1 /* 2 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. 3 * Copyright (c) 1988, 1989 by Adam de Boor 4 * Copyright (c) 1989 by Berkeley Softworks 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. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #ifndef lint 40 static char sccsid[] = "@(#)hash.c 5.5 (Berkeley) 12/28/90"; 41 #endif /* not lint */ 42 43 /* hash.c -- 44 * 45 * This module contains routines to manipulate a hash table. 46 * See hash.h for a definition of the structure of the hash 47 * table. Hash tables grow automatically as the amount of 48 * information increases. 49 */ 50 51 #include "sprite.h" 52 #include "hash.h" 53 54 /* 55 * Forward references to local procedures that are used before they're 56 * defined: 57 */ 58 59 static void RebuildTable(); 60 61 /* 62 * The following defines the ratio of # entries to # buckets 63 * at which we rebuild the table to make it larger. 64 */ 65 66 #define rebuildLimit 8 67 68 /* 69 *--------------------------------------------------------- 70 * 71 * Hash_InitTable -- 72 * 73 * This routine just sets up the hash table. 74 * 75 * Results: 76 * None. 77 * 78 * Side Effects: 79 * Memory is allocated for the initial bucket area. 80 * 81 *--------------------------------------------------------- 82 */ 83 84 void 85 Hash_InitTable(t, numBuckets) 86 register Hash_Table *t; /* Structure to use to hold table. */ 87 int numBuckets; /* How many buckets to create for starters. 88 * This number is rounded up to a power of 89 * two. If <= 0, a reasonable default is 90 * chosen. The table will grow in size later 91 * as needed. */ 92 { 93 register int i; 94 register struct Hash_Entry **hp; 95 96 /* 97 * Round up the size to a power of two. 98 */ 99 if (numBuckets <= 0) 100 i = 16; 101 else { 102 for (i = 2; i < numBuckets; i <<= 1) 103 /* void */ ; 104 } 105 t->numEntries = 0; 106 t->size = i; 107 t->mask = i - 1; 108 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 109 while (--i >= 0) 110 *hp++ = NULL; 111 } 112 113 /* 114 *--------------------------------------------------------- 115 * 116 * Hash_DeleteTable -- 117 * 118 * This routine removes everything from a hash table 119 * and frees up the memory space it occupied (except for 120 * the space in the Hash_Table structure). 121 * 122 * Results: 123 * None. 124 * 125 * Side Effects: 126 * Lots of memory is freed up. 127 * 128 *--------------------------------------------------------- 129 */ 130 131 void 132 Hash_DeleteTable(t) 133 Hash_Table *t; 134 { 135 register struct Hash_Entry **hp, *h, *nexth; 136 register int i; 137 138 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 139 for (h = *hp++; h != NULL; h = nexth) { 140 nexth = h->next; 141 free((char *)h); 142 } 143 } 144 free((char *)t->bucketPtr); 145 146 /* 147 * Set up the hash table to cause memory faults on any future access 148 * attempts until re-initialization. 149 */ 150 t->bucketPtr = NULL; 151 } 152 153 /* 154 *--------------------------------------------------------- 155 * 156 * Hash_FindEntry -- 157 * 158 * Searches a hash table for an entry corresponding to key. 159 * 160 * Results: 161 * The return value is a pointer to the entry for key, 162 * if key was present in the table. If key was not 163 * present, NULL is returned. 164 * 165 * Side Effects: 166 * None. 167 * 168 *--------------------------------------------------------- 169 */ 170 171 Hash_Entry * 172 Hash_FindEntry(t, key) 173 Hash_Table *t; /* Hash table to search. */ 174 char *key; /* A hash key. */ 175 { 176 register Hash_Entry *e; 177 register unsigned h; 178 register char *p; 179 180 for (h = 0, p = key; *p;) 181 h = (h << 5) - h + *p++; 182 p = key; 183 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 184 if (e->namehash == h && strcmp(e->name, p) == 0) 185 return (e); 186 return (NULL); 187 } 188 189 /* 190 *--------------------------------------------------------- 191 * 192 * Hash_CreateEntry -- 193 * 194 * Searches a hash table for an entry corresponding to 195 * key. If no entry is found, then one is created. 196 * 197 * Results: 198 * The return value is a pointer to the entry. If *newPtr 199 * isn't NULL, then *newPtr is filled in with TRUE if a 200 * new entry was created, and FALSE if an entry already existed 201 * with the given key. 202 * 203 * Side Effects: 204 * Memory may be allocated, and the hash buckets may be modified. 205 *--------------------------------------------------------- 206 */ 207 208 Hash_Entry * 209 Hash_CreateEntry(t, key, newPtr) 210 register Hash_Table *t; /* Hash table to search. */ 211 char *key; /* A hash key. */ 212 Boolean *newPtr; /* Filled in with TRUE if new entry created, 213 * FALSE otherwise. */ 214 { 215 register Hash_Entry *e; 216 register unsigned h; 217 register char *p; 218 int keylen; 219 struct Hash_Entry **hp; 220 221 /* 222 * Hash the key. As a side effect, save the length (strlen) of the 223 * key in case we need to create the entry. 