1 /* 2 * Copyright (c) 1988, 1989, 1990, 1993 3 * The Regents of the University of California. All rights reserved. 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 * %sccs.include.redist.c% 11 */ 12 13 #ifndef lint 14 static char sccsid[] = "@(#)hash.c 8.2 (Berkeley) 04/28/95"; 15 #endif /* not lint */ 16 17 /* hash.c -- 18 * 19 * This module contains routines to manipulate a hash table. 20 * See hash.h for a definition of the structure of the hash 21 * table. Hash tables grow automatically as the amount of 22 * information increases. 23 */ 24 #include "sprite.h" 25 #include "make.h" 26 #include "hash.h" 27 28 /* 29 * Forward references to local procedures that are used before they're 30 * defined: 31 */ 32 33 static void RebuildTable __P((Hash_Table *)); 34 35 /* 36 * The following defines the ratio of # entries to # buckets 37 * at which we rebuild the table to make it larger. 38 */ 39 40 #define rebuildLimit 8 41 42 /* 43 *--------------------------------------------------------- 44 * 45 * Hash_InitTable -- 46 * 47 * This routine just sets up the hash table. 48 * 49 * Results: 50 * None. 51 * 52 * Side Effects: 53 * Memory is allocated for the initial bucket area. 54 * 55 *--------------------------------------------------------- 56 */ 57 58 void 59 Hash_InitTable(t, numBuckets) 60 register Hash_Table *t; /* Structure to use to hold table. */ 61 int numBuckets; /* How many buckets to create for starters. 62 * This number is rounded up to a power of 63 * two. If <= 0, a reasonable default is 64 * chosen. The table will grow in size later 65 * as needed. */ 66 { 67 register int i; 68 register struct Hash_Entry **hp; 69 70 /* 71 * Round up the size to a power of two. 72 */ 73 if (numBuckets <= 0) 74 i = 16; 75 else { 76 for (i = 2; i < numBuckets; i <<= 1) 77 continue; 78 } 79 t->numEntries = 0; 80 t->size = i; 81 t->mask = i - 1; 82 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 83 while (--i >= 0) 84 *hp++ = NULL; 85 } 86 87 /* 88 *--------------------------------------------------------- 89 * 90 * Hash_DeleteTable -- 91 * 92 * This routine removes everything from a hash table 93 * and frees up the memory space it occupied (except for 94 * the space in the Hash_Table structure). 95 * 96 * Results: 97 * None. 98 * 99 * Side Effects: 100 * Lots of memory is freed up. 101 * 102 *--------------------------------------------------------- 103 */ 104 105 void 106 Hash_DeleteTable(t) 107 Hash_Table *t; 108 { 109 register struct Hash_Entry **hp, *h, *nexth = NULL; 110 register int i; 111 112 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 113 for (h = *hp++; h != NULL; h = nexth) { 114 nexth = h->next; 115 free((char *)h); 116 } 117 } 118 free((char *)t->bucketPtr); 119 120 /* 121 * Set up the hash table to cause memory faults on any future access 122 * attempts until re-initialization. 123 */ 124 t->bucketPtr = NULL; 125 } 126 127 /* 128 *--------------------------------------------------------- 129 * 130 * Hash_FindEntry -- 131 * 132 * Searches a hash table for an entry corresponding to key. 133 * 134 * Results: 135 * The return value is a pointer to the entry for key, 136 * if key was present in the table. If key was not 137 * present, NULL is returned. 138 * 139 * Side Effects: 140 * None. 141 * 142 *--------------------------------------------------------- 143 */ 144 145 Hash_Entry * 146 Hash_FindEntry(t, key) 147 Hash_Table *t; /* Hash table to search. */ 148 char *key; /* A hash key. */ 149 { 150 register Hash_Entry *e; 151 register unsigned h; 152 register char *p; 153 154 for (h = 0, p = key; *p;) 155 h = (h << 5) - h + *p++; 156 p = key; 157 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 158 if (e->namehash == h && strcmp(e->name, p) == 0) 159 return (e); 160 return (NULL); 161 } 162 163 /* 164 *--------------------------------------------------------- 165 * 166 * Hash_CreateEntry -- 167 * 168 * Searches a hash table for an entry corresponding to 169 * key. If no entry is found, then one is created. 170 * 171 * Results: 172 * The return value is a pointer to the entry. If *newPtr 173 * isn't NULL, then *newPtr is filled in with TRUE if a 174 * new entry was created, and FALSE if an entry already existed 175 * with the given key. 176 * 177 * Side Effects: 178 * Memory may be allocated, and the hash buckets may be modified. 179 *--------------------------------------------------------- 180 */ 181 182 Hash_Entry * 183 Hash_CreateEntry(t, key, newPtr) 184 register Hash_Table *t; /* Hash table to search. */ 185 char *key; /* A hash key. */ 186 Boolean *newPtr; /* Filled in with TRUE if new entry created, 187 * FALSE otherwise. */ 188 { 189 register Hash_Entry *e; 190 register unsigned h; 191 register char *p; 192 int keylen; 193 struct Hash_Entry **hp; 194 195 /* 196 * Hash the key. As a side effect, save the length (strlen) of the 197 * key in case we need to create the entry. 