pyx/font/t1code.py

   1 # -*- encoding: utf-8 -*-
   2 #
   3 #
   4 # Copyright (C) 2005-2006 André Wobst <wobsta@users.sourceforge.net>
   5 #
   6 # This file is part of PyX (http://pyx.sourceforge.net/).
   7 #
   8 # PyX is free software; you can redistribute it and/or modify
   9 # it under the terms of the GNU General Public License as published by
  10 # the Free Software Foundation; either version 2 of the License, or
  11 # (at your option) any later version.
  12 #
  13 # PyX is distributed in the hope that it will be useful,
  14 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 # GNU General Public License for more details.
  17 #
  18 # You should have received a copy of the GNU General Public License
  19 # along with PyX; if not, write to the Free Software
  20 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  21
  22 import array
  23
  24 c1 = 52845
  25 c1_16, c1_8 = divmod(c1, 0x100) # to avoid overflow (or conversion to the slow long integers)
  26 c2 = 22719
  27
  28 def decoder(code, r, n):
  29     plain = array.array("B")
  30     for x in array.array("B", code):
  31         plain.append(x ^ (r >> 8))
  32         # r = ((x + r) * c1 + c2) & 0xffff # this might overflow
  33         r = ((((x + r) * c1_16) & 0xff) * 0x100 + (x + r) * c1_8 + c2) & 0xffff
  34     return plain.tobytes()[n:]
  35
  36 def encoder(data, r, random):
  37     code = array.array("B")
  38     for x in array.array("B", random+data):
  39         code.append(x ^ (r>>8))
  40         # r = ((code[-1] + r) * c1 + c2) & 0xffff # this might overflow
  41         r = ((((code[-1] + r) * c1_16) & 0xff) * 0x100 + (code[-1] + r) * c1_8 + c2) & 0xffff
  42     return code.tobytes()