Sync usage with man page.
[netbsd-mini2440.git] / usr.bin / config / hash.c
blob140f6729b6ae9aaa059ca550f0f29c930ae6093f
1 /* $NetBSD: hash.c,v 1.5 2006/12/27 17:50:27 alc Exp $ */
3 /*
4 * Copyright (c) 1992, 1993
5 * The Regents of the University of California. All rights reserved.
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
11 * All advertising materials mentioning features or use of this software
12 * must display the following acknowledgement:
13 * This product includes software developed by the University of
14 * California, Lawrence Berkeley Laboratories.
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution.
24 * 3. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
40 * from: @(#)hash.c 8.1 (Berkeley) 6/6/93
43 #if HAVE_NBTOOL_CONFIG_H
44 #include "nbtool_config.h"
45 #endif
47 #include <sys/param.h>
48 #include <assert.h>
49 #include <stdlib.h>
50 #include <string.h>
51 #include <util.h>
52 #include "defs.h"
55 * Interned strings are kept in a hash table. By making each string
56 * unique, the program can compare strings by comparing pointers.
58 struct hashent {
59 // XXXLUKEM: a SIMPLEQ might be more appropriate
60 TAILQ_ENTRY(hashent) h_next;
61 const char *h_name; /* the string */
62 u_int h_hash; /* its hash value */
63 void *h_value; /* other values (for name=value) */
65 struct hashtab {
66 size_t ht_size; /* size (power of 2) */
67 u_int ht_mask; /* == ht_size - 1 */
68 u_int ht_used; /* number of entries used */
69 u_int ht_lim; /* when to expand */
70 TAILQ_HEAD(hashenthead, hashent) *ht_tab;
73 static struct hashtab strings;
76 * HASHFRACTION controls ht_lim, which in turn controls the average chain
77 * length. We allow a few entries, on average, as comparing them is usually
78 * cheap (the h_hash values prevent a strcmp).
80 #define HASHFRACTION(sz) ((sz) * 3 / 2)
82 static void ht_expand(struct hashtab *);
83 static void ht_init(struct hashtab *, size_t);
84 static inline u_int hash(const char *);
85 static inline struct hashent *newhashent(const char *, u_int);
88 * Initialize a new hash table. The size must be a power of 2.
90 static void
91 ht_init(struct hashtab *ht, size_t sz)
93 u_int n;
95 ht->ht_tab = emalloc(sz * sizeof (ht->ht_tab[0]));
96 ht->ht_size = sz;
97 ht->ht_mask = sz - 1;
98 for (n = 0; n < sz; n++)
99 TAILQ_INIT(&ht->ht_tab[n]);
100 ht->ht_used = 0;
101 ht->ht_lim = HASHFRACTION(sz);
105 * Expand an existing hash table.
107 static void
108 ht_expand(struct hashtab *ht)
110 struct hashenthead *h, *oldh;
111 struct hashent *p;
112 u_int n, i;
114 n = ht->ht_size * 2;
115 h = emalloc(n * sizeof *h);
116 for (i = 0; i < n; i++)
117 TAILQ_INIT(&h[i]);
118 oldh = ht->ht_tab;
119 n--;
120 for (i = 0; i < ht->ht_size; i++) {
121 while ((p = TAILQ_FIRST(&oldh[i])) != NULL) {
122 TAILQ_REMOVE(&oldh[i], p, h_next);
123 // XXXLUKEM: really should be TAILQ_INSERT_TAIL
124 TAILQ_INSERT_HEAD(&h[p->h_hash & n], p, h_next);
127 free(ht->ht_tab);
128 ht->ht_tab = h;
129 ht->ht_mask = n;
130 ht->ht_size = ++n;
131 ht->ht_lim = HASHFRACTION(n);
135 * Make a new hash entry, setting its h_next to NULL.
136 * If the free list is not empty, use the first entry from there,
137 * otherwise allocate a new entry.
139 static inline struct hashent *
140 newhashent(const char *name, u_int h)
142 struct hashent *hp;
144 hp = ecalloc(1, sizeof(*hp));
146 hp->h_name = name;
147 hp->h_hash = h;
148 return (hp);
152 * Hash a string.
