152 lines
6.1 KiB
Python
152 lines
6.1 KiB
Python
# Protocol Buffers - Google's data interchange format
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# Copyright 2008 Google Inc. All rights reserved.
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# https://developers.google.com/protocol-buffers/
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are
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# met:
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#
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# * Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following disclaimer
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# in the documentation and/or other materials provided with the
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# distribution.
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# * Neither the name of Google Inc. nor the names of its
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# contributors may be used to endorse or promote products derived from
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# this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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"""Provides a factory class for generating dynamic messages.
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The easiest way to use this class is if you have access to the FileDescriptor
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protos containing the messages you want to create you can just do the following:
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message_classes = message_factory.GetMessages(iterable_of_file_descriptors)
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my_proto_instance = message_classes['some.proto.package.MessageName']()
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"""
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__author__ = 'matthewtoia@google.com (Matt Toia)'
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from google.protobuf import descriptor_pool
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from google.protobuf import message
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from google.protobuf import reflection
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class MessageFactory(object):
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"""Factory for creating Proto2 messages from descriptors in a pool."""
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def __init__(self, pool=None):
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"""Initializes a new factory."""
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self.pool = pool or descriptor_pool.DescriptorPool()
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# local cache of all classes built from protobuf descriptors
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self._classes = {}
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def GetPrototype(self, descriptor):
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"""Builds a proto2 message class based on the passed in descriptor.
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Passing a descriptor with a fully qualified name matching a previous
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invocation will cause the same class to be returned.
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Args:
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descriptor: The descriptor to build from.
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Returns:
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A class describing the passed in descriptor.
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"""
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if descriptor not in self._classes:
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descriptor_name = descriptor.name
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if str is bytes: # PY2
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descriptor_name = descriptor.name.encode('ascii', 'ignore')
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result_class = reflection.GeneratedProtocolMessageType(
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descriptor_name,
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(message.Message,),
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{'DESCRIPTOR': descriptor, '__module__': None})
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# If module not set, it wrongly points to the reflection.py module.
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self._classes[descriptor] = result_class
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for field in descriptor.fields:
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if field.message_type:
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self.GetPrototype(field.message_type)
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for extension in result_class.DESCRIPTOR.extensions:
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if extension.containing_type not in self._classes:
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self.GetPrototype(extension.containing_type)
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extended_class = self._classes[extension.containing_type]
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extended_class.RegisterExtension(extension)
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return self._classes[descriptor]
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def GetMessages(self, files):
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"""Gets all the messages from a specified file.
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This will find and resolve dependencies, failing if the descriptor
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pool cannot satisfy them.
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Args:
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files: The file names to extract messages from.
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Returns:
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A dictionary mapping proto names to the message classes. This will include
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any dependent messages as well as any messages defined in the same file as
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a specified message.
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"""
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result = {}
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for file_name in files:
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file_desc = self.pool.FindFileByName(file_name)
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for desc in list(file_desc.message_types_by_name.values()):
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result[desc.full_name] = self.GetPrototype(desc)
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# While the extension FieldDescriptors are created by the descriptor pool,
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# the python classes created in the factory need them to be registered
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# explicitly, which is done below.
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#
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# The call to RegisterExtension will specifically check if the
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# extension was already registered on the object and either
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# ignore the registration if the original was the same, or raise
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# an error if they were different.
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for extension in list(file_desc.extensions_by_name.values()):
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if extension.containing_type not in self._classes:
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self.GetPrototype(extension.containing_type)
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extended_class = self._classes[extension.containing_type]
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extended_class.RegisterExtension(extension)
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return result
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_FACTORY = MessageFactory()
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def GetMessages(file_protos):
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"""Builds a dictionary of all the messages available in a set of files.
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Args:
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file_protos: Iterable of FileDescriptorProto to build messages out of.
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Returns:
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A dictionary mapping proto names to the message classes. This will include
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any dependent messages as well as any messages defined in the same file as
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a specified message.
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"""
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# The cpp implementation of the protocol buffer library requires to add the
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# message in topological order of the dependency graph.
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file_by_name = {file_proto.name: file_proto for file_proto in file_protos}
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def _AddFile(file_proto):
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for dependency in file_proto.dependency:
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if dependency in file_by_name:
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# Remove from elements to be visited, in order to cut cycles.
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_AddFile(file_by_name.pop(dependency))
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_FACTORY.pool.Add(file_proto)
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while file_by_name:
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_AddFile(file_by_name.popitem()[1])
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return _FACTORY.GetMessages([file_proto.name for file_proto in file_protos])
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