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 #include <sys/types.h>
44
45 #include <stdlib.h>
46 #include <string.h>
47 #include <unistd.h>
48
49 /* hash.c --
50 *
51 * This module contains routines to manipulate a hash table.
52 * See hash.h for a definition of the structure of the hash
53 * table. Hash tables grow automatically as the amount of
54 * information increases.
55 */
56 #include "sprite.h"
57 #ifndef ORDER
58 #include "make.h"
59 #endif /* ORDER */
60 #include "hash.h"
61 #include "ealloc.h"
62
63 /*
64 * Forward references to local procedures that are used before they're
65 * defined:
66 */
67
68 static void RebuildTable(Hash_Table *);
69
70 /*
71 * The following defines the ratio of # entries to # buckets
72 * at which we rebuild the table to make it larger.
73 */
74
75 #define rebuildLimit 8
76
77 /*
78 *---------------------------------------------------------
79 *
80 * Hash_InitTable --
81 *
82 * This routine just sets up the hash table.
83 *
84 * Results:
85 * None.
86 *
87 * Side Effects:
88 * Memory is allocated for the initial bucket area.
89 *
90 *---------------------------------------------------------
91 */
92
93 void
Hash_InitTable(register Hash_Table * t,int numBuckets)94 Hash_InitTable(
95 register Hash_Table *t, /* Structure to use to hold table. */
96 int numBuckets) /* How many buckets to create for starters.
97 * This number is rounded up to a power of
98 * two. If <= 0, a reasonable default is
99 * chosen. The table will grow in size later
100 * as needed. */
101 {
102 register int i;
103 register struct Hash_Entry **hp;
104
105 /*
106 * Round up the size to a power of two.
107 */
108 if (numBuckets <= 0)
109 i = 16;
110 else {
111 for (i = 2; i < numBuckets; i <<= 1)
112 continue;
113 }
114 t->numEntries = 0;
115 t->size = i;
116 t->mask = i - 1;
117 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
118 while (--i >= 0)
119 *hp++ = NULL;
120 }
121
122 /*
123 *---------------------------------------------------------
124 *
125 * Hash_DeleteTable --
126 *
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).
130 *
131 * Results:
132 * None.
133 *
134 * Side Effects:
135 * Lots of memory is freed up.
136 *
137 *---------------------------------------------------------
138 */
139
140 void
Hash_DeleteTable(Hash_Table * t)141 Hash_DeleteTable(Hash_Table *t)
142 {
143 register struct Hash_Entry **hp, *h, *nexth = NULL;
144 register int i;
145
146 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
147 for (h = *hp++; h != NULL; h = nexth) {
148 nexth = h->next;
149 free((char *)h);
150 }
151 }
152 free((char *)t->bucketPtr);
153
154 /*
155 * Set up the hash table to cause memory faults on any future access
156 * attempts until re-initialization.
157 */
158 t->bucketPtr = NULL;
159 }
160
161 /*
162 *---------------------------------------------------------
163 *
164 * Hash_FindEntry --
165 *
166 * Searches a hash table for an entry corresponding to key.
167 *
168 * Results:
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.
172 *
173 * Side Effects:
174 * None.
175 *
176 *---------------------------------------------------------
177 */
178
179 Hash_Entry *
Hash_FindEntry(Hash_Table * t,char * key)180 Hash_FindEntry(
181 Hash_Table *t, /* Hash table to search. */
182 char *key) /* A hash key. */
183 {
184 register Hash_Entry *e;
185 register unsigned h;
186 register char *p;
187
188 for (h = 0, p = key; *p;)
189 h = (h << 5) - h + *p++;
190 p = key;
191 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
192 if (e->namehash == h && strcmp(e->name, p) == 0)
193 return (e);
194 return (NULL);
195 }
196
197 /*
198 *---------------------------------------------------------
199 *
200 * Hash_CreateEntry --
201 *
202 * Searches a hash table for an entry corresponding to
203 * key. If no entry is found, then one is created.
204 *
205 * Results:
206 * The return value is a pointer to the entry. If *newPtr
207 * isn't NULL, then *newPtr is filled in with TRUE if a
208 * new entry was created, and FALSE if an entry already existed
209 * with the given key.
210 *
211 * Side Effects:
212 * Memory may be allocated, and the hash buckets may be modified.
213 *---------------------------------------------------------
214 */
215
216 Hash_Entry *
Hash_CreateEntry(register Hash_Table * t,char * key,Boolean * newPtr)217 Hash_CreateEntry(
218 register Hash_Table *t, /* Hash table to search. */
219 char *key, /* A hash key. */
220 Boolean *newPtr) /* Filled in with TRUE if new entry created,
221 * FALSE otherwise. */
222 {
223 register Hash_Entry *e;
224 register unsigned h;
225 register char *p;
226 int keylen;
227 struct Hash_Entry **hp;
228
229 /*
230 * Hash the key. As a side effect, save the length (strlen) of the
231 * key in case we need to create the entry.
232 */
233 for (h = 0, p = key; *p;)
234 h = (h << 5) - h + *p++;
235 keylen = p - key;
236 p = key;
237 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
238 if (e->namehash == h && strcmp(e->name, p) == 0) {
239 if (newPtr != NULL)
240 *newPtr = FALSE;
241 return (e);
242 }
243 }
244
245 /*
246 * The desired entry isn't there. Before allocating a new entry,
247 * expand the table if necessary (and this changes the resulting
248 * bucket chain).
