text: # 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.
  
  """Provides DescriptorPool to use as a container for proto2 descriptors.
  
  The DescriptorPool is used in conjection with a DescriptorDatabase to maintain
  a collection of protocol buffer descriptors for use when dynamically creating
  message types at runtime.
  
  For most applications protocol buffers should be used via modules generated by
  the protocol buffer compiler tool. This should only be used when the type of
  protocol buffers used in an application or library cannot be predetermined.
  
  Below is a straightforward example on how to use this class:
  
    pool = DescriptorPool()
    file_descriptor_protos = [ ... ]
    for file_descriptor_proto in file_descriptor_protos:
      pool.Add(file_descriptor_proto)
    my_message_descriptor = pool.FindMessageTypeByName('some.package.MessageType')
  
  The message descriptor can be used in conjunction with the message_factory
  module in order to create a protocol buffer class that can be encoded and
  decoded.
  
  If you want to get a Python class for the specified proto, use the
  helper functions inside google.protobuf.message_factory
  directly instead of this class.
  """
  
  __author__ = 'matthewtoia@google.com (Matt Toia)'
  
  import collections
  
  from google.protobuf import descriptor
  from google.protobuf import descriptor_database
  from google.protobuf import text_encoding
  
  
  _USE_C_DESCRIPTORS = descriptor._USE_C_DESCRIPTORS  # pylint: disable=protected-access
  
  
  def _NormalizeFullyQualifiedName(name):
    """Remove leading period from fully-qualified type name.
  
    Due to b/13860351 in descriptor_database.py, types in the root namespace are
    generated with a leading period. This function removes that prefix.
  
    Args:
      name: A str, the fully-qualified symbol name.
  
    Returns:
      A str, the normalized fully-qualified symbol name.
    """
    return name.lstrip('.')
  
  
  def _OptionsOrNone(descriptor_proto):
    """Returns the value of the field `options`, or None if it is not set."""
    if descriptor_proto.HasField('options'):
      return descriptor_proto.options
    else:
      return None
  
  
  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 == descriptor.FieldDescriptor.TYPE_MESSAGE and
            field.label == descriptor.FieldDescriptor.LABEL_OPTIONAL)
  
  
  class DescriptorPool(object):
    """A collection of protobufs dynamically constructed by descriptor protos."""
  
    if _USE_C_DESCRIPTORS:
  
      def __new__(cls, descriptor_db=None):
        # pylint: disable=protected-access
        return descriptor._message.DescriptorPool(descriptor_db)
  
    def __init__(self, descriptor_db=None):
      """Initializes a Pool of proto buffs.
  
      The descriptor_db argument to the constructor is provided to allow
      specialized file descriptor proto lookup code to be triggered on demand. An
      example would be an implementation which will read and compile a file
      specified in a call to FindFileByName() and not require the call to Add()
      at all. Results from this database will be cached internally here as well.
  
      Args:
        descriptor_db: A secondary source of file descriptors.
      """
  
      self._internal_db = descriptor_database.DescriptorDatabase()
      self._descriptor_db = descriptor_db
      self._descriptors = {}
      self._enum_descriptors = {}
      self._file_descriptors = {}
      self._toplevel_extensions = {}
      # We store extensions in two two-level mappings: The first key is the
      # descriptor of the message being extended, the second key is the extension
      # full name or its tag number.
      self._extensions_by_name = collections.defaultdict(dict)
      self._extensions_by_number = collections.defaultdict(dict)
  
    def Add(self, file_desc_proto):
      """Adds the FileDescriptorProto and its types to this pool.
  
      Args:
        file_desc_proto: The FileDescriptorProto to add.
      """
  
      self._internal_db.Add(file_desc_proto)
  
    def AddSerializedFile(self, serialized_file_desc_proto):
      """Adds the FileDescriptorProto and its types to this pool.
  
      Args:
        serialized_file_desc_proto: A bytes string, serialization of the
          FileDescriptorProto to add.
      """
  
      # pylint: disable=g-import-not-at-top
      from google.protobuf import descriptor_pb2
      file_desc_proto = descriptor_pb2.FileDescriptorProto.FromString(
          serialized_file_desc_proto)
      self.Add(file_desc_proto)
  
    def AddDescriptor(self, desc):
      """Adds a Descriptor to the pool, non-recursively.
  
