Renamed google.protobuf to protobuf26

third_party/google/protobuf/internal/python_message.py

-# 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.
-
-# Keep it Python2.5 compatible for GAE.
-#
-# Copyright 2007 Google Inc. All Rights Reserved.
-#
-# This code is meant to work on Python 2.4 and above only.
-#
-# TODO(robinson): Helpers for verbose, common checks like seeing if a
-# descriptor's cpp_type is CPPTYPE_MESSAGE.
-
-"""Contains a metaclass and helper functions used to create
-protocol message classes from Descriptor objects at runtime.
-
-Recall that a metaclass is the "type" of a class.
-(A class is to a metaclass what an instance is to a class.)
-
-In this case, we use the GeneratedProtocolMessageType metaclass
-to inject all the useful functionality into the classes
-output by the protocol compiler at compile-time.
-
-The upshot of all this is that the real implementation
-details for ALL pure-Python protocol buffers are *here in
-this file*.
-"""
-
-__author__ = 'robinson@google.com (Will Robinson)'
-
-import sys
-if sys.version_info[0] < 3:
-  try:
-    from cStringIO import StringIO as BytesIO
-  except ImportError:
-    from StringIO import StringIO as BytesIO
-  import copy_reg as copyreg
-else:
-  from io import BytesIO
-  import copyreg
-import struct
-import weakref
-
-# We use "as" to avoid name collisions with variables.
-from google.protobuf.internal import containers
-from google.protobuf.internal import decoder
-from google.protobuf.internal import encoder
-from google.protobuf.internal import enum_type_wrapper
-from google.protobuf.internal import message_listener as message_listener_mod
-from google.protobuf.internal import type_checkers
-from google.protobuf.internal import wire_format
-from google.protobuf import descriptor as descriptor_mod
-from google.protobuf import message as message_mod
-from google.protobuf import text_format
-
-_FieldDescriptor = descriptor_mod.FieldDescriptor
-
-
-def NewMessage(bases, descriptor, dictionary):
-  _AddClassAttributesForNestedExtensions(descriptor, dictionary)
-  _AddSlots(descriptor, dictionary)
-  return bases
-
-
-def InitMessage(descriptor, cls):
-  cls._decoders_by_tag = {}
-  cls._extensions_by_name = {}
-  cls._extensions_by_number = {}
-  if (descriptor.has_options and
-      descriptor.GetOptions().message_set_wire_format):
-    cls._decoders_by_tag[decoder.MESSAGE_SET_ITEM_TAG] = (
-        decoder.MessageSetItemDecoder(cls._extensions_by_number))
-
-  # Attach stuff to each FieldDescriptor for quick lookup later on.
-  for field in descriptor.fields:
-    _AttachFieldHelpers(cls, field)
-
-  _AddEnumValues(descriptor, cls)
-  _AddInitMethod(descriptor, cls)
-  _AddPropertiesForFields(descriptor, cls)
-  _AddPropertiesForExtensions(descriptor, cls)
-  _AddStaticMethods(cls)
-  _AddMessageMethods(descriptor, cls)
-  _AddPrivateHelperMethods(descriptor, cls)
-  copyreg.pickle(cls, lambda obj: (cls, (), obj.__getstate__()))
-
-
-# Stateless helpers for GeneratedProtocolMessageType below.
-# Outside clients should not access these directly.
-#
-# I opted not to make any of these methods on the metaclass, to make it more
-# clear that I'm not really using any state there and to keep clients from
-# thinking that they have direct access to these construction helpers.
-
-
-def _PropertyName(proto_field_name):
-  """Returns the name of the public property attribute which
-  clients can use to get and (in some cases) set the value
-  of a protocol message field.
-
-  Args:
-    proto_field_name: The protocol message field name, exactly
-      as it appears (or would appear) in a .proto file.
-  """
-  # TODO(robinson): Escape Python keywords (e.g., yield), and test this support.
-  # nnorwitz makes my day by writing:
-  # """
-  # FYI.  See the keyword module in the stdlib. This could be as simple as:
-  #
-  # if keyword.iskeyword(proto_field_name):
-  #   return proto_field_name + "_"
-  # return proto_field_name
-  # """
-  # Kenton says:  The above is a BAD IDEA.  People rely on being able to use
-  #   getattr() and setattr() to reflectively manipulate field values.  If we
-  #   rename the properties, then every such user has to also make sure to apply
-  #   the same transformation.  Note that currently if you name a field "yield",
-  #   you can still access it just fine using getattr/setattr -- it's not even
-  #   that cumbersome to do so.
-  # TODO(kenton):  Remove this method entirely if/when everyone agrees with my
-  #   position.
-  return proto_field_name
-
-
-def _VerifyExtensionHandle(message, extension_handle):
-  """Verify that the given extension handle is valid."""
-
-  if not isinstance(extension_handle, _FieldDescriptor):
-    raise KeyError('HasExtension() expects an extension handle, got: %s' %
-                   extension_handle)
-
-  if not extension_handle.is_extension:
-    raise KeyError('"%s" is not an extension.' % extension_handle.full_name)
-
-  if not extension_handle.containing_type:
-    raise KeyError('"%s" is missing a containing_type.'
-                   % extension_handle.full_name)
-
-  if extension_handle.containing_type is not message.DESCRIPTOR:
-    raise KeyError('Extension "%s" extends message type "%s", but this '
-                   'message is of type "%s".' %
-                   (extension_handle.full_name,
-                    extension_handle.containing_type.full_name,
-                    message.DESCRIPTOR.full_name))
-
-
-def _AddSlots(message_descriptor, dictionary):
-  """Adds a __slots__ entry to dictionary, containing the names of all valid
-  attributes for this message type.
