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# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc. All rights reserved.
# http://code.google.com/p/protobuf/
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"""Provides a factory class for generating dynamic messages."""
__author__ = 'matthewtoia@google.com (Matt Toia)'
from google.protobuf import descriptor_database
from google.protobuf import descriptor_pool
from google.protobuf import message
from google.protobuf import reflection
class MessageFactory(object):
"""Factory for creating Proto2 messages from descriptors in a pool."""
def __init__(self):
"""Initializes a new factory."""
self._classes = {}
def GetPrototype(self, descriptor):
"""Builds a proto2 message class based on the passed in descriptor.
Passing a descriptor with a fully qualified name matching a previous
invocation will cause the same class to be returned.
Args:
descriptor: The descriptor to build from.
Returns:
A class describing the passed in descriptor.
"""
if descriptor.full_name not in self._classes:
result_class = reflection.GeneratedProtocolMessageType(
descriptor.name.encode('ascii', 'ignore'),
(message.Message,),
{'DESCRIPTOR': descriptor})
self._classes[descriptor.full_name] = result_class
for field in descriptor.fields:
if field.message_type:
self.GetPrototype(field.message_type)
return self._classes[descriptor.full_name]
_DB = descriptor_database.DescriptorDatabase()
_POOL = descriptor_pool.DescriptorPool(_DB)
_FACTORY = MessageFactory()
def GetMessages(file_protos):
"""Builds a dictionary of all the messages available in a set of files.
Args:
file_protos: A sequence of file protos to build messages out of.
Returns:
A dictionary containing all the message types in the files mapping the
fully qualified name to a Message subclass for the descriptor.
"""
result = {}
for file_proto in file_protos:
_DB.Add(file_proto)
for file_proto in file_protos:
for desc in _GetAllDescriptors(file_proto.message_type, file_proto.package):
result[desc.full_name] = _FACTORY.GetPrototype(desc)
return result
def _GetAllDescriptors(desc_protos, package):
"""Gets all levels of nested message types as a flattened list of descriptors.
Args:
desc_protos: The descriptor protos to process.
package: The package where the protos are defined.
Yields:
Each message descriptor for each nested type.
"""
for desc_proto in desc_protos:
name = '.'.join((package, desc_proto.name))
yield _POOL.FindMessageTypeByName(name)
for nested_desc in _GetAllDescriptors(desc_proto.nested_type, name):
yield nested_desc
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