1 /*
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
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Adam de Boor.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
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.
25 *
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
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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
36 * SUCH DAMAGE.
37 *
38 * $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $
39 */
40
41 #include <sys/types.h>
42
43 #include <stdlib.h>
44 #include <string.h>
45 #include <unistd.h>
46 #include <libutil.h>
47
48 /* hash.c --
49 *
50 * This module contains routines to manipulate a hash table.
51 * See hash.h for a definition of the structure of the hash
52 * table. Hash tables grow automatically as the amount of
53 * information increases.
54 */
55 #include "sprite.h"
56 #ifndef ORDER
57 #include "make.h"
58 #endif /* ORDER */
59 #include "hash.h"
60
61 /*
62 * Forward references to local procedures that are used before they're
63 * defined:
64 */
65
66 static void RebuildTable(Hash_Table *);
67
68 /*
69 * The following defines the ratio of # entries to # buckets
70 * at which we rebuild the table to make it larger.
71 */
72
73 #define rebuildLimit 8
74
75 /*
76 *---------------------------------------------------------
77 *
78 * Hash_InitTable --
79 *
80 * This routine just sets up the hash table.
81 *
82 * Arguments:
83 * Hash_Table *t
84 * Structure to use to hold table.
85 * int numBuckets
86 * How many buckets to create for starters. This number is
87 * rounded up to a power of 2. If <= 0, a reasonable default
88 * is chosen. The table will grow in size later as needed.
89 *
90 * Results:
91 * None.
92 *
93 * Side Effects:
94 * Memory is allocated for the initial bucket area.
95 *
96 *---------------------------------------------------------
97 */
98
99 void
Hash_InitTable(Hash_Table * t,int numBuckets)100 Hash_InitTable(Hash_Table *t, int numBuckets)
101 {
102 int i;
103 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 struct Hash_Entry **hp, *h, *nexth = NULL;
144 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 * Arguments:
169 * Hash_Table *t
170 * Hash table to be searched.
171 * char *key
172 * A hash key.
173 *
174 * Results:
175 * The return value is a pointer to the entry for key,
176 * if key was present in the table. If key was not
177 * present, NULL is returned.
178 *
179 * Side Effects:
180 * None.
181 *
182 *---------------------------------------------------------
183 */
184
185 Hash_Entry *
Hash_FindEntry(Hash_Table * t,char * key)186 Hash_FindEntry(Hash_Table *t, char *key)
187 {
188 Hash_Entry *e;
189 unsigned h;
190 char *p;
191
192 for (h = 0, p = key; *p;)
193 h = (h << 5) - h + *p++;
194 p = key;
195 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
196 if (e->namehash == h && strcmp(e->name, p) == 0)
197 return (e);
198 return (NULL);
199 }
200
201 /*
202 *---------------------------------------------------------
203 *
204 * Hash_CreateEntry --
205 *
206 * Searches a hash table for an entry corresponding to
207 * key. If no entry is found, then one is created.
208 *
209 * Arguments:
210 * Hash_Table *t
211 * Hash table to be searched.
212 * char *key
213 * A hash key.
214 * Boolean *newPtr
215 * Filled in with TRUE if new entry created, FALSE otherwise.
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
228 Hash_Entry *
Hash_CreateEntry(Hash_Table * t,char * key,Boolean * newPtr)229 Hash_CreateEntry(Hash_Table *t, char *key, Boolean *newPtr)
230 {
231 Hash_Entry *e;
232 unsigned h;
233 char *p;
234 int keylen;
235 struct Hash_Entry **hp;
236
237 /*
238 * Hash the key. As a side effect, save the length (strlen) of the
239 * key in case we need to create the entry.
240 */
241 for (h = 0, p = key; *p;)
242 h = (h << 5) - h + *p++;
243 keylen = p - key;
244 p = key;
245 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
246 if (e->namehash == h && strcmp(e->name, p) == 0) {
247 if (newPtr != NULL)
248 *newPtr = FALSE;
249 return (e);
250 }
251 }
252
253 /*
254 * The desired entry isn't there. Before allocating a new entry,
255 * expand the table if necessary (and this changes the resulting
256 * bucket chain).
257 */
258 if (t->numEntries >= rebuildLimit * t->size)
259 RebuildTable(t);
260 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
261 hp = &t->bucketPtr[h & t->mask];
262 e->next = *hp;
263 *hp = e;
264 e->clientData = NULL;
265 e->namehash = h;
266 strcpy(e->name, p);
267 t->numEntries++;
268
269 if (newPtr != NULL)
270 *newPtr = TRUE;
271 return (e);
272 }
273
274 /*
275 *---------------------------------------------------------
276 *
277 * Hash_DeleteEntry --
278 *
279 * Delete the given hash table entry and free memory associated with it.
280 *
281 * Results:
282 * None.
283 *
284 * Side Effects:
285 * Hash chain that entry lives in is modified and memory is freed.
286 *
287 *---------------------------------------------------------
288 */
289
290 void
Hash_DeleteEntry(Hash_Table * t,Hash_Entry * e)291 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
292 {
293 Hash_Entry **hp, *p;
294
295 if (e == NULL)
296 return;
297 for (hp = &t->bucketPtr[e->namehash & t->mask];
298 (p = *hp) != NULL; hp = &p->next) {
299 if (p == e) {
300 *hp = p->next;
301 free((char *)p);
302 t->numEntries--;
303 return;
304 }
305 }
306 write(2, "bad call to Hash_DeleteEntry\n", 29);
307 abort();
308 }
309
310 /*
311 *---------------------------------------------------------
312 *
313 * Hash_EnumFirst --
314 * This procedure sets things up for a complete search
315 * of all entries recorded in the hash table.
316 *
317 * Arguments:
318 * Hash_Table *t
319 * Hash table to be searched.
320 * Hash_Search *searchPtr
321 * Area in which to keep state about search.
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,Hash_Search * searchPtr)336 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr)
337 {
338 searchPtr->tablePtr = t;
339 searchPtr->nextIndex = 0;
340 searchPtr->hashEntryPtr = NULL;
341 return Hash_EnumNext(searchPtr);
342 }
343
344 /*
345 *---------------------------------------------------------
346 *
347 * Hash_EnumNext --
348 * This procedure returns successive entries in the hash table.
349 *
350 * Arguments:
351 * Hash_Search *searchPtr
352 * Area in which to keep state about search.
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(Hash_Search * searchPtr)367 Hash_EnumNext(Hash_Search *searchPtr)
368 {
369 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
410 static void
RebuildTable(Hash_Table * t)411 RebuildTable(Hash_Table *t)
412 {
413 Hash_Entry *e, *next = NULL, **hp, **xp;
414 int i, mask;
415 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 }
436