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Add an incremental checksum update routine. Perhaps some i386 assembly

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guru out there can find a way to take advantage of little-endianness to
make this computation more efficient.  (I am certain that it can be done,
but haven't managed to make it work myself.)
This commit is contained in:
Garrett Wollman 1996-05-23 20:11:48 +00:00
parent 2f833c17e4
commit f66e235a13
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=15884
1 changed files with 17 additions and 1 deletions
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18
sys/i386/include/in_cksum.h
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@ -33,7 +33,7 @@
* from tahoe: in_cksum.c 1.2 86/01/05
* from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91
* from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
* $Id$
* $Id: in_cksum.h,v 1.1 1996/04/18 15:39:27 wollman Exp $
*/
#ifndef _MACHINE_IN_CKSUM_H_
@ -69,8 +69,24 @@ in_cksum_hdr(const struct ip *ip)
return ~sum & 0xffff;
}
static __inline void
in_cksum_update(struct ip *ip)
{
int __tmpsum;
__tmpsum = (int)ntohs(ip->ip_sum) + 256;
ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16));
}
#else
u_int in_cksum_hdr __P((const struct ip *));
#define in_cksum_update(ip) \
do { \
int __tmpsum; \
__tmpsum = (int)ntohs(ip->ip_sum) + 256; \
ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16)); \
} while(0)
#endif
#endif /* _MACHINE_IN_CKSUM_H_ */