1/* $NetBSD: hcreate.c,v 1.6 2008/07/21 12:05:43 lukem Exp $ */
2
3/*
4 * Copyright (c) 2001 Christopher G. Demetriou
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
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.
22 *
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.
33 *
34 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
35 */
36
37/*
38 * hcreate() / hsearch() / hdestroy()
39 *
40 * SysV/XPG4 hash table functions.
41 *
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.
44 *
45 * I tried to look at Knuth (as cited by the Solaris manual page), but
46 * nobody had a copy in the office, so...
47 */
48
49#include <sys/cdefs.h>
50#if 0
51#if defined(LIBC_SCCS) && !defined(lint)
52__RCSID("$NetBSD: hcreate.c,v 1.6 2008/07/21 12:05:43 lukem Exp $");
53#endif /* LIBC_SCCS and not lint */
54#endif
55__FBSDID("$FreeBSD: releng/10.3/lib/libc/stdlib/hcreate.c 269491 2014-08-04 00:51:57Z pfg $");
56
57#include <sys/types.h>
58#include <sys/queue.h>
59#include <errno.h>
60#include <search.h>
61#include <stdlib.h>
62#include <string.h>
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 */
68struct internal_entry {
69	SLIST_ENTRY(internal_entry) link;
70	ENTRY ent;
71};
72SLIST_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/* Default hash function, from db/hash/hash_func.c */
85extern u_int32_t (*__default_hash)(const void *, size_t);
86
87static struct internal_head *htable;
88static size_t htablesize;
89
90int
91hcreate(size_t nel)
92{
93	size_t idx;
94	unsigned int p2;
95
96	/* Make sure this is not called when a table already exists. */
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 is too large, cap it. */
107	if (nel > MAX_BUCKETS)
108		nel = MAX_BUCKETS;
109
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++)
113			nel >>= 1;
114		nel = 1 << p2;
115	}
116
117	/* Allocate the table. */
118	htablesize = nel;
119	htable = malloc(htablesize * sizeof htable[0]);
120	if (htable == NULL) {
121		errno = ENOMEM;
122		return 0;
123	}
124
125	/* Initialize it. */
126	for (idx = 0; idx < htablesize; idx++)
127		SLIST_INIT(&htable[idx]);
128
129	return 1;
130}
131
132void
133hdestroy(void)
134{
135	struct internal_entry *ie;
136	size_t idx;
137
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);
146		}
147	}
148	free(htable);
149	htable = NULL;
150}
151
152ENTRY *
153hsearch(ENTRY item, ACTION action)
154{
155	struct internal_head *head;
156	struct internal_entry *ie;
157	uint32_t hashval;
158	size_t len;
159
160	len = strlen(item.key);
161	hashval = (*__default_hash)(item.key, len);
162
163	head = &htable[hashval & (htablesize - 1)];
164	ie = SLIST_FIRST(head);
165	while (ie != NULL) {
166		if (strcmp(ie->ent.key, item.key) == 0)
167			break;
168		ie = SLIST_NEXT(ie, link);
169	}
170
171	if (ie != NULL)
172		return &ie->ent;
173	else if (action == FIND)
174		return NULL;
175
176	ie = malloc(sizeof *ie);
177	if (ie == NULL)
178		return NULL;
179	ie->ent.key = item.key;
180	ie->ent.data = item.data;
181
182	SLIST_INSERT_HEAD(head, ie, link);
183	return &ie->ent;
184}
185