198 */ 199 for (h = 0, p = key; *p;) 200 h = (h << 5) - h + *p++; 201 keylen = p - key; 202 p = key; 203 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 204 if (e->namehash == h && strcmp(e->name, p) == 0) { 205 if (newPtr != NULL) 206 *newPtr = FALSE; 207 return (e); 208 } 209 } 210 211 /* 212 * The desired entry isn't there. Before allocating a new entry, 213 * expand the table if necessary (and this changes the resulting 214 * bucket chain). 215 */ 216 if (t->numEntries >= rebuildLimit * t->size) 217 RebuildTable(t); 218 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 219 hp = &t->bucketPtr[h & t->mask]; 220 e->next = *hp; 221 *hp = e; 222 e->clientData = NULL; 223 e->namehash = h; 224 (void) strcpy(e->name, p); 225 t->numEntries++; 226 227 if (newPtr != NULL) 228 *newPtr = TRUE; 229 return (e); 230 } 231 232 /* 233 *--------------------------------------------------------- 234 * 235 * Hash_DeleteEntry -- 236 * 237 * Delete the given hash table entry and free memory associated with 238 * it. 239 * 240 * Results: 241 * None. 242 * 243 * Side Effects: 244 * Hash chain that entry lives in is modified and memory is freed. 245 * 246 *--------------------------------------------------------- 247 */ 248 249 void 250 Hash_DeleteEntry(t, e) 251 Hash_Table *t; 252 Hash_Entry *e; 253 { 254 register Hash_Entry **hp, *p; 255 256 if (e == NULL) 257 return; 258 for (hp = &t->bucketPtr[e->namehash & t->mask]; 259 (p = *hp) != NULL; hp = &p->next) { 260 if (p == e) { 261 *hp = p->next; 262 free((char *)p); 263 t->numEntries--; 264 return; 265 } 266 } 267 (void) write(2, "bad call to Hash_DeleteEntry\n", 29); 268 abort(); 269 } 270 271 /* 272 *--------------------------------------------------------- 273 * 274 * Hash_EnumFirst -- 275 * This procedure sets things up for a complete search 276 * of all entries recorded in the hash table. 277 * 278 * Results: 279 * The return value is the address of the first entry in 280 * the hash table, or NULL if the table is empty. 281 * 282 * Side Effects: 283 * The information in searchPtr is initialized so that successive 284 * calls to Hash_Next will return successive HashEntry's 285 * from the table. 286 * 287 *--------------------------------------------------------- 288 */ 289 290 Hash_Entry * 291 Hash_EnumFirst(t, searchPtr) 292 Hash_Table *t; /* Table to be searched. */ 293 register Hash_Search *searchPtr;/* Area in which to keep state 294 * about search.*/ 295 { 296 searchPtr->tablePtr = t; 297 searchPtr->nextIndex = 0; 298 searchPtr->hashEntryPtr = NULL; 299 return Hash_EnumNext(searchPtr); 300 } 301 302 /* 303 *--------------------------------------------------------- 304 * 305 * Hash_EnumNext -- 306 * This procedure returns successive entries in the hash table. 307 * 308 * Results: 309 * The return value is a pointer to the next HashEntry 310 * in the table, or NULL when the end of the table is 311 * reached. 312 * 313 * Side Effects: 314 * The information in searchPtr is modified to advance to the 315 * next entry. 316 * 317 *--------------------------------------------------------- 318 */ 319 320 Hash_Entry * 321 Hash_EnumNext(searchPtr) 322 register Hash_Search *searchPtr; /* Area used to keep state about 323 search. */ 324 { 325 register Hash_Entry *e; 326 Hash_Table *t = searchPtr->tablePtr; 327 328 /* 329 * The hashEntryPtr field points to the most recently returned 330 * entry, or is nil if we are starting up. If not nil, we have 331 * to start at the next one in the chain. 332 */ 333 e = searchPtr->hashEntryPtr; 334 if (e != NULL) 335 e = e->next; 336 /* 337 * If the chain ran out, or if we are starting up, we need to 338 * find the next nonempty chain. 339 */ 340 while (e == NULL) { 341 if (searchPtr->nextIndex >= t->size) 342 return (NULL); 343 e = t->bucketPtr[searchPtr->nextIndex++]; 344 } 345 searchPtr->hashEntryPtr = e; 346 return (e); 347 } 348 349 /* 350 *--------------------------------------------------------- 351 * 352 * RebuildTable -- 353 * This local routine makes a new hash table that 354 * is larger than the old one. 355 * 356 * Results: 357 * None. 358 * 359 * Side Effects: 360 * The entire hash table is moved, so any bucket numbers 361 * from the old table are invalid. 362 * 363 *--------------------------------------------------------- 364 */ 365 366 static void 367 RebuildTable(t) 368 register Hash_Table *t; 369 { 370 register Hash_Entry *e, *next = NULL, **hp, **xp; 371 register int i, mask; 372 register Hash_Entry **oldhp; 373 int oldsize; 374 375 oldhp = t->bucketPtr; 376 oldsize = i = t->size; 377 i <<= 1; 378 t->size = i; 379 t->mask = mask = i - 1; 380 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 381 while (--i >= 0) 382 *hp++ = NULL; 383 for (hp = oldhp, i = oldsize; --i >= 0;) { 384 for (e = *hp++; e != NULL; e = next) { 385 next = e->next; 386 xp = &t->bucketPtr[e->namehash & mask]; 387 e->next = *xp; 388 *xp = e; 389 } 390 } 391 free((char *)oldhp); 392 } 393