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/* $NetBSD: hash_func.c,v 1.5 1995/02/27 13:22:27 cgd Exp $ */
/*-
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 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)
#if 0
static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94";
#else
static char rcsid[] = "$NetBSD: hash_func.c,v 1.5 1995/02/27 13:22:27 cgd Exp $";
#endif
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <db.h>
#include "hash.h"
#include "page.h"
#include "extern.h"
static u_int32_t hash1 __P((const void *, size_t));
static u_int32_t hash2 __P((const void *, size_t));
static u_int32_t hash3 __P((const void *, size_t));
static u_int32_t hash4 __P((const void *, size_t));
/* Global default hash function */
u_int32_t (*__default_hash) __P((const void *, size_t)) = hash4;
/*
* HASH FUNCTIONS
*
* 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.
*
* This came from ejb's hsearch.
*/
#define PRIME1 37
#define PRIME2 1048583
static u_int32_t
hash1(keyarg, len)
const void *keyarg;
register size_t len;
{
register const u_char *key;
register u_int32_t h;
/* Convert string to integer */
for (key = keyarg, h = 0; len--;)
h = h * PRIME1 ^ (*key++ - ' ');
h %= PRIME2;
return (h);
}
/*
* Phong's linear congruential hash
*/
#define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
static u_int32_t
hash2(keyarg, len)
const void *keyarg;
size_t len;
{
register const u_char *e, *key;
register u_int32_t h;
register u_char c;
key = keyarg;
e = key + len;
for (h = 0; key != e;) {
c = *key++;
if (!c && key > 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.
*
* OZ's original sdbm hash
*/
static u_int32_t
hash3(keyarg, len)
const void *keyarg;
register size_t len;
{
register const u_char *key;
register size_t loop;
register u_int32_t h;
#define HASHC h = *key++ + 65599 * h
h = 0;
key = keyarg;
if (len > 0) {
loop = (len + 8 - 1) >> 3;
switch (len & (8 - 1)) {
case 0:
do {
HASHC;
/* FALLTHROUGH */
case 7:
HASHC;
/* FALLTHROUGH */
case 6:
HASHC;
/* FALLTHROUGH */
case 5:
HASHC;
/* FALLTHROUGH */
case 4:
HASHC;
/* FALLTHROUGH */
case 3:
HASHC;
/* FALLTHROUGH */
case 2:
HASHC;
/* FALLTHROUGH */
case 1:
HASHC;
} while (--loop);
}
}
return (h);
}
/* Hash function from Chris Torek. */
static u_int32_t
hash4(keyarg, len)
const void *keyarg;
register size_t len;
{
register const u_char *key;
register size_t loop;
register u_int32_t h;
#define HASH4a h = (h << 5) - h + *key++;
#define HASH4b h = (h << 5) + h + *key++;
#define HASH4 HASH4b
h = 0;
key = keyarg;
if (len > 0) {
loop = (len + 8 - 1) >> 3;
switch (len & (8 - 1)) {
case 0:
do {
HASH4;
/* FALLTHROUGH */
case 7:
HASH4;
/* FALLTHROUGH */
case 6:
HASH4;
/* FALLTHROUGH */
case 5:
HASH4;
/* FALLTHROUGH */
case 4:
HASH4;
/* FALLTHROUGH */
case 3:
HASH4;
/* FALLTHROUGH */
case 2:
HASH4;
/* FALLTHROUGH */
case 1:
HASH4;
} while (--loop);
}
}
return (h);
}
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