1/*- 2 * Copyright (c) 1988, 1989, 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1988, 1989 by Adam de Boor 5 * Copyright (c) 1989 by Berkeley Softworks 6 * All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * Adam de Boor. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the University of 22 * California, Berkeley and its contributors. 23 * 4. Neither the name of the University nor the names of its contributors 24 * may be used to endorse or promote products derived from this software 25 * without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37 * SUCH DAMAGE. 38 * 39 * @(#)hash.c 8.1 (Berkeley) 6/6/93 40 */ 41 42#include <sys/cdefs.h> 43__FBSDID("$FreeBSD$"); 44 45/* hash.c -- 46 * 47 * This module contains routines to manipulate a hash table. 48 * See hash.h for a definition of the structure of the hash 49 * table. Hash tables grow automatically as the amount of 50 * information increases. 51 */ 52 53#include <stdlib.h> 54#include <string.h> 55#include <unistd.h> 56 57#include "hash.h" 58#include "util.h" 59 60/* 61 * Forward references to local procedures that are used before they're 62 * defined: 63 */ 64static void RebuildTable(Hash_Table *); 65 66/* 67 * The following defines the ratio of # entries to # buckets 68 * at which we rebuild the table to make it larger. 69 */ 70 71#define rebuildLimit 8 72 73/* 74 *--------------------------------------------------------- 75 * 76 * Hash_InitTable -- 77 * 78 * Set up the hash table t with a given number of buckets, or a 79 * reasonable default if the number requested is less than or 80 * equal to zero. Hash tables will grow in size as needed. 81 * 82 * 83 * Results: 84 * None. 85 * 86 * Side Effects: 87 * Memory is allocated for the initial bucket area. 88 * 89 *--------------------------------------------------------- 90 */ 91void 92Hash_InitTable(Hash_Table *t, int numBuckets) 93{ 94 int i; 95 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 = 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 */ 131void 132Hash_DeleteTable(Hash_Table *t) 133{ 134 struct Hash_Entry **hp, *h, *nexth = NULL; 135 int i; 136 137 for (hp = t->bucketPtr, i = t->size; --i >= 0;) { 138 for (h = *hp++; h != NULL; h = nexth) { 139 nexth = h->next; 140 free(h); 141 } 142 } 143 free(t->bucketPtr); 144 145 /* 146 * Set up the hash table to cause memory faults on any future access 147 * attempts until re-initialization. 148 */ 149 t->bucketPtr = NULL; 150} 151 152/* 153 *--------------------------------------------------------- 154 * 155 * Hash_FindEntry -- 156 * 157 * Searches a hash table for an entry corresponding to key. 158 * 159 * Results: 160 * The return value is a pointer to the entry for key, 161 * if key was present in the table. If key was not 162 * present, NULL is returned. 163 * 164 * Side Effects: 165 * None. 166 * 167 *--------------------------------------------------------- 168 */ 169Hash_Entry * 170Hash_FindEntry(const Hash_Table *t, const char *key) 171{ 172 Hash_Entry *e; 173 unsigned h; 174 const char *p; 175 176 for (h = 0, p = key; *p;) 177 h = (h << 5) - h + *p++; 178 p = key; 179 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) 180 if (e->namehash == h && strcmp(e->name, p) == 0) 181 return (e); 182 return (NULL); 183} 184 185/* 186 *--------------------------------------------------------- 187 * 188 * Hash_CreateEntry -- 189 * 190 * Searches a hash table for an entry corresponding to 191 * key. If no entry is found, then one is created. 192 * 193 * Results: 194 * The return value is a pointer to the entry. If *newPtr 195 * isn't NULL, then *newPtr is filled in with TRUE if a 196 * new entry was created, and FALSE if an entry already existed 197 * with the given key. 198 * 199 * Side Effects: 200 * Memory may be allocated, and the hash buckets may be modified. 201 *--------------------------------------------------------- 202 */ 203Hash_Entry * 204Hash_CreateEntry(Hash_Table *t, const char *key, Boolean *newPtr) 205{ 206 Hash_Entry *e; 207 unsigned int h; 208 const char *p; 209 int keylen; 210 struct Hash_Entry **hp; 211 212 /* 213 * Hash the key. As a side effect, save the length (strlen) of the 214 * key in case we need to create the entry. 