-
-  Args:
-    message_descriptor: A Descriptor instance describing this message type.
-    dictionary: Class dictionary to which we'll add a '__slots__' entry.
-  """
-  dictionary['__slots__'] = ['_cached_byte_size',
-                             '_cached_byte_size_dirty',
-                             '_fields',
-                             '_unknown_fields',
-                             '_is_present_in_parent',
-                             '_listener',
-                             '_listener_for_children',
-                             '__weakref__',
-                             '_oneofs']
-
-
-def _IsMessageSetExtension(field):
-  return (field.is_extension and
-          field.containing_type.has_options and
-          field.containing_type.GetOptions().message_set_wire_format and
-          field.type == _FieldDescriptor.TYPE_MESSAGE and
-          field.message_type == field.extension_scope and
-          field.label == _FieldDescriptor.LABEL_OPTIONAL)
-
-
-def _AttachFieldHelpers(cls, field_descriptor):
-  is_repeated = (field_descriptor.label == _FieldDescriptor.LABEL_REPEATED)
-  is_packed = (field_descriptor.has_options and
-               field_descriptor.GetOptions().packed)
-
-  if _IsMessageSetExtension(field_descriptor):
-    field_encoder = encoder.MessageSetItemEncoder(field_descriptor.number)
-    sizer = encoder.MessageSetItemSizer(field_descriptor.number)
-  else:
-    field_encoder = type_checkers.TYPE_TO_ENCODER[field_descriptor.type](
-        field_descriptor.number, is_repeated, is_packed)
-    sizer = type_checkers.TYPE_TO_SIZER[field_descriptor.type](
-        field_descriptor.number, is_repeated, is_packed)
-
-  field_descriptor._encoder = field_encoder
-  field_descriptor._sizer = sizer
-  field_descriptor._default_constructor = _DefaultValueConstructorForField(
-      field_descriptor)
-
-  def AddDecoder(wiretype, is_packed):
-    tag_bytes = encoder.TagBytes(field_descriptor.number, wiretype)
-    cls._decoders_by_tag[tag_bytes] = (
-        type_checkers.TYPE_TO_DECODER[field_descriptor.type](
-            field_descriptor.number, is_repeated, is_packed,
-            field_descriptor, field_descriptor._default_constructor))
-
-  AddDecoder(type_checkers.FIELD_TYPE_TO_WIRE_TYPE[field_descriptor.type],
-             False)
-
-  if is_repeated and wire_format.IsTypePackable(field_descriptor.type):
-    # To support wire compatibility of adding packed = true, add a decoder for
-    # packed values regardless of the field's options.
-    AddDecoder(wire_format.WIRETYPE_LENGTH_DELIMITED, True)
-
-
-def _AddClassAttributesForNestedExtensions(descriptor, dictionary):
-  extension_dict = descriptor.extensions_by_name
-  for extension_name, extension_field in extension_dict.iteritems():
-    assert extension_name not in dictionary
-    dictionary[extension_name] = extension_field
-
-
-def _AddEnumValues(descriptor, cls):
-  """Sets class-level attributes for all enum fields defined in this message.
-
-  Also exporting a class-level object that can name enum values.
-
-  Args:
-    descriptor: Descriptor object for this message type.
-    cls: Class we're constructing for this message type.
-  """
-  for enum_type in descriptor.enum_types:
-    setattr(cls, enum_type.name, enum_type_wrapper.EnumTypeWrapper(enum_type))
-    for enum_value in enum_type.values:
-      setattr(cls, enum_value.name, enum_value.number)
-
-
-def _DefaultValueConstructorForField(field):
-  """Returns a function which returns a default value for a field.
-
-  Args:
-    field: FieldDescriptor object for this field.
-
-  The returned function has one argument:
-    message: Message instance containing this field, or a weakref proxy
-      of same.
-
-  That function in turn returns a default value for this field.  The default
-    value may refer back to |message| via a weak reference.
-  """
-
-  if field.label == _FieldDescriptor.LABEL_REPEATED:
-    if field.has_default_value and field.default_value != []:
-      raise ValueError('Repeated field default value not empty list: %s' % (
-          field.default_value))
-    if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-      # We can't look at _concrete_class yet since it might not have
-      # been set.  (Depends on order in which we initialize the classes).
-      message_type = field.message_type
-      def MakeRepeatedMessageDefault(message):
-        return containers.RepeatedCompositeFieldContainer(
-            message._listener_for_children, field.message_type)
-      return MakeRepeatedMessageDefault
-    else:
-      type_checker = type_checkers.GetTypeChecker(field)
-      def MakeRepeatedScalarDefault(message):
-        return containers.RepeatedScalarFieldContainer(
-            message._listener_for_children, type_checker)
-      return MakeRepeatedScalarDefault
-
-  if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-    # _concrete_class may not yet be initialized.
-    message_type = field.message_type
-    def MakeSubMessageDefault(message):
-      result = message_type._concrete_class()
-      result._SetListener(message._listener_for_children)
-      return result
-    return MakeSubMessageDefault
-
-  def MakeScalarDefault(message):
-    # TODO(protobuf-team): This may be broken since there may not be
-    # default_value.  Combine with has_default_value somehow.
