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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
7"""Provides a factory class for generating dynamic messages.
9The easiest way to use this class is if you have access to the FileDescriptor
10protos containing the messages you want to create you can just do the following:
12message_classes = message_factory.GetMessages(iterable_of_file_descriptors)
13my_proto_instance = message_classes['some.proto.package.MessageName']()
14"""
16__author__ = 'matthewtoia@google.com (Matt Toia)'
18import warnings
20from google.protobuf import descriptor_pool
21from google.protobuf import message
22from google.protobuf.internal import api_implementation
24if api_implementation.Type() == 'python':
25 from google.protobuf.internal import python_message as message_impl
26else:
27 from google.protobuf.pyext import cpp_message as message_impl # pylint: disable=g-import-not-at-top
29# The type of all Message classes.
30_GENERATED_PROTOCOL_MESSAGE_TYPE = message_impl.GeneratedProtocolMessageType
33def GetMessageClass(descriptor):
34 """Obtains a proto2 message class based on the passed in descriptor.
36 Passing a descriptor with a fully qualified name matching a previous
37 invocation will cause the same class to be returned.
39 Args:
40 descriptor: The descriptor to build from.
42 Returns:
43 A class describing the passed in descriptor.
44 """
45 concrete_class = getattr(descriptor, '_concrete_class', None)
46 if concrete_class:
47 return concrete_class
48 return _InternalCreateMessageClass(descriptor)
51def GetMessageClassesForFiles(files, pool):
52 """Gets all the messages from specified files.
54 This will find and resolve dependencies, failing if the descriptor
55 pool cannot satisfy them.
57 This will not return the classes for nested types within those classes, for
58 those, use GetMessageClass() on the nested types within their containing
59 messages.
61 For example, for the message:
63 message NestedTypeMessage {
64 message NestedType {
65 string data = 1;
66 }
67 NestedType nested = 1;
68 }
70 NestedTypeMessage will be in the result, but not
71 NestedTypeMessage.NestedType.
73 Args:
74 files: The file names to extract messages from.
75 pool: The descriptor pool to find the files including the dependent files.
77 Returns:
78 A dictionary mapping proto names to the message classes.
79 """
80 result = {}
81 for file_name in files:
82 file_desc = pool.FindFileByName(file_name)
83 for desc in file_desc.message_types_by_name.values():
84 result[desc.full_name] = GetMessageClass(desc)
86 # While the extension FieldDescriptors are created by the descriptor pool,
87 # the python classes created in the factory need them to be registered
88 # explicitly, which is done below.
89 #
90 # The call to RegisterExtension will specifically check if the
91 # extension was already registered on the object and either
92 # ignore the registration if the original was the same, or raise
93 # an error if they were different.
95 for extension in file_desc.extensions_by_name.values():
96 _ = GetMessageClass(extension.containing_type)
97 if api_implementation.Type() != 'python':
98 # TODO: Remove this check here. Duplicate extension
99 # register check should be in descriptor_pool.
100 if extension is not pool.FindExtensionByNumber(
101 extension.containing_type, extension.number
102 ):
103 raise ValueError('Double registration of Extensions')
104 # Recursively load protos for extension field, in order to be able to
105 # fully represent the extension. This matches the behavior for regular
106 # fields too.
107 if extension.message_type:
108 GetMessageClass(extension.message_type)
109 return result
112def _InternalCreateMessageClass(descriptor):
113 """Builds a proto2 message class based on the passed in descriptor.
115 Args:
116 descriptor: The descriptor to build from.
118 Returns:
119 A class describing the passed in descriptor.
120 """
121 descriptor_name = descriptor.name
122 result_class = _GENERATED_PROTOCOL_MESSAGE_TYPE(
123 descriptor_name,
124 (message.Message,),
125 {
126 'DESCRIPTOR': descriptor,
127 # If module not set, it wrongly points to message_factory module.
128 '__module__': None,
129 },
130 )
131 for field in descriptor.fields:
132 if field.message_type:
133 GetMessageClass(field.message_type)
135 for extension in result_class.DESCRIPTOR.extensions:
136 extended_class = GetMessageClass(extension.containing_type)
137 if api_implementation.Type() != 'python':
138 # TODO: Remove this check here. Duplicate extension
139 # register check should be in descriptor_pool.
140 pool = extension.containing_type.file.pool
141 if extension is not pool.FindExtensionByNumber(
142 extension.containing_type, extension.number
143 ):
144 raise ValueError('Double registration of Extensions')
145 if extension.message_type:
146 GetMessageClass(extension.message_type)
147 return result_class
150# Deprecated. Please use GetMessageClass() or GetMessageClassesForFiles()
151# method above instead.
152class MessageFactory(object):
153 """Factory for creating Proto2 messages from descriptors in a pool."""
155 def __init__(self, pool=None):
156 """Initializes a new factory."""
157 self.pool = pool or descriptor_pool.DescriptorPool()
160def GetMessages(file_protos, pool=None):
161 """Builds a dictionary of all the messages available in a set of files.
163 Args:
164 file_protos: Iterable of FileDescriptorProto to build messages out of.
165 pool: The descriptor pool to add the file protos.
167 Returns:
168 A dictionary mapping proto names to the message classes. This will include
169 any dependent messages as well as any messages defined in the same file as
170 a specified message.
171 """
172 # The cpp implementation of the protocol buffer library requires to add the
173 # message in topological order of the dependency graph.
174 des_pool = pool or descriptor_pool.DescriptorPool()
175 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 des_pool.Add(file_proto)
184 while file_by_name:
185 _AddFile(file_by_name.popitem()[1])
186 return GetMessageClassesForFiles(
187 [file_proto.name for file_proto in file_protos], des_pool
188 )