1 /* $NetBSD: hash.c,v 1.7 1997/07/01 21:17:21 christos 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 #include <sys/cdefs.h> 42 #ifndef lint 43 #if 0 44 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93"; 45 #else 46 __RCSID("$NetBSD: hash.c,v 1.7 1997/07/01 21:17:21 christos Exp $"); 47 #endif 48 #endif /* not lint */ 49 50 /* hash.c -- 51 * 52 * This module contains routines to manipulate a hash table. 53 * See hash.h for a definition of the structure of the hash 54 * table. Hash tables grow automatically as the amount of 55 * information increases. 56 */ 57 #include "sprite.h" 58 #include "make.h" 59 #include "hash.h" 60 61 /* 62 * Forward references to local procedures that are used before they're 63 * defined: 64 */ 65 66 static void RebuildTable __P((Hash_Table *)); 67 68 /* 69 * The following defines the ratio of # entries to # buckets 70 * at which we rebuild the table to make it larger. 71 */ 72 73 #define rebuildLimit 8 74 75 /* 76 *--------------------------------------------------------- 77 * 78 * Hash_InitTable -- 79 * 80 * This routine just sets up the hash table. 81 * 82 * Results: 83 * None. 84 * 85 * Side Effects: 86 * Memory is allocated for the initial bucket area. 87 * 88 *--------------------------------------------------------- 89 */ 90 91 void 92 Hash_InitTable(t, numBuckets) 93 register Hash_Table *t; /* Structure to use to hold table. */ 94 int numBuckets; /* How many buckets to create for starters. 95 * This number is rounded up to a power of 96 * two. If <= 0, a reasonable default is 97 * chosen. The table will grow in size later 98 * as needed. */ 99 { 100 register int i; 101 register struct Hash_Entry **hp; 102 103 /* 104 * Round up the size to a power of two. 105 */ 106 if (numBuckets <= 0) 107 i = 16; 108 else { 109 for (i = 2; i < numBuckets; i <<= 1) 110 continue; 111 } 112 t->numEntries = 0; 113 t->size = i; 114 t->mask = i - 1; 115 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 116 while (--i >= 0) 117 *hp++ = NULL; 118 } 119 120 /* 121 *--------------------------------------------------------- 122 * 123 * Hash_DeleteTable -- 124 * 125 * This routine removes everything from a hash table 126 * and frees up the memory space it occupied (except for 127 * the space in the Hash_Table structure). 128 * 129 * Results: 130 * None. 131 * 132 * Side Effects: 133 * Lots of memory is freed up. 134 * 135 *--------------------------------------------------------- 136 */ 137 138 void 139 Hash_DeleteTable(t) 140 Hash_Table *t; 141 { 142 register struct Hash_Entry **hp, *h, *nexth = NULL; 143 register int i; 144 145 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 146 for (h = *hp++; h != NULL; h = nexth) { 147 nexth = h->next; 148 free((char *)h); 149 } 150 } 151 free((char *)t->bucketPtr); 152 153 /* 154 * Set up the hash table to cause memory faults on any future access 155 * attempts until re-initialization. 156 */ 157 t->bucketPtr = NULL; 158 } 159 160 /* 161 *--------------------------------------------------------- 162 * 163 * Hash_FindEntry -- 164 * 165 * Searches a hash table for an entry corresponding to key. 166 * 167 * Results: 168 * The return value is a pointer to the entry for key, 169 * if key was present in the table. If key was not 170 * present, NULL is returned. 171 * 172 * Side Effects: 173 * None. 174 * 175 *--------------------------------------------------------- 176 */ 177 178 Hash_Entry * 179 Hash_FindEntry(t, key) 180 Hash_Table *t; /* Hash table to search. */ 181 char *key; /* A hash key. */ 182 { 183 register Hash_Entry *e; 184 register unsigned h; 185 register char *p; 186 187 for (h = 0, p = key; *p;) 188 h = (h << 5) - h + *p++; 189 p = key; 190 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 191 if (e->namehash == h && strcmp(e->name, p) == 0) 192 return (e); 193 return (NULL); 194 } 195 196 /* 197 *--------------------------------------------------------- 198 * 199 * Hash_CreateEntry -- 200 * 201 * Searches a hash table for an entry corresponding to 202 * key. If no entry is found, then one is created. 203 * 204 * Results: 205 * The return value is a pointer to the entry. If *newPtr 206 * isn't NULL, then *newPtr is filled in with TRUE if a 207 * new entry was created, and FALSE if an entry already existed 208 * with the given key. 209 * 210 * Side Effects: 211 * Memory may be allocated, and the hash buckets may be modified. 212 *--------------------------------------------------------- 213 */ 214 215 Hash_Entry * 216 Hash_CreateEntry(t, key, newPtr) 217 register Hash_Table *t; /* Hash table to search. */ 218 char *key; /* A hash key. */ 219 Boolean *newPtr; /* Filled in with TRUE if new entry created, 220 * FALSE otherwise. */ 221 { 222 register Hash_Entry *e; 223 register unsigned h; 224 register char *p; 225 int keylen; 226 struct Hash_Entry **hp; 227 228 /* 229 * Hash the key. As a side effect, save the length (strlen) of the 230 * key in case we need to create the entry. 