1 # Protocol Buffers - Google's data interchange format
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3 # https://developers.google.com/protocol-buffers/
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31 """A database of Python protocol buffer generated symbols.
33 SymbolDatabase makes it easy to create new instances of a registered type, given
34 only the type's protocol buffer symbol name. Once all symbols are registered,
35 they can be accessed using either the MessageFactory interface which
36 SymbolDatabase exposes, or the DescriptorPool interface of the underlying
41 db = symbol_database.SymbolDatabase()
43 # Register symbols of interest, from one or multiple files.
44 db.RegisterFileDescriptor(my_proto_pb2.DESCRIPTOR)
45 db.RegisterMessage(my_proto_pb2.MyMessage)
46 db.RegisterEnumDescriptor(my_proto_pb2.MyEnum.DESCRIPTOR)
48 # The database can be used as a MessageFactory, to generate types based on
50 types = db.GetMessages(['my_proto.proto'])
51 my_message_instance = types['MyMessage']()
53 # The database's underlying descriptor pool can be queried, so it's not
54 # necessary to know a type's filename to be able to generate it:
55 filename = db.pool.FindFileContainingSymbol('MyMessage')
56 my_message_instance = db.GetMessages([filename])['MyMessage']()
58 # This functionality is also provided directly via a convenience method:
59 my_message_instance = db.GetSymbol('MyMessage')()
63 from google.protobuf import descriptor_pool
66 class SymbolDatabase(object):
67 """A database of Python generated symbols.
69 SymbolDatabase also models message_factory.MessageFactory.
71 The symbol database can be used to keep a global registry of all protocol
72 buffer types used within a program.
79 self._symbols_by_file = {}
80 self.pool = descriptor_pool.DescriptorPool()
82 def RegisterMessage(self, message):
83 """Registers the given message type in the local database.
86 message: a message.Message, to be registered.
92 desc = message.DESCRIPTOR
93 self._symbols[desc.full_name] = message
94 if desc.file.name not in self._symbols_by_file:
95 self._symbols_by_file[desc.file.name] = {}
96 self._symbols_by_file[desc.file.name][desc.full_name] = message
97 self.pool.AddDescriptor(desc)
100 def RegisterEnumDescriptor(self, enum_descriptor):
101 """Registers the given enum descriptor in the local database.
104 enum_descriptor: a descriptor.EnumDescriptor.
107 The provided descriptor.
109 self.pool.AddEnumDescriptor(enum_descriptor)
110 return enum_descriptor
112 def RegisterFileDescriptor(self, file_descriptor):
113 """Registers the given file descriptor in the local database.
116 file_descriptor: a descriptor.FileDescriptor.
119 The provided descriptor.
121 self.pool.AddFileDescriptor(file_descriptor)
123 def GetSymbol(self, symbol):
124 """Tries to find a symbol in the local database.
126 Currently, this method only returns message.Message instances, however, if
127 may be extended in future to support other symbol types.
130 symbol: A str, a protocol buffer symbol.
133 A Python class corresponding to the symbol.
136 KeyError: if the symbol could not be found.
139 return self._symbols[symbol]
141 def GetPrototype(self, descriptor):
142 """Builds a proto2 message class based on the passed in descriptor.
144 Passing a descriptor with a fully qualified name matching a previous
145 invocation will cause the same class to be returned.
148 descriptor: The descriptor to build from.
151 A class describing the passed in descriptor.
154 return self.GetSymbol(descriptor.full_name)
156 def GetMessages(self, files):
157 """Gets all the messages from a specified file.
159 This will find and resolve dependencies, failing if they are not registered
160 in the symbol database.
164 files: The file names to extract messages from.
167 A dictionary mapping proto names to the message classes. This will include
168 any dependent messages as well as any messages defined in the same file as
172 KeyError: if a file could not be found.
177 result.update(self._symbols_by_file[f])
180 _DEFAULT = SymbolDatabase()
184 """Returns the default SymbolDatabase."""