1 /* $NetBSD: hash.c,v 1.9 2000/06/11 07:54:32 mycroft 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 1.9 2000/06/11 07:54:32 mycroft 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 1.9 2000/06/11 07:54:32 mycroft Exp $"); 50 #endif 51 #endif /* not lint */ 52 #endif 53 54 /* hash.c -- 55 * 56 * This module contains routines to manipulate a hash table. 57 * See hash.h for a definition of the structure of the hash 58 * table. Hash tables grow automatically as the amount of 59 * information increases. 60 */ 61 #include "sprite.h" 62 #include "make.h" 63 #include "hash.h" 64 65 /* 66 * Forward references to local procedures that are used before they're 67 * defined: 68 */ 69 70 static void RebuildTable __P((Hash_Table *)); 71 72 /* 73 * The following defines the ratio of # entries to # buckets 74 * at which we rebuild the table to make it larger. 75 */ 76 77 #define rebuildLimit 3 78 79 /* 80 *--------------------------------------------------------- 81 * 82 * Hash_InitTable -- 83 * 84 * This routine just sets up the hash table. 85 * 86 * Results: 87 * None. 88 * 89 * Side Effects: 90 * Memory is allocated for the initial bucket area. 91 * 92 *--------------------------------------------------------- 93 */ 94 95 void 96 Hash_InitTable(t, numBuckets) 97 register Hash_Table *t; /* Structure to use to hold table. */ 98 int numBuckets; /* How many buckets to create for starters. 99 * This number is rounded up to a power of 100 * two. If <= 0, a reasonable default is 101 * chosen. The table will grow in size later 102 * as needed. */ 103 { 104 register int i; 105 register struct Hash_Entry **hp; 106 107 /* 108 * Round up the size to a power of two. 109 */ 110 if (numBuckets <= 0) 111 i = 16; 112 else { 113 for (i = 2; i < numBuckets; i <<= 1) 114 continue; 115 } 116 t->numEntries = 0; 117 t->size = i; 118 t->mask = i - 1; 119 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 120 while (--i >= 0) 121 *hp++ = NULL; 122 } 123 124 /* 125 *--------------------------------------------------------- 126 * 127 * Hash_DeleteTable -- 128 * 129 * This routine removes everything from a hash table 130 * and frees up the memory space it occupied (except for 131 * the space in the Hash_Table structure). 132 * 133 * Results: 134 * None. 135 * 136 * Side Effects: 137 * Lots of memory is freed up. 138 * 139 *--------------------------------------------------------- 140 */ 141 142 void 143 Hash_DeleteTable(t) 144 Hash_Table *t; 145 { 146 register struct Hash_Entry **hp, *h, *nexth = NULL; 147 register int i; 148 149 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 150 for (h = *hp++; h != NULL; h = nexth) { 151 nexth = h->next; 152 free((char *)h); 153 } 154 } 155 free((char *)t->bucketPtr); 156 157 /* 158 * Set up the hash table to cause memory faults on any future access 159 * attempts until re-initialization. 160 */ 161 t->bucketPtr = NULL; 162 } 163 164 /* 165 *--------------------------------------------------------- 166 * 167 * Hash_FindEntry -- 168 * 169 * Searches a hash table for an entry corresponding to key. 170 * 171 * Results: 172 * The return value is a pointer to the entry for key, 173 * if key was present in the table. If key was not 174 * present, NULL is returned. 175 * 176 * Side Effects: 177 * None. 178 * 179 *--------------------------------------------------------- 180 */ 181 182 Hash_Entry * 183 Hash_FindEntry(t, key) 184 Hash_Table *t; /* Hash table to search. */ 185 char *key; /* A hash key. */ 186 { 187 register Hash_Entry *e; 188 register unsigned h; 189 register char *p; 190 191 for (h = 0, p = key; *p;) 192 h = (h << 5) - h + *p++; 193 p = key; 194 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 195 if (e->namehash == h && strcmp(e->name, p) == 0) 196 return (e); 197 return (NULL); 198 } 199 200 /* 201 *--------------------------------------------------------- 202 * 203 * Hash_CreateEntry -- 204 * 205 * Searches a hash table for an entry corresponding to 206 * key. If no entry is found, then one is created. 207 * 208 * Results: 209 * The return value is a pointer to the entry. If *newPtr 210 * isn't NULL, then *newPtr is filled in with TRUE if a 211 * new entry was created, and FALSE if an entry already existed 212 * with the given key. 213 * 214 * Side Effects: 215 * Memory may be allocated, and the hash buckets may be modified. 216 *--------------------------------------------------------- 217 */ 218 219 Hash_Entry * 220 Hash_CreateEntry(t, key, newPtr) 221 register Hash_Table *t; /* Hash table to search. */ 222 char *key; /* A hash key. */ 223 Boolean *newPtr; /* Filled in with TRUE if new entry created, 224 * FALSE otherwise. */ 225 { 226 register Hash_Entry *e; 227 register unsigned h; 228 register char *p; 229 int keylen; 230 struct Hash_Entry **hp; 231 232 /* 233 * Hash the key. As a side effect, save the length (strlen) of the 234 * key in case we need to create the entry. 