1 /* $NetBSD: hash.c,v 1.20 2013/11/14 00:27:05 sjg Exp $ */
4 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
7 * This code is derived from software contributed to Berkeley by
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * Copyright (c) 1988, 1989 by Adam de Boor
37 * Copyright (c) 1989 by Berkeley Softworks
38 * All rights reserved.
40 * This code is derived from software contributed to Berkeley by
43 * Redistribution and use in source and binary forms, with or without
44 * modification, are permitted provided that the following conditions
46 * 1. Redistributions of source code must retain the above copyright
47 * notice, this list of conditions and the following disclaimer.
48 * 2. Redistributions in binary form must reproduce the above copyright
49 * notice, this list of conditions and the following disclaimer in the
50 * documentation and/or other materials provided with the distribution.
51 * 3. All advertising materials mentioning features or use of this software
52 * must display the following acknowledgement:
53 * This product includes software developed by the University of
54 * California, Berkeley and its contributors.
55 * 4. Neither the name of the University nor the names of its contributors
56 * may be used to endorse or promote products derived from this software
57 * without specific prior written permission.
59 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
73 static char rcsid[] = "$NetBSD: hash.c,v 1.20 2013/11/14 00:27:05 sjg Exp $";
75 #include <sys/cdefs.h>
78 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93";
80 __RCSID("$NetBSD: hash.c,v 1.20 2013/11/14 00:27:05 sjg Exp $");
87 * This module contains routines to manipulate a hash table.
88 * See hash.h for a definition of the structure of the hash
89 * table. Hash tables grow automatically as the amount of
90 * information increases.
97 * Forward references to local procedures that are used before they're
101 static void RebuildTable(Hash_Table *);
104 * The following defines the ratio of # entries to # buckets
105 * at which we rebuild the table to make it larger.
108 #define rebuildLimit 3
111 *---------------------------------------------------------
115 * This routine just sets up the hash table.
118 * t Structure to to hold table.
119 * numBuckets How many buckets to create for starters. This
120 * number is rounded up to a power of two. If
121 * <= 0, a reasonable default is chosen. The
122 * table will grow in size later as needed.
128 * Memory is allocated for the initial bucket area.
130 *---------------------------------------------------------
134 Hash_InitTable(Hash_Table *t, int numBuckets)
137 struct Hash_Entry **hp;
140 * Round up the size to a power of two.
145 for (i = 2; i < numBuckets; i <<= 1)
151 t->bucketPtr = hp = bmake_malloc(sizeof(*hp) * i);
157 *---------------------------------------------------------
159 * Hash_DeleteTable --
161 * This routine removes everything from a hash table
162 * and frees up the memory space it occupied (except for
163 * the space in the Hash_Table structure).
169 * Lots of memory is freed up.
171 *---------------------------------------------------------
175 Hash_DeleteTable(Hash_Table *t)
177 struct Hash_Entry **hp, *h, *nexth = NULL;
180 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
181 for (h = *hp++; h != NULL; h = nexth) {
189 * Set up the hash table to cause memory faults on any future access
190 * attempts until re-initialization.
196 *---------------------------------------------------------
200 * Searches a hash table for an entry corresponding to key.
203 * t Hash table to search.
207 * The return value is a pointer to the entry for key,
208 * if key was present in the table. If key was not
209 * present, NULL is returned.
214 *---------------------------------------------------------
218 Hash_FindEntry(Hash_Table *t, const char *key)
224 if (t == NULL || t->bucketPtr == NULL) {
227 for (h = 0, p = key; *p;)
228 h = (h << 5) - h + *p++;
230 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
231 if (e->namehash == h && strcmp(e->name, p) == 0)
237 *---------------------------------------------------------
239 * Hash_CreateEntry --
241 * Searches a hash table for an entry corresponding to
242 * key. If no entry is found, then one is created.
245 * t Hash table to search.
247 * newPtr Filled in with TRUE if new entry created,
251 * The return value is a pointer to the entry. If *newPtr
252 * isn't NULL, then *newPtr is filled in with TRUE if a
253 * new entry was created, and FALSE if an entry already existed
254 * with the given key.
257 * Memory may be allocated, and the hash buckets may be modified.
258 *---------------------------------------------------------
262 Hash_CreateEntry(Hash_Table *t, const char *key, Boolean *newPtr)
268 struct Hash_Entry **hp;
271 * Hash the key. As a side effect, save the length (strlen) of the
272 * key in case we need to create the entry.
274 for (h = 0, p = key; *p;)
275 h = (h << 5) - h + *p++;
278 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
279 if (e->namehash == h && strcmp(e->name, p) == 0) {
287 * The desired entry isn't there. Before allocating a new entry,
288 * expand the table if necessary (and this changes the resulting
291 if (t->numEntries >= rebuildLimit * t->size)
293 e = bmake_malloc(sizeof(*e) + keylen);
294 hp = &t->bucketPtr[h & t->mask];
297 Hash_SetValue(e, NULL);
299 (void)strcpy(e->name, p);
308 *---------------------------------------------------------
310 * Hash_DeleteEntry --
312 * Delete the given hash table entry and free memory associated with
319 * Hash chain that entry lives in is modified and memory is freed.
321 *---------------------------------------------------------
325 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
331 for (hp = &t->bucketPtr[e->namehash & t->mask];
332 (p = *hp) != NULL; hp = &p->next) {
340 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
345 *---------------------------------------------------------
348 * This procedure sets things up for a complete search
349 * of all entries recorded in the hash table.
352 * t Table to be searched.
353 * searchPtr Area in which to keep state about search.
356 * The return value is the address of the first entry in
357 * the hash table, or NULL if the table is empty.
360 * The information in searchPtr is initialized so that successive
361 * calls to Hash_Next will return successive HashEntry's
364 *---------------------------------------------------------
368 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr)
370 searchPtr->tablePtr = t;
371 searchPtr->nextIndex = 0;
372 searchPtr->hashEntryPtr = NULL;
373 return Hash_EnumNext(searchPtr);
377 *---------------------------------------------------------
380 * This procedure returns successive entries in the hash table.
383 * searchPtr Area used to keep state about search.
386 * The return value is a pointer to the next HashEntry
387 * in the table, or NULL when the end of the table is
391 * The information in searchPtr is modified to advance to the
394 *---------------------------------------------------------
398 Hash_EnumNext(Hash_Search *searchPtr)
401 Hash_Table *t = searchPtr->tablePtr;
404 * The hashEntryPtr field points to the most recently returned
405 * entry, or is nil if we are starting up. If not nil, we have
406 * to start at the next one in the chain.
408 e = searchPtr->hashEntryPtr;
412 * If the chain ran out, or if we are starting up, we need to
413 * find the next nonempty chain.
416 if (searchPtr->nextIndex >= t->size)
418 e = t->bucketPtr[searchPtr->nextIndex++];
420 searchPtr->hashEntryPtr = e;
425 *---------------------------------------------------------
428 * This local routine makes a new hash table that
429 * is larger than the old one.
435 * The entire hash table is moved, so any bucket numbers
436 * from the old table are invalid.
438 *---------------------------------------------------------
442 RebuildTable(Hash_Table *t)
444 Hash_Entry *e, *next = NULL, **hp, **xp;
449 oldhp = t->bucketPtr;
450 oldsize = i = t->size;
453 t->mask = mask = i - 1;
454 t->bucketPtr = hp = bmake_malloc(sizeof(*hp) * i);
457 for (hp = oldhp, i = oldsize; --i >= 0;) {
458 for (e = *hp++; e != NULL; e = next) {
460 xp = &t->bucketPtr[e->namehash & mask];