1 /* $NetBSD: hash.c,v 1.6 2009/04/11 12:41:10 lukem Exp $ */ 2 3 /* 4 * Copyright (c) 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This software was developed by the Computer Systems Engineering group 8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 9 * contributed to Berkeley. 10 * 11 * All advertising materials mentioning features or use of this software 12 * must display the following acknowledgement: 13 * This product includes software developed by the University of 14 * California, Lawrence Berkeley Laboratories. 15 * 16 * Redistribution and use in source and binary forms, with or without 17 * modification, are permitted provided that the following conditions 18 * are met: 19 * 1. Redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer. 21 * 2. Redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution. 24 * 3. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * from: @(#)hash.c 8.1 (Berkeley) 6/6/93 41 */ 42 43 #if HAVE_NBTOOL_CONFIG_H 44 #include "nbtool_config.h" 45 #endif 46 47 #include <sys/param.h> 48 #include <assert.h> 49 #include <stdlib.h> 50 #include <string.h> 51 #include <util.h> 52 #include "defs.h" 53 54 /* 55 * Interned strings are kept in a hash table. By making each string 56 * unique, the program can compare strings by comparing pointers. 57 */ 58 struct hashent { 59 // XXXLUKEM: a SIMPLEQ might be more appropriate 60 TAILQ_ENTRY(hashent) h_next; 61 const char *h_name; /* the string */ 62 u_int h_hash; /* its hash value */ 63 void *h_value; /* other values (for name=value) */ 64 }; 65 struct hashtab { 66 size_t ht_size; /* size (power of 2) */ 67 u_int ht_mask; /* == ht_size - 1 */ 68 u_int ht_used; /* number of entries used */ 69 u_int ht_lim; /* when to expand */ 70 TAILQ_HEAD(hashenthead, hashent) *ht_tab; 71 }; 72 73 static struct hashtab strings; 74 75 /* 76 * HASHFRACTION controls ht_lim, which in turn controls the average chain 77 * length. We allow a few entries, on average, as comparing them is usually 78 * cheap (the h_hash values prevent a strcmp). 79 */ 80 #define HASHFRACTION(sz) ((sz) * 3 / 2) 81 82 static void ht_expand(struct hashtab *); 83 static void ht_init(struct hashtab *, size_t); 84 static inline u_int hash(const char *); 85 static inline struct hashent *newhashent(const char *, u_int); 86 87 /* 88 * Initialize a new hash table. The size must be a power of 2. 89 */ 90 static void 91 ht_init(struct hashtab *ht, size_t sz) 92 { 93 u_int n; 94 95 ht->ht_tab = emalloc(sz * sizeof (ht->ht_tab[0])); 96 ht->ht_size = sz; 97 ht->ht_mask = sz - 1; 98 for (n = 0; n < sz; n++) 99 TAILQ_INIT(&ht->ht_tab[n]); 100 ht->ht_used = 0; 101 ht->ht_lim = HASHFRACTION(sz); 102 } 103 104 /* 105 * Expand an existing hash table. 106 */ 107 static void 108 ht_expand(struct hashtab *ht) 109 { 110 struct hashenthead *h, *oldh; 111 struct hashent *p; 112 u_int n, i; 113 114 n = ht->ht_size * 2; 115 h = emalloc(n * sizeof *h); 116 for (i = 0; i < n; i++) 117 TAILQ_INIT(&h[i]); 118 oldh = ht->ht_tab; 119 n--; 120 for (i = 0; i < ht->ht_size; i++) { 121 while ((p = TAILQ_FIRST(&oldh[i])) != NULL) { 122 TAILQ_REMOVE(&oldh[i], p, h_next); 123 // XXXLUKEM: really should be TAILQ_INSERT_TAIL 124 TAILQ_INSERT_HEAD(&h[p->h_hash & n], p, h_next); 125 } 126 } 127 free(ht->ht_tab); 128 ht->ht_tab = h; 129 ht->ht_mask = n; 130 ht->ht_size = ++n; 131 ht->ht_lim = HASHFRACTION(n); 132 } 133 134 /* 135 * Make a new hash entry, setting its h_next to NULL. 136 * If the free list is not empty, use the first entry from there, 137 * otherwise allocate a new entry. 