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[dragonfly.git] / lib / libc / stdlib / hcreate.c
CommitLineData
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1/*
2 * Copyright (c) 2001 Christopher G. Demetriou
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed for the
16 * NetBSD Project. See http://www.netbsd.org/ for
17 * information about NetBSD.
18 * 4. The name of the author may not be used to endorse or promote products
19 * derived from this software without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 *
32 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
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33 *
34 * $NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $
5d0641a4 35 * $FreeBSD: src/lib/libc/stdlib/hcreate.c,v 1.4 2008/07/06 11:31:20 danger Exp $
1de703da 36 * $DragonFly: src/lib/libc/stdlib/hcreate.c,v 1.2 2003/06/17 04:26:46 dillon Exp $
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37 */
38
39/*
40 * hcreate() / hsearch() / hdestroy()
41 *
42 * SysV/XPG4 hash table functions.
43 *
44 * Implementation done based on NetBSD manual page and Solaris manual page,
45 * plus my own personal experience about how they're supposed to work.
46 *
47 * I tried to look at Knuth (as cited by the Solaris manual page), but
48 * nobody had a copy in the office, so...
49 */
50
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51#include <sys/types.h>
52#include <sys/queue.h>
53#include <errno.h>
54#include <search.h>
55#include <stdlib.h>
56#include <string.h>
57
58/*
59 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
60 * ptr machine) without adjusting MAX_BUCKETS_LG2 below.
61 */
62struct internal_entry {
63 SLIST_ENTRY(internal_entry) link;
64 ENTRY ent;
65};
66SLIST_HEAD(internal_head, internal_entry);
67
68#define MIN_BUCKETS_LG2 4
69#define MIN_BUCKETS (1 << MIN_BUCKETS_LG2)
70
71/*
72 * max * sizeof internal_entry must fit into size_t.
73 * assumes internal_entry is <= 32 (2^5) bytes.
74 */
75#define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
76#define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2)
77
78/* Default hash function, from db/hash/hash_func.c */
79extern u_int32_t (*__default_hash)(const void *, size_t);
80
81static struct internal_head *htable;
82static size_t htablesize;
83
84int
85hcreate(size_t nel)
86{
87 size_t idx;
88 unsigned int p2;
89
5d0641a4 90 /* Make sure this is not called when a table already exists. */
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91 if (htable != NULL) {
92 errno = EINVAL;
93 return 0;
94 }
95
96 /* If nel is too small, make it min sized. */
97 if (nel < MIN_BUCKETS)
98 nel = MIN_BUCKETS;
99
5d0641a4 100 /* If it is too large, cap it. */
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101 if (nel > MAX_BUCKETS)
102 nel = MAX_BUCKETS;
103
5d0641a4 104 /* If it is not a power of two in size, round up. */
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105 if ((nel & (nel - 1)) != 0) {
106 for (p2 = 0; nel != 0; p2++)
107 nel >>= 1;
108 nel = 1 << p2;
109 }
110
111 /* Allocate the table. */
112 htablesize = nel;
113 htable = malloc(htablesize * sizeof htable[0]);
114 if (htable == NULL) {
115 errno = ENOMEM;
116 return 0;
117 }
118
119 /* Initialize it. */
120 for (idx = 0; idx < htablesize; idx++)
121 SLIST_INIT(&htable[idx]);
122
123 return 1;
124}
125
126void
127hdestroy(void)
128{
129 struct internal_entry *ie;
130 size_t idx;
131
132 if (htable == NULL)
133 return;
134
135 for (idx = 0; idx < htablesize; idx++) {
136 while (!SLIST_EMPTY(&htable[idx])) {
137 ie = SLIST_FIRST(&htable[idx]);
138 SLIST_REMOVE_HEAD(&htable[idx], link);
139 free(ie->ent.key);
140 free(ie);
141 }
142 }
143 free(htable);
144 htable = NULL;
145}
146
147ENTRY *
148hsearch(ENTRY item, ACTION action)
149{
150 struct internal_head *head;
151 struct internal_entry *ie;
152 uint32_t hashval;
153 size_t len;
154
155 len = strlen(item.key);
156 hashval = (*__default_hash)(item.key, len);
157
158 head = &htable[hashval & (htablesize - 1)];
159 ie = SLIST_FIRST(head);
160 while (ie != NULL) {
161 if (strcmp(ie->ent.key, item.key) == 0)
162 break;
163 ie = SLIST_NEXT(ie, link);
164 }
165
166 if (ie != NULL)
167 return &ie->ent;
168 else if (action == FIND)
169 return NULL;
170
171 ie = malloc(sizeof *ie);
172 if (ie == NULL)
173 return NULL;
174 ie->ent.key = item.key;
175 ie->ent.data = item.data;
176
177 SLIST_INSERT_HEAD(head, ie, link);
178 return &ie->ent;
179}