {
+      throw new UnsupportedOperationException(
+          "This is supposed to be overridden by subclasses.");
+    }
+
+    /** All subclasses implement this. */
+    public abstract BuilderType mergeFrom(MessageType message);
+
+    // Defined here for return type covariance.
+    public abstract MessageType getDefaultInstanceForType();
+
+    /**
+     * Get the message being built.  We don't just pass this to the
+     * constructor because it becomes null when build() is called.
+     */
+    protected abstract MessageType internalGetResult();
+
+    /**
+     * Called by subclasses to parse an unknown field.
+     * @return {@code true} unless the tag is an end-group tag.
+     */
+    protected boolean parseUnknownField(
+        final CodedInputStream input,
+        final ExtensionRegistryLite extensionRegistry,
+        final int tag) throws IOException {
+      return input.skipField(tag);
+    }
+  }
+
+  // =================================================================
+  // Extensions-related stuff
+
+  /**
+   * Lite equivalent of {@link GeneratedMessage.ExtendableMessage}.
+   */
+  public abstract static class ExtendableMessage<
+        MessageType extends ExtendableMessage<MessageType>>
+      extends GeneratedMessageLite {
+    protected ExtendableMessage() {}
+    private final FieldSet<ExtensionDescriptor> extensions =
+        FieldSet.newFieldSet();
+
+    private void verifyExtensionContainingType(
+        final GeneratedExtension<MessageType, ?> extension) {
+      if (extension.getContainingTypeDefaultInstance() !=
+          getDefaultInstanceForType()) {
+        // This can only happen if someone uses unchecked operations.
+        throw new IllegalArgumentException(
+          "This extension is for a different message type.  Please make " +
+          "sure that you are not suppressing any generics type warnings.");
+      }
+    }
+
+    /** Check if a singular extension is present. */
+    public final boolean hasExtension(
+        final GeneratedExtension<MessageType, ?> extension) {
+      verifyExtensionContainingType(extension);
+      return extensions.hasField(extension.descriptor);
+    }
+
+    /** Get the number of elements in a repeated extension. */
+    public final <Type> int getExtensionCount(
+        final GeneratedExtension<MessageType, List<Type>> extension) {
+      verifyExtensionContainingType(extension);
+      return extensions.getRepeatedFieldCount(extension.descriptor);
+    }
+
+    /** Get the value of an extension. */
+    @SuppressWarnings("unchecked")
+    public final <Type> Type getExtension(
+        final GeneratedExtension<MessageType, Type> extension) {
+      verifyExtensionContainingType(extension);
+      final Object value = extensions.getField(extension.descriptor);
+      if (value == null) {
+        return extension.defaultValue;
+      } else {
+        return (Type) value;
+      }
+    }
+
+    /** Get one element of a repeated extension. */
+    @SuppressWarnings("unchecked")
+    public final <Type> Type getExtension(
+        final GeneratedExtension<MessageType, List<Type>> extension,
+        final int index) {
+      verifyExtensionContainingType(extension);
+      return (Type) extensions.getRepeatedField(extension.descriptor, index);
+    }
+
+    /** Called by subclasses to check if all extensions are initialized. */
+    protected boolean extensionsAreInitialized() {
+      return extensions.isInitialized();
+    }
+
+    /**
+     * Used by subclasses to serialize extensions.  Extension ranges may be
+     * interleaved with field numbers, but we must write them in canonical
+     * (sorted by field number) order.  ExtensionWriter helps us write
+     * individual ranges of extensions at once.
+     */
+    protected class ExtensionWriter {
+      // Imagine how much simpler this code would be if Java iterators had
+      // a way to get the next element without advancing the iterator.
+
+      private final Iterator<Map.Entry<ExtensionDescriptor, Object>> iter =
+            extensions.iterator();
+      private Map.Entry<ExtensionDescriptor, Object> next;
+      private final boolean messageSetWireFormat;
+
+      private ExtensionWriter(boolean messageSetWireFormat) {
+        if (iter.hasNext()) {
+          next = iter.next();
+        }
+        this.messageSetWireFormat = messageSetWireFormat;
+      }
+
+      public void writeUntil(final int end, final CodedOutputStream output)
+                             throws IOException {
+        while (next != null && next.getKey().getNumber() < end) {
+          ExtensionDescriptor extension = next.getKey();
+          if (messageSetWireFormat && extension.getLiteJavaType() ==
+                  WireFormat.JavaType.MESSAGE &&
+              !extension.isRepeated()) {
+            output.writeMessageSetExtension(extension.getNumber(),
+                                            (MessageLite) next.getValue());
+          } else {
+            FieldSet.writeField(extension, next.getValue(), output);
+          }
+          if (iter.hasNext()) {
+            next = iter.next();
+          } else {
+            next = null;
+          }
+        }
+      }
+    }
+
+    protected ExtensionWriter newExtensionWriter() {
+      return new ExtensionWriter(false);
+    }
+    protected ExtensionWriter newMessageSetExtensionWriter() {
+      return new ExtensionWriter(true);
+    }
+
+    /** Called by subclasses to compute the size of extensions. */
+    protected int extensionsSerializedSize() {
+      return extensions.getSerializedSize();
+    }
+    protected int extensionsSerializedSizeAsMessageSet() {
+      return extensions.getMessageSetSerializedSize();
+    }
+  }
+
+  /**
+   * Lite equivalent of {@link GeneratedMessage.ExtendableBuilder}.
+   */
+  @SuppressWarnings("unchecked")
+  public abstract static class ExtendableBuilder<
+        MessageType extends ExtendableMessage<MessageType>,
+        BuilderType extends ExtendableBuilder<MessageType, BuilderType>>
+      extends Builder<MessageType, BuilderType> {
+    protected ExtendableBuilder() {}
+
+    // This is implemented here only to work around an apparent bug in the
+    // Java compiler and/or build system.  See bug #1898463.  The mere presence
+    // of this dummy clone() implementation makes it go away.
+    @Override
+    public BuilderType clone() {
+      throw new UnsupportedOperationException(
+          "This is supposed to be overridden by subclasses.");
+    }
+
+    @Override
+    protected abstract MessageType internalGetResult();
+
+    /** Check if a singular extension is present. */
+    public final boolean hasExtension(
+        final GeneratedExtension<MessageType, ?> extension) {
+      return internalGetResult().hasExtension(extension);
+    }
+
+    /** Get the number of elements in a repeated extension. */
+    public final <Type> int getExtensionCount(
+        final GeneratedExtension<MessageType, List<Type>> extension) {
+      return internalGetResult().getExtensionCount(extension);
+    }
+
+    /** Get the value of an extension. */
+    public final <Type> Type getExtension(
+        final GeneratedExtension<MessageType, Type> extension) {
+      return internalGetResult().getExtension(extension);
+    }
+
+    /** Get one element of a repeated extension. */
+    public final <Type> Type getExtension(
+        final GeneratedExtension<MessageType, List<Type>> extension,
+        final int index) {
+      return internalGetResult().getExtension(extension, index);
+    }
+
+    /** Set the value of an extension. */
+    public final <Type> BuilderType setExtension(
+        final GeneratedExtension<MessageType, Type> extension,
+        final Type value) {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      message.verifyExtensionContainingType(extension);
+      message.extensions.setField(extension.descriptor, value);
+      return (BuilderType) this;
+    }
+
+    /** Set the value of one element of a repeated extension. */
+    public final <Type> BuilderType setExtension(
+        final GeneratedExtension<MessageType, List<Type>> extension,
+        final int index, final Type value) {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      message.verifyExtensionContainingType(extension);
+      message.extensions.setRepeatedField(extension.descriptor, index, value);
+      return (BuilderType) this;
+    }
+
+    /** Append a value to a repeated extension. */
+    public final <Type> BuilderType addExtension(
+        final GeneratedExtension<MessageType, List<Type>> extension,
+        final Type value) {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      message.verifyExtensionContainingType(extension);
+      message.extensions.addRepeatedField(extension.descriptor, value);
+      return (BuilderType) this;
+    }
+
+    /** Clear an extension. */
+    public final <Type> BuilderType clearExtension(
+        final GeneratedExtension<MessageType, ?> extension) {
+      final ExtendableMessage<MessageType> message = internalGetResult();
+      message.verifyExtensionContainingType(extension);
+      message.extensions.clearField(extension.descriptor);
+      return (BuilderType) this;
+    }
+
+    /**
+     * Called by subclasses to parse an unknown field or an extension.
+     * @return {@code true} unless the tag is an end-group tag.
+     */
+    @Override
+    protected boolean parseUnknownField(
+        final CodedInputStream input,
+        final ExtensionRegistryLite extensionRegistry,
+        final int tag) throws IOException {
+      final FieldSet<ExtensionDescriptor> extensions =
+          internalGetResult().extensions;
+
+      final int wireType = WireFormat.getTagWireType(tag);
+      final int fieldNumber = WireFormat.getTagFieldNumber(tag);
+
+      final GeneratedExtension<MessageType, ?> extension =
+        extensionRegistry.findLiteExtensionByNumber(
+            getDefaultInstanceForType(), fieldNumber);
+
+      if (extension == null || wireType !=
+            FieldSet.getWireFormatForFieldType(
+                extension.descriptor.getLiteType(),
+                extension.descriptor.isPacked())) {
+        // Unknown field or wrong wire type.  Skip.
+        return input.skipField(tag);
+      }
+
+      if (extension.descriptor.isPacked()) {
+        final int length = input.readRawVarint32();
+        final int limit = input.pushLimit(length);
+        if (extension.descriptor.getLiteType() == WireFormat.FieldType.ENUM) {
+          while (input.getBytesUntilLimit() > 0) {
+            final int rawValue = input.readEnum();
+            final Object value =
+                extension.descriptor.getEnumType().findValueByNumber(rawValue);
+            if (value == null) {
+              // If the number isn't recognized as a valid value for this
+              // enum, drop it (don't even add it to unknownFields).
+              return true;
+            }
+            extensions.addRepeatedField(extension.descriptor, value);
+          }
+        } else {
+          while (input.getBytesUntilLimit() > 0) {
+            final Object value =
+              FieldSet.readPrimitiveField(input,
+                                          extension.descriptor.getLiteType());
+            extensions.addRepeatedField(extension.descriptor, value);
+          }
+        }
+        input.popLimit(limit);
+      } else {
+        final Object value;
+        switch (extension.descriptor.getLiteJavaType()) {
+          case MESSAGE: {
+            MessageLite.Builder subBuilder = null;
+            if (!extension.descriptor.isRepeated()) {
+              MessageLite existingValue =
+                  (MessageLite) extensions.getField(extension.descriptor);
+              if (existingValue != null) {
+                subBuilder = existingValue.toBuilder();
+              }
+            }
+            if (subBuilder == null) {
+              subBuilder = extension.messageDefaultInstance.newBuilderForType();
+            }
+            if (extension.descriptor.getLiteType() ==
+                WireFormat.FieldType.GROUP) {
+              input.readGroup(extension.getNumber(),
+                              subBuilder, extensionRegistry);
+            } else {
+              input.readMessage(subBuilder, extensionRegistry);
+            }
+            value = subBuilder.build();
+            break;
+          }
+          case ENUM:
+            final int rawValue = input.readEnum();
+            value = extension.descriptor.getEnumType()
+                             .findValueByNumber(rawValue);
+            // If the number isn't recognized as a valid value for this enum,
+            // drop it.
+            if (value == null) {
+              return true;
+            }
+            break;
+          default:
+            value = FieldSet.readPrimitiveField(input,
+                extension.descriptor.getLiteType());
+            break;
+        }
+
+        if (extension.descriptor.isRepeated()) {
+          extensions.addRepeatedField(extension.descriptor, value);
+        } else {
+          extensions.setField(extension.descriptor, value);
+        }
+      }
+
+      return true;
+    }
+
+    protected final void mergeExtensionFields(final MessageType other) {
+      internalGetResult().extensions.mergeFrom(other.extensions);
+    }
+  }
+
+  // -----------------------------------------------------------------
+
+  /** For use by generated code only. */
+  public static <ContainingType extends MessageLite, Type>
+      GeneratedExtension<ContainingType, Type>
+      newGeneratedExtension(
+        final ContainingType containingTypeDefaultInstance,
+        final Type defaultValue,
+        final MessageLite messageDefaultInstance,
+        final Internal.EnumLiteMap<?> enumTypeMap,
+        final int number,
+        final WireFormat.FieldType type) {
+    return new GeneratedExtension<ContainingType, Type>(
+      containingTypeDefaultInstance, defaultValue, messageDefaultInstance,
+      new ExtensionDescriptor(enumTypeMap, number, type,
+        false /* isRepeated */, false /* isPacked */));
+  }
+
+  /** For use by generated code only. */
+  public static <ContainingType extends MessageLite, Type>
+      GeneratedExtension<ContainingType, List<Type>>
+      newRepeatedGeneratedExtension(
+        final ContainingType containingTypeDefaultInstance,
+        final MessageLite messageDefaultInstance,
+        final Internal.EnumLiteMap<?> enumTypeMap,
+        final int number,
+        final WireFormat.FieldType type,
+        final boolean isPacked) {
+    return new GeneratedExtension<ContainingType, List<Type>>(
+      containingTypeDefaultInstance, Collections.<Type>emptyList(),
+      messageDefaultInstance,
+      new ExtensionDescriptor(
+        enumTypeMap, number, type, true /* isRepeated */, isPacked));
+  }
+
+  private static final class ExtensionDescriptor
+      implements FieldSet.FieldDescriptorLite<
+        ExtensionDescriptor> {
+    private ExtensionDescriptor(
+        final Internal.EnumLiteMap<?> enumTypeMap,
+        final int number,
+        final WireFormat.FieldType type,
+        final boolean isRepeated,
+        final boolean isPacked) {
+      this.enumTypeMap = enumTypeMap;
+      this.number = number;
+      this.type = type;
+      this.isRepeated = isRepeated;
+      this.isPacked = isPacked;
+    }
+
+    private final Internal.EnumLiteMap<?> enumTypeMap;
+    private final int number;
+    private final WireFormat.FieldType type;
+    private final boolean isRepeated;
+    private final boolean isPacked;
+
+    public int getNumber() {
+      return number;
+    }
+
+    public WireFormat.FieldType getLiteType() {
+      return type;
+    }
+
+    public WireFormat.JavaType getLiteJavaType() {
+      return type.getJavaType();
+    }
+
+    public boolean isRepeated() {
+      return isRepeated;
+    }
+
+    public boolean isPacked() {
+      return isPacked;
+    }
+
+    public Internal.EnumLiteMap<?> getEnumType() {
+      return enumTypeMap;
+    }
+
+    @SuppressWarnings("unchecked")
+    public MessageLite.Builder internalMergeFrom(
+        MessageLite.Builder to, MessageLite from) {
+      return ((Builder) to).mergeFrom((GeneratedMessageLite) from);
+    }
+
+    public int compareTo(ExtensionDescriptor other) {
+      return number - other.number;
+    }
+  }
+
+  /**
+   * Lite equivalent to {@link GeneratedMessage.GeneratedExtension}.
+   *
+   * Users should ignore the contents of this class and only use objects of
+   * this type as parameters to extension accessors and ExtensionRegistry.add().
+   */
+  public static final class GeneratedExtension<
+      ContainingType extends MessageLite, Type> {
+    private GeneratedExtension(
+        final ContainingType containingTypeDefaultInstance,
+        final Type defaultValue,
+        final MessageLite messageDefaultInstance,
+        final ExtensionDescriptor descriptor) {
+      this.containingTypeDefaultInstance = containingTypeDefaultInstance;
+      this.defaultValue = defaultValue;
+      this.messageDefaultInstance = messageDefaultInstance;
+      this.descriptor = descriptor;
+    }
+
+    private final ContainingType containingTypeDefaultInstance;
+    private final Type defaultValue;
+    private final MessageLite messageDefaultInstance;
+    private final ExtensionDescriptor descriptor;
+
+    /**
+     * Default instance of the type being extended, used to identify that type.
+     */
+    public ContainingType getContainingTypeDefaultInstance() {
+      return containingTypeDefaultInstance;
+    }
+
+    /** Get the field number. */
+    public int getNumber() {
+      return descriptor.getNumber();
+    }
+
+    /**
+     * If the extension is an embedded message, this is the default instance of
+     * that type.
+     */
+    public MessageLite getMessageDefaultInstance() {
+      return messageDefaultInstance;
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/Internal.java b/java/src/main/java/com/google/protobuf/Internal.java
new file mode 100644
index 0000000..965465e
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/Internal.java
@@ -0,0 +1,121 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.UnsupportedEncodingException;
+
+/**
+ * The classes contained within are used internally by the Protocol Buffer
+ * library and generated message implementations. They are public only because
+ * those generated messages do not reside in the {@code protobuf} package.
+ * Others should not use this class directly.
