Recipe package system.

recipe_engine/third_party/google/protobuf/descriptor.py

Index: recipe_engine/third_party/google/protobuf/descriptor.py
diff --git a/recipe_engine/third_party/google/protobuf/descriptor.py b/recipe_engine/third_party/google/protobuf/descriptor.py
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+# 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.
+
+"""Descriptors essentially contain exactly the information found in a .proto
+file, in types that make this information accessible in Python.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+
+from google.protobuf.internal import api_implementation
+
+
+if api_implementation.Type() == 'cpp':
+  if api_implementation.Version() == 2:
+    from google.protobuf.internal.cpp import _message
+  else:
+    from google.protobuf.internal import cpp_message
+
+
+class Error(Exception):
+  """Base error for this module."""
+
+
+class TypeTransformationError(Error):
+  """Error transforming between python proto type and corresponding C++ type."""
+
+
+class DescriptorBase(object):
+
+  """Descriptors base class.
+
+  This class is the base of all descriptor classes. It provides common options
+  related functionaility.
+
+  Attributes:
+    has_options:  True if the descriptor has non-default options.  Usually it
+        is not necessary to read this -- just call GetOptions() which will
+        happily return the default instance.  However, it's sometimes useful
+        for efficiency, and also useful inside the protobuf implementation to
+        avoid some bootstrapping issues.
+  """
+
+  def __init__(self, options, options_class_name):
+    """Initialize the descriptor given its options message and the name of the
+    class of the options message. The name of the class is required in case
+    the options message is None and has to be created.
+    """
+    self._options = options
+    self._options_class_name = options_class_name
+
+    # Does this descriptor have non-default options?
+    self.has_options = options is not None
+
+  def _SetOptions(self, options, options_class_name):
+    """Sets the descriptor's options
+
+    This function is used in generated proto2 files to update descriptor
+    options. It must not be used outside proto2.
+    """
+    self._options = options
+    self._options_class_name = options_class_name
+
+    # Does this descriptor have non-default options?
+    self.has_options = options is not None
+
+  def GetOptions(self):
+    """Retrieves descriptor options.
+
+    This method returns the options set or creates the default options for the
+    descriptor.
+    """
+    if self._options:
+      return self._options
+    from google.protobuf import descriptor_pb2
+    try:
+      options_class = getattr(descriptor_pb2, self._options_class_name)
+    except AttributeError:
+      raise RuntimeError('Unknown options class name %s!' %
+                         (self._options_class_name))
+    self._options = options_class()
+    return self._options
+
+
+class _NestedDescriptorBase(DescriptorBase):
+  """Common class for descriptors that can be nested."""
+
+  def __init__(self, options, options_class_name, name, full_name,
+               file, containing_type, serialized_start=None,
+               serialized_end=None):
+    """Constructor.
+
+    Args:
+      options: Protocol message options or None
+        to use default message options.
+      options_class_name: (str) The class name of the above options.
+
+      name: (str) Name of this protocol message type.
+      full_name: (str) Fully-qualified name of this protocol message type,
+        which will include protocol "package" name and the name of any
+        enclosing types.
+      file: (FileDescriptor) Reference to file info.
+      containing_type: if provided, this is a nested descriptor, with this
+        descriptor as parent, otherwise None.
+      serialized_start: The start index (inclusive) in block in the
+        file.serialized_pb that describes this descriptor.
+      serialized_end: The end index (exclusive) in block in the
+        file.serialized_pb that describes this descriptor.
+    """
+    super(_NestedDescriptorBase, self).__init__(
+        options, options_class_name)
+
+    self.name = name
+    # TODO(falk): Add function to calculate full_name instead of having it in
+    #             memory?
+    self.full_name = full_name
+    self.file = file
+    self.containing_type = containing_type
+
+    self._serialized_start = serialized_start
+    self._serialized_end = serialized_end
+
+  def GetTopLevelContainingType(self):
+    """Returns the root if this is a nested type, or itself if its the root."""
+    desc = self
+    while desc.containing_type is not None:
+      desc = desc.containing_type
+    return desc
+
+  def CopyToProto(self, proto):
+    """Copies this to the matching proto in descriptor_pb2.
+
+    Args:
+      proto: An empty proto instance from descriptor_pb2.
