1 /* $FreeBSD$ */
2 /* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */
3
4 /*-
5 * SPDX-License-Identifier: BSD-4-Clause
6 *
7 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
8 * Copyright (c) 1988, 1989 by Adam de Boor
9 * Copyright (c) 1989 by Berkeley Softworks
10 * All rights reserved.
11 *
12 * This code is derived from software contributed to Berkeley by
13 * Adam de Boor.
14 *
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
17 * are met:
18 * 1. Redistributions of source code must retain the above copyright
19 * notice, this list of conditions and the following disclaimer.
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in the
22 * documentation and/or other materials provided with the distribution.
23 * 3. All advertising materials mentioning features or use of this software
24 * must display the following acknowledgement:
25 * This product includes software developed by the University of
26 * California, Berkeley and its contributors.
27 * 4. Neither the name of the University nor the names of its contributors
28 * may be used to endorse or promote products derived from this software
29 * without specific prior written permission.
30 *
31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
41 * SUCH DAMAGE.
42 */
43
44 #ifdef MAKE_BOOTSTRAP
45 static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $";
46 #else
47 #include <sys/cdefs.h>
48 #ifndef lint
49 #if 0
50 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93";
51 #else
52 __RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $");
53 #endif
54 #endif /* not lint */
55 #endif
56
57 #include <sys/types.h>
58
59 #include <stdlib.h>
60 #include <string.h>
61 #include <unistd.h>
62
63 /* hash.c --
64 *
65 * This module contains routines to manipulate a hash table.
66 * See hash.h for a definition of the structure of the hash
67 * table. Hash tables grow automatically as the amount of
68 * information increases.
69 */
70 #include "sprite.h"
71 #ifndef ORDER
72 #include "make.h"
73 #endif /* ORDER */
74 #include "hash.h"
75 #include "ealloc.h"
76
77 /*
78 * Forward references to local procedures that are used before they're
79 * defined:
80 */
81
82 static void RebuildTable(Hash_Table *);
83
84 /*
85 * The following defines the ratio of # entries to # buckets
86 * at which we rebuild the table to make it larger.
87 */
88
89 #define rebuildLimit 8
90
91 /*
92 *---------------------------------------------------------
93 *
94 * Hash_InitTable --
95 *
96 * This routine just sets up the hash table.
97 *
98 * Results:
99 * None.
100 *
101 * Side Effects:
102 * Memory is allocated for the initial bucket area.
103 *
104 *---------------------------------------------------------
105 */
106
107 void
Hash_InitTable(register Hash_Table * t,int numBuckets)108 Hash_InitTable(
109 register Hash_Table *t, /* Structure to use to hold table. */
110 int numBuckets) /* How many buckets to create for starters.
111 * This number is rounded up to a power of
112 * two. If <= 0, a reasonable default is
113 * chosen. The table will grow in size later
114 * as needed. */
115 {
116 register int i;
117 register struct Hash_Entry **hp;
118
119 /*
120 * Round up the size to a power of two.
121 */
122 if (numBuckets <= 0)
123 i = 16;
124 else {
125 for (i = 2; i < numBuckets; i <<= 1)
126 continue;
127 }
128 t->numEntries = 0;
129 t->size = i;
130 t->mask = i - 1;
131 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
132 while (--i >= 0)
133 *hp++ = NULL;
134 }
135
136 /*
137 *---------------------------------------------------------
138 *
139 * Hash_DeleteTable --
140 *
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).
144 *
145 * Results:
146 * None.
147 *
148 * Side Effects:
149 * Lots of memory is freed up.
150 *
151 *---------------------------------------------------------
152 */
153
154 void
Hash_DeleteTable(Hash_Table * t)155 Hash_DeleteTable(Hash_Table *t)
156 {
157 register struct Hash_Entry **hp, *h, *nexth = NULL;
158 register int i;
159
160 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
161 for (h = *hp++; h != NULL; h = nexth) {
162 nexth = h->next;
163 free((char *)h);
164 }
165 }
166 free((char *)t->bucketPtr);
167
168 /*
169 * Set up the hash table to cause memory faults on any future access
170 * attempts until re-initialization.
