1 /* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */
2
3 /*-
4 * SPDX-License-Identifier: BSD-4-Clause
5 *
6 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
7 * Copyright (c) 1988, 1989 by Adam de Boor
8 * Copyright (c) 1989 by Berkeley Softworks
9 * All rights reserved.
10 *
11 * This code is derived from software contributed to Berkeley by
12 * Adam de Boor.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
22 * 3. All advertising materials mentioning features or use of this software
23 * must display the following acknowledgement:
24 * This product includes software developed by the University of
25 * California, Berkeley and its contributors.
26 * 4. Neither the name of the University nor the names of its contributors
27 * may be used to endorse or promote products derived from this software
28 * without specific prior written permission.
29 *
30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 * SUCH DAMAGE.
41 */
42
43 #ifdef MAKE_BOOTSTRAP
44 static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $";
45 #else
46 #include <sys/cdefs.h>
47 #ifndef lint
48 #if 0
49 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93";
50 #else
51 __RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $");
52 #endif
53 #endif /* not lint */
54 #endif
55
56 #include <sys/types.h>
57
58 #include <stdlib.h>
59 #include <string.h>
60 #include <unistd.h>
61
62 /* hash.c --
63 *
64 * This module contains routines to manipulate a hash table.
65 * See hash.h for a definition of the structure of the hash
66 * table. Hash tables grow automatically as the amount of
67 * information increases.
68 */
69 #include "sprite.h"
70 #ifndef ORDER
71 #include "make.h"
72 #endif /* ORDER */
73 #include "hash.h"
74 #include "ealloc.h"
75
76 /*
77 * Forward references to local procedures that are used before they're
78 * defined:
79 */
80
81 static void RebuildTable(Hash_Table *);
82
83 /*
84 * The following defines the ratio of # entries to # buckets
85 * at which we rebuild the table to make it larger.
86 */
87
88 #define rebuildLimit 8
89
90 /*
91 *---------------------------------------------------------
92 *
93 * Hash_InitTable --
94 *
95 * This routine just sets up the hash table.
96 *
97 * Results:
98 * None.
99 *
100 * Side Effects:
101 * Memory is allocated for the initial bucket area.
102 *
103 *---------------------------------------------------------
104 */
105
106 void
Hash_InitTable(register Hash_Table * t,int numBuckets)107 Hash_InitTable(
108 register Hash_Table *t, /* Structure to use to hold table. */
109 int numBuckets) /* How many buckets to create for starters.
110 * This number is rounded up to a power of
111 * two. If <= 0, a reasonable default is
112 * chosen. The table will grow in size later
113 * as needed. */
114 {
115 register int i;
116 register struct Hash_Entry **hp;
117
118 /*
119 * Round up the size to a power of two.
120 */
121 if (numBuckets <= 0)
122 i = 16;
123 else {
124 for (i = 2; i < numBuckets; i <<= 1)
125 continue;
126 }
127 t->numEntries = 0;
128 t->size = i;
129 t->mask = i - 1;
130 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
131 while (--i >= 0)
132 *hp++ = NULL;
133 }
134
135 /*
136 *---------------------------------------------------------
137 *
138 * Hash_DeleteTable --
139 *
140 * This routine removes everything from a hash table
141 * and frees up the memory space it occupied (except for
142 * the space in the Hash_Table structure).
143 *
144 * Results:
145 * None.
146 *
147 * Side Effects:
148 * Lots of memory is freed up.
149 *
150 *---------------------------------------------------------
151 */
152
153 void
Hash_DeleteTable(Hash_Table * t)154 Hash_DeleteTable(Hash_Table *t)
155 {
156 register struct Hash_Entry **hp, *h, *nexth = NULL;
157 register int i;
158
159 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
160 for (h = *hp++; h != NULL; h = nexth) {
161 nexth = h->next;
162 free((char *)h);
163 }
164 }
165 free((char *)t->bucketPtr);
166
167 /*
168 * Set up the hash table to cause memory faults on any future access
169 * attempts until re-initialization.
170 */
171 t->bucketPtr = NULL;
172 }
173
174 /*
175 *---------------------------------------------------------
176 *
177 * Hash_FindEntry --
178 *
179 * Searches a hash table for an entry corresponding to key.
180 *
181 * Results:
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.
185 *
186 * Side Effects:
187 * None.
188 *
189 *---------------------------------------------------------
190 */
191
192 Hash_Entry *
Hash_FindEntry(Hash_Table * t,char * key)193 Hash_FindEntry(
194 Hash_Table *t, /* Hash table to search. */
195 char *key) /* A hash key. */
196 {
197 register Hash_Entry *e;
198 register unsigned h;
199 register char *p;
200
201 for (h = 0, p = key; *p;)
202 h = (h << 5) - h + *p++;
203 p = key;
204 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
205 if (e->namehash == h && strcmp(e->name, p) == 0)
206 return (e);
207 return (NULL);
208 }
209
210 /*
211 *---------------------------------------------------------
212 *
213 * Hash_CreateEntry --
214 *
215 * Searches a hash table for an entry corresponding to
216 * key. If no entry is found, then one is created.
217 *
218 * Results:
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.
223 *
224 * Side Effects:
225 * Memory may be allocated, and the hash buckets may be modified.
226 *---------------------------------------------------------
227 */
228
229 Hash_Entry *
Hash_CreateEntry(register Hash_Table * t,char * key,Boolean * newPtr)230 Hash_CreateEntry(
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. */
235 {
236 register Hash_Entry *e;
237 register unsigned h;
238 register char *p;
239 int keylen;
240 struct Hash_Entry **hp;
241
242 /*
243 * Hash the key. As a side effect, save the length (strlen) of the
244 * key in case we need to create the entry.
