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/*
* $OpenBSD: chksum.c,v 1.1 1997/01/16 09:26:50 niklas Exp $
* $NetBSD: chksum.c,v 1.1.1.1 1996/11/29 23:36:30 is Exp $
*
* Copyright (c) 1996 Ignatios Souvatzis
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Ignatios Souvatzis
* for the NetBSD project.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include "chksum.h"
u_int32_t
chksum(block, size)
u_int32_t *block;
int size;
{
u_int32_t sum, lastsum;
int i;
sum = 0;
for (i=0; i<size; i++) {
lastsum = sum;
sum += block[i];
if (sum < lastsum)
++sum;
}
return sum;
}
#ifdef TESTSUM
u_int32_t myblock[8192];
int
main(int argc, char *argb[]) {
int bbsize;
u_int32_t cks, cks1;
bbsize=atol(argb[1]);
bbsize *= (512 / sizeof (u_int32_t));
if (4*bbsize != read(0, myblock, sizeof(u_int32_t)*bbsize)) {
fprintf(stderr, "short read\n");
exit(1);
}
fprintf(stderr, "Cksum field = 0x%x, ", myblock[1]);
cks = chksum(myblock, bbsize);
fprintf(stderr, "cksum = 0x%x\n", cks);
myblock[1] += 0xFFFFFFFF - cks;
fprintf(stderr, "New cksum field = 0x%x, ", myblock[1]);
cks1 = chksum(myblock, bbsize);
fprintf(stderr, "cksum = 0x%x\n", cks1);
}
#endif
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