85 lines
2.6 KiB
C
85 lines
2.6 KiB
C
/*
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* $NetBSD: chksum.c,v 1.1 1997/01/21 18:26:12 is Exp $
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*
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* Copyright (c) 1996 Ignatios Souvatzis
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Ignatios Souvatzis
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* for the NetBSD project.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include "chksum.h"
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u_int32_t
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chksum(block, size)
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u_int32_t *block;
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int size;
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{
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u_int32_t sum, lastsum;
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int i;
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sum = 0;
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for (i=0; i<size; i++) {
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lastsum = sum;
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sum += block[i];
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if (sum < lastsum)
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++sum;
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}
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return sum;
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}
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#ifdef TESTSUM
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u_int32_t myblock[8192];
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int
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main(int argc, char *argb[]) {
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int bbsize;
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u_int32_t cks, cks1;
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bbsize=atol(argb[1]);
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bbsize *= (512 / sizeof (u_int32_t));
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if (4*bbsize != read(0, myblock, sizeof(u_int32_t)*bbsize)) {
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fprintf(stderr, "short read\n");
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exit(1);
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}
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fprintf(stderr, "Cksum field = 0x%x, ", myblock[1]);
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cks = chksum(myblock, bbsize);
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fprintf(stderr, "cksum = 0x%x\n", cks);
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myblock[1] += 0xFFFFFFFF - cks;
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fprintf(stderr, "New cksum field = 0x%x, ", myblock[1]);
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cks1 = chksum(myblock, bbsize);
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fprintf(stderr, "cksum = 0x%x\n", cks1);
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}
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#endif
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