1 /* $NetBSD: hash.c,v 1.64 2021/04/11 12:46:54 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 1.64 2021/04/11 12:46:54 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_String(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 /* This hash function matches Gosling's Emacs and java.lang.String. */ 102 unsigned int 103 Hash_Substring(Substring key) 104 { 105 unsigned int h; 106 const char *p; 107 108 h = 0; 109 for (p = key.start; p != key.end; p++) 110 h = 31 * h + (unsigned char)*p; 111 return h; 112 } 113 114 static HashEntry * 115 HashTable_Find(HashTable *t, unsigned int h, const char *key) 116 { 117 HashEntry *e; 118 unsigned int chainlen = 0; 119 120 #ifdef DEBUG_HASH_LOOKUP 121 DEBUG4(HASH, "%s: %p h=%08x key=%s\n", __func__, t, h, key); 122 #endif 123 124 for (e = t->buckets[h & t->bucketsMask]; e != NULL; e = e->next) { 125 chainlen++; 126 if (e->key_hash == h && strcmp(e->key, key) == 0) 127 break; 128 } 129 130 if (chainlen > t->maxchain) 131 t->maxchain = chainlen; 132 133 return e; 134 } 135 136 static bool 137 HashEntry_KeyEquals(const HashEntry *he, Substring key) 138 { 139 const char *heKey, *p; 140 141 heKey = he->key; 142 for (p = key.start; p != key.end; p++, heKey++) 143 if (*p != *heKey || *heKey == '\0') 144 return false; 145 return *heKey == '\0'; 146 } 147 148 static HashEntry * 149 HashTable_FindEntryBySubstring(HashTable *t, Substring key, unsigned int h) 150 { 151 HashEntry *e; 152 unsigned int chainlen = 0; 153 154 #ifdef DEBUG_HASH_LOOKUP 155 DEBUG4(HASH, "%s: %p h=%08x key=%.*s\n", __func__, t, h, 156 (int)Substring_Length(key), key.start); 157 #endif 158 159 for (e = t->buckets[h & t->bucketsMask]; e != NULL; e = e->next) { 160 chainlen++; 161 if (e->key_hash == h && HashEntry_KeyEquals(e, key)) 162 break; 163 } 164 165 if (chainlen > t->maxchain) 166 t->maxchain = chainlen; 167 168 return e; 169 } 170 171 /* Set up the hash table. */ 172 void 173 HashTable_Init(HashTable *t) 174 { 175 unsigned int n = 16, i; 176 HashEntry **buckets = bmake_malloc(sizeof *buckets * n); 177 for (i = 0; i < n; i++) 178 buckets[i] = NULL; 179 180 t->buckets = buckets; 181 t->bucketsSize = n; 182 t->numEntries = 0; 183 t->bucketsMask = n - 1; 184 t->maxchain = 0; 185 } 186 187 /* 188 * Remove everything from the hash table and free up the memory for the keys 189 * of the hash table, but not for the values associated to these keys. 190 */ 191 void 192 HashTable_Done(HashTable *t) 193 { 194 HashEntry **buckets = t->buckets; 195 size_t i, n = t->bucketsSize; 196 197 for (i = 0; i < n; i++) { 198 HashEntry *he = buckets[i]; 199 while (he != NULL) { 200 HashEntry *next = he->next; 201 free(he); 202 he = next; 203 } 204 } 205 206 free(t->buckets); 207 #ifdef CLEANUP 208 t->buckets = NULL; 209 #endif 210 } 211 212 /* Find the entry corresponding to the key, or return NULL. */ 213 HashEntry * 214 HashTable_FindEntry(HashTable *t, const char *key) 215 { 216 unsigned int h = Hash_String(key, NULL); 217 return HashTable_Find(t, h, key); 218 } 219 220 /* Find the value corresponding to the key, or return NULL. */ 221 void * 222 HashTable_FindValue(HashTable *t, const char *key) 223 { 224 HashEntry *he = HashTable_FindEntry(t, key); 225 return he != NULL ? he->value : NULL; 226 } 227 228 /* 229 * Find the value corresponding to the key and the precomputed hash, 230 * or return NULL. 231 */ 232 void * 233 HashTable_FindValueBySubstringHash(HashTable *t, Substring key, unsigned int h) 234 { 235 HashEntry *he = HashTable_FindEntryBySubstring(t, key, h); 236 return he != NULL ? he->value : NULL; 237 } 238 239 /* 240 * Make the hash table larger. Any bucket numbers from the old table become 241 * invalid; the hash codes stay valid though. 