File:
[DVB] /
multiplexer /
crc16.c
Revision
1.1:
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Thu Oct 28 21:08:18 2004 UTC (19 years, 7 months ago) by
oskar
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CVS tags:
version-1-1-1,
version-1-1-0,
version-1-0-8,
version-1-0-7,
version-1-0-6,
version-1-0-5,
version-1-0-4,
version-1-0-3,
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devide crc stuff into crc16 and crc32 files
/*
* cyclic redundancy check 16 bit
* Copyright (C) 1999 Christian Wolff, 2004 Oskar Schirmer
* for Convergence Integrated Media GmbH (http://www.convergence.de)
*
* This program 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.
*
* This program 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <sys/types.h>
#include "crc16.h"
u_int16_t crc_16_table[256];
// generate the tables of CRC-16 remainders for all possible bytes
void gen_crc16_table() {
register int i,j;
register u_int16_t crc16;
for (i=0; i<256; i++) {
crc16=(u_int16_t)i << 8;
for (j=0; j<8; j++) {
crc16 = (crc16 << 1) ^ ((crc16 & (1<<15)) ? POLYNOMIAL_16_MSBF : 0);
}
crc_16_table[i]=crc16;
}
}
// update the CRC on the data block one byte at a time
u_int16_t update_crc_16_block(u_int16_t crc, char *data_block_ptr, int data_block_size)
{
register int i;
for (i=data_block_size; i>0; i--)
crc=update_crc_16(crc, *data_block_ptr++);
return crc;
}
void crc16_calc (char *data,
int size,
char *crc)
{
u_int16_t c;
c = CRC_INIT_16;
while (--size >= 0) {
c = update_crc_16 (c,*data++);
}
crc[1] = c; c >>= 8;
crc[0] = c;
}
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