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Diffstat (limited to 'generator/google/protobuf/reflection.py')
-rw-r--r-- | generator/google/protobuf/reflection.py | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/generator/google/protobuf/reflection.py b/generator/google/protobuf/reflection.py new file mode 100644 index 0000000..9570fd5 --- /dev/null +++ b/generator/google/protobuf/reflection.py @@ -0,0 +1,169 @@ +# Protocol Buffers - Google's data interchange format +# Copyright 2008 Google Inc. All rights reserved. +# http://code.google.com/p/protobuf/ +# +# 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. + +# This code is meant to work on Python 2.4 and above only. + +"""Contains a metaclass and helper functions used to create +protocol message classes from Descriptor objects at runtime. + +Recall that a metaclass is the "type" of a class. +(A class is to a metaclass what an instance is to a class.) + +In this case, we use the GeneratedProtocolMessageType metaclass +to inject all the useful functionality into the classes +output by the protocol compiler at compile-time. + +The upshot of all this is that the real implementation +details for ALL pure-Python protocol buffers are *here in +this file*. +""" + +__author__ = 'robinson@google.com (Will Robinson)' + + +from google.protobuf.internal import api_implementation +from google.protobuf import descriptor as descriptor_mod +from google.protobuf import message + +_FieldDescriptor = descriptor_mod.FieldDescriptor + + +if api_implementation.Type() == 'cpp': + if api_implementation.Version() == 2: + from google.protobuf.internal.cpp import cpp_message + _NewMessage = cpp_message.NewMessage + _InitMessage = cpp_message.InitMessage + else: + from google.protobuf.internal import cpp_message + _NewMessage = cpp_message.NewMessage + _InitMessage = cpp_message.InitMessage +else: + from google.protobuf.internal import python_message + _NewMessage = python_message.NewMessage + _InitMessage = python_message.InitMessage + + +class GeneratedProtocolMessageType(type): + + """Metaclass for protocol message classes created at runtime from Descriptors. + + We add implementations for all methods described in the Message class. We + also create properties to allow getting/setting all fields in the protocol + message. Finally, we create slots to prevent users from accidentally + "setting" nonexistent fields in the protocol message, which then wouldn't get + serialized / deserialized properly. + + The protocol compiler currently uses this metaclass to create protocol + message classes at runtime. Clients can also manually create their own + classes at runtime, as in this example: + + mydescriptor = Descriptor(.....) + class MyProtoClass(Message): + __metaclass__ = GeneratedProtocolMessageType + DESCRIPTOR = mydescriptor + myproto_instance = MyProtoClass() + myproto.foo_field = 23 + ... + """ + + # Must be consistent with the protocol-compiler code in + # proto2/compiler/internal/generator.*. + _DESCRIPTOR_KEY = 'DESCRIPTOR' + + def __new__(cls, name, bases, dictionary): + """Custom allocation for runtime-generated class types. + + We override __new__ because this is apparently the only place + where we can meaningfully set __slots__ on the class we're creating(?). + (The interplay between metaclasses and slots is not very well-documented). + + Args: + name: Name of the class (ignored, but required by the + metaclass protocol). + bases: Base classes of the class we're constructing. + (Should be message.Message). We ignore this field, but + it's required by the metaclass protocol + dictionary: The class dictionary of the class we're + constructing. dictionary[_DESCRIPTOR_KEY] must contain + a Descriptor object describing this protocol message + type. + + Returns: + Newly-allocated class. + """ + descriptor = dictionary[GeneratedProtocolMessageType._DESCRIPTOR_KEY] + bases = _NewMessage(bases, descriptor, dictionary) + superclass = super(GeneratedProtocolMessageType, cls) + + new_class = superclass.__new__(cls, name, bases, dictionary) + setattr(descriptor, '_concrete_class', new_class) + return new_class + + def __init__(cls, name, bases, dictionary): + """Here we perform the majority of our work on the class. + We add enum getters, an __init__ method, implementations + of all Message methods, and properties for all fields + in the protocol type. + + Args: + name: Name of the class (ignored, but required by the + metaclass protocol). + bases: Base classes of the class we're constructing. + (Should be message.Message). We ignore this field, but + it's required by the metaclass protocol + dictionary: The class dictionary of the class we're + constructing. dictionary[_DESCRIPTOR_KEY] must contain + a Descriptor object describing this protocol message + type. + """ + descriptor = dictionary[GeneratedProtocolMessageType._DESCRIPTOR_KEY] + _InitMessage(descriptor, cls) + superclass = super(GeneratedProtocolMessageType, cls) + superclass.__init__(name, bases, dictionary) + + +def ParseMessage(descriptor, byte_str): + """Generate a new Message instance from this Descriptor and a byte string. + + Args: + descriptor: Protobuf Descriptor object + byte_str: Serialized protocol buffer byte string + + Returns: + Newly created protobuf Message object. + """ + + class _ResultClass(message.Message): + __metaclass__ = GeneratedProtocolMessageType + DESCRIPTOR = descriptor + + new_msg = _ResultClass() + new_msg.ParseFromString(byte_str) + return new_msg |