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 /* from: static char sccsid[] = "@(#)hash.c 5.5 (Berkeley) 12/28/90"; */ 41 static char *rcsid = "$Id: hash.c,v 1.4 1994/03/05 00:34:45 cgd 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 #include "sprite.h" 52 #include "make.h" 53 #include "hash.h" 54 55 /* 56 * Forward references to local procedures that are used before they're 57 * defined: 58 */ 59 60 static void RebuildTable __P((Hash_Table *)); 61 62 /* 63 * The following defines the ratio of # entries to # buckets 64 * at which we rebuild the table to make it larger. 65 */ 66 67 #define rebuildLimit 8 68 69 /* 70 *--------------------------------------------------------- 71 * 72 * Hash_InitTable -- 73 * 74 * This routine just sets up the hash table. 75 * 76 * Results: 77 * None. 78 * 79 * Side Effects: 80 * Memory is allocated for the initial bucket area. 81 * 82 *--------------------------------------------------------- 83 */ 84 85 void 86 Hash_InitTable(t, numBuckets) 87 register Hash_Table *t; /* Structure to use to hold table. */ 88 int numBuckets; /* How many buckets to create for starters. 89 * This number is rounded up to a power of 90 * two. If <= 0, a reasonable default is 91 * chosen. The table will grow in size later 92 * as needed. */ 93 { 94 register int i; 95 register struct Hash_Entry **hp; 96 97 /* 98 * Round up the size to a power of two. 99 */ 100 if (numBuckets <= 0) 101 i = 16; 102 else { 103 for (i = 2; i < numBuckets; i <<= 1) 104 continue; 105 } 106 t->numEntries = 0; 107 t->size = i; 108 t->mask = i - 1; 109 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 110 while (--i >= 0) 111 *hp++ = NULL; 112 } 113 114 /* 115 *--------------------------------------------------------- 116 * 117 * Hash_DeleteTable -- 118 * 119 * This routine removes everything from a hash table 120 * and frees up the memory space it occupied (except for 121 * the space in the Hash_Table structure). 122 * 123 * Results: 124 * None. 125 * 126 * Side Effects: 127 * Lots of memory is freed up. 128 * 129 *--------------------------------------------------------- 130 */ 131 132 void 133 Hash_DeleteTable(t) 134 Hash_Table *t; 135 { 136 register struct Hash_Entry **hp, *h, *nexth = NULL; 137 register int i; 138 139 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 140 for (h = *hp++; h != NULL; h = nexth) { 141 nexth = h->next; 142 free((char *)h); 143 } 144 } 145 free((char *)t->bucketPtr); 146 147 /* 148 * Set up the hash table to cause memory faults on any future access 149 * attempts until re-initialization. 150 */ 151 t->bucketPtr = NULL; 152 } 153 154 /* 155 *--------------------------------------------------------- 156 * 157 * Hash_FindEntry -- 158 * 159 * Searches a hash table for an entry corresponding to key. 160 * 161 * Results: 162 * The return value is a pointer to the entry for key, 163 * if key was present in the table. If key was not 164 * present, NULL is returned. 165 * 166 * Side Effects: 167 * None. 168 * 169 *--------------------------------------------------------- 170 */ 171 172 Hash_Entry * 173 Hash_FindEntry(t, key) 174 Hash_Table *t; /* Hash table to search. */ 175 char *key; /* A hash key. */ 176 { 177 register Hash_Entry *e; 178 register unsigned h; 179 register char *p; 180 181 for (h = 0, p = key; *p;) 182 h = (h << 5) - h + *p++; 183 p = key; 184 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 185 if (e->namehash == h && strcmp(e->name, p) == 0) 186 return (e); 187 return (NULL); 188 } 189 190 /* 191 *--------------------------------------------------------- 192 * 193 * Hash_CreateEntry -- 194 * 195 * Searches a hash table for an entry corresponding to 196 * key. If no entry is found, then one is created. 197 * 198 * Results: 199 * The return value is a pointer to the entry. If *newPtr 200 * isn't NULL, then *newPtr is filled in with TRUE if a 201 * new entry was created, and FALSE if an entry already existed 202 * with the given key. 203 * 204 * Side Effects: 205 * Memory may be allocated, and the hash buckets may be modified. 206 *--------------------------------------------------------- 207 */ 208 209 Hash_Entry * 210 Hash_CreateEntry(t, key, newPtr) 211 register Hash_Table *t; /* Hash table to search. */ 212 char *key; /* A hash key. */ 213 Boolean *newPtr; /* Filled in with TRUE if new entry created, 214 * FALSE otherwise. */ 215 { 216 register Hash_Entry *e; 217 register unsigned h; 218 register char *p; 219 int keylen; 220 struct Hash_Entry **hp; 221 222 /* 223 * Hash the key. As a side effect, save the length (strlen) of the 224 * key in case we need to create the entry. 