235 */ 236 for (h = 0, p = key; *p;) 237 h = (h << 5) - h + *p++; 238 keylen = p - key; 239 p = key; 240 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 241 if (e->namehash == h && strcmp(e->name, p) == 0) { 242 if (newPtr != NULL) 243 *newPtr = FALSE; 244 return (e); 245 } 246 } 247 248 /* 249 * The desired entry isn't there. Before allocating a new entry, 250 * expand the table if necessary (and this changes the resulting 251 * bucket chain). 252 */ 253 if (t->numEntries >= rebuildLimit * t->size) 254 RebuildTable(t); 255 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 256 hp = &t->bucketPtr[h & t->mask]; 257 e->next = *hp; 258 *hp = e; 259 e->clientData = NULL; 260 e->namehash = h; 261 (void) strcpy(e->name, p); 262 t->numEntries++; 263 264 if (newPtr != NULL) 265 *newPtr = TRUE; 266 return (e); 267 } 268 269 /* 270 *--------------------------------------------------------- 271 * 272 * Hash_DeleteEntry -- 273 * 274 * Delete the given hash table entry and free memory associated with 275 * it. 276 * 277 * Results: 278 * None. 279 * 280 * Side Effects: 281 * Hash chain that entry lives in is modified and memory is freed. 282 * 283 *--------------------------------------------------------- 284 */ 285 286 void 287 Hash_DeleteEntry(t, e) 288 Hash_Table *t; 289 Hash_Entry *e; 290 { 291 register Hash_Entry **hp, *p; 292 293 if (e == NULL) 294 return; 295 for (hp = &t->bucketPtr[e->namehash & t->mask]; 296 (p = *hp) != NULL; hp = &p->next) { 297 if (p == e) { 298 *hp = p->next; 299 free((char *)p); 300 t->numEntries--; 301 return; 302 } 303 } 304 (void) write(2, "bad call to Hash_DeleteEntry\n", 29); 305 abort(); 306 } 307 308 /* 309 *--------------------------------------------------------- 310 * 311 * Hash_EnumFirst -- 312 * This procedure sets things up for a complete search 313 * of all entries recorded in the hash table. 314 * 315 * Results: 316 * The return value is the address of the first entry in 317 * the hash table, or NULL if the table is empty. 318 * 319 * Side Effects: 320 * The information in searchPtr is initialized so that successive 321 * calls to Hash_Next will return successive HashEntry's 322 * from the table. 323 * 324 *--------------------------------------------------------- 325 */ 326 327 Hash_Entry * 328 Hash_EnumFirst(t, searchPtr) 329 Hash_Table *t; /* Table to be searched. */ 330 register Hash_Search *searchPtr;/* Area in which to keep state 331 * about search.*/ 332 { 333 searchPtr->tablePtr = t; 334 searchPtr->nextIndex = 0; 335 searchPtr->hashEntryPtr = NULL; 336 return Hash_EnumNext(searchPtr); 337 } 338 339 /* 340 *--------------------------------------------------------- 341 * 342 * Hash_EnumNext -- 343 * This procedure returns successive entries in the hash table. 344 * 345 * Results: 346 * The return value is a pointer to the next HashEntry 347 * in the table, or NULL when the end of the table is 348 * reached. 349 * 350 * Side Effects: 351 * The information in searchPtr is modified to advance to the 352 * next entry. 353 * 354 *--------------------------------------------------------- 355 */ 356 357 Hash_Entry * 358 Hash_EnumNext(searchPtr) 359 register Hash_Search *searchPtr; /* Area used to keep state about 360 search. */ 361 { 362 register Hash_Entry *e; 363 Hash_Table *t = searchPtr->tablePtr; 364 365 /* 366 * The hashEntryPtr field points to the most recently returned 367 * entry, or is nil if we are starting up. If not nil, we have 368 * to start at the next one in the chain. 369 */ 370 e = searchPtr->hashEntryPtr; 371 if (e != NULL) 372 e = e->next; 373 /* 374 * If the chain ran out, or if we are starting up, we need to 375 * find the next nonempty chain. 376 */ 377 while (e == NULL) { 378 if (searchPtr->nextIndex >= t->size) 379 return (NULL); 380 e = t->bucketPtr[searchPtr->nextIndex++]; 381 } 382 searchPtr->hashEntryPtr = e; 383 return (e); 384 } 385 386 /* 387 *--------------------------------------------------------- 388 * 389 * RebuildTable -- 390 * This local routine makes a new hash table that 391 * is larger than the old one. 392 * 393 * Results: 394 * None. 395 * 396 * Side Effects: 397 * The entire hash table is moved, so any bucket numbers 398 * from the old table are invalid. 399 * 400 *--------------------------------------------------------- 401 */ 402 403 static void 404 RebuildTable(t) 405 register Hash_Table *t; 406 { 407 register Hash_Entry *e, *next = NULL, **hp, **xp; 408 register int i, mask; 409 register Hash_Entry **oldhp; 410 int oldsize; 411 412 oldhp = t->bucketPtr; 413 oldsize = i = t->size; 414 i <<= 1; 415 t->size = i; 416 t->mask = mask = i - 1; 417 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 418 while (--i >= 0) 419 *hp++ = NULL; 420 for (hp = oldhp, i = oldsize; --i >= 0;) { 421 for (e = *hp++; e != NULL; e = next) { 422 next = e->next; 423 xp = &t->bucketPtr[e->namehash & mask]; 424 e->next = *xp; 425 *xp = e; 426 } 427 } 428 free((char *)oldhp); 429 } 430