+ *
+ * @author kenton@google.com (Kenton Varda)
+ */
+public class Internal {
+  /**
+   * Helper called by generated code to construct default values for string
+   * fields.
+   * <p>
+   * The protocol compiler does not actually contain a UTF-8 decoder -- it
+   * just pushes UTF-8-encoded text around without touching it.  The one place
+   * where this presents a problem is when generating Java string literals.
+   * Unicode characters in the string literal would normally need to be encoded
+   * using a Unicode escape sequence, which would require decoding them.
+   * To get around this, protoc instead embeds the UTF-8 bytes into the
+   * generated code and leaves it to the runtime library to decode them.
+   * <p>
+   * It gets worse, though.  If protoc just generated a byte array, like:
+   *   new byte[] {0x12, 0x34, 0x56, 0x78}
+   * Java actually generates *code* which allocates an array and then fills
+   * in each value.  This is much less efficient than just embedding the bytes
+   * directly into the bytecode.  To get around this, we need another
+   * work-around.  String literals are embedded directly, so protoc actually
+   * generates a string literal corresponding to the bytes.  The easiest way
+   * to do this is to use the ISO-8859-1 character set, which corresponds to
+   * the first 256 characters of the Unicode range.  Protoc can then use
+   * good old CEscape to generate the string.
+   * <p>
+   * So we have a string literal which represents a set of bytes which
+   * represents another string.  This function -- stringDefaultValue --
+   * converts from the generated string to the string we actually want.  The
+   * generated code calls this automatically.
+   */
+  public static String stringDefaultValue(String bytes) {
+    try {
+      return new String(bytes.getBytes("ISO-8859-1"), "UTF-8");
+    } catch (UnsupportedEncodingException e) {
+      // This should never happen since all JVMs are required to implement
+      // both of the above character sets.
+      throw new IllegalStateException(
+          "Java VM does not support a standard character set.", e);
+    }
+  }
+
+  /**
+   * Helper called by generated code to construct default values for bytes
+   * fields.
+   * <p>
+   * This is a lot like {@link #stringDefaultValue}, but for bytes fields.
+   * In this case we only need the second of the two hacks -- allowing us to
+   * embed raw bytes as a string literal with ISO-8859-1 encoding.
+   */
+  public static ByteString bytesDefaultValue(String bytes) {
+    try {
+      return ByteString.copyFrom(bytes.getBytes("ISO-8859-1"));
+    } catch (UnsupportedEncodingException e) {
+      // This should never happen since all JVMs are required to implement
+      // ISO-8859-1.
+      throw new IllegalStateException(
+          "Java VM does not support a standard character set.", e);
+    }
+  }
+
+  /**
+   * Interface for an enum value or value descriptor, to be used in FieldSet.
+   * The lite library stores enum values directly in FieldSets but the full
+   * library stores EnumValueDescriptors in order to better support reflection.
+   */
+  public interface EnumLite {
+    int getNumber();
+  }
+
+  /**
+   * Interface for an object which maps integers to {@link EnumLite}s.
+   * {@link Descriptors.EnumDescriptor} implements this interface by mapping
+   * numbers to {@link Descriptors.EnumValueDescriptor}s.  Additionally,
+   * every generated enum type has a static method internalGetValueMap() which
+   * returns an implementation of this type that maps numbers to enum values.
+   */
+  public interface EnumLiteMap<T extends EnumLite> {
+    T findValueByNumber(int number);
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/InvalidProtocolBufferException.java b/java/src/main/java/com/google/protobuf/InvalidProtocolBufferException.java
new file mode 100644
index 0000000..90f7ffb
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/InvalidProtocolBufferException.java
@@ -0,0 +1,93 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+
+/**
+ * Thrown when a protocol message being parsed is invalid in some way,
+ * e.g. it contains a malformed varint or a negative byte length.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public class InvalidProtocolBufferException extends IOException {
+  private static final long serialVersionUID = -1616151763072450476L;
+
+  public InvalidProtocolBufferException(final String description) {
+    super(description);
+  }
+
+  static InvalidProtocolBufferException truncatedMessage() {
+    return new InvalidProtocolBufferException(
+      "While parsing a protocol message, the input ended unexpectedly " +
+      "in the middle of a field.  This could mean either than the " +
+      "input has been truncated or that an embedded message " +
+      "misreported its own length.");
+  }
+
+  static InvalidProtocolBufferException negativeSize() {
+    return new InvalidProtocolBufferException(
+      "CodedInputStream encountered an embedded string or message " +
+      "which claimed to have negative size.");
+  }
+
+  static InvalidProtocolBufferException malformedVarint() {
+    return new InvalidProtocolBufferException(
+      "CodedInputStream encountered a malformed varint.");
+  }
+
+  static InvalidProtocolBufferException invalidTag() {
+    return new InvalidProtocolBufferException(
+      "Protocol message contained an invalid tag (zero).");
+  }
+
+  static InvalidProtocolBufferException invalidEndTag() {
+    return new InvalidProtocolBufferException(
+      "Protocol message end-group tag did not match expected tag.");
+  }
+
+  static InvalidProtocolBufferException invalidWireType() {
+    return new InvalidProtocolBufferException(
+      "Protocol message tag had invalid wire type.");
+  }
+
+  static InvalidProtocolBufferException recursionLimitExceeded() {
+    return new InvalidProtocolBufferException(
+      "Protocol message had too many levels of nesting.  May be malicious.  " +
+      "Use CodedInputStream.setRecursionLimit() to increase the depth limit.");
+  }
+
+  static InvalidProtocolBufferException sizeLimitExceeded() {
+    return new InvalidProtocolBufferException(
+      "Protocol message was too large.  May be malicious.  " +
+      "Use CodedInputStream.setSizeLimit() to increase the size limit.");
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/Message.java b/java/src/main/java/com/google/protobuf/Message.java
new file mode 100644
index 0000000..c11abdc
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/Message.java
@@ -0,0 +1,305 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// TODO(kenton):  Use generics?  E.g. Builder<BuilderType extends Builder>, then
+//   mergeFrom*() could return BuilderType for better type-safety.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Map;
+
+/**
+ * Abstract interface implemented by Protocol Message objects.
+ * <p>
+ * See also {@link MessageLite}, which defines most of the methods that typical
+ * users care about.  {@link Message} adds to it methods that are not available
+ * in the "lite" runtime.  The biggest added features are introspection and
+ * reflection -- i.e., getting descriptors for the message type and accessing
+ * the field values dynamically.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public interface Message extends MessageLite {
+  /**
+   * Get the message's type's descriptor.  This differs from the
+   * {@code getDescriptor()} method of generated message classes in that
+   * this method is an abstract method of the {@code Message} interface
+   * whereas {@code getDescriptor()} is a static method of a specific class.
+   * They return the same thing.
+   */
+  Descriptors.Descriptor getDescriptorForType();
+
+  // (From MessageLite, re-declared here only for return type covariance.)
+  Message getDefaultInstanceForType();
+
+  /**
+   * Returns a collection of all the fields in this message which are set
+   * and their corresponding values.  A singular ("required" or "optional")
+   * field is set iff hasField() returns true for that field.  A "repeated"
+   * field is set iff getRepeatedFieldSize() is greater than zero.  The
+   * values are exactly what would be returned by calling
+   * {@link #getField(Descriptors.FieldDescriptor)} for each field.  The map
+   * is guaranteed to be a sorted map, so iterating over it will return fields
+   * in order by field number.
+   */
+  Map<Descriptors.FieldDescriptor, Object> getAllFields();
+
+  /**
+   * Returns true if the given field is set.  This is exactly equivalent to
+   * calling the generated "has" accessor method corresponding to the field.
+   * @throws IllegalArgumentException The field is a repeated field, or
+   *           {@code field.getContainingType() != getDescriptorForType()}.
+   */
+  boolean hasField(Descriptors.FieldDescriptor field);
+
+  /**
+   * Obtains the value of the given field, or the default value if it is
+   * not set.  For primitive fields, the boxed primitive value is returned.
+   * For enum fields, the EnumValueDescriptor for the value is returend. For
+   * embedded message fields, the sub-message is returned.  For repeated
+   * fields, a java.util.List is returned.
+   */
+  Object getField(Descriptors.FieldDescriptor field);
+
+  /**
+   * Gets the number of elements of a repeated field.  This is exactly
+   * equivalent to calling the generated "Count" accessor method corresponding
+   * to the field.
+   * @throws IllegalArgumentException The field is not a repeated field, or
+   *           {@code field.getContainingType() != getDescriptorForType()}.
+   */
+  int getRepeatedFieldCount(Descriptors.FieldDescriptor field);
+
+  /**
+   * Gets an element of a repeated field.  For primitive fields, the boxed
+   * primitive value is returned.  For enum fields, the EnumValueDescriptor
+   * for the value is returend. For embedded message fields, the sub-message
+   * is returned.
+   * @throws IllegalArgumentException The field is not a repeated field, or
+   *           {@code field.getContainingType() != getDescriptorForType()}.
+   */
+  Object getRepeatedField(Descriptors.FieldDescriptor field, int index);
+
+  /** Get the {@link UnknownFieldSet} for this message. */
+  UnknownFieldSet getUnknownFields();
+
+  // -----------------------------------------------------------------
+  // Comparison and hashing
+
+  /**
+   * Compares the specified object with this message for equality.  Returns
+   * <tt>true</tt> if the given object is a message of the same type (as
+   * defined by {@code getDescriptorForType()}) and has identical values for
+   * all of its fields.
+   *
+   * @param other object to be compared for equality with this message
+   * @return <tt>true</tt> if the specified object is equal to this message
+   */
+  @Override
+  boolean equals(Object other);
+
+  /**
+   * Returns the hash code value for this message.  The hash code of a message
+   * is defined to be <tt>getDescriptor().hashCode() ^ map.hashCode()</tt>,
+   * where <tt>map</tt> is a map of field numbers to field values.
+   *
+   * @return the hash code value for this message
+   * @see Map#hashCode()
+   */
+  @Override
+  int hashCode();
+
+  // -----------------------------------------------------------------
+  // Convenience methods.
+
+  /**
+   * Converts the message to a string in protocol buffer text format. This is
+   * just a trivial wrapper around {@link TextFormat#printToString(Message)}.
+   */
+  @Override
+  String toString();
+
+  // =================================================================
+  // Builders
+
+  // (From MessageLite, re-declared here only for return type covariance.)
+  Builder newBuilderForType();
+  Builder toBuilder();
+
+  /**
+   * Abstract interface implemented by Protocol Message builders.
+   */
+  interface Builder extends MessageLite.Builder {
+    // (From MessageLite.Builder, re-declared here only for return type
+    // covariance.)
+    Builder clear();
+
+    /**
+     * Merge {@code other} into the message being built.  {@code other} must
+     * have the exact same type as {@code this} (i.e.
+     * {@code getDescriptorForType() == other.getDescriptorForType()}).
+     *
+     * Merging occurs as follows.  For each field:<br>
+     * * For singular primitive fields, if the field is set in {@code other},
+     *   then {@code other}'s value overwrites the value in this message.<br>
+     * * For singular message fields, if the field is set in {@code other},
+     *   it is merged into the corresponding sub-message of this message
+     *   using the same merging rules.<br>
+     * * For repeated fields, the elements in {@code other} are concatenated
+     *   with the elements in this message.
+     *
+     * This is equivalent to the {@code Message::MergeFrom} method in C++.
+     */
+    Builder mergeFrom(Message other);
+
+    // (From MessageLite.Builder, re-declared here only for return type
+    // covariance.)
+    Message build();
+    Message buildPartial();
+    Builder clone();
+    Builder mergeFrom(CodedInputStream input) throws IOException;
+    Builder mergeFrom(CodedInputStream input,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws IOException;
+
+    /**
+     * Get the message's type's descriptor.
+     * See {@link Message#getDescriptorForType()}.
+     */
+    Descriptors.Descriptor getDescriptorForType();
+
+    // (From MessageLite.Builder, re-declared here only for return type
+    // covariance.)
+    Message getDefaultInstanceForType();
+
+    /**
+     * Like {@link Message#getAllFields()}.  The returned map may or may not
+     * reflect future changes to the builder.  Either way, the returned map is
+     * itself unmodifiable.
+     */
+    Map<Descriptors.FieldDescriptor, Object> getAllFields();
+
+    /**
+     * Create a Builder for messages of the appropriate type for the given
+     * field.  Messages built with this can then be passed to setField(),
+     * setRepeatedField(), or addRepeatedField().
+     */
+    Builder newBuilderForField(Descriptors.FieldDescriptor field);
+
+    /** Like {@link Message#hasField(Descriptors.FieldDescriptor)} */
+    boolean hasField(Descriptors.FieldDescriptor field);
+
+    /** Like {@link Message#getField(Descriptors.FieldDescriptor)} */
+    Object getField(Descriptors.FieldDescriptor field);
+
+    /**
+     * Sets a field to the given value.  The value must be of the correct type
+     * for this field, i.e. the same type that
+     * {@link Message#getField(Descriptors.FieldDescriptor)} would return.
+     */
+    Builder setField(Descriptors.FieldDescriptor field, Object value);
+
+    /**
+     * Clears the field.  This is exactly equivalent to calling the generated
+     * "clear" accessor method corresponding to the field.
+     */
+    Builder clearField(Descriptors.FieldDescriptor field);
+
+    /**
+     * Like {@link Message#getRepeatedFieldCount(Descriptors.FieldDescriptor)}
+     */
+    int getRepeatedFieldCount(Descriptors.FieldDescriptor field);
+
+    /**
+     * Like {@link Message#getRepeatedField(Descriptors.FieldDescriptor,int)}
+     */
+    Object getRepeatedField(Descriptors.FieldDescriptor field, int index);
+
+    /**
+     * Sets an element of a repeated field to the given value.  The value must
+     * be of the correct type for this field, i.e. the same type that
+     * {@link Message#getRepeatedField(Descriptors.FieldDescriptor,int)} would
+     * return.
+     * @throws IllegalArgumentException The field is not a repeated field, or
+     *           {@code field.getContainingType() != getDescriptorForType()}.
+     */
+    Builder setRepeatedField(Descriptors.FieldDescriptor field,
+                             int index, Object value);
+
+    /**
+     * Like {@code setRepeatedField}, but appends the value as a new element.
+     * @throws IllegalArgumentException The field is not a repeated field, or
+     *           {@code field.getContainingType() != getDescriptorForType()}.
+     */
+    Builder addRepeatedField(Descriptors.FieldDescriptor field, Object value);
+
+    /** Get the {@link UnknownFieldSet} for this message. */
+    UnknownFieldSet getUnknownFields();
+
+    /** Set the {@link UnknownFieldSet} for this message. */
+    Builder setUnknownFields(UnknownFieldSet unknownFields);
+
+    /**
+     * Merge some unknown fields into the {@link UnknownFieldSet} for this
+     * message.
+     */
+    Builder mergeUnknownFields(UnknownFieldSet unknownFields);
+
+    // ---------------------------------------------------------------
+    // Convenience methods.
+
+    // (From MessageLite.Builder, re-declared here only for return type
+    // covariance.)
+    Builder mergeFrom(ByteString data) throws InvalidProtocolBufferException;
+    Builder mergeFrom(ByteString data,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws InvalidProtocolBufferException;
+    Builder mergeFrom(byte[] data) throws InvalidProtocolBufferException;
+    Builder mergeFrom(byte[] data, int off, int len)
+                      throws InvalidProtocolBufferException;
+    Builder mergeFrom(byte[] data,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws InvalidProtocolBufferException;
+    Builder mergeFrom(byte[] data, int off, int len,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws InvalidProtocolBufferException;
+    Builder mergeFrom(InputStream input) throws IOException;
+    Builder mergeFrom(InputStream input,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws IOException;
+    Builder mergeDelimitedFrom(InputStream input)
+                               throws IOException;
+    Builder mergeDelimitedFrom(InputStream input,
+                               ExtensionRegistryLite extensionRegistry)
+                               throws IOException;
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/MessageLite.java b/java/src/main/java/com/google/protobuf/MessageLite.java
new file mode 100644
index 0000000..3ebe9bb
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/MessageLite.java
@@ -0,0 +1,331 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// TODO(kenton):  Use generics?  E.g. Builder<BuilderType extends Builder>, then
+//   mergeFrom*() could return BuilderType for better type-safety.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+/**
+ * Abstract interface implemented by Protocol Message objects.
+ *
+ * <p>This interface is implemented by all protocol message objects.  Non-lite
+ * messages additionally implement the Message interface, which is a subclass
+ * of MessageLite.  Use MessageLite instead when you only need the subset of
+ * features which it supports -- namely, nothing that uses descriptors or
+ * reflection.  You can instruct the protocol compiler to generate classes
+ * which implement only MessageLite, not the full Message interface, by adding
+ * the follow line to the .proto file:
+ * <pre>
+ *   option optimize_for = LITE_RUNTIME;
+ * </pre>
+ *
+ * <p>This is particularly useful on resource-constrained systems where the
+ * full protocol buffers runtime library is too big.
