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/* -*- c-file-style: "bsd" -*-
*
* $Id: checksum.c,v 1.24 2000/08/06 12:50:36 mbp Exp $
*
* Copyright (C) 1999, 2000 by Martin Pool <mbp@humbug.org.au>
* Copyright (C) 1996 by Andrew Tridgell
* Copyright (C) 1996 by Paul Mackerras
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "includes.h"
/* XXX: I think this is obsolete. */
int checksum_seed = 0;
/*
* A simple 32 bit checksum that can be updated from either end
* (inspired by Mark Adler's Adler-32 checksum)
*/
uint32_t _hs_calc_weak_sum(byte_t const *buf1, int len)
{
int i;
uint32_t s1, s2;
int8_t const *buf = (int8_t const *) buf1; /* this is signed */
s1 = s2 = 0;
for (i = 0; i < (len - 4); i += 4) {
s2 += 4 * (s1 + buf[i]) + 3 * buf[i + 1] +
2 * buf[i + 2] + buf[i + 3] + 10 * CHAR_OFFSET;
s1 += (buf[i + 0] + buf[i + 1] + buf[i + 2] + buf[i + 3] +
4 * CHAR_OFFSET);
}
for (; i < len; i++) {
s1 += (buf[i] + CHAR_OFFSET);
s2 += s1;
}
return (s1 & 0xffff) + (s2 << 16);
}
/*
* Calculate and store into SUM a strong MD4 checksum of the file
* blocks seen so far.
*
* The checksum is perturbed by a seed value. This is used when
* retrying a failed transmission: we've discovered that the hashes
* collided at some point, so we're going to try again with different
* hashes to see if we can get it right. (Check tridge's thesis for
* details and to see if that's correct.)
*
* Since we can't retry a web transaction I'm not sure if it's very
* useful in rproxy.
*/
uint32_t
_hs_calc_strong_sum(byte_t const *buf,
size_t len,
byte_t *sum,
size_t sum_len)
{
hs_mdfour_t m;
byte_t tsum[MD4_LENGTH];
hs_mdfour_begin(&m);
hs_mdfour_update(&m, buf, len);
hs_mdfour_result(&m, tsum);
memcpy(sum, tsum, sum_len);
return 0;
}
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