225 */ 226 for (h = 0, p = key; *p;) 227 h = (h << 5) - h + *p++; 228 keylen = p - key; 229 p = key; 230 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 231 if (e->namehash == h && strcmp(e->name, p) == 0) { 232 if (newPtr != NULL) 233 *newPtr = FALSE; 234 return (e); 235 } 236 } 237 238 /* 239 * The desired entry isn't there. Before allocating a new entry, 240 * expand the table if necessary (and this changes the resulting 241 * bucket chain). 242 */ 243 if (t->numEntries >= rebuildLimit * t->size) 244 RebuildTable(t); 245 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 246 hp = &t->bucketPtr[h & t->mask]; 247 e->next = *hp; 248 *hp = e; 249 e->clientData = NULL; 250 e->namehash = h; 251 (void) strcpy(e->name, p); 252 t->numEntries++; 253 254 if (newPtr != NULL) 255 *newPtr = TRUE; 256 return (e); 257 } 258 259 /* 260 *--------------------------------------------------------- 261 * 262 * Hash_DeleteEntry -- 263 * 264 * Delete the given hash table entry and free memory associated with 265 * it. 266 * 267 * Results: 268 * None. 269 * 270 * Side Effects: 271 * Hash chain that entry lives in is modified and memory is freed. 272 * 273 *--------------------------------------------------------- 274 */ 275 276 void 277 Hash_DeleteEntry(t, e) 278 Hash_Table *t; 279 Hash_Entry *e; 280 { 281 register Hash_Entry **hp, *p; 282 283 if (e == NULL) 284 return; 285 for (hp = &t->bucketPtr[e->namehash & t->mask]; 286 (p = *hp) != NULL; hp = &p->next) { 287 if (p == e) { 288 *hp = p->next; 289 free((char *)p); 290 t->numEntries--; 291 return; 292 } 293 } 294 (void) write(2, "bad call to Hash_DeleteEntry\n", 29); 295 abort(); 296 } 297 298 /* 299 *--------------------------------------------------------- 300 * 301 * Hash_EnumFirst -- 302 * This procedure sets things up for a complete search 303 * of all entries recorded in the hash table. 304 * 305 * Results: 306 * The return value is the address of the first entry in 307 * the hash table, or NULL if the table is empty. 308 * 309 * Side Effects: 310 * The information in searchPtr is initialized so that successive 311 * calls to Hash_Next will return successive HashEntry's 312 * from the table. 313 * 314 *--------------------------------------------------------- 315 */ 316 317 Hash_Entry * 318 Hash_EnumFirst(t, searchPtr) 319 Hash_Table *t; /* Table to be searched. */ 320 register Hash_Search *searchPtr;/* Area in which to keep state 321 * about search.*/ 322 { 323 searchPtr->tablePtr = t; 324 searchPtr->nextIndex = 0; 325 searchPtr->hashEntryPtr = NULL; 326 return Hash_EnumNext(searchPtr); 327 } 328 329 /* 330 *--------------------------------------------------------- 331 * 332 * Hash_EnumNext -- 333 * This procedure returns successive entries in the hash table. 334 * 335 * Results: 336 * The return value is a pointer to the next HashEntry 337 * in the table, or NULL when the end of the table is 338 * reached. 339 * 340 * Side Effects: 341 * The information in searchPtr is modified to advance to the 342 * next entry. 343 * 344 *--------------------------------------------------------- 345 */ 346 347 Hash_Entry * 348 Hash_EnumNext(searchPtr) 349 register Hash_Search *searchPtr; /* Area used to keep state about 350 search. */ 351 { 352 register Hash_Entry *e; 353 Hash_Table *t = searchPtr->tablePtr; 354 355 /* 356 * The hashEntryPtr field points to the most recently returned 357 * entry, or is nil if we are starting up. If not nil, we have 358 * to start at the next one in the chain. 359 */ 360 e = searchPtr->hashEntryPtr; 361 if (e != NULL) 362 e = e->next; 363 /* 364 * If the chain ran out, or if we are starting up, we need to 365 * find the next nonempty chain. 366 */ 367 while (e == NULL) { 368 if (searchPtr->nextIndex >= t->size) 369 return (NULL); 370 e = t->bucketPtr[searchPtr->nextIndex++]; 371 } 372 searchPtr->hashEntryPtr = e; 373 return (e); 374 } 375 376 /* 377 *--------------------------------------------------------- 378 * 379 * RebuildTable -- 380 * This local routine makes a new hash table that 381 * is larger than the old one. 382 * 383 * Results: 384 * None. 385 * 386 * Side Effects: 387 * The entire hash table is moved, so any bucket numbers 388 * from the old table are invalid. 389 * 390 *--------------------------------------------------------- 391 */ 392 393 static void 394 RebuildTable(t) 395 register Hash_Table *t; 396 { 397 register Hash_Entry *e, *next = NULL, **hp, **xp; 398 register int i, mask; 399 register Hash_Entry **oldhp; 400 int oldsize; 401 402 oldhp = t->bucketPtr; 403 oldsize = i = t->size; 404 i <<= 1; 405 t->size = i; 406 t->mask = mask = i - 1; 407 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 408 while (--i >= 0) 409 *hp++ = NULL; 410 for (hp = oldhp, i = oldsize; --i >= 0;) { 411 for (e = *hp++; e != NULL; e = next) { 412 next = e->next; 413 xp = &t->bucketPtr[e->namehash & mask]; 414 e->next = *xp; 415 *xp = e; 416 } 417 } 418 free((char *)oldhp); 419 } 420