Accessor style for optional fields.

This CL implements the 'optional_field_style=accessors' option.
All optional fields will now be 1 Java field and 1 bit in a shared
bitfield behind get/set/has/clear accessor methods. The setter
performs null check for reference types (Strings and byte[]s).

Also decentralized the clear code generation.

Change-Id: I60ac78329e352e76c2f8139fba1f292383080ad3

12 files changed, 525 insertions, 56 deletions

diff --git a/src/google/protobuf/compiler/javanano/javanano_enum_field.cc b/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
index 9c4acb9..b30b9fb 100644
--- a/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_enum_field.cc
@@ -90,7 +90,18 @@ GenerateMembers(io::Printer* printer) const {
 }
 
 void EnumFieldGenerator::
-GenerateParsingCode(io::Printer* printer) const {
+GenerateClearCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$ = $default$;\n");
+
+  if (params_.generate_has()) {
+    printer->Print(variables_,
+      "has$capitalized_name$ = false;\n");
+  }
+}
+
+void EnumFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
   printer->Print(variables_,
     "  this.$name$ = input.readInt32();\n");
 
@@ -146,6 +157,71 @@ string EnumFieldGenerator::GetBoxedType() const {
 
 // ===================================================================
 
+AccessorEnumFieldGenerator::
+AccessorEnumFieldGenerator(const FieldDescriptor* descriptor,
+    const Params& params, int has_bit_index)
+  : FieldGenerator(params), descriptor_(descriptor) {
+  SetEnumVariables(params, descriptor, &variables_);
+  SetBitOperationVariables("has", has_bit_index, &variables_);
+}
+
+AccessorEnumFieldGenerator::~AccessorEnumFieldGenerator() {}
+
+void AccessorEnumFieldGenerator::
+GenerateMembers(io::Printer* printer) const {
+  printer->Print(variables_,
+    "private int $name$_ = $default$;\n"
+    "public int get$capitalized_name$() {\n"
+    "  return $name$_;\n"
+    "}\n"
+    "public void set$capitalized_name$(int value) {\n"
+    "  $name$_ = value;\n"
+    "  $set_has$;\n"
+    "}\n"
+    "public boolean has$capitalized_name$() {\n"
+    "  return $get_has$;\n"
+    "}\n"
+    "public void clear$capitalized_name$() {\n"
+    "  $name$_ = $default$;\n"
+    "  $clear_has$;\n"
+    "}\n");
+}
+
+void AccessorEnumFieldGenerator::
+GenerateClearCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$_ = $default$;\n");
+}
+
+void AccessorEnumFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "set$capitalized_name$(input.readInt32());\n");
+}
+
+void AccessorEnumFieldGenerator::
+GenerateSerializationCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "if (has$capitalized_name$()) {\n"
+    "  output.writeInt32($number$, $name$_);\n"
+    "}\n");
+}
+
+void AccessorEnumFieldGenerator::
+GenerateSerializedSizeCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "if (has$capitalized_name$()) {\n"
+    "  size += com.google.protobuf.nano.CodedOutputByteBufferNano\n"
+    "    .computeInt32Size($number$, $name$_);\n"
+    "}\n");
+}
+
+string AccessorEnumFieldGenerator::GetBoxedType() const {
+  return ClassName(params_, descriptor_->enum_type());
+}
+
+// ===================================================================
+
 RepeatedEnumFieldGenerator::
 RepeatedEnumFieldGenerator(const FieldDescriptor* descriptor, const Params& params)
   : FieldGenerator(params), descriptor_(descriptor) {
@@ -165,7 +241,13 @@ GenerateMembers(io::Printer* printer) const {
 }
 
 void RepeatedEnumFieldGenerator::
-GenerateParsingCode(io::Printer* printer) const {
+GenerateClearCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$ = com.google.protobuf.nano.WireFormatNano.EMPTY_INT_ARRAY;\n");
+}
+
+void RepeatedEnumFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
   // First, figure out the length of the array, then parse.
   if (descriptor_->options().packed()) {
     printer->Print(variables_,
diff --git a/src/google/protobuf/compiler/javanano/javanano_enum_field.h b/src/google/protobuf/compiler/javanano/javanano_enum_field.h
index 6e1a443..934aaaa 100644
--- a/src/google/protobuf/compiler/javanano/javanano_enum_field.h
+++ b/src/google/protobuf/compiler/javanano/javanano_enum_field.h
@@ -51,7 +51,8 @@ class EnumFieldGenerator : public FieldGenerator {
 
