hash.c revision 1.3
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[] = "from: @(#)hash.c 5.5 (Berkeley) 12/28/90";*/ 41 static char rcsid[] = "$Id: hash.c,v 1.3 1994/01/13 21:01:49 jtc Exp $"; 42 #endif /* not lint */ 43 44 /* hash.c -- 45 * 46 * This module contains routines to manipulate a hash table. 47 * See hash.h for a definition of the structure of the hash 48 * table. Hash tables grow automatically as the amount of 49 * information increases. 50 */ 51 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include <unistd.h> 55 #include "sprite.h" 56 #include "hash.h" 57 58 /* 59 * Forward references to local procedures that are used before they're 60 * defined: 61 */ 62 63 static void RebuildTable(); 64 65 /* 66 * The following defines the ratio of # entries to # buckets 67 * at which we rebuild the table to make it larger. 68 */ 69 70 #define rebuildLimit 8 71 72 /* 73 *--------------------------------------------------------- 74 * 75 * Hash_InitTable -- 76 * 77 * This routine just sets up the hash table. 78 * 79 * Results: 80 * None. 81 * 82 * Side Effects: 83 * Memory is allocated for the initial bucket area. 84 * 85 *--------------------------------------------------------- 86 */ 87 88 void 89 Hash_InitTable(t, numBuckets) 90 register Hash_Table *t; /* Structure to use to hold table. */ 91 int numBuckets; /* How many buckets to create for starters. 92 * This number is rounded up to a power of 93 * two. If <= 0, a reasonable default is 94 * chosen. The table will grow in size later 95 * as needed. */ 96 { 97 register int i; 98 register struct Hash_Entry **hp; 99 100 /* 101 * Round up the size to a power of two. 102 */ 103 if (numBuckets <= 0) 104 i = 16; 105 else { 106 for (i = 2; i < numBuckets; i <<= 1) 107 /* void */ ; 108 } 109 t->numEntries = 0; 110 t->size = i; 111 t->mask = i - 1; 112 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 113 while (--i >= 0) 114 *hp++ = NULL; 115 } 116 117 /* 118 *--------------------------------------------------------- 119 * 120 * Hash_DeleteTable -- 121 * 122 * This routine removes everything from a hash table 123 * and frees up the memory space it occupied (except for 124 * the space in the Hash_Table structure). 125 * 126 * Results: 127 * None. 128 * 129 * Side Effects: 130 * Lots of memory is freed up. 131 * 132 *--------------------------------------------------------- 133 */ 134 135 void 136 Hash_DeleteTable(t) 137 Hash_Table *t; 138 { 139 register struct Hash_Entry **hp, *h, *nexth; 140 register int i; 141 142 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 143 for (h = *hp++; h != NULL; h = nexth) { 144 nexth = h->next; 145 free((char *)h); 146 } 147 } 148 free((char *)t->bucketPtr); 149 150 /* 151 * Set up the hash table to cause memory faults on any future access 152 * attempts until re-initialization. 153 */ 154 t->bucketPtr = NULL; 155 } 156 157 /* 158 *--------------------------------------------------------- 159 * 160 * Hash_FindEntry -- 161 * 162 * Searches a hash table for an entry corresponding to key. 163 * 164 * Results: 165 * The return value is a pointer to the entry for key, 166 * if key was present in the table. If key was not 167 * present, NULL is returned. 168 * 169 * Side Effects: 170 * None. 171 * 172 *--------------------------------------------------------- 173 */ 174 175 Hash_Entry * 176 Hash_FindEntry(t, key) 177 Hash_Table *t; /* Hash table to search. */ 178 char *key; /* A hash key. */ 179 { 180 register Hash_Entry *e; 181 register unsigned h; 182 register char *p; 183 184 for (h = 0, p = key; *p;) 185 h = (h << 5) - h + *p++; 186 p = key; 187 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 188 if (e->namehash == h && strcmp(e->name, p) == 0) 189 return (e); 190 return (NULL); 191 } 192 193 /* 194 *--------------------------------------------------------- 195 * 196 * Hash_CreateEntry -- 197 * 198 * Searches a hash table for an entry corresponding to 199 * key. If no entry is found, then one is created. 200 * 201 * Results: 202 * The return value is a pointer to the entry. If *newPtr 203 * isn't NULL, then *newPtr is filled in with TRUE if a 204 * new entry was created, and FALSE if an entry already existed 205 * with the given key. 206 * 207 * Side Effects: 208 * Memory may be allocated, and the hash buckets may be modified. 209 *--------------------------------------------------------- 210 */ 211 212 Hash_Entry * 213 Hash_CreateEntry(t, key, newPtr) 214 register Hash_Table *t; /* Hash table to search. */ 215 char *key; /* A hash key. */ 216 Boolean *newPtr; /* Filled in with TRUE if new entry created, 217 * FALSE otherwise. */ 218 { 219 register Hash_Entry *e; 220 register unsigned h; 221 register char *p; 222 int keylen; 223 struct Hash_Entry **hp; 224 225 /* 226 * Hash the key. As a side effect, save the length (strlen) of the 227 * key in case we need to create the entry. 