1 /* $NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross 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. All advertising materials mentioning features or use of this software
16 * must display the following acknowledgement:
17 * This product includes software developed for the
18 * NetBSD Project. See http://www.netbsd.org/ for
19 * information about NetBSD.
20 * 4. The name of the author may not be used to endorse or promote products
21 * derived from this software without specific prior written permission.
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
26 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
27 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
28 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
32 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
38 * hcreate() / hsearch() / hdestroy()
40 * SysV/XPG4 hash table functions.
42 * Implementation done based on NetBSD manual page and Solaris manual page,
43 * plus my own personal experience about how they're supposed to work.
45 * I tried to look at Knuth (as cited by the Solaris manual page), but
46 * nobody had a copy in the office, so...
49 #include <sys/cdefs.h>
51 #if defined(LIBC_SCCS) && !defined(lint)
52 __RCSID("$NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $");
53 #endif /* LIBC_SCCS and not lint */
55 __FBSDID("$FreeBSD$");
57 #include <sys/types.h>
58 #include <sys/queue.h>
65 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
66 * ptr machine) without adjusting MAX_BUCKETS_LG2 below.
68 struct internal_entry {
69 SLIST_ENTRY(internal_entry) link;
72 SLIST_HEAD(internal_head, internal_entry);
74 #define MIN_BUCKETS_LG2 4
75 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2)
78 * max * sizeof internal_entry must fit into size_t.
79 * assumes internal_entry is <= 32 (2^5) bytes.
81 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
82 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2)
84 /* Default hash function, from db/hash/hash_func.c */
85 extern u_int32_t (*__default_hash)(const void *, size_t);
87 static struct internal_head *htable;
88 static size_t htablesize;
96 /* Make sure this is not called when a table already exists. */
102 /* If nel is too small, make it min sized. */
103 if (nel < MIN_BUCKETS)
106 /* If it is too large, cap it. */
107 if (nel > MAX_BUCKETS)
110 /* If it is not a power of two in size, round up. */
111 if ((nel & (nel - 1)) != 0) {
112 for (p2 = 0; nel != 0; p2++)
117 /* Allocate the table. */
119 htable = malloc(htablesize * sizeof htable[0]);
120 if (htable == NULL) {
126 for (idx = 0; idx < htablesize; idx++)
127 SLIST_INIT(&htable[idx]);
135 struct internal_entry *ie;
141 for (idx = 0; idx < htablesize; idx++) {
142 while (!SLIST_EMPTY(&htable[idx])) {
143 ie = SLIST_FIRST(&htable[idx]);
144 SLIST_REMOVE_HEAD(&htable[idx], link);
154 hsearch(ENTRY item, ACTION action)
156 struct internal_head *head;
157 struct internal_entry *ie;
161 len = strlen(item.key);
162 hashval = (*__default_hash)(item.key, len);
164 head = &htable[hashval & (htablesize - 1)];
165 ie = SLIST_FIRST(head);
167 if (strcmp(ie->ent.key, item.key) == 0)
169 ie = SLIST_NEXT(ie, link);
174 else if (action == FIND)
177 ie = malloc(sizeof *ie);
180 ie->ent.key = item.key;
181 ie->ent.data = item.data;
183 SLIST_INSERT_HEAD(head, ie, link);