1 /* $NetBSD: hash.c,v 1.61 2021/02/01 17:32:10 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 /* Hash tables with string keys. */ 73 74 #include "make.h" 75 76 /* "@(#)hash.c 8.1 (Berkeley) 6/6/93" */ 77 MAKE_RCSID("$NetBSD: hash.c,v 1.61 2021/02/01 17:32:10 rillig Exp $"); 78 79 /* 80 * The ratio of # entries to # buckets at which we rebuild the table to 81 * make it larger. 82 */ 83 #define rebuildLimit 3 84 85 /* This hash function matches Gosling's Emacs and java.lang.String. */ 86 static unsigned int 87 hash(const char *key, size_t *out_keylen) 88 { 89 unsigned int h; 90 const char *p; 91 92 h = 0; 93 for (p = key; *p != '\0'; p++) 94 h = 31 * h + (unsigned char)*p; 95 96 if (out_keylen != NULL) 97 *out_keylen = (size_t)(p - key); 98 return h; 99 } 100 101 unsigned int 102 Hash_Hash(const char *key) 103 { 104 return hash(key, NULL); 105 } 106 107 static HashEntry * 108 HashTable_Find(HashTable *t, unsigned int h, const char *key) 109 { 110 HashEntry *e; 111 unsigned int chainlen = 0; 112 113 #ifdef DEBUG_HASH_LOOKUP 114 DEBUG4(HASH, "%s: %p h=%08x key=%s\n", __func__, t, h, key); 115 #endif 116 117 for (e = t->buckets[h & t->bucketsMask]; e != NULL; e = e->next) { 118 chainlen++; 119 if (e->key_hash == h && strcmp(e->key, key) == 0) 120 break; 121 } 122 123 if (chainlen > t->maxchain) 124 t->maxchain = chainlen; 125 126 return e; 127 } 128 129 /* Set up the hash table. */ 130 void 131 HashTable_Init(HashTable *t) 132 { 133 unsigned int n = 16, i; 134 HashEntry **buckets = bmake_malloc(sizeof *buckets * n); 135 for (i = 0; i < n; i++) 136 buckets[i] = NULL; 137 138 t->buckets = buckets; 139 t->bucketsSize = n; 140 t->numEntries = 0; 141 t->bucketsMask = n - 1; 142 t->maxchain = 0; 143 } 144 145 /* 146 * Remove everything from the hash table and free up the memory for the keys 147 * of the hash table, but not for the values associated to these keys. 148 */ 149 void 150 HashTable_Done(HashTable *t) 151 { 152 HashEntry **buckets = t->buckets; 153 size_t i, n = t->bucketsSize; 154 155 for (i = 0; i < n; i++) { 156 HashEntry *he = buckets[i]; 157 while (he != NULL) { 158 HashEntry *next = he->next; 159 free(he); 160 he = next; 161 } 162 } 163 164 free(t->buckets); 165 #ifdef CLEANUP 166 t->buckets = NULL; 167 #endif 168 } 169 170 /* Find the entry corresponding to the key, or return NULL. */ 171 HashEntry * 172 HashTable_FindEntry(HashTable *t, const char *key) 173 { 174 unsigned int h = hash(key, NULL); 175 return HashTable_Find(t, h, key); 176 } 177 178 /* Find the value corresponding to the key, or return NULL. */ 179 void * 180 HashTable_FindValue(HashTable *t, const char *key) 181 { 182 HashEntry *he = HashTable_FindEntry(t, key); 183 return he != NULL ? he->value : NULL; 184 } 185 186 /* 187 * Find the value corresponding to the key and the precomputed hash, 188 * or return NULL. 189 */ 190 void * 191 HashTable_FindValueHash(HashTable *t, const char *key, unsigned int h) 192 { 193 HashEntry *he = HashTable_Find(t, h, key); 194 return he != NULL ? he->value : NULL; 195 } 196 197 /* 198 * Make the hash table larger. Any bucket numbers from the old table become 199 * invalid; the hash codes stay valid though. 