hash.c revision 1.47
1 /* $NetBSD: hash.c,v 1.47 2020/10/18 12:47:43 rillig Exp $ */ 2 3 /* 4 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Adam de Boor. 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 /* 36 * Copyright (c) 1988, 1989 by Adam de Boor 37 * Copyright (c) 1989 by Berkeley Softworks 38 * All rights reserved. 39 * 40 * This code is derived from software contributed to Berkeley by 41 * Adam de Boor. 42 * 43 * Redistribution and use in source and binary forms, with or without 44 * modification, are permitted provided that the following conditions 45 * are met: 46 * 1. Redistributions of source code must retain the above copyright 47 * notice, this list of conditions and the following disclaimer. 48 * 2. Redistributions in binary form must reproduce the above copyright 49 * notice, this list of conditions and the following disclaimer in the 50 * documentation and/or other materials provided with the distribution. 51 * 3. All advertising materials mentioning features or use of this software 52 * must display the following acknowledgement: 53 * This product includes software developed by the University of 54 * California, Berkeley and its contributors. 55 * 4. Neither the name of the University nor the names of its contributors 56 * may be used to endorse or promote products derived from this software 57 * without specific prior written permission. 58 * 59 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 62 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 69 * SUCH DAMAGE. 70 */ 71 72 /* 73 * This module contains routines to manipulate a hash table. 74 * See hash.h for a definition of the structure of the hash 75 * table. Hash tables grow automatically as the amount of 76 * information increases. 77 */ 78 79 #include "make.h" 80 81 /* "@(#)hash.c 8.1 (Berkeley) 6/6/93" */ 82 MAKE_RCSID("$NetBSD: hash.c,v 1.47 2020/10/18 12:47:43 rillig Exp $"); 83 84 /* 85 * The ratio of # entries to # buckets at which we rebuild the table to 86 * make it larger. 87 */ 88 #define rebuildLimit 3 89 90 /* This hash function matches Gosling's emacs. */ 91 static unsigned int 92 hash(const char *key, size_t *out_keylen) 93 { 94 unsigned h = 0; 95 const char *p = key; 96 while (*p != '\0') 97 h = (h << 5) - h + (unsigned char)*p++; 98 if (out_keylen != NULL) 99 *out_keylen = (size_t)(p - key); 100 return h; 101 } 102 103 static HashEntry * 104 HashTable_Find(HashTable *t, unsigned int h, const char *key) 105 { 106 HashEntry *e; 107 unsigned int chainlen = 0; 108 109 #ifdef DEBUG_HASH_LOOKUP 110 DEBUG4(HASH, "%s: %p h=%x key=%s\n", __func__, t, h, key); 111 #endif 112 113 for (e = t->buckets[h & t->bucketsMask]; e != NULL; e = e->next) { 114 chainlen++; 115 if (e->key_hash == h && strcmp(e->key, key) == 0) 116 break; 117 } 118 119 if (chainlen > t->maxchain) 120 t->maxchain = chainlen; 121 122 return e; 123 } 124 125 /* Sets up the hash table. */ 126 void 127 Hash_InitTable(HashTable *t) 128 { 129 unsigned int n = 16, i; 130 HashEntry **hp; 131 132 t->numEntries = 0; 133 t->maxchain = 0; 134 t->bucketsSize = n; 135 t->bucketsMask = n - 1; 136 t->buckets = hp = bmake_malloc(sizeof(*hp) * n); 137 for (i = 0; i < n; i++) 138 hp[i] = NULL; 139 } 140 141 /* Removes everything from the hash table and frees up the memory space it 142 * occupied (except for the space in the HashTable structure). */ 143 void 144 Hash_DeleteTable(HashTable *t) 145 { 146 HashEntry **hp, *h, *nexth = NULL; 147 int i; 148 149 for (hp = t->buckets, i = (int)t->bucketsSize; --i >= 0;) { 150 for (h = *hp++; h != NULL; h = nexth) { 151 nexth = h->next; 152 free(h); 153 } 154 } 155 free(t->buckets); 156 157 /* 158 * Set up the hash table to cause memory faults on any future access 159 * attempts until re-initialization. 160 */ 161 t->buckets = NULL; 162 } 163 164 /* Searches the hash table for an entry corresponding to the key. 165 * 166 * Input: 167 * t Hash table to search. 