-    return field.default_value
-  return MakeScalarDefault
-
-
-def _AddInitMethod(message_descriptor, cls):
-  """Adds an __init__ method to cls."""
-  fields = message_descriptor.fields
-  def init(self, **kwargs):
-    self._cached_byte_size = 0
-    self._cached_byte_size_dirty = len(kwargs) > 0
-    self._fields = {}
-    # Contains a mapping from oneof field descriptors to the descriptor
-    # of the currently set field in that oneof field.
-    self._oneofs = {}
-
-    # _unknown_fields is () when empty for efficiency, and will be turned into
-    # a list if fields are added.
-    self._unknown_fields = ()
-    self._is_present_in_parent = False
-    self._listener = message_listener_mod.NullMessageListener()
-    self._listener_for_children = _Listener(self)
-    for field_name, field_value in kwargs.iteritems():
-      field = _GetFieldByName(message_descriptor, field_name)
-      if field is None:
-        raise TypeError("%s() got an unexpected keyword argument '%s'" %
-                        (message_descriptor.name, field_name))
-      if field.label == _FieldDescriptor.LABEL_REPEATED:
-        copy = field._default_constructor(self)
-        if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:  # Composite
-          for val in field_value:
-            copy.add().MergeFrom(val)
-        else:  # Scalar
-          copy.extend(field_value)
-        self._fields[field] = copy
-      elif field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-        copy = field._default_constructor(self)
-        copy.MergeFrom(field_value)
-        self._fields[field] = copy
-      else:
-        setattr(self, field_name, field_value)
-
-  init.__module__ = None
-  init.__doc__ = None
-  cls.__init__ = init
-
-
-def _GetFieldByName(message_descriptor, field_name):
-  """Returns a field descriptor by field name.
-
-  Args:
-    message_descriptor: A Descriptor describing all fields in message.
-    field_name: The name of the field to retrieve.
-  Returns:
-    The field descriptor associated with the field name.
-  """
-  try:
-    return message_descriptor.fields_by_name[field_name]
-  except KeyError:
-    raise ValueError('Protocol message has no "%s" field.' % field_name)
-
-
-def _AddPropertiesForFields(descriptor, cls):
-  """Adds properties for all fields in this protocol message type."""
-  for field in descriptor.fields:
-    _AddPropertiesForField(field, cls)
-
-  if descriptor.is_extendable:
-    # _ExtensionDict is just an adaptor with no state so we allocate a new one
-    # every time it is accessed.
-    cls.Extensions = property(lambda self: _ExtensionDict(self))
-
-
-def _AddPropertiesForField(field, cls):
-  """Adds a public property for a protocol message field.
-  Clients can use this property to get and (in the case
-  of non-repeated scalar fields) directly set the value
-  of a protocol message field.
-
-  Args:
-    field: A FieldDescriptor for this field.
-    cls: The class we're constructing.
-  """
-  # Catch it if we add other types that we should
-  # handle specially here.
-  assert _FieldDescriptor.MAX_CPPTYPE == 10
-
-  constant_name = field.name.upper() + "_FIELD_NUMBER"
-  setattr(cls, constant_name, field.number)
-
-  if field.label == _FieldDescriptor.LABEL_REPEATED:
-    _AddPropertiesForRepeatedField(field, cls)
-  elif field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-    _AddPropertiesForNonRepeatedCompositeField(field, cls)
-  else:
-    _AddPropertiesForNonRepeatedScalarField(field, cls)
-
-
-def _AddPropertiesForRepeatedField(field, cls):
-  """Adds a public property for a "repeated" protocol message field.  Clients
-  can use this property to get the value of the field, which will be either a
-  _RepeatedScalarFieldContainer or _RepeatedCompositeFieldContainer (see
-  below).
-
-  Note that when clients add values to these containers, we perform
-  type-checking in the case of repeated scalar fields, and we also set any
-  necessary "has" bits as a side-effect.
-
-  Args:
-    field: A FieldDescriptor for this field.
-    cls: The class we're constructing.
-  """
-  proto_field_name = field.name
-  property_name = _PropertyName(proto_field_name)
-
-  def getter(self):
-    field_value = self._fields.get(field)
-    if field_value is None:
-      # Construct a new object to represent this field.
-      field_value = field._default_constructor(self)
-
-      # Atomically check if another thread has preempted us and, if not, swap
-      # in the new object we just created.  If someone has preempted us, we
-      # take that object and discard ours.
-      # WARNING:  We are relying on setdefault() being atomic.  This is true
-      #   in CPython but we haven't investigated others.  This warning appears
-      #   in several other locations in this file.
-      field_value = self._fields.setdefault(field, field_value)
-    return field_value
-  getter.__module__ = None
-  getter.__doc__ = 'Getter for %s.' % proto_field_name
-
-  # We define a setter just so we can throw an exception with a more
-  # helpful error message.
-  def setter(self, new_value):
-    raise AttributeError('Assignment not allowed to repeated field '
-                         '"%s" in protocol message object.' % proto_field_name)
-
-  doc = 'Magic attribute generated for "%s" proto field.' % proto_field_name
-  setattr(cls, property_name, property(getter, setter, doc=doc))
-
-
-def _AddPropertiesForNonRepeatedScalarField(field, cls):
-  """Adds a public property for a nonrepeated, scalar protocol message field.
-  Clients can use this property to get and directly set the value of the field.
-  Note that when the client sets the value of a field by using this property,
-  all necessary "has" bits are set as a side-effect, and we also perform
-  type-checking.
-
-  Args:
-    field: A FieldDescriptor for this field.
