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 */
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
84static struct internal_head *htable;
85static size_t htablesize;
86
87int
88hcreate(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
131void
132hdestroy(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
153ENTRY *
154hsearch(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