   // implements FieldGenerator ---------------------------------------
   void GenerateMembers(io::Printer* printer) const;
-  void GenerateParsingCode(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
 
@@ -64,6 +65,28 @@ class EnumFieldGenerator : public FieldGenerator {
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(EnumFieldGenerator);
 };
 
+class AccessorEnumFieldGenerator : public FieldGenerator {
+ public:
+  explicit AccessorEnumFieldGenerator(const FieldDescriptor* descriptor,
+      const Params& params, int has_bit_index);
+  ~AccessorEnumFieldGenerator();
+
+  // implements FieldGenerator ---------------------------------------
+  void GenerateMembers(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateSerializationCode(io::Printer* printer) const;
+  void GenerateSerializedSizeCode(io::Printer* printer) const;
+
+  string GetBoxedType() const;
+
+ private:
+  const FieldDescriptor* descriptor_;
+  map<string, string> variables_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(AccessorEnumFieldGenerator);
+};
+
 class RepeatedEnumFieldGenerator : public FieldGenerator {
  public:
   explicit RepeatedEnumFieldGenerator(const FieldDescriptor* descriptor, const Params& params);
@@ -71,7 +94,8 @@ class RepeatedEnumFieldGenerator : public FieldGenerator {
 
   // implements FieldGenerator ---------------------------------------
   void GenerateMembers(io::Printer* printer) const;
-  void GenerateParsingCode(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
 
diff --git a/src/google/protobuf/compiler/javanano/javanano_field.cc b/src/google/protobuf/compiler/javanano/javanano_field.cc
index ea25786..6629f96 100644
--- a/src/google/protobuf/compiler/javanano/javanano_field.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_field.cc
@@ -53,16 +53,21 @@ FieldGeneratorMap::FieldGeneratorMap(const Descriptor* descriptor, const Params
     extension_generators_(
       new scoped_ptr<FieldGenerator>[descriptor->extension_count()]) {
 
+  int next_has_bit_index = 0;
   // Construct all the FieldGenerators.
   for (int i = 0; i < descriptor->field_count(); i++) {
-    field_generators_[i].reset(MakeGenerator(descriptor->field(i), params));
+    field_generators_[i].reset(
+        MakeGenerator(descriptor->field(i), params, &next_has_bit_index));
   }
   for (int i = 0; i < descriptor->extension_count(); i++) {
-    extension_generators_[i].reset(MakeGenerator(descriptor->extension(i), params));
+    extension_generators_[i].reset(
+        MakeGenerator(descriptor->extension(i), params, &next_has_bit_index));
   }
+  total_bits_ = next_has_bit_index;
 }
 
-FieldGenerator* FieldGeneratorMap::MakeGenerator(const FieldDescriptor* field, const Params &params) {
+FieldGenerator* FieldGeneratorMap::MakeGenerator(const FieldDescriptor* field,
+    const Params &params, int* next_has_bit_index) {
   if (field->is_repeated()) {
     switch (GetJavaType(field)) {
       case JAVATYPE_MESSAGE:
@@ -72,6 +77,21 @@ FieldGenerator* FieldGeneratorMap::MakeGenerator(const FieldDescriptor* field, c
       default:
         return new RepeatedPrimitiveFieldGenerator(field, params);
     }
+  } else if (params.optional_field_accessors() && field->is_optional()) {
+    // We need a has-bit for each primitive/enum field because their default
+    // values could be same as explicitly set values. But we don't need it
+    // for a message field because they have no defaults and Nano uses 'null'
+    // for unset messages, which cannot be set explicitly.
+    switch (GetJavaType(field)) {
+      case JAVATYPE_MESSAGE:
+        return new AccessorMessageFieldGenerator(field, params);
+      case JAVATYPE_ENUM:
+        return new AccessorEnumFieldGenerator(
+            field, params, (*next_has_bit_index)++);
+      default:
+        return new AccessorPrimitiveFieldGenerator(
+            field, params, (*next_has_bit_index)++);
+    }
   } else {
     switch (GetJavaType(field)) {
       case JAVATYPE_MESSAGE:
diff --git a/src/google/protobuf/compiler/javanano/javanano_field.h b/src/google/protobuf/compiler/javanano/javanano_field.h
index 7db48a5..dad2e7a 100644
--- a/src/google/protobuf/compiler/javanano/javanano_field.h
+++ b/src/google/protobuf/compiler/javanano/javanano_field.h
@@ -58,7 +58,8 @@ class FieldGenerator {
   virtual ~FieldGenerator();
 