-    cls: The class we're constructing.
-  """
-  proto_field_name = field.name
-  property_name = _PropertyName(proto_field_name)
-  type_checker = type_checkers.GetTypeChecker(field)
-  default_value = field.default_value
-  valid_values = set()
-
-  def getter(self):
-    # TODO(protobuf-team): This may be broken since there may not be
-    # default_value.  Combine with has_default_value somehow.
-    return self._fields.get(field, default_value)
-  getter.__module__ = None
-  getter.__doc__ = 'Getter for %s.' % proto_field_name
-  def field_setter(self, new_value):
-    # pylint: disable=protected-access
-    self._fields[field] = type_checker.CheckValue(new_value)
-    # Check _cached_byte_size_dirty inline to improve performance, since scalar
-    # setters are called frequently.
-    if not self._cached_byte_size_dirty:
-      self._Modified()
-
-  if field.containing_oneof is not None:
-    def setter(self, new_value):
-      field_setter(self, new_value)
-      self._UpdateOneofState(field)
-  else:
-    setter = field_setter
-
-  setter.__module__ = None
-  setter.__doc__ = 'Setter for %s.' % proto_field_name
-
-  # Add a property to encapsulate the getter/setter.
-  doc = 'Magic attribute generated for "%s" proto field.' % proto_field_name
-  setattr(cls, property_name, property(getter, setter, doc=doc))
-
-
-def _AddPropertiesForNonRepeatedCompositeField(field, cls):
-  """Adds a public property for a nonrepeated, composite protocol message field.
-  A composite field is a "group" or "message" field.
-
-  Clients can use this property to get the value of the field, but cannot
-  assign to the property directly.
-
-  Args:
-    field: A FieldDescriptor for this field.
-    cls: The class we're constructing.
-  """
-  # TODO(robinson): Remove duplication with similar method
-  # for non-repeated scalars.
-  proto_field_name = field.name
-  property_name = _PropertyName(proto_field_name)
-
-  # TODO(komarek): Can anyone explain to me why we cache the message_type this
-  # way, instead of referring to field.message_type inside of getter(self)?
-  # What if someone sets message_type later on (which makes for simpler
-  # dyanmic proto descriptor and class creation code).
-  message_type = field.message_type
-
-  def getter(self):
-    field_value = self._fields.get(field)
-    if field_value is None:
-      # Construct a new object to represent this field.
-      field_value = message_type._concrete_class()  # use field.message_type?
-      field_value._SetListener(
-          _OneofListener(self, field)
-          if field.containing_oneof is not None
-          else self._listener_for_children)
-
-      # Atomically check if another thread has preempted us and, if not, swap
-      # in the new object we just created.  If someone has preempted us, we
-      # take that object and discard ours.
-      # WARNING:  We are relying on setdefault() being atomic.  This is true
-      #   in CPython but we haven't investigated others.  This warning appears
-      #   in several other locations in this file.
-      field_value = self._fields.setdefault(field, field_value)
-    return field_value
-  getter.__module__ = None
-  getter.__doc__ = 'Getter for %s.' % proto_field_name
-
-  # We define a setter just so we can throw an exception with a more
-  # helpful error message.
-  def setter(self, new_value):
-    raise AttributeError('Assignment not allowed to composite field '
-                         '"%s" in protocol message object.' % proto_field_name)
-
-  # Add a property to encapsulate the getter.
-  doc = 'Magic attribute generated for "%s" proto field.' % proto_field_name
-  setattr(cls, property_name, property(getter, setter, doc=doc))
-
-
-def _AddPropertiesForExtensions(descriptor, cls):
-  """Adds properties for all fields in this protocol message type."""
-  extension_dict = descriptor.extensions_by_name
-  for extension_name, extension_field in extension_dict.iteritems():
-    constant_name = extension_name.upper() + "_FIELD_NUMBER"
-    setattr(cls, constant_name, extension_field.number)
-
-
-def _AddStaticMethods(cls):
-  # TODO(robinson): This probably needs to be thread-safe(?)
-  def RegisterExtension(extension_handle):
-    extension_handle.containing_type = cls.DESCRIPTOR
-    _AttachFieldHelpers(cls, extension_handle)
-
-    # Try to insert our extension, failing if an extension with the same number
-    # already exists.
-    actual_handle = cls._extensions_by_number.setdefault(
-        extension_handle.number, extension_handle)
-    if actual_handle is not extension_handle:
-      raise AssertionError(
-          'Extensions "%s" and "%s" both try to extend message type "%s" with '
-          'field number %d.' %
-          (extension_handle.full_name, actual_handle.full_name,
-           cls.DESCRIPTOR.full_name, extension_handle.number))
-
-    cls._extensions_by_name[extension_handle.full_name] = extension_handle
-
-    handle = extension_handle  # avoid line wrapping
-    if _IsMessageSetExtension(handle):
-      # MessageSet extension.  Also register under type name.
-      cls._extensions_by_name[
-          extension_handle.message_type.full_name] = extension_handle
-
-  cls.RegisterExtension = staticmethod(RegisterExtension)
-
-  def FromString(s):
-    message = cls()
-    message.MergeFromString(s)
-    return message
-  cls.FromString = staticmethod(FromString)
-
-
-def _IsPresent(item):
-  """Given a (FieldDescriptor, value) tuple from _fields, return true if the
-  value should be included in the list returned by ListFields()."""