+ *
+ * <p>Note that on non-constrained systems (e.g. servers) when you need to link
+ * in lots of protocol definitions, a better way to reduce total code footprint
+ * is to use {@code optimize_for = CODE_SIZE}.  This will make the generated
+ * code smaller while still supporting all the same features (at the expense of
+ * speed).  {@code optimize_for = LITE_RUNTIME} is best when you only have a
+ * small number of message types linked into your binary, in which case the
+ * size of the protocol buffers runtime itself is the biggest problem.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public interface MessageLite {
+  /**
+   * Get an instance of the type with all fields set to their default values.
+   * This may or may not be a singleton.  This differs from the
+   * {@code getDefaultInstance()} method of generated message classes in that
+   * this method is an abstract method of the {@code MessageLite} interface
+   * whereas {@code getDefaultInstance()} is a static method of a specific
+   * class.  They return the same thing.
+   */
+  MessageLite getDefaultInstanceForType();
+
+  /**
+   * Returns true if all required fields in the message and all embedded
+   * messages are set, false otherwise.
+   */
+  boolean isInitialized();
+
+  /**
+   * Serializes the message and writes it to {@code output}.  This does not
+   * flush or close the stream.
+   */
+  void writeTo(CodedOutputStream output) throws IOException;
+
+  /**
+   * Get the number of bytes required to encode this message.  The result
+   * is only computed on the first call and memoized after that.
+   */
+  int getSerializedSize();
+
+  // -----------------------------------------------------------------
+  // Convenience methods.
+
+  /**
+   * Serializes the message to a {@code ByteString} and returns it. This is
+   * just a trivial wrapper around
+   * {@link #writeTo(CodedOutputStream)}.
+   */
+  ByteString toByteString();
+
+  /**
+   * Serializes the message to a {@code byte} array and returns it.  This is
+   * just a trivial wrapper around
+   * {@link #writeTo(CodedOutputStream)}.
+   */
+  byte[] toByteArray();
+
+  /**
+   * Serializes the message and writes it to {@code output}.  This is just a
+   * trivial wrapper around {@link #writeTo(CodedOutputStream)}.  This does
+   * not flush or close the stream.
+   * <p>
+   * NOTE:  Protocol Buffers are not self-delimiting.  Therefore, if you write
+   * any more data to the stream after the message, you must somehow ensure
+   * that the parser on the receiving end does not interpret this as being
+   * part of the protocol message.  This can be done e.g. by writing the size
+   * of the message before the data, then making sure to limit the input to
+   * that size on the receiving end (e.g. by wrapping the InputStream in one
+   * which limits the input).  Alternatively, just use
+   * {@link #writeDelimitedTo(OutputStream)}.
+   */
+  void writeTo(OutputStream output) throws IOException;
+
+  /**
+   * Like {@link #writeTo(OutputStream)}, but writes the size of the message
+   * as a varint before writing the data.  This allows more data to be written
+   * to the stream after the message without the need to delimit the message
+   * data yourself.  Use {@link Builder#mergeDelimitedFrom(InputStream)} (or
+   * the static method {@code YourMessageType.parseDelimitedFrom(InputStream)})
+   * to parse messages written by this method.
+   */
+  void writeDelimitedTo(OutputStream output) throws IOException;
+
+  // =================================================================
+  // Builders
+
+  /**
+   * Constructs a new builder for a message of the same type as this message.
+   */
+  Builder newBuilderForType();
+
+  /**
+   * Constructs a builder initialized with the current message.  Use this to
+   * derive a new message from the current one.
+   */
+  Builder toBuilder();
+
+  /**
+   * Abstract interface implemented by Protocol Message builders.
+   */
+  interface Builder extends Cloneable {
+    /** Resets all fields to their default values. */
+    Builder clear();
+
+    /**
+     * Construct the final message.  Once this is called, the Builder is no
+     * longer valid, and calling any other method will result in undefined
+     * behavior and may throw a NullPointerException.  If you need to continue
+     * working with the builder after calling {@code build()}, {@code clone()}
+     * it first.
+     * @throws UninitializedMessageException The message is missing one or more
+     *         required fields (i.e. {@link #isInitialized()} returns false).
+     *         Use {@link #buildPartial()} to bypass this check.
+     */
+    MessageLite build();
+
+    /**
+     * Like {@link #build()}, but does not throw an exception if the message
+     * is missing required fields.  Instead, a partial message is returned.
+     * Once this is called, the Builder is no longer valid, and calling any
+     * will result in undefined behavior and may throw a NullPointerException.
+     *
+     * If you need to continue working with the builder after calling
+     * {@code buildPartial()}, {@code clone()} it first.
+     */
+    MessageLite buildPartial();
+
+    /**
+     * Clones the Builder.
+     * @see Object#clone()
+     */
+    Builder clone();
+
+    /**
+     * Returns true if all required fields in the message and all embedded
+     * messages are set, false otherwise.
+     */
+    boolean isInitialized();
+
+    /**
+     * Parses a message of this type from the input and merges it with this
+     * message, as if using {@link Builder#mergeFrom(MessageLite)}.
+     *
+     * <p>Warning:  This does not verify that all required fields are present in
+     * the input message.  If you call {@link #build()} without setting all
+     * required fields, it will throw an {@link UninitializedMessageException},
+     * which is a {@code RuntimeException} and thus might not be caught.  There
+     * are a few good ways to deal with this:
+     * <ul>
+     *   <li>Call {@link #isInitialized()} to verify that all required fields
+     *       are set before building.
+     *   <li>Parse the message separately using one of the static
+     *       {@code parseFrom} methods, then use {@link #mergeFrom(MessageLite)}
+     *       to merge it with this one.  {@code parseFrom} will throw an
+     *       {@link InvalidProtocolBufferException} (an {@code IOException})
+     *       if some required fields are missing.
+     *   <li>Use {@code buildPartial()} to build, which ignores missing
+     *       required fields.
+     * </ul>
+     *
+     * <p>Note:  The caller should call
+     * {@link CodedInputStream#checkLastTagWas(int)} after calling this to
+     * verify that the last tag seen was the appropriate end-group tag,
+     * or zero for EOF.
+     */
+    Builder mergeFrom(CodedInputStream input) throws IOException;
+
+    /**
+     * Like {@link Builder#mergeFrom(CodedInputStream)}, but also
+     * parses extensions.  The extensions that you want to be able to parse
+     * must be registered in {@code extensionRegistry}.  Extensions not in
+     * the registry will be treated as unknown fields.
+     */
+    Builder mergeFrom(CodedInputStream input,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws IOException;
+
+    /**
+     * Get the message's type's default instance.
+     * See {@link MessageLite#getDefaultInstanceForType()}.
+     */
+    MessageLite getDefaultInstanceForType();
+
+    // ---------------------------------------------------------------
+    // Convenience methods.
+
+    /**
+     * Parse {@code data} as a message of this type and merge it with the
+     * message being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream)}.
+     */
+    Builder mergeFrom(ByteString data) throws InvalidProtocolBufferException;
+
+    /**
+     * Parse {@code data} as a message of this type and merge it with the
+     * message being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream,ExtensionRegistry)}.
+     */
+    Builder mergeFrom(ByteString data,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws InvalidProtocolBufferException;
+
+    /**
+     * Parse {@code data} as a message of this type and merge it with the
+     * message being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream)}.
+     */
+    Builder mergeFrom(byte[] data) throws InvalidProtocolBufferException;
+
+    /**
+     * Parse {@code data} as a message of this type and merge it with the
+     * message being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream)}.
+     */
+    Builder mergeFrom(byte[] data, int off, int len)
+                      throws InvalidProtocolBufferException;
+
+    /**
+     * Parse {@code data} as a message of this type and merge it with the
+     * message being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream,ExtensionRegistry)}.
+     */
+    Builder mergeFrom(byte[] data,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws InvalidProtocolBufferException;
+
+    /**
+     * Parse {@code data} as a message of this type and merge it with the
+     * message being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream,ExtensionRegistry)}.
+     */
+    Builder mergeFrom(byte[] data, int off, int len,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws InvalidProtocolBufferException;
+
+    /**
+     * Parse a message of this type from {@code input} and merge it with the
+     * message being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream)}.  Note that this method always
+     * reads the <i>entire</i> input (unless it throws an exception).  If you
+     * want it to stop earlier, you will need to wrap your input in some
+     * wrapper stream that limits reading.  Or, use
+     * {@link MessageLite#writeDelimitedTo(OutputStream)} to write your message
+     * and {@link #mergeDelimitedFrom(InputStream)} to read it.
+     * <p>
+     * Despite usually reading the entire input, this does not close the stream.
+     */
+    Builder mergeFrom(InputStream input) throws IOException;
+
+    /**
+     * Parse a message of this type from {@code input} and merge it with the
+     * message being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream,ExtensionRegistry)}.
+     */
+    Builder mergeFrom(InputStream input,
+                      ExtensionRegistryLite extensionRegistry)
+                      throws IOException;
+
+    /**
+     * Like {@link #mergeFrom(InputStream)}, but does not read until EOF.
+     * Instead, the size of the message (encoded as a varint) is read first,
+     * then the message data.  Use
+     * {@link MessageLite#writeDelimitedTo(OutputStream)} to write messages in
+     * this format.
+     */
+    Builder mergeDelimitedFrom(InputStream input)
+                               throws IOException;
+
+    /**
+     * Like {@link #mergeDelimitedFrom(InputStream)} but supporting extensions.
+     */
+    Builder mergeDelimitedFrom(InputStream input,
+                               ExtensionRegistryLite extensionRegistry)
+                               throws IOException;
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/ProtocolMessageEnum.java b/java/src/main/java/com/google/protobuf/ProtocolMessageEnum.java
new file mode 100644
index 0000000..112400f
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/ProtocolMessageEnum.java
@@ -0,0 +1,58 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.EnumDescriptor;
+import com.google.protobuf.Descriptors.EnumValueDescriptor;
+
+/**
+ * Interface of useful methods added to all enums generated by the protocol
+ * compiler.
+ */
+public interface ProtocolMessageEnum extends Internal.EnumLite {
+
+  /**
+   * Return the value's numeric value as defined in the .proto file.
+   */
+  int getNumber();
+
+  /**
+   * Return the value's descriptor, which contains information such as
+   * value name, number, and type.
+   */
+  EnumValueDescriptor getValueDescriptor();
+
+  /**
+   * Return the enum type's descriptor, which contains information
+   * about each defined value, etc.
+   */
+  EnumDescriptor getDescriptorForType();
+}
diff --git a/java/src/main/java/com/google/protobuf/RpcCallback.java b/java/src/main/java/com/google/protobuf/RpcCallback.java
new file mode 100644
index 0000000..841c88a
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/RpcCallback.java
@@ -0,0 +1,41 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * Interface for an RPC callback, normally called when an RPC completes.
+ * {@code ParameterType} is normally the method's response message type.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public interface RpcCallback<ParameterType> {
+  void run(ParameterType parameter);
+}
diff --git a/java/src/main/java/com/google/protobuf/RpcChannel.java b/java/src/main/java/com/google/protobuf/RpcChannel.java
new file mode 100644
index 0000000..204ff18
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/RpcChannel.java
@@ -0,0 +1,65 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * <p>Abstract interface for an RPC channel.  An {@code RpcChannel} represents a
+ * communication line to a {@link Service} which can be used to call that
+ * {@link Service}'s methods.  The {@link Service} may be running on another
+ * machine.  Normally, you should not call an {@code RpcChannel} directly, but
+ * instead construct a stub {@link Service} wrapping it.  Example:
+ *
+ * <pre>
+ *   RpcChannel channel = rpcImpl.newChannel("remotehost.example.com:1234");
+ *   RpcController controller = rpcImpl.newController();
+ *   MyService service = MyService.newStub(channel);
+ *   service.myMethod(controller, request, callback);
+ * </pre>
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public interface RpcChannel {
+  /**
+   * Call the given method of the remote service.  This method is similar to
+   * {@code Service.callMethod()} with one important difference:  the caller
+   * decides the types of the {@code Message} objects, not the callee.  The
+   * request may be of any type as long as
+   * {@code request.getDescriptor() == method.getInputType()}.
+   * The response passed to the callback will be of the same type as
+   * {@code responsePrototype} (which must have
+   * {@code getDescriptor() == method.getOutputType()}).
+   */
+  void callMethod(Descriptors.MethodDescriptor method,
+                  RpcController controller,
+                  Message request,
+                  Message responsePrototype,
+                  RpcCallback<Message> done);
+}
diff --git a/java/src/main/java/com/google/protobuf/RpcController.java b/java/src/main/java/com/google/protobuf/RpcController.java
new file mode 100644
index 0000000..a017422
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/RpcController.java
@@ -0,0 +1,112 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * <p>An {@code RpcController} mediates a single method call.  The primary
+ * purpose of the controller is to provide a way to manipulate settings
+ * specific to the RPC implementation and to find out about RPC-level errors.
+ *
+ * <p>The methods provided by the {@code RpcController} interface are intended
+ * to be a "least common denominator" set of features which we expect all
+ * implementations to support.  Specific implementations may provide more
+ * advanced features (e.g. deadline propagation).
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public interface RpcController {
+  // -----------------------------------------------------------------
+  // These calls may be made from the client side only.  Their results
+  // are undefined on the server side (may throw RuntimeExceptions).
+
+  /**
+   * Resets the RpcController to its initial state so that it may be reused in
+   * a new call.  This can be called from the client side only.  It must not
+   * be called while an RPC is in progress.
+   */
+  void reset();
+
+  /**
+   * After a call has finished, returns true if the call failed.  The possible
+   * reasons for failure depend on the RPC implementation.  {@code failed()}
+   * most only be called on the client side, and must not be called before a
+   * call has finished.
+   */
+  boolean failed();
+
+  /**
+   * If {@code failed()} is {@code true}, returns a human-readable description
+   * of the error.
+   */
+  String errorText();
+
+  /**
+   * Advises the RPC system that the caller desires that the RPC call be
+   * canceled.  The RPC system may cancel it immediately, may wait awhile and
+   * then cancel it, or may not even cancel the call at all.  If the call is
+   * canceled, the "done" callback will still be called and the RpcController
+   * will indicate that the call failed at that time.
+   */
+  void startCancel();
+
+  // -----------------------------------------------------------------
+  // These calls may be made from the server side only.  Their results
+  // are undefined on the client side (may throw RuntimeExceptions).
+
+  /**
+   * Causes {@code failed()} to return true on the client side.  {@code reason}
+   * will be incorporated into the message returned by {@code errorText()}.
+   * If you find you need to return machine-readable information about
+   * failures, you should incorporate it into your response protocol buffer
+   * and should NOT call {@code setFailed()}.
+   */
+  void setFailed(String reason);
+
+  /**
+   * If {@code true}, indicates that the client canceled the RPC, so the server
+   * may as well give up on replying to it.  This method must be called on the
+   * server side only.  The server should still call the final "done" callback.
+   */
+  boolean isCanceled();
+
+  /**
+   * Asks that the given callback be called when the RPC is canceled.  The
+   * parameter passed to the callback will always be {@code null}.  The
+   * callback will always be called exactly once.  If the RPC completes without
+   * being canceled, the callback will be called after completion.  If the RPC
+   * has already been canceled when NotifyOnCancel() is called, the callback
+   * will be called immediately.
+   *
+   * <p>{@code notifyOnCancel()} must be called no more than once per request.
+   * It must be called on the server side only.
+   */
+  void notifyOnCancel(RpcCallback<Object> callback);
+}
diff --git a/java/src/main/java/com/google/protobuf/RpcUtil.java b/java/src/main/java/com/google/protobuf/RpcUtil.java
new file mode 100644
index 0000000..b1b959a
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/RpcUtil.java
@@ -0,0 +1,135 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * Grab-bag of utility functions useful when dealing with RPCs.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class RpcUtil {
+  private RpcUtil() {}
+
+  /**
+   * Take an {@code RpcCallback<Message>} and convert it to an
+   * {@code RpcCallback} accepting a specific message type.  This is always
+   * type-safe (parameter type contravariance).
+   */
+  @SuppressWarnings("unchecked")
+  public static <Type extends Message> RpcCallback<Type>
+  specializeCallback(final RpcCallback<Message> originalCallback) {
+    return (RpcCallback<Type>)originalCallback;
+    // The above cast works, but only due to technical details of the Java
+    // implementation.  A more theoretically correct -- but less efficient --
+    // implementation would be as follows:
+    //   return new RpcCallback<Type>() {
+    //     public void run(Type parameter) {
+    //       originalCallback.run(parameter);
+    //     }
+    //   };
+  }
+
+  /**
+   * Take an {@code RpcCallback} accepting a specific message type and convert
+   * it to an {@code RpcCallback<Message>}.  The generalized callback will
+   * accept any message object which has the same descriptor, and will convert
+   * it to the correct class before calling the original callback.  However,
+   * if the generalized callback is given a message with a different descriptor,
+   * an exception will be thrown.