   virtual void GenerateMembers(io::Printer* printer) const = 0;
-  virtual void GenerateParsingCode(io::Printer* printer) const = 0;
+  virtual void GenerateClearCode(io::Printer* printer) const = 0;
+  virtual void GenerateMergingCode(io::Printer* printer) const = 0;
   virtual void GenerateSerializationCode(io::Printer* printer) const = 0;
   virtual void GenerateSerializedSizeCode(io::Printer* printer) const = 0;
 
@@ -78,13 +79,16 @@ class FieldGeneratorMap {
 
   const FieldGenerator& get(const FieldDescriptor* field) const;
   const FieldGenerator& get_extension(int index) const;
+  int total_bits() const { return total_bits_; }
 
  private:
   const Descriptor* descriptor_;
   scoped_array<scoped_ptr<FieldGenerator> > field_generators_;
   scoped_array<scoped_ptr<FieldGenerator> > extension_generators_;
+  int total_bits_;
 
-  static FieldGenerator* MakeGenerator(const FieldDescriptor* field, const Params &params);
+  static FieldGenerator* MakeGenerator(const FieldDescriptor* field,
+      const Params &params, int* next_has_bit_index);
 
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FieldGeneratorMap);
 };
diff --git a/src/google/protobuf/compiler/javanano/javanano_helpers.cc b/src/google/protobuf/compiler/javanano/javanano_helpers.cc
index ebc9c63..630ecd1 100644
--- a/src/google/protobuf/compiler/javanano/javanano_helpers.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_helpers.cc
@@ -484,6 +484,13 @@ string GenerateClearBit(int bit_index) {
   return result;
 }
 
+void SetBitOperationVariables(const string name,
+    int bitIndex, map<string, string>* variables) {
+  (*variables)["get_" + name] = GenerateGetBit(bitIndex);
+  (*variables)["set_" + name] = GenerateSetBit(bitIndex);
+  (*variables)["clear_" + name] = GenerateClearBit(bitIndex);
+}
+
 }  // namespace javanano
 }  // namespace compiler
 }  // namespace protobuf
diff --git a/src/google/protobuf/compiler/javanano/javanano_helpers.h b/src/google/protobuf/compiler/javanano/javanano_helpers.h
index 03fd434..cddc077 100644
--- a/src/google/protobuf/compiler/javanano/javanano_helpers.h
+++ b/src/google/protobuf/compiler/javanano/javanano_helpers.h
@@ -163,6 +163,11 @@ string GenerateSetBit(int bit_index);
 // Example: "bitField1_ = (bitField1_ & ~0x04)"
 string GenerateClearBit(int bit_index);
 
+// Sets the 'get_*', 'set_*' and 'clear_*' variables, where * is the given bit
+// field name, to the appropriate Java expressions for the given bit index.
+void SetBitOperationVariables(const string name,
+    int bitIndex, map<string, string>* variables);
+
 }  // namespace javanano
 }  // namespace compiler
 }  // namespace protobuf
diff --git a/src/google/protobuf/compiler/javanano/javanano_message.cc b/src/google/protobuf/compiler/javanano/javanano_message.cc
index 851c443..c9ea654 100644
--- a/src/google/protobuf/compiler/javanano/javanano_message.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_message.cc
@@ -137,9 +137,9 @@ void MessageGenerator::Generate(io::Printer* printer) {
   // warnings here in the class declaration.
   printer->Print(
     "@SuppressWarnings(\"hiding\")\n"
-    "public $modifiers$ final class $classname$ extends\n"
+    "public $modifiers$final class $classname$ extends\n"
     "    com.google.protobuf.nano.MessageNano {\n",
-    "modifiers", is_own_file ? "" : "static",
+    "modifiers", is_own_file ? "" : "static ",
     "classname", descriptor_->name());
   printer->Indent();
   printer->Print(
@@ -167,6 +167,13 @@ void MessageGenerator::Generate(io::Printer* printer) {
     MessageGenerator(descriptor_->nested_type(i), params_).Generate(printer);
   }
 
