1 /* $NetBSD: hash.c,v 1.79 2024/07/07 09:37:00 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" */
77 MAKE_RCSID("$NetBSD: hash.c,v 1.79 2024/07/07 09:37:00 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 *he;
117 size_t keyLen = Substring_Length(key);
118
119 #ifdef DEBUG_HASH_LOOKUP
120 DEBUG4(HASH, "HashTable_Find: %p h=%08x key=%.*s\n",
121 t, h, (int)keyLen, key.start);
122 #endif
123
124 for (he = t->buckets[h & t->bucketsMask]; he != NULL; he = he->next) {
125 if (he->hash == h &&
126 strncmp(he->key, key.start, keyLen) == 0 &&
127 he->key[keyLen] == '\0')
128 break;
129 }
130
131 return he;
132 }
133
134 /* Set up the hash table. */
135 void
HashTable_Init(HashTable * t)136 HashTable_Init(HashTable *t)
137 {
138 unsigned int n = 16, i;
139 HashEntry **buckets = bmake_malloc(sizeof *buckets * n);
140 for (i = 0; i < n; i++)
141 buckets[i] = NULL;
142
143 t->buckets = buckets;
144 t->bucketsSize = n;
145 t->numEntries = 0;
146 t->bucketsMask = n - 1;
147 }
148
149 /*
150 * Remove everything from the hash table and free up the memory for the keys
151 * of the hash table, but not for the values associated to these keys.
152 */
153 void
HashTable_Done(HashTable * t)154 HashTable_Done(HashTable *t)
155 {
156 HashEntry **buckets = t->buckets;
157 size_t i, n = t->bucketsSize;
158
159 for (i = 0; i < n; i++) {
160 HashEntry *he = buckets[i];
161 while (he != NULL) {
162 HashEntry *next = he->next;
163 free(he);
164 he = next;
165 }
166 }
167
168 free(t->buckets);
169 #ifdef CLEANUP
170 t->buckets = NULL;
171 #endif
172 }
173
174 /* Find the entry corresponding to the key, or return NULL. */
175 HashEntry *
HashTable_FindEntry(HashTable * t,const char * key)176 HashTable_FindEntry(HashTable *t, const char *key)
177 {
178 const char *keyEnd;
179 unsigned int h = Hash_String(key, &keyEnd);
180 return HashTable_Find(t, Substring_Init(key, keyEnd), h);
181 }
182
183 /* Find the value corresponding to the key, or return NULL. */
184 void *
HashTable_FindValue(HashTable * t,const char * key)185 HashTable_FindValue(HashTable *t, const char *key)
186 {
187 HashEntry *he = HashTable_FindEntry(t, key);
188 return he != NULL ? he->value : NULL;
189 }
190
191 /*
192 * Find the value corresponding to the key and the precomputed hash,
193 * or return NULL.
194 */
195 void *
HashTable_FindValueBySubstringHash(HashTable * t,Substring key,unsigned int h)196 HashTable_FindValueBySubstringHash(HashTable *t, Substring key, unsigned int h)
197 {
198 HashEntry *he = HashTable_Find(t, key, h);
199 return he != NULL ? he->value : NULL;
200 }
201
202 static unsigned
HashTable_MaxChain(const HashTable * t)203 HashTable_MaxChain(const HashTable *t)
204 {
205 unsigned b, cl, max_cl = 0;
206 for (b = 0; b < t->bucketsSize; b++) {
207 const HashEntry *he = t->buckets[b];
208 for (cl = 0; he != NULL; he = he->next)
209 cl++;
210 if (cl > max_cl)
211 max_cl = cl;
212 }
213 return max_cl;
214 }
215
216 /*
217 * Make the hash table larger. Any bucket numbers from the old table become
218 * invalid; the hash values stay valid though.