228 */ 229 for (h = 0, p = key; *p;) 230 h = (h << 5) - h + *p++; 231 keylen = p - key; 232 p = key; 233 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 234 if (e->namehash == h && strcmp(e->name, p) == 0) { 235 if (newPtr != NULL) 236 *newPtr = FALSE; 237 return (e); 238 } 239 } 240 241 /* 242 * The desired entry isn't there. Before allocating a new entry, 243 * expand the table if necessary (and this changes the resulting 244 * bucket chain). 245 */ 246 if (t->numEntries >= rebuildLimit * t->size) 247 RebuildTable(t); 248 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 249 hp = &t->bucketPtr[h & t->mask]; 250 e->next = *hp; 251 *hp = e; 252 e->clientData = NULL; 253 e->namehash = h; 254 (void) strcpy(e->name, p); 255 t->numEntries++; 256 257 if (newPtr != NULL) 258 *newPtr = TRUE; 259 return (e); 260 } 261 262 /* 263 *--------------------------------------------------------- 264 * 265 * Hash_DeleteEntry -- 266 * 267 * Delete the given hash table entry and free memory associated with 268 * it. 269 * 270 * Results: 271 * None. 272 * 273 * Side Effects: 274 * Hash chain that entry lives in is modified and memory is freed. 275 * 276 *--------------------------------------------------------- 277 */ 278 279 void 280 Hash_DeleteEntry(t, e) 281 Hash_Table *t; 282 Hash_Entry *e; 283 { 284 register Hash_Entry **hp, *p; 285 286 if (e == NULL) 287 return; 288 for (hp = &t->bucketPtr[e->namehash & t->mask]; 289 (p = *hp) != NULL; hp = &p->next) { 290 if (p == e) { 291 *hp = p->next; 292 free((char *)p); 293 t->numEntries--; 294 return; 295 } 296 } 297 (void) write(2, "bad call to Hash_DeleteEntry\n", 29); 298 abort(); 299 } 300 301 /* 302 *--------------------------------------------------------- 303 * 304 * Hash_EnumFirst -- 305 * This procedure sets things up for a complete search 306 * of all entries recorded in the hash table. 307 * 308 * Results: 309 * The return value is the address of the first entry in 310 * the hash table, or NULL if the table is empty. 311 * 312 * Side Effects: 313 * The information in searchPtr is initialized so that successive 314 * calls to Hash_Next will return successive HashEntry's 315 * from the table. 316 * 317 *--------------------------------------------------------- 318 */ 319 320 Hash_Entry * 321 Hash_EnumFirst(t, searchPtr) 322 Hash_Table *t; /* Table to be searched. */ 323 register Hash_Search *searchPtr;/* Area in which to keep state 324 * about search.*/ 325 { 326 searchPtr->tablePtr = t; 327 searchPtr->nextIndex = 0; 328 searchPtr->hashEntryPtr = NULL; 329 return Hash_EnumNext(searchPtr); 330 } 331 332 /* 333 *--------------------------------------------------------- 334 * 335 * Hash_EnumNext -- 336 * This procedure returns successive entries in the hash table. 337 * 338 * Results: 339 * The return value is a pointer to the next HashEntry 340 * in the table, or NULL when the end of the table is 341 * reached. 342 * 343 * Side Effects: 344 * The information in searchPtr is modified to advance to the 345 * next entry. 346 * 347 *--------------------------------------------------------- 348 */ 349 350 Hash_Entry * 351 Hash_EnumNext(searchPtr) 352 register Hash_Search *searchPtr; /* Area used to keep state about 353 search. */ 354 { 355 register Hash_Entry *e; 356 Hash_Table *t = searchPtr->tablePtr; 357 358 /* 359 * The hashEntryPtr field points to the most recently returned 360 * entry, or is nil if we are starting up. If not nil, we have 361 * to start at the next one in the chain. 362 */ 363 e = searchPtr->hashEntryPtr; 364 if (e != NULL) 365 e = e->next; 366 /* 367 * If the chain ran out, or if we are starting up, we need to 368 * find the next nonempty chain. 369 */ 370 while (e == NULL) { 371 if (searchPtr->nextIndex >= t->size) 372 return (NULL); 373 e = t->bucketPtr[searchPtr->nextIndex++]; 374 } 375 searchPtr->hashEntryPtr = e; 376 return (e); 377 } 378 379 /* 380 *--------------------------------------------------------- 381 * 382 * RebuildTable -- 383 * This local routine makes a new hash table that 384 * is larger than the old one. 385 * 386 * Results: 387 * None. 388 * 389 * Side Effects: 390 * The entire hash table is moved, so any bucket numbers 391 * from the old table are invalid. 392 * 393 *--------------------------------------------------------- 394 */ 395 396 static void 397 RebuildTable(t) 398 register Hash_Table *t; 399 { 400 register Hash_Entry *e, *next, **hp, **xp; 401 register int i, mask; 402 register Hash_Entry **oldhp; 403 int oldsize; 404 405 oldhp = t->bucketPtr; 406 oldsize = i = t->size; 407 i <<= 1; 408 t->size = i; 409 t->mask = mask = i - 1; 410 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 411 while (--i >= 0) 412 *hp++ = NULL; 413 for (hp = oldhp, i = oldsize; --i >= 0;) { 414 for (e = *hp++; e != NULL; e = next) { 415 next = e->next; 416 xp = &t->bucketPtr[e->namehash & mask]; 417 e->next = *xp; 418 *xp = e; 419 } 420 } 421 free((char *)oldhp); 422 } 423
Indexes created Thu Oct 23 22:10:10 GMT 2025