1#!/usr/bin/env python2.7
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 gzip
75import struct
76
77def openFileRd(in_file):
78    """
79    This opens the file passed as argument for reading using an appropriate
80    function depending on if it is gzipped or not. It returns the file
81    handle.
82    """
83    try:
84        # First see if this file is gzipped
85        try:
86            # Opening the file works even if it is not a gzip file
87            proto_in = gzip.open(in_file, 'rb')
88
89            # Force a check of the magic number by seeking in the
90            # file. If we do not do it here the error will occur when
91            # reading the first message.
92            proto_in.seek(1)
93            proto_in.seek(0)
94        except IOError:
95            proto_in = open(in_file, 'rb')
96    except IOError:
97        print "Failed to open ", in_file, " for reading"
98        exit(-1)
99    return proto_in
100
101def _DecodeVarint32(in_file):
102    """
103    The decoding of the Varint32 is copied from
104    google.protobuf.internal.decoder and is only repeated here to
105    avoid depending on the internal functions in the library. If the
106    end of file is reached, return (0, 0).
107    """
108    result = 0
109    shift = 0
110    pos = 0
111    # Use a 32-bit mask
112    mask = 0xffffffff
113    while 1:
114        c = in_file.read(1)
115        if len(c) == 0:
116            return (0, 0)
117        b = struct.unpack('<B', c)[0]
118        result |= ((b & 0x7f) << shift)
119        pos += 1
120        if not (b & 0x80):
121            if result > 0x7fffffffffffffff:
122                result -= (1 << 64)
123                result |= ~mask
124            else:
125                result &= mask
126            return (result, pos)
127        shift += 7
128        if shift >= 64:
129            raise IOError('Too many bytes when decoding varint.')
130
131def decodeMessage(in_file, message):
132    """
133    Attempt to read a message from the file and decode it. Return
134    False if no message could be read.
135    """
136    try:
137        size, pos = _DecodeVarint32(in_file)
138        if size == 0:
139            return False
140        buf = in_file.read(size)
141        message.ParseFromString(buf)
142        return True
143    except IOError:
144        return False
145
146def _EncodeVarint32(out_file, value):
147  """
148  The encoding of the Varint32 is copied from
149  google.protobuf.internal.encoder and is only repeated here to
150  avoid depending on the internal functions in the library.
151  """
152  bits = value & 0x7f
153  value >>= 7
154  while value:
155    out_file.write(struct.pack('<B', 0x80 | bits))
156    bits = value & 0x7f
157    value >>= 7
158  out_file.write(struct.pack('<B', bits))
159
160def encodeMessage(out_file, message):
161    """
162    Encoded a message with the length prepended as a 32-bit varint.
163    """
164    out = message.SerializeToString()
165    _EncodeVarint32(out_file, len(out))
166    out_file.write(out)
167