171 */
172 t->bucketPtr = NULL;
173 }
174
175 /*
176 *---------------------------------------------------------
177 *
178 * Hash_FindEntry --
179 *
180 * Searches a hash table for an entry corresponding to key.
181 *
182 * Results:
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.
186 *
187 * Side Effects:
188 * None.
189 *
190 *---------------------------------------------------------
191 */
192
193 Hash_Entry *
Hash_FindEntry(Hash_Table * t,char * key)194 Hash_FindEntry(
195 Hash_Table *t, /* Hash table to search. */
196 char *key) /* A hash key. */
197 {
198 register Hash_Entry *e;
199 register unsigned h;
200 register char *p;
201
202 for (h = 0, p = key; *p;)
203 h = (h << 5) - h + *p++;
204 p = key;
205 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
206 if (e->namehash == h && strcmp(e->name, p) == 0)
207 return (e);
208 return (NULL);
209 }
210
211 /*
212 *---------------------------------------------------------
213 *
214 * Hash_CreateEntry --
215 *
216 * Searches a hash table for an entry corresponding to
217 * key. If no entry is found, then one is created.
218 *
219 * Results:
220 * The return value is a pointer to the entry. If *newPtr
221 * isn't NULL, then *newPtr is filled in with TRUE if a
222 * new entry was created, and FALSE if an entry already existed
223 * with the given key.
224 *
225 * Side Effects:
226 * Memory may be allocated, and the hash buckets may be modified.
227 *---------------------------------------------------------
228 */
229
230 Hash_Entry *
Hash_CreateEntry(register Hash_Table * t,char * key,Boolean * newPtr)231 Hash_CreateEntry(
232 register Hash_Table *t, /* Hash table to search. */
233 char *key, /* A hash key. */
234 Boolean *newPtr) /* Filled in with TRUE if new entry created,
235 * FALSE otherwise. */
236 {
237 register Hash_Entry *e;
238 register unsigned h;
239 register char *p;
240 int keylen;
241 struct Hash_Entry **hp;
242
243 /*
244 * Hash the key. As a side effect, save the length (strlen) of the
245 * key in case we need to create the entry.
246 */
247 for (h = 0, p = key; *p;)
248 h = (h << 5) - h + *p++;
249 keylen = p - key;
250 p = key;
251 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
252 if (e->namehash == h && strcmp(e->name, p) == 0) {
253 if (newPtr != NULL)
254 *newPtr = FALSE;
255 return (e);
256 }
257 }
258
259 /*
260 * The desired entry isn't there. Before allocating a new entry,
261 * expand the table if necessary (and this changes the resulting
262 * bucket chain).
263 */
264 if (t->numEntries >= rebuildLimit * t->size)
265 RebuildTable(t);
266 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
267 hp = &t->bucketPtr[h & t->mask];
268 e->next = *hp;
269 *hp = e;
270 e->clientData = NULL;
271 e->namehash = h;
272 (void) strcpy(e->name, p);
273 t->numEntries++;
274
275 if (newPtr != NULL)
276 *newPtr = TRUE;
277 return (e);
278 }
279
280 /*
281 *---------------------------------------------------------
282 *
283 * Hash_DeleteEntry --
284 *
285 * Delete the given hash table entry and free memory associated with
286 * it.
287 *
288 * Results:
289 * None.
290 *
291 * Side Effects:
292 * Hash chain that entry lives in is modified and memory is freed.
