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// This file is part of par2cmdline (a PAR 2.0 compatible file verification and
// repair tool). See http://parchive.sourceforge.net for details of PAR 2.0.
//
// Copyright (c) 2003 Peter Brian Clements
//
// par2cmdline 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.
//
// par2cmdline 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 this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
#include "par2cmdline.h"
#ifdef _MSC_VER
#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif
#endif
// The one and only CCITT CRC32 lookup table
crc32table ccitttable(0xEDB88320L);
// Construct the CRC32 lookup table from the specified polynomial
void GenerateCRC32Table(u32 polynomial, u32 (&table)[256])
{
for (u32 i = 0; i <= 255 ; i++)
{
u32 crc = i;
for (u32 j = 0; j < 8; j++)
{
crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
}
table[i] = crc;
}
}
// Construct a CRC32 lookup table for windowing
void GenerateWindowTable(u64 window, u32 (&target)[256])
{
for (u32 i=0; i<=255; i++)
{
u32 crc = ccitttable.table[i];
for (u64 j=0; j<window; j++)
{
crc = ((crc >> 8) & 0x00ffffffL) ^ ccitttable.table[(u8)crc];
}
target[i] = crc;
}
}
// Construct the mask value to apply to the CRC when windowing
u32 ComputeWindowMask(u64 window)
{
u32 result = ~0;
while (window > 0)
{
result = CRCUpdateChar(result, (char)0);
window--;
}
result ^= ~0;
return result;
}
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