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 #ifdef MAKE_BOOTSTRAP 44 static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $"; 45 #else 46 #include <sys/cdefs.h> 47 #ifndef lint 48 #if 0 49 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93"; 50 #else 51 __RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $"); 52 #endif 53 #endif /* not lint */ 54 #endif 55 56 #include <sys/types.h> 57 58 #include <stdlib.h> 59 #include <string.h> 60 #include <unistd.h> 61 62 /* hash.c -- 63 * 64 * This module contains routines to manipulate a hash table. 65 * See hash.h for a definition of the structure of the hash 66 * table. Hash tables grow automatically as the amount of 67 * information increases. 68 */ 69 #include "sprite.h" 70 #ifndef ORDER 71 #include "make.h" 72 #endif /* ORDER */ 73 #include "hash.h" 74 #include "ealloc.h" 75 76 /* 77 * Forward references to local procedures that are used before they're 78 * defined: 79 */ 80 81 static void RebuildTable(Hash_Table *); 82 83 /* 84 * The following defines the ratio of # entries to # buckets 85 * at which we rebuild the table to make it larger. 86 */ 87 88 #define rebuildLimit 8 89 90 /* 91 *--------------------------------------------------------- 92 * 93 * Hash_InitTable -- 94 * 95 * This routine just sets up the hash table. 96 * 97 * Results: 98 * None. 99 * 100 * Side Effects: 101 * Memory is allocated for the initial bucket area. 102 * 103 *--------------------------------------------------------- 104 */ 105 106 void 107 Hash_InitTable( 108 register Hash_Table *t, /* Structure to use to hold table. */ 109 int numBuckets) /* How many buckets to create for starters. 110 * This number is rounded up to a power of 111 * two. If <= 0, a reasonable default is 112 * chosen. The table will grow in size later 113 * as needed. */ 114 { 115 register int i; 116 register struct Hash_Entry **hp; 117 118 /* 119 * Round up the size to a power of two. 120 */ 121 if (numBuckets <= 0) 122 i = 16; 123 else { 124 for (i = 2; i < numBuckets; i <<= 1) 125 continue; 126 } 127 t->numEntries = 0; 128 t->size = i; 129 t->mask = i - 1; 130 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 131 while (--i >= 0) 132 *hp++ = NULL; 133 } 134 135 /* 136 *--------------------------------------------------------- 137 * 138 * Hash_DeleteTable -- 139 * 140 * This routine removes everything from a hash table 141 * and frees up the memory space it occupied (except for 142 * the space in the Hash_Table structure). 143 * 144 * Results: 145 * None. 146 * 147 * Side Effects: 148 * Lots of memory is freed up. 149 * 150 *--------------------------------------------------------- 151 */ 152 153 void 154 Hash_DeleteTable(Hash_Table *t) 155 { 156 register struct Hash_Entry **hp, *h, *nexth = NULL; 157 register int i; 158 159 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 160 for (h = *hp++; h != NULL; h = nexth) { 161 nexth = h->next; 162 free((char *)h); 163 } 164 } 165 free((char *)t->bucketPtr); 166 167 /* 168 * Set up the hash table to cause memory faults on any future access 169 * attempts until re-initialization. 170 */ 171 t->bucketPtr = NULL; 172 } 173 174 /* 175 *--------------------------------------------------------- 176 * 177 * Hash_FindEntry -- 178 * 179 * Searches a hash table for an entry corresponding to key. 180 * 181 * Results: 182 * The return value is a pointer to the entry for key, 183 * if key was present in the table. If key was not 184 * present, NULL is returned. 185 * 186 * Side Effects: 187 * None. 188 * 189 *--------------------------------------------------------- 190 */ 191 192 Hash_Entry * 193 Hash_FindEntry( 194 Hash_Table *t, /* Hash table to search. */ 195 char *key) /* A hash key. */ 196 { 197 register Hash_Entry *e; 198 register unsigned h; 199 register char *p; 200 201 for (h = 0, p = key; *p;) 202 h = (h << 5) - h + *p++; 203 p = key; 204 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 205 if (e->namehash == h && strcmp(e->name, p) == 0) 206 return (e); 207 return (NULL); 208 } 209 210 /* 211 *--------------------------------------------------------- 212 * 213 * Hash_CreateEntry -- 214 * 215 * Searches a hash table for an entry corresponding to 216 * key. If no entry is found, then one is created. 217 * 218 * Results: 219 * The return value is a pointer to the entry. If *newPtr 220 * isn't NULL, then *newPtr is filled in with TRUE if a 221 * new entry was created, and FALSE if an entry already existed 222 * with the given key. 223 * 224 * Side Effects: 225 * Memory may be allocated, and the hash buckets may be modified. 226 *--------------------------------------------------------- 227 */ 228 229 Hash_Entry * 230 Hash_CreateEntry( 231 register Hash_Table *t, /* Hash table to search. */ 232 char *key, /* A hash key. */ 233 Boolean *newPtr) /* Filled in with TRUE if new entry created, 234 * FALSE otherwise. */ 235 { 236 register Hash_Entry *e; 237 register unsigned h; 238 register char *p; 239 int keylen; 240 struct Hash_Entry **hp; 241 242 /* 243 * Hash the key. As a side effect, save the length (strlen) of the 244 * key in case we need to create the entry. 