1/* $FreeBSD: head/sbin/rcorder/hash.c 201227 2009-12-29 22:53:27Z ed $ */
2/* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */
3
4/*
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
8 * All rights reserved.
9 *
10 * This code is derived from software contributed to Berkeley by
11 * Adam de Boor.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
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.
28 *
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
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39 * SUCH DAMAGE.
40 */
41
42#ifdef MAKE_BOOTSTRAP
43static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $";
44#else
45#include <sys/cdefs.h>
46#ifndef lint
47#if 0
48static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93";
49#else
50__RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $");
51#endif
52#endif /* not lint */
53#endif
54
55#include <sys/types.h>
56
57#include <stdlib.h>
58#include <string.h>
59#include <unistd.h>
60
61/* hash.c --
62 *
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.
67 */
68#include "sprite.h"
69#ifndef ORDER
70#include "make.h"
71#endif /* ORDER */
72#include "hash.h"
73#include "ealloc.h"
74
75/*
76 * Forward references to local procedures that are used before they're
77 * defined:
78 */
79
80static void RebuildTable(Hash_Table *);
81
82/*
83 * The following defines the ratio of # entries to # buckets
84 * at which we rebuild the table to make it larger.
85 */
86
87#define rebuildLimit 8
88
89/*
90 *---------------------------------------------------------
91 *
92 * Hash_InitTable --
93 *
94 * This routine just sets up the hash table.
95 *
96 * Results:
97 * None.
98 *
99 * Side Effects:
100 * Memory is allocated for the initial bucket area.
101 *
102 *---------------------------------------------------------
103 */
104
105void
106Hash_InitTable(
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
112 * as needed. */
113{
114 register int i;
115 register struct Hash_Entry **hp;
116
117 /*
118 * Round up the size to a power of two.
119 */
120 if (numBuckets <= 0)
121 i = 16;
122 else {
123 for (i = 2; i < numBuckets; i <<= 1)
124 continue;
125 }
126 t->numEntries = 0;
127 t->size = i;
128 t->mask = i - 1;
129 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
130 while (--i >= 0)
131 *hp++ = NULL;
132}
133
134/*
135 *---------------------------------------------------------
136 *
137 * Hash_DeleteTable --
138 *
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).
142 *
143 * Results:
144 * None.
145 *
146 * Side Effects:
147 * Lots of memory is freed up.
148 *
149 *---------------------------------------------------------
150 */
151
152void
153Hash_DeleteTable(Hash_Table *t)
154{
155 register struct Hash_Entry **hp, *h, *nexth = NULL;
156 register int i;
157
158 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
159 for (h = *hp++; h != NULL; h = nexth) {
160 nexth = h->next;
161 free((char *)h);
162 }
163 }
164 free((char *)t->bucketPtr);
165
166 /*
167 * Set up the hash table to cause memory faults on any future access
168 * attempts until re-initialization.
169 */
170 t->bucketPtr = NULL;
171}
172
173/*
174 *---------------------------------------------------------
175 *
176 * Hash_FindEntry --
177 *
178 * Searches a hash table for an entry corresponding to key.
179 *
180 * Results:
181 * The return value is a pointer to the entry for key,
182 * if key was present in the table. If key was not
183 * present, NULL is returned.
184 *
185 * Side Effects:
186 * None.
187 *
188 *---------------------------------------------------------
189 */
190
191Hash_Entry *
192Hash_FindEntry(
193 Hash_Table *t, /* Hash table to search. */
194 char *key) /* A hash key. */
195{
196 register Hash_Entry *e;
197 register unsigned h;
198 register char *p;
199
200 for (h = 0, p = key; *p;)
201 h = (h << 5) - h + *p++;
202 p = key;
203 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
204 if (e->namehash == h && strcmp(e->name, p) == 0)
205 return (e);
206 return (NULL);
207}
208
209/*
210 *---------------------------------------------------------
211 *
212 * Hash_CreateEntry --
213 *
214 * Searches a hash table for an entry corresponding to
215 * key. If no entry is found, then one is created.
216 *
217 * Results:
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.
222 *
223 * Side Effects:
224 * Memory may be allocated, and the hash buckets may be modified.
225 *---------------------------------------------------------
226 */
227
228Hash_Entry *
229Hash_CreateEntry(
230 register Hash_Table *t, /* Hash table to search. */
231 char *key, /* A hash key. */
232 Boolean *newPtr) /* Filled in with TRUE if new entry created,
233 * FALSE otherwise. */
234{
235 register Hash_Entry *e;
236 register unsigned h;
237 register char *p;
238 int keylen;
239 struct Hash_Entry **hp;
240
241 /*
242 * Hash the key. As a side effect, save the length (strlen) of the
243 * key in case we need to create the entry.