      If the Descriptor contains nested messages or enums, the caller must
      explicitly register them. This method also registers the FileDescriptor
      associated with the message.
  
      Args:
        desc: A Descriptor.
      """
      if not isinstance(desc, descriptor.Descriptor):
        raise TypeError('Expected instance of descriptor.Descriptor.')
  
      self._descriptors[desc.full_name] = desc
      self.AddFileDescriptor(desc.file)
  
    def AddEnumDescriptor(self, enum_desc):
      """Adds an EnumDescriptor to the pool.
  
      This method also registers the FileDescriptor associated with the message.
  
      Args:
        enum_desc: An EnumDescriptor.
      """
  
      if not isinstance(enum_desc, descriptor.EnumDescriptor):
        raise TypeError('Expected instance of descriptor.EnumDescriptor.')
  
      self._enum_descriptors[enum_desc.full_name] = enum_desc
      self.AddFileDescriptor(enum_desc.file)
  
    def AddExtensionDescriptor(self, extension):
      """Adds a FieldDescriptor describing an extension to the pool.
  
      Args:
        extension: A FieldDescriptor.
  
      Raises:
        AssertionError: when another extension with the same number extends the
          same message.
        TypeError: when the specified extension is not a
          descriptor.FieldDescriptor.
      """
      if not (isinstance(extension, descriptor.FieldDescriptor) and
              extension.is_extension):
        raise TypeError('Expected an extension descriptor.')
  
      if extension.extension_scope is None:
        self._toplevel_extensions[extension.full_name] = extension
  
      try:
        existing_desc = self._extensions_by_number[
            extension.containing_type][extension.number]
      except KeyError:
        pass
      else:
        if extension is not existing_desc:
          raise AssertionError(
              'Extensions "%s" and "%s" both try to extend message type "%s" '
              'with field number %d.' %
              (extension.full_name, existing_desc.full_name,
               extension.containing_type.full_name, extension.number))
  
      self._extensions_by_number[extension.containing_type][
          extension.number] = extension
      self._extensions_by_name[extension.containing_type][
          extension.full_name] = extension
  
      # Also register MessageSet extensions with the type name.
      if _IsMessageSetExtension(extension):
        self._extensions_by_name[extension.containing_type][
            extension.message_type.full_name] = extension
  
    def AddFileDescriptor(self, file_desc):
      """Adds a FileDescriptor to the pool, non-recursively.
  
      If the FileDescriptor contains messages or enums, the caller must explicitly
      register them.
  
      Args:
        file_desc: A FileDescriptor.
      """
  
      if not isinstance(file_desc, descriptor.FileDescriptor):
        raise TypeError('Expected instance of descriptor.FileDescriptor.')
      self._file_descriptors[file_desc.name] = file_desc
  
    def FindFileByName(self, file_name):
      """Gets a FileDescriptor by file name.
  
      Args:
        file_name: The path to the file to get a descriptor for.
  
      Returns:
        A FileDescriptor for the named file.
  
      Raises:
        KeyError: if the file can not be found in the pool.
      """
  
      try:
        return self._file_descriptors[file_name]
      except KeyError:
        pass
  
      try:
        file_proto = self._internal_db.FindFileByName(file_name)
      except KeyError as error:
        if self._descriptor_db:
          file_proto = self._descriptor_db.FindFileByName(file_name)
        else:
          raise error
      if not file_proto:
        raise KeyError('Cannot find a file named %s' % file_name)
      return self._ConvertFileProtoToFileDescriptor(file_proto)
  
    def FindFileContainingSymbol(self, symbol):
      """Gets the FileDescriptor for the file containing the specified symbol.
  
      Args:
        symbol: The name of the symbol to search for.
  
      Returns:
        A FileDescriptor that contains the specified symbol.
  
