hash.c revision 1.3
1 /* $NetBSD: hash.c,v 1.3 2003/08/07 10:04:37 agc 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 #ifdef MAKE_BOOTSTRAP 73 static char rcsid[] = "$NetBSD: hash.c,v 1.3 2003/08/07 10:04:37 agc Exp $"; 74 #else 75 #include <sys/cdefs.h> 76 #ifndef lint 77 #if 0 78 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93"; 79 #else 80 __RCSID("$NetBSD: hash.c,v 1.3 2003/08/07 10:04:37 agc Exp $"); 81 #endif 82 #endif /* not lint */ 83 #endif 84 85 #include <sys/types.h> 86 87 #include <stdlib.h> 88 #include <string.h> 89 #include <unistd.h> 90 91 /* hash.c -- 92 * 93 * This module contains routines to manipulate a hash table. 94 * See hash.h for a definition of the structure of the hash 95 * table. Hash tables grow automatically as the amount of 96 * information increases. 97 */ 98 #include "hash.h" 99 #include "ealloc.h" 100 101 /* 102 * Forward references to local procedures that are used before they're 103 * defined: 104 */ 105 106 static void RebuildTable(Hash_Table *); 107 108 /* 109 * The following defines the ratio of # entries to # buckets 110 * at which we rebuild the table to make it larger. 111 */ 112 113 #define rebuildLimit 8 114 115 /* 116 *--------------------------------------------------------- 117 * 118 * Hash_InitTable -- 119 * 120 * This routine just sets up the hash table. 121 * 122 * Input: 123 * t Structure to use to hold table. 124 * numBuckets How many buckets to create for starters. This number 125 * is rounded up to a power of two. If <= 0, a reasonable 126 * default is chosen. The table will grow in size later 127 * as needed. 128 * 129 * Results: 130 * None. 131 * 132 * Side Effects: 133 * Memory is allocated for the initial bucket area. 134 * 135 *--------------------------------------------------------- 136 */ 137 138 void 139 Hash_InitTable(Hash_Table *t, int numBuckets) 140 { 141 int i; 142 struct Hash_Entry **hp; 143 144 /* 145 * Round up the size to a power of two. 146 */ 147 if (numBuckets <= 0) 148 i = 16; 149 else { 150 for (i = 2; i < numBuckets; i <<= 1) 151 continue; 152 } 153 t->numEntries = 0; 154 t->size = i; 155 t->mask = i - 1; 156 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 157 while (--i >= 0) 158 *hp++ = NULL; 159 } 160 161 /* 162 *--------------------------------------------------------- 163 * 164 * Hash_DeleteTable -- 165 * 166 * This routine removes everything from a hash table 167 * and frees up the memory space it occupied (except for 168 * the space in the Hash_Table structure). 169 * 170 * Results: 171 * None. 172 * 173 * Side Effects: 174 * Lots of memory is freed up. 175 * 176 *--------------------------------------------------------- 177 */ 178 179 void 180 Hash_DeleteTable(Hash_Table *t) 181 { 182 struct Hash_Entry **hp, *h, *nexth; 183 int i; 184 185 nexth = NULL; 186 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 187 for (h = *hp++; h != NULL; h = nexth) { 188 nexth = h->next; 189 free((char *)h); 190 } 191 } 192 free((char *)t->bucketPtr); 193 194 /* 195 * Set up the hash table to cause memory faults on any future access 196 * attempts until re-initialization. 197 */ 198 t->bucketPtr = NULL; 199 } 200 201 /* 202 *--------------------------------------------------------- 203 * 204 * Hash_FindEntry -- 205 * 206 * Searches a hash table for an entry corresponding to key. 207 * 208 * Input: 209 * t Hash table to search. 210 * key A hash key. 211 * 212 * Results: 213 * The return value is a pointer to the entry for key, 214 * if key was present in the table. If key was not 215 * present, NULL is returned. 216 * 217 * Side Effects: 218 * None. 219 * 220 *--------------------------------------------------------- 221 */ 222 223 Hash_Entry * 224 Hash_FindEntry(Hash_Table *t, char *key) 225 { 226 Hash_Entry *e; 227 unsigned h; 228 char *p; 229 230 for (h = 0, p = key; *p;) 231 h = (h << 5) - h + *p++; 232 p = key; 233 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 234 if (e->namehash == h && strcmp(e->name, p) == 0) 235 return (e); 236 return (NULL); 237 } 238 239 /* 240 *--------------------------------------------------------- 241 * 242 * Hash_CreateEntry -- 243 * 244 * Searches a hash table for an entry corresponding to 245 * key. If no entry is found, then one is created. 246 * 247 * Input: 248 * t Hash table to search. 249 * key A hash key. 250 * newPtr Filled in with 1 if new entry created, 0 otherwise. 251 * 252 * Results: 253 * The return value is a pointer to the entry. If *newPtr 254 * isn't NULL, then *newPtr is filled in with TRUE if a 255 * new entry was created, and FALSE if an entry already existed 256 * with the given key. 257 * 258 * Side Effects: 259 * Memory may be allocated, and the hash buckets may be modified. 260 *--------------------------------------------------------- 261 */ 262 263 Hash_Entry * 264 Hash_CreateEntry(Hash_Table *t, char *key, int *newPtr) 265 { 266 Hash_Entry *e; 267 unsigned h; 268 char *p; 269 int keylen; 270 struct Hash_Entry **hp; 271 272 /* 273 * Hash the key. As a side effect, save the length (strlen) of the 274 * key in case we need to create the entry. 