source: trunk/src/kmk/hash.c@ 118

Last change on this file since 118 was 51, checked in by bird, 23 years ago

kMk and porting to kLib.
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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
39#ifndef lint
40#if 0
41static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93";
42#else
43static const char rcsid[] =
44 "$FreeBSD: src/usr.bin/make/hash.c,v 1.9 1999/09/11 13:08:01 hoek Exp $";
45#endif
46#define KLIBFILEDEF rcsid
47#endif /* not lint */
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#include "make.h"
58#include "hash.h"
59
60/*
61 * Forward references to local procedures that are used before they're
62 * defined:
63 */
64
65static void RebuildTable __P((Hash_Table *));
66
67/*
68 * The following defines the ratio of # entries to # buckets
69 * at which we rebuild the table to make it larger.
70 */
71
72#define rebuildLimit 8
73
74/*
75 *---------------------------------------------------------
76 *
77 * Hash_InitTable --
78 *
79 * This routine just sets up the hash table.
80 *
81 * Results:
82 * None.
83 *
84 * Side Effects:
85 * Memory is allocated for the initial bucket area.
86 *
87 *---------------------------------------------------------
88 */
89
90void
91Hash_InitTable(t, numBuckets)
92 register Hash_Table *t; /* Structure to use to hold table. */
93 int numBuckets; /* How many buckets to create for starters.
94 * This number is rounded up to a power of
95 * two. If <= 0, a reasonable default is
96 * chosen. The table will grow in size later
97 * as needed. */
98{
99 register int i;
100 register struct Hash_Entry **hp;
101
102 /*
103 * Round up the size to a power of two.
104 */
105 if (numBuckets <= 0)
106 i = 16;
107 else {
108 for (i = 2; i < numBuckets; i <<= 1)
109 continue;
110 }
111 t->numEntries = 0;
112 t->size = i;
113 t->mask = i - 1;
114 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
115 while (--i >= 0)
116 *hp++ = NULL;
117}
118
119/*
120 *---------------------------------------------------------
121 *
122 * Hash_DeleteTable --
123 *
124 * This routine removes everything from a hash table
125 * and frees up the memory space it occupied (except for
126 * the space in the Hash_Table structure).
127 *
128 * Results:
129 * None.
130 *
131 * Side Effects:
132 * Lots of memory is freed up.
133 *
134 *---------------------------------------------------------
135 */
136
137void
138Hash_DeleteTable(t)
139 Hash_Table *t;
140{
141 register struct Hash_Entry **hp, *h, *nexth = NULL;
142 register int i;
143
144 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
145 for (h = *hp++; h != NULL; h = nexth) {
146 nexth = h->next;
147 efree((char *)h);
148 }
149 }
150 efree((char *)t->bucketPtr);
151
152 /*
153 * Set up the hash table to cause memory faults on any future access
154 * attempts until re-initialization.
155 */
156 t->bucketPtr = NULL;
157}
158
159/*
160 *---------------------------------------------------------
161 *
162 * Hash_FindEntry --
163 *
164 * Searches a hash table for an entry corresponding to key.
165 *
166 * Results:
167 * The return value is a pointer to the entry for key,
168 * if key was present in the table. If key was not
169 * present, NULL is returned.
170 *
171 * Side Effects:
172 * None.
173 *
174 *---------------------------------------------------------
175 */
176
177Hash_Entry *
178Hash_FindEntry(t, key)
179 Hash_Table *t; /* Hash table to search. */
180 char *key; /* A hash key. */
181{
182 register Hash_Entry *e;
183 register unsigned h;
184 register char *p;
185
186 for (h = 0, p = key; *p;)
187 h = (h << 5) - h + *p++;
188 p = key;
189 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
190 if (e->namehash == h && strcmp(e->name, p) == 0)
191 return (e);
192 return (NULL);
193}
194
195/*
196 *---------------------------------------------------------
197 *
198 * Hash_CreateEntry --
199 *
200 * Searches a hash table for an entry corresponding to
201 * key. If no entry is found, then one is created.
202 *
203 * Results:
204 * The return value is a pointer to the entry. If *newPtr
205 * isn't NULL, then *newPtr is filled in with TRUE if a
206 * new entry was created, and FALSE if an entry already existed
207 * with the given key.
208 *
209 * Side Effects:
210 * Memory may be allocated, and the hash buckets may be modified.
211 *---------------------------------------------------------
212 */
213
214Hash_Entry *
215Hash_CreateEntry(t, key, newPtr)
216 register Hash_Table *t; /* Hash table to search. */
217 char *key; /* A hash key. */
218 Boolean *newPtr; /* Filled in with TRUE if new entry created,
219 * FALSE otherwise. */
220{
221 register Hash_Entry *e;
222 register unsigned h;
223 register char *p;
224 int keylen;
225 struct Hash_Entry **hp;
226
227 /*
228 * Hash the key. As a side effect, save the length (strlen) of the
229 * key in case we need to create the entry.
230 */
231 for (h = 0, p = key; *p;)
232 h = (h << 5) - h + *p++;
233 keylen = p - key;
234 p = key;
235 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
236 if (e->namehash == h && strcmp(e->name, p) == 0) {
237 if (newPtr != NULL)
238 *newPtr = FALSE;
239 return (e);
240 }
241 }
242
243 /*
244 * The desired entry isn't there. Before allocating a new entry,
245 * expand the table if necessary (and this changes the resulting
246 * bucket chain).
247 */
248 if (t->numEntries >= rebuildLimit * t->size)
249 RebuildTable(t);
250 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
251 hp = &t->bucketPtr[h & t->mask];
252 e->next = *hp;
253 *hp = e;
254 e->clientData = NULL;
255 e->namehash = h;
256 (void) strcpy(e->name, p);
257 t->numEntries++;
258
259 if (newPtr != NULL)
260 *newPtr = TRUE;
261 return (e);
262}
263
264/*
265 *---------------------------------------------------------
266 *
267 * Hash_DeleteEntry --
268 *
269 * Delete the given hash table entry and efree memory associated with
270 * it.
271 *
272 * Results:
273 * None.
274 *
275 * Side Effects:
276 * Hash chain that entry lives in is modified and memory is freed.
277 *
278 *---------------------------------------------------------
279 */
280
281void
282Hash_DeleteEntry(t, e)
283 Hash_Table *t;
284 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 efree((char *)p);
295 t->numEntries--;
296 return;
297 }
298 }
299 (void) write(STDERR_FILENO, "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
322Hash_Entry *
323Hash_EnumFirst(t, searchPtr)
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
352Hash_Entry *
353Hash_EnumNext(searchPtr)
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
398static void
399RebuildTable(t)
400 register Hash_Table *t;
401{
402 register Hash_Entry *e, *next = NULL, **hp, **xp;
403 register int i, mask;
404 register Hash_Entry **oldhp;
405 int oldsize;
406
407 oldhp = t->bucketPtr;
408 oldsize = i = t->size;
409 i <<= 1;
410 t->size = i;
411 t->mask = mask = i - 1;
412 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
413 while (--i >= 0)
414 *hp++ = NULL;
415 for (hp = oldhp, i = oldsize; --i >= 0;) {
416 for (e = *hp++; e != NULL; e = next) {
417 next = e->next;
418 xp = &t->bucketPtr[e->namehash & mask];
419 e->next = *xp;
420 *xp = e;
421 }
422 }
423 efree((char *)oldhp);
424}
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