      Raises:
        KeyError: if the file can not be found in the pool.
      """
  
      symbol = _NormalizeFullyQualifiedName(symbol)
      try:
        return self._descriptors[symbol].file
      except KeyError:
        pass
  
      try:
        return self._enum_descriptors[symbol].file
      except KeyError:
        pass
  
      try:
        file_proto = self._internal_db.FindFileContainingSymbol(symbol)
      except KeyError as error:
        if self._descriptor_db:
          file_proto = self._descriptor_db.FindFileContainingSymbol(symbol)
        else:
          raise error
      if not file_proto:
        raise KeyError('Cannot find a file containing %s' % symbol)
      return self._ConvertFileProtoToFileDescriptor(file_proto)
  
    def FindMessageTypeByName(self, full_name):
      """Loads the named descriptor from the pool.
  
      Args:
        full_name: The full name of the descriptor to load.
  
      Returns:
        The descriptor for the named type.
      """
  
      full_name = _NormalizeFullyQualifiedName(full_name)
      if full_name not in self._descriptors:
        self.FindFileContainingSymbol(full_name)
      return self._descriptors[full_name]
  
    def FindEnumTypeByName(self, full_name):
      """Loads the named enum descriptor from the pool.
  
      Args:
        full_name: The full name of the enum descriptor to load.
  
      Returns:
        The enum descriptor for the named type.
      """
  
      full_name = _NormalizeFullyQualifiedName(full_name)
      if full_name not in self._enum_descriptors:
        self.FindFileContainingSymbol(full_name)
      return self._enum_descriptors[full_name]
  
    def FindFieldByName(self, full_name):
      """Loads the named field descriptor from the pool.
  
      Args:
        full_name: The full name of the field descriptor to load.
  
      Returns:
        The field descriptor for the named field.
      """
      full_name = _NormalizeFullyQualifiedName(full_name)
      message_name, _, field_name = full_name.rpartition('.')
      message_descriptor = self.FindMessageTypeByName(message_name)
      return message_descriptor.fields_by_name[field_name]
  
    def FindExtensionByName(self, full_name):
      """Loads the named extension descriptor from the pool.
  
      Args:
        full_name: The full name of the extension descriptor to load.
  
      Returns:
        A FieldDescriptor, describing the named extension.
      """
      full_name = _NormalizeFullyQualifiedName(full_name)
      try:
        # The proto compiler does not give any link between the FileDescriptor
        # and top-level extensions unless the FileDescriptorProto is added to
        # the DescriptorDatabase, but this can impact memory usage.
        # So we registered these extensions by name explicitly.
        return self._toplevel_extensions[full_name]
      except KeyError:
        pass
      message_name, _, extension_name = full_name.rpartition('.')
      try:
        # Most extensions are nested inside a message.
        scope = self.FindMessageTypeByName(message_name)
      except KeyError:
        # Some extensions are defined at file scope.
        scope = self.FindFileContainingSymbol(full_name)
      return scope.extensions_by_name[extension_name]
  
    def FindExtensionByNumber(self, message_descriptor, number):
      """Gets the extension of the specified message with the specified number.
  
      Extensions have to be registered to this pool by calling
      AddExtensionDescriptor.
  
      Args:
        message_descriptor: descriptor of the extended message.
        number: integer, number of the extension field.
  
      Returns:
        A FieldDescriptor describing the extension.
  
      Raise:
        KeyError: when no extension with the given number is known for the
          specified message.
      """
      return self._extensions_by_number[message_descriptor][number]
  
    def FindAllExtensions(self, message_descriptor):
      """Gets all the known extension of a given message.
  
      Extensions have to be registered to this pool by calling
      AddExtensionDescriptor.
  
      Args:
        message_descriptor: descriptor of the extended message.
  
      Returns:
        A list of FieldDescriptor describing the extensions.
      """
      return list(self._extensions_by_number[message_descriptor].values())
  
    def _ConvertFileProtoToFileDescriptor(self, file_proto):
      """Creates a FileDescriptor from a proto or returns a cached copy.
  
      This method also has the side effect of loading all the symbols found in
      the file into the appropriate dictionaries in the pool.
  
      Args:
        file_proto: The proto to convert.
  
