122 lines
4.5 KiB
Python
122 lines
4.5 KiB
Python
# 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.
|
|
|
|
# This code is meant to work on Python 2.4 and above only.
|
|
|
|
"""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)'
|
|
|
|
|
|
from google.protobuf.internal import api_implementation
|
|
from google.protobuf import message
|
|
|
|
|
|
if api_implementation.Type() == 'cpp':
|
|
from google.protobuf.pyext import cpp_message as message_impl
|
|
else:
|
|
from google.protobuf.internal import python_message as message_impl
|
|
|
|
# The type of all Message classes.
|
|
# Part of the public interface, but normally only used by message factories.
|
|
GeneratedProtocolMessageType = message_impl.GeneratedProtocolMessageType
|
|
|
|
MESSAGE_CLASS_CACHE = {}
|
|
|
|
|
|
def ParseMessage(descriptor, byte_str):
|
|
"""Generate a new Message instance from this Descriptor and a byte string.
|
|
|
|
Args:
|
|
descriptor: Protobuf Descriptor object
|
|
byte_str: Serialized protocol buffer byte string
|
|
|
|
Returns:
|
|
Newly created protobuf Message object.
|
|
"""
|
|
result_class = MakeClass(descriptor)
|
|
new_msg = result_class()
|
|
new_msg.ParseFromString(byte_str)
|
|
return new_msg
|
|
|
|
|
|
def MakeClass(descriptor):
|
|
"""Construct a class object for a protobuf described by descriptor.
|
|
|
|
Composite descriptors are handled by defining the new class as a member of the
|
|
parent class, recursing as deep as necessary.
|
|
This is the dynamic equivalent to:
|
|
|
|
class Parent(message.Message):
|
|
__metaclass__ = GeneratedProtocolMessageType
|
|
DESCRIPTOR = descriptor
|
|
class Child(message.Message):
|
|
__metaclass__ = GeneratedProtocolMessageType
|
|
DESCRIPTOR = descriptor.nested_types[0]
|
|
|
|
Sample usage:
|
|
file_descriptor = descriptor_pb2.FileDescriptorProto()
|
|
file_descriptor.ParseFromString(proto2_string)
|
|
msg_descriptor = descriptor.MakeDescriptor(file_descriptor.message_type[0])
|
|
msg_class = reflection.MakeClass(msg_descriptor)
|
|
msg = msg_class()
|
|
|
|
Args:
|
|
descriptor: A descriptor.Descriptor object describing the protobuf.
|
|
Returns:
|
|
The Message class object described by the descriptor.
|
|
"""
|
|
if descriptor in MESSAGE_CLASS_CACHE:
|
|
return MESSAGE_CLASS_CACHE[descriptor]
|
|
|
|
attributes = {}
|
|
for name, nested_type in list(descriptor.nested_types_by_name.items()):
|
|
attributes[name] = MakeClass(nested_type)
|
|
|
|
attributes[GeneratedProtocolMessageType._DESCRIPTOR_KEY] = descriptor
|
|
|
|
result = GeneratedProtocolMessageType(
|
|
str(descriptor.name), (message.Message,), attributes)
|
|
MESSAGE_CLASS_CACHE[descriptor] = result
|
|
return result
|