1 /* $OpenBSD: hcreate.c,v 1.2 2005/08/08 08:05:36 espie 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 "namespace.h"
51 #include <assert.h>
52 #include <errno.h>
53 #include <inttypes.h>
54 #include <search.h>
55 #include <stdlib.h>
56 #include <string.h>
57 #include <sys/queue.h>
58
59 #ifndef _DIAGASSERT
60 #define _DIAGASSERT
61 #endif
62
63 /*
64 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
65 * ptr machine) without adjusting MAX_BUCKETS_LG2 below.
66 */
67 struct internal_entry {
68 SLIST_ENTRY(internal_entry) link;
69 ENTRY ent;
70 };
71 SLIST_HEAD(internal_head, internal_entry);
72
73 #define MIN_BUCKETS_LG2 4
74 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2)
75
76 /*
77 * max * sizeof internal_entry must fit into size_t.
78 * assumes internal_entry is <= 32 (2^5) bytes.
79 */
80 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
81 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2)
82
83 /* Default hash function, from db/hash/hash_func.c */
84 extern u_int32_t (*__default_hash)(const void *, size_t);
85
86 static struct internal_head *htable;
87 static size_t htablesize;
88
89 int
hcreate(size_t nel)90 hcreate(size_t nel)
91 {
92 size_t idx;
93 unsigned int p2;
94
95 /* Make sure this isn't called when a table already exists. */
96 _DIAGASSERT(htable == NULL);
97 if (htable != NULL) {
98 errno = EINVAL;
99 return 0;
100 }
101
102 /* If nel is too small, make it min sized. */
103 if (nel < MIN_BUCKETS)
104 nel = MIN_BUCKETS;
105
106 /* If it's too large, cap it. */
107 if (nel > MAX_BUCKETS)
108 nel = MAX_BUCKETS;
109
110 /* If it's is not a power of two in size, round up. */
111 if ((nel & (nel - 1)) != 0) {
112 for (p2 = 0; nel != 0; p2++)
113 nel >>= 1;
114 _DIAGASSERT(p2 <= MAX_BUCKETS_LG2);
115 nel = 1 << p2;
116 }
117
118 /* Allocate the table. */
119 htablesize = nel;
120 htable = malloc(htablesize * sizeof htable[0]);
121 if (htable == NULL) {
122 errno = ENOMEM;
123 return 0;
124 }
125
126 /* Initialize it. */
127 for (idx = 0; idx < htablesize; idx++)
128 SLIST_INIT(&htable[idx]);
129
130 return 1;
131 }
132
133 void
hdestroy(void)134 hdestroy(void)
135 {
136 struct internal_entry *ie;
137 size_t idx;
138
139 _DIAGASSERT(htable != NULL);
140 if (htable == NULL)
141 return;
142
143 for (idx = 0; idx < htablesize; idx++) {
144 while (!SLIST_EMPTY(&htable[idx])) {
145 ie = SLIST_FIRST(&htable[idx]);
146 SLIST_REMOVE_HEAD(&htable[idx], link);
147 free(ie->ent.key);
148 free(ie);
149 }
150 }
151 free(htable);
152 htable = NULL;
153 }
154
155 ENTRY *
hsearch(ENTRY item,ACTION action)156 hsearch(ENTRY item, ACTION action)
157 {
158 struct internal_head *head;
159 struct internal_entry *ie;
160 uint32_t hashval;
161 size_t len;
162
163 _DIAGASSERT(htable != NULL);
164 _DIAGASSERT(item.key != NULL);
165 _DIAGASSERT(action == ENTER || action == FIND);
166
167 len = strlen(item.key);
168 hashval = (*__default_hash)(item.key, len);
169
170 head = &htable[hashval & (htablesize - 1)];
171 ie = SLIST_FIRST(head);
172 while (ie != NULL) {
173 if (strcmp(ie->ent.key, item.key) == 0)
174 break;
175 ie = SLIST_NEXT(ie, link);
176 }
177
178 if (ie != NULL)
179 return &ie->ent;
180 else if (action == FIND)
181 return NULL;
182
183 ie = malloc(sizeof *ie);
184 if (ie == NULL)
185 return NULL;
186 ie->ent.key = item.key;
187 ie->ent.data = item.data;
188
189 SLIST_INSERT_HEAD(head, ie, link);
190 return &ie->ent;
191 }
192