+
+    Raises:
+      Error: If self couldnt be serialized, due to to few constructor arguments.
+    """
+    if (self.file is not None and
+        self._serialized_start is not None and
+        self._serialized_end is not None):
+      proto.ParseFromString(self.file.serialized_pb[
+          self._serialized_start:self._serialized_end])
+    else:
+      raise Error('Descriptor does not contain serialization.')
+
+
+class Descriptor(_NestedDescriptorBase):
+
+  """Descriptor for a protocol message type.
+
+  A Descriptor instance has the following attributes:
+
+    name: (str) Name of this protocol message type.
+    full_name: (str) Fully-qualified name of this protocol message type,
+      which will include protocol "package" name and the name of any
+      enclosing types.
+
+    containing_type: (Descriptor) Reference to the descriptor of the
+      type containing us, or None if this is top-level.
+
+    fields: (list of FieldDescriptors) Field descriptors for all
+      fields in this type.
+    fields_by_number: (dict int -> FieldDescriptor) Same FieldDescriptor
+      objects as in |fields|, but indexed by "number" attribute in each
+      FieldDescriptor.
+    fields_by_name: (dict str -> FieldDescriptor) Same FieldDescriptor
+      objects as in |fields|, but indexed by "name" attribute in each
+      FieldDescriptor.
+
+    nested_types: (list of Descriptors) Descriptor references
+      for all protocol message types nested within this one.
+    nested_types_by_name: (dict str -> Descriptor) Same Descriptor
+      objects as in |nested_types|, but indexed by "name" attribute
+      in each Descriptor.
+
+    enum_types: (list of EnumDescriptors) EnumDescriptor references
+      for all enums contained within this type.
+    enum_types_by_name: (dict str ->EnumDescriptor) Same EnumDescriptor
+      objects as in |enum_types|, but indexed by "name" attribute
+      in each EnumDescriptor.
+    enum_values_by_name: (dict str -> EnumValueDescriptor) Dict mapping
+      from enum value name to EnumValueDescriptor for that value.
+
+    extensions: (list of FieldDescriptor) All extensions defined directly
+      within this message type (NOT within a nested type).
+    extensions_by_name: (dict, string -> FieldDescriptor) Same FieldDescriptor
+      objects as |extensions|, but indexed by "name" attribute of each
+      FieldDescriptor.
+
+    is_extendable:  Does this type define any extension ranges?
+
+    options: (descriptor_pb2.MessageOptions) Protocol message options or None
+      to use default message options.
+
+    file: (FileDescriptor) Reference to file descriptor.
+  """
+
+  def __init__(self, name, full_name, filename, containing_type, fields,
+               nested_types, enum_types, extensions, options=None,
+               is_extendable=True, extension_ranges=None, file=None,
+               serialized_start=None, serialized_end=None):
+    """Arguments to __init__() are as described in the description
+    of Descriptor fields above.
+
+    Note that filename is an obsolete argument, that is not used anymore.
+    Please use file.name to access this as an attribute.
+    """
+    super(Descriptor, self).__init__(
+        options, 'MessageOptions', name, full_name, file,
+        containing_type, serialized_start=serialized_start,
+        serialized_end=serialized_start)
+
+    # We have fields in addition to fields_by_name and fields_by_number,
+    # so that:
+    #   1. Clients can index fields by "order in which they're listed."
+    #   2. Clients can easily iterate over all fields with the terse
+    #      syntax: for f in descriptor.fields: ...
+    self.fields = fields
+    for field in self.fields:
+      field.containing_type = self
+    self.fields_by_number = dict((f.number, f) for f in fields)
+    self.fields_by_name = dict((f.name, f) for f in fields)
+
+    self.nested_types = nested_types
+    self.nested_types_by_name = dict((t.name, t) for t in nested_types)
+
+    self.enum_types = enum_types
+    for enum_type in self.enum_types:
+      enum_type.containing_type = self
+    self.enum_types_by_name = dict((t.name, t) for t in enum_types)
+    self.enum_values_by_name = dict(
+        (v.name, v) for t in enum_types for v in t.values)
+
+    self.extensions = extensions
+    for extension in self.extensions:
+      extension.extension_scope = self
+    self.extensions_by_name = dict((f.name, f) for f in extensions)
+    self.is_extendable = is_extendable
+    self.extension_ranges = extension_ranges
+
+    self._serialized_start = serialized_start
+    self._serialized_end = serialized_end
+
+  def EnumValueName(self, enum, value):
+    """Returns the string name of an enum value.
