| /*- |
| * 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. ***REMOVED*** - see |
| * ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change |
| * 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 */ |
| |
| #ifndef macintosh |
| #include <sys/types.h> |
| #endif |
| #include "mcom_db.h" |
| #include "hash.h" |
| #include "page.h" |
| /* #include "extern.h" */ |
| |
| #if 0 |
| static uint32 hash1(const void *, size_t); |
| static uint32 hash2(const void *, size_t); |
| static uint32 hash3(const void *, size_t); |
| #endif |
| static uint32 hash4(const void *, size_t); |
| |
| /* Global default hash function */ |
| uint32 (*__default_hash)(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 |
| |
| #if 0 |
| static uint32 |
| hash1(const void *keyarg, register size_t len) |
| { |
| register const uint8 *key; |
| register uint32 h; |
| |
| /* Convert string to integer */ |
| for (key = (const uint8 *)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 uint32 |
| hash2(const void *keyarg, size_t len) |
| { |
| register const uint8 *e, *key; |
| register uint32 h; |
| register uint8 c; |
| |
| key = (const uint8 *)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 uint32 |
| hash3(const void *keyarg, register size_t len) |
| { |
| register const uint8 *key; |
| register size_t loop; |
| register uint32 h; |
| |
| #define HASHC h = *key++ + 65599 * h |
| |
| h = 0; |
| key = (const uint8 *)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); |
| } |
| #endif /* 0 */ |
| |
| /* Hash function from Chris Torek. */ |
| static uint32 |
| hash4(const void *keyarg, register size_t len) |
| { |
| register const uint8 *key; |
| register size_t loop; |
| register uint32 h; |
| |
| #define HASH4a h = (h << 5) - h + *key++; |
| #define HASH4b h = (h << 5) + h + *key++; |
| #define HASH4 HASH4b |
| |
| h = 0; |
| key = (const uint8 *)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); |
| } |