xorn/src/python/base64.py

   1 # gaf - Python library for manipulating gEDA files
   2 #**********************************************************************
   3 #                   _     _                     __   _  _
   4 #   __ _ _ __   ___| |_  | |__   __ _ ___  ___ / /_ | or |
   5 #  / _` | '_ \ / _ \ __| | '_ \ / _` / __|/ _ \ '_ \| or |_
   6 # | (_| | | | |  __/ |_  | |_) | (_| \__ \  __/ (_) |__   _|
   7 #  \__, |_| |_|\___|\__| |_.__/ \__,_|___/\___|\___/   |_|
   8 #  |___/
   9 #
  10 #  created by Alfred Reibenschuh <alfredreibenschuh@gmx.net>,
  11 #  under the "GNU Library General Public License" (see below).
  12 #
  13 #**********************************************************************
  14 # Copyright (C) 2003 Free Software Foundation
  15 # Copyright (C) 2013-2020 Roland Lutz
  16 #
  17 # This program is free software; you can redistribute it and/or modify
  18 # it under the terms of the GNU General Public License as published by
  19 # the Free Software Foundation; either version 2 of the License, or
  20 # (at your option) any later version.
  21 #
  22 # This program is distributed in the hope that it will be useful,
  23 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  24 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  25 # GNU General Public License for more details.
  26 #
  27 # You should have received a copy of the GNU General Public License
  28 # along with this program; if not, write to the Free Software Foundation,
  29 # Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  30
  31 ## \namespace xorn.base64
  32 ## Reading and writing base64-encoded data
  33
  34 from gettext import gettext as _
  35
  36 BASE64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
  37 PAD64 = '='
  38 RANK = [
  39     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0x00-0x0f
  40     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0x10-0x1f
  41     255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63, # 0x20-0x2f
  42      52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,255,255,255, # 0x30-0x3f
  43     255,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, # 0x40-0x4f
  44      15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255, # 0x50-0x5f
  45     255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, # 0x60-0x6f
  46      41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255, # 0x70-0x7f
  47     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0x80-0x8f
  48     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0x90-0x9f
  49     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0xa0-0xaf
  50     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0xb0-0xbf
  51     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0xc0-0xcf
  52     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0xd0-0xdf
  53     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0xe0-0xef
  54     255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, # 0xf0-0xff
  55 ]
  56
  57 ## Write a binary string to a file in %base64 representation.
  58 #
  59 # If \a columns is not \c None, insert a newline every \a columns
  60 # characters.  This is required by RFC 2045, but some applications
  61 # don't require it.  \a columns must positive and a multiple of \c 4.
  62 #
  63 # If \a delim is not \c None, it is written on a separate line after
  64 # the data.  This argument is provided for symmetry with \ref decode.
  65 #
  66 # \return \c None.
  67
  68 def encode(f, src, columns = 72, delim = None):
  69     # bulk encoding
  70     blen = len(src) - len(src) % 3
  71     ocnt = 0
  72
  73     for pos in xrange(0, blen, 3):
  74         # Convert 3 bytes of src to 4 bytes of output
  75         #
  76         # output[0] = input[0] 7:2
  77         # output[1] = input[0] 1:0 input[1] 7:4
  78         # output[2] = input[1] 3:0 input[2] 7:6
  79         # output[3] = input[1] 5:0
  80
  81         i0, i1, i2 = [ord(ch) for ch in src[pos:pos + 3]]
  82
  83         # Map output to the Base64 alphabet
  84         f.write(BASE64[i0 >> 2] +
  85                 BASE64[((i0 & 0x03) << 4) + (i1 >> 4)] +
  86                 BASE64[((i1 & 0x0f) << 2) + (i2 >> 6)] +
  87                 BASE64[i2 & 0x3f])
  88
  89         if columns is not None:
  90             ocnt += 1
  91             if ocnt % (columns / 4) == 0 and pos != len(src) - 3:
  92                 f.write('\n')
  93
  94     # Now worry about padding with remaining 1 or 2 bytes
  95     if blen != len(src):
  96         i0 = ord(src[blen])
  97         if blen == len(src) - 1:
  98             i1 = 0
  99         else:
 100             i1 = ord(src[blen + 1])
 101         i2 = 0
 102
 103         f.write(BASE64[i0 >> 2] +
 104                 BASE64[((i0 & 0x03) << 4) + (i1 >> 4)])
 105         if blen == len(src) - 1:
 106             f.write(PAD64)
 107         else:
 108             f.write(BASE64[((i1 & 0x0f) << 2) + (i2 >> 6)])
 109         f.write(PAD64)
 110
 111     if src:
 112         f.write('\n')
 113
 114     if delim is not None:
 115         f.write(delim + '\n')
 116
 117 ## Raised when reading invalid or unterminated base64-encoded data.
