protolib.py revision 10107:524afa92d940
1#!/usr/bin/env python 2 3# Copyright (c) 2013 ARM Limited 4# All rights reserved 5# 6# The license below extends only to copyright in the software and shall 7# not be construed as granting a license to any other intellectual 8# property including but not limited to intellectual property relating 9# to a hardware implementation of the functionality of the software 10# licensed hereunder. You may use the software subject to the license 11# terms below provided that you ensure that this notice is replicated 12# unmodified and in its entirety in all distributions of the software, 13# modified or unmodified, in source code or in binary form. 14# 15# Redistribution and use in source and binary forms, with or without 16# modification, are permitted provided that the following conditions are 17# met: redistributions of source code must retain the above copyright 18# notice, this list of conditions and the following disclaimer; 19# redistributions in binary form must reproduce the above copyright 20# notice, this list of conditions and the following disclaimer in the 21# documentation and/or other materials provided with the distribution; 22# neither the name of the copyright holders nor the names of its 23# contributors may be used to endorse or promote products derived from 24# this software without specific prior written permission. 25# 26# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 27# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 28# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 29# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 30# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 31# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 32# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 36# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37# 38# Copyright 2008 Google Inc. All rights reserved. 39# http://code.google.com/p/protobuf/ 40# 41# Redistribution and use in source and binary forms, with or without 42# modification, are permitted provided that the following conditions are 43# met: 44# 45# * Redistributions of source code must retain the above copyright 46# notice, this list of conditions and the following disclaimer. 47# * Redistributions in binary form must reproduce the above 48# copyright notice, this list of conditions and the following disclaimer 49# in the documentation and/or other materials provided with the 50# distribution. 51# * Neither the name of Google Inc. nor the names of its 52# contributors may be used to endorse or promote products derived from 53# this software without specific prior written permission. 54# 55# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 56# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 57# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 58# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 59# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 60# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 61# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 62# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 63# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 64# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 65# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 66# 67# Authors: Andreas Hansson 68# Radhika Jagtap 69 70# This file is a library of commonly used functions used when interfacing 71# with protobuf python messages. For eg, the decode scripts for different 72# types of proto objects can use the same function to decode a single message 73 74import struct 75 76def DecodeVarint(in_file): 77 """ 78 The decoding of the Varint32 is copied from 79 google.protobuf.internal.decoder and is only repeated here to 80 avoid depending on the internal functions in the library. If the 81 end of file is reached, return (0, 0). 82 """ 83 result = 0 84 shift = 0 85 pos = 0 86 # Use a 32-bit mask 87 mask = 0xffffffff 88 while 1: 89 c = in_file.read(1) 90 if len(c) == 0: 91 return (0, 0) 92 b = struct.unpack('<B', c)[0] 93 result |= ((b & 0x7f) << shift) 94 pos += 1 95 if not (b & 0x80): 96 if result > 0x7fffffffffffffff: 97 result -= (1 << 64) 98 result |= ~mask 99 else: 100 result &= mask 101 return (result, pos) 102 shift += 7 103 if shift >= 64: 104 raise IOError('Too many bytes when decoding varint.') 105 106def decodeMessage(in_file, message): 107 """ 108 Attempt to read a message from the file and decode it. Return 109 False if no message could be read. 110 """ 111 try: 112 size, pos = DecodeVarint(in_file) 113 if size == 0: 114 return False 115 buf = in_file.read(size) 116 message.ParseFromString(buf) 117 return True 118 except IOError: 119 return False 120 121def EncodeVarint(out_file, value): 122 """ 123 The encoding of the Varint32 is copied from 124 google.protobuf.internal.encoder and is only repeated here to 125 avoid depending on the internal functions in the library. 126 """ 127 bits = value & 0x7f 128 value >>= 7 129 while value: 130 out_file.write(struct.pack('<B', 0x80|bits)) 131 bits = value & 0x7f 132 value >>= 7 133 out_file.write(struct.pack('<B', bits)) 134 135def encodeMessage(out_file, message): 136 """ 137 Encoded a message with the length prepended as a 32-bit varint. 138 """ 139 out = message.SerializeToString() 140 EncodeVarint(out_file, len(out)) 141 out_file.write(out) 142