200 */ 201 static void 202 HashTable_Enlarge(HashTable *t) 203 { 204 unsigned int oldSize = t->bucketsSize; 205 HashEntry **oldBuckets = t->buckets; 206 unsigned int newSize = 2 * oldSize; 207 unsigned int newMask = newSize - 1; 208 HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize); 209 size_t i; 210 211 for (i = 0; i < newSize; i++) 212 newBuckets[i] = NULL; 213 214 for (i = 0; i < oldSize; i++) { 215 HashEntry *he = oldBuckets[i]; 216 while (he != NULL) { 217 HashEntry *next = he->next; 218 he->next = newBuckets[he->key_hash & newMask]; 219 newBuckets[he->key_hash & newMask] = he; 220 he = next; 221 } 222 } 223 224 free(oldBuckets); 225 226 t->bucketsSize = newSize; 227 t->bucketsMask = newMask; 228 t->buckets = newBuckets; 229 DEBUG5(HASH, "%s: %p size=%d entries=%d maxchain=%d\n", 230 __func__, t, t->bucketsSize, t->numEntries, t->maxchain); 231 t->maxchain = 0; 232 } 233 234 /* 235 * Find or create an entry corresponding to the key. 236 * Return in out_isNew whether a new entry has been created. 237 */ 238 HashEntry * 239 HashTable_CreateEntry(HashTable *t, const char *key, Boolean *out_isNew) 240 { 241 size_t keylen; 242 unsigned int h = hash(key, &keylen); 243 HashEntry *he = HashTable_Find(t, h, key); 244 245 if (he != NULL) { 246 if (out_isNew != NULL) 247 *out_isNew = FALSE; 248 return he; 249 } 250 251 if (t->numEntries >= rebuildLimit * t->bucketsSize) 252 HashTable_Enlarge(t); 253 254 he = bmake_malloc(sizeof *he + keylen); 255 he->value = NULL; 256 he->key_hash = h; 257 memcpy(he->key, key, keylen + 1); 258 259 he->next = t->buckets[h & t->bucketsMask]; 260 t->buckets[h & t->bucketsMask] = he; 261 t->numEntries++; 262 263 if (out_isNew != NULL) 264 *out_isNew = TRUE; 265 return he; 266 } 267 268 HashEntry * 269 HashTable_Set(HashTable *t, const char *key, void *value) 270 { 271 HashEntry *he = HashTable_CreateEntry(t, key, NULL); 272 HashEntry_Set(he, value); 273 return he; 274 } 275 276 /* Delete the entry from the table and free the associated memory. */ 277 void 278 HashTable_DeleteEntry(HashTable *t, HashEntry *he) 279 { 280 HashEntry **ref = &t->buckets[he->key_hash & t->bucketsMask]; 281 HashEntry *p; 282 283 for (; (p = *ref) != NULL; ref = &p->next) { 284 if (p == he) { 285 *ref = p->next; 286 free(p); 287 t->numEntries--; 288 return; 289 } 290 } 291 abort(); 292 } 293 294 /* Set things up for iterating over all entries in the hash table. */ 295 void 296 HashIter_Init(HashIter *hi, HashTable *t) 297 { 298 hi->table = t; 299 hi->nextBucket = 0; 300 hi->entry = NULL; 301 } 302 303 /* 304 * Return the next entry in the hash table, or NULL if the end of the table 305 * is reached. 306 */ 307 HashEntry * 308 HashIter_Next(HashIter *hi) 309 { 310 HashTable *t = hi->table; 311 HashEntry *he = hi->entry; 312 HashEntry **buckets = t->buckets; 313 unsigned int bucketsSize = t->bucketsSize; 314 315 if (he != NULL) 316 he = he->next; /* skip the most recently returned entry */ 317 318 while (he == NULL) { /* find the next nonempty chain */ 319 if (hi->nextBucket >= bucketsSize) 320 return NULL; 321 he = buckets[hi->nextBucket++]; 322 } 323 hi->entry = he; 324 return he; 325 } 326 327 void 328 HashTable_DebugStats(HashTable *t, const char *name) 329 { 330 DEBUG4(HASH, "HashTable %s: size=%u numEntries=%u maxchain=%u\n", 331 name, t->bucketsSize, t->numEntries, t->maxchain); 332 } 333