hash.c revision 173412
1/* $FreeBSD: head/sbin/rcorder/hash.c 173412 2007-11-07 10:53:41Z kevlo $ */ 2/* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */ 3 4/* 5 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. 6 * Copyright (c) 1988, 1989 by Adam de Boor 7 * Copyright (c) 1989 by Berkeley Softworks 8 * All rights reserved. 9 * 10 * This code is derived from software contributed to Berkeley by 11 * Adam de Boor. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 */ 41 42#ifdef MAKE_BOOTSTRAP 43static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $"; 44#else 45#include <sys/cdefs.h> 46#ifndef lint 47#if 0 48static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93"; 49#else 50__RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $"); 51#endif 52#endif /* not lint */ 53#endif 54 55#include <sys/types.h> 56 57#include <stdlib.h> 58#include <string.h> 59#include <unistd.h> 60 61/* hash.c -- 62 * 63 * This module contains routines to manipulate a hash table. 64 * See hash.h for a definition of the structure of the hash 65 * table. Hash tables grow automatically as the amount of 66 * information increases. 67 */ 68#include "sprite.h" 69#ifndef ORDER 70#include "make.h" 71#endif /* ORDER */ 72#include "hash.h" 73#include "ealloc.h" 74 75/* 76 * Forward references to local procedures that are used before they're 77 * defined: 78 */ 79 80static void RebuildTable(Hash_Table *); 81 82/* 83 * The following defines the ratio of # entries to # buckets 84 * at which we rebuild the table to make it larger. 85 */ 86 87#define rebuildLimit 8 88 89/* 90 *--------------------------------------------------------- 91 * 92 * Hash_InitTable -- 93 * 94 * This routine just sets up the hash table. 95 * 96 * Results: 97 * None. 98 * 99 * Side Effects: 100 * Memory is allocated for the initial bucket area. 101 * 102 *--------------------------------------------------------- 103 */ 104 105void 106Hash_InitTable(t, numBuckets) 107 register Hash_Table *t; /* Structure to use to hold table. */ 108 int numBuckets; /* How many buckets to create for starters. 109 * This number is rounded up to a power of 110 * two. If <= 0, a reasonable default is 111 * chosen. The table will grow in size later 112 * as needed. */ 113{ 114 register int i; 115 register struct Hash_Entry **hp; 116 117 /* 118 * Round up the size to a power of two. 119 */ 120 if (numBuckets <= 0) 121 i = 16; 122 else { 123 for (i = 2; i < numBuckets; i <<= 1) 124 continue; 125 } 126 t->numEntries = 0; 127 t->size = i; 128 t->mask = i - 1; 129 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i); 130 while (--i >= 0) 131 *hp++ = NULL; 132} 133 134/* 135 *--------------------------------------------------------- 136 * 137 * Hash_DeleteTable -- 138 * 139 * This routine removes everything from a hash table 140 * and frees up the memory space it occupied (except for 141 * the space in the Hash_Table structure). 142 * 143 * Results: 144 * None. 145 * 146 * Side Effects: 147 * Lots of memory is freed up. 148 * 149 *--------------------------------------------------------- 150 */ 151 152void 153Hash_DeleteTable(t) 154 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 192Hash_Entry * 193Hash_FindEntry(t, key) 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 229Hash_Entry * 230Hash_CreateEntry(t, key, newPtr) 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 296void 297Hash_DeleteEntry(t, e) 298 Hash_Table *t; 299 Hash_Entry *e; 300{ 301 register Hash_Entry **hp, *p; 302 303 if (e == NULL) 304 return; 305 for (hp = &t->bucketPtr[e->namehash & t->mask]; 306 (p = *hp) != NULL; hp = &p->next) { 307 if (p == e) { 308 *hp = p->next; 309 free((char *)p); 310 t->numEntries--; 311 return; 312 } 313 } 314 (void)write(2, "bad call to Hash_DeleteEntry\n", 29); 315 abort(); 316} 317 318/* 319 *--------------------------------------------------------- 320 * 321 * Hash_EnumFirst -- 322 * This procedure sets things up for a complete search 323 * of all entries recorded in the hash table. 324 * 325 * Results: 326 * The return value is the address of the first entry in 327 * the hash table, or NULL if the table is empty. 328 * 329 * Side Effects: 330 * The information in searchPtr is initialized so that successive 331 * calls to Hash_Next will return successive HashEntry's 332 * from the table. 333 * 334 *--------------------------------------------------------- 335 */ 336 337Hash_Entry * 338Hash_EnumFirst(t, searchPtr) 339 Hash_Table *t; /* Table to be searched. */ 340 register Hash_Search *searchPtr;/* Area in which to keep state 341 * about search.*/ 342{ 343 searchPtr->tablePtr = t; 344 searchPtr->nextIndex = 0; 345 searchPtr->hashEntryPtr = NULL; 346 return Hash_EnumNext(searchPtr); 347} 348 349/* 350 *--------------------------------------------------------- 351 * 352 * Hash_EnumNext -- 353 * This procedure returns successive entries in the hash table. 354 * 355 * Results: 356 * The return value is a pointer to the next HashEntry 357 * in the table, or NULL when the end of the table is 358 * reached. 359 * 360 * Side Effects: 361 * The information in searchPtr is modified to advance to the 362 * next entry. 363 * 364 *--------------------------------------------------------- 365 */ 366 367Hash_Entry * 368Hash_EnumNext(searchPtr) 369 register Hash_Search *searchPtr; /* Area used to keep state about 370 search. */ 371{ 372 register Hash_Entry *e; 373 Hash_Table *t = searchPtr->tablePtr; 374 375 /* 376 * The hashEntryPtr field points to the most recently returned 377 * entry, or is nil if we are starting up. If not nil, we have 378 * to start at the next one in the chain. 379 */ 380 e = searchPtr->hashEntryPtr; 381 if (e != NULL) 382 e = e->next; 383 /* 384 * If the chain ran out, or if we are starting up, we need to 385 * find the next nonempty chain. 386 */ 387 while (e == NULL) { 388 if (searchPtr->nextIndex >= t->size) 389 return (NULL); 390 e = t->bucketPtr[searchPtr->nextIndex++]; 391 } 392 searchPtr->hashEntryPtr = e; 393 return (e); 394} 395 396/* 397 *--------------------------------------------------------- 398 * 399 * RebuildTable -- 400 * This local routine makes a new hash table that 401 * is larger than the old one. 402 * 403 * Results: 404 * None. 405 * 406 * Side Effects: 407 * The entire hash table is moved, so any bucket numbers 408 * from the old table are invalid. 409 * 410 *--------------------------------------------------------- 411 */ 412 413static void 414RebuildTable(t) 415 register Hash_Table *t; 416{ 417 register Hash_Entry *e, *next = NULL, **hp, **xp; 418 register int i, mask; 419 register Hash_Entry **oldhp; 420 int oldsize; 421 422 oldhp = t->bucketPtr; 423 oldsize = i = t->size; 424 i <<= 1; 425 t->size = i; 426 t->mask = mask = i - 1; 427 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i); 428 while (--i >= 0) 429 *hp++ = NULL; 430 for (hp = oldhp, i = oldsize; --i >= 0;) { 431 for (e = *hp++; e != NULL; e = next) { 432 next = e->next; 433 xp = &t->bucketPtr[e->namehash & mask]; 434 e->next = *xp; 435 *xp = e; 436 } 437 } 438 free((char *)oldhp); 439} 440