+  // Integers for bit fields
+  int totalInts = (field_generators_.total_bits() + 31) / 32;
+  for (int i = 0; i < totalInts; i++) {
+    printer->Print("private int $bit_field_name$;\n",
+      "bit_field_name", GetBitFieldName(i));
+  }
+
   // Fields
   for (int i = 0; i < descriptor_->field_count(); i++) {
     PrintFieldComment(printer, descriptor_->field(i));
@@ -327,7 +334,7 @@ void MessageGenerator::GenerateMergeFromMethods(io::Printer* printer) {
       "tag", SimpleItoa(tag));
     printer->Indent();
 
-    field_generators_.get(field).GenerateParsingCode(printer);
+    field_generators_.get(field).GenerateMergingCode(printer);
 
     printer->Outdent();
     printer->Print(
@@ -376,33 +383,17 @@ void MessageGenerator::GenerateClear(io::Printer* printer) {
     "classname", descriptor_->name());
   printer->Indent();
 
+  // Clear bit fields.
+  int totalInts = (field_generators_.total_bits() + 31) / 32;
+  for (int i = 0; i < totalInts; i++) {
+    printer->Print("$bit_field_name$ = 0;\n",
+      "bit_field_name", GetBitFieldName(i));
+  }
+
   // Call clear for all of the fields.
   for (int i = 0; i < descriptor_->field_count(); i++) {
     const FieldDescriptor* field = descriptor_->field(i);
-
-    if (field->type() == FieldDescriptor::TYPE_BYTES &&
-        !field->default_value_string().empty()) {
-      // Need to clone the default value because it is of a mutable
-      // type.
-      printer->Print(
-        "$name$ = $default$.clone();\n",
-        "name", RenameJavaKeywords(UnderscoresToCamelCase(field)),
-        "default", DefaultValue(params_, field));
-    } else {
-      printer->Print(
-        "$name$ = $default$;\n",
-        "name", RenameJavaKeywords(UnderscoresToCamelCase(field)),
-        "default", DefaultValue(params_, field));
-    }
-
-    if (params_.generate_has() &&
-        field->label() != FieldDescriptor::LABEL_REPEATED &&
-        field->type() != FieldDescriptor::TYPE_GROUP &&
-        field->type() != FieldDescriptor::TYPE_MESSAGE) {
-      printer->Print(
-        "has$capitalized_name$ = false;\n",
-        "capitalized_name", UnderscoresToCapitalizedCamelCase(field));
-    }
+    field_generators_.get(field).GenerateClearCode(printer);
   }
 
   // Clear unknown fields.
diff --git a/src/google/protobuf/compiler/javanano/javanano_message_field.cc b/src/google/protobuf/compiler/javanano/javanano_message_field.cc
index 7d9a281..02dbdb1 100644
--- a/src/google/protobuf/compiler/javanano/javanano_message_field.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_message_field.cc
@@ -88,9 +88,17 @@ GenerateMembers(io::Printer* printer) const {
 }
 
 void MessageFieldGenerator::
-GenerateParsingCode(io::Printer* printer) const {
+GenerateClearCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "this.$name$ = new $type$();\n");
+    "$name$ = null;\n");
+}
+
+void MessageFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "if (this.$name$ == null) {\n"
+    "  this.$name$ = new $type$();\n"
+    "}");
 
   if (descriptor_->type() == FieldDescriptor::TYPE_GROUP) {
     printer->Print(variables_,
@@ -124,6 +132,81 @@ string MessageFieldGenerator::GetBoxedType() const {
 