224 */ 225 for (h = 0, p = key; *p;) 226 h = (h << 5) - h + *p++; 227 keylen = p - key; 228 p = key; 229 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 230 if (e->namehash == h && strcmp(e->name, p) == 0) { 231 if (newPtr != NULL) 232 *newPtr = FALSE; 233 return (e); 234 } 235 } 236 237 /* 238 * The desired entry isn't there. Before allocating a new entry, 239 * expand the table if necessary (and this changes the resulting 240 * bucket chain). 241 */ 242 if (t->numEntries >= rebuildLimit * t->size) 243 RebuildTable(t); 244 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 245 hp = &t->bucketPtr[h & t->mask]; 246 e->next = *hp; 247 *hp = e; 248 e->clientData = NULL; 249 e->namehash = h; 250 (void) strcpy(e->name, p); 251 t->numEntries++; 252 253 if (newPtr != NULL) 254 *newPtr = TRUE; 255 return (e); 256 } 257 258 /* 259 *--------------------------------------------------------- 260 * 261 * Hash_DeleteEntry -- 262 * 263 * Delete the given hash table entry and free memory associated with 264 * it. 265 * 266 * Results: 267 * None. 268 * 269 * Side Effects: 270 * Hash chain that entry lives in is modified and memory is freed. 271 * 272 *--------------------------------------------------------- 273 */ 274 275 void 276 Hash_DeleteEntry(t, e) 277 Hash_Table *t; 278 Hash_Entry *e; 279 { 280 register Hash_Entry **hp, *p; 281 282 if (e == NULL) 283 return; 284 for (hp = &t->bucketPtr[e->namehash & t->mask]; 285 (p = *hp) != NULL; hp = &p->next) { 286 if (p == e) { 287 *hp = p->next; 288 free((char *)p); 289 t->numEntries--; 290 return; 291 } 292 } 293 (void) write(2, "bad call to Hash_DeleteEntry\n", 29); 294 abort(); 295 } 296 297 /* 298 *--------------------------------------------------------- 299 * 300 * Hash_EnumFirst -- 301 * This procedure sets things up for a complete search 302 * of all entries recorded in the hash table. 303 * 304 * Results: 305 * The return value is the address of the first entry in 306 * the hash table, or NULL if the table is empty. 307 * 308 * Side Effects: 309 * The information in searchPtr is initialized so that successive 310 * calls to Hash_Next will return successive HashEntry's 311 * from the table. 312 * 313 *--------------------------------------------------------- 314 */ 315 316 Hash_Entry * 317 Hash_EnumFirst(t, searchPtr) 318 Hash_Table *t; /* Table to be searched. */ 319 register Hash_Search *searchPtr;/* Area in which to keep state 320 * about search.*/ 321 { 322 searchPtr->tablePtr = t; 323 searchPtr->nextIndex = 0; 324 searchPtr->hashEntryPtr = NULL; 325 return Hash_EnumNext(searchPtr); 326 } 327 328 /* 329 *--------------------------------------------------------- 330 * 331 * Hash_EnumNext -- 332 * This procedure returns successive entries in the hash table. 333 * 334 * Results: 335 * The return value is a pointer to the next HashEntry 336 * in the table, or NULL when the end of the table is 337 * reached. 338 * 339 * Side Effects: 340 * The information in searchPtr is modified to advance to the 341 * next entry. 342 * 343 *--------------------------------------------------------- 344 */ 345 346 Hash_Entry * 347 Hash_EnumNext(searchPtr) 348 register Hash_Search *searchPtr; /* Area used to keep state about 349 search. */ 350 { 351 register Hash_Entry *e; 352 Hash_Table *t = searchPtr->tablePtr; 353 354 /* 355 * The hashEntryPtr field points to the most recently returned 356 * entry, or is nil if we are starting up. If not nil, we have 357 * to start at the next one in the chain. 358 */ 359 e = searchPtr->hashEntryPtr; 360 if (e != NULL) 361 e = e->next; 362 /* 363 * If the chain ran out, or if we are starting up, we need to 364 * find the next nonempty chain. 365 */ 366 while (e == NULL) { 367 if (searchPtr->nextIndex >= t->size) 368 return (NULL); 369 e = t->bucketPtr[searchPtr->nextIndex++]; 370 } 371 searchPtr->hashEntryPtr = e; 372 return (e); 373 } 374 375 /* 376 *--------------------------------------------------------- 377 * 378 * RebuildTable -- 379 * This local routine makes a new hash table that 380 * is larger than the old one. 381 * 382 * Results: 383 * None. 384 * 385 * Side Effects: 386 * The entire hash table is moved, so any bucket numbers 387 * from the old table are invalid. 388 * 389 *--------------------------------------------------------- 390 */ 391 392 static void 393 RebuildTable(t) 394 register Hash_Table *t; 395 { 396 register Hash_Entry *e, *next, **hp, **xp; 397 register int i, mask; 398 register Hash_Entry **oldhp; 399 int oldsize; 400 401 oldhp = t->bucketPtr; 402 oldsize = i = t->size; 403 i <<= 1; 404 t->size = i; 405 t->mask = mask = i - 1; 406 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 407 while (--i >= 0) 408 *hp++ = NULL; 409 for (hp = oldhp, i = oldsize; --i >= 0;) { 410 for (e = *hp++; e != NULL; e = next) { 411 next = e->next; 412 xp = &t->bucketPtr[e->namehash & mask]; 413 e->next = *xp; 414 *xp = e; 415 } 416 } 417 free((char *)oldhp); 418 } 419