244 */
245 for (h = 0, p = key; *p;)
246 h = (h << 5) - h + *p++;
247 keylen = p - key;
248 p = key;
249 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
250 if (e->namehash == h && strcmp(e->name, p) == 0) {
251 if (newPtr != NULL)
252 *newPtr = FALSE;
253 return (e);
254 }
255 }
256
257 /*
258 * The desired entry isn't there. Before allocating a new entry,
259 * expand the table if necessary (and this changes the resulting
260 * bucket chain).
261 */
262 if (t->numEntries >= rebuildLimit * t->size)
263 RebuildTable(t);
264 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
265 hp = &t->bucketPtr[h & t->mask];
266 e->next = *hp;
267 *hp = e;
268 e->clientData = NULL;
269 e->namehash = h;
270 (void) strcpy(e->name, p);
271 t->numEntries++;
272
273 if (newPtr != NULL)
274 *newPtr = TRUE;
275 return (e);
276}
277
278/*
279 *---------------------------------------------------------
280 *
281 * Hash_DeleteEntry --
282 *
283 * Delete the given hash table entry and free memory associated with
284 * it.
285 *
286 * Results:
287 * None.
288 *
289 * Side Effects:
290 * Hash chain that entry lives in is modified and memory is freed.
291 *
292 *---------------------------------------------------------
293 */
294
295void
296Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
297{
298 register Hash_Entry **hp, *p;
299
300 if (e == NULL)
301 return;
302 for (hp = &t->bucketPtr[e->namehash & t->mask];
303 (p = *hp) != NULL; hp = &p->next) {
304 if (p == e) {
305 *hp = p->next;
306 free((char *)p);
307 t->numEntries--;
308 return;
309 }
310 }
311 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
312 abort();
313}
314
315/*
316 *---------------------------------------------------------
317 *
318 * Hash_EnumFirst --
319 * This procedure sets things up for a complete search
320 * of all entries recorded in the hash table.
321 *
322 * Results:
323 * The return value is the address of the first entry in
324 * the hash table, or NULL if the table is empty.
325 *
326 * Side Effects:
327 * The information in searchPtr is initialized so that successive
328 * calls to Hash_Next will return successive HashEntry's
329 * from the table.
330 *
331 *---------------------------------------------------------
332 */
333
334Hash_Entry *
335Hash_EnumFirst(
336 Hash_Table *t, /* Table to be searched. */
337 register Hash_Search *searchPtr)/* Area in which to keep state
338 * about search.*/
339{
340 searchPtr->tablePtr = t;
341 searchPtr->nextIndex = 0;
342 searchPtr->hashEntryPtr = NULL;
343 return Hash_EnumNext(searchPtr);
344}
345
346/*
347 *---------------------------------------------------------
348 *
349 * Hash_EnumNext --
350 * This procedure returns successive entries in the hash table.
351 *
352 * Results:
353 * The return value is a pointer to the next HashEntry
354 * in the table, or NULL when the end of the table is
355 * reached.
356 *
357 * Side Effects:
358 * The information in searchPtr is modified to advance to the
359 * next entry.
360 *
361 *---------------------------------------------------------
362 */
363
364Hash_Entry *
365Hash_EnumNext(
366 register Hash_Search *searchPtr) /* Area used to keep state about
367 search. */
368{
369 register Hash_Entry *e;
370 Hash_Table *t = searchPtr->tablePtr;
371
372 /*
373 * The hashEntryPtr field points to the most recently returned
374 * entry, or is nil if we are starting up. If not nil, we have
375 * to start at the next one in the chain.
376 */
377 e = searchPtr->hashEntryPtr;
378 if (e != NULL)
379 e = e->next;
380 /*
381 * If the chain ran out, or if we are starting up, we need to
382 * find the next nonempty chain.
383 */
384 while (e == NULL) {
385 if (searchPtr->nextIndex >= t->size)
386 return (NULL);
387 e = t->bucketPtr[searchPtr->nextIndex++];
388 }
389 searchPtr->hashEntryPtr = e;
390 return (e);
391}
392
393/*
394 *---------------------------------------------------------
395 *
396 * RebuildTable --
397 * This local routine makes a new hash table that
398 * is larger than the old one.
399 *
400 * Results:
401 * None.
402 *
403 * Side Effects:
404 * The entire hash table is moved, so any bucket numbers
405 * from the old table are invalid.
406 *
407 *---------------------------------------------------------
408 */
409
410static void
411RebuildTable(register Hash_Table *t)
412{
413 register Hash_Entry *e, *next = NULL, **hp, **xp;
414 register int i, mask;
415 register Hash_Entry **oldhp;
416 int oldsize;
417
418 oldhp = t->bucketPtr;
419 oldsize = i = t->size;
420 i <<= 1;
421 t->size = i;
422 t->mask = mask = i - 1;
423 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
424 while (--i >= 0)
425 *hp++ = NULL;
426 for (hp = oldhp, i = oldsize; --i >= 0;) {
427 for (e = *hp++; e != NULL; e = next) {
428 next = e->next;
429 xp = &t->bucketPtr[e->namehash & mask];
430 e->next = *xp;
431 *xp = e;
432 }
433 }
434 free((char *)oldhp);
435}