 // ===================================================================
 
+AccessorMessageFieldGenerator::
+AccessorMessageFieldGenerator(
+    const FieldDescriptor* descriptor, const Params& params)
+  : FieldGenerator(params), descriptor_(descriptor) {
+  SetMessageVariables(params, descriptor, &variables_);
+}
+
+AccessorMessageFieldGenerator::~AccessorMessageFieldGenerator() {}
+
+void AccessorMessageFieldGenerator::
+GenerateMembers(io::Printer* printer) const {
+  printer->Print(variables_,
+    "private $type$ $name$_ = null;\n"
+    "public $type$ get$capitalized_name$() {\n"
+    "  return $name$_;\n"
+    "}\n"
+    "public void set$capitalized_name$($type$ value) {\n"
+    "  if (value == null) {\n"
+    "    throw new java.lang.NullPointerException();\n"
+    "  }\n"
+    "  $name$_ = value;\n"
+    "}\n"
+    "public boolean has$capitalized_name$() {\n"
+    "  return $name$_ != null;\n"
+    "}\n"
+    "public void clear$capitalized_name$() {\n"
+    "  $name$_ = null;\n"
+    "}\n");
+}
+
+void AccessorMessageFieldGenerator::
+GenerateClearCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$_ = null;\n");
+}
+
+void AccessorMessageFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "if (!has$capitalized_name$()) {\n"
+    "  set$capitalized_name$(new $type$());\n"
+    "}");
+
+  if (descriptor_->type() == FieldDescriptor::TYPE_GROUP) {
+    printer->Print(variables_,
+      "input.readGroup($name$_, $number$);\n");
+  } else {
+    printer->Print(variables_,
+      "input.readMessage($name$_);\n");
+  }
+}
+
+void AccessorMessageFieldGenerator::
+GenerateSerializationCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "if (has$capitalized_name$()) {\n"
+    "  output.write$group_or_message$($number$, $name$_);\n"
+    "}\n");
+}
+
+void AccessorMessageFieldGenerator::
+GenerateSerializedSizeCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "if (has$capitalized_name$()) {\n"
+    "  size += com.google.protobuf.nano.CodedOutputByteBufferNano\n"
+    "    .compute$group_or_message$Size($number$, $name$_);\n"
+    "}\n");
+}
+
+string AccessorMessageFieldGenerator::GetBoxedType() const {
+  return ClassName(params_, descriptor_->message_type());
+}
+
+// ===================================================================
+
 RepeatedMessageFieldGenerator::
 RepeatedMessageFieldGenerator(const FieldDescriptor* descriptor, const Params& params)
   : FieldGenerator(params), descriptor_(descriptor) {
@@ -139,7 +222,13 @@ GenerateMembers(io::Printer* printer) const {
 }
 
 void RepeatedMessageFieldGenerator::
-GenerateParsingCode(io::Printer* printer) const {
+GenerateClearCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$ = $type$.EMPTY_ARRAY;\n");
+}
+
+void RepeatedMessageFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
   // First, figure out the length of the array, then parse.
   printer->Print(variables_,
     "int arrayLength = com.google.protobuf.nano.WireFormatNano.getRepeatedFieldArrayLength(input, $tag$);\n"
diff --git a/src/google/protobuf/compiler/javanano/javanano_message_field.h b/src/google/protobuf/compiler/javanano/javanano_message_field.h
index 943a832..9807513 100644
--- a/src/google/protobuf/compiler/javanano/javanano_message_field.h
+++ b/src/google/protobuf/compiler/javanano/javanano_message_field.h
@@ -51,7 +51,8 @@ class MessageFieldGenerator : public FieldGenerator {
 
   // implements FieldGenerator ---------------------------------------
   void GenerateMembers(io::Printer* printer) const;
-  void GenerateParsingCode(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
 
@@ -64,6 +65,28 @@ class MessageFieldGenerator : public FieldGenerator {
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageFieldGenerator);
 };
 
