1 /* $NetBSD: hash.c,v 1.6 1996/11/06 17:59:06 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 #ifndef lint 42 #if 0 43 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93"; 44 #else 45 static char rcsid[] = "$NetBSD: hash.c,v 1.6 1996/11/06 17:59:06 christos Exp $"; 46 #endif 47 #endif /* not lint */ 48 49 /* hash.c -- 50 * 51 * This module contains routines to manipulate a hash table. 52 * See hash.h for a definition of the structure of the hash 53 * table. Hash tables grow automatically as the amount of 54 * information increases. 55 */ 56 #include "sprite.h" 57 #include "make.h" 58 #include "hash.h" 59 60 /* 61 * Forward references to local procedures that are used before they're 62 * defined: 63 */ 64 65 static void RebuildTable __P((Hash_Table *)); 66 67 /* 68 * The following defines the ratio of # entries to # buckets 69 * at which we rebuild the table to make it larger. 70 */ 71 72 #define rebuildLimit 8 73 74 /* 75 *--------------------------------------------------------- 76 * 77 * Hash_InitTable -- 78 * 79 * This routine just sets up the hash table. 80 * 81 * Results: 82 * None. 83 * 84 * Side Effects: 85 * Memory is allocated for the initial bucket area. 86 * 87 *--------------------------------------------------------- 88 */ 89 90 void 91 Hash_InitTable(t, numBuckets) 92 register Hash_Table *t; /* Structure to use to hold table. */ 93 int numBuckets; /* How many buckets to create for starters. 94 * This number is rounded up to a power of 95 * two. If <= 0, a reasonable default is 96 * chosen. The table will grow in size later 97 * as needed. */ 98 { 99 register int i; 100 register struct Hash_Entry **hp; 101 102 /* 103 * Round up the size to a power of two. 104 */ 105 if (numBuckets <= 0) 106 i = 16; 107 else { 108 for (i = 2; i < numBuckets; i <<= 1) 109 continue; 110 } 111 t->numEntries = 0; 112 t->size = i; 113 t->mask = i - 1; 114 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 115 while (--i >= 0) 116 *hp++ = NULL; 117 } 118 119 /* 120 *--------------------------------------------------------- 121 * 122 * Hash_DeleteTable -- 123 * 124 * This routine removes everything from a hash table 125 * and frees up the memory space it occupied (except for 126 * the space in the Hash_Table structure). 127 * 128 * Results: 129 * None. 130 * 131 * Side Effects: 132 * Lots of memory is freed up. 133 * 134 *--------------------------------------------------------- 135 */ 136 137 void 138 Hash_DeleteTable(t) 139 Hash_Table *t; 140 { 141 register struct Hash_Entry **hp, *h, *nexth = NULL; 142 register int i; 143 144 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 145 for (h = *hp++; h != NULL; h = nexth) { 146 nexth = h->next; 147 free((char *)h); 148 } 149 } 150 free((char *)t->bucketPtr); 151 152 /* 153 * Set up the hash table to cause memory faults on any future access 154 * attempts until re-initialization. 155 */ 156 t->bucketPtr = NULL; 157 } 158 159 /* 160 *--------------------------------------------------------- 161 * 162 * Hash_FindEntry -- 163 * 164 * Searches a hash table for an entry corresponding to key. 165 * 166 * Results: 167 * The return value is a pointer to the entry for key, 168 * if key was present in the table. If key was not 169 * present, NULL is returned. 170 * 171 * Side Effects: 172 * None. 173 * 174 *--------------------------------------------------------- 175 */ 176 177 Hash_Entry * 178 Hash_FindEntry(t, key) 179 Hash_Table *t; /* Hash table to search. */ 180 char *key; /* A hash key. */ 181 { 182 register Hash_Entry *e; 183 register unsigned h; 184 register char *p; 185 186 for (h = 0, p = key; *p;) 187 h = (h << 5) - h + *p++; 188 p = key; 189 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 190 if (e->namehash == h && strcmp(e->name, p) == 0) 191 return (e); 192 return (NULL); 193 } 194 195 /* 196 *--------------------------------------------------------- 197 * 198 * Hash_CreateEntry -- 199 * 200 * Searches a hash table for an entry corresponding to 201 * key. If no entry is found, then one is created. 202 * 203 * Results: 204 * The return value is a pointer to the entry. If *newPtr 205 * isn't NULL, then *newPtr is filled in with TRUE if a 206 * new entry was created, and FALSE if an entry already existed 207 * with the given key. 208 * 209 * Side Effects: 210 * Memory may be allocated, and the hash buckets may be modified. 211 *--------------------------------------------------------- 212 */ 213 214 Hash_Entry * 215 Hash_CreateEntry(t, key, newPtr) 216 register Hash_Table *t; /* Hash table to search. */ 217 char *key; /* A hash key. */ 218 Boolean *newPtr; /* Filled in with TRUE if new entry created, 219 * FALSE otherwise. */ 220 { 221 register Hash_Entry *e; 222 register unsigned h; 223 register char *p; 224 int keylen; 225 struct Hash_Entry **hp; 226 227 /* 228 * Hash the key. As a side effect, save the length (strlen) of the 229 * key in case we need to create the entry. 