+   */
+  public static <Type extends Message>
+  RpcCallback<Message> generalizeCallback(
+      final RpcCallback<Type> originalCallback,
+      final Class<Type> originalClass,
+      final Type defaultInstance) {
+    return new RpcCallback<Message>() {
+      public void run(final Message parameter) {
+        Type typedParameter;
+        try {
+          typedParameter = originalClass.cast(parameter);
+        } catch (ClassCastException ignored) {
+          typedParameter = copyAsType(defaultInstance, parameter);
+        }
+        originalCallback.run(typedParameter);
+      }
+    };
+  }
+
+  /**
+   * Creates a new message of type "Type" which is a copy of "source".  "source"
+   * must have the same descriptor but may be a different class (e.g.
+   * DynamicMessage).
+   */
+  @SuppressWarnings("unchecked")
+  private static <Type extends Message> Type copyAsType(
+      final Type typeDefaultInstance, final Message source) {
+    return (Type)typeDefaultInstance.newBuilderForType()
+                                    .mergeFrom(source)
+                                    .build();
+  }
+
+  /**
+   * Creates a callback which can only be called once.  This may be useful for
+   * security, when passing a callback to untrusted code:  most callbacks do
+   * not expect to be called more than once, so doing so may expose bugs if it
+   * is not prevented.
+   */
+  public static <ParameterType>
+    RpcCallback<ParameterType> newOneTimeCallback(
+      final RpcCallback<ParameterType> originalCallback) {
+    return new RpcCallback<ParameterType>() {
+      private boolean alreadyCalled = false;
+
+      public void run(final ParameterType parameter) {
+        synchronized(this) {
+          if (alreadyCalled) {
+            throw new AlreadyCalledException();
+          }
+          alreadyCalled = true;
+        }
+
+        originalCallback.run(parameter);
+      }
+    };
+  }
+
+  /**
+   * Exception thrown when a one-time callback is called more than once.
+   */
+  public static final class AlreadyCalledException extends RuntimeException {
+    private static final long serialVersionUID = 5469741279507848266L;
+
+    public AlreadyCalledException() {
+      super("This RpcCallback was already called and cannot be called " +
+            "multiple times.");
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/Service.java b/java/src/main/java/com/google/protobuf/Service.java
new file mode 100644
index 0000000..33bcfd3
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/Service.java
@@ -0,0 +1,111 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * Abstract base interface for protocol-buffer-based RPC services.  Services
+ * themselves are abstract classes (implemented either by servers or as
+ * stubs), but they subclass this base interface.  The methods of this
+ * interface can be used to call the methods of the service without knowing
+ * its exact type at compile time (analogous to the Message interface).
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public interface Service {
+  /**
+   * Get the {@code ServiceDescriptor} describing this service and its methods.
+   */
+  Descriptors.ServiceDescriptor getDescriptorForType();
+
+  /**
+   * <p>Call a method of the service specified by MethodDescriptor.  This is
+   * normally implemented as a simple {@code switch()} that calls the standard
+   * definitions of the service's methods.
+   *
+   * <p>Preconditions:
+   * <ul>
+   *   <li>{@code method.getService() == getDescriptorForType()}
+   *   <li>{@code request} is of the exact same class as the object returned by
+   *       {@code getRequestPrototype(method)}.
+   *   <li>{@code controller} is of the correct type for the RPC implementation
+   *       being used by this Service.  For stubs, the "correct type" depends
+   *       on the RpcChannel which the stub is using.  Server-side Service
+   *       implementations are expected to accept whatever type of
+   *       {@code RpcController} the server-side RPC implementation uses.
+   * </ul>
+   *
+   * <p>Postconditions:
+   * <ul>
+   *   <li>{@code done} will be called when the method is complete.  This may be
+   *       before {@code callMethod()} returns or it may be at some point in
+   *       the future.
+   *   <li>The parameter to {@code done} is the response.  It must be of the
+   *       exact same type as would be returned by
+   *       {@code getResponsePrototype(method)}.
+   *   <li>If the RPC failed, the parameter to {@code done} will be
+   *       {@code null}.  Further details about the failure can be found by
+   *       querying {@code controller}.
+   * </ul>
+   */
+  void callMethod(Descriptors.MethodDescriptor method,
+                  RpcController controller,
+                  Message request,
+                  RpcCallback<Message> done);
+
+  /**
+   * <p>{@code callMethod()} requires that the request passed in is of a
+   * particular subclass of {@code Message}.  {@code getRequestPrototype()}
+   * gets the default instances of this type for a given method.  You can then
+   * call {@code Message.newBuilderForType()} on this instance to
+   * construct a builder to build an object which you can then pass to
+   * {@code callMethod()}.
+   *
+   * <p>Example:
+   * <pre>
+   *   MethodDescriptor method =
+   *     service.getDescriptorForType().findMethodByName("Foo");
+   *   Message request =
+   *     stub.getRequestPrototype(method).newBuilderForType()
+   *         .mergeFrom(input).build();
+   *   service.callMethod(method, request, callback);
+   * </pre>
+   */
+  Message getRequestPrototype(Descriptors.MethodDescriptor method);
+
+  /**
+   * Like {@code getRequestPrototype()}, but gets a prototype of the response
+   * message.  {@code getResponsePrototype()} is generally not needed because
+   * the {@code Service} implementation constructs the response message itself,
+   * but it may be useful in some cases to know ahead of time what type of
+   * object will be returned.
+   */
+  Message getResponsePrototype(Descriptors.MethodDescriptor method);
+}
diff --git a/java/src/main/java/com/google/protobuf/ServiceException.java b/java/src/main/java/com/google/protobuf/ServiceException.java
new file mode 100644
index 0000000..c043a77
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/ServiceException.java
@@ -0,0 +1,44 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * Thrown by blocking RPC methods when a failure occurs.
+ *
+ * @author cpovirk@google.com (Chris Povirk)
+ */
+public final class ServiceException extends Exception {
+  private static final long serialVersionUID = -1219262335729891920L;
+
+  public ServiceException(final String message) {
+    super(message);
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/TextFormat.java b/java/src/main/java/com/google/protobuf/TextFormat.java
new file mode 100644
index 0000000..a855720
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/TextFormat.java
@@ -0,0 +1,1323 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+import com.google.protobuf.Descriptors.EnumDescriptor;
+import com.google.protobuf.Descriptors.EnumValueDescriptor;
+
+import java.io.IOException;
+import java.nio.CharBuffer;
+import java.math.BigInteger;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Provide ascii text parsing and formatting support for proto2 instances.
+ * The implementation largely follows google/protobuf/text_format.cc.
+ *
+ * @author wenboz@google.com Wenbo Zhu
+ * @author kenton@google.com Kenton Varda
+ */
+public final class TextFormat {
+  private TextFormat() {
+  }
+
+  /**
+   * Outputs a textual representation of the Protocol Message supplied into
+   * the parameter output. (This representation is the new version of the
+   * classic "ProtocolPrinter" output from the original Protocol Buffer system)
+   */
+  public static void print(final Message message, final Appendable output)
+                           throws IOException {
+    final TextGenerator generator = new TextGenerator(output);
+    print(message, generator);
+  }
+
+  /** Outputs a textual representation of {@code fields} to {@code output}. */
+  public static void print(final UnknownFieldSet fields,
+                           final Appendable output)
+                           throws IOException {
+    final TextGenerator generator = new TextGenerator(output);
+    printUnknownFields(fields, generator);
+  }
+
+  /**
+   * Like {@code print()}, but writes directly to a {@code String} and
+   * returns it.
+   */
+  public static String printToString(final Message message) {
+    try {
+      final StringBuilder text = new StringBuilder();
+      print(message, text);
+      return text.toString();
+    } catch (IOException e) {
+      throw new RuntimeException(
+        "Writing to a StringBuilder threw an IOException (should never " +
+        "happen).", e);
+    }
+  }
+
+  /**
+   * Like {@code print()}, but writes directly to a {@code String} and
+   * returns it.
+   */
+  public static String printToString(final UnknownFieldSet fields) {
+    try {
+      final StringBuilder text = new StringBuilder();
+      print(fields, text);
+      return text.toString();
+    } catch (IOException e) {
+      throw new RuntimeException(
+        "Writing to a StringBuilder threw an IOException (should never " +
+        "happen).", e);
+    }
+  }
+
+  private static void print(final Message message,
+                            final TextGenerator generator)
+      throws IOException {
+    for (final Map.Entry<FieldDescriptor, Object> field :
+         message.getAllFields().entrySet()) {
+      printField(field.getKey(), field.getValue(), generator);
+    }
+    printUnknownFields(message.getUnknownFields(), generator);
+  }
+  
+  public static void printField(final FieldDescriptor field,
+                                final Object value,
+                                final Appendable output)
+                                throws IOException {
+    final TextGenerator generator = new TextGenerator(output);
+    printField(field, value, generator);
+  }
+
+  public static String printFieldToString(final FieldDescriptor field,
+                                          final Object value) {
+    try {
+      final StringBuilder text = new StringBuilder();
+      printField(field, value, text);
+      return text.toString();
+    } catch (IOException e) {
+      throw new RuntimeException(
+        "Writing to a StringBuilder threw an IOException (should never " +
+        "happen).", e);  
+    }
+  }
+  
+  private static void printField(final FieldDescriptor field,
+                                final Object value,
+                                final TextGenerator generator)
+                                throws IOException {
+    if (field.isRepeated()) {
+      // Repeated field.  Print each element.
+      for (final Object element : (List) value) {
+        printSingleField(field, element, generator);
+      }
+    } else {
+      printSingleField(field, value, generator);
+    }
+  }
+
+  private static void printSingleField(final FieldDescriptor field,
+                                       final Object value,
+                                       final TextGenerator generator)
+                                       throws IOException {
+    if (field.isExtension()) {
+      generator.print("[");
+      // We special-case MessageSet elements for compatibility with proto1.
+      if (field.getContainingType().getOptions().getMessageSetWireFormat()
+          && (field.getType() == FieldDescriptor.Type.MESSAGE)
+          && (field.isOptional())
+          // object equality
+          && (field.getExtensionScope() == field.getMessageType())) {
+        generator.print(field.getMessageType().getFullName());
+      } else {
+        generator.print(field.getFullName());
+      }
+      generator.print("]");
+    } else {
+      if (field.getType() == FieldDescriptor.Type.GROUP) {
+        // Groups must be serialized with their original capitalization.
+        generator.print(field.getMessageType().getName());
+      } else {
+        generator.print(field.getName());
+      }
+    }
+
+    if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+      generator.print(" {\n");
+      generator.indent();
+    } else {
+      generator.print(": ");
+    }
+
+    printFieldValue(field, value, generator);
+
+    if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+      generator.outdent();
+      generator.print("}");
+    }
+    generator.print("\n");
+  }
+
+  private static void printFieldValue(final FieldDescriptor field,
+                                      final Object value,
+                                      final TextGenerator generator)
+                                      throws IOException {
+    switch (field.getType()) {
+      case INT32:
+      case INT64:
+      case SINT32:
+      case SINT64:
+      case SFIXED32:
+      case SFIXED64:
+      case FLOAT:
+      case DOUBLE:
+      case BOOL:
+        // Good old toString() does what we want for these types.
+        generator.print(value.toString());
+        break;
+
+      case UINT32:
+      case FIXED32:
+        generator.print(unsignedToString((Integer) value));
+        break;
+
+      case UINT64:
+      case FIXED64:
+        generator.print(unsignedToString((Long) value));
+        break;
+
+      case STRING:
+        generator.print("\"");
+        generator.print(escapeText((String) value));
+        generator.print("\"");
+        break;
+
+      case BYTES:
+        generator.print("\"");
+        generator.print(escapeBytes((ByteString) value));
+        generator.print("\"");
+        break;
+
+      case ENUM:
+        generator.print(((EnumValueDescriptor) value).getName());
+        break;
+
+      case MESSAGE:
+      case GROUP:
+        print((Message) value, generator);
+        break;
+    }
+  }
+
+  private static void printUnknownFields(final UnknownFieldSet unknownFields,
+                                         final TextGenerator generator)
+                                         throws IOException {
+    for (final Map.Entry<Integer, UnknownFieldSet.Field> entry :
+         unknownFields.asMap().entrySet()) {
+      final String prefix = entry.getKey().toString() + ": ";
+      final UnknownFieldSet.Field field = entry.getValue();
+
+      for (final long value : field.getVarintList()) {
+        generator.print(entry.getKey().toString());
+        generator.print(": ");
+        generator.print(unsignedToString(value));
+        generator.print("\n");
+      }
+      for (final int value : field.getFixed32List()) {
+        generator.print(entry.getKey().toString());
+        generator.print(": ");
+        generator.print(String.format((Locale) null, "0x%08x", value));
+        generator.print("\n");
+      }
+      for (final long value : field.getFixed64List()) {
+        generator.print(entry.getKey().toString());
+        generator.print(": ");
+        generator.print(String.format((Locale) null, "0x%016x", value));
+        generator.print("\n");
+      }
+      for (final ByteString value : field.getLengthDelimitedList()) {
+        generator.print(entry.getKey().toString());
+        generator.print(": \"");
+        generator.print(escapeBytes(value));
+        generator.print("\"\n");
+      }
+      for (final UnknownFieldSet value : field.getGroupList()) {
+        generator.print(entry.getKey().toString());
+        generator.print(" {\n");
+        generator.indent();
+        printUnknownFields(value, generator);
+        generator.outdent();
+        generator.print("}\n");
+      }
+    }
+  }
+
+  /** Convert an unsigned 32-bit integer to a string. */
+  private static String unsignedToString(final int value) {
+    if (value >= 0) {
+      return Integer.toString(value);
+    } else {
+      return Long.toString(((long) value) & 0x00000000FFFFFFFFL);
+    }
+  }
+
+  /** Convert an unsigned 64-bit integer to a string. */
+  private static String unsignedToString(final long value) {
+    if (value >= 0) {
+      return Long.toString(value);
+    } else {
+      // Pull off the most-significant bit so that BigInteger doesn't think
+      // the number is negative, then set it again using setBit().
+      return BigInteger.valueOf(value & 0x7FFFFFFFFFFFFFFFL)
+                       .setBit(63).toString();
+    }
+  }
+
+  /**
+   * An inner class for writing text to the output stream.
+   */
+  private static final class TextGenerator {
+    private Appendable output;
+    private boolean atStartOfLine = true;
+    private final StringBuilder indent = new StringBuilder();
+
+    private TextGenerator(final Appendable output) {
+      this.output = output;
+    }
+
+    /**
+     * Indent text by two spaces.  After calling Indent(), two spaces will be
+     * inserted at the beginning of each line of text.  Indent() may be called
+     * multiple times to produce deeper indents.
+     */
+    public void indent() {
+      indent.append("  ");
+    }
+
+    /**
+     * Reduces the current indent level by two spaces, or crashes if the indent
+     * level is zero.
+     */
+    public void outdent() {
+      final int length = indent.length();
+      if (length == 0) {
+        throw new IllegalArgumentException(
+            " Outdent() without matching Indent().");
+      }
+      indent.delete(length - 2, length);
+    }
+
+    /**
+     * Print text to the output stream.
+     */
+    public void print(final CharSequence text) throws IOException {
+      final int size = text.length();
+      int pos = 0;
+
+      for (int i = 0; i < size; i++) {
+        if (text.charAt(i) == '\n') {
+          write(text.subSequence(pos, size), i - pos + 1);
+          pos = i + 1;
+          atStartOfLine = true;
+        }
+      }
+      write(text.subSequence(pos, size), size - pos);
+    }
+
+    private void write(final CharSequence data, final int size)
+                       throws IOException {
+      if (size == 0) {
+        return;
+      }
+      if (atStartOfLine) {
+        atStartOfLine = false;
+        output.append(indent);
+      }
+      output.append(data);
+    }
+  }
+
+  // =================================================================
+  // Parsing
+
+  /**
+   * Represents a stream of tokens parsed from a {@code String}.
+   *
+   * <p>The Java standard library provides many classes that you might think
+   * would be useful for implementing this, but aren't.  For example:
+   *
+   * <ul>
+   * <li>{@code java.io.StreamTokenizer}:  This almost does what we want -- or,
+   *   at least, something that would get us close to what we want -- except
+   *   for one fatal flaw:  It automatically un-escapes strings using Java
+   *   escape sequences, which do not include all the escape sequences we
+   *   need to support (e.g. '\x').