+class AccessorMessageFieldGenerator : public FieldGenerator {
+ public:
+  explicit AccessorMessageFieldGenerator(
+      const FieldDescriptor* descriptor, const Params& params);
+  ~AccessorMessageFieldGenerator();
+
+  // implements FieldGenerator ---------------------------------------
+  void GenerateMembers(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateSerializationCode(io::Printer* printer) const;
+  void GenerateSerializedSizeCode(io::Printer* printer) const;
+
+  string GetBoxedType() const;
+
+ private:
+  const FieldDescriptor* descriptor_;
+  map<string, string> variables_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(AccessorMessageFieldGenerator);
+};
+
 class RepeatedMessageFieldGenerator : public FieldGenerator {
  public:
   explicit RepeatedMessageFieldGenerator(const FieldDescriptor* descriptor,
@@ -72,7 +95,8 @@ class RepeatedMessageFieldGenerator : public FieldGenerator {
 
   // implements FieldGenerator ---------------------------------------
   void GenerateMembers(io::Printer* printer) const;
-  void GenerateParsingCode(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
 
diff --git a/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc b/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
index 79357e9..69664d3 100644
--- a/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
+++ b/src/google/protobuf/compiler/javanano/javanano_primitive_field.cc
@@ -260,6 +260,7 @@ void SetPrimitiveVariables(const FieldDescriptor* descriptor, const Params param
       default_value = strings::Substitute(
           "com.google.protobuf.nano.InternalNano.bytesDefaultValue(\"$0\")",
           CEscape(descriptor->default_value_string()));
+      (*variables)["default_copy_if_needed"] = (*variables)["default"] + ".clone()";
     } else {
       if (AllAscii(descriptor->default_value_string())) {
         // All chars are ASCII.  In this case CEscape() works fine.
@@ -269,8 +270,11 @@ void SetPrimitiveVariables(const FieldDescriptor* descriptor, const Params param
             "com.google.protobuf.nano.InternalNano.stringDefaultValue(\"$0\")",
             CEscape(descriptor->default_value_string()));
       }
+      (*variables)["default_copy_if_needed"] = (*variables)["default"];
     }
     (*variables)["default_constant_value"] = default_value;
+  } else {
+    (*variables)["default_copy_if_needed"] = (*variables)["default"];
   }
   (*variables)["boxed_type"] = BoxedPrimitiveTypeName(GetJavaType(descriptor));
   (*variables)["capitalized_type"] = GetCapitalizedType(descriptor);
@@ -280,7 +284,7 @@ void SetPrimitiveVariables(const FieldDescriptor* descriptor, const Params param
   if (IsReferenceType(GetJavaType(descriptor))) {
     (*variables)["null_check"] =
         "  if (value == null) {\n"
-        "    throw new NullPointerException();\n"
+        "    throw new java.lang.NullPointerException();\n"
         "  }\n";
   } else {
     (*variables)["null_check"] = "";
@@ -310,17 +314,9 @@ GenerateMembers(io::Printer* printer) const {
     // Those primitive types that need a saved default.
     printer->Print(variables_,
       "private static final $type$ $default_constant$ = $default_constant_value$;\n");
-    if (descriptor_->type() == FieldDescriptor::TYPE_BYTES) {
-      printer->Print(variables_,
-        "public $type$ $name$ = $default$.clone();\n");
-    } else {
-      printer->Print(variables_,
-        "public $type$ $name$ = $default$;\n");
-    }
-  } else {
-    printer->Print(variables_,
-      "public $type$ $name$ = $default$;\n");
   }
+  printer->Print(variables_,
+    "public $type$ $name$ = $default_copy_if_needed$;\n");
 
   if (params_.generate_has()) {
     printer->Print(variables_,
@@ -329,7 +325,18 @@ GenerateMembers(io::Printer* printer) const {
 }
 
 void PrimitiveFieldGenerator::
-GenerateParsingCode(io::Printer* printer) const {
+GenerateClearCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$ = $default_copy_if_needed$;\n");
+
+  if (params_.generate_has()) {
+    printer->Print(variables_,
+      "has$capitalized_name$ = false;\n");
+  }
+}
+
+void PrimitiveFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
   printer->Print(variables_,
     "this.$name$ = input.read$capitalized_type$();\n");
 
