1 files changed, 185 insertions, 0 deletions
diff --git a/python/google/protobuf/symbol_database.py b/python/google/protobuf/symbol_database.py
new file mode 100644
index 0000000..4c70b39
--- /dev/null
+++ b/python/google/protobuf/symbol_database.py
@@ -0,0 +1,185 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# https://developers.google.com/protocol-buffers/
+#
+# 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.
+
+"""A database of Python protocol buffer generated symbols.
+
+SymbolDatabase makes it easy to create new instances of a registered type, given
+only the type's protocol buffer symbol name. Once all symbols are registered,
+they can be accessed using either the MessageFactory interface which
+SymbolDatabase exposes, or the DescriptorPool interface of the underlying
+pool.
+
+Example usage:
+
+  db = symbol_database.SymbolDatabase()
+
+  # Register symbols of interest, from one or multiple files.
+  db.RegisterFileDescriptor(my_proto_pb2.DESCRIPTOR)
+  db.RegisterMessage(my_proto_pb2.MyMessage)
+  db.RegisterEnumDescriptor(my_proto_pb2.MyEnum.DESCRIPTOR)
+
+  # The database can be used as a MessageFactory, to generate types based on
+  # their name:
+  types = db.GetMessages(['my_proto.proto'])
+  my_message_instance = types['MyMessage']()
+
+  # The database's underlying descriptor pool can be queried, so it's not
+  # necessary to know a type's filename to be able to generate it:
+  filename = db.pool.FindFileContainingSymbol('MyMessage')
+  my_message_instance = db.GetMessages([filename])['MyMessage']()
+
+  # This functionality is also provided directly via a convenience method:
+  my_message_instance = db.GetSymbol('MyMessage')()
+"""
+
+
+from google.protobuf import descriptor_pool
+
+
+class SymbolDatabase(object):
+  """A database of Python generated symbols.
+
+  SymbolDatabase also models message_factory.MessageFactory.
+
+  The symbol database can be used to keep a global registry of all protocol
+  buffer types used within a program.
+  """
+
+  def __init__(self):
+    """Constructor."""
+
+    self._symbols = {}
+    self._symbols_by_file = {}
+    self.pool = descriptor_pool.DescriptorPool()
+
+  def RegisterMessage(self, message):
+    """Registers the given message type in the local database.
+
+    Args:
+      message: a message.Message, to be registered.
+
+    Returns:
+      The provided message.
+    """
+
+    desc = message.DESCRIPTOR
+    self._symbols[desc.full_name] = message
+    if desc.file.name not in self._symbols_by_file:
+      self._symbols_by_file[desc.file.name] = {}
+    self._symbols_by_file[desc.file.name][desc.full_name] = message
+    self.pool.AddDescriptor(desc)
+    return message
+
+  def RegisterEnumDescriptor(self, enum_descriptor):
+    """Registers the given enum descriptor in the local database.
+
+    Args:
+      enum_descriptor: a descriptor.EnumDescriptor.
+
+    Returns:
+      The provided descriptor.
+    """
+    self.pool.AddEnumDescriptor(enum_descriptor)
+    return enum_descriptor
+
+  def RegisterFileDescriptor(self, file_descriptor):
+    """Registers the given file descriptor in the local database.
+
+    Args:
+      file_descriptor: a descriptor.FileDescriptor.
+
+    Returns:
+      The provided descriptor.
+    """
+    self.pool.AddFileDescriptor(file_descriptor)
+
+  def GetSymbol(self, symbol):
+    """Tries to find a symbol in the local database.
+
+    Currently, this method only returns message.Message instances, however, if
+    may be extended in future to support other symbol types.
+
+    Args:
+      symbol: A str, a protocol buffer symbol.
+
+    Returns:
+      A Python class corresponding to the symbol.
+
+    Raises:
+      KeyError: if the symbol could not be found.
+    """
+
+    return self._symbols[symbol]
+
+  def GetPrototype(self, descriptor):
+    """Builds a proto2 message class based on the passed in descriptor.
+
+    Passing a descriptor with a fully qualified name matching a previous
+    invocation will cause the same class to be returned.
+
+    Args:
+      descriptor: The descriptor to build from.
+
+    Returns:
+      A class describing the passed in descriptor.
+    """
+
+    return self.GetSymbol(descriptor.full_name)
+
+  def GetMessages(self, files):
+    """Gets all the messages from a specified file.
+
+    This will find and resolve dependencies, failing if they are not registered
+    in the symbol database.
+
+
+    Args:
+      files: The file names to extract messages from.
+
+    Returns:
+      A dictionary mapping proto names to the message classes. This will include
+      any dependent messages as well as any messages defined in the same file as
+      a specified message.
+
+    Raises:
+      KeyError: if a file could not be found.
+    """
+
+    result = {}
+    for f in files:
+      result.update(self._symbols_by_file[f])
+    return result
+
+_DEFAULT = SymbolDatabase()
+
+
+def Default():
+  """Returns the default SymbolDatabase."""
+  return _DEFAULT