+
+    This is just a small helper method to simplify a common operation.
+
+    Args:
+      enum: string name of the Enum.
+      value: int, value of the enum.
+
+    Returns:
+      string name of the enum value.
+
+    Raises:
+      KeyError if either the Enum doesn't exist or the value is not a valid
+        value for the enum.
+    """
+    return self.enum_types_by_name[enum].values_by_number[value].name
+
+  def CopyToProto(self, proto):
+    """Copies this to a descriptor_pb2.DescriptorProto.
+
+    Args:
+      proto: An empty descriptor_pb2.DescriptorProto.
+    """
+    # This function is overriden to give a better doc comment.
+    super(Descriptor, self).CopyToProto(proto)
+
+
+# TODO(robinson): We should have aggressive checking here,
+# for example:
+#   * If you specify a repeated field, you should not be allowed
+#     to specify a default value.
+#   * [Other examples here as needed].
+#
+# TODO(robinson): for this and other *Descriptor classes, we
+# might also want to lock things down aggressively (e.g.,
+# prevent clients from setting the attributes).  Having
+# stronger invariants here in general will reduce the number
+# of runtime checks we must do in reflection.py...
+class FieldDescriptor(DescriptorBase):
+
+  """Descriptor for a single field in a .proto file.
+
+  A FieldDescriptor instance has the following attributes:
+
+    name: (str) Name of this field, exactly as it appears in .proto.
+    full_name: (str) Name of this field, including containing scope.  This is
+      particularly relevant for extensions.
+    index: (int) Dense, 0-indexed index giving the order that this
+      field textually appears within its message in the .proto file.
+    number: (int) Tag number declared for this field in the .proto file.
+
+    type: (One of the TYPE_* constants below) Declared type.
+    cpp_type: (One of the CPPTYPE_* constants below) C++ type used to
+      represent this field.
+
+    label: (One of the LABEL_* constants below) Tells whether this
+      field is optional, required, or repeated.
+    has_default_value: (bool) True if this field has a default value defined,
+      otherwise false.
+    default_value: (Varies) Default value of this field.  Only
+      meaningful for non-repeated scalar fields.  Repeated fields
+      should always set this to [], and non-repeated composite
+      fields should always set this to None.
+
+    containing_type: (Descriptor) Descriptor of the protocol message
+      type that contains this field.  Set by the Descriptor constructor
+      if we're passed into one.
+      Somewhat confusingly, for extension fields, this is the
+      descriptor of the EXTENDED message, not the descriptor
+      of the message containing this field.  (See is_extension and
+      extension_scope below).
+    message_type: (Descriptor) If a composite field, a descriptor
+      of the message type contained in this field.  Otherwise, this is None.
+    enum_type: (EnumDescriptor) If this field contains an enum, a
+      descriptor of that enum.  Otherwise, this is None.
+
+    is_extension: True iff this describes an extension field.
+    extension_scope: (Descriptor) Only meaningful if is_extension is True.
+      Gives the message that immediately contains this extension field.
+      Will be None iff we're a top-level (file-level) extension field.
+
+    options: (descriptor_pb2.FieldOptions) Protocol message field options or
+      None to use default field options.
+  """
+
+  # Must be consistent with C++ FieldDescriptor::Type enum in
+  # descriptor.h.
+  #
+  # TODO(robinson): Find a way to eliminate this repetition.
+  TYPE_DOUBLE         = 1
+  TYPE_FLOAT          = 2
+  TYPE_INT64          = 3
+  TYPE_UINT64         = 4
+  TYPE_INT32          = 5
+  TYPE_FIXED64        = 6
+  TYPE_FIXED32        = 7
+  TYPE_BOOL           = 8
+  TYPE_STRING         = 9
+  TYPE_GROUP          = 10
+  TYPE_MESSAGE        = 11
+  TYPE_BYTES          = 12
+  TYPE_UINT32         = 13
+  TYPE_ENUM           = 14
+  TYPE_SFIXED32       = 15
+  TYPE_SFIXED64       = 16
+  TYPE_SINT32         = 17
+  TYPE_SINT64         = 18
+  MAX_TYPE            = 18
+
+  # Must be consistent with C++ FieldDescriptor::CppType enum in
+  # descriptor.h.
