2 /* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */
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
10 * This code is derived from software contributed to Berkeley by
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
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.
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
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38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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_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
115 register struct Hash_Entry **hp;
118 * Round up the size to a power of two.
123 for (i = 2; i < numBuckets; i <<= 1)
129 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
135 *---------------------------------------------------------
137 * Hash_DeleteTable --
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).
147 * Lots of memory is freed up.
149 *---------------------------------------------------------
156 register struct Hash_Entry **hp, *h, *nexth = NULL;
159 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
160 for (h = *hp++; h != NULL; h = nexth) {
165 free((char *)t->bucketPtr);
168 * Set up the hash table to cause memory faults on any future access
169 * attempts until re-initialization.
175 *---------------------------------------------------------
179 * Searches a hash table for an entry corresponding to key.
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.
189 *---------------------------------------------------------
193 Hash_FindEntry(t, key)
194 Hash_Table *t; /* Hash table to search. */
195 char *key; /* A hash key. */
197 register Hash_Entry *e;
201 for (h = 0, p = key; *p;)
202 h = (h << 5) - h + *p++;
204 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
205 if (e->namehash == h && strcmp(e->name, p) == 0)
211 *---------------------------------------------------------
213 * Hash_CreateEntry --
215 * Searches a hash table for an entry corresponding to
216 * key. If no entry is found, then one is created.
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.
225 * Memory may be allocated, and the hash buckets may be modified.
226 *---------------------------------------------------------
230 Hash_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. */
236 register Hash_Entry *e;
240 struct Hash_Entry **hp;
243 * Hash the key. As a side effect, save the length (strlen) of the
244 * key in case we need to create the entry.
246 for (h = 0, p = key; *p;)
247 h = (h << 5) - h + *p++;
250 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
251 if (e->namehash == h && strcmp(e->name, p) == 0) {
259 * The desired entry isn't there. Before allocating a new entry,
260 * expand the table if necessary (and this changes the resulting
263 if (t->numEntries >= rebuildLimit * t->size)
265 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
266 hp = &t->bucketPtr[h & t->mask];
269 e->clientData = NULL;
271 (void) strcpy(e->name, p);
280 *---------------------------------------------------------
282 * Hash_DeleteEntry --
284 * Delete the given hash table entry and free memory associated with
291 * Hash chain that entry lives in is modified and memory is freed.
293 *---------------------------------------------------------
297 Hash_DeleteEntry(t, e)
301 register Hash_Entry **hp, *p;
305 for (hp = &t->bucketPtr[e->namehash & t->mask];
306 (p = *hp) != NULL; hp = &p->next) {
314 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
319 *---------------------------------------------------------
322 * This procedure sets things up for a complete search
323 * of all entries recorded in the hash table.
326 * The return value is the address of the first entry in
327 * the hash table, or NULL if the table is empty.
330 * The information in searchPtr is initialized so that successive
331 * calls to Hash_Next will return successive HashEntry's
334 *---------------------------------------------------------
338 Hash_EnumFirst(t, searchPtr)
339 Hash_Table *t; /* Table to be searched. */
340 register Hash_Search *searchPtr;/* Area in which to keep state
343 searchPtr->tablePtr = t;
344 searchPtr->nextIndex = 0;
345 searchPtr->hashEntryPtr = NULL;
346 return Hash_EnumNext(searchPtr);
350 *---------------------------------------------------------
353 * This procedure returns successive entries in the hash table.
356 * The return value is a pointer to the next HashEntry
357 * in the table, or NULL when the end of the table is
361 * The information in searchPtr is modified to advance to the
364 *---------------------------------------------------------
368 Hash_EnumNext(searchPtr)
369 register Hash_Search *searchPtr; /* Area used to keep state about
372 register Hash_Entry *e;
373 Hash_Table *t = searchPtr->tablePtr;
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.
380 e = searchPtr->hashEntryPtr;
384 * If the chain ran out, or if we are starting up, we need to
385 * find the next nonempty chain.
388 if (searchPtr->nextIndex >= t->size)
390 e = t->bucketPtr[searchPtr->nextIndex++];
392 searchPtr->hashEntryPtr = e;
397 *---------------------------------------------------------
400 * This local routine makes a new hash table that
401 * is larger than the old one.
407 * The entire hash table is moved, so any bucket numbers
408 * from the old table are invalid.
410 *---------------------------------------------------------
415 register Hash_Table *t;
417 register Hash_Entry *e, *next = NULL, **hp, **xp;
418 register int i, mask;
419 register Hash_Entry **oldhp;
422 oldhp = t->bucketPtr;
423 oldsize = i = t->size;
426 t->mask = mask = i - 1;
427 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
430 for (hp = oldhp, i = oldsize; --i >= 0;) {
431 for (e = *hp++; e != NULL; e = next) {
433 xp = &t->bucketPtr[e->namehash & mask];