1# Protocol Buffers - Google's data interchange format
2# Copyright 2008 Google Inc.  All rights reserved.
3# https://developers.google.com/protocol-buffers/
4#
5# Redistribution and use in source and binary forms, with or without
6# modification, are permitted provided that the following conditions are
7# met:
8#
9#     * Redistributions of source code must retain the above copyright
10# notice, this list of conditions and the following disclaimer.
11#     * Redistributions in binary form must reproduce the above
12# copyright notice, this list of conditions and the following disclaimer
13# in the documentation and/or other materials provided with the
14# distribution.
15#     * Neither the name of Google Inc. nor the names of its
16# contributors may be used to endorse or promote products derived from
17# this software without specific prior written permission.
18#
19# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30
31"""Provides a factory class for generating dynamic messages.
32
33The easiest way to use this class is if you have access to the FileDescriptor
34protos containing the messages you want to create you can just do the following:
35
36message_classes = message_factory.GetMessages(iterable_of_file_descriptors)
37my_proto_instance = message_classes['some.proto.package.MessageName']()
38"""
39
40__author__ = 'matthewtoia@google.com (Matt Toia)'
41
42from google.protobuf import descriptor_pool
43from google.protobuf import message
44from google.protobuf import reflection
45
46
47class MessageFactory(object):
48  """Factory for creating Proto2 messages from descriptors in a pool."""
49
50  def __init__(self, pool=None):
51    """Initializes a new factory."""
52    self.pool = pool or descriptor_pool.DescriptorPool()
53
54    # local cache of all classes built from protobuf descriptors
55    self._classes = {}
56
57  def GetPrototype(self, descriptor):
58    """Builds a proto2 message class based on the passed in descriptor.
59
60    Passing a descriptor with a fully qualified name matching a previous
61    invocation will cause the same class to be returned.
62
63    Args:
64      descriptor: The descriptor to build from.
65
66    Returns:
67      A class describing the passed in descriptor.
68    """
69    if descriptor.full_name not in self._classes:
70      descriptor_name = descriptor.name
71      if str is bytes:  # PY2
72        descriptor_name = descriptor.name.encode('ascii', 'ignore')
73      result_class = reflection.GeneratedProtocolMessageType(
74          descriptor_name,
75          (message.Message,),
76          {'DESCRIPTOR': descriptor, '__module__': None})
77          # If module not set, it wrongly points to the reflection.py module.
78      self._classes[descriptor.full_name] = result_class
79      for field in descriptor.fields:
80        if field.message_type:
81          self.GetPrototype(field.message_type)
82      for extension in result_class.DESCRIPTOR.extensions:
83        if extension.containing_type.full_name not in self._classes:
84          self.GetPrototype(extension.containing_type)
85        extended_class = self._classes[extension.containing_type.full_name]
86        extended_class.RegisterExtension(extension)
87    return self._classes[descriptor.full_name]
88
89  def GetMessages(self, files):
90    """Gets all the messages from a specified file.
91
92    This will find and resolve dependencies, failing if the descriptor
93    pool cannot satisfy them.
94
95    Args:
96      files: The file names to extract messages from.
97
98    Returns:
99      A dictionary mapping proto names to the message classes. This will include
100      any dependent messages as well as any messages defined in the same file as
101      a specified message.
102    """
103    result = {}
104    for file_name in files:
105      file_desc = self.pool.FindFileByName(file_name)
106      for name, msg in file_desc.message_types_by_name.items():
107        if file_desc.package:
108          full_name = '.'.join([file_desc.package, name])
109        else:
110          full_name = msg.name
111        result[full_name] = self.GetPrototype(
112            self.pool.FindMessageTypeByName(full_name))
113
114      # While the extension FieldDescriptors are created by the descriptor pool,
115      # the python classes created in the factory need them to be registered
116      # explicitly, which is done below.
117      #
118      # The call to RegisterExtension will specifically check if the
119      # extension was already registered on the object and either
120      # ignore the registration if the original was the same, or raise
121      # an error if they were different.
122
123      for name, extension in file_desc.extensions_by_name.items():
124        if extension.containing_type.full_name not in self._classes:
125          self.GetPrototype(extension.containing_type)
126        extended_class = self._classes[extension.containing_type.full_name]
127        extended_class.RegisterExtension(extension)
128    return result
129
130
131_FACTORY = MessageFactory()
132
133
134def GetMessages(file_protos):
135  """Builds a dictionary of all the messages available in a set of files.
136
137  Args:
138    file_protos: A sequence of file protos to build messages out of.
139
140  Returns:
141    A dictionary mapping proto names to the message classes. This will include
142    any dependent messages as well as any messages defined in the same file as
143    a specified message.
144  """
145  for file_proto in file_protos:
146    _FACTORY.pool.Add(file_proto)
147  return _FACTORY.GetMessages([file_proto.name for file_proto in file_protos])
148