Date: Wed, 15 Nov 2000 03:11:31 -0800 From: Julian Elischer <julian@elischer.org> To: Ruslan Ermilov <ru@FreeBSD.ORG> Cc: Charles Mott <cmott@scientech.com>, Archie Cobbs <archie@dellroad.org>, net@FreeBSD.ORG, Ari Suutari <ari@suutari.iki.fi> Subject: Re: libalias: Incremental Update of Internet Checksum Message-ID: <3A126F63.8EB0D49@elischer.org> References: <Pine.BSF.4.21.0011122254240.50684-100000@carcassonne.scientech.com> <Pine.BSF.4.21.0011130015100.50906-100000@carcassonne.scientech.com> <20001113103852.E34671@sunbay.com>
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Ruslan Ermilov wrote:
>
Here's the version I wrote some years ago..
#define FIXSUM16(c, op, np)
\
do {
\
(c) -= (u_int16_t) ~*((u_int16_t *) (op));
\
if ((c) < 0) {
\
(c) += 0xffff;
\
}
\
(c) -= (u_int16_t) *((u_int16_t *) (np));
\
if ((c) < 0) {
\
(c) += 0xffff;
\
}
\
} while (0)
it replaces the 16 bit word at *op with the new value at *np and updates
the
checksum c
--
__--_|\ Julian Elischer
/ \ julian@elischer.org
( OZ ) World tour 2000
---> X_.---._/ presently in: Budapest
v
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