+  #
+  # TODO(robinson): Find a way to eliminate this repetition.
+  CPPTYPE_INT32       = 1
+  CPPTYPE_INT64       = 2
+  CPPTYPE_UINT32      = 3
+  CPPTYPE_UINT64      = 4
+  CPPTYPE_DOUBLE      = 5
+  CPPTYPE_FLOAT       = 6
+  CPPTYPE_BOOL        = 7
+  CPPTYPE_ENUM        = 8
+  CPPTYPE_STRING      = 9
+  CPPTYPE_MESSAGE     = 10
+  MAX_CPPTYPE         = 10
+
+  _PYTHON_TO_CPP_PROTO_TYPE_MAP = {
+      TYPE_DOUBLE: CPPTYPE_DOUBLE,
+      TYPE_FLOAT: CPPTYPE_FLOAT,
+      TYPE_ENUM: CPPTYPE_ENUM,
+      TYPE_INT64: CPPTYPE_INT64,
+      TYPE_SINT64: CPPTYPE_INT64,
+      TYPE_SFIXED64: CPPTYPE_INT64,
+      TYPE_UINT64: CPPTYPE_UINT64,
+      TYPE_FIXED64: CPPTYPE_UINT64,
+      TYPE_INT32: CPPTYPE_INT32,
+      TYPE_SFIXED32: CPPTYPE_INT32,
+      TYPE_SINT32: CPPTYPE_INT32,
+      TYPE_UINT32: CPPTYPE_UINT32,
+      TYPE_FIXED32: CPPTYPE_UINT32,
+      TYPE_BYTES: CPPTYPE_STRING,
+      TYPE_STRING: CPPTYPE_STRING,
+      TYPE_BOOL: CPPTYPE_BOOL,
+      TYPE_MESSAGE: CPPTYPE_MESSAGE,
+      TYPE_GROUP: CPPTYPE_MESSAGE
+      }
+
+  # Must be consistent with C++ FieldDescriptor::Label enum in
+  # descriptor.h.
+  #
+  # TODO(robinson): Find a way to eliminate this repetition.
+  LABEL_OPTIONAL      = 1
+  LABEL_REQUIRED      = 2
+  LABEL_REPEATED      = 3
+  MAX_LABEL           = 3
+
+  def __init__(self, name, full_name, index, number, type, cpp_type, label,
+               default_value, message_type, enum_type, containing_type,
+               is_extension, extension_scope, options=None,
+               has_default_value=True):
+    """The arguments are as described in the description of FieldDescriptor
+    attributes above.
+
+    Note that containing_type may be None, and may be set later if necessary
+    (to deal with circular references between message types, for example).
+    Likewise for extension_scope.
+    """
+    super(FieldDescriptor, self).__init__(options, 'FieldOptions')
+    self.name = name
+    self.full_name = full_name
+    self.index = index
+    self.number = number
+    self.type = type
+    self.cpp_type = cpp_type
+    self.label = label
+    self.has_default_value = has_default_value
+    self.default_value = default_value
+    self.containing_type = containing_type
+    self.message_type = message_type
+    self.enum_type = enum_type
+    self.is_extension = is_extension
+    self.extension_scope = extension_scope
+    if api_implementation.Type() == 'cpp':
+      if is_extension:
+        if api_implementation.Version() == 2:
+          self._cdescriptor = _message.GetExtensionDescriptor(full_name)
+        else:
+          self._cdescriptor = cpp_message.GetExtensionDescriptor(full_name)
+      else:
+        if api_implementation.Version() == 2:
+          self._cdescriptor = _message.GetFieldDescriptor(full_name)
+        else:
+          self._cdescriptor = cpp_message.GetFieldDescriptor(full_name)
+    else:
+      self._cdescriptor = None
+
+  @staticmethod
+  def ProtoTypeToCppProtoType(proto_type):
+    """Converts from a Python proto type to a C++ Proto Type.
+
+    The Python ProtocolBuffer classes specify both the 'Python' datatype and the
+    'C++' datatype - and they're not the same. This helper method should
+    translate from one to another.
