1 /* $NetBSD: hash.c,v 1.72 2022/02/09 21:09:24 rillig Exp $ */
4 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
7 * This code is derived from software contributed to Berkeley by
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
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.
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
36 * Copyright (c) 1988, 1989 by Adam de Boor
37 * Copyright (c) 1989 by Berkeley Softworks
38 * All rights reserved.
40 * This code is derived from software contributed to Berkeley by
43 * Redistribution and use in source and binary forms, with or without
44 * modification, are permitted provided that the following conditions
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.
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
72 /* Hash tables with string keys. */
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 $");
80 * The ratio of # entries to # buckets at which we rebuild the table to
83 #define rebuildLimit 3
85 /* This hash function matches Gosling's Emacs and java.lang.String. */
87 Hash_String(const char *key, const char **out_keyEnd)
93 for (p = key; *p != '\0'; p++)
94 h = 31 * h + (unsigned char)*p;
100 /* This hash function matches Gosling's Emacs and java.lang.String. */
102 Hash_Substring(Substring key)
108 for (p = key.start; p != key.end; p++)
109 h = 31 * h + (unsigned char)*p;
114 HashTable_Find(HashTable *t, Substring key, unsigned int h)
117 unsigned int chainlen = 0;
118 size_t keyLen = Substring_Length(key);
120 #ifdef DEBUG_HASH_LOOKUP
121 DEBUG4(HASH, "HashTable_Find: %p h=%08x key=%.*s\n",
122 t, h, (int)keyLen, key.start);
125 for (e = t->buckets[h & t->bucketsMask]; e != NULL; e = e->next) {
127 if (e->key_hash == h &&
128 strncmp(e->key, key.start, keyLen) == 0 &&
129 e->key[keyLen] == '\0')
133 if (chainlen > t->maxchain)
134 t->maxchain = chainlen;
139 /* Set up the hash table. */
141 HashTable_Init(HashTable *t)
143 unsigned int n = 16, i;
144 HashEntry **buckets = bmake_malloc(sizeof *buckets * n);
145 for (i = 0; i < n; i++)
148 t->buckets = buckets;
151 t->bucketsMask = n - 1;
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.
160 HashTable_Done(HashTable *t)
162 HashEntry **buckets = t->buckets;
163 size_t i, n = t->bucketsSize;
165 for (i = 0; i < n; i++) {
166 HashEntry *he = buckets[i];
168 HashEntry *next = he->next;
180 /* Find the entry corresponding to the key, or return NULL. */
182 HashTable_FindEntry(HashTable *t, const char *key)
185 unsigned int h = Hash_String(key, &keyEnd);
186 return HashTable_Find(t, Substring_Init(key, keyEnd), h);
189 /* Find the value corresponding to the key, or return NULL. */
191 HashTable_FindValue(HashTable *t, const char *key)
193 HashEntry *he = HashTable_FindEntry(t, key);
194 return he != NULL ? he->value : NULL;
198 * Find the value corresponding to the key and the precomputed hash,
202 HashTable_FindValueBySubstringHash(HashTable *t, Substring key, unsigned int h)
204 HashEntry *he = HashTable_Find(t, key, h);
205 return he != NULL ? he->value : NULL;
209 * Make the hash table larger. Any bucket numbers from the old table become
210 * invalid; the hash codes stay valid though.
213 HashTable_Enlarge(HashTable *t)
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);
222 for (i = 0; i < newSize; i++)
223 newBuckets[i] = NULL;
225 for (i = 0; i < oldSize; i++) {
226 HashEntry *he = oldBuckets[i];
228 HashEntry *next = he->next;
229 he->next = newBuckets[he->key_hash & newMask];
230 newBuckets[he->key_hash & newMask] = he;
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);
246 * Find or create an entry corresponding to the key.
247 * Return in out_isNew whether a new entry has been created.
250 HashTable_CreateEntry(HashTable *t, const char *key, bool *out_isNew)
253 unsigned int h = Hash_String(key, &keyEnd);
254 HashEntry *he = HashTable_Find(t, Substring_Init(key, keyEnd), h);
257 if (out_isNew != NULL)
262 if (t->numEntries >= rebuildLimit * t->bucketsSize)
263 HashTable_Enlarge(t);
265 he = bmake_malloc(sizeof *he + (size_t)(keyEnd - key));
268 memcpy(he->key, key, (size_t)(keyEnd - key) + 1);
270 he->next = t->buckets[h & t->bucketsMask];
271 t->buckets[h & t->bucketsMask] = he;
274 if (out_isNew != NULL)
280 HashTable_Set(HashTable *t, const char *key, void *value)
282 HashEntry *he = HashTable_CreateEntry(t, key, NULL);
283 HashEntry_Set(he, value);
286 /* Delete the entry from the table, don't free the value of the entry. */
288 HashTable_DeleteEntry(HashTable *t, HashEntry *he)
290 HashEntry **ref = &t->buckets[he->key_hash & t->bucketsMask];
293 for (; (p = *ref) != NULL; ref = &p->next) {
305 * Return the next entry in the hash table, or NULL if the end of the table
309 HashIter_Next(HashIter *hi)
311 HashTable *t = hi->table;
312 HashEntry *he = hi->entry;
313 HashEntry **buckets = t->buckets;
314 unsigned int bucketsSize = t->bucketsSize;
317 he = he->next; /* skip the most recently returned entry */
319 while (he == NULL) { /* find the next nonempty chain */
320 if (hi->nextBucket >= bucketsSize)
322 he = buckets[hi->nextBucket++];
329 HashTable_DebugStats(HashTable *t, const char *name)
331 DEBUG4(HASH, "HashTable %s: size=%u numEntries=%u maxchain=%u\n",
332 name, t->bucketsSize, t->numEntries, t->maxchain);