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/* $OpenBSD: in_cksum.c,v 1.2 1996/09/23 14:18:55 mickey Exp $ */
/* $NetBSD: in_cksum.c,v 1.3 1995/04/22 13:53:48 cgd Exp $ */
/*
* Copyright (c) 1992 Regents of the University of California.
* All rights reserved.
*
* This software was developed by the Computer Systems Engineering group
* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
* contributed to Berkeley.
*
* 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 the University of
* California, Lawrence Berkeley Laboratory and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
*
* @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL)
*/
#include <sys/types.h>
/*
* Checksum routine for Internet Protocol family headers.
* This routine is very heavily used in the network
* code and should be modified for each CPU to be as fast as possible.
* In particular, it should not be this one.
*/
int
in_cksum(p, len)
register void *p;
register int len;
{
register int sum = 0, oddbyte = 0, v = 0;
register u_char *cp = p;
/* we assume < 2^16 bytes being summed */
while (len > 0) {
if (oddbyte) {
sum += v + *cp++;
len--;
}
if (((long)cp & 1) == 0) {
while ((len -= 2) >= 0) {
sum += *(u_short *)cp;
cp += 2;
}
} else {
while ((len -= 2) >= 0) {
sum += *cp++ << 8;
sum += *cp++;
}
}
if ((oddbyte = len & 1) != 0)
v = *cp << 8;
}
if (oddbyte)
sum += v;
sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
sum += sum >> 16; /* add potential last carry */
return (0xffff & ~sum);
}
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