+   * <li>{@code java.util.Scanner}:  This seems like a great way at least to
+   *   parse regular expressions out of a stream (so we wouldn't have to load
+   *   the entire input into a single string before parsing).  Sadly,
+   *   {@code Scanner} requires that tokens be delimited with some delimiter.
+   *   Thus, although the text "foo:" should parse to two tokens ("foo" and
+   *   ":"), {@code Scanner} would recognize it only as a single token.
+   *   Furthermore, {@code Scanner} provides no way to inspect the contents
+   *   of delimiters, making it impossible to keep track of line and column
+   *   numbers.
+   * </ul>
+   *
+   * <p>Luckily, Java's regular expression support does manage to be useful to
+   * us.  (Barely:  We need {@code Matcher.usePattern()}, which is new in
+   * Java 1.5.)  So, we can use that, at least.  Unfortunately, this implies
+   * that we need to have the entire input in one contiguous string.
+   */
+  private static final class Tokenizer {
+    private final CharSequence text;
+    private final Matcher matcher;
+    private String currentToken;
+
+    // The character index within this.text at which the current token begins.
+    private int pos = 0;
+
+    // The line and column numbers of the current token.
+    private int line = 0;
+    private int column = 0;
+
+    // The line and column numbers of the previous token (allows throwing
+    // errors *after* consuming).
+    private int previousLine = 0;
+    private int previousColumn = 0;
+
+    // We use possesive quantifiers (*+ and ++) because otherwise the Java
+    // regex matcher has stack overflows on large inputs.
+    private static final Pattern WHITESPACE =
+      Pattern.compile("(\\s|(#.*$))++", Pattern.MULTILINE);
+    private static final Pattern TOKEN = Pattern.compile(
+      "[a-zA-Z_][0-9a-zA-Z_+-]*+|" +                // an identifier
+      "[0-9+-][0-9a-zA-Z_.+-]*+|" +                 // a number
+      "\"([^\"\n\\\\]|\\\\.)*+(\"|\\\\?$)|" +       // a double-quoted string
+      "\'([^\"\n\\\\]|\\\\.)*+(\'|\\\\?$)",         // a single-quoted string
+      Pattern.MULTILINE);
+
+    private static final Pattern DOUBLE_INFINITY = Pattern.compile(
+      "-?inf(inity)?",
+      Pattern.CASE_INSENSITIVE);
+    private static final Pattern FLOAT_INFINITY = Pattern.compile(
+      "-?inf(inity)?f?",
+      Pattern.CASE_INSENSITIVE);
+    private static final Pattern FLOAT_NAN = Pattern.compile(
+      "nanf?",
+      Pattern.CASE_INSENSITIVE);
+
+    /** Construct a tokenizer that parses tokens from the given text. */
+    private Tokenizer(final CharSequence text) {
+      this.text = text;
+      this.matcher = WHITESPACE.matcher(text);
+      skipWhitespace();
+      nextToken();
+    }
+
+    /** Are we at the end of the input? */
+    public boolean atEnd() {
+      return currentToken.length() == 0;
+    }
+
+    /** Advance to the next token. */
+    public void nextToken() {
+      previousLine = line;
+      previousColumn = column;
+
+      // Advance the line counter to the current position.
+      while (pos < matcher.regionStart()) {
+        if (text.charAt(pos) == '\n') {
+          ++line;
+          column = 0;
+        } else {
+          ++column;
+        }
+        ++pos;
+      }
+
+      // Match the next token.
+      if (matcher.regionStart() == matcher.regionEnd()) {
+        // EOF
+        currentToken = "";
+      } else {
+        matcher.usePattern(TOKEN);
+        if (matcher.lookingAt()) {
+          currentToken = matcher.group();
+          matcher.region(matcher.end(), matcher.regionEnd());
+        } else {
+          // Take one character.
+          currentToken = String.valueOf(text.charAt(pos));
+          matcher.region(pos + 1, matcher.regionEnd());
+        }
+
+        skipWhitespace();
+      }
+    }
+
+    /**
+     * Skip over any whitespace so that the matcher region starts at the next
+     * token.
+     */
+    private void skipWhitespace() {
+      matcher.usePattern(WHITESPACE);
+      if (matcher.lookingAt()) {
+        matcher.region(matcher.end(), matcher.regionEnd());
+      }
+    }
+
+    /**
+     * If the next token exactly matches {@code token}, consume it and return
+     * {@code true}.  Otherwise, return {@code false} without doing anything.
+     */
+    public boolean tryConsume(final String token) {
+      if (currentToken.equals(token)) {
+        nextToken();
+        return true;
+      } else {
+        return false;
+      }
+    }
+
+    /**
+     * If the next token exactly matches {@code token}, consume it.  Otherwise,
+     * throw a {@link ParseException}.
+     */
+    public void consume(final String token) throws ParseException {
+      if (!tryConsume(token)) {
+        throw parseException("Expected \"" + token + "\".");
+      }
+    }
+
+    /**
+     * Returns {@code true} if the next token is an integer, but does
+     * not consume it.
+     */
+    public boolean lookingAtInteger() {
+      if (currentToken.length() == 0) {
+        return false;
+      }
+
+      final char c = currentToken.charAt(0);
+      return ('0' <= c && c <= '9') ||
+             c == '-' || c == '+';
+    }
+
+    /**
+     * If the next token is an identifier, consume it and return its value.
+     * Otherwise, throw a {@link ParseException}.
+     */
+    public String consumeIdentifier() throws ParseException {
+      for (int i = 0; i < currentToken.length(); i++) {
+        final char c = currentToken.charAt(i);
+        if (('a' <= c && c <= 'z') ||
+            ('A' <= c && c <= 'Z') ||
+            ('0' <= c && c <= '9') ||
+            (c == '_') || (c == '.')) {
+          // OK
+        } else {
+          throw parseException("Expected identifier.");
+        }
+      }
+
+      final String result = currentToken;
+      nextToken();
+      return result;
+    }
+
+    /**
+     * If the next token is a 32-bit signed integer, consume it and return its
+     * value.  Otherwise, throw a {@link ParseException}.
+     */
+    public int consumeInt32() throws ParseException {
+      try {
+        final int result = parseInt32(currentToken);
+        nextToken();
+        return result;
+      } catch (NumberFormatException e) {
+        throw integerParseException(e);
+      }
+    }
+
+    /**
+     * If the next token is a 32-bit unsigned integer, consume it and return its
+     * value.  Otherwise, throw a {@link ParseException}.
+     */
+    public int consumeUInt32() throws ParseException {
+      try {
+        final int result = parseUInt32(currentToken);
+        nextToken();
+        return result;
+      } catch (NumberFormatException e) {
+        throw integerParseException(e);
+      }
+    }
+
+    /**
+     * If the next token is a 64-bit signed integer, consume it and return its
+     * value.  Otherwise, throw a {@link ParseException}.
+     */
+    public long consumeInt64() throws ParseException {
+      try {
+        final long result = parseInt64(currentToken);
+        nextToken();
+        return result;
+      } catch (NumberFormatException e) {
+        throw integerParseException(e);
+      }
+    }
+
+    /**
+     * If the next token is a 64-bit unsigned integer, consume it and return its
+     * value.  Otherwise, throw a {@link ParseException}.
+     */
+    public long consumeUInt64() throws ParseException {
+      try {
+        final long result = parseUInt64(currentToken);
+        nextToken();
+        return result;
+      } catch (NumberFormatException e) {
+        throw integerParseException(e);
+      }
+    }
+
+    /**
+     * If the next token is a double, consume it and return its value.
+     * Otherwise, throw a {@link ParseException}.
+     */
+    public double consumeDouble() throws ParseException {
+      // We need to parse infinity and nan separately because
+      // Double.parseDouble() does not accept "inf", "infinity", or "nan".
+      if (DOUBLE_INFINITY.matcher(currentToken).matches()) {
+        final boolean negative = currentToken.startsWith("-");
+        nextToken();
+        return negative ? Double.NEGATIVE_INFINITY : Double.POSITIVE_INFINITY;
+      }
+      if (currentToken.equalsIgnoreCase("nan")) {
+        nextToken();
+        return Double.NaN;
+      }
+      try {
+        final double result = Double.parseDouble(currentToken);
+        nextToken();
+        return result;
+      } catch (NumberFormatException e) {
+        throw floatParseException(e);
+      }
+    }
+
+    /**
+     * If the next token is a float, consume it and return its value.
+     * Otherwise, throw a {@link ParseException}.
+     */
+    public float consumeFloat() throws ParseException {
+      // We need to parse infinity and nan separately because
+      // Float.parseFloat() does not accept "inf", "infinity", or "nan".
+      if (FLOAT_INFINITY.matcher(currentToken).matches()) {
+        final boolean negative = currentToken.startsWith("-");
+        nextToken();
+        return negative ? Float.NEGATIVE_INFINITY : Float.POSITIVE_INFINITY;
+      }
+      if (FLOAT_NAN.matcher(currentToken).matches()) {
+        nextToken();
+        return Float.NaN;
+      }
+      try {
+        final float result = Float.parseFloat(currentToken);
+        nextToken();
+        return result;
+      } catch (NumberFormatException e) {
+        throw floatParseException(e);
+      }
+    }
+
+    /**
+     * If the next token is a boolean, consume it and return its value.
+     * Otherwise, throw a {@link ParseException}.
+     */
+    public boolean consumeBoolean() throws ParseException {
+      if (currentToken.equals("true")) {
+        nextToken();
+        return true;
+      } else if (currentToken.equals("false")) {
+        nextToken();
+        return false;
+      } else {
+        throw parseException("Expected \"true\" or \"false\".");
+      }
+    }
+
+    /**
+     * If the next token is a string, consume it and return its (unescaped)
+     * value.  Otherwise, throw a {@link ParseException}.
+     */
+    public String consumeString() throws ParseException {
+      return consumeByteString().toStringUtf8();
+    }
+
+    /**
+     * If the next token is a string, consume it, unescape it as a
+     * {@link ByteString}, and return it.  Otherwise, throw a
+     * {@link ParseException}.
+     */
+    public ByteString consumeByteString() throws ParseException {
+      final char quote = currentToken.length() > 0 ? currentToken.charAt(0)
+                                                   : '\0';
+      if (quote != '\"' && quote != '\'') {
+        throw parseException("Expected string.");
+      }
+
+      if (currentToken.length() < 2 ||
+          currentToken.charAt(currentToken.length() - 1) != quote) {
+        throw parseException("String missing ending quote.");
+      }
+
+      try {
+        final String escaped =
+            currentToken.substring(1, currentToken.length() - 1);
+        final ByteString result = unescapeBytes(escaped);
+        nextToken();
+        return result;
+      } catch (InvalidEscapeSequenceException e) {
+        throw parseException(e.getMessage());
+      }
+    }
+
+    /**
+     * Returns a {@link ParseException} with the current line and column
+     * numbers in the description, suitable for throwing.
+     */
+    public ParseException parseException(final String description) {
+      // Note:  People generally prefer one-based line and column numbers.
+      return new ParseException(
+        (line + 1) + ":" + (column + 1) + ": " + description);
+    }
+
+    /**
+     * Returns a {@link ParseException} with the line and column numbers of
+     * the previous token in the description, suitable for throwing.
+     */
+    public ParseException parseExceptionPreviousToken(
+        final String description) {
+      // Note:  People generally prefer one-based line and column numbers.
+      return new ParseException(
+        (previousLine + 1) + ":" + (previousColumn + 1) + ": " + description);
+    }
+
+    /**
+     * Constructs an appropriate {@link ParseException} for the given
+     * {@code NumberFormatException} when trying to parse an integer.
+     */
+    private ParseException integerParseException(
+        final NumberFormatException e) {
+      return parseException("Couldn't parse integer: " + e.getMessage());
+    }
+
+    /**
+     * Constructs an appropriate {@link ParseException} for the given
+     * {@code NumberFormatException} when trying to parse a float or double.
+     */
+    private ParseException floatParseException(final NumberFormatException e) {
+      return parseException("Couldn't parse number: " + e.getMessage());
+    }
+  }
+
+  /** Thrown when parsing an invalid text format message. */
+  public static class ParseException extends IOException {
+    private static final long serialVersionUID = 3196188060225107702L;
+
+    public ParseException(final String message) {
+      super(message);
+    }
+  }
+
+  /**
+   * Parse a text-format message from {@code input} and merge the contents
+   * into {@code builder}.
+   */
+  public static void merge(final Readable input,
+                           final Message.Builder builder)
+                           throws IOException {
+    merge(input, ExtensionRegistry.getEmptyRegistry(), builder);
+  }
+
+  /**
+   * Parse a text-format message from {@code input} and merge the contents
+   * into {@code builder}.
+   */
+  public static void merge(final CharSequence input,
+                           final Message.Builder builder)
+                           throws ParseException {
+    merge(input, ExtensionRegistry.getEmptyRegistry(), builder);
+  }
+
+  /**
+   * Parse a text-format message from {@code input} and merge the contents
+   * into {@code builder}.  Extensions will be recognized if they are
+   * registered in {@code extensionRegistry}.
+   */
+  public static void merge(final Readable input,
+                           final ExtensionRegistry extensionRegistry,
+                           final Message.Builder builder)
+                           throws IOException {
+    // Read the entire input to a String then parse that.
+
+    // If StreamTokenizer were not quite so crippled, or if there were a kind
+    // of Reader that could read in chunks that match some particular regex,
+    // or if we wanted to write a custom Reader to tokenize our stream, then
+    // we would not have to read to one big String.  Alas, none of these is
+    // the case.  Oh well.
+
+    merge(toStringBuilder(input), extensionRegistry, builder);
+  }
+
+  private static final int BUFFER_SIZE = 4096;
+
+  // TODO(chrisn): See if working around java.io.Reader#read(CharBuffer)
+  // overhead is worthwhile
+  private static StringBuilder toStringBuilder(final Readable input)
+      throws IOException {
+    final StringBuilder text = new StringBuilder();
+    final CharBuffer buffer = CharBuffer.allocate(BUFFER_SIZE);
+    while (true) {
+      final int n = input.read(buffer);
+      if (n == -1) {
+        break;
+      }
+      buffer.flip();
+      text.append(buffer, 0, n);
+    }
+    return text;
+  }
+
+  /**
+   * Parse a text-format message from {@code input} and merge the contents
+   * into {@code builder}.  Extensions will be recognized if they are
+   * registered in {@code extensionRegistry}.
+   */
+  public static void merge(final CharSequence input,
+                           final ExtensionRegistry extensionRegistry,
+                           final Message.Builder builder)
+                           throws ParseException {
+    final Tokenizer tokenizer = new Tokenizer(input);
+
+    while (!tokenizer.atEnd()) {
+      mergeField(tokenizer, extensionRegistry, builder);
+    }
+  }
+
+  /**
+   * Parse a single field from {@code tokenizer} and merge it into
+   * {@code builder}.
+   */
+  private static void mergeField(final Tokenizer tokenizer,
+                                 final ExtensionRegistry extensionRegistry,
+                                 final Message.Builder builder)
+                                 throws ParseException {
+    FieldDescriptor field;
+    final Descriptor type = builder.getDescriptorForType();
+    ExtensionRegistry.ExtensionInfo extension = null;
+
+    if (tokenizer.tryConsume("[")) {
+      // An extension.
+      final StringBuilder name =
+          new StringBuilder(tokenizer.consumeIdentifier());
+      while (tokenizer.tryConsume(".")) {
+        name.append('.');
+        name.append(tokenizer.consumeIdentifier());
+      }
+
+      extension = extensionRegistry.findExtensionByName(name.toString());
+
+      if (extension == null) {
+        throw tokenizer.parseExceptionPreviousToken(
+          "Extension \"" + name + "\" not found in the ExtensionRegistry.");
+      } else if (extension.descriptor.getContainingType() != type) {
+        throw tokenizer.parseExceptionPreviousToken(
+          "Extension \"" + name + "\" does not extend message type \"" +
+          type.getFullName() + "\".");
+      }
+
+      tokenizer.consume("]");
+
+      field = extension.descriptor;
+    } else {
+      final String name = tokenizer.consumeIdentifier();
+      field = type.findFieldByName(name);
+
+      // Group names are expected to be capitalized as they appear in the
+      // .proto file, which actually matches their type names, not their field
+      // names.
+      if (field == null) {
+        // Explicitly specify US locale so that this code does not break when
+        // executing in Turkey.
+        final String lowerName = name.toLowerCase(Locale.US);
+        field = type.findFieldByName(lowerName);
+        // If the case-insensitive match worked but the field is NOT a group,
+        if (field != null && field.getType() != FieldDescriptor.Type.GROUP) {
+          field = null;
+        }
+      }
+      // Again, special-case group names as described above.