168 * key A hash key. 169 * 170 * Results: 171 * Returns a pointer to the entry for key, or NULL if the table contains 172 * no entry for the key. 173 */ 174 HashEntry * 175 Hash_FindEntry(HashTable *t, const char *key) 176 { 177 unsigned int h = hash(key, NULL); 178 return HashTable_Find(t, h, key); 179 } 180 181 void * 182 Hash_FindValue(HashTable *t, const char *key) 183 { 184 HashEntry *he = Hash_FindEntry(t, key); 185 return he != NULL ? he->value : NULL; 186 } 187 188 /* Makes a new hash table that is larger than the old one. The entire hash 189 * table is moved, so any bucket numbers from the old table become invalid. */ 190 static void 191 RebuildTable(HashTable *t) 192 { 193 HashEntry *e, *next = NULL, **hp, **xp; 194 int i; 195 unsigned int mask, oldsize, newsize; 196 HashEntry **oldhp; 197 198 oldhp = t->buckets; 199 oldsize = t->bucketsSize; 200 newsize = oldsize << 1; 201 t->bucketsSize = (unsigned int)newsize; 202 t->bucketsMask = mask = newsize - 1; 203 t->buckets = hp = bmake_malloc(sizeof(*hp) * newsize); 204 i = (int)newsize; 205 while (--i >= 0) 206 *hp++ = NULL; 207 for (hp = oldhp, i = (int)oldsize; --i >= 0;) { 208 for (e = *hp++; e != NULL; e = next) { 209 next = e->next; 210 xp = &t->buckets[e->key_hash & mask]; 211 e->next = *xp; 212 *xp = e; 213 } 214 } 215 free(oldhp); 216 DEBUG5(HASH, "%s: %p size=%d entries=%d maxchain=%d\n", 217 __func__, t, t->bucketsSize, t->numEntries, t->maxchain); 218 t->maxchain = 0; 219 } 220 221 /* Searches the hash table for an entry corresponding to the key. 222 * If no entry is found, then one is created. 223 * 224 * Input: 225 * t Hash table to search. 226 * key A hash key. 227 * newPtr Filled with TRUE if new entry created, 228 * FALSE otherwise. 229 */ 230 HashEntry * 231 Hash_CreateEntry(HashTable *t, const char *key, Boolean *newPtr) 232 { 233 HashEntry *e; 234 unsigned h; 235 size_t keylen; 236 HashEntry **hp; 237 238 h = hash(key, &keylen); 239 e = HashTable_Find(t, h, key); 240 if (e) { 241 if (newPtr != NULL) 242 *newPtr = FALSE; 243 return e; 244 } 245 246 /* 247 * The desired entry isn't there. Before allocating a new entry, 248 * expand the table if necessary (and this changes the resulting 249 * bucket chain). 250 */ 251 if (t->numEntries >= rebuildLimit * t->bucketsSize) 252 RebuildTable(t); 253 254 e = bmake_malloc(sizeof(*e) + keylen); 255 hp = &t->buckets[h & t->bucketsMask]; 256 e->next = *hp; 257 *hp = e; 258 Hash_SetValue(e, NULL); 259 e->key_hash = h; 260 memcpy(e->key, key, keylen + 1); 261 t->numEntries++; 262 263 if (newPtr != NULL) 264 *newPtr = TRUE; 265 return e; 266 } 267 268 /* Delete the given hash table entry and free memory associated with it. */ 269 void 270 Hash_DeleteEntry(HashTable *t, HashEntry *e) 271 { 272 HashEntry **hp, *p; 273 274 for (hp = &t->buckets[e->key_hash & t->bucketsMask]; 275 (p = *hp) != NULL; hp = &p->next) { 276 if (p == e) { 277 *hp = p->next; 278 free(p); 279 t->numEntries--; 280 return; 281 } 282 } 283 abort(); 284 } 285 286 /* Set things up for iterating over all entries in the hash table. */ 287 void 288 HashIter_Init(HashIter *hi, HashTable *t) 289 { 290 hi->table = t; 291 hi->nextBucket = 0; 292 hi->entry = NULL; 293 } 294 295 /* Return the next entry in the hash table, or NULL if the end of the table 296 * is reached. */ 297 HashEntry * 298 HashIter_Next(HashIter *hi) 299 { 300 HashEntry *e; 301 HashTable *t = hi->table; 302 303 /* 304 * The entry field points to the most recently returned 305 * entry, or is NULL if we are starting up. If not NULL, we have 306 * to start at the next one in the chain. 307 */ 308 e = hi->entry; 309 if (e != NULL) 310 e = e->next; 311 /* 312 * If the chain ran out, or if we are starting up, we need to 313 * find the next nonempty chain. 314 */ 315 while (e == NULL) { 316 if (hi->nextBucket >= t->bucketsSize) 317 return NULL; 318 e = t->buckets[hi->nextBucket++]; 319 } 320 hi->entry = e; 321 return e; 322 } 323 324 void 325 Hash_DebugStats(HashTable *t, const char *name) 326 { 327 DEBUG4(HASH, "HashTable %s: size=%u numEntries=%u maxchain=%u\n", 328 name, t->bucketsSize, t->numEntries, t->maxchain); 329 } 330
Indexes created Mon Oct 20 20:10:13 GMT 2025