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)