-
-  if item[0].label == _FieldDescriptor.LABEL_REPEATED:
-    return bool(item[1])
-  elif item[0].cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-    return item[1]._is_present_in_parent
-  else:
-    return True
-
-
-def _AddListFieldsMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-
-  def ListFields(self):
-    all_fields = [item for item in self._fields.iteritems() if _IsPresent(item)]
-    all_fields.sort(key = lambda item: item[0].number)
-    return all_fields
-
-  cls.ListFields = ListFields
-
-
-def _AddHasFieldMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-
-  singular_fields = {}
-  for field in message_descriptor.fields:
-    if field.label != _FieldDescriptor.LABEL_REPEATED:
-      singular_fields[field.name] = field
-  # Fields inside oneofs are never repeated (enforced by the compiler).
-  for field in message_descriptor.oneofs:
-    singular_fields[field.name] = field
-
-  def HasField(self, field_name):
-    try:
-      field = singular_fields[field_name]
-    except KeyError:
-      raise ValueError(
-          'Protocol message has no singular "%s" field.' % field_name)
-
-    if isinstance(field, descriptor_mod.OneofDescriptor):
-      try:
-        return HasField(self, self._oneofs[field].name)
-      except KeyError:
-        return False
-    else:
-      if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-        value = self._fields.get(field)
-        return value is not None and value._is_present_in_parent
-      else:
-        return field in self._fields
-
-  cls.HasField = HasField
-
-
-def _AddClearFieldMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-  def ClearField(self, field_name):
-    try:
-      field = message_descriptor.fields_by_name[field_name]
-    except KeyError:
-      try:
-        field = message_descriptor.oneofs_by_name[field_name]
-        if field in self._oneofs:
-          field = self._oneofs[field]
-        else:
-          return
-      except KeyError:
-        raise ValueError('Protocol message has no "%s" field.' % field_name)
-
-    if field in self._fields:
-      # Note:  If the field is a sub-message, its listener will still point
-      #   at us.  That's fine, because the worst than can happen is that it
-      #   will call _Modified() and invalidate our byte size.  Big deal.
-      del self._fields[field]
-
-      if self._oneofs.get(field.containing_oneof, None) is field:
-        del self._oneofs[field.containing_oneof]
-
-    # Always call _Modified() -- even if nothing was changed, this is
-    # a mutating method, and thus calling it should cause the field to become
-    # present in the parent message.
-    self._Modified()
-
-  cls.ClearField = ClearField
-
-
-def _AddClearExtensionMethod(cls):
-  """Helper for _AddMessageMethods()."""
-  def ClearExtension(self, extension_handle):
-    _VerifyExtensionHandle(self, extension_handle)
-
-    # Similar to ClearField(), above.
-    if extension_handle in self._fields:
-      del self._fields[extension_handle]
-    self._Modified()
-  cls.ClearExtension = ClearExtension
-
-
-def _AddClearMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-  def Clear(self):
-    # Clear fields.
-    self._fields = {}
-    self._unknown_fields = ()
-    self._Modified()
-  cls.Clear = Clear
-
-
-def _AddHasExtensionMethod(cls):
-  """Helper for _AddMessageMethods()."""
-  def HasExtension(self, extension_handle):
-    _VerifyExtensionHandle(self, extension_handle)
-    if extension_handle.label == _FieldDescriptor.LABEL_REPEATED:
-      raise KeyError('"%s" is repeated.' % extension_handle.full_name)
-
-    if extension_handle.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-      value = self._fields.get(extension_handle)
-      return value is not None and value._is_present_in_parent
-    else:
-      return extension_handle in self._fields
-  cls.HasExtension = HasExtension
-
-
-def _AddEqualsMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-  def __eq__(self, other):
-    if (not isinstance(other, message_mod.Message) or
-        other.DESCRIPTOR != self.DESCRIPTOR):
-      return False
-
-    if self is other:
-      return True
-
-    if not self.ListFields() == other.ListFields():
-      return False
-
-    # Sort unknown fields because their order shouldn't affect equality test.
-    unknown_fields = list(self._unknown_fields)
-    unknown_fields.sort()
-    other_unknown_fields = list(other._unknown_fields)
-    other_unknown_fields.sort()
-
-    return unknown_fields == other_unknown_fields
-
-  cls.__eq__ = __eq__
-
-
-def _AddStrMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-  def __str__(self):
-    return text_format.MessageToString(self)
-  cls.__str__ = __str__
-
-
-def _AddUnicodeMethod(unused_message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-
-  def __unicode__(self):
-    return text_format.MessageToString(self, as_utf8=True).decode('utf-8')
-  cls.__unicode__ = __unicode__
-
-
-def _AddSetListenerMethod(cls):
-  """Helper for _AddMessageMethods()."""
-  def SetListener(self, listener):
-    if listener is None:
-      self._listener = message_listener_mod.NullMessageListener()
-    else:
-      self._listener = listener
-  cls._SetListener = SetListener
-
-
-def _BytesForNonRepeatedElement(value, field_number, field_type):
-  """Returns the number of bytes needed to serialize a non-repeated element.
-  The returned byte count includes space for tag information and any
-  other additional space associated with serializing value.
-
-  Args:
-    value: Value we're serializing.
-    field_number: Field number of this value.  (Since the field number
-      is stored as part of a varint-encoded tag, this has an impact
-      on the total bytes required to serialize the value).
-    field_type: The type of the field.  One of the TYPE_* constants
-      within FieldDescriptor.
