protobuf_json.py

# JSON serialization support for Google's protobuf Messages
# Copyright (c) 2009, Paul Dovbush
# All rights reserved.
# http://code.google.com/p/protobuf-json/
#
# 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 <ORGANIZATION> 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
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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'''
Provide serialization and de-serialization of Google's protobuf Messages into/from JSON format.
'''

# groups are deprecated and not supported;
# Note that preservation of unknown fields is currently not available for Python (c) google docs
# extensions is not supported from 0.0.5 (due to gpb2.3 changes)

__version__='0.0.5'
__author__='Paul Dovbush <dpp@dpp.su>'


import json	# py2.6+ TODO: add support for other JSON serialization modules
from google.protobuf.descriptor import FieldDescriptor as FD


class ParseError(Exception): pass


def json2pb(pb, js):
	''' convert JSON string to google.protobuf.descriptor instance '''
	for field in pb.DESCRIPTOR.fields:
		if field.name not in js:
			continue
		if field.type == FD.TYPE_MESSAGE:
			pass
		elif field.type in _js2ftype:
			ftype = _js2ftype[field.type]
		else: 
			raise ParseError("Field %s.%s of type '%d' is not supported" % (pb.__class__.__name__, field.name, field.type, ))
		value = js[field.name]
		if field.label == FD.LABEL_REPEATED:
			pb_value = getattr(pb, field.name, None)
			for v in value:
				if field.type == FD.TYPE_MESSAGE:
					json2pb(pb_value.add(), v)
				else:
					pb_value.append(ftype(v))
		else:
			if field.type == FD.TYPE_MESSAGE:
				json2pb(getattr(pb, field.name, None), value)
			else:
				setattr(pb, field.name, ftype(value))
	return pb



def pb2json(pb):
	''' convert google.protobuf.descriptor instance to JSON string '''
	js = {}
	# fields = pb.DESCRIPTOR.fields #all fields
	fields = pb.ListFields()	#only filled (including extensions)
	for field,value in fields:
		if field.type == FD.TYPE_MESSAGE:
			ftype = pb2json
		elif field.type in _ftype2js:
			ftype = _ftype2js[field.type]
		else:
			raise ParseError("Field %s.%s of type '%d' is not supported" % (pb.__class__.__name__, field.name, field.type, ))
		if field.label == FD.LABEL_REPEATED:
			js_value = []
			for v in value:
				js_value.append(ftype(v))
		else:
			js_value = ftype(value)
		js[field.name] = js_value
	return js


_ftype2js = {
	FD.TYPE_DOUBLE: float,
	FD.TYPE_FLOAT: float,
	FD.TYPE_INT64: long,
	FD.TYPE_UINT64: long,
	FD.TYPE_INT32: int,
	FD.TYPE_FIXED64: float,
	FD.TYPE_FIXED32: float,
	FD.TYPE_BOOL: bool,
	FD.TYPE_STRING: unicode,
	#FD.TYPE_MESSAGE: pb2json,		#handled specially
	FD.TYPE_BYTES: lambda x: x.encode('string_escape'),
	FD.TYPE_UINT32: int,
	FD.TYPE_ENUM: int,
	FD.TYPE_SFIXED32: float,
	FD.TYPE_SFIXED64: float,
	FD.TYPE_SINT32: int,
	FD.TYPE_SINT64: long,
}

_js2ftype = {
	FD.TYPE_DOUBLE: float,
	FD.TYPE_FLOAT: float,
	FD.TYPE_INT64: long,
	FD.TYPE_UINT64: long,
	FD.TYPE_INT32: int,
	FD.TYPE_FIXED64: float,
	FD.TYPE_FIXED32: float,
	FD.TYPE_BOOL: bool,
	FD.TYPE_STRING: unicode,
	# FD.TYPE_MESSAGE: json2pb,	#handled specially
	FD.TYPE_BYTES: lambda x: x.decode('string_escape'),
	FD.TYPE_UINT32: int,
	FD.TYPE_ENUM: int,
	FD.TYPE_SFIXED32: float,
	FD.TYPE_SFIXED64: float,
	FD.TYPE_SINT32: int,
	FD.TYPE_SINT64: long,
}