1/*	$NetBSD: hash.c,v 1.74 2023/12/19 19:33:39 rillig Exp $	*/
2
3/*
4 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
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. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35/*
36 * Copyright (c) 1988, 1989 by Adam de Boor
37 * Copyright (c) 1989 by Berkeley Softworks
38 * All rights reserved.
39 *
40 * This code is derived from software contributed to Berkeley by
41 * Adam de Boor.
42 *
43 * Redistribution and use in source and binary forms, with or without
44 * modification, are permitted provided that the following conditions
45 * are met:
46 * 1. Redistributions of source code must retain the above copyright
47 *    notice, this list of conditions and the following disclaimer.
48 * 2. Redistributions in binary form must reproduce the above copyright
49 *    notice, this list of conditions and the following disclaimer in the
50 *    documentation and/or other materials provided with the distribution.
51 * 3. All advertising materials mentioning features or use of this software
52 *    must display the following acknowledgement:
53 *	This product includes software developed by the University of
54 *	California, Berkeley and its contributors.
55 * 4. Neither the name of the University nor the names of its contributors
56 *    may be used to endorse or promote products derived from this software
57 *    without specific prior written permission.
58 *
59 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
69 * SUCH DAMAGE.
70 */
71
72/* Hash tables with string keys and pointer values. */
73
74#include "make.h"
75
76/*	"@(#)hash.c	8.1 (Berkeley) 6/6/93"	*/
77MAKE_RCSID("$NetBSD: hash.c,v 1.74 2023/12/19 19:33:39 rillig Exp $");
78
79/*
80 * The ratio of # entries to # buckets at which we rebuild the table to
81 * make it larger.
82 */
83#define rebuildLimit 3
84
85/* This hash function matches Gosling's Emacs and java.lang.String. */
86static unsigned int
87Hash_String(const char *key, const char **out_keyEnd)
88{
89	unsigned int h;
90	const char *p;
91
92	h = 0;
93	for (p = key; *p != '\0'; p++)
94		h = 31 * h + (unsigned char)*p;
95
96	*out_keyEnd = p;
97	return h;
98}
99
100/* This hash function matches Gosling's Emacs and java.lang.String. */
101unsigned int
102Hash_Substring(Substring key)
103{
104	unsigned int h;
105	const char *p;
106
107	h = 0;
108	for (p = key.start; p != key.end; p++)
109		h = 31 * h + (unsigned char)*p;
110	return h;
111}
112
113static HashEntry *
114HashTable_Find(HashTable *t, Substring key, unsigned int h)
115{
116	HashEntry *he;
117	unsigned int chainlen = 0;
118	size_t keyLen = Substring_Length(key);
119
120#ifdef DEBUG_HASH_LOOKUP
121	DEBUG4(HASH, "HashTable_Find: %p h=%08x key=%.*s\n",
122	    t, h, (int)keyLen, key.start);
123#endif
124
125	for (he = t->buckets[h & t->bucketsMask]; he != NULL; he = he->next) {
126		chainlen++;
127		if (he->hash == h &&
128		    strncmp(he->key, key.start, keyLen) == 0 &&
129		    he->key[keyLen] == '\0')
130			break;
131	}
132
133	if (chainlen > t->maxchain)
134		t->maxchain = chainlen;
135
136	return he;
137}
138
139/* Set up the hash table. */
140void
141HashTable_Init(HashTable *t)
142{
143	unsigned int n = 16, i;
144	HashEntry **buckets = bmake_malloc(sizeof *buckets * n);
145	for (i = 0; i < n; i++)
146		buckets[i] = NULL;
147
148	t->buckets = buckets;
149	t->bucketsSize = n;
150	t->numEntries = 0;
151	t->bucketsMask = n - 1;
152	t->maxchain = 0;
153}
154
155/*
156 * Remove everything from the hash table and free up the memory for the keys
157 * of the hash table, but not for the values associated to these keys.
158 */
159void
160HashTable_Done(HashTable *t)
161{
162	HashEntry **buckets = t->buckets;
163	size_t i, n = t->bucketsSize;
164
165	for (i = 0; i < n; i++) {
166		HashEntry *he = buckets[i];
167		while (he != NULL) {
168			HashEntry *next = he->next;
169			free(he);
170			he = next;
171		}
172	}
173
174	free(t->buckets);
175#ifdef CLEANUP
176	t->buckets = NULL;
177#endif
178}
179
180/* Find the entry corresponding to the key, or return NULL. */
181HashEntry *
182HashTable_FindEntry(HashTable *t, const char *key)
183{
184	const char *keyEnd;
185	unsigned int h = Hash_String(key, &keyEnd);
186	return HashTable_Find(t, Substring_Init(key, keyEnd), h);
187}
188
189/* Find the value corresponding to the key, or return NULL. */
190void *
191HashTable_FindValue(HashTable *t, const char *key)
192{
193	HashEntry *he = HashTable_FindEntry(t, key);
194	return he != NULL ? he->value : NULL;
195}
196
197/*
198 * Find the value corresponding to the key and the precomputed hash,
199 * or return NULL.
