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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
8"""Provides a factory class for generating dynamic messages.
10The easiest way to use this class is if you have access to the FileDescriptor
11protos containing the messages you want to create you can just do the following:
13message_classes = message_factory.GetMessages(iterable_of_file_descriptors)
14my_proto_instance = message_classes['some.proto.package.MessageName']()
15"""
17__author__ = 'matthewtoia@google.com (Matt Toia)'
19import warnings
21from google.protobuf import descriptor_pool
22from google.protobuf import message
23from google.protobuf.internal import api_implementation
25if api_implementation.Type() == 'python':
26 from google.protobuf.internal import python_message as message_impl
27else:
28 from google.protobuf.pyext import cpp_message as message_impl # pylint: disable=g-import-not-at-top
31# The type of all Message classes.
32_GENERATED_PROTOCOL_MESSAGE_TYPE = message_impl.GeneratedProtocolMessageType
35def GetMessageClass(descriptor):
36 """Obtains a proto2 message class based on the passed in descriptor.
38 Passing a descriptor with a fully qualified name matching a previous
39 invocation will cause the same class to be returned.
41 Args:
42 descriptor: The descriptor to build from.
44 Returns:
45 A class describing the passed in descriptor.
46 """
47 concrete_class = getattr(descriptor, '_concrete_class', None)
48 if concrete_class:
49 return concrete_class
50 return _InternalCreateMessageClass(descriptor)
53def GetMessageClassesForFiles(files, pool):
54 """Gets all the messages from specified files.
56 This will find and resolve dependencies, failing if the descriptor
57 pool cannot satisfy them.
59 Args:
60 files: The file names to extract messages from.
61 pool: The descriptor pool to find the files including the dependent files.
63 Returns:
64 A dictionary mapping proto names to the message classes.
65 """
66 result = {}
67 for file_name in files:
68 file_desc = pool.FindFileByName(file_name)
69 for desc in file_desc.message_types_by_name.values():
70 result[desc.full_name] = GetMessageClass(desc)
72 # While the extension FieldDescriptors are created by the descriptor pool,
73 # the python classes created in the factory need them to be registered
74 # explicitly, which is done below.
75 #
76 # The call to RegisterExtension will specifically check if the
77 # extension was already registered on the object and either
78 # ignore the registration if the original was the same, or raise
79 # an error if they were different.
81 for extension in file_desc.extensions_by_name.values():
82 _ = GetMessageClass(extension.containing_type)
83 if api_implementation.Type() != 'python':
84 # TODO: Remove this check here. Duplicate extension
85 # register check should be in descriptor_pool.
86 if extension is not pool.FindExtensionByNumber(
87 extension.containing_type, extension.number
88 ):
89 raise ValueError('Double registration of Extensions')
90 # Recursively load protos for extension field, in order to be able to
91 # fully represent the extension. This matches the behavior for regular
92 # fields too.
93 if extension.message_type:
94 GetMessageClass(extension.message_type)
95 return result
98def _InternalCreateMessageClass(descriptor):
99 """Builds a proto2 message class based on the passed in descriptor.
101 Args:
102 descriptor: The descriptor to build from.
104 Returns:
105 A class describing the passed in descriptor.
106 """
107 descriptor_name = descriptor.name
108 result_class = _GENERATED_PROTOCOL_MESSAGE_TYPE(
109 descriptor_name,
110 (message.Message,),
111 {
112 'DESCRIPTOR': descriptor,
113 # If module not set, it wrongly points to message_factory module.
114 '__module__': None,
115 },
116 )
117 for field in descriptor.fields:
118 if field.message_type:
119 GetMessageClass(field.message_type)
121 for extension in result_class.DESCRIPTOR.extensions:
122 extended_class = GetMessageClass(extension.containing_type)
123 if api_implementation.Type() != 'python':
124 # TODO: Remove this check here. Duplicate extension
125 # register check should be in descriptor_pool.
126 pool = extension.containing_type.file.pool
127 if extension is not pool.FindExtensionByNumber(
128 extension.containing_type, extension.number
129 ):
130 raise ValueError('Double registration of Extensions')
131 if extension.message_type:
132 GetMessageClass(extension.message_type)
133 return result_class
136# Deprecated. Please use GetMessageClass() or GetMessageClassesForFiles()
137# method above instead.
138class MessageFactory(object):
139 """Factory for creating Proto2 messages from descriptors in a pool."""
141 def __init__(self, pool=None):
142 """Initializes a new factory."""
143 self.pool = pool or descriptor_pool.DescriptorPool()
146def GetMessages(file_protos, pool=None):
147 """Builds a dictionary of all the messages available in a set of files.
149 Args:
150 file_protos: Iterable of FileDescriptorProto to build messages out of.
151 pool: The descriptor pool to add the file protos.
153 Returns:
154 A dictionary mapping proto names to the message classes. This will include
155 any dependent messages as well as any messages defined in the same file as
156 a specified message.
157 """
158 # The cpp implementation of the protocol buffer library requires to add the
159 # message in topological order of the dependency graph.
160 des_pool = pool or descriptor_pool.DescriptorPool()
161 file_by_name = {file_proto.name: file_proto for file_proto in file_protos}
163 def _AddFile(file_proto):
164 for dependency in file_proto.dependency:
165 if dependency in file_by_name:
166 # Remove from elements to be visited, in order to cut cycles.
167 _AddFile(file_by_name.pop(dependency))
168 des_pool.Add(file_proto)
170 while file_by_name:
171 _AddFile(file_by_name.popitem()[1])
172 return GetMessageClassesForFiles(
173 [file_proto.name for file_proto in file_protos], des_pool
174 )