275 */ 276 for (h = 0, p = key; *p;) 277 h = (h << 5) - h + *p++; 278 keylen = p - key; 279 p = key; 280 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 281 if (e->namehash == h && strcmp(e->name, p) == 0) { 282 if (newPtr != NULL) 283 *newPtr = 0; 284 return (e); 285 } 286 } 287 288 /* 289 * The desired entry isn't there. Before allocating a new entry, 290 * expand the table if necessary (and this changes the resulting 291 * bucket chain). 292 */ 293 if (t->numEntries >= rebuildLimit * t->size) 294 RebuildTable(t); 295 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 296 hp = &t->bucketPtr[h & t->mask]; 297 e->next = *hp; 298 *hp = e; 299 e->clientData = NULL; 300 e->namehash = h; 301 (void) strcpy(e->name, p); 302 t->numEntries++; 303 304 if (newPtr != NULL) 305 *newPtr = 1; 306 return (e); 307 } 308 309 /* 310 *--------------------------------------------------------- 311 * 312 * Hash_DeleteEntry -- 313 * 314 * Delete the given hash table entry and free memory associated with 315 * it. 316 * 317 * Results: 318 * None. 319 * 320 * Side Effects: 321 * Hash chain that entry lives in is modified and memory is freed. 322 * 323 *--------------------------------------------------------- 324 */ 325 326 void 327 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e) 328 { 329 Hash_Entry **hp, *p; 330 331 if (e == NULL) 332 return; 333 for (hp = &t->bucketPtr[e->namehash & t->mask]; 334 (p = *hp) != NULL; hp = &p->next) { 335 if (p == e) { 336 *hp = p->next; 337 free((char *)p); 338 t->numEntries--; 339 return; 340 } 341 } 342 (void)write(2, "bad call to Hash_DeleteEntry\n", 29); 343 abort(); 344 } 345 346 /* 347 *--------------------------------------------------------- 348 * 349 * Hash_EnumFirst -- 350 * This procedure sets things up for a complete search 351 * of all entries recorded in the hash table. 352 * 353 * Input: 354 * t Table to be searched. 355 * searchPtr Area in which to keep state about search. 356 * 357 * Results: 358 * The return value is the address of the first entry in 359 * the hash table, or NULL if the table is empty. 360 * 361 * Side Effects: 362 * The information in searchPtr is initialized so that successive 363 * calls to Hash_Next will return successive HashEntry's 364 * from the table. 365 * 366 *--------------------------------------------------------- 367 */ 368 369 Hash_Entry * 370 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr) 371 { 372 373 searchPtr->tablePtr = t; 374 searchPtr->nextIndex = 0; 375 searchPtr->hashEntryPtr = NULL; 376 return Hash_EnumNext(searchPtr); 377 } 378 379 /* 380 *--------------------------------------------------------- 381 * 382 * Hash_EnumNext -- 383 * This procedure returns successive entries in the hash table. 384 * 385 * Results: 386 * The return value is a pointer to the next HashEntry 387 * in the table, or NULL when the end of the table is 388 * reached. 389 * 390 * Side Effects: 391 * The information in searchPtr is modified to advance to the 392 * next entry. 393 * 394 *--------------------------------------------------------- 395 */ 396 397 Hash_Entry * 398 Hash_EnumNext(Hash_Search *searchPtr) 399 { 400 Hash_Entry *e; 401 Hash_Table *t = searchPtr->tablePtr; 402 403 /* 404 * The hashEntryPtr field points to the most recently returned 405 * entry, or is nil if we are starting up. If not nil, we have 406 * to start at the next one in the chain. 407 */ 408 e = searchPtr->hashEntryPtr; 409 if (e != NULL) 410 e = e->next; 411 /* 412 * If the chain ran out, or if we are starting up, we need to 413 * find the next nonempty chain. 414 */ 415 while (e == NULL) { 416 if (searchPtr->nextIndex >= t->size) 417 return (NULL); 418 e = t->bucketPtr[searchPtr->nextIndex++]; 419 } 420 searchPtr->hashEntryPtr = e; 421 return (e); 422 } 423 424 /* 425 *--------------------------------------------------------- 426 * 427 * RebuildTable -- 428 * This local routine makes a new hash table that 429 * is larger than the old one. 430 * 431 * Results: 432 * None. 433 * 434 * Side Effects: 435 * The entire hash table is moved, so any bucket numbers 436 * from the old table are invalid. 437 * 438 *--------------------------------------------------------- 439 */ 440 441 static void 442 RebuildTable(Hash_Table *t) 443 { 444 Hash_Entry *e, *next, **hp, **xp; 445 int i, mask; 446 Hash_Entry **oldhp; 447 int oldsize; 448 449 next = NULL; 450 oldhp = t->bucketPtr; 451 oldsize = i = t->size; 452 i <<= 1; 453 t->size = i; 454 t->mask = mask = i - 1; 455 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 456 while (--i >= 0) 457 *hp++ = NULL; 458 for (hp = oldhp, i = oldsize; --i >= 0;) { 459 for (e = *hp++; e != NULL; e = next) { 460 next = e->next; 461 xp = &t->bucketPtr[e->namehash & mask]; 462 e->next = *xp; 463 *xp = e; 464 } 465 } 466 free((char *)oldhp); 467 } 468
Indexes created Fri Sep 26 08:10:20 GMT 2025