@@ -397,6 +404,76 @@ string PrimitiveFieldGenerator::GetBoxedType() const {
 
 // ===================================================================
 
+AccessorPrimitiveFieldGenerator::
+AccessorPrimitiveFieldGenerator(const FieldDescriptor* descriptor,
+     const Params& params, int has_bit_index)
+  : FieldGenerator(params), descriptor_(descriptor) {
+  SetPrimitiveVariables(descriptor, params, &variables_);
+  SetBitOperationVariables("has", has_bit_index, &variables_);
+}
+
+AccessorPrimitiveFieldGenerator::~AccessorPrimitiveFieldGenerator() {}
+
+void AccessorPrimitiveFieldGenerator::
+GenerateMembers(io::Printer* printer) const {
+  if (variables_.find("default_constant_value") != variables_.end()) {
+    printer->Print(variables_,
+      "private static final $type$ $default_constant$ = $default_constant_value$;\n");
+  }
+  printer->Print(variables_,
+    "private $type$ $name$_ = $default_copy_if_needed$;\n"
+    "public $type$ get$capitalized_name$() {\n"
+    "  return $name$_;\n"
+    "}\n"
+    "public void set$capitalized_name$($type$ value) {\n"
+    "$null_check$"
+    "  $name$_ = value;\n"
+    "  $set_has$;\n"
+    "}\n"
+    "public boolean has$capitalized_name$() {\n"
+    "  return $get_has$;\n"
+    "}\n"
+    "public void clear$capitalized_name$() {\n"
+    "  $name$_ = $default_copy_if_needed$;\n"
+    "  $clear_has$;\n"
+    "}\n");
+}
+
+void AccessorPrimitiveFieldGenerator::
+GenerateClearCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$_ = $default_copy_if_needed$;\n");
+}
+
+void AccessorPrimitiveFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "set$capitalized_name$(input.read$capitalized_type$());\n");
+}
+
+void AccessorPrimitiveFieldGenerator::
+GenerateSerializationCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "if (has$capitalized_name$()) {\n"
+    "  output.write$capitalized_type$($number$, $name$_);\n"
+    "}\n");
+}
+
+void AccessorPrimitiveFieldGenerator::
+GenerateSerializedSizeCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "if (has$capitalized_name$()) {\n"
+    "  size += com.google.protobuf.nano.CodedOutputByteBufferNano\n"
+    "      .compute$capitalized_type$Size($number$, $name$_);\n"
+    "}\n");
+}
+
+string AccessorPrimitiveFieldGenerator::GetBoxedType() const {
+  return BoxedPrimitiveTypeName(GetJavaType(descriptor_));
+}
+
+// ===================================================================
+
 RepeatedPrimitiveFieldGenerator::
 RepeatedPrimitiveFieldGenerator(const FieldDescriptor* descriptor, const Params& params)
   : FieldGenerator(params), descriptor_(descriptor) {
@@ -412,7 +489,13 @@ GenerateMembers(io::Printer* printer) const {
 }
 
 void RepeatedPrimitiveFieldGenerator::
-GenerateParsingCode(io::Printer* printer) const {
+GenerateClearCode(io::Printer* printer) const {
+  printer->Print(variables_,
+    "$name$ = $default$;\n");
+}
+
+void RepeatedPrimitiveFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
   // First, figure out the length of the array, then parse.
   if (descriptor_->options().packed()) {
     printer->Print(variables_,
diff --git a/src/google/protobuf/compiler/javanano/javanano_primitive_field.h b/src/google/protobuf/compiler/javanano/javanano_primitive_field.h
index a56082d..b42e2f3 100644
--- a/src/google/protobuf/compiler/javanano/javanano_primitive_field.h
+++ b/src/google/protobuf/compiler/javanano/javanano_primitive_field.h
@@ -51,7 +51,8 @@ class PrimitiveFieldGenerator : public FieldGenerator {
 
   // implements FieldGenerator ---------------------------------------
   void GenerateMembers(io::Printer* printer) const;
-  void GenerateParsingCode(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
 
@@ -66,6 +67,28 @@ class PrimitiveFieldGenerator : public FieldGenerator {
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(PrimitiveFieldGenerator);
 };
 
