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diff --git a/python/google/protobuf/proto_builder.py b/python/google/protobuf/proto_builder.py
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+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# https://developers.google.com/protocol-buffers/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Dynamic Protobuf class creator."""
+
+import hashlib
+import os
+
+from google.protobuf import descriptor_pb2
+from google.protobuf import message_factory
+
+
+def _GetMessageFromFactory(factory, full_name):
+  """Get a proto class from the MessageFactory by name.
+
+  Args:
+    factory: a MessageFactory instance.
+    full_name: str, the fully qualified name of the proto type.
+  Returns:
+    a class, for the type identified by full_name.
+  Raises:
+    KeyError, if the proto is not found in the factory's descriptor pool.
+  """
+  proto_descriptor = factory.pool.FindMessageTypeByName(full_name)
+  proto_cls = factory.GetPrototype(proto_descriptor)
+  return proto_cls
+
+
+def MakeSimpleProtoClass(fields, full_name, pool=None):
+  """Create a Protobuf class whose fields are basic types.
+
+  Note: this doesn't validate field names!
+
+  Args:
+    fields: dict of {name: field_type} mappings for each field in the proto.
+    full_name: str, the fully-qualified name of the proto type.
+    pool: optional DescriptorPool instance.
+  Returns:
+    a class, the new protobuf class with a FileDescriptor.
+  """
+  factory = message_factory.MessageFactory(pool=pool)
+  try:
+    proto_cls = _GetMessageFromFactory(factory, full_name)
+    return proto_cls
+  except KeyError:
+    # The factory's DescriptorPool doesn't know about this class yet.
+    pass
+
+  # Use a consistent file name that is unlikely to conflict with any imported
+  # proto files.
+  fields_hash = hashlib.sha1()
+  for f_name, f_type in sorted(fields.items()):
+    fields_hash.update(f_name.encode('utf8'))
+    fields_hash.update(str(f_type).encode('utf8'))
+  proto_file_name = fields_hash.hexdigest() + '.proto'
+
+  package, name = full_name.rsplit('.', 1)
+  file_proto = descriptor_pb2.FileDescriptorProto()
+  file_proto.name = os.path.join(package.replace('.', '/'), proto_file_name)
+  file_proto.package = package
+  desc_proto = file_proto.message_type.add()
+  desc_proto.name = name
+  for f_number, (f_name, f_type) in enumerate(sorted(fields.items()), 1):
+    field_proto = desc_proto.field.add()
+    field_proto.name = f_name
+    field_proto.number = f_number
+    field_proto.label = descriptor_pb2.FieldDescriptorProto.LABEL_OPTIONAL
+    field_proto.type = f_type
+
+  factory.pool.Add(file_proto)
+  return _GetMessageFromFactory(factory, full_name)