      Returns:
        A FileDescriptor matching the passed in proto.
      """
  
      if file_proto.name not in self._file_descriptors:
        built_deps = list(self._GetDeps(file_proto.dependency))
        direct_deps = [self.FindFileByName(n) for n in file_proto.dependency]
        public_deps = [direct_deps[i] for i in file_proto.public_dependency]
  
        file_descriptor = descriptor.FileDescriptor(
            pool=self,
            name=file_proto.name,
            package=file_proto.package,
            syntax=file_proto.syntax,
            options=_OptionsOrNone(file_proto),
            serialized_pb=file_proto.SerializeToString(),
            dependencies=direct_deps,
            public_dependencies=public_deps)
        scope = {}
  
        # This loop extracts all the message and enum types from all the
        # dependencies of the file_proto. This is necessary to create the
        # scope of available message types when defining the passed in
        # file proto.
        for dependency in built_deps:
          scope.update(self._ExtractSymbols(
              dependency.message_types_by_name.values()))
          scope.update((_PrefixWithDot(enum.full_name), enum)
                       for enum in dependency.enum_types_by_name.values())
  
        for message_type in file_proto.message_type:
          message_desc = self._ConvertMessageDescriptor(
              message_type, file_proto.package, file_descriptor, scope,
              file_proto.syntax)
          file_descriptor.message_types_by_name[message_desc.name] = (
              message_desc)
  
        for enum_type in file_proto.enum_type:
          file_descriptor.enum_types_by_name[enum_type.name] = (
              self._ConvertEnumDescriptor(enum_type, file_proto.package,
                                          file_descriptor, None, scope))
  
        for index, extension_proto in enumerate(file_proto.extension):
          extension_desc = self._MakeFieldDescriptor(
              extension_proto, file_proto.package, index, is_extension=True)
          extension_desc.containing_type = self._GetTypeFromScope(
              file_descriptor.package, extension_proto.extendee, scope)
          self._SetFieldType(extension_proto, extension_desc,
                             file_descriptor.package, scope)
          file_descriptor.extensions_by_name[extension_desc.name] = (
              extension_desc)
  
        for desc_proto in file_proto.message_type:
          self._SetAllFieldTypes(file_proto.package, desc_proto, scope)
  
        if file_proto.package:
          desc_proto_prefix = _PrefixWithDot(file_proto.package)
        else:
          desc_proto_prefix = ''
  
        for desc_proto in file_proto.message_type:
          desc = self._GetTypeFromScope(
              desc_proto_prefix, desc_proto.name, scope)
          file_descriptor.message_types_by_name[desc_proto.name] = desc
  
        for index, service_proto in enumerate(file_proto.service):
          file_descriptor.services_by_name[service_proto.name] = (
              self._MakeServiceDescriptor(service_proto, index, scope,
                                          file_proto.package, file_descriptor))
  
        self.Add(file_proto)
        self._file_descriptors[file_proto.name] = file_descriptor
  
      return self._file_descriptors[file_proto.name]
  
    def _ConvertMessageDescriptor(self, desc_proto, package=None, file_desc=None,
                                  scope=None, syntax=None):
      """Adds the proto to the pool in the specified package.
  
      Args:
        desc_proto: The descriptor_pb2.DescriptorProto protobuf message.
        package: The package the proto should be located in.
        file_desc: The file containing this message.
        scope: Dict mapping short and full symbols to message and enum types.
        syntax: string indicating syntax of the file ("proto2" or "proto3")
  
      Returns:
        The added descriptor.
      """
  
      if package:
        desc_name = '.'.join((package, desc_proto.name))
      else:
        desc_name = desc_proto.name
  
      if file_desc is None:
        file_name = None
      else:
        file_name = file_desc.name
  
