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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    """Obtains 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      result_class = self.CreatePrototype(descriptor)
80      # The assignment to _classes is redundant for the base implementation, but
81      # might avoid confusion in cases where CreatePrototype gets overridden and
82      # does not call the base implementation.
83      self._classes[descriptor] = result_class
84      return result_class
85    return self._classes[descriptor]
86
87  def CreatePrototype(self, descriptor):
88    """Builds a proto2 message class based on the passed in descriptor.
89
90    Don't call this function directly, it always creates a new class. Call
91    GetPrototype() instead. This method is meant to be overridden in subblasses
92    to perform additional operations on the newly constructed class.
93
94    Args:
95      descriptor: The descriptor to build from.
96
97    Returns:
98      A class describing the passed in descriptor.
99    """
100    descriptor_name = descriptor.name
101    result_class = _GENERATED_PROTOCOL_MESSAGE_TYPE(
102        descriptor_name,
103        (message.Message,),
104        {
105            'DESCRIPTOR': descriptor,
106            # If module not set, it wrongly points to message_factory module.
107            '__module__': None,
108        })
109    result_class._FACTORY = self  # pylint: disable=protected-access
110    # Assign in _classes before doing recursive calls to avoid infinite
111    # recursion.
112    self._classes[descriptor] = result_class
113    for field in descriptor.fields:
114      if field.message_type:
115        self.GetPrototype(field.message_type)
116    for extension in result_class.DESCRIPTOR.extensions:
117      if extension.containing_type not in self._classes:
118        self.GetPrototype(extension.containing_type)
119      extended_class = self._classes[extension.containing_type]
120      extended_class.RegisterExtension(extension)
121    return result_class
122
123  def GetMessages(self, files):
124    """Gets all the messages from a specified file.
125
126    This will find and resolve dependencies, failing if the descriptor
127    pool cannot satisfy them.
128
129    Args:
130      files: The file names to extract messages from.
131
132    Returns:
133      A dictionary mapping proto names to the message classes. This will include
134      any dependent messages as well as any messages defined in the same file as
135      a specified message.
136    """
137    result = {}
138    for file_name in files:
139      file_desc = self.pool.FindFileByName(file_name)
140      for desc in file_desc.message_types_by_name.values():
141        result[desc.full_name] = self.GetPrototype(desc)
142
143      # While the extension FieldDescriptors are created by the descriptor pool,
144      # the python classes created in the factory need them to be registered
145      # explicitly, which is done below.
146      #
147      # The call to RegisterExtension will specifically check if the
148      # extension was already registered on the object and either
149      # ignore the registration if the original was the same, or raise
150      # an error if they were different.
151
152      for extension in file_desc.extensions_by_name.values():
153        if extension.containing_type not in self._classes:
154          self.GetPrototype(extension.containing_type)
155        extended_class = self._classes[extension.containing_type]
156        extended_class.RegisterExtension(extension)
157    return result
158
159
160_FACTORY = MessageFactory()
161
162
163def GetMessages(file_protos):
164  """Builds a dictionary of all the messages available in a set of files.
165
166  Args:
167    file_protos: Iterable of FileDescriptorProto to build messages out of.
168
169  Returns:
170    A dictionary mapping proto names to the message classes. This will include
171    any dependent messages as well as any messages defined in the same file as
172    a specified message.
173  """
174  # The cpp implementation of the protocol buffer library requires to add the
175  # message in topological order of the dependency graph.
176  file_by_name = {file_proto.name: file_proto for file_proto in file_protos}
177  def _AddFile(file_proto):
178    for dependency in file_proto.dependency:
179      if dependency in file_by_name:
180        # Remove from elements to be visited, in order to cut cycles.
181        _AddFile(file_by_name.pop(dependency))
182    _FACTORY.pool.Add(file_proto)
183  while file_by_name:
184    _AddFile(file_by_name.popitem()[1])
185  return _FACTORY.GetMessages([file_proto.name for file_proto in file_protos])
186