215 */ 216 for (h = 0, p = key; *p;) 217 h = (h << 5) - h + *p++; 218 keylen = p - key; 219 p = key; 220 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) { 221 if (e->namehash == h && strcmp(e->name, p) == 0) { 222 if (newPtr != NULL) 223 *newPtr = FALSE; 224 return (e); 225 } 226 } 227 228 /* 229 * The desired entry isn't there. Before allocating a new entry, 230 * expand the table if necessary (and this changes the resulting 231 * bucket chain). 232 */ 233 if (t->numEntries >= rebuildLimit * t->size) 234 RebuildTable(t); 235 e = emalloc(sizeof(*e) + keylen); 236 hp = &t->bucketPtr[h & t->mask]; 237 e->next = *hp; 238 *hp = e; 239 e->clientData = NULL; 240 e->namehash = h; 241 strcpy(e->name, p); 242 t->numEntries++; 243 244 if (newPtr != NULL) 245 *newPtr = TRUE; 246 return (e); 247} 248 249/* 250 *--------------------------------------------------------- 251 * 252 * Hash_DeleteEntry -- 253 * 254 * Delete the given hash table entry and free memory associated with 255 * it. 256 * 257 * Results: 258 * None. 259 * 260 * Side Effects: 261 * Hash chain that entry lives in is modified and memory is freed. 262 * 263 *--------------------------------------------------------- 264 */ 265void 266Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e) 267{ 268 Hash_Entry **hp, *p; 269 270 if (e == NULL) 271 return; 272 for (hp = &t->bucketPtr[e->namehash & t->mask]; 273 (p = *hp) != NULL; hp = &p->next) { 274 if (p == e) { 275 *hp = p->next; 276 free(p); 277 t->numEntries--; 278 return; 279 } 280 } 281 write(STDERR_FILENO, "bad call to Hash_DeleteEntry\n", 29); 282 abort(); 283} 284 285/* 286 *--------------------------------------------------------- 287 * 288 * Hash_EnumFirst -- 289 * This procedure sets things up for a complete search 290 * of all entries recorded in the hash table. 291 * 292 * Results: 293 * The return value is the address of the first entry in 294 * the hash table, or NULL if the table is empty. 295 * 296 * Side Effects: 297 * The information in searchPtr is initialized so that successive 298 * calls to Hash_Next will return successive HashEntry's 299 * from the table. 300 * 301 *--------------------------------------------------------- 302 */ 303Hash_Entry * 304Hash_EnumFirst(const Hash_Table *t, Hash_Search *searchPtr) 305{ 306 307 searchPtr->tablePtr = t; 308 searchPtr->nextIndex = 0; 309 searchPtr->hashEntryPtr = NULL; 310 return (Hash_EnumNext(searchPtr)); 311} 312 313/* 314 *--------------------------------------------------------- 315 * 316 * Hash_EnumNext -- 317 * This procedure returns successive entries in the hash table. 318 * 319 * Results: 320 * The return value is a pointer to the next HashEntry 321 * in the table, or NULL when the end of the table is 322 * reached. 323 * 324 * Side Effects: 325 * The information in searchPtr is modified to advance to the 326 * next entry. 327 * 328 *--------------------------------------------------------- 329 */ 330Hash_Entry * 331Hash_EnumNext(Hash_Search *searchPtr) 332{ 333 Hash_Entry *e; 334 const Hash_Table *t = searchPtr->tablePtr; 335 336 /* 337 * The hashEntryPtr field points to the most recently returned 338 * entry, or is NULL if we are starting up. If not NULL, we have 339 * to start at the next one in the chain. 340 */ 341 e = searchPtr->hashEntryPtr; 342 if (e != NULL) 343 e = e->next; 344 /* 345 * If the chain ran out, or if we are starting up, we need to 346 * find the next nonempty chain. 347 */ 348 while (e == NULL) { 349 if (searchPtr->nextIndex >= t->size) 350 return (NULL); 351 e = t->bucketPtr[searchPtr->nextIndex++]; 352 } 353 searchPtr->hashEntryPtr = e; 354 return (e); 355} 356 357/* 358 *--------------------------------------------------------- 359 * 360 * RebuildTable -- 361 * This local routine makes a new hash table that 362 * is larger than the old one. 363 * 364 * Results: 365 * None. 366 * 367 * Side Effects: 368 * The entire hash table is moved, so any bucket numbers 369 * from the old table are invalid. 370 * 371 *--------------------------------------------------------- 372 */ 373static void 374RebuildTable(Hash_Table *t) 375{ 376 Hash_Entry *e, *next = NULL, **hp, **xp; 377 int i, mask; 378 Hash_Entry **oldhp; 379 int oldsize; 380 381 oldhp = t->bucketPtr; 382 oldsize = i = t->size; 383 i <<= 1; 384 t->size = i; 385 t->mask = mask = i - 1; 386 t->bucketPtr = hp = emalloc(sizeof(*hp) * i); 387 while (--i >= 0) 388 *hp++ = NULL; 389 for (hp = oldhp, i = oldsize; --i >= 0;) { 390 for (e = *hp++; e != NULL; e = next) { 391 next = e->next; 392 xp = &t->bucketPtr[e->namehash & mask]; 393 e->next = *xp; 394 *xp = e; 395 } 396 } 397 free(oldhp); 398} 399