      if scope is None:
        scope = {}
  
      nested = [
          self._ConvertMessageDescriptor(
              nested, desc_name, file_desc, scope, syntax)
          for nested in desc_proto.nested_type]
      enums = [
          self._ConvertEnumDescriptor(enum, desc_name, file_desc, None, scope)
          for enum in desc_proto.enum_type]
      fields = [self._MakeFieldDescriptor(field, desc_name, index)
                for index, field in enumerate(desc_proto.field)]
      extensions = [
          self._MakeFieldDescriptor(extension, desc_name, index,
                                    is_extension=True)
          for index, extension in enumerate(desc_proto.extension)]
      oneofs = [
          descriptor.OneofDescriptor(desc.name, '.'.join((desc_name, desc.name)),
                                     index, None, [], desc.options)
          for index, desc in enumerate(desc_proto.oneof_decl)]
      extension_ranges = [(r.start, r.end) for r in desc_proto.extension_range]
      if extension_ranges:
        is_extendable = True
      else:
        is_extendable = False
      desc = descriptor.Descriptor(
          name=desc_proto.name,
          full_name=desc_name,
          filename=file_name,
          containing_type=None,
          fields=fields,
          oneofs=oneofs,
          nested_types=nested,
          enum_types=enums,
          extensions=extensions,
          options=_OptionsOrNone(desc_proto),
          is_extendable=is_extendable,
          extension_ranges=extension_ranges,
          file=file_desc,
          serialized_start=None,
          serialized_end=None,
          syntax=syntax)
      for nested in desc.nested_types:
        nested.containing_type = desc
      for enum in desc.enum_types:
        enum.containing_type = desc
      for field_index, field_desc in enumerate(desc_proto.field):
        if field_desc.HasField('oneof_index'):
          oneof_index = field_desc.oneof_index
          oneofs[oneof_index].fields.append(fields[field_index])
          fields[field_index].containing_oneof = oneofs[oneof_index]
  
      scope[_PrefixWithDot(desc_name)] = desc
      self._descriptors[desc_name] = desc
      return desc
  
    def _ConvertEnumDescriptor(self, enum_proto, package=None, file_desc=None,
                               containing_type=None, scope=None):
      """Make a protobuf EnumDescriptor given an EnumDescriptorProto protobuf.
  
      Args:
        enum_proto: The descriptor_pb2.EnumDescriptorProto protobuf message.
        package: Optional package name for the new message EnumDescriptor.
        file_desc: The file containing the enum descriptor.
        containing_type: The type containing this enum.
        scope: Scope containing available types.
  
      Returns:
        The added descriptor
      """
  
      if package:
        enum_name = '.'.join((package, enum_proto.name))
      else:
        enum_name = enum_proto.name
  
      if file_desc is None:
        file_name = None
      else:
        file_name = file_desc.name
  
      values = [self._MakeEnumValueDescriptor(value, index)
                for index, value in enumerate(enum_proto.value)]
      desc = descriptor.EnumDescriptor(name=enum_proto.name,
                                       full_name=enum_name,
                                       filename=file_name,
                                       file=file_desc,
                                       values=values,
                                       containing_type=containing_type,
                                       options=_OptionsOrNone(enum_proto))
      scope['.%s' % enum_name] = desc
      self._enum_descriptors[enum_name] = desc
      return desc
  
    def _MakeFieldDescriptor(self, field_proto, message_name, index,
                             is_extension=False):
      """Creates a field descriptor from a FieldDescriptorProto.
  
      For message and enum type fields, this method will do a look up
      in the pool for the appropriate descriptor for that type. If it
      is unavailable, it will fall back to the _source function to
      create it. If this type is still unavailable, construction will
      fail.
  
      Args:
        field_proto: The proto describing the field.
        message_name: The name of the containing message.
        index: Index of the field
        is_extension: Indication that this field is for an extension.
  
      Returns:
        An initialized FieldDescriptor object
      """
  
      if message_name:
        full_name = '.'.join((message_name, field_proto.name))
      else:
        full_name = field_proto.name
  
      return descriptor.FieldDescriptor(
          name=field_proto.name,
          full_name=full_name,
          index=index,
          number=field_proto.number,
          type=field_proto.type,
          cpp_type=None,
          message_type=None,
          enum_type=None,
          containing_type=None,
          label=field_proto.label,
          has_default_value=False,
          default_value=None,
          is_extension=is_extension,
          extension_scope=None,
          options=_OptionsOrNone(field_proto))
  
    def _SetAllFieldTypes(self, package, desc_proto, scope):
      """Sets all the descriptor's fields's types.
  
      This method also sets the containing types on any extensions.
  
