1 /* $NetBSD: hash.c,v 1.2 2002/06/30 14:17:44 lukem Exp $ */ 2 3 /* 4 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. 5 * Copyright (c) 1988, 1989 by Adam de Boor 6 * Copyright (c) 1989 by Berkeley Softworks 7 * All rights reserved. 8 * 9 * This code is derived from software contributed to Berkeley by 10 * Adam de Boor. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 */ 40 41 #ifdef MAKE_BOOTSTRAP 42 static char rcsid[] = "$NetBSD: hash.c,v 1.2 2002/06/30 14:17:44 lukem Exp $"; 43 #else 44 #include <sys/cdefs.h> 45 #ifndef lint 46 #if 0 47 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93"; 48 #else 49 __RCSID("$NetBSD: hash.c,v 1.2 2002/06/30 14:17:44 lukem Exp $"); 50 #endif 51 #endif /* not lint */ 52 #endif 53 54 #include <sys/types.h> 55 56 #include <stdlib.h> 57 #include <string.h> 58 #include <unistd.h> 59 60 /* hash.c -- 61 * 62 * This module contains routines to manipulate a hash table. 63 * See hash.h for a definition of the structure of the hash 64 * table. Hash tables grow automatically as the amount of 65 * information increases. 66 */ 67 #include "hash.h" 68 #include "ealloc.h" 69 70 /* 71 * Forward references to local procedures that are used before they're 72 * defined: 73 */ 74 75 static void RebuildTable(Hash_Table *); 76 77 /* 78 * The following defines the ratio of # entries to # buckets 79 * at which we rebuild the table to make it larger. 80 */ 81 82 #define rebuildLimit 8 83 84 /* 85 *--------------------------------------------------------- 86 * 87 * Hash_InitTable -- 88 * 89 * This routine just sets up the hash table. 90 * 91 * Input: 92 * t Structure to use to hold table. 93 * numBuckets How many buckets to create for starters. This number 94 * is rounded up to a power of two. If <= 0, a reasonable 95 * default is chosen. The table will grow in size later 96 * as needed. 97 * 98 * Results: 99 * None. 100 * 101 * Side Effects: 102 * Memory is allocated for the initial bucket area. 103 * 104 *--------------------------------------------------------- 105 */ 106 107 void 108 Hash_InitTable(Hash_Table *t, int numBuckets) 109 { 110 int i; 111 struct Hash_Entry **hp; 112 113 /* 114 * Round up the size to a power of two. 115 */ 116 if (numBuckets <= 0) 117 i = 16; 118 else { 119 for (i = 2; i < numBuckets; i <<= 1) 120 continue; 121 } 122 t->numEntries = 0; 123 t->size = i; 124 t->mask = i - 1; 125 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 126 while (--i >= 0) 127 *hp++ = NULL; 128 } 129 130 /* 131 *--------------------------------------------------------- 132 * 133 * Hash_DeleteTable -- 134 * 135 * This routine removes everything from a hash table 136 * and frees up the memory space it occupied (except for 137 * the space in the Hash_Table structure). 138 * 139 * Results: 140 * None. 141 * 142 * Side Effects: 143 * Lots of memory is freed up. 144 * 145 *--------------------------------------------------------- 146 */ 147 148 void 149 Hash_DeleteTable(Hash_Table *t) 150 { 151 struct Hash_Entry **hp, *h, *nexth; 152 int i; 153 154 nexth = NULL; 155 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 156 for (h = *hp++; h != NULL; h = nexth) { 157 nexth = h->next; 158 free((char *)h); 159 } 160 } 161 free((char *)t->bucketPtr); 162 163 /* 164 * Set up the hash table to cause memory faults on any future access 165 * attempts until re-initialization. 166 */ 167 t->bucketPtr = NULL; 168 } 169 170 /* 171 *--------------------------------------------------------- 172 * 173 * Hash_FindEntry -- 174 * 175 * Searches a hash table for an entry corresponding to key. 176 * 177 * Input: 178 * t Hash table to search. 179 * key A hash key. 180 * 181 * Results: 182 * The return value is a pointer to the entry for key, 183 * if key was present in the table. If key was not 184 * present, NULL is returned. 185 * 186 * Side Effects: 187 * None. 188 * 189 *--------------------------------------------------------- 190 */ 191 192 Hash_Entry * 193 Hash_FindEntry(Hash_Table *t, char *key) 194 { 195 Hash_Entry *e; 196 unsigned h; 197 char *p; 198 199 for (h = 0, p = key; *p;) 200 h = (h << 5) - h + *p++; 201 p = key; 202 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 203 if (e->namehash == h && strcmp(e->name, p) == 0) 204 return (e); 205 return (NULL); 206 } 207 208 /* 209 *--------------------------------------------------------- 210 * 211 * Hash_CreateEntry -- 212 * 213 * Searches a hash table for an entry corresponding to 214 * key. If no entry is found, then one is created. 215 * 216 * Input: 217 * t Hash table to search. 218 * key A hash key. 219 * newPtr Filled in with 1 if new entry created, 0 otherwise. 220 * 221 * Results: 222 * The return value is a pointer to the entry. If *newPtr 223 * isn't NULL, then *newPtr is filled in with TRUE if a 224 * new entry was created, and FALSE if an entry already existed 225 * with the given key. 226 * 227 * Side Effects: 228 * Memory may be allocated, and the hash buckets may be modified. 