1# Protocol Buffers - Google's data interchange format
2# Copyright 2008 Google Inc. All rights reserved.
3#
4# Use of this source code is governed by a BSD-style
5# license that can be found in the LICENSE file or at
6# https://developers.google.com/open-source/licenses/bsd
7
8# This code is meant to work on Python 2.4 and above only.
9
10"""Contains a metaclass and helper functions used to create
11protocol message classes from Descriptor objects at runtime.
12
13Recall that a metaclass is the "type" of a class.
14(A class is to a metaclass what an instance is to a class.)
15
16In this case, we use the GeneratedProtocolMessageType metaclass
17to inject all the useful functionality into the classes
18output by the protocol compiler at compile-time.
19
20The upshot of all this is that the real implementation
21details for ALL pure-Python protocol buffers are *here in
22this file*.
23"""
24
25__author__ = 'robinson@google.com (Will Robinson)'
26
27
28from google.protobuf import message_factory
29from google.protobuf import symbol_database
30
31# The type of all Message classes.
32# Part of the public interface, but normally only used by message factories.
33GeneratedProtocolMessageType = message_factory._GENERATED_PROTOCOL_MESSAGE_TYPE
34
35MESSAGE_CLASS_CACHE = {}
36
37
38# Deprecated. Please NEVER use reflection.ParseMessage().
39def ParseMessage(descriptor, byte_str):
40 """Generate a new Message instance from this Descriptor and a byte string.
41
42 DEPRECATED: ParseMessage is deprecated because it is using MakeClass().
43 Please use MessageFactory.GetPrototype() instead.
44
45 Args:
46 descriptor: Protobuf Descriptor object
47 byte_str: Serialized protocol buffer byte string
48
49 Returns:
50 Newly created protobuf Message object.
51 """
52 result_class = MakeClass(descriptor)
53 new_msg = result_class()
54 new_msg.ParseFromString(byte_str)
55 return new_msg
56
57
58# Deprecated. Please NEVER use reflection.MakeClass().
59def MakeClass(descriptor):
60 """Construct a class object for a protobuf described by descriptor.
61
62 DEPRECATED: use MessageFactory.GetPrototype() instead.
63
64 Args:
65 descriptor: A descriptor.Descriptor object describing the protobuf.
66 Returns:
67 The Message class object described by the descriptor.
68 """
69 # Original implementation leads to duplicate message classes, which won't play
70 # well with extensions. Message factory info is also missing.
71 # Redirect to message_factory.
72 return message_factory.GetMessageClass(descriptor)