Package google :: Package protobuf :: Module message_factory
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Source Code for Module google.protobuf.message_factory

  1  # Protocol Buffers - Google's data interchange format 
  2  # Copyright 2008 Google Inc.  All rights reserved. 
  3  # https://developers.google.com/protocol-buffers/ 
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 30   
 31  """Provides a factory class for generating dynamic messages. 
 32   
 33  The easiest way to use this class is if you have access to the FileDescriptor 
 34  protos containing the messages you want to create you can just do the following: 
 35   
 36  message_classes = message_factory.GetMessages(iterable_of_file_descriptors) 
 37  my_proto_instance = message_classes['some.proto.package.MessageName']() 
 38  """ 
 39   
 40  __author__ = 'matthewtoia@google.com (Matt Toia)' 
 41   
 42  from google.protobuf.internal import api_implementation 
 43  from google.protobuf import descriptor_pool 
 44  from google.protobuf import message 
 45   
 46  if api_implementation.Type() == 'cpp': 
 47    from google.protobuf.pyext import cpp_message as message_impl 
 48  else: 
 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   
56 -class 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 # If module not set, it wrongly points to message_factory module. 87 self._classes[descriptor] = result_class 88 for field in descriptor.fields: 89 if field.message_type: 90 self.GetPrototype(field.message_type) 91 for extension in result_class.DESCRIPTOR.extensions: 92 if extension.containing_type not in self._classes: 93 self.GetPrototype(extension.containing_type) 94 extended_class = self._classes[extension.containing_type] 95 extended_class.RegisterExtension(extension) 96 return self._classes[descriptor]
97
98 - def GetMessages(self, files):
99 """Gets all the messages from a specified file. 100 101 This will find and resolve dependencies, failing if the descriptor 102 pool cannot satisfy them. 103 104 Args: 105 files: The file names to extract messages from. 106 107 Returns: 108 A dictionary mapping proto names to the message classes. This will include 109 any dependent messages as well as any messages defined in the same file as 110 a specified message. 111 """ 112 result = {} 113 for file_name in files: 114 file_desc = self.pool.FindFileByName(file_name) 115 for desc in file_desc.message_types_by_name.values(): 116 result[desc.full_name] = self.GetPrototype(desc) 117 118 # While the extension FieldDescriptors are created by the descriptor pool, 119 # the python classes created in the factory need them to be registered 120 # explicitly, which is done below. 121 # 122 # The call to RegisterExtension will specifically check if the 123 # extension was already registered on the object and either 124 # ignore the registration if the original was the same, or raise 125 # an error if they were different. 126 127 for extension in file_desc.extensions_by_name.values(): 128 if extension.containing_type not in self._classes: 129 self.GetPrototype(extension.containing_type) 130 extended_class = self._classes[extension.containing_type] 131 extended_class.RegisterExtension(extension) 132 return result
133 134 135 _FACTORY = MessageFactory() 136 137
138 -def GetMessages(file_protos):
139 """Builds a dictionary of all the messages available in a set of files. 140 141 Args: 142 file_protos: Iterable of FileDescriptorProto to build messages out of. 143 144 Returns: 145 A dictionary mapping proto names to the message classes. This will include 146 any dependent messages as well as any messages defined in the same file as 147 a specified message. 148 """ 149 # The cpp implementation of the protocol buffer library requires to add the 150 # message in topological order of the dependency graph. 151 file_by_name = {file_proto.name: file_proto for file_proto in file_protos} 152 def _AddFile(file_proto): 153 for dependency in file_proto.dependency: 154 if dependency in file_by_name: 155 # Remove from elements to be visited, in order to cut cycles. 156 _AddFile(file_by_name.pop(dependency)) 157 _FACTORY.pool.Add(file_proto)
158 while file_by_name: 159 _AddFile(file_by_name.popitem()[1]) 160 return _FACTORY.GetMessages([file_proto.name for file_proto in file_protos]) 161