2 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
3 * Copyright (c) 1988, 1989 by Adam de Boor
4 * Copyright (c) 1989 by Berkeley Softworks
7 * This code is derived from software contributed to Berkeley by
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11 * modification, are permitted provided that the following conditions
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14 * notice, this list of conditions and the following disclaimer.
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19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
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26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $
39 * $DragonFly: src/sbin/rcorder/hash.c,v 1.4 2004/12/01 19:44:53 liamfoy Exp $
43 static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $";
45 #include <sys/cdefs.h>
48 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93";
50 __RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $");
55 #include <sys/types.h>
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.
76 * Forward references to local procedures that are used before they're
80 static void RebuildTable(Hash_Table *);
83 * The following defines the ratio of # entries to # buckets
84 * at which we rebuild the table to make it larger.
87 #define rebuildLimit 8
90 *---------------------------------------------------------
94 * This routine just sets up the hash table.
100 * Memory is allocated for the initial bucket area.
102 *---------------------------------------------------------
106 * Hash_Table *t; Structure to use to hold table.
107 * int numBuckets; How many buckets to create for starters.
108 * This number is rounded up to a power of
109 * two. If <= 0, a reasonable default is
110 * chosen. The table will grow in size later
114 Hash_InitTable(Hash_Table *t, int numBuckets)
117 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 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 *---------------------------------------------------------
194 Hash_FindEntry(Hash_Table *t, char *key)
200 for (h = 0, p = key; *p;)
201 h = (h << 5) - h + *p++;
203 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
204 if (e->namehash == h && strcmp(e->name, p) == 0)
210 *---------------------------------------------------------
212 * Hash_CreateEntry --
214 * Searches a hash table for an entry corresponding to
215 * key. If no entry is found, then one is created.
218 * The return value is a pointer to the entry. If *newPtr
219 * isn't NULL, then *newPtr is filled in with TRUE if a
220 * new entry was created, and FALSE if an entry already existed
221 * with the given key.
224 * Memory may be allocated, and the hash buckets may be modified.
225 *---------------------------------------------------------
229 Hash_CreateEntry(Hash_Table *t, char *key, Boolean *newPtr)
235 struct Hash_Entry **hp;
238 * Hash the key. As a side effect, save the length (strlen) of the
239 * key in case we need to create the entry.
241 for (h = 0, p = key; *p;)
242 h = (h << 5) - h + *p++;
245 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
246 if (e->namehash == h && strcmp(e->name, p) == 0) {
254 * The desired entry isn't there. Before allocating a new entry,
255 * expand the table if necessary (and this changes the resulting
258 if (t->numEntries >= rebuildLimit * t->size)
260 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
261 hp = &t->bucketPtr[h & t->mask];
264 e->clientData = NULL;
266 (void) strcpy(e->name, p);
275 *---------------------------------------------------------
277 * Hash_DeleteEntry --
279 * Delete the given hash table entry and free memory associated with
286 * Hash chain that entry lives in is modified and memory is freed.
288 *---------------------------------------------------------
292 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
298 for (hp = &t->bucketPtr[e->namehash & t->mask];
299 (p = *hp) != NULL; hp = &p->next) {
307 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
312 *---------------------------------------------------------
315 * This procedure sets things up for a complete search
316 * of all entries recorded in the hash table.
319 * The return value is the address of the first entry in
320 * the hash table, or NULL if the table is empty.
323 * The information in searchPtr is initialized so that successive
324 * calls to Hash_Next will return successive HashEntry's
327 *---------------------------------------------------------
331 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr)
333 searchPtr->tablePtr = t;
334 searchPtr->nextIndex = 0;
335 searchPtr->hashEntryPtr = NULL;
336 return Hash_EnumNext(searchPtr);
340 *---------------------------------------------------------
343 * This procedure returns successive entries in the hash table.
346 * The return value is a pointer to the next HashEntry
347 * in the table, or NULL when the end of the table is
351 * The information in searchPtr is modified to advance to the
354 *---------------------------------------------------------
358 Hash_EnumNext(Hash_Search *searchPtr)
361 Hash_Table *t = searchPtr->tablePtr;
364 * The hashEntryPtr field points to the most recently returned
365 * entry, or is nil if we are starting up. If not nil, we have
366 * to start at the next one in the chain.
368 e = searchPtr->hashEntryPtr;
372 * If the chain ran out, or if we are starting up, we need to
373 * find the next nonempty chain.
376 if (searchPtr->nextIndex >= t->size)
378 e = t->bucketPtr[searchPtr->nextIndex++];
380 searchPtr->hashEntryPtr = e;
385 *---------------------------------------------------------
388 * This local routine makes a new hash table that
389 * is larger than the old one.
395 * The entire hash table is moved, so any bucket numbers
396 * from the old table are invalid.
398 *---------------------------------------------------------
402 RebuildTable(Hash_Table *t)
404 Hash_Entry *e, *next = NULL, **hp, **xp;
409 oldhp = t->bucketPtr;
410 oldsize = i = t->size;
413 t->mask = mask = i - 1;
414 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
417 for (hp = oldhp, i = oldsize; --i >= 0;) {
418 for (e = *hp++; e != NULL; e = next) {
420 xp = &t->bucketPtr[e->namehash & mask];