-  """
-  try:
-    fn = type_checkers.TYPE_TO_BYTE_SIZE_FN[field_type]
-    return fn(field_number, value)
-  except KeyError:
-    raise message_mod.EncodeError('Unrecognized field type: %d' % field_type)
-
-
-def _AddByteSizeMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-
-  def ByteSize(self):
-    if not self._cached_byte_size_dirty:
-      return self._cached_byte_size
-
-    size = 0
-    for field_descriptor, field_value in self.ListFields():
-      size += field_descriptor._sizer(field_value)
-
-    for tag_bytes, value_bytes in self._unknown_fields:
-      size += len(tag_bytes) + len(value_bytes)
-
-    self._cached_byte_size = size
-    self._cached_byte_size_dirty = False
-    self._listener_for_children.dirty = False
-    return size
-
-  cls.ByteSize = ByteSize
-
-
-def _AddSerializeToStringMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-
-  def SerializeToString(self):
-    # Check if the message has all of its required fields set.
-    errors = []
-    if not self.IsInitialized():
-      raise message_mod.EncodeError(
-          'Message %s is missing required fields: %s' % (
-          self.DESCRIPTOR.full_name, ','.join(self.FindInitializationErrors())))
-    return self.SerializePartialToString()
-  cls.SerializeToString = SerializeToString
-
-
-def _AddSerializePartialToStringMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-
-  def SerializePartialToString(self):
-    out = BytesIO()
-    self._InternalSerialize(out.write)
-    return out.getvalue()
-  cls.SerializePartialToString = SerializePartialToString
-
-  def InternalSerialize(self, write_bytes):
-    for field_descriptor, field_value in self.ListFields():
-      field_descriptor._encoder(write_bytes, field_value)
-    for tag_bytes, value_bytes in self._unknown_fields:
-      write_bytes(tag_bytes)
-      write_bytes(value_bytes)
-  cls._InternalSerialize = InternalSerialize
-
-
-def _AddMergeFromStringMethod(message_descriptor, cls):
-  """Helper for _AddMessageMethods()."""
-  def MergeFromString(self, serialized):
-    length = len(serialized)
-    try:
-      if self._InternalParse(serialized, 0, length) != length:
-        # The only reason _InternalParse would return early is if it
-        # encountered an end-group tag.
-        raise message_mod.DecodeError('Unexpected end-group tag.')
-    except (IndexError, TypeError):
-      # Now ord(buf[p:p+1]) == ord('') gets TypeError.
-      raise message_mod.DecodeError('Truncated message.')
-    except struct.error, e:
-      raise message_mod.DecodeError(e)
-    return length   # Return this for legacy reasons.
-  cls.MergeFromString = MergeFromString
-
-  local_ReadTag = decoder.ReadTag
-  local_SkipField = decoder.SkipField
-  decoders_by_tag = cls._decoders_by_tag
-
-  def InternalParse(self, buffer, pos, end):
-    self._Modified()
-    field_dict = self._fields
-    unknown_field_list = self._unknown_fields
-    while pos != end:
-      (tag_bytes, new_pos) = local_ReadTag(buffer, pos)
-      field_decoder = decoders_by_tag.get(tag_bytes)
-      if field_decoder is None:
-        value_start_pos = new_pos
-        new_pos = local_SkipField(buffer, new_pos, end, tag_bytes)
-        if new_pos == -1:
-          return pos
-        if not unknown_field_list:
-          unknown_field_list = self._unknown_fields = []
-        unknown_field_list.append((tag_bytes, buffer[value_start_pos:new_pos]))
-        pos = new_pos
-      else:
-        pos = field_decoder(buffer, new_pos, end, self, field_dict)
-    return pos
-  cls._InternalParse = InternalParse
-
-
-def _AddIsInitializedMethod(message_descriptor, cls):
-  """Adds the IsInitialized and FindInitializationError methods to the
-  protocol message class."""
-
-  required_fields = [field for field in message_descriptor.fields
-                           if field.label == _FieldDescriptor.LABEL_REQUIRED]
-
-  def IsInitialized(self, errors=None):
-    """Checks if all required fields of a message are set.
-
-    Args:
-      errors:  A list which, if provided, will be populated with the field
-               paths of all missing required fields.
-
-    Returns:
-      True iff the specified message has all required fields set.
-    """
-
-    # Performance is critical so we avoid HasField() and ListFields().
-
-    for field in required_fields:
-      if (field not in self._fields or
-          (field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE and
-           not self._fields[field]._is_present_in_parent)):
-        if errors is not None:
-          errors.extend(self.FindInitializationErrors())
-        return False
-
-    for field, value in list(self._fields.items()):  # dict can change size!
-      if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-        if field.label == _FieldDescriptor.LABEL_REPEATED:
-          for element in value:
-            if not element.IsInitialized():
-              if errors is not None:
-                errors.extend(self.FindInitializationErrors())
-              return False
-        elif value._is_present_in_parent and not value.IsInitialized():
-          if errors is not None:
-            errors.extend(self.FindInitializationErrors())
-          return False
-
-    return True
-
-  cls.IsInitialized = IsInitialized
-
-  def FindInitializationErrors(self):
-    """Finds required fields which are not initialized.
-
-    Returns:
-      A list of strings.  Each string is a path to an uninitialized field from
-      the top-level message, e.g. "foo.bar[5].baz".
