/* * Copyright (c) 2003 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this * file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_LICENSE_HEADER_END@ */ /*- * 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) static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94"; #endif /* LIBC_SCCS and not lint */ #include <sys/cdefs.h> #include <sys/types.h> #include <db.h> #include "hash.h" #include "page.h" #include "extern.h" static u_int32_t hash1(const void *, size_t) ; static u_int32_t hash2(const void *, size_t) ; static u_int32_t hash3(const void *, size_t) ; static u_int32_t hash4(const void *, size_t); /* Global default hash function */ u_int32_t (*__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 static u_int32_t hash1(keyarg, len) const void *keyarg; size_t len; { const u_char *key; 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; { const u_char *e, *key; u_int32_t h; 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; size_t len; { const u_char *key; size_t loop; 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; size_t len; { const u_char *key; size_t loop; 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); }