util/protolib.py

   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
  74 import gzip
  75 import struct
  76
  77 def 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
 101 def _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
 131 def 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
 146 def _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
 160 def 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)