1 /* $NetBSD: hash.c,v 1.72 2022/02/09 21:09:24 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. */
73
74 #include "make.h"
75
76 /* "@(#)hash.c 8.1 (Berkeley) 6/6/93" */
77 MAKE_RCSID("$NetBSD: hash.c,v 1.72 2022/02/09 21:09:24 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. */
86 static unsigned int
Hash_String(const char * key,const char ** out_keyEnd)87 Hash_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. */
101 unsigned int
Hash_Substring(Substring key)102 Hash_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
113 static HashEntry *
HashTable_Find(HashTable * t,Substring key,unsigned int h)114 HashTable_Find(HashTable *t, Substring key, unsigned int h)
115 {
116 HashEntry *e;
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 (e = t->buckets[h & t->bucketsMask]; e != NULL; e = e->next) {
126 chainlen++;
127 if (e->key_hash == h &&
128 strncmp(e->key, key.start, keyLen) == 0 &&
129 e->key[keyLen] == '\0')
130 break;
131 }
132
133 if (chainlen > t->maxchain)
134 t->maxchain = chainlen;
135
136 return e;
137 }
138
139 /* Set up the hash table. */
140 void
HashTable_Init(HashTable * t)141 HashTable_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 */
159 void
HashTable_Done(HashTable * t)160 HashTable_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. */
181 HashEntry *
HashTable_FindEntry(HashTable * t,const char * key)182 HashTable_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. */
190 void *
HashTable_FindValue(HashTable * t,const char * key)191 HashTable_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 */
201 void *
HashTable_FindValueBySubstringHash(HashTable * t,Substring key,unsigned int h)202 HashTable_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 codes stay valid though.
211 */
212 static void
HashTable_Enlarge(HashTable * t)213 HashTable_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->key_hash & newMask];
230 newBuckets[he->key_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 */
249 HashEntry *
HashTable_CreateEntry(HashTable * t,const char * key,bool * out_isNew)250 HashTable_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->key_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
279 void
HashTable_Set(HashTable * t,const char * key,void * value)280 HashTable_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. */
287 void
HashTable_DeleteEntry(HashTable * t,HashEntry * he)288 HashTable_DeleteEntry(HashTable *t, HashEntry *he)
289 {
290 HashEntry **ref = &t->buckets[he->key_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 */
308 HashEntry *
HashIter_Next(HashIter * hi)309 HashIter_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
328 void
HashTable_DebugStats(HashTable * t,const char * name)329 HashTable_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