2 /* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */
5 * SPDX-License-Identifier: BSD-4-Clause
7 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
8 * Copyright (c) 1988, 1989 by Adam de Boor
9 * Copyright (c) 1989 by Berkeley Softworks
10 * All rights reserved.
12 * This code is derived from software contributed to Berkeley by
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
18 * 1. Redistributions of source code must retain the above copyright
19 * notice, this list of conditions and the following disclaimer.
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in the
22 * documentation and/or other materials provided with the distribution.
23 * 3. All advertising materials mentioning features or use of this software
24 * must display the following acknowledgement:
25 * This product includes software developed by the University of
26 * California, Berkeley and its contributors.
27 * 4. Neither the name of the University nor the names of its contributors
28 * may be used to endorse or promote products derived from this software
29 * without specific prior written permission.
31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
45 static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $";
47 #include <sys/cdefs.h>
50 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93";
52 __RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $");
57 #include <sys/types.h>
65 * This module contains routines to manipulate a hash table.
66 * See hash.h for a definition of the structure of the hash
67 * table. Hash tables grow automatically as the amount of
68 * information increases.
78 * Forward references to local procedures that are used before they're
82 static void RebuildTable(Hash_Table *);
85 * The following defines the ratio of # entries to # buckets
86 * at which we rebuild the table to make it larger.
89 #define rebuildLimit 8
92 *---------------------------------------------------------
96 * This routine just sets up the hash table.
102 * Memory is allocated for the initial bucket area.
104 *---------------------------------------------------------
109 register Hash_Table *t, /* Structure to use to hold table. */
110 int numBuckets) /* How many buckets to create for starters.
111 * This number is rounded up to a power of
112 * two. If <= 0, a reasonable default is
113 * chosen. The table will grow in size later
117 register struct Hash_Entry **hp;
120 * Round up the size to a power of two.
125 for (i = 2; i < numBuckets; i <<= 1)
131 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
137 *---------------------------------------------------------
139 * Hash_DeleteTable --
141 * This routine removes everything from a hash table
142 * and frees up the memory space it occupied (except for
143 * the space in the Hash_Table structure).
149 * Lots of memory is freed up.
151 *---------------------------------------------------------
155 Hash_DeleteTable(Hash_Table *t)
157 register struct Hash_Entry **hp, *h, *nexth = NULL;
160 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
161 for (h = *hp++; h != NULL; h = nexth) {
166 free((char *)t->bucketPtr);
169 * Set up the hash table to cause memory faults on any future access
170 * attempts until re-initialization.
176 *---------------------------------------------------------
180 * Searches a hash table for an entry corresponding to key.
183 * The return value is a pointer to the entry for key,
184 * if key was present in the table. If key was not
185 * present, NULL is returned.
190 *---------------------------------------------------------
195 Hash_Table *t, /* Hash table to search. */
196 char *key) /* A hash key. */
198 register Hash_Entry *e;
202 for (h = 0, p = key; *p;)
203 h = (h << 5) - h + *p++;
205 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
206 if (e->namehash == h && strcmp(e->name, p) == 0)
212 *---------------------------------------------------------
214 * Hash_CreateEntry --
216 * Searches a hash table for an entry corresponding to
217 * key. If no entry is found, then one is created.
220 * The return value is a pointer to the entry. If *newPtr
221 * isn't NULL, then *newPtr is filled in with TRUE if a
222 * new entry was created, and FALSE if an entry already existed
223 * with the given key.
226 * Memory may be allocated, and the hash buckets may be modified.
227 *---------------------------------------------------------
232 register Hash_Table *t, /* Hash table to search. */
233 char *key, /* A hash key. */
234 Boolean *newPtr) /* Filled in with TRUE if new entry created,
235 * FALSE otherwise. */
237 register Hash_Entry *e;
241 struct Hash_Entry **hp;
244 * Hash the key. As a side effect, save the length (strlen) of the
245 * key in case we need to create the entry.
247 for (h = 0, p = key; *p;)
248 h = (h << 5) - h + *p++;
251 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
252 if (e->namehash == h && strcmp(e->name, p) == 0) {
260 * The desired entry isn't there. Before allocating a new entry,
261 * expand the table if necessary (and this changes the resulting
264 if (t->numEntries >= rebuildLimit * t->size)
266 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
267 hp = &t->bucketPtr[h & t->mask];
270 e->clientData = NULL;
272 (void) strcpy(e->name, p);
281 *---------------------------------------------------------
283 * Hash_DeleteEntry --
285 * Delete the given hash table entry and free memory associated with
292 * Hash chain that entry lives in is modified and memory is freed.
294 *---------------------------------------------------------
298 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
300 register Hash_Entry **hp, *p;
304 for (hp = &t->bucketPtr[e->namehash & t->mask];
305 (p = *hp) != NULL; hp = &p->next) {
313 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
318 *---------------------------------------------------------
321 * This procedure sets things up for a complete search
322 * of all entries recorded in the hash table.
325 * The return value is the address of the first entry in
326 * the hash table, or NULL if the table is empty.
329 * The information in searchPtr is initialized so that successive
330 * calls to Hash_Next will return successive HashEntry's
333 *---------------------------------------------------------
338 Hash_Table *t, /* Table to be searched. */
339 register Hash_Search *searchPtr)/* Area in which to keep state
342 searchPtr->tablePtr = t;
343 searchPtr->nextIndex = 0;
344 searchPtr->hashEntryPtr = NULL;
345 return Hash_EnumNext(searchPtr);
349 *---------------------------------------------------------
352 * This procedure returns successive entries in the hash table.
355 * The return value is a pointer to the next HashEntry
356 * in the table, or NULL when the end of the table is
360 * The information in searchPtr is modified to advance to the
363 *---------------------------------------------------------
368 register Hash_Search *searchPtr) /* Area used to keep state about
371 register Hash_Entry *e;
372 Hash_Table *t = searchPtr->tablePtr;
375 * The hashEntryPtr field points to the most recently returned
376 * entry, or is nil if we are starting up. If not nil, we have
377 * to start at the next one in the chain.
379 e = searchPtr->hashEntryPtr;
383 * If the chain ran out, or if we are starting up, we need to
384 * find the next nonempty chain.
387 if (searchPtr->nextIndex >= t->size)
389 e = t->bucketPtr[searchPtr->nextIndex++];
391 searchPtr->hashEntryPtr = e;
396 *---------------------------------------------------------
399 * This local routine makes a new hash table that
400 * is larger than the old one.
406 * The entire hash table is moved, so any bucket numbers
407 * from the old table are invalid.
409 *---------------------------------------------------------
413 RebuildTable(register Hash_Table *t)
415 register Hash_Entry *e, *next = NULL, **hp, **xp;
416 register int i, mask;
417 register Hash_Entry **oldhp;
420 oldhp = t->bucketPtr;
421 oldsize = i = t->size;
424 t->mask = mask = i - 1;
425 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
428 for (hp = oldhp, i = oldsize; --i >= 0;) {
429 for (e = *hp++; e != NULL; e = next) {
431 xp = &t->bucketPtr[e->namehash & mask];