245 */ 246 for (h = 0, p = key; *p;) 247 h = (h << 5) - h + *p++; 248 keylen = p - key; 249 p = key; 250 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 251 if (e->namehash == h && strcmp(e->name, p) == 0) { 252 if (newPtr != NULL) 253 *newPtr = FALSE; 254 return (e); 255 } 256 } 257 258 /* 259 * The desired entry isn't there. Before allocating a new entry, 260 * expand the table if necessary (and this changes the resulting 261 * bucket chain). 262 */ 263 if (t->numEntries >= rebuildLimit * t->size) 264 RebuildTable(t); 265 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen); 266 hp = &t->bucketPtr[h & t->mask]; 267 e->next = *hp; 268 *hp = e; 269 e->clientData = NULL; 270 e->namehash = h; 271 (void) strcpy(e->name, p); 272 t->numEntries++; 273 274 if (newPtr != NULL) 275 *newPtr = TRUE; 276 return (e); 277 } 278 279 /* 280 *--------------------------------------------------------- 281 * 282 * Hash_DeleteEntry -- 283 * 284 * Delete the given hash table entry and free memory associated with 285 * it. 286 * 287 * Results: 288 * None. 289 * 290 * Side Effects: 291 * Hash chain that entry lives in is modified and memory is freed. 292 * 293 *--------------------------------------------------------- 294 */ 295 296 void 297 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e) 298 { 299 register Hash_Entry **hp, *p; 300 301 if (e == NULL) 302 return; 303 for (hp = &t->bucketPtr[e->namehash & t->mask]; 304 (p = *hp) != NULL; hp = &p->next) { 305 if (p == e) { 306 *hp = p->next; 307 free((char *)p); 308 t->numEntries--; 309 return; 310 } 311 } 312 (void)write(2, "bad call to Hash_DeleteEntry\n", 29); 313 abort(); 314 } 315 316 /* 317 *--------------------------------------------------------- 318 * 319 * Hash_EnumFirst -- 320 * This procedure sets things up for a complete search 321 * of all entries recorded in the hash table. 322 * 323 * Results: 324 * The return value is the address of the first entry in 325 * the hash table, or NULL if the table is empty. 326 * 327 * Side Effects: 328 * The information in searchPtr is initialized so that successive 329 * calls to Hash_Next will return successive HashEntry's 330 * from the table. 331 * 332 *--------------------------------------------------------- 333 */ 334 335 Hash_Entry * 336 Hash_EnumFirst( 337 Hash_Table *t, /* Table to be searched. */ 338 register Hash_Search *searchPtr)/* Area in which to keep state 339 * about search.*/ 340 { 341 searchPtr->tablePtr = t; 342 searchPtr->nextIndex = 0; 343 searchPtr->hashEntryPtr = NULL; 344 return Hash_EnumNext(searchPtr); 345 } 346 347 /* 348 *--------------------------------------------------------- 349 * 350 * Hash_EnumNext -- 351 * This procedure returns successive entries in the hash table. 352 * 353 * Results: 354 * The return value is a pointer to the next HashEntry 355 * in the table, or NULL when the end of the table is 356 * reached. 357 * 358 * Side Effects: 359 * The information in searchPtr is modified to advance to the 360 * next entry. 361 * 362 *--------------------------------------------------------- 363 */ 364 365 Hash_Entry * 366 Hash_EnumNext( 367 register Hash_Search *searchPtr) /* Area used to keep state about 368 search. */ 369 { 370 register Hash_Entry *e; 371 Hash_Table *t = searchPtr->tablePtr; 372 373 /* 374 * The hashEntryPtr field points to the most recently returned 375 * entry, or is nil if we are starting up. If not nil, we have 376 * to start at the next one in the chain. 377 */ 378 e = searchPtr->hashEntryPtr; 379 if (e != NULL) 380 e = e->next; 381 /* 382 * If the chain ran out, or if we are starting up, we need to 383 * find the next nonempty chain. 384 */ 385 while (e == NULL) { 386 if (searchPtr->nextIndex >= t->size) 387 return (NULL); 388 e = t->bucketPtr[searchPtr->nextIndex++]; 389 } 390 searchPtr->hashEntryPtr = e; 391 return (e); 392 } 393 394 /* 395 *--------------------------------------------------------- 396 * 397 * RebuildTable -- 398 * This local routine makes a new hash table that 399 * is larger than the old one. 400 * 401 * Results: 402 * None. 403 * 404 * Side Effects: 405 * The entire hash table is moved, so any bucket numbers 406 * from the old table are invalid. 407 * 408 *--------------------------------------------------------- 409 */ 410 411 static void 412 RebuildTable(register Hash_Table *t) 413 { 414 register Hash_Entry *e, *next = NULL, **hp, **xp; 415 register int i, mask; 416 register Hash_Entry **oldhp; 417 int oldsize; 418 419 oldhp = t->bucketPtr; 420 oldsize = i = t->size; 421 i <<= 1; 422 t->size = i; 423 t->mask = mask = i - 1; 424 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 425 while (--i >= 0) 426 *hp++ = NULL; 427 for (hp = oldhp, i = oldsize; --i >= 0;) { 428 for (e = *hp++; e != NULL; e = next) { 429 next = e->next; 430 xp = &t->bucketPtr[e->namehash & mask]; 431 e->next = *xp; 432 *xp = e; 433 } 434 } 435 free((char *)oldhp); 436 } 437