+
+    Args:
+      proto_type: the Python proto type (descriptor.FieldDescriptor.TYPE_*)
+    Returns:
+      descriptor.FieldDescriptor.CPPTYPE_*, the C++ type.
+    Raises:
+      TypeTransformationError: when the Python proto type isn't known.
+    """
+    try:
+      return FieldDescriptor._PYTHON_TO_CPP_PROTO_TYPE_MAP[proto_type]
+    except KeyError:
+      raise TypeTransformationError('Unknown proto_type: %s' % proto_type)
+
+
+class EnumDescriptor(_NestedDescriptorBase):
+
+  """Descriptor for an enum defined in a .proto file.
+
+  An EnumDescriptor instance has the following attributes:
+
+    name: (str) Name of the enum type.
+    full_name: (str) Full name of the type, including package name
+      and any enclosing type(s).
+
+    values: (list of EnumValueDescriptors) List of the values
+      in this enum.
+    values_by_name: (dict str -> EnumValueDescriptor) Same as |values|,
+      but indexed by the "name" field of each EnumValueDescriptor.
+    values_by_number: (dict int -> EnumValueDescriptor) Same as |values|,
+      but indexed by the "number" field of each EnumValueDescriptor.
+    containing_type: (Descriptor) Descriptor of the immediate containing
+      type of this enum, or None if this is an enum defined at the
+      top level in a .proto file.  Set by Descriptor's constructor
+      if we're passed into one.
+    file: (FileDescriptor) Reference to file descriptor.
+    options: (descriptor_pb2.EnumOptions) Enum options message or
+      None to use default enum options.
+  """
+
+  def __init__(self, name, full_name, filename, values,
+               containing_type=None, options=None, file=None,
+               serialized_start=None, serialized_end=None):
+    """Arguments are as described in the attribute description above.
+
+    Note that filename is an obsolete argument, that is not used anymore.
+    Please use file.name to access this as an attribute.
+    """
+    super(EnumDescriptor, self).__init__(
+        options, 'EnumOptions', name, full_name, file,
+        containing_type, serialized_start=serialized_start,
+        serialized_end=serialized_start)
+
+    self.values = values
+    for value in self.values:
+      value.type = self
+    self.values_by_name = dict((v.name, v) for v in values)
+    self.values_by_number = dict((v.number, v) for v in values)
+
+    self._serialized_start = serialized_start
+    self._serialized_end = serialized_end
+
+  def CopyToProto(self, proto):
+    """Copies this to a descriptor_pb2.EnumDescriptorProto.
+
+    Args:
+      proto: An empty descriptor_pb2.EnumDescriptorProto.
+    """
+    # This function is overriden to give a better doc comment.
+    super(EnumDescriptor, self).CopyToProto(proto)
+
+
+class EnumValueDescriptor(DescriptorBase):
+
+  """Descriptor for a single value within an enum.
+
+    name: (str) Name of this value.
+    index: (int) Dense, 0-indexed index giving the order that this
+      value appears textually within its enum in the .proto file.
+    number: (int) Actual number assigned to this enum value.
+    type: (EnumDescriptor) EnumDescriptor to which this value
+      belongs.  Set by EnumDescriptor's constructor if we're
+      passed into one.
+    options: (descriptor_pb2.EnumValueOptions) Enum value options message or
+      None to use default enum value options options.
+  """
+
+  def __init__(self, name, index, number, type=None, options=None):
+    """Arguments are as described in the attribute description above."""
+    super(EnumValueDescriptor, self).__init__(options, 'EnumValueOptions')
+    self.name = name
+    self.index = index
+    self.number = number
+    self.type = type
+
+
+class ServiceDescriptor(_NestedDescriptorBase):
+
+  """Descriptor for a service.
+
+    name: (str) Name of the service.
+    full_name: (str) Full name of the service, including package name.
+    index: (int) 0-indexed index giving the order that this services
+      definition appears withing the .proto file.
+    methods: (list of MethodDescriptor) List of methods provided by this
+      service.
+    options: (descriptor_pb2.ServiceOptions) Service options message or
+      None to use default service options.
+    file: (FileDescriptor) Reference to file info.
+  """
+
+  def __init__(self, name, full_name, index, methods, options=None, file=None,
+               serialized_start=None, serialized_end=None):
+    super(ServiceDescriptor, self).__init__(
+        options, 'ServiceOptions', name, full_name, file,
+        None, serialized_start=serialized_start,
+        serialized_end=serialized_end)
+    self.index = index
+    self.methods = methods
+    # Set the containing service for each method in this service.
