mirror of https://github.com/VLSIDA/OpenRAM.git
43 lines
1.6 KiB
Python
43 lines
1.6 KiB
Python
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# -*- coding: ISO-8859-1 -*-
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#
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#
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# Copyright (C) 2005-2006 Andr<64> Wobst <wobsta@users.sourceforge.net>
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#
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# This file is part of PyX (http://pyx.sourceforge.net/).
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#
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# PyX is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# PyX is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with PyX; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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import array
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c1 = 52845
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c1_16, c1_8 = divmod(c1, 0x100) # to avoid overflow (or conversion to the slow long integers)
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c2 = 22719
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def decoder(code, r, n):
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plain = array.array("B")
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for x in array.array("B", code):
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plain.append(x ^ (r >> 8))
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# r = ((x + r) * c1 + c2) & 0xffff # this might overflow
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r = ((((x + r) * c1_16) & 0xff) * 0x100 + (x + r) * c1_8 + c2) & 0xffff
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return plain.tostring()[n:]
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def encoder(data, r, random):
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code = array.array("B")
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for x in array.array("B", random+data):
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code.append(x ^ (r>>8))
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# r = ((code[-1] + r) * c1 + c2) & 0xffff # this might overflow
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r = ((((code[-1] + r) * c1_16) & 0xff) * 0x100 + (code[-1] + r) * c1_8 + c2) & 0xffff
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return code.tostring()
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