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/* $Id: hash.c,v 1.3 2019/02/13 05:41:35 tb Exp $ */
/*
* Copyright (c) 2019 Kristaps Dzonsons <kristaps@bsd.lv>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <assert.h>
#include <endian.h>
#include <stdint.h>
#include <stdlib.h>
#include <openssl/md4.h>
#include "extern.h"
/*
* A fast 32-bit hash.
* Described in Tridgell's "Efficient Algorithms for Sorting and
* Synchronization" thesis and the "Rolling checksum" document.
*/
uint32_t
hash_fast(const void *buf, size_t len)
{
size_t i = 0;
uint32_t a = 0, /* part of a(k, l) */
b = 0; /* b(k, l) */
const signed char *dat = buf;
if (len > 4)
for ( ; i < len - 4; i += 4) {
b += 4 * (a + dat[i]) +
3 * dat[i + 1] +
2 * dat[i + 2] +
dat[i + 3];
a += dat[i + 0] +
dat[i + 1] +
dat[i + 2] +
dat[i + 3];
}
for ( ; i < len; i++) {
a += dat[i];
b += a;
}
/* s(k, l) = (eps % M) + 2^16 b(k, l) % M */
return (a & 0xffff) + (b << 16);
}
/*
* Slow MD4-based hash with trailing seed.
*/
void
hash_slow(const void *buf, size_t len,
unsigned char *md, const struct sess *sess)
{
MD4_CTX ctx;
int32_t seed = htole32(sess->seed);
MD4_Init(&ctx);
MD4_Update(&ctx, buf, len);
MD4_Update(&ctx, (unsigned char *)&seed, sizeof(int32_t));
MD4_Final(md, &ctx);
}
/*
* Hash an entire file.
* This is similar to hash_slow() except the seed is hashed at the end
* of the sequence, not the beginning.
*/
void
hash_file(const void *buf, size_t len,
unsigned char *md, const struct sess *sess)
{
MD4_CTX ctx;
int32_t seed = htole32(sess->seed);
MD4_Init(&ctx);
MD4_Update(&ctx, (unsigned char *)&seed, sizeof(int32_t));
MD4_Update(&ctx, buf, len);
MD4_Final(md, &ctx);
}
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