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/*
* Copyright (c) 1998-2006 The TCPDUMP project
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code
* distributions retain the above copyright notice and this paragraph
* in its entirety, and (2) distributions including binary code include
* the above copyright notice and this paragraph in its entirety in
* the documentation or other materials provided with the distribution.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND
* WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
* LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE.
*
* miscellaneous checksumming routines
*
* Original code by Hannes Gredler (hannes@juniper.net)
*/
#ifndef lint
static const char rcsid[] _U_ =
"@(#) $Header: /tcpdump/master/tcpdump/checksum.c,v 1.2 2006-02-09 20:35:38 hannes Exp $";
#endif
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <tcpdump-stdinc.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "interface.h"
#include "extract.h"
#include "addrtoname.h"
#define CRC10_POLYNOMIAL 0x633
static u_int16_t crc10_table[256];
static void
init_crc10_table(void)
{
register int i, j;
register u_int16_t accum;
for ( i = 0; i < 256; i++ )
{
accum = ((unsigned short) i << 2);
for ( j = 0; j < 8; j++ )
{
if ((accum <<= 1) & 0x400) accum ^= CRC10_POLYNOMIAL;
}
crc10_table[i] = accum;
}
return;
}
u_int16_t
verify_crc10_cksum(u_int16_t accum, const u_char *p, int length)
{
register int i;
for ( i = 0; i < length; i++ )
{
accum = ((accum << 8) & 0x3ff)
^ crc10_table[( accum >> 2) & 0xff]
^ *p++;
}
return accum;
}
/* precompute checksum tables */
void
init_checksum(void) {
init_crc10_table();
}
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