-    """
-
-    errors = []  # simplify things
-
-    for field in required_fields:
-      if not self.HasField(field.name):
-        errors.append(field.name)
-
-    for field, value in self.ListFields():
-      if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-        if field.is_extension:
-          name = "(%s)" % field.full_name
-        else:
-          name = field.name
-
-        if field.label == _FieldDescriptor.LABEL_REPEATED:
-          for i in xrange(len(value)):
-            element = value[i]
-            prefix = "%s[%d]." % (name, i)
-            sub_errors = element.FindInitializationErrors()
-            errors += [ prefix + error for error in sub_errors ]
-        else:
-          prefix = name + "."
-          sub_errors = value.FindInitializationErrors()
-          errors += [ prefix + error for error in sub_errors ]
-
-    return errors
-
-  cls.FindInitializationErrors = FindInitializationErrors
-
-
-def _AddMergeFromMethod(cls):
-  LABEL_REPEATED = _FieldDescriptor.LABEL_REPEATED
-  CPPTYPE_MESSAGE = _FieldDescriptor.CPPTYPE_MESSAGE
-
-  def MergeFrom(self, msg):
-    if not isinstance(msg, cls):
-      raise TypeError(
-          "Parameter to MergeFrom() must be instance of same class: "
-          "expected %s got %s." % (cls.__name__, type(msg).__name__))
-
-    assert msg is not self
-    self._Modified()
-
-    fields = self._fields
-
-    for field, value in msg._fields.iteritems():
-      if field.label == LABEL_REPEATED:
-        field_value = fields.get(field)
-        if field_value is None:
-          # Construct a new object to represent this field.
-          field_value = field._default_constructor(self)
-          fields[field] = field_value
-        field_value.MergeFrom(value)
-      elif field.cpp_type == CPPTYPE_MESSAGE:
-        if value._is_present_in_parent:
-          field_value = fields.get(field)
-          if field_value is None:
-            # Construct a new object to represent this field.
-            field_value = field._default_constructor(self)
-            fields[field] = field_value
-          field_value.MergeFrom(value)
-      else:
-        self._fields[field] = value
-
-    if msg._unknown_fields:
-      if not self._unknown_fields:
-        self._unknown_fields = []
-      self._unknown_fields.extend(msg._unknown_fields)
-
-  cls.MergeFrom = MergeFrom
-
-
-def _AddWhichOneofMethod(message_descriptor, cls):
-  def WhichOneof(self, oneof_name):
-    """Returns the name of the currently set field inside a oneof, or None."""
-    try:
-      field = message_descriptor.oneofs_by_name[oneof_name]
-    except KeyError:
-      raise ValueError(
-          'Protocol message has no oneof "%s" field.' % oneof_name)
-
-    nested_field = self._oneofs.get(field, None)
-    if nested_field is not None and self.HasField(nested_field.name):
-      return nested_field.name
-    else:
-      return None
-
-  cls.WhichOneof = WhichOneof
-
-
-def _AddMessageMethods(message_descriptor, cls):
-  """Adds implementations of all Message methods to cls."""
-  _AddListFieldsMethod(message_descriptor, cls)
-  _AddHasFieldMethod(message_descriptor, cls)
-  _AddClearFieldMethod(message_descriptor, cls)
-  if message_descriptor.is_extendable:
-    _AddClearExtensionMethod(cls)
-    _AddHasExtensionMethod(cls)
-  _AddClearMethod(message_descriptor, cls)
-  _AddEqualsMethod(message_descriptor, cls)
-  _AddStrMethod(message_descriptor, cls)
-  _AddUnicodeMethod(message_descriptor, cls)
-  _AddSetListenerMethod(cls)
-  _AddByteSizeMethod(message_descriptor, cls)
-  _AddSerializeToStringMethod(message_descriptor, cls)
-  _AddSerializePartialToStringMethod(message_descriptor, cls)
-  _AddMergeFromStringMethod(message_descriptor, cls)
-  _AddIsInitializedMethod(message_descriptor, cls)
-  _AddMergeFromMethod(cls)
-  _AddWhichOneofMethod(message_descriptor, cls)
-
-def _AddPrivateHelperMethods(message_descriptor, cls):
-  """Adds implementation of private helper methods to cls."""
-
-  def Modified(self):
-    """Sets the _cached_byte_size_dirty bit to true,
-    and propagates this to our listener iff this was a state change.
-    """
-
-    # Note:  Some callers check _cached_byte_size_dirty before calling
-    #   _Modified() as an extra optimization.  So, if this method is ever
-    #   changed such that it does stuff even when _cached_byte_size_dirty is
-    #   already true, the callers need to be updated.
-    if not self._cached_byte_size_dirty:
-      self._cached_byte_size_dirty = True
-      self._listener_for_children.dirty = True
-      self._is_present_in_parent = True
-      self._listener.Modified()
-
-  def _UpdateOneofState(self, field):
-    """Sets field as the active field in its containing oneof.
-
-    Will also delete currently active field in the oneof, if it is different
-    from the argument. Does not mark the message as modified.
-    """
-    other_field = self._oneofs.setdefault(field.containing_oneof, field)
-    if other_field is not field:
-      del self._fields[other_field]
-      self._oneofs[field.containing_oneof] = field
-
-  cls._Modified = Modified
-  cls.SetInParent = Modified
-  cls._UpdateOneofState = _UpdateOneofState
-
-
-class _Listener(object):
-
-  """MessageListener implementation that a parent message registers with its
-  child message.
-
-  In order to support semantics like:
-
-    foo.bar.baz.qux = 23
-    assert foo.HasField('bar')
-
-  ...child objects must have back references to their parents.
-  This helper class is at the heart of this support.
