pyx/font/t1code.py

   1 #!/usr/bin/env python
   2 # -*- coding: ISO-8859-1 -*-
   3 #
   4 #
   5 # Copyright (C) 2005 André Wobst <wobsta@users.sourceforge.net>
   6 #
   7 # This file is part of PyX (http://pyx.sourceforge.net/).
   8 #
   9 # PyX is free software; you can redistribute it and/or modify
  10 # it under the terms of the GNU General Public License as published by
  11 # the Free Software Foundation; either version 2 of the License, or
  12 # (at your option) any later version.
  13 #
  14 # PyX is distributed in the hope that it will be useful,
  15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 # GNU General Public License for more details.
  18 #
  19 # You should have received a copy of the GNU General Public License
  20 # along with PyX; if not, write to the Free Software
  21 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  22
  23 import array
  24
  25 c1 = 52845
  26 c1_16, c1_8 = divmod(c1, 0x100) # to avoid overflow (or conversion to the slow long integers)
  27 c2 = 22719
  28
  29 def decoder(code, r, n):
  30     plain = array.array("B")
  31     for x in array.array("B", code):
  32         plain.append(x ^ (r >> 8))
  33         # r = ((x + r) * c1 + c2) & 0xffff # this might overflow
  34         r = ((((x + r) * c1_16) & 0xff) * 0x100 + (x + r) * c1_8 + c2) & 0xffff
  35     return plain.tostring()[n:]
  36
  37 def encoder(data, r, random):
  38     code = array.array("B")
  39     for x in array.array("B", random+data):
  40         code.append(x ^ (r>>8))
  41         # r = ((code[-1] + r) * c1 + c2) & 0xffff # this might overflow
  42         r = ((((code[-1] + r) * c1_16) & 0xff) * 0x100 + (code[-1] + r) * c1_8 + c2) & 0xffff
  43     return code.tostring()