1 /* $NetBSD: hash_func.c,v 1.13 2008/09/10 17:52:35 joerg Exp $ */ 2 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 HAVE_NBTOOL_CONFIG_H 36 #include "nbtool_config.h" 37 #endif 38 39 #include <sys/cdefs.h> 40 __RCSID("$NetBSD: hash_func.c,v 1.13 2008/09/10 17:52:35 joerg Exp $"); 41 42 #include <sys/types.h> 43 44 #include <db.h> 45 #include "hash.h" 46 #include "page.h" 47 #include "extern.h" 48 49 #if 0 50 static uint32_t hash1(const void *, size_t) __attribute__((__unused__)); 51 static uint32_t hash2(const void *, size_t) __attribute__((__unused__)); 52 static uint32_t hash3(const void *, size_t) __attribute__((__unused__)); 53 #endif 54 static uint32_t hash4(const void *, size_t) __attribute__((__unused__)); 55 56 /* Global default hash function */ 57 uint32_t (*__default_hash)(const void *, size_t) = hash4; 58 #if 0 59 /* 60 * HASH FUNCTIONS 61 * 62 * Assume that we've already split the bucket to which this key hashes, 63 * calculate that bucket, and check that in fact we did already split it. 64 * 65 * This came from ejb's hsearch. 66 */ 67 68 #define PRIME1 37 69 #define PRIME2 1048583 70 71 static uint32_t 72 hash1(const void *keyarg, size_t len) 73 { 74 const uint8_t *key; 75 uint32_t h; 76 77 /* Convert string to integer */ 78 for (key = keyarg, h = 0; len--;) 79 h = h * PRIME1 ^ (*key++ - ' '); 80 h %= PRIME2; 81 return (h); 82 } 83 84 /* 85 * Phong's linear congruential hash 86 */ 87 #define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c)) 88 89 static uint32_t 90 hash2(const void *keyarg, size_t len) 91 { 92 const uint8_t *e, *key; 93 uint32_t h; 94 uint8_t c; 95 96 key = keyarg; 97 e = key + len; 98 for (h = 0; key != e;) { 99 c = *key++; 100 if (!c && key > e) 101 break; 102 dcharhash(h, c); 103 } 104 return (h); 105 } 106 107 /* 108 * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte 109 * units. On the first time through the loop we get the "leftover bytes" 110 * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle 111 * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If 112 * this routine is heavily used enough, it's worth the ugly coding. 113 * 114 * OZ's original sdbm hash 115 */ 116 static uint32_t 117 hash3(const void *keyarg, size_t len) 118 { 119 const uint8_t *key; 120 size_t loop; 121 uint32_t h; 122 123 #define HASHC h = *key++ + 65599 * h 124 125 h = 0; 126 key = keyarg; 127 if (len > 0) { 128 loop = (len + 8 - 1) >> 3; 129 130 switch (len & (8 - 1)) { 131 case 0: 132 do { 133 HASHC; 134 /* FALLTHROUGH */ 135 case 7: 136 HASHC; 137 /* FALLTHROUGH */ 138 case 6: 139 HASHC; 140 /* FALLTHROUGH */ 141 case 5: 142 HASHC; 143 /* FALLTHROUGH */ 144 case 4: 145 HASHC; 146 /* FALLTHROUGH */ 147 case 3: 148 HASHC; 149 /* FALLTHROUGH */ 150 case 2: 151 HASHC; 152 /* FALLTHROUGH */ 153 case 1: 154 HASHC; 155 } while (--loop); 156 } 157 } 158 return (h); 159 } 160 #endif 161 162 /* Hash function from Chris Torek. */ 163 static uint32_t 164 hash4(const void *keyarg, size_t len) 165 { 166 const uint8_t *key; 167 size_t loop; 168 uint32_t h; 169 170 #define HASH4a h = (h << 5) - h + *key++; 171 #define HASH4b h = (h << 5) + h + *key++; 172 #define HASH4 HASH4b 173 174 h = 0; 175 key = keyarg; 176 if (len > 0) { 177 loop = (len + 8 - 1) >> 3; 178 179 switch (len & (8 - 1)) { 180 case 0: 181 do { 182 HASH4; 183 /* FALLTHROUGH */ 184 case 7: 185 HASH4; 186 /* FALLTHROUGH */ 187 case 6: 188 HASH4; 189 /* FALLTHROUGH */ 190 case 5: 191 HASH4; 192 /* FALLTHROUGH */ 193 case 4: 194 HASH4; 195 /* FALLTHROUGH */ 196 case 3: 197 HASH4; 198 /* FALLTHROUGH */ 199 case 2: 200 HASH4; 201 /* FALLTHROUGH */ 202 case 1: 203 HASH4; 204 } while (--loop); 205 } 206 } 207 return (h); 208 } 209
Indexes created Tue Sep 23 07:09:52 GMT 2025