1 /* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */ 2 3 /*- 4 * SPDX-License-Identifier: BSD-4-Clause 5 * 6 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. 7 * Copyright (c) 1988, 1989 by Adam de Boor 8 * Copyright (c) 1989 by Berkeley Softworks 9 * All rights reserved. 10 * 11 * This code is derived from software contributed to Berkeley by 12 * Adam de Boor. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 1. Redistributions of source code must retain the above copyright 18 * notice, this list of conditions and the following disclaimer. 19 * 2. Redistributions in binary form must reproduce the above copyright 20 * notice, this list of conditions and the following disclaimer in the 21 * documentation and/or other materials provided with the distribution. 22 * 3. All advertising materials mentioning features or use of this software 23 * must display the following acknowledgement: 24 * This product includes software developed by the University of 25 * California, Berkeley and its contributors. 26 * 4. Neither the name of the University nor the names of its contributors 27 * may be used to endorse or promote products derived from this software 28 * without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 */ 42 43 #include <sys/types.h> 44 45 #include <stdlib.h> 46 #include <string.h> 47 #include <unistd.h> 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 #ifndef ORDER 58 #include "make.h" 59 #endif /* ORDER */ 60 #include "hash.h" 61 #include "ealloc.h" 62 63 /* 64 * Forward references to local procedures that are used before they're 65 * defined: 66 */ 67 68 static void RebuildTable(Hash_Table *); 69 70 /* 71 * The following defines the ratio of # entries to # buckets 72 * at which we rebuild the table to make it larger. 73 */ 74 75 #define rebuildLimit 8 76 77 /* 78 *--------------------------------------------------------- 79 * 80 * Hash_InitTable -- 81 * 82 * This routine just sets up the hash table. 83 * 84 * Results: 85 * None. 86 * 87 * Side Effects: 88 * Memory is allocated for the initial bucket area. 89 * 90 *--------------------------------------------------------- 91 */ 92 93 void 94 Hash_InitTable( 95 register Hash_Table *t, /* Structure to use to hold table. */ 96 int numBuckets) /* How many buckets to create for starters. 97 * This number is rounded up to a power of 98 * two. If <= 0, a reasonable default is 99 * chosen. The table will grow in size later 100 * as needed. */ 101 { 102 register int i; 103 register struct Hash_Entry **hp; 104 105 /* 106 * Round up the size to a power of two. 107 */ 108 if (numBuckets <= 0) 109 i = 16; 110 else { 111 for (i = 2; i < numBuckets; i <<= 1) 112 continue; 113 } 114 t->numEntries = 0; 115 t->size = i; 116 t->mask = i - 1; 117 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 118 while (--i >= 0) 119 *hp++ = NULL; 120 } 121 122 /* 123 *--------------------------------------------------------- 124 * 125 * Hash_DeleteTable -- 126 * 127 * This routine removes everything from a hash table 128 * and frees up the memory space it occupied (except for 129 * the space in the Hash_Table structure). 130 * 131 * Results: 132 * None. 133 * 134 * Side Effects: 135 * Lots of memory is freed up. 136 * 137 *--------------------------------------------------------- 138 */ 139 140 void 141 Hash_DeleteTable(Hash_Table *t) 142 { 143 register struct Hash_Entry **hp, *h, *nexth = NULL; 144 register int i; 145 146 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 147 for (h = *hp++; h != NULL; h = nexth) { 148 nexth = h->next; 149 free((char *)h); 150 } 151 } 152 free((char *)t->bucketPtr); 153 154 /* 155 * Set up the hash table to cause memory faults on any future access 156 * attempts until re-initialization. 