1# Protocol Buffers - Google's data interchange format
2# Copyright 2008 Google Inc.  All rights reserved.
3# http://code.google.com/p/protobuf/
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30
31"""Provides a factory class for generating dynamic messages."""
32
33__author__ = 'matthewtoia@google.com (Matt Toia)'
34
35from google.protobuf import descriptor_database
36from google.protobuf import descriptor_pool
37from google.protobuf import message
38from google.protobuf import reflection
39
40
41class MessageFactory(object):
42  """Factory for creating Proto2 messages from descriptors in a pool."""
43
44  def __init__(self):
45    """Initializes a new factory."""
46    self._classes = {}
47
48  def GetPrototype(self, descriptor):
49    """Builds a proto2 message class based on the passed in descriptor.
50
51    Passing a descriptor with a fully qualified name matching a previous
52    invocation will cause the same class to be returned.
53
54    Args:
55      descriptor: The descriptor to build from.
56
57    Returns:
58      A class describing the passed in descriptor.
59    """
60
61    if descriptor.full_name not in self._classes:
62      result_class = reflection.GeneratedProtocolMessageType(
63          descriptor.name.encode('ascii', 'ignore'),
64          (message.Message,),
65          {'DESCRIPTOR': descriptor})
66      self._classes[descriptor.full_name] = result_class
67      for field in descriptor.fields:
68        if field.message_type:
69          self.GetPrototype(field.message_type)
70    return self._classes[descriptor.full_name]
71
72
73_DB = descriptor_database.DescriptorDatabase()
74_POOL = descriptor_pool.DescriptorPool(_DB)
75_FACTORY = MessageFactory()
76
77
78def GetMessages(file_protos):
79  """Builds a dictionary of all the messages available in a set of files.
80
81  Args:
82    file_protos: A sequence of file protos to build messages out of.
83
84  Returns:
85    A dictionary containing all the message types in the files mapping the
86    fully qualified name to a Message subclass for the descriptor.
87  """
88
89  result = {}
90  for file_proto in file_protos:
91    _DB.Add(file_proto)
92  for file_proto in file_protos:
93    for desc in _GetAllDescriptors(file_proto.message_type, file_proto.package):
94      result[desc.full_name] = _FACTORY.GetPrototype(desc)
95  return result
96
97
98def _GetAllDescriptors(desc_protos, package):
99  """Gets all levels of nested message types as a flattened list of descriptors.
100
101  Args:
102    desc_protos: The descriptor protos to process.
103    package: The package where the protos are defined.
104
105  Yields:
106    Each message descriptor for each nested type.
107  """
108
109  for desc_proto in desc_protos:
110    name = '.'.join((package, desc_proto.name))
111    yield _POOL.FindMessageTypeByName(name)
112    for nested_desc in _GetAllDescriptors(desc_proto.nested_type, name):
113      yield nested_desc
114