245 */
246 for (h = 0, p = key; *p;)
247 h = (h << 5) - h + *p++;
248 keylen = p - key;
249 p = key;
250 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
251 if (e->namehash == h && strcmp(e->name, p) == 0) {
252 if (newPtr != NULL)
253 *newPtr = FALSE;
254 return (e);
255 }
256 }
257
258 /*
259 * The desired entry isn't there. Before allocating a new entry,
260 * expand the table if necessary (and this changes the resulting
261 * bucket chain).
262 */
263 if (t->numEntries >= rebuildLimit * t->size)
264 RebuildTable(t);
265 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
266 hp = &t->bucketPtr[h & t->mask];
267 e->next = *hp;
268 *hp = e;
269 e->clientData = NULL;
270 e->namehash = h;
271 (void) strcpy(e->name, p);
272 t->numEntries++;
273
274 if (newPtr != NULL)
275 *newPtr = TRUE;
276 return (e);
277 }
278
279 /*
280 *---------------------------------------------------------
281 *
282 * Hash_DeleteEntry --
283 *
284 * Delete the given hash table entry and free memory associated with
285 * it.
286 *
287 * Results:
288 * None.
289 *
290 * Side Effects:
291 * Hash chain that entry lives in is modified and memory is freed.
292 *
293 *---------------------------------------------------------
294 */
295
296 void
Hash_DeleteEntry(Hash_Table * t,Hash_Entry * e)297 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
298 {
299 register Hash_Entry **hp, *p;
300
301 if (e == NULL)
302 return;
303 for (hp = &t->bucketPtr[e->namehash & t->mask];
304 (p = *hp) != NULL; hp = &p->next) {
305 if (p == e) {
306 *hp = p->next;
307 free((char *)p);
308 t->numEntries--;
309 return;
310 }
311 }
312 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
313 abort();
314 }
315
316 /*
317 *---------------------------------------------------------
318 *
319 * Hash_EnumFirst --
320 * This procedure sets things up for a complete search
321 * of all entries recorded in the hash table.
322 *
323 * Results:
324 * The return value is the address of the first entry in
325 * the hash table, or NULL if the table is empty.
326 *
327 * Side Effects:
328 * The information in searchPtr is initialized so that successive
329 * calls to Hash_Next will return successive HashEntry's
330 * from the table.
331 *
332 *---------------------------------------------------------
333 */
334
335 Hash_Entry *
Hash_EnumFirst(Hash_Table * t,register Hash_Search * searchPtr)336 Hash_EnumFirst(
337 Hash_Table *t, /* Table to be searched. */
338 register Hash_Search *searchPtr)/* Area in which to keep state
339 * about search.*/
340 {
341 searchPtr->tablePtr = t;
342 searchPtr->nextIndex = 0;
343 searchPtr->hashEntryPtr = NULL;
344 return Hash_EnumNext(searchPtr);
345 }
346
347 /*
348 *---------------------------------------------------------
349 *
350 * Hash_EnumNext --
351 * This procedure returns successive entries in the hash table.
352 *
353 * Results:
354 * The return value is a pointer to the next HashEntry
355 * in the table, or NULL when the end of the table is
356 * reached.
357 *
358 * Side Effects:
359 * The information in searchPtr is modified to advance to the
360 * next entry.
361 *
362 *---------------------------------------------------------
363 */
364
365 Hash_Entry *
Hash_EnumNext(register Hash_Search * searchPtr)366 Hash_EnumNext(
367 register Hash_Search *searchPtr) /* Area used to keep state about
368 search. */
369 {
370 register Hash_Entry *e;
371 Hash_Table *t = searchPtr->tablePtr;
372
373 /*
374 * The hashEntryPtr field points to the most recently returned
375 * entry, or is nil if we are starting up. If not nil, we have
376 * to start at the next one in the chain.
377 */
378 e = searchPtr->hashEntryPtr;
379 if (e != NULL)
380 e = e->next;
381 /*
382 * If the chain ran out, or if we are starting up, we need to
383 * find the next nonempty chain.
384 */
385 while (e == NULL) {
386 if (searchPtr->nextIndex >= t->size)
387 return (NULL);
388 e = t->bucketPtr[searchPtr->nextIndex++];
389 }
390 searchPtr->hashEntryPtr = e;
391 return (e);
392 }
393
394 /*
395 *---------------------------------------------------------
396 *
397 * RebuildTable --
398 * This local routine makes a new hash table that
399 * is larger than the old one.
400 *
401 * Results:
402 * None.
403 *
404 * Side Effects:
405 * The entire hash table is moved, so any bucket numbers
406 * from the old table are invalid.
407 *
408 *---------------------------------------------------------
409 */
410
411 static void
RebuildTable(register Hash_Table * t)412 RebuildTable(register Hash_Table *t)
413 {
414 register Hash_Entry *e, *next = NULL, **hp, **xp;
415 register int i, mask;
416 register Hash_Entry **oldhp;
417 int oldsize;
418
419 oldhp = t->bucketPtr;
420 oldsize = i = t->size;
421 i <<= 1;
422 t->size = i;
423 t->mask = mask = i - 1;
424 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
425 while (--i >= 0)
426 *hp++ = NULL;
427 for (hp = oldhp, i = oldsize; --i >= 0;) {
428 for (e = *hp++; e != NULL; e = next) {
429 next = e->next;
430 xp = &t->bucketPtr[e->namehash & mask];
431 e->next = *xp;
432 *xp = e;
433 }
434 }
435 free((char *)oldhp);
436 }
437