229 *--------------------------------------------------------- 230 */ 231 232 Hash_Entry * 233 Hash_CreateEntry(Hash_Table *t, char *key, int *newPtr) 234 { 235 Hash_Entry *e; 236 unsigned h; 237 char *p; 238 int keylen; 239 struct Hash_Entry **hp; 240 241 /* 242 * Hash the key. As a side effect, save the length (strlen) of the 243 * key in case we need to create the entry. 244 */ 245 for (h = 0, p = key; *p;) 246 h = (h << 5) - h + *p++; 247 keylen = p - key; 248 p = key; 249 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 250 if (e->namehash == h && strcmp(e->name, p) == 0) { 251 if (newPtr != NULL) 252 *newPtr = 0; 253 return (e); 254 } 255 } 256 257 /* 258 * The desired entry isn't there. Before allocating a new entry, 259 * expand the table if necessary (and this changes the resulting 260 * bucket chain). 261 */ 262 if (t->numEntries >= rebuildLimit * t->size) 263 RebuildTable(t); 264 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 265 hp = &t->bucketPtr[h & t->mask]; 266 e->next = *hp; 267 *hp = e; 268 e->clientData = NULL; 269 e->namehash = h; 270 (void) strcpy(e->name, p); 271 t->numEntries++; 272 273 if (newPtr != NULL) 274 *newPtr = 1; 275 return (e); 276 } 277 278 /* 279 *--------------------------------------------------------- 280 * 281 * Hash_DeleteEntry -- 282 * 283 * Delete the given hash table entry and free memory associated with 284 * it. 285 * 286 * Results: 287 * None. 288 * 289 * Side Effects: 290 * Hash chain that entry lives in is modified and memory is freed. 291 * 292 *--------------------------------------------------------- 293 */ 294 295 void 296 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e) 297 { 298 Hash_Entry **hp, *p; 299 300 if (e == NULL) 301 return; 302 for (hp = &t->bucketPtr[e->namehash & t->mask]; 303 (p = *hp) != NULL; hp = &p->next) { 304 if (p == e) { 305 *hp = p->next; 306 free((char *)p); 307 t->numEntries--; 308 return; 309 } 310 } 311 (void)write(2, "bad call to Hash_DeleteEntry\n", 29); 312 abort(); 313 } 314 315 /* 316 *--------------------------------------------------------- 317 * 318 * Hash_EnumFirst -- 319 * This procedure sets things up for a complete search 320 * of all entries recorded in the hash table. 321 * 322 * Input: 323 * t Table to be searched. 324 * searchPtr Area in which to keep state about search. 325 * 326 * Results: 327 * The return value is the address of the first entry in 328 * the hash table, or NULL if the table is empty. 329 * 330 * Side Effects: 331 * The information in searchPtr is initialized so that successive 332 * calls to Hash_Next will return successive HashEntry's 333 * from the table. 334 * 335 *--------------------------------------------------------- 336 */ 337 338 Hash_Entry * 339 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr) 340 { 341 342 searchPtr->tablePtr = t; 343 searchPtr->nextIndex = 0; 344 searchPtr->hashEntryPtr = NULL; 345 return Hash_EnumNext(searchPtr); 346 } 347 348 /* 349 *--------------------------------------------------------- 350 * 351 * Hash_EnumNext -- 352 * This procedure returns successive entries in the hash table. 353 * 354 * Results: 355 * The return value is a pointer to the next HashEntry 356 * in the table, or NULL when the end of the table is 357 * reached. 358 * 359 * Side Effects: 360 * The information in searchPtr is modified to advance to the 361 * next entry. 362 * 363 *--------------------------------------------------------- 364 */ 365 366 Hash_Entry * 367 Hash_EnumNext(Hash_Search *searchPtr) 368 { 369 Hash_Entry *e; 370 Hash_Table *t = searchPtr->tablePtr; 371 372 /* 373 * The hashEntryPtr field points to the most recently returned 374 * entry, or is nil if we are starting up. If not nil, we have 375 * to start at the next one in the chain. 376 */ 377 e = searchPtr->hashEntryPtr; 378 if (e != NULL) 379 e = e->next; 380 /* 381 * If the chain ran out, or if we are starting up, we need to 382 * find the next nonempty chain. 383 */ 384 while (e == NULL) { 385 if (searchPtr->nextIndex >= t->size) 386 return (NULL); 387 e = t->bucketPtr[searchPtr->nextIndex++]; 388 } 389 searchPtr->hashEntryPtr = e; 390 return (e); 391 } 392 393 /* 394 *--------------------------------------------------------- 395 * 396 * RebuildTable -- 397 * This local routine makes a new hash table that 398 * is larger than the old one. 399 * 400 * Results: 401 * None. 402 * 403 * Side Effects: 404 * The entire hash table is moved, so any bucket numbers 405 * from the old table are invalid. 406 * 407 *--------------------------------------------------------- 408 */ 409 410 static void 411 RebuildTable(Hash_Table *t) 412 { 413 Hash_Entry *e, *next, **hp, **xp; 414 int i, mask; 415 Hash_Entry **oldhp; 416 int oldsize; 417 418 next = NULL; 419 oldhp = t->bucketPtr; 420 oldsize = i = t->size; 421 i <<= 1; 422 t->size = i; 423 t->mask = mask = i - 1; 424 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 425 while (--i >= 0) 426 *hp++ = NULL; 427 for (hp = oldhp, i = oldsize; --i >= 0;) { 428 for (e = *hp++; e != NULL; e = next) { 429 next = e->next; 430 xp = &t->bucketPtr[e->namehash & mask]; 431 e->next = *xp; 432 *xp = e; 433 } 434 } 435 free((char *)oldhp); 436 } 437