230 */ 231 for (h = 0, p = key; *p;) 232 h = (h << 5) - h + *p++; 233 keylen = p - key; 234 p = key; 235 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 236 if (e->namehash == h && strcmp(e->name, p) == 0) { 237 if (newPtr != NULL) 238 *newPtr = FALSE; 239 return (e); 240 } 241 } 242 243 /* 244 * The desired entry isn't there. Before allocating a new entry, 245 * expand the table if necessary (and this changes the resulting 246 * bucket chain). 247 */ 248 if (t->numEntries >= rebuildLimit * t->size) 249 RebuildTable(t); 250 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 251 hp = &t->bucketPtr[h & t->mask]; 252 e->next = *hp; 253 *hp = e; 254 e->clientData = NULL; 255 e->namehash = h; 256 (void) strcpy(e->name, p); 257 t->numEntries++; 258 259 if (newPtr != NULL) 260 *newPtr = TRUE; 261 return (e); 262 } 263 264 /* 265 *--------------------------------------------------------- 266 * 267 * Hash_DeleteEntry -- 268 * 269 * Delete the given hash table entry and free memory associated with 270 * it. 271 * 272 * Results: 273 * None. 274 * 275 * Side Effects: 276 * Hash chain that entry lives in is modified and memory is freed. 277 * 278 *--------------------------------------------------------- 279 */ 280 281 void 282 Hash_DeleteEntry(t, e) 283 Hash_Table *t; 284 Hash_Entry *e; 285 { 286 register Hash_Entry **hp, *p; 287 288 if (e == NULL) 289 return; 290 for (hp = &t->bucketPtr[e->namehash & t->mask]; 291 (p = *hp) != NULL; hp = &p->next) { 292 if (p == e) { 293 *hp = p->next; 294 free((char *)p); 295 t->numEntries--; 296 return; 297 } 298 } 299 (void) write(2, "bad call to Hash_DeleteEntry\n", 29); 300 abort(); 301 } 302 303 /* 304 *--------------------------------------------------------- 305 * 306 * Hash_EnumFirst -- 307 * This procedure sets things up for a complete search 308 * of all entries recorded in the hash table. 309 * 310 * Results: 311 * The return value is the address of the first entry in 312 * the hash table, or NULL if the table is empty. 313 * 314 * Side Effects: 315 * The information in searchPtr is initialized so that successive 316 * calls to Hash_Next will return successive HashEntry's 317 * from the table. 318 * 319 *--------------------------------------------------------- 320 */ 321 322 Hash_Entry * 323 Hash_EnumFirst(t, searchPtr) 324 Hash_Table *t; /* Table to be searched. */ 325 register Hash_Search *searchPtr;/* Area in which to keep state 326 * about search.*/ 327 { 328 searchPtr->tablePtr = t; 329 searchPtr->nextIndex = 0; 330 searchPtr->hashEntryPtr = NULL; 331 return Hash_EnumNext(searchPtr); 332 } 333 334 /* 335 *--------------------------------------------------------- 336 * 337 * Hash_EnumNext -- 338 * This procedure returns successive entries in the hash table. 339 * 340 * Results: 341 * The return value is a pointer to the next HashEntry 342 * in the table, or NULL when the end of the table is 343 * reached. 344 * 345 * Side Effects: 346 * The information in searchPtr is modified to advance to the 347 * next entry. 348 * 349 *--------------------------------------------------------- 350 */ 351 352 Hash_Entry * 353 Hash_EnumNext(searchPtr) 354 register Hash_Search *searchPtr; /* Area used to keep state about 355 search. */ 356 { 357 register Hash_Entry *e; 358 Hash_Table *t = searchPtr->tablePtr; 359 360 /* 361 * The hashEntryPtr field points to the most recently returned 362 * entry, or is nil if we are starting up. If not nil, we have 363 * to start at the next one in the chain. 364 */ 365 e = searchPtr->hashEntryPtr; 366 if (e != NULL) 367 e = e->next; 368 /* 369 * If the chain ran out, or if we are starting up, we need to 370 * find the next nonempty chain. 371 */ 372 while (e == NULL) { 373 if (searchPtr->nextIndex >= t->size) 374 return (NULL); 375 e = t->bucketPtr[searchPtr->nextIndex++]; 376 } 377 searchPtr->hashEntryPtr = e; 378 return (e); 379 } 380 381 /* 382 *--------------------------------------------------------- 383 * 384 * RebuildTable -- 385 * This local routine makes a new hash table that 386 * is larger than the old one. 387 * 388 * Results: 389 * None. 390 * 391 * Side Effects: 392 * The entire hash table is moved, so any bucket numbers 393 * from the old table are invalid. 394 * 395 *--------------------------------------------------------- 396 */ 397 398 static void 399 RebuildTable(t) 400 register Hash_Table *t; 401 { 402 register Hash_Entry *e, *next = NULL, **hp, **xp; 403 register int i, mask; 404 register Hash_Entry **oldhp; 405 int oldsize; 406 407 oldhp = t->bucketPtr; 408 oldsize = i = t->size; 409 i <<= 1; 410 t->size = i; 411 t->mask = mask = i - 1; 412 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 413 while (--i >= 0) 414 *hp++ = NULL; 415 for (hp = oldhp, i = oldsize; --i >= 0;) { 416 for (e = *hp++; e != NULL; e = next) { 417 next = e->next; 418 xp = &t->bucketPtr[e->namehash & mask]; 419 e->next = *xp; 420 *xp = e; 421 } 422 } 423 free((char *)oldhp); 424 } 425