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.
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. All advertising materials mentioning features or use of this software
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
24 * without specific prior written permission.
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 $
41 #include <sys/types.h>
49 * This module contains routines to manipulate a hash table.
50 * See hash.h for a definition of the structure of the hash
51 * table. Hash tables grow automatically as the amount of
52 * information increases.
62 * Forward references to local procedures that are used before they're
66 static void RebuildTable(Hash_Table
*);
69 * The following defines the ratio of # entries to # buckets
70 * at which we rebuild the table to make it larger.
73 #define rebuildLimit 8
76 *---------------------------------------------------------
80 * This routine just sets up the hash table.
86 * Memory is allocated for the initial bucket area.
88 *---------------------------------------------------------
92 * Hash_Table *t; Structure to use to hold table.
93 * int numBuckets; How many buckets to create for starters.
94 * This number is rounded up to a power of
95 * two. If <= 0, a reasonable default is
96 * chosen. The table will grow in size later
100 Hash_InitTable(Hash_Table
*t
, int numBuckets
)
103 struct Hash_Entry
**hp
;
106 * Round up the size to a power of two.
111 for (i
= 2; i
< numBuckets
; i
<<= 1)
117 t
->bucketPtr
= hp
= (struct Hash_Entry
**)emalloc(sizeof(*hp
) * i
);
123 *---------------------------------------------------------
125 * Hash_DeleteTable --
127 * This routine removes everything from a hash table
128 * and frees up the memory space it occupied (except for
129 * the space in the Hash_Table structure).
135 * Lots of memory is freed up.
137 *---------------------------------------------------------
141 Hash_DeleteTable(Hash_Table
*t
)
143 struct Hash_Entry
**hp
, *h
, *nexth
= NULL
;
146 for (hp
= t
->bucketPtr
, i
= t
->size
; --i
>= 0;) {
147 for (h
= *hp
++; h
!= NULL
; h
= nexth
) {
152 free((char *)t
->bucketPtr
);
155 * Set up the hash table to cause memory faults on any future access
156 * attempts until re-initialization.
162 *---------------------------------------------------------
166 * Searches a hash table for an entry corresponding to key.
169 * The return value is a pointer to the entry for key,
170 * if key was present in the table. If key was not
171 * present, NULL is returned.
176 *---------------------------------------------------------
180 Hash_FindEntry(Hash_Table
*t
, char *key
)
186 for (h
= 0, p
= key
; *p
;)
187 h
= (h
<< 5) - h
+ *p
++;
189 for (e
= t
->bucketPtr
[h
& t
->mask
]; e
!= NULL
; e
= e
->next
)
190 if (e
->namehash
== h
&& strcmp(e
->name
, p
) == 0)
196 *---------------------------------------------------------
198 * Hash_CreateEntry --
200 * Searches a hash table for an entry corresponding to
201 * key. If no entry is found, then one is created.
204 * The return value is a pointer to the entry. If *newPtr
205 * isn't NULL, then *newPtr is filled in with TRUE if a
206 * new entry was created, and FALSE if an entry already existed
207 * with the given key.
210 * Memory may be allocated, and the hash buckets may be modified.
211 *---------------------------------------------------------
215 Hash_CreateEntry(Hash_Table
*t
, char *key
, Boolean
*newPtr
)
221 struct Hash_Entry
**hp
;
224 * Hash the key. As a side effect, save the length (strlen) of the
225 * key in case we need to create the entry.
227 for (h
= 0, p
= key
; *p
;)
228 h
= (h
<< 5) - h
+ *p
++;
231 for (e
= t
->bucketPtr
[h
& t
->mask
]; e
!= NULL
; e
= e
->next
) {
232 if (e
->namehash
== h
&& strcmp(e
->name
, p
) == 0) {
240 * The desired entry isn't there. Before allocating a new entry,
241 * expand the table if necessary (and this changes the resulting
244 if (t
->numEntries
>= rebuildLimit
* t
->size
)
246 e
= (Hash_Entry
*) emalloc(sizeof(*e
) + keylen
);
247 hp
= &t
->bucketPtr
[h
& t
->mask
];
250 e
->clientData
= NULL
;
261 *---------------------------------------------------------
263 * Hash_DeleteEntry --
265 * Delete the given hash table entry and free memory associated with
272 * Hash chain that entry lives in is modified and memory is freed.
274 *---------------------------------------------------------
278 Hash_DeleteEntry(Hash_Table
*t
, Hash_Entry
*e
)
284 for (hp
= &t
->bucketPtr
[e
->namehash
& t
->mask
];
285 (p
= *hp
) != NULL
; hp
= &p
->next
) {
293 write(2, "bad call to Hash_DeleteEntry\n", 29);
298 *---------------------------------------------------------
301 * This procedure sets things up for a complete search
302 * of all entries recorded in the hash table.
305 * The return value is the address of the first entry in
306 * the hash table, or NULL if the table is empty.
309 * The information in searchPtr is initialized so that successive
310 * calls to Hash_Next will return successive HashEntry's
313 *---------------------------------------------------------
317 Hash_EnumFirst(Hash_Table
*t
, Hash_Search
*searchPtr
)
319 searchPtr
->tablePtr
= t
;
320 searchPtr
->nextIndex
= 0;
321 searchPtr
->hashEntryPtr
= NULL
;
322 return Hash_EnumNext(searchPtr
);
326 *---------------------------------------------------------
329 * This procedure returns successive entries in the hash table.
332 * The return value is a pointer to the next HashEntry
333 * in the table, or NULL when the end of the table is
337 * The information in searchPtr is modified to advance to the
340 *---------------------------------------------------------
344 Hash_EnumNext(Hash_Search
*searchPtr
)
347 Hash_Table
*t
= searchPtr
->tablePtr
;
350 * The hashEntryPtr field points to the most recently returned
351 * entry, or is nil if we are starting up. If not nil, we have
352 * to start at the next one in the chain.
354 e
= searchPtr
->hashEntryPtr
;
358 * If the chain ran out, or if we are starting up, we need to
359 * find the next nonempty chain.
362 if (searchPtr
->nextIndex
>= t
->size
)
364 e
= t
->bucketPtr
[searchPtr
->nextIndex
++];
366 searchPtr
->hashEntryPtr
= e
;
371 *---------------------------------------------------------
374 * This local routine makes a new hash table that
375 * is larger than the old one.
381 * The entire hash table is moved, so any bucket numbers
382 * from the old table are invalid.
384 *---------------------------------------------------------
388 RebuildTable(Hash_Table
*t
)
390 Hash_Entry
*e
, *next
= NULL
, **hp
, **xp
;
395 oldhp
= t
->bucketPtr
;
396 oldsize
= i
= t
->size
;
399 t
->mask
= mask
= i
- 1;
400 t
->bucketPtr
= hp
= (struct Hash_Entry
**) emalloc(sizeof(*hp
) * i
);
403 for (hp
= oldhp
, i
= oldsize
; --i
>= 0;) {
404 for (e
= *hp
++; e
!= NULL
; e
= next
) {
406 xp
= &t
->bucketPtr
[e
->namehash
& mask
];