1 /* $NetBSD: hash.c,v 1.60 2020/12/30 10:03:16 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 1.60 2020/12/30 10:03:16 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 /* Remove everything from the hash table and frees up the memory. */ 146 void 147 HashTable_Done(HashTable *t) 148 { 149 HashEntry **buckets = t->buckets; 150 size_t i, n = t->bucketsSize; 151 152 for (i = 0; i < n; i++) { 153 HashEntry *he = buckets[i]; 154 while (he != NULL) { 155 HashEntry *next = he->next; 156 free(he); 157 he = next; 158 } 159 } 160 free(t->buckets); 161 162 #ifdef CLEANUP 163 t->buckets = NULL; 164 #endif 165 } 166 167 /* Find the entry corresponding to the key, or return NULL. */ 168 HashEntry * 169 HashTable_FindEntry(HashTable *t, const char *key) 170 { 171 unsigned int h = hash(key, NULL); 172 return HashTable_Find(t, h, key); 173 } 174 175 /* Find the value corresponding to the key, or return NULL. */ 176 void * 177 HashTable_FindValue(HashTable *t, const char *key) 178 { 179 HashEntry *he = HashTable_FindEntry(t, key); 180 return he != NULL ? he->value : NULL; 181 } 182 183 /* 184 * Find the value corresponding to the key and the precomputed hash, 185 * or return NULL. 186 */ 187 void * 188 HashTable_FindValueHash(HashTable *t, const char *key, unsigned int h) 189 { 190 HashEntry *he = HashTable_Find(t, h, key); 191 return he != NULL ? he->value : NULL; 192 } 193 194 /* 195 * Make the hash table larger. Any bucket numbers from the old table become 196 * invalid; the hash codes stay valid though. 197 */ 198 static void 199 HashTable_Enlarge(HashTable *t) 200 { 201 unsigned int oldSize = t->bucketsSize; 202 HashEntry **oldBuckets = t->buckets; 203 unsigned int newSize = 2 * oldSize; 204 unsigned int newMask = newSize - 1; 205 HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize); 206 size_t i; 207 208 for (i = 0; i < newSize; i++) 209 newBuckets[i] = NULL; 210 211 for (i = 0; i < oldSize; i++) { 212 HashEntry *he = oldBuckets[i]; 213 while (he != NULL) { 214 HashEntry *next = he->next; 215 he->next = newBuckets[he->key_hash & newMask]; 216 newBuckets[he->key_hash & newMask] = he; 217 he = next; 218 } 219 } 220 221 free(oldBuckets); 222 223 t->bucketsSize = newSize; 224 t->bucketsMask = newMask; 225 t->buckets = newBuckets; 226 DEBUG5(HASH, "%s: %p size=%d entries=%d maxchain=%d\n", 227 __func__, t, t->bucketsSize, t->numEntries, t->maxchain); 228 t->maxchain = 0; 229 } 230 231 /* 232 * Find or create an entry corresponding to the key. 233 * Return in out_isNew whether a new entry has been created. 234 */ 235 HashEntry * 236 HashTable_CreateEntry(HashTable *t, const char *key, Boolean *out_isNew) 237 { 238 size_t keylen; 239 unsigned int h = hash(key, &keylen); 240 HashEntry *he = HashTable_Find(t, h, key); 241 242 if (he != NULL) { 243 if (out_isNew != NULL) 244 *out_isNew = FALSE; 245 return he; 246 } 247 248 if (t->numEntries >= rebuildLimit * t->bucketsSize) 249 HashTable_Enlarge(t); 250 251 he = bmake_malloc(sizeof *he + keylen); 252 he->value = NULL; 253 he->key_hash = h; 254 memcpy(he->key, key, keylen + 1); 255 256 he->next = t->buckets[h & t->bucketsMask]; 257 t->buckets[h & t->bucketsMask] = he; 258 t->numEntries++; 259 260 if (out_isNew != NULL) 261 *out_isNew = TRUE; 262 return he; 263 } 264 265 HashEntry * 266 HashTable_Set(HashTable *t, const char *key, void *value) 267 { 268 HashEntry *he = HashTable_CreateEntry(t, key, NULL); 269 HashEntry_Set(he, value); 270 return he; 271 } 272 273 /* Delete the entry from the table and free the associated memory. */ 274 void 275 HashTable_DeleteEntry(HashTable *t, HashEntry *he) 276 { 277 HashEntry **ref = &t->buckets[he->key_hash & t->bucketsMask]; 278 HashEntry *p; 279 280 for (; (p = *ref) != NULL; ref = &p->next) { 281 if (p == he) { 282 *ref = p->next; 283 free(p); 284 t->numEntries--; 285 return; 286 } 287 } 288 abort(); 289 } 290 291 /* Set things up for iterating over all entries in the hash table. */ 292 void 293 HashIter_Init(HashIter *hi, HashTable *t) 294 { 295 hi->table = t; 296 hi->nextBucket = 0; 297 hi->entry = NULL; 298 } 299 300 /* 301 * Return the next entry in the hash table, or NULL if the end of the table 302 * is reached. 303 */ 304 HashEntry * 305 HashIter_Next(HashIter *hi) 306 { 307 HashTable *t = hi->table; 308 HashEntry *he = hi->entry; 309 HashEntry **buckets = t->buckets; 310 unsigned int bucketsSize = t->bucketsSize; 311 312 if (he != NULL) 313 he = he->next; /* skip the most recently returned entry */ 314 315 while (he == NULL) { /* find the next nonempty chain */ 316 if (hi->nextBucket >= bucketsSize) 317 return NULL; 318 he = buckets[hi->nextBucket++]; 319 } 320 hi->entry = he; 321 return he; 322 } 323 324 void 325 HashTable_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