242 */ 243 static void 244 HashTable_Enlarge(HashTable *t) 245 { 246 unsigned int oldSize = t->bucketsSize; 247 HashEntry **oldBuckets = t->buckets; 248 unsigned int newSize = 2 * oldSize; 249 unsigned int newMask = newSize - 1; 250 HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize); 251 size_t i; 252 253 for (i = 0; i < newSize; i++) 254 newBuckets[i] = NULL; 255 256 for (i = 0; i < oldSize; i++) { 257 HashEntry *he = oldBuckets[i]; 258 while (he != NULL) { 259 HashEntry *next = he->next; 260 he->next = newBuckets[he->key_hash & newMask]; 261 newBuckets[he->key_hash & newMask] = he; 262 he = next; 263 } 264 } 265 266 free(oldBuckets); 267 268 t->bucketsSize = newSize; 269 t->bucketsMask = newMask; 270 t->buckets = newBuckets; 271 DEBUG5(HASH, "%s: %p size=%d entries=%d maxchain=%d\n", 272 __func__, (void *)t, t->bucketsSize, t->numEntries, t->maxchain); 273 t->maxchain = 0; 274 } 275 276 /* 277 * Find or create an entry corresponding to the key. 278 * Return in out_isNew whether a new entry has been created. 279 */ 280 HashEntry * 281 HashTable_CreateEntry(HashTable *t, const char *key, bool *out_isNew) 282 { 283 size_t keylen; 284 unsigned int h = Hash_String(key, &keylen); 285 HashEntry *he = HashTable_Find(t, h, key); 286 287 if (he != NULL) { 288 if (out_isNew != NULL) 289 *out_isNew = false; 290 return he; 291 } 292 293 if (t->numEntries >= rebuildLimit * t->bucketsSize) 294 HashTable_Enlarge(t); 295 296 he = bmake_malloc(sizeof *he + keylen); 297 he->value = NULL; 298 he->key_hash = h; 299 memcpy(he->key, key, keylen + 1); 300 301 he->next = t->buckets[h & t->bucketsMask]; 302 t->buckets[h & t->bucketsMask] = he; 303 t->numEntries++; 304 305 if (out_isNew != NULL) 306 *out_isNew = true; 307 return he; 308 } 309 310 HashEntry * 311 HashTable_Set(HashTable *t, const char *key, void *value) 312 { 313 HashEntry *he = HashTable_CreateEntry(t, key, NULL); 314 HashEntry_Set(he, value); 315 return he; 316 } 317 318 /* Delete the entry from the table and free the associated memory. */ 319 void 320 HashTable_DeleteEntry(HashTable *t, HashEntry *he) 321 { 322 HashEntry **ref = &t->buckets[he->key_hash & t->bucketsMask]; 323 HashEntry *p; 324 325 for (; (p = *ref) != NULL; ref = &p->next) { 326 if (p == he) { 327 *ref = p->next; 328 free(p); 329 t->numEntries--; 330 return; 331 } 332 } 333 abort(); 334 } 335 336 /* Set things up for iterating over all entries in the hash table. */ 337 void 338 HashIter_Init(HashIter *hi, HashTable *t) 339 { 340 hi->table = t; 341 hi->nextBucket = 0; 342 hi->entry = NULL; 343 } 344 345 /* 346 * Return the next entry in the hash table, or NULL if the end of the table 347 * is reached. 348 */ 349 HashEntry * 350 HashIter_Next(HashIter *hi) 351 { 352 HashTable *t = hi->table; 353 HashEntry *he = hi->entry; 354 HashEntry **buckets = t->buckets; 355 unsigned int bucketsSize = t->bucketsSize; 356 357 if (he != NULL) 358 he = he->next; /* skip the most recently returned entry */ 359 360 while (he == NULL) { /* find the next nonempty chain */ 361 if (hi->nextBucket >= bucketsSize) 362 return NULL; 363 he = buckets[hi->nextBucket++]; 364 } 365 hi->entry = he; 366 return he; 367 } 368 369 void 370 HashTable_DebugStats(HashTable *t, const char *name) 371 { 372 DEBUG4(HASH, "HashTable %s: size=%u numEntries=%u maxchain=%u\n", 373 name, t->bucketsSize, t->numEntries, t->maxchain); 374 } 375