1 /* $NetBSD: hash.c,v 1.79 2024/07/07 09:37:00 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 and pointer values. */ 73 74 #include "make.h" 75 76 /* "@(#)hash.c 8.1 (Berkeley) 6/6/93" */ 77 MAKE_RCSID("$NetBSD: hash.c,v 1.79 2024/07/07 09:37:00 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 *he; 117 size_t keyLen = Substring_Length(key); 118 119 #ifdef DEBUG_HASH_LOOKUP 120 DEBUG4(HASH, "HashTable_Find: %p h=%08x key=%.*s\n", 121 t, h, (int)keyLen, key.start); 122 #endif 123 124 for (he = t->buckets[h & t->bucketsMask]; he != NULL; he = he->next) { 125 if (he->hash == h && 126 strncmp(he->key, key.start, keyLen) == 0 && 127 he->key[keyLen] == '\0') 128 break; 129 } 130 131 return he; 132 } 133 134 /* Set up the hash table. */ 135 void 136 HashTable_Init(HashTable *t) 137 { 138 unsigned int n = 16, i; 139 HashEntry **buckets = bmake_malloc(sizeof *buckets * n); 140 for (i = 0; i < n; i++) 141 buckets[i] = NULL; 142 143 t->buckets = buckets; 144 t->bucketsSize = n; 145 t->numEntries = 0; 146 t->bucketsMask = n - 1; 147 } 148 149 /* 150 * Remove everything from the hash table and free up the memory for the keys 151 * of the hash table, but not for the values associated to these keys. 152 */ 153 void 154 HashTable_Done(HashTable *t) 155 { 156 HashEntry **buckets = t->buckets; 157 size_t i, n = t->bucketsSize; 158 159 for (i = 0; i < n; i++) { 160 HashEntry *he = buckets[i]; 161 while (he != NULL) { 162 HashEntry *next = he->next; 163 free(he); 164 he = next; 165 } 166 } 167 168 free(t->buckets); 169 #ifdef CLEANUP 170 t->buckets = NULL; 171 #endif 172 } 173 174 /* Find the entry corresponding to the key, or return NULL. */ 175 HashEntry * 176 HashTable_FindEntry(HashTable *t, const char *key) 177 { 178 const char *keyEnd; 179 unsigned int h = Hash_String(key, &keyEnd); 180 return HashTable_Find(t, Substring_Init(key, keyEnd), h); 181 } 182 183 /* Find the value corresponding to the key, or return NULL. */ 184 void * 185 HashTable_FindValue(HashTable *t, const char *key) 186 { 187 HashEntry *he = HashTable_FindEntry(t, key); 188 return he != NULL ? he->value : NULL; 189 } 190 191 /* 192 * Find the value corresponding to the key and the precomputed hash, 193 * or return NULL. 194 */ 195 void * 196 HashTable_FindValueBySubstringHash(HashTable *t, Substring key, unsigned int h) 197 { 198 HashEntry *he = HashTable_Find(t, key, h); 199 return he != NULL ? he->value : NULL; 200 } 201 202 static unsigned 203 HashTable_MaxChain(const HashTable *t) 204 { 205 unsigned b, cl, max_cl = 0; 206 for (b = 0; b < t->bucketsSize; b++) { 207 const HashEntry *he = t->buckets[b]; 208 for (cl = 0; he != NULL; he = he->next) 209 cl++; 210 if (cl > max_cl) 211 max_cl = cl; 212 } 213 return max_cl; 214 } 215 216 /* 217 * Make the hash table larger. Any bucket numbers from the old table become 218 * invalid; the hash values stay valid though. 219 */ 220 static void 221 HashTable_Enlarge(HashTable *t) 222 { 223 unsigned int oldSize = t->bucketsSize; 224 HashEntry **oldBuckets = t->buckets; 225 unsigned int newSize = 2 * oldSize; 226 unsigned int newMask = newSize - 1; 227 HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize); 228 size_t i; 229 230 for (i = 0; i < newSize; i++) 231 newBuckets[i] = NULL; 232 233 for (i = 0; i < oldSize; i++) { 234 HashEntry *he = oldBuckets[i]; 235 while (he != NULL) { 236 HashEntry *next = he->next; 237 he->next = newBuckets[he->hash & newMask]; 238 newBuckets[he->hash & newMask] = he; 239 he = next; 240 } 241 } 242 243 free(oldBuckets); 244 245 t->bucketsSize = newSize; 246 t->bucketsMask = newMask; 247 t->buckets = newBuckets; 248 DEBUG4(HASH, "HashTable_Enlarge: %p size=%d entries=%d maxchain=%d\n", 249 (void *)t, t->bucketsSize, t->numEntries, HashTable_MaxChain(t)); 250 } 251 252 /* 253 * Find or create an entry corresponding to the key. 254 * Return in out_isNew whether a new entry has been created. 255 */ 256 HashEntry * 257 HashTable_CreateEntry(HashTable *t, const char *key, bool *out_isNew) 258 { 259 const char *keyEnd; 260 unsigned int h = Hash_String(key, &keyEnd); 261 HashEntry *he = HashTable_Find(t, Substring_Init(key, keyEnd), h); 262 263 if (he != NULL) { 264 if (out_isNew != NULL) 265 *out_isNew = false; 266 return he; 267 } 268 269 if (t->numEntries >= rebuildLimit * t->bucketsSize) 270 HashTable_Enlarge(t); 271 272 he = bmake_malloc(sizeof *he + (size_t)(keyEnd - key)); 273 he->value = NULL; 274 he->hash = h; 275 memcpy(he->key, key, (size_t)(keyEnd - key) + 1); 276 277 he->next = t->buckets[h & t->bucketsMask]; 278 t->buckets[h & t->bucketsMask] = he; 279 t->numEntries++; 280 281 if (out_isNew != NULL) 282 *out_isNew = true; 283 return he; 284 } 285 286 void 287 HashTable_Set(HashTable *t, const char *key, void *value) 288 { 289 HashEntry *he = HashTable_CreateEntry(t, key, NULL); 290 HashEntry_Set(he, value); 291 } 292 293 /* Delete the entry from the table, don't free the value of the entry. */ 294 void 295 HashTable_DeleteEntry(HashTable *t, HashEntry *he) 296 { 297 HashEntry **ref = &t->buckets[he->hash & t->bucketsMask]; 298 299 for (; *ref != he; ref = &(*ref)->next) 300 continue; 301 *ref = he->next; 302 free(he); 303 t->numEntries--; 304 } 305 306 /* 307 * Place the next entry from the hash table in hi->entry, or return false if 308 * the end of the table is reached. 309 */ 310 bool 311 HashIter_Next(HashIter *hi) 312 { 313 HashTable *t = hi->table; 314 HashEntry *he = hi->entry; 315 HashEntry **buckets = t->buckets; 316 unsigned int bucketsSize = t->bucketsSize; 317 318 if (he != NULL) 319 he = he->next; /* skip the most recently returned entry */ 320 321 while (he == NULL) { /* find the next nonempty chain */ 322 if (hi->nextBucket >= bucketsSize) 323 return false; 324 he = buckets[hi->nextBucket++]; 325 } 326 hi->entry = he; 327 return true; 328 } 329 330 void 331 HashTable_DebugStats(const HashTable *t, const char *name) 332 { 333 DEBUG4(HASH, "HashTable \"%s\": size=%u entries=%u maxchain=%u\n", 334 name, t->bucketsSize, t->numEntries, HashTable_MaxChain(t)); 335 } 336