1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Margo Seltzer. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #if defined(LIBC_SCCS) && !defined(lint) 36 static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94"; 37 #endif /* LIBC_SCCS and not lint */ 38 #include <sys/types.h> 39 40 #include <db.h> 41 #include "hash.h" 42 #include "page.h" 43 #include "extern.h" 44 45 #ifdef notdef 46 static u_int32_t hash1(const void *, size_t) __unused; 47 static u_int32_t hash2(const void *, size_t) __unused; 48 static u_int32_t hash3(const void *, size_t) __unused; 49 #endif 50 static u_int32_t hash4(const void *, size_t); 51 52 /* Default hash function. */ 53 u_int32_t (*__default_hash)(const void *, size_t) = hash4; 54 55 #ifdef notdef 56 /* 57 * Assume that we've already split the bucket to which this key hashes, 58 * calculate that bucket, and check that in fact we did already split it. 59 * 60 * EJB's original hsearch hash. 61 */ 62 #define PRIME1 37 63 #define PRIME2 1048583 64 65 u_int32_t 66 hash1(const void *key, size_t len) 67 { 68 u_int32_t h; 69 u_int8_t *k; 70 71 h = 0; 72 k = (u_int8_t *)key; 73 /* Convert string to integer */ 74 while (len--) 75 h = h * PRIME1 ^ (*k++ - ' '); 76 h %= PRIME2; 77 return (h); 78 } 79 80 /* 81 * Phong Vo's linear congruential hash 82 */ 83 #define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c)) 84 85 u_int32_t 86 hash2(const void *key, size_t len) 87 { 88 u_int32_t h; 89 u_int8_t *e, c, *k; 90 91 k = (u_int8_t *)key; 92 e = k + len; 93 for (h = 0; k != e;) { 94 c = *k++; 95 if (!c && k > e) 96 break; 97 dcharhash(h, c); 98 } 99 return (h); 100 } 101 102 /* 103 * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte 104 * units. On the first time through the loop we get the "leftover bytes" 105 * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle 106 * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If 107 * this routine is heavily used enough, it's worth the ugly coding. 108 * 109 * Ozan Yigit's original sdbm hash. 110 */ 111 u_int32_t 112 hash3(const void *key, size_t len) 113 { 114 u_int32_t n, loop; 115 u_int8_t *k; 116 117 #define HASHC n = *k++ + 65599 * n 118 119 n = 0; 120 k = (u_int8_t *)key; 121 if (len > 0) { 122 loop = (len + 8 - 1) >> 3; 123 124 switch (len & (8 - 1)) { 125 case 0: 126 do { /* All fall throughs */ 127 HASHC; 128 case 7: 129 HASHC; 130 case 6: 131 HASHC; 132 case 5: 133 HASHC; 134 case 4: 135 HASHC; 136 case 3: 137 HASHC; 138 case 2: 139 HASHC; 140 case 1: 141 HASHC; 142 } while (--loop); 143 } 144 145 } 146 return (n); 147 } 148 #endif /* notdef */ 149 150 /* Chris Torek's hash function. */ 151 u_int32_t 152 hash4(const void *key, size_t len) 153 { 154 u_int32_t h, loop; 155 const u_int8_t *k; 156 157 #define HASH4a h = (h << 5) - h + *k++; 158 #define HASH4b h = (h << 5) + h + *k++; 159 #define HASH4 HASH4b 160 161 h = 0; 162 k = key; 163 if (len > 0) { 164 loop = (len + 8 - 1) >> 3; 165 166 switch (len & (8 - 1)) { 167 case 0: 168 do { /* All fall throughs */ 169 HASH4; 170 case 7: 171 HASH4; 172 case 6: 173 HASH4; 174 case 5: 175 HASH4; 176 case 4: 177 HASH4; 178 case 3: 179 HASH4; 180 case 2: 181 HASH4; 182 case 1: 183 HASH4; 184 } while (--loop); 185 } 186 187 } 188 return (h); 189 } 190