231 */ 232 for (h = 0, p = key; *p;) 233 h = (h << 5) - h + *p++; 234 keylen = p - key; 235 p = key; 236 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 237 if (e->namehash == h && strcmp(e->name, p) == 0) { 238 if (newPtr != NULL) 239 *newPtr = FALSE; 240 return (e); 241 } 242 } 243 244 /* 245 * The desired entry isn't there. Before allocating a new entry, 246 * expand the table if necessary (and this changes the resulting 247 * bucket chain). 248 */ 249 if (t->numEntries >= rebuildLimit * t->size) 250 RebuildTable(t); 251 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 252 hp = &t->bucketPtr[h & t->mask]; 253 e->next = *hp; 254 *hp = e; 255 e->clientData = NULL; 256 e->namehash = h; 257 (void) strcpy(e->name, p); 258 t->numEntries++; 259 260 if (newPtr != NULL) 261 *newPtr = TRUE; 262 return (e); 263 } 264 265 /* 266 *--------------------------------------------------------- 267 * 268 * Hash_DeleteEntry -- 269 * 270 * Delete the given hash table entry and free memory associated with 271 * it. 272 * 273 * Results: 274 * None. 275 * 276 * Side Effects: 277 * Hash chain that entry lives in is modified and memory is freed. 278 * 279 *--------------------------------------------------------- 280 */ 281 282 void 283 Hash_DeleteEntry(t, e) 284 Hash_Table *t; 285 Hash_Entry *e; 286 { 287 register Hash_Entry **hp, *p; 288 289 if (e == NULL) 290 return; 291 for (hp = &t->bucketPtr[e->namehash & t->mask]; 292 (p = *hp) != NULL; hp = &p->next) { 293 if (p == e) { 294 *hp = p->next; 295 free((char *)p); 296 t->numEntries--; 297 return; 298 } 299 } 300 (void) write(2, "bad call to Hash_DeleteEntry\n", 29); 301 abort(); 302 } 303 304 /* 305 *--------------------------------------------------------- 306 * 307 * Hash_EnumFirst -- 308 * This procedure sets things up for a complete search 309 * of all entries recorded in the hash table. 310 * 311 * Results: 312 * The return value is the address of the first entry in 313 * the hash table, or NULL if the table is empty. 314 * 315 * Side Effects: 316 * The information in searchPtr is initialized so that successive 317 * calls to Hash_Next will return successive HashEntry's 318 * from the table. 319 * 320 *--------------------------------------------------------- 321 */ 322 323 Hash_Entry * 324 Hash_EnumFirst(t, searchPtr) 325 Hash_Table *t; /* Table to be searched. */ 326 register Hash_Search *searchPtr;/* Area in which to keep state 327 * about search.*/ 328 { 329 searchPtr->tablePtr = t; 330 searchPtr->nextIndex = 0; 331 searchPtr->hashEntryPtr = NULL; 332 return Hash_EnumNext(searchPtr); 333 } 334 335 /* 336 *--------------------------------------------------------- 337 * 338 * Hash_EnumNext -- 339 * This procedure returns successive entries in the hash table. 340 * 341 * Results: 342 * The return value is a pointer to the next HashEntry 343 * in the table, or NULL when the end of the table is 344 * reached. 345 * 346 * Side Effects: 347 * The information in searchPtr is modified to advance to the 348 * next entry. 349 * 350 *--------------------------------------------------------- 351 */ 352 353 Hash_Entry * 354 Hash_EnumNext(searchPtr) 355 register Hash_Search *searchPtr; /* Area used to keep state about 356 search. */ 357 { 358 register Hash_Entry *e; 359 Hash_Table *t = searchPtr->tablePtr; 360 361 /* 362 * The hashEntryPtr field points to the most recently returned 363 * entry, or is nil if we are starting up. If not nil, we have 364 * to start at the next one in the chain. 365 */ 366 e = searchPtr->hashEntryPtr; 367 if (e != NULL) 368 e = e->next; 369 /* 370 * If the chain ran out, or if we are starting up, we need to 371 * find the next nonempty chain. 372 */ 373 while (e == NULL) { 374 if (searchPtr->nextIndex >= t->size) 375 return (NULL); 376 e = t->bucketPtr[searchPtr->nextIndex++]; 377 } 378 searchPtr->hashEntryPtr = e; 379 return (e); 380 } 381 382 /* 383 *--------------------------------------------------------- 384 * 385 * RebuildTable -- 386 * This local routine makes a new hash table that 387 * is larger than the old one. 388 * 389 * Results: 390 * None. 391 * 392 * Side Effects: 393 * The entire hash table is moved, so any bucket numbers 394 * from the old table are invalid. 395 * 396 *--------------------------------------------------------- 397 */ 398 399 static void 400 RebuildTable(t) 401 register Hash_Table *t; 402 { 403 register Hash_Entry *e, *next = NULL, **hp, **xp; 404 register int i, mask; 405 register Hash_Entry **oldhp; 406 int oldsize; 407 408 oldhp = t->bucketPtr; 409 oldsize = i = t->size; 410 i <<= 1; 411 t->size = i; 412 t->mask = mask = i - 1; 413 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 414 while (--i >= 0) 415 *hp++ = NULL; 416 for (hp = oldhp, i = oldsize; --i >= 0;) { 417 for (e = *hp++; e != NULL; e = next) { 418 next = e->next; 419 xp = &t->bucketPtr[e->namehash & mask]; 420 e->next = *xp; 421 *xp = e; 422 } 423 } 424 free((char *)oldhp); 425 } 426