+      if (field != null && field.getType() == FieldDescriptor.Type.GROUP &&
+          !field.getMessageType().getName().equals(name)) {
+        field = null;
+      }
+
+      if (field == null) {
+        throw tokenizer.parseExceptionPreviousToken(
+          "Message type \"" + type.getFullName() +
+          "\" has no field named \"" + name + "\".");
+      }
+    }
+
+    Object value = null;
+
+    if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
+      tokenizer.tryConsume(":");  // optional
+
+      final String endToken;
+      if (tokenizer.tryConsume("<")) {
+        endToken = ">";
+      } else {
+        tokenizer.consume("{");
+        endToken = "}";
+      }
+
+      final Message.Builder subBuilder;
+      if (extension == null) {
+        subBuilder = builder.newBuilderForField(field);
+      } else {
+        subBuilder = extension.defaultInstance.newBuilderForType();
+      }
+
+      while (!tokenizer.tryConsume(endToken)) {
+        if (tokenizer.atEnd()) {
+          throw tokenizer.parseException(
+            "Expected \"" + endToken + "\".");
+        }
+        mergeField(tokenizer, extensionRegistry, subBuilder);
+      }
+
+      value = subBuilder.build();
+
+    } else {
+      tokenizer.consume(":");
+
+      switch (field.getType()) {
+        case INT32:
+        case SINT32:
+        case SFIXED32:
+          value = tokenizer.consumeInt32();
+          break;
+
+        case INT64:
+        case SINT64:
+        case SFIXED64:
+          value = tokenizer.consumeInt64();
+          break;
+
+        case UINT32:
+        case FIXED32:
+          value = tokenizer.consumeUInt32();
+          break;
+
+        case UINT64:
+        case FIXED64:
+          value = tokenizer.consumeUInt64();
+          break;
+
+        case FLOAT:
+          value = tokenizer.consumeFloat();
+          break;
+
+        case DOUBLE:
+          value = tokenizer.consumeDouble();
+          break;
+
+        case BOOL:
+          value = tokenizer.consumeBoolean();
+          break;
+
+        case STRING:
+          value = tokenizer.consumeString();
+          break;
+
+        case BYTES:
+          value = tokenizer.consumeByteString();
+          break;
+
+        case ENUM:
+          final EnumDescriptor enumType = field.getEnumType();
+
+          if (tokenizer.lookingAtInteger()) {
+            final int number = tokenizer.consumeInt32();
+            value = enumType.findValueByNumber(number);
+            if (value == null) {
+              throw tokenizer.parseExceptionPreviousToken(
+                "Enum type \"" + enumType.getFullName() +
+                "\" has no value with number " + number + '.');
+            }
+          } else {
+            final String id = tokenizer.consumeIdentifier();
+            value = enumType.findValueByName(id);
+            if (value == null) {
+              throw tokenizer.parseExceptionPreviousToken(
+                "Enum type \"" + enumType.getFullName() +
+                "\" has no value named \"" + id + "\".");
+            }
+          }
+
+          break;
+
+        case MESSAGE:
+        case GROUP:
+          throw new RuntimeException("Can't get here.");
+      }
+    }
+
+    if (field.isRepeated()) {
+      builder.addRepeatedField(field, value);
+    } else {
+      builder.setField(field, value);
+    }
+  }
+
+  // =================================================================
+  // Utility functions
+  //
+  // Some of these methods are package-private because Descriptors.java uses
+  // them.
+
+  /**
+   * Escapes bytes in the format used in protocol buffer text format, which
+   * is the same as the format used for C string literals.  All bytes
+   * that are not printable 7-bit ASCII characters are escaped, as well as
+   * backslash, single-quote, and double-quote characters.  Characters for
+   * which no defined short-hand escape sequence is defined will be escaped
+   * using 3-digit octal sequences.
+   */
+  static String escapeBytes(final ByteString input) {
+    final StringBuilder builder = new StringBuilder(input.size());
+    for (int i = 0; i < input.size(); i++) {
+      final byte b = input.byteAt(i);
+      switch (b) {
+        // Java does not recognize \a or \v, apparently.
+        case 0x07: builder.append("\\a" ); break;
+        case '\b': builder.append("\\b" ); break;
+        case '\f': builder.append("\\f" ); break;
+        case '\n': builder.append("\\n" ); break;
+        case '\r': builder.append("\\r" ); break;
+        case '\t': builder.append("\\t" ); break;
+        case 0x0b: builder.append("\\v" ); break;
+        case '\\': builder.append("\\\\"); break;
+        case '\'': builder.append("\\\'"); break;
+        case '"' : builder.append("\\\""); break;
+        default:
+          if (b >= 0x20) {
+            builder.append((char) b);
+          } else {
+            builder.append('\\');
+            builder.append((char) ('0' + ((b >>> 6) & 3)));
+            builder.append((char) ('0' + ((b >>> 3) & 7)));
+            builder.append((char) ('0' + (b & 7)));
+          }
+          break;
+      }
+    }
+    return builder.toString();
+  }
+
+  /**
+   * Un-escape a byte sequence as escaped using
+   * {@link #escapeBytes(ByteString)}.  Two-digit hex escapes (starting with
+   * "\x") are also recognized.
+   */
+  static ByteString unescapeBytes(final CharSequence input)
+      throws InvalidEscapeSequenceException {
+    final byte[] result = new byte[input.length()];
+    int pos = 0;
+    for (int i = 0; i < input.length(); i++) {
+      char c = input.charAt(i);
+      if (c == '\\') {
+        if (i + 1 < input.length()) {
+          ++i;
+          c = input.charAt(i);
+          if (isOctal(c)) {
+            // Octal escape.
+            int code = digitValue(c);
+            if (i + 1 < input.length() && isOctal(input.charAt(i + 1))) {
+              ++i;
+              code = code * 8 + digitValue(input.charAt(i));
+            }
+            if (i + 1 < input.length() && isOctal(input.charAt(i + 1))) {
+              ++i;
+              code = code * 8 + digitValue(input.charAt(i));
+            }
+            result[pos++] = (byte)code;
+          } else {
+            switch (c) {
+              case 'a' : result[pos++] = 0x07; break;
+              case 'b' : result[pos++] = '\b'; break;
+              case 'f' : result[pos++] = '\f'; break;
+              case 'n' : result[pos++] = '\n'; break;
+              case 'r' : result[pos++] = '\r'; break;
+              case 't' : result[pos++] = '\t'; break;
+              case 'v' : result[pos++] = 0x0b; break;
+              case '\\': result[pos++] = '\\'; break;
+              case '\'': result[pos++] = '\''; break;
+              case '"' : result[pos++] = '\"'; break;
+
+              case 'x':
+                // hex escape
+                int code = 0;
+                if (i + 1 < input.length() && isHex(input.charAt(i + 1))) {
+                  ++i;
+                  code = digitValue(input.charAt(i));
+                } else {
+                  throw new InvalidEscapeSequenceException(
+                    "Invalid escape sequence: '\\x' with no digits");
+                }
+                if (i + 1 < input.length() && isHex(input.charAt(i + 1))) {
+                  ++i;
+                  code = code * 16 + digitValue(input.charAt(i));
+                }
+                result[pos++] = (byte)code;
+                break;
+
+              default:
+                throw new InvalidEscapeSequenceException(
+                  "Invalid escape sequence: '\\" + c + '\'');
+            }
+          }
+        } else {
+          throw new InvalidEscapeSequenceException(
+            "Invalid escape sequence: '\\' at end of string.");
+        }
+      } else {
+        result[pos++] = (byte)c;
+      }
+    }
+
+    return ByteString.copyFrom(result, 0, pos);
+  }
+
+  /**
+   * Thrown by {@link TextFormat#unescapeBytes} and
+   * {@link TextFormat#unescapeText} when an invalid escape sequence is seen.
+   */
+  static class InvalidEscapeSequenceException extends IOException {
+    private static final long serialVersionUID = -8164033650142593304L;
+
+    InvalidEscapeSequenceException(final String description) {
+      super(description);
+    }
+  }
+
+  /**
+   * Like {@link #escapeBytes(ByteString)}, but escapes a text string.
+   * Non-ASCII characters are first encoded as UTF-8, then each byte is escaped
+   * individually as a 3-digit octal escape.  Yes, it's weird.
+   */
+  static String escapeText(final String input) {
+    return escapeBytes(ByteString.copyFromUtf8(input));
+  }
+
+  /**
+   * Un-escape a text string as escaped using {@link #escapeText(String)}.
+   * Two-digit hex escapes (starting with "\x") are also recognized.
+   */
+  static String unescapeText(final String input)
+                             throws InvalidEscapeSequenceException {
+    return unescapeBytes(input).toStringUtf8();
+  }
+
+  /** Is this an octal digit? */
+  private static boolean isOctal(final char c) {
+    return '0' <= c && c <= '7';
+  }
+
+  /** Is this a hex digit? */
+  private static boolean isHex(final char c) {
+    return ('0' <= c && c <= '9') ||
+           ('a' <= c && c <= 'f') ||
+           ('A' <= c && c <= 'F');
+  }
+
+  /**
+   * Interpret a character as a digit (in any base up to 36) and return the
+   * numeric value.  This is like {@code Character.digit()} but we don't accept
+   * non-ASCII digits.
+   */
+  private static int digitValue(final char c) {
+    if ('0' <= c && c <= '9') {
+      return c - '0';
+    } else if ('a' <= c && c <= 'z') {
+      return c - 'a' + 10;
+    } else {
+      return c - 'A' + 10;
+    }
+  }
+
+  /**
+   * Parse a 32-bit signed integer from the text.  Unlike the Java standard
+   * {@code Integer.parseInt()}, this function recognizes the prefixes "0x"
+   * and "0" to signify hexidecimal and octal numbers, respectively.
+   */
+  static int parseInt32(final String text) throws NumberFormatException {
+    return (int) parseInteger(text, true, false);
+  }
+
+  /**
+   * Parse a 32-bit unsigned integer from the text.  Unlike the Java standard
+   * {@code Integer.parseInt()}, this function recognizes the prefixes "0x"
+   * and "0" to signify hexidecimal and octal numbers, respectively.  The
+   * result is coerced to a (signed) {@code int} when returned since Java has
+   * no unsigned integer type.
+   */
+  static int parseUInt32(final String text) throws NumberFormatException {
+    return (int) parseInteger(text, false, false);
+  }
+
+  /**
+   * Parse a 64-bit signed integer from the text.  Unlike the Java standard
+   * {@code Integer.parseInt()}, this function recognizes the prefixes "0x"
+   * and "0" to signify hexidecimal and octal numbers, respectively.
+   */
+  static long parseInt64(final String text) throws NumberFormatException {
+    return parseInteger(text, true, true);
+  }
+
+  /**
+   * Parse a 64-bit unsigned integer from the text.  Unlike the Java standard
+   * {@code Integer.parseInt()}, this function recognizes the prefixes "0x"
+   * and "0" to signify hexidecimal and octal numbers, respectively.  The
+   * result is coerced to a (signed) {@code long} when returned since Java has
+   * no unsigned long type.
+   */
+  static long parseUInt64(final String text) throws NumberFormatException {
+    return parseInteger(text, false, true);
+  }
+
+  private static long parseInteger(final String text,
+                                   final boolean isSigned,
+                                   final boolean isLong)
+                                   throws NumberFormatException {
+    int pos = 0;
+
+    boolean negative = false;
+    if (text.startsWith("-", pos)) {
+      if (!isSigned) {
+        throw new NumberFormatException("Number must be positive: " + text);
+      }
+      ++pos;
+      negative = true;
+    }
+
+    int radix = 10;
+    if (text.startsWith("0x", pos)) {
+      pos += 2;
+      radix = 16;
+    } else if (text.startsWith("0", pos)) {
+      radix = 8;
+    }
+
+    final String numberText = text.substring(pos);
+
+    long result = 0;
+    if (numberText.length() < 16) {
+      // Can safely assume no overflow.
+      result = Long.parseLong(numberText, radix);
+      if (negative) {
+        result = -result;
+      }
+
+      // Check bounds.
+      // No need to check for 64-bit numbers since they'd have to be 16 chars
+      // or longer to overflow.
+      if (!isLong) {
+        if (isSigned) {
+          if (result > Integer.MAX_VALUE || result < Integer.MIN_VALUE) {
+            throw new NumberFormatException(
+              "Number out of range for 32-bit signed integer: " + text);
+          }
+        } else {
+          if (result >= (1L << 32) || result < 0) {
+            throw new NumberFormatException(
+              "Number out of range for 32-bit unsigned integer: " + text);
+          }
+        }
+      }
+    } else {
+      BigInteger bigValue = new BigInteger(numberText, radix);
+      if (negative) {
+        bigValue = bigValue.negate();
+      }
+
+      // Check bounds.
+      if (!isLong) {
+        if (isSigned) {
+          if (bigValue.bitLength() > 31) {
+            throw new NumberFormatException(
+              "Number out of range for 32-bit signed integer: " + text);
+          }
+        } else {
+          if (bigValue.bitLength() > 32) {
+            throw new NumberFormatException(
+              "Number out of range for 32-bit unsigned integer: " + text);
+          }
+        }
+      } else {
+        if (isSigned) {
+          if (bigValue.bitLength() > 63) {
+            throw new NumberFormatException(
+              "Number out of range for 64-bit signed integer: " + text);
+          }
+        } else {
+          if (bigValue.bitLength() > 64) {
+            throw new NumberFormatException(
+              "Number out of range for 64-bit unsigned integer: " + text);
+          }
+        }
+      }
+
+      result = bigValue.longValue();
+    }
+
+    return result;
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/UninitializedMessageException.java b/java/src/main/java/com/google/protobuf/UninitializedMessageException.java
new file mode 100644
index 0000000..8743c12
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/UninitializedMessageException.java
@@ -0,0 +1,99 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Thrown when attempting to build a protocol message that is missing required
+ * fields.  This is a {@code RuntimeException} because it normally represents
+ * a programming error:  it happens when some code which constructs a message
+ * fails to set all the fields.  {@code parseFrom()} methods <b>do not</b>
+ * throw this; they throw an {@link InvalidProtocolBufferException} if
+ * required fields are missing, because it is not a programming error to
+ * receive an incomplete message.  In other words,
+ * {@code UninitializedMessageException} should never be thrown by correct
+ * code, but {@code InvalidProtocolBufferException} might be.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public class UninitializedMessageException extends RuntimeException {
+  private static final long serialVersionUID = -7466929953374883507L;
+
+  public UninitializedMessageException(final MessageLite message) {
+    super("Message was missing required fields.  (Lite runtime could not " +
+          "determine which fields were missing).");
+    missingFields = null;
+  }
+
+  public UninitializedMessageException(final List<String> missingFields) {
+    super(buildDescription(missingFields));
+    this.missingFields = missingFields;
+  }
+
+  private final List<String> missingFields;
+
+  /**
+   * Get a list of human-readable names of required fields missing from this
+   * message.  Each name is a full path to a field, e.g. "foo.bar[5].baz".
+   * Returns null if the lite runtime was used, since it lacks the ability to
+   * find missing fields.
+   */
+  public List<String> getMissingFields() {
+    return Collections.unmodifiableList(missingFields);
+  }
+
+  /**
+   * Converts this exception to an {@link InvalidProtocolBufferException}.
+   * When a parsed message is missing required fields, this should be thrown
+   * instead of {@code UninitializedMessageException}.
+   */
+  public InvalidProtocolBufferException asInvalidProtocolBufferException() {
+    return new InvalidProtocolBufferException(getMessage());
+  }
+
+  /** Construct the description string for this exception. */
+  private static String buildDescription(final List<String> missingFields) {
+    final StringBuilder description =
+      new StringBuilder("Message missing required fields: ");
+    boolean first = true;
+    for (final String field : missingFields) {
+      if (first) {
+        first = false;
+      } else {
+        description.append(", ");
+      }
+      description.append(field);
+    }
+    return description.toString();
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/UnknownFieldSet.java b/java/src/main/java/com/google/protobuf/UnknownFieldSet.java
new file mode 100644
index 0000000..7f7e493
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/UnknownFieldSet.java
@@ -0,0 +1,947 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * {@code UnknownFieldSet} is used to keep track of fields which were seen when
+ * parsing a protocol message but whose field numbers or types are unrecognized.
+ * This most frequently occurs when new fields are added to a message type
+ * and then messages containing those feilds are read by old software that was
+ * compiled before the new types were added.
+ *
+ * <p>Every {@link Message} contains an {@code UnknownFieldSet} (and every
+ * {@link Message.Builder} contains an {@link Builder}).
+ *
+ * <p>Most users will never need to use this class.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class UnknownFieldSet implements MessageLite {
+  private UnknownFieldSet() {}
+
+  /** Create a new {@link Builder}. */
+  public static Builder newBuilder() {
+    return Builder.create();
+  }
+
+  /**
+   * Create a new {@link Builder} and initialize it to be a copy
+   * of {@code copyFrom}.