+class AccessorPrimitiveFieldGenerator : public FieldGenerator {
+ public:
+  explicit AccessorPrimitiveFieldGenerator( const FieldDescriptor* descriptor,
+      const Params &params, int has_bit_index);
+  ~AccessorPrimitiveFieldGenerator();
+
+  // implements FieldGenerator ---------------------------------------
+  void GenerateMembers(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateSerializationCode(io::Printer* printer) const;
+  void GenerateSerializedSizeCode(io::Printer* printer) const;
+
+  string GetBoxedType() const;
+
+ private:
+  const FieldDescriptor* descriptor_;
+  map<string, string> variables_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(AccessorPrimitiveFieldGenerator);
+};
+
 class RepeatedPrimitiveFieldGenerator : public FieldGenerator {
  public:
   explicit RepeatedPrimitiveFieldGenerator(const FieldDescriptor* descriptor, const Params& params);
@@ -73,7 +96,8 @@ class RepeatedPrimitiveFieldGenerator : public FieldGenerator {
 
   // implements FieldGenerator ---------------------------------------
   void GenerateMembers(io::Printer* printer) const;
-  void GenerateParsingCode(io::Printer* printer) const;
+  void GenerateClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
 
diff --git a/src/google/protobuf/unittest_accessors_nano.proto b/src/google/protobuf/unittest_accessors_nano.proto
new file mode 100644
index 0000000..875af25
--- /dev/null
+++ b/src/google/protobuf/unittest_accessors_nano.proto
@@ -0,0 +1,116 @@
+// 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.
+
+// Author: maxtroy@google.com (Max Cai)
+
+package protobuf_unittest;
+
+option java_package = "com.google.protobuf.nano";
+option java_outer_classname = "NanoAccessorsOuterClass";
+
+message TestNanoAccessors {
+
+  message NestedMessage {
+    optional int32 bb = 1;
+  }
+
+  enum NestedEnum {
+    FOO = 1;
+    BAR = 2;
+    BAZ = 3;
+  }
+
+  // Singular
+  optional int32  optional_int32    =  1;
+  optional string optional_string   = 14;
+  optional bytes  optional_bytes    = 15;
+
+  optional NestedMessage optional_nested_message = 18;
+
+  optional NestedEnum optional_nested_enum = 21;
+
+  // Repeated
+  repeated int32  repeated_int32    = 31;
+  repeated string repeated_string   = 44;
+  repeated bytes  repeated_bytes    = 45;
+
+  repeated NestedMessage repeated_nested_message  = 48;
+
+  repeated NestedEnum repeated_nested_enum  = 51;
+
+  // Singular with defaults
+  optional int32  default_int32    = 61 [default =  41    ];
+  optional string default_string   = 74 [default = "hello"];
+  optional bytes  default_bytes    = 75 [default = "world"];
+
+  optional float default_float_nan = 99  [default =  nan];
+
+  optional NestedEnum default_nested_enum = 81 [default = BAR];
+
+  // Required
+  required int32 id = 86;
+
+  // Add enough optional fields to make 2 bit fields in total
+  optional int32 filler100 = 100;
+  optional int32 filler101 = 101;
+  optional int32 filler102 = 102;
+  optional int32 filler103 = 103;
+  optional int32 filler104 = 104;
+  optional int32 filler105 = 105;
+  optional int32 filler106 = 106;
+  optional int32 filler107 = 107;
+  optional int32 filler108 = 108;
+  optional int32 filler109 = 109;
+  optional int32 filler110 = 110;
+  optional int32 filler111 = 111;
+  optional int32 filler112 = 112;
+  optional int32 filler113 = 113;
+  optional int32 filler114 = 114;
+  optional int32 filler115 = 115;
+  optional int32 filler116 = 116;
+  optional int32 filler117 = 117;
+  optional int32 filler118 = 118;
+  optional int32 filler119 = 119;
+  optional int32 filler120 = 120;
+  optional int32 filler121 = 121;
+  optional int32 filler122 = 122;
+  optional int32 filler123 = 123;
+  optional int32 filler124 = 124;
+  optional int32 filler125 = 125;
+  optional int32 filler126 = 126;
+  optional int32 filler127 = 127;
+  optional int32 filler128 = 128;
+  optional int32 filler129 = 129;
+  optional int32 filler130 = 130;
+
+  optional int32 before_bit_field_check = 139;
+  optional int32 bit_field_check = 140;
+  optional int32 after_bit_field_check = 141;
+}