1 /* $NetBSD: hcreate.c,v 1.7 2011/09/14 23:33:51 christos Exp $ */
4 * Copyright (c) 2001 Christopher G. Demetriou
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. The name of the author may not be used to endorse or promote products
16 * derived from this software without specific prior written permission.
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
33 * hcreate() / hsearch() / hdestroy()
35 * SysV/XPG4 hash table functions.
37 * Implementation done based on NetBSD manual page and Solaris manual page,
38 * plus my own personal experience about how they're supposed to work.
40 * I tried to look at Knuth (as cited by the Solaris manual page), but
41 * nobody had a copy in the office, so...
44 #include <sys/cdefs.h>
46 #if defined(LIBC_SCCS) && !defined(lint)
47 __RCSID("$NetBSD: hcreate.c,v 1.8 2011/09/17 16:54:39 christos Exp $");
48 #endif /* LIBC_SCCS and not lint */
50 __FBSDID("$FreeBSD$");
52 #include <sys/types.h>
53 #include <sys/queue.h>
60 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
61 * ptr machine) without adjusting MAX_BUCKETS_LG2 below.
63 struct internal_entry {
64 SLIST_ENTRY(internal_entry) link;
67 SLIST_HEAD(internal_head, internal_entry);
69 #define MIN_BUCKETS_LG2 4
70 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2)
73 * max * sizeof internal_entry must fit into size_t.
74 * assumes internal_entry is <= 32 (2^5) bytes.
76 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
77 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2)
79 /* Default hash function, from db/hash/hash_func.c */
80 extern u_int32_t (*__default_hash)(const void *, size_t);
82 static struct hsearch_data htable;
88 /* Make sure this is not called when a table already exists. */
89 if (htable.table != NULL) {
93 return hcreate_r(nel, &htable);
97 hcreate_r(size_t nel, struct hsearch_data *head)
99 struct internal_head *table;
104 /* If nel is too small, make it min sized. */
105 if (nel < MIN_BUCKETS)
108 /* If it is too large, cap it. */
109 if (nel > MAX_BUCKETS)
112 /* If it is not a power of two in size, round up. */
113 if ((nel & (nel - 1)) != 0) {
114 for (p2 = 0; nel != 0; p2++)
119 /* Allocate the table. */
122 p = malloc(nel * sizeof table[0]);
131 for (idx = 0; idx < nel; idx++)
132 SLIST_INIT(&table[idx]);
144 hdestroy_r(struct hsearch_data *head)
146 struct internal_entry *ie;
149 struct internal_head *table;
158 for (idx = 0; idx < head->size; idx++) {
159 while (!SLIST_EMPTY(&table[idx])) {
160 ie = SLIST_FIRST(&table[idx]);
161 SLIST_REMOVE_HEAD(&table[idx], link);
169 hsearch(ENTRY item, ACTION action)
172 (void)hsearch_r(item, action, &ep, &htable);
177 hsearch_r(ENTRY item, ACTION action, ENTRY **itemp, struct hsearch_data *head)
179 struct internal_head *table, *chain;
180 struct internal_entry *ie;
188 len = strlen(item.key);
189 hashval = (*__default_hash)(item.key, len);
191 chain = &table[hashval & (head->size - 1)];
192 ie = SLIST_FIRST(chain);
194 if (strcmp(ie->ent.key, item.key) == 0)
196 ie = SLIST_NEXT(ie, link);
202 } else if (action == FIND) {
208 ie = malloc(sizeof *ie);
211 ie->ent.key = item.key;
212 ie->ent.data = item.data;
214 SLIST_INSERT_HEAD(chain, ie, link);