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1# Protocol Buffers - Google's data interchange format
2# Copyright 2008 Google Inc.  All rights reserved.
3# https://developers.google.com/protocol-buffers/
4#
5# Redistribution and use in source and binary forms, with or without
6# modification, are permitted provided that the following conditions are
7# met:
8#
9#     * Redistributions of source code must retain the above copyright
10# notice, this list of conditions and the following disclaimer.
11#     * Redistributions in binary form must reproduce the above
12# copyright notice, this list of conditions and the following disclaimer
13# in the documentation and/or other materials provided with the
14# distribution.
15#     * Neither the name of Google Inc. nor the names of its
16# contributors may be used to endorse or promote products derived from
17# this software without specific prior written permission.
18#
19# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30
31"""Provides a factory class for generating dynamic messages.
32
33The easiest way to use this class is if you have access to the FileDescriptor
34protos containing the messages you want to create you can just do the following:
35
36message_classes = message_factory.GetMessages(iterable_of_file_descriptors)
37my_proto_instance = message_classes['some.proto.package.MessageName']()
38"""
39
40__author__ = 'matthewtoia@google.com (Matt Toia)'
41
42from google.protobuf.internal import api_implementation
43from google.protobuf import descriptor_pool
44from google.protobuf import message
45
46if api_implementation.Type() == 'cpp':
47  from google.protobuf.pyext import cpp_message as message_impl
48else:
49  from google.protobuf.internal import python_message as message_impl
50
51
52# The type of all Message classes.
53_GENERATED_PROTOCOL_MESSAGE_TYPE = message_impl.GeneratedProtocolMessageType
54
55
56class MessageFactory(object):
57  """Factory for creating Proto2 messages from descriptors in a pool."""
58
59  def __init__(self, pool=None):
60    """Initializes a new factory."""
61    self.pool = pool or descriptor_pool.DescriptorPool()
62
63    # local cache of all classes built from protobuf descriptors
64    self._classes = {}
65
66  def GetPrototype(self, descriptor):
67    """Builds a proto2 message class based on the passed in descriptor.
68
69    Passing a descriptor with a fully qualified name matching a previous
70    invocation will cause the same class to be returned.
71
72    Args:
73      descriptor: The descriptor to build from.
74
75    Returns:
76      A class describing the passed in descriptor.
77    """
78    if descriptor not in self._classes:
79      descriptor_name = descriptor.name
80      if str is bytes:  # PY2
81        descriptor_name = descriptor.name.encode('ascii', 'ignore')
82      result_class = _GENERATED_PROTOCOL_MESSAGE_TYPE(
83          descriptor_name,
84          (message.Message,),
85          {'DESCRIPTOR': descriptor, '__module__': None})
86      # pylint: disable=protected-access
87      result_class._FACTORY = self
88      # If module not set, it wrongly points to message_factory module.
89      self._classes[descriptor] = result_class
90      for field in descriptor.fields:
91        if field.message_type:
92          self.GetPrototype(field.message_type)
93      for extension in result_class.DESCRIPTOR.extensions:
94        if extension.containing_type not in self._classes:
95          self.GetPrototype(extension.containing_type)
96        extended_class = self._classes[extension.containing_type]
97        extended_class.RegisterExtension(extension)
98    return self._classes[descriptor]
99
100  def GetMessages(self, files):
101    """Gets all the messages from a specified file.
102
103    This will find and resolve dependencies, failing if the descriptor
104    pool cannot satisfy them.
105
106    Args:
107      files: The file names to extract messages from.
108
109    Returns:
110      A dictionary mapping proto names to the message classes. This will include
111      any dependent messages as well as any messages defined in the same file as
112      a specified message.
113    """
114    result = {}
115    for file_name in files:
116      file_desc = self.pool.FindFileByName(file_name)
117      for desc in file_desc.message_types_by_name.values():
118        result[desc.full_name] = self.GetPrototype(desc)
119
120      # While the extension FieldDescriptors are created by the descriptor pool,
121      # the python classes created in the factory need them to be registered
122      # explicitly, which is done below.
123      #
124      # The call to RegisterExtension will specifically check if the
125      # extension was already registered on the object and either
126      # ignore the registration if the original was the same, or raise
127      # an error if they were different.
128
129      for extension in file_desc.extensions_by_name.values():
130        if extension.containing_type not in self._classes:
131          self.GetPrototype(extension.containing_type)
132        extended_class = self._classes[extension.containing_type]
133        extended_class.RegisterExtension(extension)
134    return result
135
136
137_FACTORY = MessageFactory()
138
139
140def GetMessages(file_protos):
141  """Builds a dictionary of all the messages available in a set of files.
142
143  Args:
144    file_protos: Iterable of FileDescriptorProto to build messages out of.
145
146  Returns:
147    A dictionary mapping proto names to the message classes. This will include
148    any dependent messages as well as any messages defined in the same file as
149    a specified message.
150  """
151  # The cpp implementation of the protocol buffer library requires to add the
152  # message in topological order of the dependency graph.
153  file_by_name = {file_proto.name: file_proto for file_proto in file_protos}
154  def _AddFile(file_proto):
155    for dependency in file_proto.dependency:
156      if dependency in file_by_name:
157        # Remove from elements to be visited, in order to cut cycles.
158        _AddFile(file_by_name.pop(dependency))
159    _FACTORY.pool.Add(file_proto)
160  while file_by_name:
161    _AddFile(file_by_name.popitem()[1])
162  return _FACTORY.GetMessages([file_proto.name for file_proto in file_protos])
163