util/protolib.py

   1 #!/usr/bin/env python3
   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 # This file is a library of commonly used functions used when interfacing
  68 # with protobuf python messages. For eg, the decode scripts for different
  69 # types of proto objects can use the same function to decode a single message
  70
  71 import gzip
  72 import struct
  73
  74 def openFileRd(in_file):
  75     """
  76     This opens the file passed as argument for reading using an appropriate
  77     function depending on if it is gzipped or not. It returns the file
  78     handle.
  79     """
  80     try:
  81         # First see if this file is gzipped
  82         try:
  83             # Opening the file works even if it is not a gzip file
  84             proto_in = gzip.open(in_file, 'rb')
  85
  86             # Force a check of the magic number by seeking in the
  87             # file. If we do not do it here the error will occur when
  88             # reading the first message.
  89             proto_in.seek(1)
  90             proto_in.seek(0)
  91         except IOError:
  92             proto_in = open(in_file, 'rb')
  93     except IOError:
  94         print("Failed to open ", in_file, " for reading")
  95         exit(-1)
  96     return proto_in
  97
  98 def _DecodeVarint32(in_file):
  99     """
 100     The decoding of the Varint32 is copied from
 101     google.protobuf.internal.decoder and is only repeated here to
 102     avoid depending on the internal functions in the library. If the
 103     end of file is reached, return (0, 0).
 104     """
 105     result = 0
 106     shift = 0
 107     pos = 0
 108     # Use a 32-bit mask
 109     mask = 0xffffffff
 110     while 1:
 111         c = in_file.read(1)
 112         if len(c) == 0:
 113             return (0, 0)
 114         b = struct.unpack('<B', c)[0]
 115         result |= ((b & 0x7f) << shift)
 116         pos += 1
 117         if not (b & 0x80):
 118             if result > 0x7fffffffffffffff:
 119                 result -= (1 << 64)
 120                 result |= ~mask
 121             else:
 122                 result &= mask
 123             return (result, pos)
 124         shift += 7
 125         if shift >= 64:
 126             raise IOError('Too many bytes when decoding varint.')
 127
 128 def decodeMessage(in_file, message):
 129     """
 130     Attempt to read a message from the file and decode it. Return
 131     False if no message could be read.
 132     """
 133     try:
 134         size, pos = _DecodeVarint32(in_file)
 135         if size == 0:
 136             return False
 137         buf = in_file.read(size)
 138         message.ParseFromString(buf)
 139         return True
 140     except IOError:
 141         return False
 142
 143 def _EncodeVarint32(out_file, value):
 144   """
 145   The encoding of the Varint32 is copied from
 146   google.protobuf.internal.encoder and is only repeated here to
 147   avoid depending on the internal functions in the library.
 148   """
 149   bits = value & 0x7f
 150   value >>= 7
 151   while value:
 152     out_file.write(struct.pack('<B', 0x80 | bits))
 153     bits = value & 0x7f
 154     value >>= 7
 155   out_file.write(struct.pack('<B', bits))
 156
 157 def encodeMessage(out_file, message):
 158     """
 159     Encoded a message with the length prepended as a 32-bit varint.
 160     """
 161     out = message.SerializeToString()
 162     _EncodeVarint32(out_file, len(out))
 163     out_file.write(out)