9fc74a871c
This does not include the new hash routines since they will cause problems when reading old hash files. Since mpool(3) has been changed, provide a compatibility shim for older binaries. Obtained from: OpenBSD
191 lines
4.5 KiB
C
191 lines
4.5 KiB
C
/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Margo Seltzer.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <db.h>
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#include "hash.h"
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#include "page.h"
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#include "extern.h"
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#ifdef notdef
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static u_int32_t hash1(const void *, size_t) __unused;
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static u_int32_t hash2(const void *, size_t) __unused;
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static u_int32_t hash3(const void *, size_t) __unused;
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#endif
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static u_int32_t hash4(const void *, size_t);
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/* Default hash function. */
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u_int32_t (*__default_hash)(const void *, size_t) = hash4;
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#ifdef notdef
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/*
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* Assume that we've already split the bucket to which this key hashes,
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* calculate that bucket, and check that in fact we did already split it.
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*
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* EJB's original hsearch hash.
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*/
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#define PRIME1 37
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#define PRIME2 1048583
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u_int32_t
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hash1(const void *key, size_t len)
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{
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u_int32_t h;
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u_int8_t *k;
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h = 0;
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k = (u_int8_t *)key;
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/* Convert string to integer */
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while (len--)
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h = h * PRIME1 ^ (*k++ - ' ');
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h %= PRIME2;
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return (h);
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}
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/*
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* Phong Vo's linear congruential hash
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*/
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#define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
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u_int32_t
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hash2(const void *key, size_t len)
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{
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u_int32_t h;
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u_int8_t *e, c, *k;
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k = (u_int8_t *)key;
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e = k + len;
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for (h = 0; k != e;) {
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c = *k++;
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if (!c && k > e)
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break;
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dcharhash(h, c);
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}
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return (h);
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}
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/*
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* This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
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* units. On the first time through the loop we get the "leftover bytes"
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* (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
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* all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
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* this routine is heavily used enough, it's worth the ugly coding.
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*
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* Ozan Yigit's original sdbm hash.
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*/
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u_int32_t
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hash3(const void *key, size_t len)
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{
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u_int32_t n, loop;
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u_int8_t *k;
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#define HASHC n = *k++ + 65599 * n
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n = 0;
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k = (u_int8_t *)key;
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if (len > 0) {
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loop = (len + 8 - 1) >> 3;
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switch (len & (8 - 1)) {
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case 0:
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do { /* All fall throughs */
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HASHC;
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case 7:
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HASHC;
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case 6:
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HASHC;
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case 5:
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HASHC;
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case 4:
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HASHC;
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case 3:
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HASHC;
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case 2:
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HASHC;
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case 1:
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HASHC;
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} while (--loop);
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}
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}
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return (n);
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}
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#endif /* notdef */
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/* Chris Torek's hash function. */
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u_int32_t
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hash4(const void *key, size_t len)
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{
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u_int32_t h, loop;
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const u_int8_t *k;
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#define HASH4a h = (h << 5) - h + *k++;
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#define HASH4b h = (h << 5) + h + *k++;
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#define HASH4 HASH4b
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h = 0;
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k = key;
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if (len > 0) {
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loop = (len + 8 - 1) >> 3;
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switch (len & (8 - 1)) {
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case 0:
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do { /* All fall throughs */
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HASH4;
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case 7:
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HASH4;
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case 6:
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HASH4;
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case 5:
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HASH4;
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case 4:
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HASH4;
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case 3:
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HASH4;
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case 2:
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HASH4;
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case 1:
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HASH4;
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} while (--loop);
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}
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}
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return (h);
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}
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