154 static inline u_int
155 hash(const char *str)
157 u_int h;
159 for (h = 0; *str;)
160 h = (h << 5) + h + *str++;
161 return (h);
164 void
165 initintern(void)
168 ht_init(&strings, 128);
172 * Generate a single unique copy of the given string. We expect this
173 * function to be used frequently, so it should be fast.
175 const char *
176 intern(const char *s)
178 struct hashtab *ht;
179 struct hashent *hp;
180 struct hashenthead *hpp;
181 u_int h;
182 char *p;
184 ht = &strings;
185 h = hash(s);
186 hpp = &ht->ht_tab[h & ht->ht_mask];
187 TAILQ_FOREACH(hp, hpp, h_next) {
188 if (hp->h_hash == h && strcmp(hp->h_name, s) == 0)
189 return (hp->h_name);
191 p = estrdup(s);
192 hp = newhashent(p, h);
193 TAILQ_INSERT_TAIL(hpp, hp, h_next);
194 if (++ht->ht_used > ht->ht_lim)
195 ht_expand(ht);
196 return (p);
199 struct hashtab *
200 ht_new(void)
202 struct hashtab *ht;
204 ht = ecalloc(1, sizeof *ht);
205 ht_init(ht, 8);
206 return (ht);
209 void
210 ht_free(struct hashtab *ht)
212 size_t i;
213 struct hashent *hp;
214 struct hashenthead *hpp;
216 for (i = 0; i < ht->ht_size; i++) {
217 hpp = &ht->ht_tab[i];
218 while ((hp = TAILQ_FIRST(hpp)) != NULL) {
219 TAILQ_REMOVE(hpp, hp, h_next);
220 free(hp);
221 ht->ht_used--;
225 assert(ht->ht_used == 0);
226 free(ht->ht_tab);
227 free(ht);
231 * Insert and/or replace.
234 ht_insrep(struct hashtab *ht, const char *nam, void *val, int replace)
236 struct hashent *hp;
237 struct hashenthead *hpp;
238 u_int h;
240 h = hash(nam);
241 hpp = &ht->ht_tab[h & ht->ht_mask];
242 TAILQ_FOREACH(hp, hpp, h_next) {
243 if (hp->h_name == nam) {
244 if (replace)
245 hp->h_value = val;
246 return (1);
249 hp = newhashent(nam, h);
250 TAILQ_INSERT_TAIL(hpp, hp, h_next);
251 hp->h_value = val;
252 if (++ht->ht_used > ht->ht_lim)
253 ht_expand(ht);
254 return (0);
258 * Remove.
261 ht_remove(struct hashtab *ht, const char *name)
263 struct hashent *hp;
264 struct hashenthead *hpp;
265 u_int h;
267 h = hash(name);
268 hpp = &ht->ht_tab[h & ht->ht_mask];
270 TAILQ_FOREACH(hp, hpp, h_next) {
271 if (hp->h_name != name)
272 continue;
273 TAILQ_REMOVE(hpp, hp, h_next);
275 free(hp);
276 ht->ht_used--;
277 return (0);
279 return (1);
282 void *
283 ht_lookup(struct hashtab *ht, const char *nam)
285 struct hashent *hp;
286 struct hashenthead *hpp;
287 u_int h;
289 h = hash(nam);
290 hpp = &ht->ht_tab[h & ht->ht_mask];
291 TAILQ_FOREACH(hp, hpp, h_next)
292 if (hp->h_name == nam)
293 return (hp->h_value);
294 return (NULL);
298 * first parameter to callback is the entry name from the hash table
299 * second parameter is the value from the hash table
300 * third argument is passed through from the "arg" parameter to ht_enumerate()
304 ht_enumerate(struct hashtab *ht, ht_callback cbfunc, void *arg)
306 struct hashent *hp;
307 struct hashenthead *hpp;
308 size_t i;
309 int rval = 0;
311 for (i = 0; i < ht->ht_size; i++) {
312 hpp = &ht->ht_tab[i];
313 TAILQ_FOREACH(hp, hpp, h_next)
314 rval += (*cbfunc)(hp->h_name, hp->h_value, arg);
316 return rval;