1 /* $NetBSD: hash.c,v 1.5 2007/03/03 00:09:30 simonb 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 1.5 2007/03/03 00:09:30 simonb 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 1.5 2007/03/03 00:09:30 simonb 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 #include <err.h> 91 #include <util.h> 92 93 /* hash.c -- 94 * 95 * This module contains routines to manipulate a hash table. 96 * See hash.h for a definition of the structure of the hash 97 * table. Hash tables grow automatically as the amount of 98 * information increases. 99 */ 100 #include "hash.h" 101 102 /* 103 * Forward references to local procedures that are used before they're 104 * defined: 105 */ 106 107 static void RebuildTable(Hash_Table *); 108 109 /* 110 * The following defines the ratio of # entries to # buckets 111 * at which we rebuild the table to make it larger. 112 */ 113 114 #define rebuildLimit 8 115 116 /* 117 *--------------------------------------------------------- 118 * 119 * Hash_InitTable -- 120 * 121 * This routine just sets up the hash table. 122 * 123 * Input: 124 * t Structure to use to hold table. 125 * numBuckets How many buckets to create for starters. This number 126 * is rounded up to a power of two. If <= 0, a reasonable 127 * default is chosen. The table will grow in size later 128 * as needed. 129 * 130 * Results: 131 * None. 132 * 133 * Side Effects: 134 * Memory is allocated for the initial bucket area. 135 * 136 *--------------------------------------------------------- 137 */ 138 139 void 140 Hash_InitTable(Hash_Table *t, int numBuckets) 141 { 142 int i; 143 struct Hash_Entry **hp; 144 145 /* 146 * Round up the size to a power of two. 147 */ 148 if (numBuckets <= 0) 149 i = 16; 150 else { 151 for (i = 2; i < numBuckets; i <<= 1) 152 continue; 153 } 154 t->numEntries = 0; 155 t->size = i; 156 t->mask = i - 1; 157 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 158 while (--i >= 0) 159 *hp++ = NULL; 160 } 161 162 /* 163 *--------------------------------------------------------- 164 * 165 * Hash_DeleteTable -- 166 * 167 * This routine removes everything from a hash table 168 * and frees up the memory space it occupied (except for 169 * the space in the Hash_Table structure). 170 * 171 * Results: 172 * None. 173 * 174 * Side Effects: 175 * Lots of memory is freed up. 176 * 177 *--------------------------------------------------------- 178 */ 179 180 void 181 Hash_DeleteTable(Hash_Table *t) 182 { 183 struct Hash_Entry **hp, *h, *nexth; 184 int i; 185 186 nexth = NULL; 187 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 188 for (h = *hp++; h != NULL; h = nexth) { 189 nexth = h->next; 190 free(h); 191 } 192 } 193 free(t->bucketPtr); 194 195 /* 196 * Set up the hash table to cause memory faults on any future access 197 * attempts until re-initialization. 198 */ 199 t->bucketPtr = NULL; 200 } 201 202 /* 203 *--------------------------------------------------------- 204 * 205 * Hash_FindEntry -- 206 * 207 * Searches a hash table for an entry corresponding to key. 208 * 209 * Input: 210 * t Hash table to search. 211 * key A hash key. 212 * 213 * Results: 214 * The return value is a pointer to the entry for key, 215 * if key was present in the table. If key was not 216 * present, NULL is returned. 217 * 218 * Side Effects: 219 * None. 220 * 221 *--------------------------------------------------------- 222 */ 223 224 Hash_Entry * 225 Hash_FindEntry(Hash_Table *t, char *key) 226 { 227 Hash_Entry *e; 228 unsigned h; 229 char *p; 230 231 for (h = 0, p = key; *p;) 232 h = (h << 5) - h + *p++; 233 p = key; 234 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 235 if (e->namehash == h && strcmp(e->name, p) == 0) 236 return (e); 237 return (NULL); 238 } 239 240 /* 241 *--------------------------------------------------------- 242 * 243 * Hash_CreateEntry -- 244 * 245 * Searches a hash table for an entry corresponding to 246 * key. If no entry is found, then one is created. 247 * 248 * Input: 249 * t Hash table to search. 250 * key A hash key. 251 * newPtr Filled in with 1 if new entry created, 0 otherwise. 252 * 253 * Results: 254 * The return value is a pointer to the entry. If *newPtr 255 * isn't NULL, then *newPtr is filled in with TRUE if a 256 * new entry was created, and FALSE if an entry already existed 257 * with the given key. 258 * 259 * Side Effects: 260 * Memory may be allocated, and the hash buckets may be modified. 261 *--------------------------------------------------------- 262 */ 263 264 Hash_Entry * 265 Hash_CreateEntry(Hash_Table *t, char *key, int *newPtr) 266 { 267 Hash_Entry *e; 268 unsigned h; 269 char *p; 270 int keylen; 271 struct Hash_Entry **hp; 272 273 /* 274 * Hash the key. As a side effect, save the length (strlen) of the 275 * key in case we need to create the entry. 