293 *
294 *---------------------------------------------------------
295 */
296
297 void
Hash_DeleteEntry(Hash_Table * t,Hash_Entry * e)298 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
299 {
300 register Hash_Entry **hp, *p;
301
302 if (e == NULL)
303 return;
304 for (hp = &t->bucketPtr[e->namehash & t->mask];
305 (p = *hp) != NULL; hp = &p->next) {
306 if (p == e) {
307 *hp = p->next;
308 free((char *)p);
309 t->numEntries--;
310 return;
311 }
312 }
313 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
314 abort();
315 }
316
317 /*
318 *---------------------------------------------------------
319 *
320 * Hash_EnumFirst --
321 * This procedure sets things up for a complete search
322 * of all entries recorded in the hash table.
323 *
324 * Results:
325 * The return value is the address of the first entry in
326 * the hash table, or NULL if the table is empty.
327 *
328 * Side Effects:
329 * The information in searchPtr is initialized so that successive
330 * calls to Hash_Next will return successive HashEntry's
331 * from the table.
332 *
333 *---------------------------------------------------------
334 */
335
336 Hash_Entry *
Hash_EnumFirst(Hash_Table * t,register Hash_Search * searchPtr)337 Hash_EnumFirst(
338 Hash_Table *t, /* Table to be searched. */
339 register Hash_Search *searchPtr)/* Area in which to keep state
340 * about search.*/
341 {
342 searchPtr->tablePtr = t;
343 searchPtr->nextIndex = 0;
344 searchPtr->hashEntryPtr = NULL;
345 return Hash_EnumNext(searchPtr);
346 }
347
348 /*
349 *---------------------------------------------------------
350 *
351 * Hash_EnumNext --
352 * This procedure returns successive entries in the hash table.
353 *
354 * Results:
355 * The return value is a pointer to the next HashEntry
356 * in the table, or NULL when the end of the table is
357 * reached.
358 *
359 * Side Effects:
360 * The information in searchPtr is modified to advance to the
361 * next entry.
362 *
363 *---------------------------------------------------------
364 */
365
366 Hash_Entry *
Hash_EnumNext(register Hash_Search * searchPtr)367 Hash_EnumNext(
368 register Hash_Search *searchPtr) /* Area used to keep state about
369 search. */
370 {
371 register Hash_Entry *e;
372 Hash_Table *t = searchPtr->tablePtr;
373
374 /*
375 * The hashEntryPtr field points to the most recently returned
376 * entry, or is nil if we are starting up. If not nil, we have
377 * to start at the next one in the chain.
378 */
379 e = searchPtr->hashEntryPtr;
380 if (e != NULL)
381 e = e->next;
382 /*
383 * If the chain ran out, or if we are starting up, we need to
384 * find the next nonempty chain.
385 */
386 while (e == NULL) {
387 if (searchPtr->nextIndex >= t->size)
388 return (NULL);
389 e = t->bucketPtr[searchPtr->nextIndex++];
390 }
391 searchPtr->hashEntryPtr = e;
392 return (e);
393 }
394
395 /*
396 *---------------------------------------------------------
397 *
398 * RebuildTable --
399 * This local routine makes a new hash table that
400 * is larger than the old one.
401 *
402 * Results:
403 * None.
404 *
405 * Side Effects:
406 * The entire hash table is moved, so any bucket numbers
407 * from the old table are invalid.
408 *
409 *---------------------------------------------------------
410 */
411
412 static void
RebuildTable(register Hash_Table * t)413 RebuildTable(register Hash_Table *t)
414 {
415 register Hash_Entry *e, *next = NULL, **hp, **xp;
416 register int i, mask;
417 register Hash_Entry **oldhp;
418 int oldsize;
419
420 oldhp = t->bucketPtr;
421 oldsize = i = t->size;
422 i <<= 1;
423 t->size = i;
424 t->mask = mask = i - 1;
425 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
426 while (--i >= 0)
427 *hp++ = NULL;
428 for (hp = oldhp, i = oldsize; --i >= 0;) {
429 for (e = *hp++; e != NULL; e = next) {
430 next = e->next;
431 xp = &t->bucketPtr[e->namehash & mask];
432 e->next = *xp;
433 *xp = e;
434 }
435 }
436 free((char *)oldhp);
437 }
438