 118
 119 class DecodingError(Exception):
 120     pass
 121
 122 ## Read a string in %base64 representation from a file.
 123 #
 124 # This function is liberal in what it will accept.  It ignores
 125 # non-base64 symbols.
 126 #
 127 # If \a delim is \c None, read until the end of the file.  If \a delim
 128 # is not \c None, read until a line containing exactly \a delim is
 129 # found.
 130 #
 131 # \return A string containing the decoded data.
 132 #
 133 # \throw DecodingError if reading something that is not valid
 134 #                      base64-encoded data
 135 # \throw DecodingError if the end of the file is hit and \a delim is
 136 #                      not \c None
 137
 138 def decode(f, delim = None):
 139     ch = 0
 140     state = 0
 141     res = 0
 142     dst = []
 143     pad = 0
 144
 145     while True:
 146       try:
 147         line = f.next()
 148       except StopIteration:
 149         if delim is not None:
 150           raise DecodingError, _("Unexpected end-of-file")
 151         break
 152
 153       if delim is not None and line == delim + '\n':
 154         break
 155
 156       for ch in line:
 157         if ch == PAD64:
 158             pad += 1
 159             continue
 160         pos = RANK[ord(ch)]
 161         if pos == 255:
 162             # Skip any non-base64 anywhere
 163             continue
 164         if pad != 0:
 165             raise DecodingError
 166
 167         if state == 0:
 168             dst += [pos << 2]
 169             state = 1
 170         elif state == 1:
 171             dst[-1] |= pos >> 4
 172             res = (pos & 0x0f) << 4
 173             state = 2
 174         elif state == 2:
 175             dst += [res | (pos >> 2)]
 176             res = (pos & 0x03) << 6
 177             state = 3
 178         elif state == 3:
 179             dst += [res | pos]
 180             state = 0
 181
 182     # We are done decoding Base-64 chars.  Let's see if we ended
 183     # on a byte boundary, and/or with erroneous trailing characters.
 184     if pad != 0:
 185         # We got a pad char.
 186         if state == 0:
 187             # Invalid = in first position
 188             raise DecodingError
 189         elif state == 1:
 190             # Invalid = in second position
 191             raise DecodingError
 192         elif state == 2:
 193             # Valid, means one byte of info
 194             # Make sure there is another trailing = sign.
 195             if pad != 2:
 196                 raise DecodingError
 197         elif state == 3:
 198             # Valid, means two bytes of info
 199             # We know this char is an =.  Is there anything but
 200             # whitespace after it?
 201             if pad != 1:
 202                 raise DecodingError
 203         if state == 2 or state == 3:
 204             # Now make sure for cases 2 and 3 that the "extra"
 205             # bits that slopped past the last full byte were
 206             # zeros.  If we don't check them, they become a
 207             # subliminal channel.
 208             if res != 0:
 209                 raise DecodingError
 210     else:
 211         # We ended by seeing the end of the string.  Make sure we
 212         # have no partial bytes lying around.
 213         if state != 0:
 214             raise DecodingError
 215     return ''.join(chr(b) for b in dst)