276 */ 277 for (h = 0, p = key; *p;) 278 h = (h << 5) - h + *p++; 279 keylen = p - key; 280 p = key; 281 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 282 if (e->namehash == h && strcmp(e->name, p) == 0) { 283 if (newPtr != NULL) 284 *newPtr = 0; 285 return (e); 286 } 287 } 288 289 /* 290 * The desired entry isn't there. Before allocating a new entry, 291 * expand the table if necessary (and this changes the resulting 292 * bucket chain). 293 */ 294 if (t->numEntries >= rebuildLimit * t->size) 295 RebuildTable(t); 296 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 297 hp = &t->bucketPtr[h & t->mask]; 298 e->next = *hp; 299 *hp = e; 300 e->clientData = NULL; 301 e->namehash = h; 302 (void) strcpy(e->name, p); 303 t->numEntries++; 304 305 if (newPtr != NULL) 306 *newPtr = 1; 307 return (e); 308 } 309 310 /* 311 *--------------------------------------------------------- 312 * 313 * Hash_DeleteEntry -- 314 * 315 * Delete the given hash table entry and free memory associated with 316 * it. 317 * 318 * Results: 319 * None. 320 * 321 * Side Effects: 322 * Hash chain that entry lives in is modified and memory is freed. 323 * 324 *--------------------------------------------------------- 325 */ 326 327 void 328 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e) 329 { 330 Hash_Entry **hp, *p; 331 332 if (e == NULL) 333 return; 334 for (hp = &t->bucketPtr[e->namehash & t->mask]; 335 (p = *hp) != NULL; hp = &p->next) { 336 if (p == e) { 337 *hp = p->next; 338 free(p); 339 t->numEntries--; 340 return; 341 } 342 } 343 (void)write(2, "bad call to Hash_DeleteEntry\n", 29); 344 abort(); 345 } 346 347 /* 348 *--------------------------------------------------------- 349 * 350 * Hash_EnumFirst -- 351 * This procedure sets things up for a complete search 352 * of all entries recorded in the hash table. 353 * 354 * Input: 355 * t Table to be searched. 356 * searchPtr Area in which to keep state about search. 357 * 358 * Results: 359 * The return value is the address of the first entry in 360 * the hash table, or NULL if the table is empty. 361 * 362 * Side Effects: 363 * The information in searchPtr is initialized so that successive 364 * calls to Hash_Next will return successive HashEntry's 365 * from the table. 366 * 367 *--------------------------------------------------------- 368 */ 369 370 Hash_Entry * 371 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr) 372 { 373 374 searchPtr->tablePtr = t; 375 searchPtr->nextIndex = 0; 376 searchPtr->hashEntryPtr = NULL; 377 return Hash_EnumNext(searchPtr); 378 } 379 380 /* 381 *--------------------------------------------------------- 382 * 383 * Hash_EnumNext -- 384 * This procedure returns successive entries in the hash table. 385 * 386 * Results: 387 * The return value is a pointer to the next HashEntry 388 * in the table, or NULL when the end of the table is 389 * reached. 390 * 391 * Side Effects: 392 * The information in searchPtr is modified to advance to the 393 * next entry. 394 * 395 *--------------------------------------------------------- 396 */ 397 398 Hash_Entry * 399 Hash_EnumNext(Hash_Search *searchPtr) 400 { 401 Hash_Entry *e; 402 Hash_Table *t = searchPtr->tablePtr; 403 404 /* 405 * The hashEntryPtr field points to the most recently returned 406 * entry, or is nil if we are starting up. If not nil, we have 407 * to start at the next one in the chain. 408 */ 409 e = searchPtr->hashEntryPtr; 410 if (e != NULL) 411 e = e->next; 412 /* 413 * If the chain ran out, or if we are starting up, we need to 414 * find the next nonempty chain. 415 */ 416 while (e == NULL) { 417 if (searchPtr->nextIndex >= t->size) 418 return (NULL); 419 e = t->bucketPtr[searchPtr->nextIndex++]; 420 } 421 searchPtr->hashEntryPtr = e; 422 return (e); 423 } 424 425 /* 426 *--------------------------------------------------------- 427 * 428 * RebuildTable -- 429 * This local routine makes a new hash table that 430 * is larger than the old one. 431 * 432 * Results: 433 * None. 434 * 435 * Side Effects: 436 * The entire hash table is moved, so any bucket numbers 437 * from the old table are invalid. 438 * 439 *--------------------------------------------------------- 440 */ 441 442 static void 443 RebuildTable(Hash_Table *t) 444 { 445 Hash_Entry *e, *next, **hp, **xp; 446 int i, mask; 447 Hash_Entry **oldhp; 448 int oldsize; 449 450 next = NULL; 451 oldhp = t->bucketPtr; 452 oldsize = i = t->size; 453 i <<= 1; 454 t->size = i; 455 t->mask = mask = i - 1; 456 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 457 while (--i >= 0) 458 *hp++ = NULL; 459 for (hp = oldhp, i = oldsize; --i >= 0;) { 460 for (e = *hp++; e != NULL; e = next) { 461 next = e->next; 462 xp = &t->bucketPtr[e->namehash & mask]; 463 e->next = *xp; 464 *xp = e; 465 } 466 } 467 free(oldhp); 468 } 469
Indexes created Sun Sep 21 20:09:37 GMT 2025