157 */ 158 t->bucketPtr = NULL; 159 } 160 161 /* 162 *--------------------------------------------------------- 163 * 164 * Hash_FindEntry -- 165 * 166 * Searches a hash table for an entry corresponding to key. 167 * 168 * Results: 169 * The return value is a pointer to the entry for key, 170 * if key was present in the table. If key was not 171 * present, NULL is returned. 172 * 173 * Side Effects: 174 * None. 175 * 176 *--------------------------------------------------------- 177 */ 178 179 Hash_Entry * 180 Hash_FindEntry( 181 Hash_Table *t, /* Hash table to search. */ 182 char *key) /* A hash key. */ 183 { 184 register Hash_Entry *e; 185 register unsigned h; 186 register char *p; 187 188 for (h = 0, p = key; *p;) 189 h = (h << 5) - h + *p++; 190 p = key; 191 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 192 if (e->namehash == h && strcmp(e->name, p) == 0) 193 return (e); 194 return (NULL); 195 } 196 197 /* 198 *--------------------------------------------------------- 199 * 200 * Hash_CreateEntry -- 201 * 202 * Searches a hash table for an entry corresponding to 203 * key. If no entry is found, then one is created. 204 * 205 * Results: 206 * The return value is a pointer to the entry. If *newPtr 207 * isn't NULL, then *newPtr is filled in with TRUE if a 208 * new entry was created, and FALSE if an entry already existed 209 * with the given key. 210 * 211 * Side Effects: 212 * Memory may be allocated, and the hash buckets may be modified. 213 *--------------------------------------------------------- 214 */ 215 216 Hash_Entry * 217 Hash_CreateEntry( 218 register Hash_Table *t, /* Hash table to search. */ 219 char *key, /* A hash key. */ 220 Boolean *newPtr) /* Filled in with TRUE if new entry created, 221 * FALSE otherwise. */ 222 { 223 register Hash_Entry *e; 224 register unsigned h; 225 register char *p; 226 int keylen; 227 struct Hash_Entry **hp; 228 229 /* 230 * Hash the key. As a side effect, save the length (strlen) of the 231 * key in case we need to create the entry. 232 */ 233 for (h = 0, p = key; *p;) 234 h = (h << 5) - h + *p++; 235 keylen = p - key; 236 p = key; 237 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 238 if (e->namehash == h && strcmp(e->name, p) == 0) { 239 if (newPtr != NULL) 240 *newPtr = FALSE; 241 return (e); 242 } 243 } 244 245 /* 246 * The desired entry isn't there. Before allocating a new entry, 247 * expand the table if necessary (and this changes the resulting 248 * bucket chain). 249 */ 250 if (t->numEntries >= rebuildLimit * t->size) 251 RebuildTable(t); 252 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 253 hp = &t->bucketPtr[h & t->mask]; 254 e->next = *hp; 255 *hp = e; 256 e->clientData = NULL; 257 e->namehash = h; 258 (void) strcpy(e->name, p); 259 t->numEntries++; 260 261 if (newPtr != NULL) 262 *newPtr = TRUE; 263 return (e); 264 } 265 266 /* 267 *--------------------------------------------------------- 268 * 269 * Hash_DeleteEntry -- 270 * 271 * Delete the given hash table entry and free memory associated with 272 * it. 273 * 274 * Results: 275 * None. 276 * 277 * Side Effects: 278 * Hash chain that entry lives in is modified and memory is freed. 279 * 280 *--------------------------------------------------------- 281 */ 282 283 void 284 Hash_DeleteEntry(Hash_Table *t, 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( 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( 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(register Hash_Table *t) 400 { 401 register Hash_Entry *e, *next = NULL, **hp, **xp; 402 register int i, mask; 403 register Hash_Entry **oldhp; 404 int oldsize; 405 406 oldhp = t->bucketPtr; 407 oldsize = i = t->size; 408 i <<= 1; 409 t->size = i; 410 t->mask = mask = i - 1; 411 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 412 while (--i >= 0) 413 *hp++ = NULL; 414 for (hp = oldhp, i = oldsize; --i >= 0;) { 415 for (e = *hp++; e != NULL; e = next) { 416 next = e->next; 417 xp = &t->bucketPtr[e->namehash & mask]; 418 e->next = *xp; 419 *xp = e; 420 } 421 } 422 free((char *)oldhp); 423 } 424