1 /* $OpenBSD: hcreate.c,v 1.7 2016/05/29 20:47:49 guenther Exp $ */
2 /* $NetBSD: hcreate.c,v 1.5 2004/04/23 02:48:12 simonb Exp $ */
3
4 /*
5 * Copyright (c) 2001 Christopher G. Demetriou
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed for the
19 * NetBSD Project. See http://www.NetBSD.org/ for
20 * information about NetBSD.
21 * 4. The name of the author may not be used to endorse or promote products
22 * derived from this software without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
25 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
26 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
27 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
28 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
29 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
30 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
31 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
32 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
33 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34 *
35 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
36 */
37
38 /*
39 * hcreate() / hsearch() / hdestroy()
40 *
41 * SysV/XPG4 hash table functions.
42 *
43 * Implementation done based on NetBSD manual page and Solaris manual page,
44 * plus my own personal experience about how they're supposed to work.
45 *
46 * I tried to look at Knuth (as cited by the Solaris manual page), but
47 * nobody had a copy in the office, so...
48 */
49
50 #include <assert.h>
51 #include <errno.h>
52 #include <stdint.h>
53 #include <search.h>
54 #include <stdlib.h>
55 #include <string.h>
56 #include <sys/queue.h>
57
58 #include <db.h> /* for __default_hash */
59
60 #ifndef _DIAGASSERT
61 #define _DIAGASSERT(x)
62 #endif
63
64 /*
65 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
66 * ptr machine) without adjusting MAX_BUCKETS_LG2 below.
67 */
68 struct internal_entry {
69 SLIST_ENTRY(internal_entry) link;
70 ENTRY ent;
71 };
72 SLIST_HEAD(internal_head, internal_entry);
73
74 #define MIN_BUCKETS_LG2 4
75 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2)
76
77 /*
78 * max * sizeof internal_entry must fit into size_t.
79 * assumes internal_entry is <= 32 (2^5) bytes.
80 */
81 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
82 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2)
83
84 static struct internal_head *htable;
85 static size_t htablesize;
86
87 int
hcreate(size_t nel)88 hcreate(size_t nel)
89 {
90 size_t idx;
91 unsigned int p2;
92
93 /* Make sure this isn't called when a table already exists. */
94 _DIAGASSERT(htable == NULL);
95 if (htable != NULL) {
96 errno = EINVAL;
97 return 0;
98 }
99
100 /* If nel is too small, make it min sized. */
101 if (nel < MIN_BUCKETS)
102 nel = MIN_BUCKETS;
103
104 /* If it's too large, cap it. */
105 if (nel > MAX_BUCKETS)
106 nel = MAX_BUCKETS;
107
108 /* If it's is not a power of two in size, round up. */
109 if ((nel & (nel - 1)) != 0) {
110 for (p2 = 0; nel != 0; p2++)
111 nel >>= 1;
112 _DIAGASSERT(p2 <= MAX_BUCKETS_LG2);
113 nel = 1 << p2;
114 }
115
116 /* Allocate the table. */
117 htablesize = nel;
118 htable = calloc(htablesize, sizeof htable[0]);
119 if (htable == NULL) {
120 errno = ENOMEM;
121 return 0;
122 }
123
124 /* Initialize it. */
125 for (idx = 0; idx < htablesize; idx++)
126 SLIST_INIT(&htable[idx]);
127
128 return 1;
129 }
130
131 void
hdestroy(void)132 hdestroy(void)
133 {
134 struct internal_entry *ie;
135 size_t idx;
136
137 _DIAGASSERT(htable != NULL);
138 if (htable == NULL)
139 return;
140
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);
145 free(ie->ent.key);
146 free(ie);
147 }
148 }
149 free(htable);
150 htable = NULL;
151 }
152
153 ENTRY *
hsearch(ENTRY item,ACTION action)154 hsearch(ENTRY item, ACTION action)
155 {
156 struct internal_head *head;
157 struct internal_entry *ie;
158 uint32_t hashval;
159 size_t len;
160
161 _DIAGASSERT(htable != NULL);
162 _DIAGASSERT(item.key != NULL);
163 _DIAGASSERT(action == ENTER || action == FIND);
164
165 len = strlen(item.key);
166 hashval = __default_hash(item.key, len);
167
168 head = &htable[hashval & (htablesize - 1)];
169 ie = SLIST_FIRST(head);
170 while (ie != NULL) {
171 if (strcmp(ie->ent.key, item.key) == 0)
172 break;
173 ie = SLIST_NEXT(ie, link);
174 }
175
176 if (ie != NULL)
177 return &ie->ent;
178 else if (action == FIND)
179 return NULL;
180
181 ie = malloc(sizeof *ie);
182 if (ie == NULL)
183 return NULL;
184 ie->ent.key = item.key;
185 ie->ent.data = item.data;
186
187 SLIST_INSERT_HEAD(head, ie, link);
188 return &ie->ent;
189 }
190