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77 lines
1.9 KiB
C++
77 lines
1.9 KiB
C++
////////////////////////////////////////////////////////////////////////////////////////
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//
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// Nestopia - NES/Famicom emulator written in C++
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//
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// Copyright (C) 2003-2008 Martin Freij
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//
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// This file is part of Nestopia.
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//
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// Nestopia 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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// Nestopia 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 Nestopia; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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//
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////////////////////////////////////////////////////////////////////////////////////////
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#include "NstCore.hpp"
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#include "NstCrc32.hpp"
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namespace Nes
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{
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namespace Core
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{
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namespace Crc32
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{
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static dword NST_CALL Iterate(uint data,dword crc)
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{
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struct Lut
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{
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dword data[256];
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Lut()
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{
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for (uint i=0; i < 256; ++i)
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{
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dword n = i;
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for (uint j=0; j < 8; ++j)
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n = (n >> 1) ^ (((~n & 1) - 1) & 0xEDB88320);
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data[i] = n;
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}
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}
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};
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static const Lut lut;
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return (crc >> 8) ^ lut.data[(crc ^ data) & 0xFF];
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}
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dword NST_CALL Compute(uint data,dword crc)
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{
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return Iterate( data, crc ^ 0xFFFFFFFF ) ^ 0xFFFFFFFF;
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}
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dword NST_CALL Compute(const byte* NST_RESTRICT data,const dword length,dword crc)
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{
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crc ^= 0xFFFFFFFF;
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for (const byte* const end=data+length; data != end; ++data)
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crc = Iterate( *data, crc );
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crc ^= 0xFFFFFFFF;
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return crc;
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}
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}
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}
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}
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