+    for method in self.methods:
+      method.containing_service = self
+
+  def FindMethodByName(self, name):
+    """Searches for the specified method, and returns its descriptor."""
+    for method in self.methods:
+      if name == method.name:
+        return method
+    return None
+
+  def CopyToProto(self, proto):
+    """Copies this to a descriptor_pb2.ServiceDescriptorProto.
+
+    Args:
+      proto: An empty descriptor_pb2.ServiceDescriptorProto.
+    """
+    # This function is overriden to give a better doc comment.
+    super(ServiceDescriptor, self).CopyToProto(proto)
+
+
+class MethodDescriptor(DescriptorBase):
+
+  """Descriptor for a method in a service.
+
+  name: (str) Name of the method within the service.
+  full_name: (str) Full name of method.
+  index: (int) 0-indexed index of the method inside the service.
+  containing_service: (ServiceDescriptor) The service that contains this
+    method.
+  input_type: The descriptor of the message that this method accepts.
+  output_type: The descriptor of the message that this method returns.
+  options: (descriptor_pb2.MethodOptions) Method options message or
+    None to use default method options.
+  """
+
+  def __init__(self, name, full_name, index, containing_service,
+               input_type, output_type, options=None):
+    """The arguments are as described in the description of MethodDescriptor
+    attributes above.
+
+    Note that containing_service may be None, and may be set later if necessary.
+    """
+    super(MethodDescriptor, self).__init__(options, 'MethodOptions')
+    self.name = name
+    self.full_name = full_name
+    self.index = index
+    self.containing_service = containing_service
+    self.input_type = input_type
+    self.output_type = output_type
+
+
+class FileDescriptor(DescriptorBase):
+  """Descriptor for a file. Mimics the descriptor_pb2.FileDescriptorProto.
+
+  name: name of file, relative to root of source tree.
+  package: name of the package
+  serialized_pb: (str) Byte string of serialized
+    descriptor_pb2.FileDescriptorProto.
+  """
+
+  def __init__(self, name, package, options=None, serialized_pb=None):
+    """Constructor."""
+    super(FileDescriptor, self).__init__(options, 'FileOptions')
+
+    self.message_types_by_name = {}
+    self.name = name
+    self.package = package
+    self.serialized_pb = serialized_pb
+    if (api_implementation.Type() == 'cpp' and
+        self.serialized_pb is not None):
+      if api_implementation.Version() == 2:
+        _message.BuildFile(self.serialized_pb)
+      else:
+        cpp_message.BuildFile(self.serialized_pb)
+
+  def CopyToProto(self, proto):
+    """Copies this to a descriptor_pb2.FileDescriptorProto.
+
+    Args:
+      proto: An empty descriptor_pb2.FileDescriptorProto.
+    """
+    proto.ParseFromString(self.serialized_pb)
+
+
+def _ParseOptions(message, string):
+  """Parses serialized options.
+
+  This helper function is used to parse serialized options in generated
+  proto2 files. It must not be used outside proto2.
+  """
+  message.ParseFromString(string)
+  return message
+
+
+def MakeDescriptor(desc_proto, package=''):
+  """Make a protobuf Descriptor given a DescriptorProto protobuf.
+
+  Args:
+    desc_proto: The descriptor_pb2.DescriptorProto protobuf message.
+    package: Optional package name for the new message Descriptor (string).
+
+  Returns:
+    A Descriptor for protobuf messages.
+  """
+  full_message_name = [desc_proto.name]
+  if package: full_message_name.insert(0, package)
+  fields = []
+  for field_proto in desc_proto.field:
+    full_name = '.'.join(full_message_name + [field_proto.name])
+    field = FieldDescriptor(
+        field_proto.name, full_name, field_proto.number - 1,
+        field_proto.number, field_proto.type,
+        FieldDescriptor.ProtoTypeToCppProtoType(field_proto.type),
+        field_proto.label, None, None, None, None, False, None,
+        has_default_value=False)
+    fields.append(field)
+
+  desc_name = '.'.join(full_message_name)
+  return Descriptor(desc_proto.name, desc_name, None, None, fields,
+                    [], [], [])