200 */
201void *
202HashTable_FindValueBySubstringHash(HashTable *t, Substring key, unsigned int h)
203{
204	HashEntry *he = HashTable_Find(t, key, h);
205	return he != NULL ? he->value : NULL;
206}
207
208/*
209 * Make the hash table larger. Any bucket numbers from the old table become
210 * invalid; the hash values stay valid though.
211 */
212static void
213HashTable_Enlarge(HashTable *t)
214{
215	unsigned int oldSize = t->bucketsSize;
216	HashEntry **oldBuckets = t->buckets;
217	unsigned int newSize = 2 * oldSize;
218	unsigned int newMask = newSize - 1;
219	HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize);
220	size_t i;
221
222	for (i = 0; i < newSize; i++)
223		newBuckets[i] = NULL;
224
225	for (i = 0; i < oldSize; i++) {
226		HashEntry *he = oldBuckets[i];
227		while (he != NULL) {
228			HashEntry *next = he->next;
229			he->next = newBuckets[he->hash & newMask];
230			newBuckets[he->hash & newMask] = he;
231			he = next;
232		}
233	}
234
235	free(oldBuckets);
236
237	t->bucketsSize = newSize;
238	t->bucketsMask = newMask;
239	t->buckets = newBuckets;
240	DEBUG4(HASH, "HashTable_Enlarge: %p size=%d entries=%d maxchain=%d\n",
241	    (void *)t, t->bucketsSize, t->numEntries, t->maxchain);
242	t->maxchain = 0;
243}
244
245/*
246 * Find or create an entry corresponding to the key.
247 * Return in out_isNew whether a new entry has been created.
248 */
249HashEntry *
250HashTable_CreateEntry(HashTable *t, const char *key, bool *out_isNew)
251{
252	const char *keyEnd;
253	unsigned int h = Hash_String(key, &keyEnd);
254	HashEntry *he = HashTable_Find(t, Substring_Init(key, keyEnd), h);
255
256	if (he != NULL) {
257		if (out_isNew != NULL)
258			*out_isNew = false;
259		return he;
260	}
261
262	if (t->numEntries >= rebuildLimit * t->bucketsSize)
263		HashTable_Enlarge(t);
264
265	he = bmake_malloc(sizeof *he + (size_t)(keyEnd - key));
266	he->value = NULL;
267	he->hash = h;
268	memcpy(he->key, key, (size_t)(keyEnd - key) + 1);
269
270	he->next = t->buckets[h & t->bucketsMask];
271	t->buckets[h & t->bucketsMask] = he;
272	t->numEntries++;
273
274	if (out_isNew != NULL)
275		*out_isNew = true;
276	return he;
277}
278
279void
280HashTable_Set(HashTable *t, const char *key, void *value)
281{
282	HashEntry *he = HashTable_CreateEntry(t, key, NULL);
283	HashEntry_Set(he, value);
284}
285
286/* Delete the entry from the table, don't free the value of the entry. */
287void
288HashTable_DeleteEntry(HashTable *t, HashEntry *he)
289{
290	HashEntry **ref = &t->buckets[he->hash & t->bucketsMask];
291	HashEntry *p;
292
293	for (; (p = *ref) != NULL; ref = &p->next) {
294		if (p == he) {
295			*ref = p->next;
296			free(p);
297			t->numEntries--;
298			return;
299		}
300	}
301	abort();
302}
303
304/*
305 * Return the next entry in the hash table, or NULL if the end of the table
306 * is reached.
307 */
308HashEntry *
309HashIter_Next(HashIter *hi)
310{
311	HashTable *t = hi->table;
312	HashEntry *he = hi->entry;
313	HashEntry **buckets = t->buckets;
314	unsigned int bucketsSize = t->bucketsSize;
315
316	if (he != NULL)
317		he = he->next;	/* skip the most recently returned entry */
318
319	while (he == NULL) {	/* find the next nonempty chain */
320		if (hi->nextBucket >= bucketsSize)
321			return NULL;
322		he = buckets[hi->nextBucket++];
323	}
324	hi->entry = he;
325	return he;
326}
327
328void
329HashTable_DebugStats(HashTable *t, const char *name)
330{
331	DEBUG4(HASH, "HashTable %s: size=%u numEntries=%u maxchain=%u\n",
332	    name, t->bucketsSize, t->numEntries, t->maxchain);
333}
334