1 /* $NetBSD: hash.c,v 1.71 2022/01/27 11:00:07 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 1.71 2022/01/27 11:00:07 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, const char **out_keyEnd) 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 *out_keyEnd = p; 97 return h; 98 } 99 100 /* This hash function matches Gosling's Emacs and java.lang.String. */ 101 unsigned int 102 Hash_Substring(Substring key) 103 { 104 unsigned int h; 105 const char *p; 106 107 h = 0; 108 for (p = key.start; p != key.end; p++) 109 h = 31 * h + (unsigned char)*p; 110 return h; 111 } 112 113 static HashEntry * 114 HashTable_Find(HashTable *t, Substring key, unsigned int h) 115 { 116 HashEntry *e; 117 unsigned int chainlen = 0; 118 size_t keyLen = Substring_Length(key); 119 120 #ifdef DEBUG_HASH_LOOKUP 121 DEBUG4(HASH, "HashTable_Find: %p h=%08x key=%.*s\n", 122 t, h, (int)keyLen, key.start); 123 #endif 124 125 for (e = t->buckets[h & t->bucketsMask]; e != NULL; e = e->next) { 126 chainlen++; 127 if (e->key_hash == h && 128 strncmp(e->key, key.start, keyLen) == 0 && 129 e->key[keyLen] == '\0') 130 break; 131 } 132 133 if (chainlen > t->maxchain) 134 t->maxchain = chainlen; 135 136 return e; 137 } 138 139 /* Set up the hash table. */ 140 void 141 HashTable_Init(HashTable *t) 142 { 143 unsigned int n = 16, i; 144 HashEntry **buckets = bmake_malloc(sizeof *buckets * n); 145 for (i = 0; i < n; i++) 146 buckets[i] = NULL; 147 148 t->buckets = buckets; 149 t->bucketsSize = n; 150 t->numEntries = 0; 151 t->bucketsMask = n - 1; 152 t->maxchain = 0; 153 } 154 155 /* 156 * Remove everything from the hash table and free up the memory for the keys 157 * of the hash table, but not for the values associated to these keys. 158 */ 159 void 160 HashTable_Done(HashTable *t) 161 { 162 HashEntry **buckets = t->buckets; 163 size_t i, n = t->bucketsSize; 164 165 for (i = 0; i < n; i++) { 166 HashEntry *he = buckets[i]; 167 while (he != NULL) { 168 HashEntry *next = he->next; 169 free(he); 170 he = next; 171 } 172 } 173 174 free(t->buckets); 175 #ifdef CLEANUP 176 t->buckets = NULL; 177 #endif 178 } 179 180 /* Find the entry corresponding to the key, or return NULL. */ 181 HashEntry * 182 HashTable_FindEntry(HashTable *t, const char *key) 183 { 184 const char *keyEnd; 185 unsigned int h = Hash_String(key, &keyEnd); 186 return HashTable_Find(t, Substring_Init(key, keyEnd), h); 187 } 188 189 /* Find the value corresponding to the key, or return NULL. */ 190 void * 191 HashTable_FindValue(HashTable *t, const char *key) 192 { 193 HashEntry *he = HashTable_FindEntry(t, key); 194 return he != NULL ? he->value : NULL; 195 } 196 197 /* 198 * Find the value corresponding to the key and the precomputed hash, 199 * or return NULL. 200 */ 201 void * 202 HashTable_FindValueBySubstringHash(HashTable *t, Substring key, unsigned int h) 203 { 204 HashEntry *he = HashTable_Find(t, key, h); 205 return he != NULL ? he->value : NULL; 206 } 207 208 /* 209 * Make the hash table larger. Any bucket numbers from the old table become 210 * invalid; the hash codes stay valid though. 