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