      Args:
        package: The current package of desc_proto.
        desc_proto: The message descriptor to update.
        scope: Enclosing scope of available types.
      """
  
      package = _PrefixWithDot(package)
  
      main_desc = self._GetTypeFromScope(package, desc_proto.name, scope)
  
      if package == '.':
        nested_package = _PrefixWithDot(desc_proto.name)
      else:
        nested_package = '.'.join([package, desc_proto.name])
  
      for field_proto, field_desc in zip(desc_proto.field, main_desc.fields):
        self._SetFieldType(field_proto, field_desc, nested_package, scope)
  
      for extension_proto, extension_desc in (
          zip(desc_proto.extension, main_desc.extensions)):
        extension_desc.containing_type = self._GetTypeFromScope(
            nested_package, extension_proto.extendee, scope)
        self._SetFieldType(extension_proto, extension_desc, nested_package, scope)
  
      for nested_type in desc_proto.nested_type:
        self._SetAllFieldTypes(nested_package, nested_type, scope)
  
    def _SetFieldType(self, field_proto, field_desc, package, scope):
      """Sets the field's type, cpp_type, message_type and enum_type.
  
      Args:
        field_proto: Data about the field in proto format.
        field_desc: The descriptor to modiy.
        package: The package the field's container is in.
        scope: Enclosing scope of available types.
      """
      if field_proto.type_name:
        desc = self._GetTypeFromScope(package, field_proto.type_name, scope)
      else:
        desc = None
  
      if not field_proto.HasField('type'):
        if isinstance(desc, descriptor.Descriptor):
          field_proto.type = descriptor.FieldDescriptor.TYPE_MESSAGE
        else:
          field_proto.type = descriptor.FieldDescriptor.TYPE_ENUM
  
      field_desc.cpp_type = descriptor.FieldDescriptor.ProtoTypeToCppProtoType(
          field_proto.type)
  
      if (field_proto.type == descriptor.FieldDescriptor.TYPE_MESSAGE
          or field_proto.type == descriptor.FieldDescriptor.TYPE_GROUP):
        field_desc.message_type = desc
  
      if field_proto.type == descriptor.FieldDescriptor.TYPE_ENUM:
        field_desc.enum_type = desc
  
      if field_proto.label == descriptor.FieldDescriptor.LABEL_REPEATED:
        field_desc.has_default_value = False
        field_desc.default_value = []
      elif field_proto.HasField('default_value'):
        field_desc.has_default_value = True
        if (field_proto.type == descriptor.FieldDescriptor.TYPE_DOUBLE or
            field_proto.type == descriptor.FieldDescriptor.TYPE_FLOAT):
          field_desc.default_value = float(field_proto.default_value)
        elif field_proto.type == descriptor.FieldDescriptor.TYPE_STRING:
          field_desc.default_value = field_proto.default_value
        elif field_proto.type == descriptor.FieldDescriptor.TYPE_BOOL:
          field_desc.default_value = field_proto.default_value.lower() == 'true'
        elif field_proto.type == descriptor.FieldDescriptor.TYPE_ENUM:
          field_desc.default_value = field_desc.enum_type.values_by_name[
              field_proto.default_value].number
        elif field_proto.type == descriptor.FieldDescriptor.TYPE_BYTES:
          field_desc.default_value = text_encoding.CUnescape(
              field_proto.default_value)
        else:
          # All other types are of the "int" type.
          field_desc.default_value = int(field_proto.default_value)
      else:
        field_desc.has_default_value = False
        if (field_proto.type == descriptor.FieldDescriptor.TYPE_DOUBLE or
            field_proto.type == descriptor.FieldDescriptor.TYPE_FLOAT):
          field_desc.default_value = 0.0
        elif field_proto.type == descriptor.FieldDescriptor.TYPE_STRING:
          field_desc.default_value = u''
        elif field_proto.type == descriptor.FieldDescriptor.TYPE_BOOL:
          field_desc.default_value = False
        elif field_proto.type == descriptor.FieldDescriptor.TYPE_ENUM:
          field_desc.default_value = field_desc.enum_type.values[0].number
        elif field_proto.type == descriptor.FieldDescriptor.TYPE_BYTES:
          field_desc.default_value = b''
        else:
          # All other types are of the "int" type.
          field_desc.default_value = 0
  
      field_desc.type = field_proto.type
  
    def _MakeEnumValueDescriptor(self, value_proto, index):
      """Creates a enum value descriptor object from a enum value proto.
  
      Args:
        value_proto: The proto describing the enum value.
        index: The index of the enum value.
  