+   */
+  public static Builder newBuilder(final UnknownFieldSet copyFrom) {
+    return newBuilder().mergeFrom(copyFrom);
+  }
+
+  /** Get an empty {@code UnknownFieldSet}. */
+  public static UnknownFieldSet getDefaultInstance() {
+    return defaultInstance;
+  }
+  public UnknownFieldSet getDefaultInstanceForType() {
+    return defaultInstance;
+  }
+  private static final UnknownFieldSet defaultInstance =
+    new UnknownFieldSet(Collections.<Integer, Field>emptyMap());
+
+  /**
+   * Construct an {@code UnknownFieldSet} around the given map.  The map is
+   * expected to be immutable.
+   */
+  private UnknownFieldSet(final Map<Integer, Field> fields) {
+    this.fields = fields;
+  }
+  private Map<Integer, Field> fields;
+
+  @Override
+  public boolean equals(final Object other) {
+    if (this == other) {
+      return true;
+    }
+    return (other instanceof UnknownFieldSet) &&
+           fields.equals(((UnknownFieldSet) other).fields);
+  }
+
+  @Override
+  public int hashCode() {
+    return fields.hashCode();
+  }
+
+  /** Get a map of fields in the set by number. */
+  public Map<Integer, Field> asMap() {
+    return fields;
+  }
+
+  /** Check if the given field number is present in the set. */
+  public boolean hasField(final int number) {
+    return fields.containsKey(number);
+  }
+
+  /**
+   * Get a field by number.  Returns an empty field if not present.  Never
+   * returns {@code null}.
+   */
+  public Field getField(final int number) {
+    final Field result = fields.get(number);
+    return (result == null) ? Field.getDefaultInstance() : result;
+  }
+
+  /** Serializes the set and writes it to {@code output}. */
+  public void writeTo(final CodedOutputStream output) throws IOException {
+    for (final Map.Entry<Integer, Field> entry : fields.entrySet()) {
+      entry.getValue().writeTo(entry.getKey(), output);
+    }
+  }
+
+  /**
+   * Converts the set to a string in protocol buffer text format. This is
+   * just a trivial wrapper around
+   * {@link TextFormat#printToString(UnknownFieldSet)}.
+   */
+  @Override
+  public String toString() {
+    return TextFormat.printToString(this);
+  }
+
+  /**
+   * Serializes the message to a {@code ByteString} and returns it. This is
+   * just a trivial wrapper around {@link #writeTo(CodedOutputStream)}.
+   */
+  public ByteString toByteString() {
+    try {
+      final ByteString.CodedBuilder out =
+        ByteString.newCodedBuilder(getSerializedSize());
+      writeTo(out.getCodedOutput());
+      return out.build();
+    } catch (final IOException e) {
+      throw new RuntimeException(
+        "Serializing to a ByteString threw an IOException (should " +
+        "never happen).", e);
+    }
+  }
+
+  /**
+   * Serializes the message to a {@code byte} array and returns it.  This is
+   * just a trivial wrapper around {@link #writeTo(CodedOutputStream)}.
+   */
+  public byte[] toByteArray() {
+    try {
+      final byte[] result = new byte[getSerializedSize()];
+      final CodedOutputStream output = CodedOutputStream.newInstance(result);
+      writeTo(output);
+      output.checkNoSpaceLeft();
+      return result;
+    } catch (final IOException e) {
+      throw new RuntimeException(
+        "Serializing to a byte array threw an IOException " +
+        "(should never happen).", e);
+    }
+  }
+
+  /**
+   * Serializes the message and writes it to {@code output}.  This is just a
+   * trivial wrapper around {@link #writeTo(CodedOutputStream)}.
+   */
+  public void writeTo(final OutputStream output) throws IOException {
+    final CodedOutputStream codedOutput = CodedOutputStream.newInstance(output);
+    writeTo(codedOutput);
+    codedOutput.flush();
+  }
+
+  public void writeDelimitedTo(OutputStream output) throws IOException {
+    final CodedOutputStream codedOutput = CodedOutputStream.newInstance(output);
+    codedOutput.writeRawVarint32(getSerializedSize());
+    writeTo(codedOutput);
+    codedOutput.flush();
+  }
+
+  /** Get the number of bytes required to encode this set. */
+  public int getSerializedSize() {
+    int result = 0;
+    for (final Map.Entry<Integer, Field> entry : fields.entrySet()) {
+      result += entry.getValue().getSerializedSize(entry.getKey());
+    }
+    return result;
+  }
+
+  /**
+   * Serializes the set and writes it to {@code output} using
+   * {@code MessageSet} wire format.
+   */
+  public void writeAsMessageSetTo(final CodedOutputStream output)
+      throws IOException {
+    for (final Map.Entry<Integer, Field> entry : fields.entrySet()) {
+      entry.getValue().writeAsMessageSetExtensionTo(
+        entry.getKey(), output);
+    }
+  }
+
+  /**
+   * Get the number of bytes required to encode this set using
+   * {@code MessageSet} wire format.
+   */
+  public int getSerializedSizeAsMessageSet() {
+    int result = 0;
+    for (final Map.Entry<Integer, Field> entry : fields.entrySet()) {
+      result += entry.getValue().getSerializedSizeAsMessageSetExtension(
+        entry.getKey());
+    }
+    return result;
+  }
+
+  public boolean isInitialized() {
+    // UnknownFieldSets do not have required fields, so they are always
+    // initialized.
+    return true;
+  }
+
+  /** Parse an {@code UnknownFieldSet} from the given input stream. */
+  public static UnknownFieldSet parseFrom(final CodedInputStream input)
+                                          throws IOException {
+    return newBuilder().mergeFrom(input).build();
+  }
+
+  /** Parse {@code data} as an {@code UnknownFieldSet} and return it. */
+  public static UnknownFieldSet parseFrom(final ByteString data)
+      throws InvalidProtocolBufferException {
+    return newBuilder().mergeFrom(data).build();
+  }
+
+  /** Parse {@code data} as an {@code UnknownFieldSet} and return it. */
+  public static UnknownFieldSet parseFrom(final byte[] data)
+      throws InvalidProtocolBufferException {
+    return newBuilder().mergeFrom(data).build();
+  }
+
+  /** Parse an {@code UnknownFieldSet} from {@code input} and return it. */
+  public static UnknownFieldSet parseFrom(final InputStream input)
+                                          throws IOException {
+    return newBuilder().mergeFrom(input).build();
+  }
+
+  public Builder newBuilderForType() {
+    return newBuilder();
+  }
+
+  public Builder toBuilder() {
+    return newBuilder().mergeFrom(this);
+  }
+
+  /**
+   * Builder for {@link UnknownFieldSet}s.
+   *
+   * <p>Note that this class maintains {@link Field.Builder}s for all fields
+   * in the set.  Thus, adding one element to an existing {@link Field} does not
+   * require making a copy.  This is important for efficient parsing of
+   * unknown repeated fields.  However, it implies that {@link Field}s cannot
+   * be constructed independently, nor can two {@link UnknownFieldSet}s share
+   * the same {@code Field} object.
+   *
+   * <p>Use {@link UnknownFieldSet#newBuilder()} to construct a {@code Builder}.
+   */
+  public static final class Builder implements MessageLite.Builder {
+    // This constructor should never be called directly (except from 'create').
+    private Builder() {}
+
+    private Map<Integer, Field> fields;
+
+    // Optimization:  We keep around a builder for the last field that was
+    //   modified so that we can efficiently add to it multiple times in a
+    //   row (important when parsing an unknown repeated field).
+    private int lastFieldNumber;
+    private Field.Builder lastField;
+
+    private static Builder create() {
+      Builder builder = new Builder();
+      builder.reinitialize();
+      return builder;
+    }
+
+    /**
+     * Get a field builder for the given field number which includes any
+     * values that already exist.
+     */
+    private Field.Builder getFieldBuilder(final int number) {
+      if (lastField != null) {
+        if (number == lastFieldNumber) {
+          return lastField;
+        }
+        // Note:  addField() will reset lastField and lastFieldNumber.
+        addField(lastFieldNumber, lastField.build());
+      }
+      if (number == 0) {
+        return null;
+      } else {
+        final Field existing = fields.get(number);
+        lastFieldNumber = number;
+        lastField = Field.newBuilder();
+        if (existing != null) {
+          lastField.mergeFrom(existing);
+        }
+        return lastField;
+      }
+    }
+
+    /**
+     * Build the {@link UnknownFieldSet} and return it.
+     *
+     * <p>Once {@code build()} has been called, the {@code Builder} will no
+     * longer be usable.  Calling any method after {@code build()} will result
+     * in undefined behavior and can cause a {@code NullPointerException} to be
+     * thrown.
+     */
+    public UnknownFieldSet build() {
+      getFieldBuilder(0);  // Force lastField to be built.
+      final UnknownFieldSet result;
+      if (fields.isEmpty()) {
+        result = getDefaultInstance();
+      } else {
+        result = new UnknownFieldSet(Collections.unmodifiableMap(fields));
+      }
+      fields = null;
+      return result;
+    }
+
+    public UnknownFieldSet buildPartial() {
+      // No required fields, so this is the same as build().
+      return build();
+    }
+
+    @Override
+    public Builder clone() {
+      getFieldBuilder(0);  // Force lastField to be built.
+      return UnknownFieldSet.newBuilder().mergeFrom(
+          new UnknownFieldSet(fields));
+    }
+
+    public UnknownFieldSet getDefaultInstanceForType() {
+      return UnknownFieldSet.getDefaultInstance();
+    }
+
+    private void reinitialize() {
+      fields = Collections.emptyMap();
+      lastFieldNumber = 0;
+      lastField = null;
+    }
+
+    /** Reset the builder to an empty set. */
+    public Builder clear() {
+      reinitialize();
+      return this;
+    }
+
+    /**
+     * Merge the fields from {@code other} into this set.  If a field number
+     * exists in both sets, {@code other}'s values for that field will be
+     * appended to the values in this set.
+     */
+    public Builder mergeFrom(final UnknownFieldSet other) {
+      if (other != getDefaultInstance()) {
+        for (final Map.Entry<Integer, Field> entry : other.fields.entrySet()) {
+          mergeField(entry.getKey(), entry.getValue());
+        }
+      }
+      return this;
+    }
+
+    /**
+     * Add a field to the {@code UnknownFieldSet}.  If a field with the same
+     * number already exists, the two are merged.
+     */
+    public Builder mergeField(final int number, final Field field) {
+      if (number == 0) {
+        throw new IllegalArgumentException("Zero is not a valid field number.");
+      }
+      if (hasField(number)) {
+        getFieldBuilder(number).mergeFrom(field);
+      } else {
+        // Optimization:  We could call getFieldBuilder(number).mergeFrom(field)
+        // in this case, but that would create a copy of the Field object.
+        // We'd rather reuse the one passed to us, so call addField() instead.
+        addField(number, field);
+      }
+      return this;
+    }
+
+    /**
+     * Convenience method for merging a new field containing a single varint
+     * value.  This is used in particular when an unknown enum value is
+     * encountered.
+     */
+    public Builder mergeVarintField(final int number, final int value) {
+      if (number == 0) {
+        throw new IllegalArgumentException("Zero is not a valid field number.");
+      }
+      getFieldBuilder(number).addVarint(value);
+      return this;
+    }
+
+    /** Check if the given field number is present in the set. */
+    public boolean hasField(final int number) {
+      if (number == 0) {
+        throw new IllegalArgumentException("Zero is not a valid field number.");
+      }
+      return number == lastFieldNumber || fields.containsKey(number);
+    }
+
+    /**
+     * Add a field to the {@code UnknownFieldSet}.  If a field with the same
+     * number already exists, it is removed.
+     */
+    public Builder addField(final int number, final Field field) {
+      if (number == 0) {
+        throw new IllegalArgumentException("Zero is not a valid field number.");
+      }
+      if (lastField != null && lastFieldNumber == number) {
+        // Discard this.
+        lastField = null;
+        lastFieldNumber = 0;
+      }
+      if (fields.isEmpty()) {
+        fields = new TreeMap<Integer,Field>();
+      }
+      fields.put(number, field);
+      return this;
+    }
+
+    /**
+     * Get all present {@code Field}s as an immutable {@code Map}.  If more
+     * fields are added, the changes may or may not be reflected in this map.
+     */
+    public Map<Integer, Field> asMap() {
+      getFieldBuilder(0);  // Force lastField to be built.
+      return Collections.unmodifiableMap(fields);
+    }
+
+    /**
+     * Parse an entire message from {@code input} and merge its fields into
+     * this set.
+     */
+    public Builder mergeFrom(final CodedInputStream input) throws IOException {
+      while (true) {
+        final int tag = input.readTag();
+        if (tag == 0 || !mergeFieldFrom(tag, input)) {
+          break;
+        }
+      }
+      return this;
+    }
+
+    /**
+     * Parse a single field from {@code input} and merge it into this set.
+     * @param tag The field's tag number, which was already parsed.
+     * @return {@code false} if the tag is an engroup tag.
+     */
+    public boolean mergeFieldFrom(final int tag, final CodedInputStream input)
+                                  throws IOException {
+      final int number = WireFormat.getTagFieldNumber(tag);
+      switch (WireFormat.getTagWireType(tag)) {
+        case WireFormat.WIRETYPE_VARINT:
+          getFieldBuilder(number).addVarint(input.readInt64());
+          return true;
+        case WireFormat.WIRETYPE_FIXED64:
+          getFieldBuilder(number).addFixed64(input.readFixed64());
+          return true;
+        case WireFormat.WIRETYPE_LENGTH_DELIMITED:
+          getFieldBuilder(number).addLengthDelimited(input.readBytes());
+          return true;
+        case WireFormat.WIRETYPE_START_GROUP:
+          final Builder subBuilder = newBuilder();
+          input.readGroup(number, subBuilder,
+                          ExtensionRegistry.getEmptyRegistry());
+          getFieldBuilder(number).addGroup(subBuilder.build());
+          return true;
+        case WireFormat.WIRETYPE_END_GROUP:
+          return false;
+        case WireFormat.WIRETYPE_FIXED32:
+          getFieldBuilder(number).addFixed32(input.readFixed32());
+          return true;
+        default:
+          throw InvalidProtocolBufferException.invalidWireType();
+      }
+    }
+
+    /**
+     * Parse {@code data} as an {@code UnknownFieldSet} and merge it with the
+     * set being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream)}.
+     */
+    public Builder mergeFrom(final ByteString data)
+        throws InvalidProtocolBufferException {
+      try {
+        final CodedInputStream input = data.newCodedInput();
+        mergeFrom(input);
+        input.checkLastTagWas(0);
+        return this;
+      } catch (final InvalidProtocolBufferException e) {
+        throw e;
+      } catch (final IOException e) {
+        throw new RuntimeException(
+          "Reading from a ByteString threw an IOException (should " +
+          "never happen).", e);
+      }
+    }
+
+    /**
+     * Parse {@code data} as an {@code UnknownFieldSet} and merge it with the
+     * set being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream)}.
+     */
+    public Builder mergeFrom(final byte[] data)
+        throws InvalidProtocolBufferException {
+      try {
+        final CodedInputStream input = CodedInputStream.newInstance(data);
+        mergeFrom(input);
+        input.checkLastTagWas(0);
+        return this;
+      } catch (final InvalidProtocolBufferException e) {
+        throw e;
+      } catch (final IOException e) {
+        throw new RuntimeException(
+          "Reading from a byte array threw an IOException (should " +
+          "never happen).", e);
+      }
+    }
+
+    /**
+     * Parse an {@code UnknownFieldSet} from {@code input} and merge it with the
+     * set being built.  This is just a small wrapper around
+     * {@link #mergeFrom(CodedInputStream)}.
+     */
+    public Builder mergeFrom(final InputStream input) throws IOException {
+      final CodedInputStream codedInput = CodedInputStream.newInstance(input);
+      mergeFrom(codedInput);
+      codedInput.checkLastTagWas(0);
+      return this;
+    }
+
+    public Builder mergeDelimitedFrom(InputStream input)
+        throws IOException {
+      final int size = CodedInputStream.readRawVarint32(input);
+      final InputStream limitedInput =
+        new AbstractMessage.Builder.LimitedInputStream(input, size);
+      return mergeFrom(limitedInput, null);
+    }
+
+    public Builder mergeDelimitedFrom(
+        InputStream input,
+        ExtensionRegistryLite extensionRegistry) throws IOException {
+      // UnknownFieldSet has no extensions.
+      return mergeFrom(input);
+    }
+
+    public Builder mergeFrom(
+        CodedInputStream input,
+        ExtensionRegistryLite extensionRegistry) throws IOException {
+      // UnknownFieldSet has no extensions.
+      return mergeFrom(input);
+    }
+
+    public Builder mergeFrom(
+        ByteString data,
+        ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      // UnknownFieldSet has no extensions.