219 */
220 static void
HashTable_Enlarge(HashTable * t)221 HashTable_Enlarge(HashTable *t)
222 {
223 unsigned int oldSize = t->bucketsSize;
224 HashEntry **oldBuckets = t->buckets;
225 unsigned int newSize = 2 * oldSize;
226 unsigned int newMask = newSize - 1;
227 HashEntry **newBuckets = bmake_malloc(sizeof *newBuckets * newSize);
228 size_t i;
229
230 for (i = 0; i < newSize; i++)
231 newBuckets[i] = NULL;
232
233 for (i = 0; i < oldSize; i++) {
234 HashEntry *he = oldBuckets[i];
235 while (he != NULL) {
236 HashEntry *next = he->next;
237 he->next = newBuckets[he->hash & newMask];
238 newBuckets[he->hash & newMask] = he;
239 he = next;
240 }
241 }
242
243 free(oldBuckets);
244
245 t->bucketsSize = newSize;
246 t->bucketsMask = newMask;
247 t->buckets = newBuckets;
248 DEBUG4(HASH, "HashTable_Enlarge: %p size=%d entries=%d maxchain=%d\n",
249 (void *)t, t->bucketsSize, t->numEntries, HashTable_MaxChain(t));
250 }
251
252 /*
253 * Find or create an entry corresponding to the key.
254 * Return in out_isNew whether a new entry has been created.
255 */
256 HashEntry *
HashTable_CreateEntry(HashTable * t,const char * key,bool * out_isNew)257 HashTable_CreateEntry(HashTable *t, const char *key, bool *out_isNew)
258 {
259 const char *keyEnd;
260 unsigned int h = Hash_String(key, &keyEnd);
261 HashEntry *he = HashTable_Find(t, Substring_Init(key, keyEnd), h);
262
263 if (he != NULL) {
264 if (out_isNew != NULL)
265 *out_isNew = false;
266 return he;
267 }
268
269 if (t->numEntries >= rebuildLimit * t->bucketsSize)
270 HashTable_Enlarge(t);
271
272 he = bmake_malloc(sizeof *he + (size_t)(keyEnd - key));
273 he->value = NULL;
274 he->hash = h;
275 memcpy(he->key, key, (size_t)(keyEnd - key) + 1);
276
277 he->next = t->buckets[h & t->bucketsMask];
278 t->buckets[h & t->bucketsMask] = he;
279 t->numEntries++;
280
281 if (out_isNew != NULL)
282 *out_isNew = true;
283 return he;
284 }
285
286 void
HashTable_Set(HashTable * t,const char * key,void * value)287 HashTable_Set(HashTable *t, const char *key, void *value)
288 {
289 HashEntry *he = HashTable_CreateEntry(t, key, NULL);
290 HashEntry_Set(he, value);
291 }
292
293 /* Delete the entry from the table, don't free the value of the entry. */
294 void
HashTable_DeleteEntry(HashTable * t,HashEntry * he)295 HashTable_DeleteEntry(HashTable *t, HashEntry *he)
296 {
297 HashEntry **ref = &t->buckets[he->hash & t->bucketsMask];
298
299 for (; *ref != he; ref = &(*ref)->next)
300 continue;
301 *ref = he->next;
302 free(he);
303 t->numEntries--;
304 }
305
306 /*
307 * Place the next entry from the hash table in hi->entry, or return false if
308 * the end of the table is reached.
309 */
310 bool
HashIter_Next(HashIter * hi)311 HashIter_Next(HashIter *hi)
312 {
313 HashTable *t = hi->table;
314 HashEntry *he = hi->entry;
315 HashEntry **buckets = t->buckets;
316 unsigned int bucketsSize = t->bucketsSize;
317
318 if (he != NULL)
319 he = he->next; /* skip the most recently returned entry */
320
321 while (he == NULL) { /* find the next nonempty chain */
322 if (hi->nextBucket >= bucketsSize)
323 return false;
324 he = buckets[hi->nextBucket++];
325 }
326 hi->entry = he;
327 return true;
328 }
329
330 void
HashTable_DebugStats(const HashTable * t,const char * name)331 HashTable_DebugStats(const HashTable *t, const char *name)
332 {
333 DEBUG4(HASH, "HashTable \"%s\": size=%u entries=%u maxchain=%u\n",
334 name, t->bucketsSize, t->numEntries, HashTable_MaxChain(t));
335 }
336