      Returns:
        An initialized EnumValueDescriptor object.
      """
  
      return descriptor.EnumValueDescriptor(
          name=value_proto.name,
          index=index,
          number=value_proto.number,
          options=_OptionsOrNone(value_proto),
          type=None)
  
    def _MakeServiceDescriptor(self, service_proto, service_index, scope,
                               package, file_desc):
      """Make a protobuf ServiceDescriptor given a ServiceDescriptorProto.
  
      Args:
        service_proto: The descriptor_pb2.ServiceDescriptorProto protobuf message.
        service_index: The index of the service in the File.
        scope: Dict mapping short and full symbols to message and enum types.
        package: Optional package name for the new message EnumDescriptor.
        file_desc: The file containing the service descriptor.
  
      Returns:
        The added descriptor.
      """
  
      if package:
        service_name = '.'.join((package, service_proto.name))
      else:
        service_name = service_proto.name
  
      methods = [self._MakeMethodDescriptor(method_proto, service_name, package,
                                            scope, index)
                 for index, method_proto in enumerate(service_proto.method)]
      desc = descriptor.ServiceDescriptor(name=service_proto.name,
                                          full_name=service_name,
                                          index=service_index,
                                          methods=methods,
                                          options=_OptionsOrNone(service_proto),
                                          file=file_desc)
      return desc
  
    def _MakeMethodDescriptor(self, method_proto, service_name, package, scope,
                              index):
      """Creates a method descriptor from a MethodDescriptorProto.
  
      Args:
        method_proto: The proto describing the method.
        service_name: The name of the containing service.
        package: Optional package name to look up for types.
        scope: Scope containing available types.
        index: Index of the method in the service.
  
      Returns:
        An initialized MethodDescriptor object.
      """
      full_name = '.'.join((service_name, method_proto.name))
      input_type = self._GetTypeFromScope(
          package, method_proto.input_type, scope)
      output_type = self._GetTypeFromScope(
          package, method_proto.output_type, scope)
      return descriptor.MethodDescriptor(name=method_proto.name,
                                         full_name=full_name,
                                         index=index,
                                         containing_service=None,
                                         input_type=input_type,
                                         output_type=output_type,
                                         options=_OptionsOrNone(method_proto))
  
    def _ExtractSymbols(self, descriptors):
      """Pulls out all the symbols from descriptor protos.
  
      Args:
        descriptors: The messages to extract descriptors from.
      Yields:
        A two element tuple of the type name and descriptor object.
      """
  
      for desc in descriptors:
        yield (_PrefixWithDot(desc.full_name), desc)
        for symbol in self._ExtractSymbols(desc.nested_types):
          yield symbol
        for enum in desc.enum_types:
          yield (_PrefixWithDot(enum.full_name), enum)
  
    def _GetDeps(self, dependencies):
      """Recursively finds dependencies for file protos.
  
      Args:
        dependencies: The names of the files being depended on.
  
      Yields:
        Each direct and indirect dependency.
      """
  
      for dependency in dependencies:
        dep_desc = self.FindFileByName(dependency)
        yield dep_desc
        for parent_dep in dep_desc.dependencies:
          yield parent_dep
  
    def _GetTypeFromScope(self, package, type_name, scope):
      """Finds a given type name in the current scope.
  
      Args:
        package: The package the proto should be located in.
        type_name: The name of the type to be found in the scope.
        scope: Dict mapping short and full symbols to message and enum types.
  
      Returns:
        The descriptor for the requested type.
      """
      if type_name not in scope:
        components = _PrefixWithDot(package).split('.')
        while components:
          possible_match = '.'.join(components + [type_name])
          if possible_match in scope:
            type_name = possible_match
            break
          else:
            components.pop(-1)
      return scope[type_name]
  
  
  def _PrefixWithDot(name):
    return name if name.startswith('.') else '.%s' % name
  
  
  if _USE_C_DESCRIPTORS:
    # TODO(user): This pool could be constructed from Python code, when we
    # support a flag like 'use_cpp_generated_pool=True'.
    # pylint: disable=protected-access
    _DEFAULT = descriptor._message.default_pool
  else:
    _DEFAULT = DescriptorPool()
  
  
  def Default():
    return _DEFAULT
  