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/*-
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Margo Seltzer.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <db.h>
#include "hash.h"
#include "page.h"
#include "extern.h"
#ifdef notdef
static u_int32_t hash1(const void *, size_t) __unused;
static u_int32_t hash2(const void *, size_t) __unused;
static u_int32_t hash3(const void *, size_t) __unused;
#endif
static u_int32_t hash4(const void *, size_t);
/* Default hash function. */
u_int32_t (*__default_hash)(const void *, size_t) = hash4;
#ifdef notdef
/*
* Assume that we've already split the bucket to which this key hashes,
* calculate that bucket, and check that in fact we did already split it.
*
* EJB's original hsearch hash.
*/
#define PRIME1 37
#define PRIME2 1048583
u_int32_t
hash1(const void *key, size_t len)
{
u_int32_t h;
u_int8_t *k;
h = 0;
k = (u_int8_t *)key;
/* Convert string to integer */
while (len--)
h = h * PRIME1 ^ (*k++ - ' ');
h %= PRIME2;
return (h);
}
/*
* Phong Vo's linear congruential hash
*/
#define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
u_int32_t
hash2(const void *key, size_t len)
{
u_int32_t h;
u_int8_t *e, c, *k;
k = (u_int8_t *)key;
e = k + len;
for (h = 0; k != e;) {
c = *k++;
if (!c && k > e)
break;
dcharhash(h, c);
}
return (h);
}
/*
* This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
* units. On the first time through the loop we get the "leftover bytes"
* (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
* all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
* this routine is heavily used enough, it's worth the ugly coding.
*
* Ozan Yigit's original sdbm hash.
*/
u_int32_t
hash3(const void *key, size_t len)
{
u_int32_t n, loop;
u_int8_t *k;
#define HASHC n = *k++ + 65599 * n
n = 0;
k = (u_int8_t *)key;
if (len > 0) {
loop = (len + 8 - 1) >> 3;
switch (len & (8 - 1)) {
case 0:
do { /* All fall throughs */
HASHC;
case 7:
HASHC;
case 6:
HASHC;
case 5:
HASHC;
case 4:
HASHC;
case 3:
HASHC;
case 2:
HASHC;
case 1:
HASHC;
} while (--loop);
}
}
return (n);
}
#endif /* notdef */
/* Chris Torek's hash function. */
u_int32_t
hash4(const void *key, size_t len)
{
u_int32_t h, loop;
const u_int8_t *k;
#define HASH4a h = (h << 5) - h + *k++;
#define HASH4b h = (h << 5) + h + *k++;
#define HASH4 HASH4b
h = 0;
k = key;
if (len > 0) {
loop = (len + 8 - 1) >> 3;
switch (len & (8 - 1)) {
case 0:
do { /* All fall throughs */
HASH4;
case 7:
HASH4;
case 6:
HASH4;
case 5:
HASH4;
case 4:
HASH4;
case 3:
HASH4;
case 2:
HASH4;
case 1:
HASH4;
} while (--loop);
}
}
return (h);
}
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