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# -*- encoding: utf-8 -*-
#
#
# Copyright (C) 2005-2006 André Wobst <wobsta@pyx-project.org>
#
# This file is part of PyX (https://pyx-project.org/).
#
# PyX is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# PyX is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with PyX; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
import array
c1 = 52845
c1_16, c1_8 = divmod(c1, 0x100) # to avoid overflow (or conversion to the slow long integers)
c2 = 22719
def decoder(code, r, n):
plain = array.array("B")
for x in array.array("B", code):
plain.append(x ^ (r >> 8))
# r = ((x + r) * c1 + c2) & 0xffff # this might overflow
r = ((((x + r) * c1_16) & 0xff) * 0x100 + (x + r) * c1_8 + c2) & 0xffff
return plain.tobytes()[n:]
def encoder(data, r, random):
code = array.array("B")
for x in array.array("B", random+data):
code.append(x ^ (r>>8))
# r = ((code[-1] + r) * c1 + c2) & 0xffff # this might overflow
r = ((((code[-1] + r) * c1_16) & 0xff) * 0x100 + (code[-1] + r) * c1_8 + c2) & 0xffff
return code.tobytes()
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