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/*
Copyright (c) 2010 Gluster, Inc. <http://www.gluster.com>
This file is part of GlusterFS.
GlusterFS is free software; you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published
by the Free Software Foundation; either version 3 of the License,
or (at your option) any later version.
GlusterFS 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
Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see
<http://www.gnu.org/licenses/>.
*/
#include <inttypes.h>
#include "glusterfs.h"
#include "md5.h"
#include "checksum.h"
/*
* The "weak" checksum required for the rsync algorithm,
* adapted from the rsync source code. The following comment
* appears there:
*
* "a simple 32 bit checksum that can be upadted from either end
* (inspired by Mark Adler's Adler-32 checksum)"
*/
uint32_t
gf_rsync_weak_checksum (char *buf1, int32_t len)
{
int32_t i;
uint32_t s1, s2;
signed char *buf = (signed char *) buf1;
uint32_t csum;
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];
s1 += buf[i+0] + buf[i+1] + buf[i+2] + buf[i+3];
}
for (; i < len; i++) {
s1 += buf[i];
s2 += s1;
}
csum = (s1 & 0xffff) + (s2 << 16);
return csum;
}
/*
* The "strong" checksum required for the rsync algorithm,
* adapted from the rsync source code.
*/
void
gf_rsync_strong_checksum (char *buf, int32_t len, uint8_t *sum)
{
md_context m;
md5_begin (&m);
md5_update (&m, (unsigned char *) buf, len);
md5_result (&m, (unsigned char *) sum);
return;
}
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