138 */ 139 static inline struct hashent * 140 newhashent(const char *name, u_int h) 141 { 142 struct hashent *hp; 143 144 hp = ecalloc(1, sizeof(*hp)); 145 146 hp->h_name = name; 147 hp->h_hash = h; 148 return (hp); 149 } 150 151 /* 152 * Hash a string. 153 */ 154 static inline u_int 155 hash(const char *str) 156 { 157 u_int h; 158 159 for (h = 0; *str;) 160 h = (h << 5) + h + *str++; 161 return (h); 162 } 163 164 void 165 initintern(void) 166 { 167 168 ht_init(&strings, 128); 169 } 170 171 /* 172 * Generate a single unique copy of the given string. We expect this 173 * function to be used frequently, so it should be fast. 174 */ 175 const char * 176 intern(const char *s) 177 { 178 struct hashtab *ht; 179 struct hashent *hp; 180 struct hashenthead *hpp; 181 u_int h; 182 char *p; 183 184 ht = &strings; 185 h = hash(s); 186 hpp = &ht->ht_tab[h & ht->ht_mask]; 187 TAILQ_FOREACH(hp, hpp, h_next) { 188 if (hp->h_hash == h && strcmp(hp->h_name, s) == 0) 189 return (hp->h_name); 190 } 191 p = estrdup(s); 192 hp = newhashent(p, h); 193 TAILQ_INSERT_TAIL(hpp, hp, h_next); 194 if (++ht->ht_used > ht->ht_lim) 195 ht_expand(ht); 196 return (p); 197 } 198 199 struct hashtab * 200 ht_new(void) 201 { 202 struct hashtab *ht; 203 204 ht = ecalloc(1, sizeof *ht); 205 ht_init(ht, 8); 206 return (ht); 207 } 208 209 void 210 ht_free(struct hashtab *ht) 211 { 212 size_t i; 213 struct hashent *hp; 214 struct hashenthead *hpp; 215 216 for (i = 0; i < ht->ht_size; i++) { 217 hpp = &ht->ht_tab[i]; 218 while ((hp = TAILQ_FIRST(hpp)) != NULL) { 219 TAILQ_REMOVE(hpp, hp, h_next); 220 free(hp); 221 ht->ht_used--; 222 } 223 } 224 225 assert(ht->ht_used == 0); 226 free(ht->ht_tab); 227 free(ht); 228 } 229 230 /* 231 * Insert and/or replace. 232 */ 233 int 234 ht_insrep(struct hashtab *ht, const char *nam, void *val, int replace) 235 { 236 struct hashent *hp; 237 struct hashenthead *hpp; 238 u_int h; 239 240 h = hash(nam); 241 hpp = &ht->ht_tab[h & ht->ht_mask]; 242 TAILQ_FOREACH(hp, hpp, h_next) { 243 if (hp->h_name == nam) { 244 if (replace) 245 hp->h_value = val; 246 return (1); 247 } 248 } 249 hp = newhashent(nam, h); 250 TAILQ_INSERT_TAIL(hpp, hp, h_next); 251 hp->h_value = val; 252 if (++ht->ht_used > ht->ht_lim) 253 ht_expand(ht); 254 return (0); 255 } 256 257 /* 258 * Remove. 259 */ 260 int 261 ht_remove(struct hashtab *ht, const char *name) 262 { 263 struct hashent *hp; 264 struct hashenthead *hpp; 265 u_int h; 266 267 h = hash(name); 268 hpp = &ht->ht_tab[h & ht->ht_mask]; 269 270 TAILQ_FOREACH(hp, hpp, h_next) { 271 if (hp->h_name != name) 272 continue; 273 TAILQ_REMOVE(hpp, hp, h_next); 274 275 free(hp); 276 ht->ht_used--; 277 return (0); 278 } 279 return (1); 280 } 281 282 void * 283 ht_lookup(struct hashtab *ht, const char *nam) 284 { 285 struct hashent *hp; 286 struct hashenthead *hpp; 287 u_int h; 288 289 h = hash(nam); 290 hpp = &ht->ht_tab[h & ht->ht_mask]; 291 TAILQ_FOREACH(hp, hpp, h_next) 292 if (hp->h_name == nam) 293 return (hp->h_value); 294 return (NULL); 295 } 296 297 /* 298 * first parameter to callback is the entry name from the hash table 299 * second parameter is the value from the hash table 300 * third argument is passed through from the "arg" parameter to ht_enumerate() 301 */ 302 303 int 304 ht_enumerate(struct hashtab *ht, ht_callback cbfunc, void *arg) 305 { 306 struct hashent *hp; 307 struct hashenthead *hpp; 308 size_t i; 309 int rval = 0; 310 311 for (i = 0; i < ht->ht_size; i++) { 312 hpp = &ht->ht_tab[i]; 313 TAILQ_FOREACH(hp, hpp, h_next) 314 rval += (*cbfunc)(hp->h_name, hp->h_value, arg); 315 } 316 return rval; 317 } 318