-  """
-
-  def __init__(self, parent_message):
-    """Args:
-      parent_message: The message whose _Modified() method we should call when
-        we receive Modified() messages.
-    """
-    # This listener establishes a back reference from a child (contained) object
-    # to its parent (containing) object.  We make this a weak reference to avoid
-    # creating cyclic garbage when the client finishes with the 'parent' object
-    # in the tree.
-    if isinstance(parent_message, weakref.ProxyType):
-      self._parent_message_weakref = parent_message
-    else:
-      self._parent_message_weakref = weakref.proxy(parent_message)
-
-    # As an optimization, we also indicate directly on the listener whether
-    # or not the parent message is dirty.  This way we can avoid traversing
-    # up the tree in the common case.
-    self.dirty = False
-
-  def Modified(self):
-    if self.dirty:
-      return
-    try:
-      # Propagate the signal to our parents iff this is the first field set.
-      self._parent_message_weakref._Modified()
-    except ReferenceError:
-      # We can get here if a client has kept a reference to a child object,
-      # and is now setting a field on it, but the child's parent has been
-      # garbage-collected.  This is not an error.
-      pass
-
-
-class _OneofListener(_Listener):
-  """Special listener implementation for setting composite oneof fields."""
-
-  def __init__(self, parent_message, field):
-    """Args:
-      parent_message: The message whose _Modified() method we should call when
-        we receive Modified() messages.
-      field: The descriptor of the field being set in the parent message.
-    """
-    super(_OneofListener, self).__init__(parent_message)
-    self._field = field
-
-  def Modified(self):
-    """Also updates the state of the containing oneof in the parent message."""
-    try:
-      self._parent_message_weakref._UpdateOneofState(self._field)
-      super(_OneofListener, self).Modified()
-    except ReferenceError:
-      pass
-
-
-# TODO(robinson): Move elsewhere?  This file is getting pretty ridiculous...
-# TODO(robinson): Unify error handling of "unknown extension" crap.
-# TODO(robinson): Support iteritems()-style iteration over all
-# extensions with the "has" bits turned on?
-class _ExtensionDict(object):
-
-  """Dict-like container for supporting an indexable "Extensions"
-  field on proto instances.
-
-  Note that in all cases we expect extension handles to be
-  FieldDescriptors.
-  """
-
-  def __init__(self, extended_message):
-    """extended_message: Message instance for which we are the Extensions dict.
-    """
-
-    self._extended_message = extended_message
-
-  def __getitem__(self, extension_handle):
-    """Returns the current value of the given extension handle."""
-
-    _VerifyExtensionHandle(self._extended_message, extension_handle)
-
-    result = self._extended_message._fields.get(extension_handle)
-    if result is not None:
-      return result
-
-    if extension_handle.label == _FieldDescriptor.LABEL_REPEATED:
-      result = extension_handle._default_constructor(self._extended_message)
-    elif extension_handle.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
-      result = extension_handle.message_type._concrete_class()
-      try:
-        result._SetListener(self._extended_message._listener_for_children)
-      except ReferenceError:
-        pass
-    else:
-      # Singular scalar -- just return the default without inserting into the
-      # dict.
-      return extension_handle.default_value
-
-    # Atomically check if another thread has preempted us and, if not, swap
-    # in the new object we just created.  If someone has preempted us, we
-    # take that object and discard ours.
-    # WARNING:  We are relying on setdefault() being atomic.  This is true
-    #   in CPython but we haven't investigated others.  This warning appears
-    #   in several other locations in this file.
-    result = self._extended_message._fields.setdefault(
-        extension_handle, result)
-
-    return result
-
-  def __eq__(self, other):
-    if not isinstance(other, self.__class__):
-      return False
-
-    my_fields = self._extended_message.ListFields()
-    other_fields = other._extended_message.ListFields()
-
-    # Get rid of non-extension fields.
-    my_fields    = [ field for field in my_fields    if field.is_extension ]
-    other_fields = [ field for field in other_fields if field.is_extension ]
-
-    return my_fields == other_fields
-
-  def __ne__(self, other):
-    return not self == other
-
-  def __hash__(self):
-    raise TypeError('unhashable object')
-
-  # Note that this is only meaningful for non-repeated, scalar extension
-  # fields.  Note also that we may have to call _Modified() when we do
-  # successfully set a field this way, to set any necssary "has" bits in the
-  # ancestors of the extended message.
-  def __setitem__(self, extension_handle, value):
-    """If extension_handle specifies a non-repeated, scalar extension
-    field, sets the value of that field.
-    """
-
-    _VerifyExtensionHandle(self._extended_message, extension_handle)
-
-    if (extension_handle.label == _FieldDescriptor.LABEL_REPEATED or
-        extension_handle.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE):
-      raise TypeError(
-          'Cannot assign to extension "%s" because it is a repeated or '
-          'composite type.' % extension_handle.full_name)
-
-    # It's slightly wasteful to lookup the type checker each time,
-    # but we expect this to be a vanishingly uncommon case anyway.
-    type_checker = type_checkers.GetTypeChecker(
-        extension_handle)
-    # pylint: disable=protected-access
-    self._extended_message._fields[extension_handle] = (
-      type_checker.CheckValue(value))
-    self._extended_message._Modified()
-
-  def _FindExtensionByName(self, name):
-    """Tries to find a known extension with the specified name.
-
-    Args:
-      name: Extension full name.
-
-    Returns:
-      Extension field descriptor.
-    """
-    return self._extended_message._extensions_by_name.get(name, None)