249 */
250 if (t->numEntries >= rebuildLimit * t->size)
251 RebuildTable(t);
252 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
253 hp = &t->bucketPtr[h & t->mask];
254 e->next = *hp;
255 *hp = e;
256 e->clientData = NULL;
257 e->namehash = h;
258 (void) strcpy(e->name, p);
259 t->numEntries++;
260
261 if (newPtr != NULL)
262 *newPtr = TRUE;
263 return (e);
264 }
265
266 /*
267 *---------------------------------------------------------
268 *
269 * Hash_DeleteEntry --
270 *
271 * Delete the given hash table entry and free memory associated with
272 * it.
273 *
274 * Results:
275 * None.
276 *
277 * Side Effects:
278 * Hash chain that entry lives in is modified and memory is freed.
279 *
280 *---------------------------------------------------------
281 */
282
283 void
Hash_DeleteEntry(Hash_Table * t,Hash_Entry * e)284 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
285 {
286 register Hash_Entry **hp, *p;
287
288 if (e == NULL)
289 return;
290 for (hp = &t->bucketPtr[e->namehash & t->mask];
291 (p = *hp) != NULL; hp = &p->next) {
292 if (p == e) {
293 *hp = p->next;
294 free((char *)p);
295 t->numEntries--;
296 return;
297 }
298 }
299 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
300 abort();
301 }
302
303 /*
304 *---------------------------------------------------------
305 *
306 * Hash_EnumFirst --
307 * This procedure sets things up for a complete search
308 * of all entries recorded in the hash table.
309 *
310 * Results:
311 * The return value is the address of the first entry in
312 * the hash table, or NULL if the table is empty.
313 *
314 * Side Effects:
315 * The information in searchPtr is initialized so that successive
316 * calls to Hash_Next will return successive HashEntry's
317 * from the table.
318 *
319 *---------------------------------------------------------
320 */
321
322 Hash_Entry *
Hash_EnumFirst(Hash_Table * t,register Hash_Search * searchPtr)323 Hash_EnumFirst(
324 Hash_Table *t, /* Table to be searched. */
325 register Hash_Search *searchPtr)/* Area in which to keep state
326 * about search.*/
327 {
328 searchPtr->tablePtr = t;
329 searchPtr->nextIndex = 0;
330 searchPtr->hashEntryPtr = NULL;
331 return Hash_EnumNext(searchPtr);
332 }
333
334 /*
335 *---------------------------------------------------------
336 *
337 * Hash_EnumNext --
338 * This procedure returns successive entries in the hash table.
339 *
340 * Results:
341 * The return value is a pointer to the next HashEntry
342 * in the table, or NULL when the end of the table is
343 * reached.
344 *
345 * Side Effects:
346 * The information in searchPtr is modified to advance to the
347 * next entry.
348 *
349 *---------------------------------------------------------
350 */
351
352 Hash_Entry *
Hash_EnumNext(register Hash_Search * searchPtr)353 Hash_EnumNext(
354 register Hash_Search *searchPtr) /* Area used to keep state about
355 search. */
356 {
357 register Hash_Entry *e;
358 Hash_Table *t = searchPtr->tablePtr;
359
360 /*
361 * The hashEntryPtr field points to the most recently returned
362 * entry, or is nil if we are starting up. If not nil, we have
363 * to start at the next one in the chain.
364 */
365 e = searchPtr->hashEntryPtr;
366 if (e != NULL)
367 e = e->next;
368 /*
369 * If the chain ran out, or if we are starting up, we need to
370 * find the next nonempty chain.
371 */
372 while (e == NULL) {
373 if (searchPtr->nextIndex >= t->size)
374 return (NULL);
375 e = t->bucketPtr[searchPtr->nextIndex++];
376 }
377 searchPtr->hashEntryPtr = e;
378 return (e);
379 }
380
381 /*
382 *---------------------------------------------------------
383 *
384 * RebuildTable --
385 * This local routine makes a new hash table that
386 * is larger than the old one.
387 *
388 * Results:
389 * None.
390 *
391 * Side Effects:
392 * The entire hash table is moved, so any bucket numbers
393 * from the old table are invalid.
394 *
395 *---------------------------------------------------------
396 */
397
398 static void
RebuildTable(register Hash_Table * t)399 RebuildTable(register Hash_Table *t)
400 {
401 register Hash_Entry *e, *next = NULL, **hp, **xp;
402 register int i, mask;
403 register Hash_Entry **oldhp;
404 int oldsize;
405
406 oldhp = t->bucketPtr;
407 oldsize = i = t->size;
408 i <<= 1;
409 t->size = i;
410 t->mask = mask = i - 1;
411 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
412 while (--i >= 0)
413 *hp++ = NULL;
414 for (hp = oldhp, i = oldsize; --i >= 0;) {
415 for (e = *hp++; e != NULL; e = next) {
416 next = e->next;
417 xp = &t->bucketPtr[e->namehash & mask];
418 e->next = *xp;
419 *xp = e;
420 }
421 }
422 free((char *)oldhp);
423 }
424