+      return mergeFrom(data);
+    }
+
+    public Builder mergeFrom(byte[] data, int off, int len)
+        throws InvalidProtocolBufferException {
+      try {
+        final CodedInputStream input =
+            CodedInputStream.newInstance(data, off, len);
+        mergeFrom(input);
+        input.checkLastTagWas(0);
+        return this;
+      } catch (InvalidProtocolBufferException e) {
+        throw e;
+      } catch (IOException e) {
+        throw new RuntimeException(
+          "Reading from a byte array threw an IOException (should " +
+          "never happen).", e);
+      }
+    }
+
+    public Builder mergeFrom(
+        byte[] data,
+        ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      // UnknownFieldSet has no extensions.
+      return mergeFrom(data);
+    }
+
+    public Builder mergeFrom(
+        byte[] data, int off, int len,
+        ExtensionRegistryLite extensionRegistry)
+        throws InvalidProtocolBufferException {
+      // UnknownFieldSet has no extensions.
+      return mergeFrom(data, off, len);
+    }
+
+    public Builder mergeFrom(
+        InputStream input,
+        ExtensionRegistryLite extensionRegistry) throws IOException {
+      // UnknownFieldSet has no extensions.
+      return mergeFrom(input);
+    }
+
+    public boolean isInitialized() {
+      // UnknownFieldSets do not have required fields, so they are always
+      // initialized.
+      return true;
+    }
+  }
+
+  /**
+   * Represents a single field in an {@code UnknownFieldSet}.
+   *
+   * <p>A {@code Field} consists of five lists of values.  The lists correspond
+   * to the five "wire types" used in the protocol buffer binary format.
+   * The wire type of each field can be determined from the encoded form alone,
+   * without knowing the field's declared type.  So, we are able to parse
+   * unknown values at least this far and separate them.  Normally, only one
+   * of the five lists will contain any values, since it is impossible to
+   * define a valid message type that declares two different types for the
+   * same field number.  However, the code is designed to allow for the case
+   * where the same unknown field number is encountered using multiple different
+   * wire types.
+   *
+   * <p>{@code Field} is an immutable class.  To construct one, you must use a
+   * {@link Builder}.
+   *
+   * @see UnknownFieldSet
+   */
+  public static final class Field {
+    private Field() {}
+
+    /** Construct a new {@link Builder}. */
+    public static Builder newBuilder() {
+      return Builder.create();
+    }
+
+    /**
+     * Construct a new {@link Builder} and initialize it to a copy of
+     * {@code copyFrom}.
+     */
+    public static Builder newBuilder(final Field copyFrom) {
+      return newBuilder().mergeFrom(copyFrom);
+    }
+
+    /** Get an empty {@code Field}. */
+    public static Field getDefaultInstance() {
+      return fieldDefaultInstance;
+    }
+    private static final Field fieldDefaultInstance = newBuilder().build();
+
+    /** Get the list of varint values for this field. */
+    public List<Long> getVarintList()               { return varint;          }
+
+    /** Get the list of fixed32 values for this field. */
+    public List<Integer> getFixed32List()           { return fixed32;         }
+
+    /** Get the list of fixed64 values for this field. */
+    public List<Long> getFixed64List()              { return fixed64;         }
+
+    /** Get the list of length-delimited values for this field. */
+    public List<ByteString> getLengthDelimitedList() { return lengthDelimited; }
+
+    /**
+     * Get the list of embedded group values for this field.  These are
+     * represented using {@link UnknownFieldSet}s rather than {@link Message}s
+     * since the group's type is presumably unknown.
+     */
+    public List<UnknownFieldSet> getGroupList()      { return group;           }
+
+    @Override
+    public boolean equals(final Object other) {
+      if (this == other) {
+        return true;
+      }
+      if (!(other instanceof Field)) {
+        return false;
+      }
+      return Arrays.equals(getIdentityArray(),
+          ((Field) other).getIdentityArray());
+    }
+
+    @Override
+    public int hashCode() {
+      return Arrays.hashCode(getIdentityArray());
+    }
+
+    /**
+     * Returns the array of objects to be used to uniquely identify this
+     * {@link Field} instance.
+     */
+    private Object[] getIdentityArray() {
+      return new Object[] {
+          varint,
+          fixed32,
+          fixed64,
+          lengthDelimited,
+          group};
+    }
+
+    /**
+     * Serializes the field, including field number, and writes it to
+     * {@code output}.
+     */
+    public void writeTo(final int fieldNumber, final CodedOutputStream output)
+                        throws IOException {
+      for (final long value : varint) {
+        output.writeUInt64(fieldNumber, value);
+      }
+      for (final int value : fixed32) {
+        output.writeFixed32(fieldNumber, value);
+      }
+      for (final long value : fixed64) {
+        output.writeFixed64(fieldNumber, value);
+      }
+      for (final ByteString value : lengthDelimited) {
+        output.writeBytes(fieldNumber, value);
+      }
+      for (final UnknownFieldSet value : group) {
+        output.writeGroup(fieldNumber, value);
+      }
+    }
+
+    /**
+     * Get the number of bytes required to encode this field, including field
+     * number.
+     */
+    public int getSerializedSize(final int fieldNumber) {
+      int result = 0;
+      for (final long value : varint) {
+        result += CodedOutputStream.computeUInt64Size(fieldNumber, value);
+      }
+      for (final int value : fixed32) {
+        result += CodedOutputStream.computeFixed32Size(fieldNumber, value);
+      }
+      for (final long value : fixed64) {
+        result += CodedOutputStream.computeFixed64Size(fieldNumber, value);
+      }
+      for (final ByteString value : lengthDelimited) {
+        result += CodedOutputStream.computeBytesSize(fieldNumber, value);
+      }
+      for (final UnknownFieldSet value : group) {
+        result += CodedOutputStream.computeGroupSize(fieldNumber, value);
+      }
+      return result;
+    }
+
+    /**
+     * Serializes the field, including field number, and writes it to
+     * {@code output}, using {@code MessageSet} wire format.
+     */
+    public void writeAsMessageSetExtensionTo(
+        final int fieldNumber,
+        final CodedOutputStream output)
+        throws IOException {
+      for (final ByteString value : lengthDelimited) {
+        output.writeRawMessageSetExtension(fieldNumber, value);
+      }
+    }
+
+    /**
+     * Get the number of bytes required to encode this field, including field
+     * number, using {@code MessageSet} wire format.
+     */
+    public int getSerializedSizeAsMessageSetExtension(final int fieldNumber) {
+      int result = 0;
+      for (final ByteString value : lengthDelimited) {
+        result += CodedOutputStream.computeRawMessageSetExtensionSize(
+          fieldNumber, value);
+      }
+      return result;
+    }
+
+    private List<Long> varint;
+    private List<Integer> fixed32;
+    private List<Long> fixed64;
+    private List<ByteString> lengthDelimited;
+    private List<UnknownFieldSet> group;
+
+    /**
+     * Used to build a {@link Field} within an {@link UnknownFieldSet}.
+     *
+     * <p>Use {@link Field#newBuilder()} to construct a {@code Builder}.
+     */
+    public static final class Builder {
+      // This constructor should never be called directly (except from 'create').
+      private Builder() {}
+
+      private static Builder create() {
+        Builder builder = new Builder();
+        builder.result = new Field();
+        return builder;
+      }
+
+      private Field result;
+
+      /**
+       * Build the field.  After {@code build()} has been called, the
+       * {@code Builder} is no longer usable.  Calling any other method will
+       * result in undefined behavior and can cause a
+       * {@code NullPointerException} to be thrown.
+       */
+      public Field build() {
+        if (result.varint == null) {
+          result.varint = Collections.emptyList();
+        } else {
+          result.varint = Collections.unmodifiableList(result.varint);
+        }
+        if (result.fixed32 == null) {
+          result.fixed32 = Collections.emptyList();
+        } else {
+          result.fixed32 = Collections.unmodifiableList(result.fixed32);
+        }
+        if (result.fixed64 == null) {
+          result.fixed64 = Collections.emptyList();
+        } else {
+          result.fixed64 = Collections.unmodifiableList(result.fixed64);
+        }
+        if (result.lengthDelimited == null) {
+          result.lengthDelimited = Collections.emptyList();
+        } else {
+          result.lengthDelimited =
+            Collections.unmodifiableList(result.lengthDelimited);
+        }
+        if (result.group == null) {
+          result.group = Collections.emptyList();
+        } else {
+          result.group = Collections.unmodifiableList(result.group);
+        }
+
+        final Field returnMe = result;
+        result = null;
+        return returnMe;
+      }
+
+      /** Discard the field's contents. */
+      public Builder clear() {
+        result = new Field();
+        return this;
+      }
+
+      /**
+       * Merge the values in {@code other} into this field.  For each list
+       * of values, {@code other}'s values are append to the ones in this
+       * field.
+       */
+      public Builder mergeFrom(final Field other) {
+        if (!other.varint.isEmpty()) {
+          if (result.varint == null) {
+            result.varint = new ArrayList<Long>();
+          }
+          result.varint.addAll(other.varint);
+        }
+        if (!other.fixed32.isEmpty()) {
+          if (result.fixed32 == null) {
+            result.fixed32 = new ArrayList<Integer>();
+          }
+          result.fixed32.addAll(other.fixed32);
+        }
+        if (!other.fixed64.isEmpty()) {
+          if (result.fixed64 == null) {
+            result.fixed64 = new ArrayList<Long>();
+          }
+          result.fixed64.addAll(other.fixed64);
+        }
+        if (!other.lengthDelimited.isEmpty()) {
+          if (result.lengthDelimited == null) {
+            result.lengthDelimited = new ArrayList<ByteString>();
+          }
+          result.lengthDelimited.addAll(other.lengthDelimited);
+        }
+        if (!other.group.isEmpty()) {
+          if (result.group == null) {
+            result.group = new ArrayList<UnknownFieldSet>();
+          }
+          result.group.addAll(other.group);
+        }
+        return this;
+      }
+
+      /** Add a varint value. */
+      public Builder addVarint(final long value) {
+        if (result.varint == null) {
+          result.varint = new ArrayList<Long>();
+        }
+        result.varint.add(value);
+        return this;
+      }
+
+      /** Add a fixed32 value. */
+      public Builder addFixed32(final int value) {
+        if (result.fixed32 == null) {
+          result.fixed32 = new ArrayList<Integer>();
+        }
+        result.fixed32.add(value);
+        return this;
+      }
+
+      /** Add a fixed64 value. */
+      public Builder addFixed64(final long value) {
+        if (result.fixed64 == null) {
+          result.fixed64 = new ArrayList<Long>();
+        }
+        result.fixed64.add(value);
+        return this;
+      }
+
+      /** Add a length-delimited value. */
+      public Builder addLengthDelimited(final ByteString value) {
+        if (result.lengthDelimited == null) {
+          result.lengthDelimited = new ArrayList<ByteString>();
+        }
+        result.lengthDelimited.add(value);
+        return this;
+      }
+
+      /** Add an embedded group. */
+      public Builder addGroup(final UnknownFieldSet value) {
+        if (result.group == null) {
+          result.group = new ArrayList<UnknownFieldSet>();
+        }
+        result.group.add(value);
+        return this;
+      }
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/WireFormat.java b/java/src/main/java/com/google/protobuf/WireFormat.java
new file mode 100644
index 0000000..3b0bdcd
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/WireFormat.java
@@ -0,0 +1,153 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * This class is used internally by the Protocol Buffer library and generated
+ * message implementations.  It is public only because those generated messages
+ * do not reside in the {@code protobuf} package.  Others should not use this
+ * class directly.
+ *
+ * This class contains constants and helper functions useful for dealing with
+ * the Protocol Buffer wire format.
+ *
+ * @author kenton@google.com Kenton Varda
+ */
+public final class WireFormat {
+  // Do not allow instantiation.
+  private WireFormat() {}
+
+  static final int WIRETYPE_VARINT           = 0;
+  static final int WIRETYPE_FIXED64          = 1;
+  static final int WIRETYPE_LENGTH_DELIMITED = 2;
+  static final int WIRETYPE_START_GROUP      = 3;
+  static final int WIRETYPE_END_GROUP        = 4;
+  static final int WIRETYPE_FIXED32          = 5;
+
+  static final int TAG_TYPE_BITS = 3;
+  static final int TAG_TYPE_MASK = (1 << TAG_TYPE_BITS) - 1;
+
+  /** Given a tag value, determines the wire type (the lower 3 bits). */
+  static int getTagWireType(final int tag) {
+    return tag & TAG_TYPE_MASK;
+  }
+
+  /** Given a tag value, determines the field number (the upper 29 bits). */
+  public static int getTagFieldNumber(final int tag) {
+    return tag >>> TAG_TYPE_BITS;
+  }
+
+  /** Makes a tag value given a field number and wire type. */
+  static int makeTag(final int fieldNumber, final int wireType) {
+    return (fieldNumber << TAG_TYPE_BITS) | wireType;
+  }
+
+  /**
+   * Lite equivalent to {@link Descriptors.FieldDescriptor.JavaType}.  This is
+   * only here to support the lite runtime and should not be used by users.
+   */
+  public enum JavaType {
+    INT(0),
+    LONG(0L),
+    FLOAT(0F),
+    DOUBLE(0D),
+    BOOLEAN(false),
+    STRING(""),
+    BYTE_STRING(ByteString.EMPTY),
+    ENUM(null),
+    MESSAGE(null);
+
+    JavaType(final Object defaultDefault) {
+      this.defaultDefault = defaultDefault;
+    }
+
+    /**
+     * The default default value for fields of this type, if it's a primitive
+     * type.
+     */
+    Object getDefaultDefault() {
+      return defaultDefault;
+    }
+
+    private final Object defaultDefault;
+  }
+
+  /**
+   * Lite equivalent to {@link Descriptors.FieldDescriptor.Type}.  This is
+   * only here to support the lite runtime and should not be used by users.
+   */
+  public enum FieldType {
+    DOUBLE  (JavaType.DOUBLE     , WIRETYPE_FIXED64         ),
+    FLOAT   (JavaType.FLOAT      , WIRETYPE_FIXED32         ),
+    INT64   (JavaType.LONG       , WIRETYPE_VARINT          ),
+    UINT64  (JavaType.LONG       , WIRETYPE_VARINT          ),
+    INT32   (JavaType.INT        , WIRETYPE_VARINT          ),
+    FIXED64 (JavaType.LONG       , WIRETYPE_FIXED64         ),
+    FIXED32 (JavaType.INT        , WIRETYPE_FIXED32         ),
+    BOOL    (JavaType.BOOLEAN    , WIRETYPE_VARINT          ),
+    STRING  (JavaType.STRING     , WIRETYPE_LENGTH_DELIMITED),
+    GROUP   (JavaType.MESSAGE    , WIRETYPE_START_GROUP     ),
+    MESSAGE (JavaType.MESSAGE    , WIRETYPE_LENGTH_DELIMITED),
+    BYTES   (JavaType.BYTE_STRING, WIRETYPE_LENGTH_DELIMITED),
+    UINT32  (JavaType.INT        , WIRETYPE_VARINT          ),
+    ENUM    (JavaType.ENUM       , WIRETYPE_VARINT          ),
+    SFIXED32(JavaType.INT        , WIRETYPE_FIXED32         ),
+    SFIXED64(JavaType.LONG       , WIRETYPE_FIXED64         ),
+    SINT32  (JavaType.INT        , WIRETYPE_VARINT          ),
+    SINT64  (JavaType.LONG       , WIRETYPE_VARINT          );
+
+    FieldType(final JavaType javaType, final int wireType) {
+      this.javaType = javaType;
+      this.wireType = wireType;
+    }
+
+    private final JavaType javaType;
+    private final int wireType;
+
+    public JavaType getJavaType() { return javaType; }
+    public int getWireType() { return wireType; }
+  }
+
+  // Field numbers for feilds in MessageSet wire format.
+  static final int MESSAGE_SET_ITEM    = 1;
+  static final int MESSAGE_SET_TYPE_ID = 2;
+  static final int MESSAGE_SET_MESSAGE = 3;
+
+  // Tag numbers.
+  static final int MESSAGE_SET_ITEM_TAG =
+    makeTag(MESSAGE_SET_ITEM, WIRETYPE_START_GROUP);
+  static final int MESSAGE_SET_ITEM_END_TAG =
+    makeTag(MESSAGE_SET_ITEM, WIRETYPE_END_GROUP);
+  static final int MESSAGE_SET_TYPE_ID_TAG =
+    makeTag(MESSAGE_SET_TYPE_ID, WIRETYPE_VARINT);
+  static final int MESSAGE_SET_MESSAGE_TAG =
+    makeTag(MESSAGE_SET_MESSAGE, WIRETYPE_LENGTH_DELIMITED);
+}