211 */ 212 static void 213 HashTable_Enlarge(HashTable *t) 214 { 215 unsigned int oldSize = t->bucketsSize; 216 HashEntry **oldBuckets = t->buckets; 217 unsigned int newSize = 2 * oldSize; 218 unsigned int newMask = newSize - 1; 219 HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize); 220 size_t i; 221 222 for (i = 0; i < newSize; i++) 223 newBuckets[i] = NULL; 224 225 for (i = 0; i < oldSize; i++) { 226 HashEntry *he = oldBuckets[i]; 227 while (he != NULL) { 228 HashEntry *next = he->next; 229 he->next = newBuckets[he->key_hash & newMask]; 230 newBuckets[he->key_hash & newMask] = he; 231 he = next; 232 } 233 } 234 235 free(oldBuckets); 236 237 t->bucketsSize = newSize; 238 t->bucketsMask = newMask; 239 t->buckets = newBuckets; 240 DEBUG4(HASH, "HashTable_Enlarge: %p size=%d entries=%d maxchain=%d\n", 241 (void *)t, t->bucketsSize, t->numEntries, t->maxchain); 242 t->maxchain = 0; 243 } 244 245 /* 246 * Find or create an entry corresponding to the key. 247 * Return in out_isNew whether a new entry has been created. 248 */ 249 HashEntry * 250 HashTable_CreateEntry(HashTable *t, const char *key, bool *out_isNew) 251 { 252 const char *keyEnd; 253 unsigned int h = Hash_String(key, &keyEnd); 254 HashEntry *he = HashTable_Find(t, Substring_Init(key, keyEnd), h); 255 256 if (he != NULL) { 257 if (out_isNew != NULL) 258 *out_isNew = false; 259 return he; 260 } 261 262 if (t->numEntries >= rebuildLimit * t->bucketsSize) 263 HashTable_Enlarge(t); 264 265 he = bmake_malloc(sizeof *he + (size_t)(keyEnd - key)); 266 he->value = NULL; 267 he->key_hash = h; 268 memcpy(he->key, key, (size_t)(keyEnd - key) + 1); 269 270 he->next = t->buckets[h & t->bucketsMask]; 271 t->buckets[h & t->bucketsMask] = he; 272 t->numEntries++; 273 274 if (out_isNew != NULL) 275 *out_isNew = true; 276 return he; 277 } 278 279 void 280 HashTable_Set(HashTable *t, const char *key, void *value) 281 { 282 HashEntry *he = HashTable_CreateEntry(t, key, NULL); 283 HashEntry_Set(he, value); 284 } 285 286 /* Delete the entry from the table and free the associated memory. */ 287 void 288 HashTable_DeleteEntry(HashTable *t, HashEntry *he) 289 { 290 HashEntry **ref = &t->buckets[he->key_hash & t->bucketsMask]; 291 HashEntry *p; 292 293 for (; (p = *ref) != NULL; ref = &p->next) { 294 if (p == he) { 295 *ref = p->next; 296 free(p); 297 t->numEntries--; 298 return; 299 } 300 } 301 abort(); 302 } 303 304 /* 305 * Return the next entry in the hash table, or NULL if the end of the table 306 * is reached. 307 */ 308 HashEntry * 309 HashIter_Next(HashIter *hi) 310 { 311 HashTable *t = hi->table; 312 HashEntry *he = hi->entry; 313 HashEntry **buckets = t->buckets; 314 unsigned int bucketsSize = t->bucketsSize; 315 316 if (he != NULL) 317 he = he->next; /* skip the most recently returned entry */ 318 319 while (he == NULL) { /* find the next nonempty chain */ 320 if (hi->nextBucket >= bucketsSize) 321 return NULL; 322 he = buckets[hi->nextBucket++]; 323 } 324 hi->entry = he; 325 return he; 326 } 327 328 void 329 HashTable_DebugStats(HashTable *t, const char *name) 330 { 331 DEBUG4(HASH, "HashTable %s: size=%u numEntries=%u maxchain=%u\n", 332 name, t->bucketsSize, t->numEntries, t->maxchain); 333 } 334