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OS/2 Shareware BBS: 6 File
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06-File.zip
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fst03f.zip
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crc.c
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C/C++ Source or Header
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1996-01-09
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/* crc.c -- Compute CRCs
Copyright (c) 1995-1996 by Eberhard Mattes
This file is part of fst.
fst 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, or (at your option)
any later version.
fst 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 fst; see the file COPYING. If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <stdlib.h>
#include "crc.h"
#define CRC_POLYNOMIAL 0x4c11db7
static crc_t crc_table[256];
void crc_build_table (void)
{
int i, j;
crc_t t;
crc_table[0] = 0;
for (i = 0, j = 0; i < 128; ++i, j += 2)
{
t = crc_table[i] << 1;
if (crc_table[i] & 0x80000000)
{
crc_table[j+0] = t ^ CRC_POLYNOMIAL;
crc_table[j+1] = t;
}
else
{
crc_table[j+0] = t;
crc_table[j+1] = t ^ CRC_POLYNOMIAL;
}
}
}
crc_t crc_compute (const unsigned char *src, size_t size)
{
size_t i;
crc_t crc;
crc = ~0;
for (i = 0; i < size; ++i)
crc = (crc << 8) ^ crc_table[(crc >> 24) ^ src[i]];
return ~crc;
}