1/* $NetBSD: hcreate.c,v 1.7 2011/09/14 23:33:51 christos 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. The name of the author may not be used to endorse or promote products
16 *    derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
30 */
31
32/*
33 * hcreate() / hsearch() / hdestroy()
34 *
35 * SysV/XPG4 hash table functions.
36 *
37 * Implementation done based on NetBSD manual page and Solaris manual page,
38 * plus my own personal experience about how they're supposed to work.
39 *
40 * I tried to look at Knuth (as cited by the Solaris manual page), but
41 * nobody had a copy in the office, so...
42 */
43
44#include <sys/cdefs.h>
45#if defined(LIBC_SCCS) && !defined(lint)
46__RCSID("$NetBSD: hcreate.c,v 1.7 2011/09/14 23:33:51 christos Exp $");
47#endif /* LIBC_SCCS and not lint */
48
49#if !defined(lint)
50__COPYRIGHT("@(#) Copyright (c) 2001\
51 Christopher G. Demetriou.  All rights reserved.");
52#endif /* not lint */
53
54#include "namespace.h"
55#include <assert.h>
56#include <errno.h>
57#include <inttypes.h>
58#include <search.h>
59#include <stdlib.h>
60#include <string.h>
61#include <sys/queue.h>
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 */
67struct internal_entry {
68	SLIST_ENTRY(internal_entry) link;
69	ENTRY ent;
70};
71SLIST_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 */
84extern u_int32_t (*__default_hash)(const void *, size_t);
85
86static struct hsearch_data htable;
87
88int
89hcreate(size_t nel)
90{
91	_DIAGASSERT(htable.table == NULL);
92
93	/* Make sure this isn't called when a table already exists. */
94	if (htable.table != NULL) {
95		errno = EINVAL;
96		return 0;
97	}
98	return hcreate_r(nel, &htable);
99}
100
101int
102hcreate_r(size_t nel, struct hsearch_data *head)
103{
104	struct internal_head *table;
105	size_t idx;
106	unsigned int p2;
107	void *p;
108
109	/* If nel is too small, make it min sized. */
110	if (nel < MIN_BUCKETS)
111		nel = MIN_BUCKETS;
112
113	/* If it's too large, cap it. */
114	if (nel > MAX_BUCKETS)
115		nel = MAX_BUCKETS;
116
117	/* If it's is not a power of two in size, round up. */
118	if ((nel & (nel - 1)) != 0) {
119		for (p2 = 0; nel != 0; p2++)
120			nel >>= 1;
121		_DIAGASSERT(p2 <= MAX_BUCKETS_LG2);
122		nel = 1 << p2;
123	}
124
125	/* Allocate the table. */
126	head->size = nel;
127	head->filled = 0;
128	p = malloc(nel * sizeof table[0]);
129	if (p == NULL) {
130		errno = ENOMEM;
131		return 0;
132	}
133	head->table = p;
134	table = p;
135
136	/* Initialize it. */
137	for (idx = 0; idx < nel; idx++)
138		SLIST_INIT(&table[idx]);
139
140	return 1;
141}
142
143void
144hdestroy(void)
145{
146	_DIAGASSERT(htable.table != NULL);
147	hdestroy_r(&htable);
148}
149
150void
151hdestroy_r(struct hsearch_data *head)
152{
153	struct internal_entry *ie;
154	size_t idx;
155	void *p;
156	struct internal_head *table;
157
158	if (head == NULL)
159		return;
160
161	p = head->table;
162	head->table = NULL;
163	table = p;
164
165	for (idx = 0; idx < head->size; idx++) {
166		while (!SLIST_EMPTY(&table[idx])) {
167			ie = SLIST_FIRST(&table[idx]);
168			SLIST_REMOVE_HEAD(&table[idx], link);
169			free(ie->ent.key);
170			free(ie);
171		}
172	}
173	free(table);
174}
175
176ENTRY *
177hsearch(ENTRY item, ACTION action)
178{
179	ENTRY *ep;
180	_DIAGASSERT(htable.table != NULL);
181	(void)hsearch_r(item, action, &ep, &htable);
182	return ep;
183}
184
185int
186hsearch_r(ENTRY item, ACTION action, ENTRY **itemp, struct hsearch_data *head)
187{
188	struct internal_head *table, *chain;
189	struct internal_entry *ie;
190	uint32_t hashval;
191	size_t len;
192	void *p;
193
194	_DIAGASSERT(item.key != NULL);
195	_DIAGASSERT(action == ENTER || action == FIND);
196
197	p = head->table;
198	table = p;
199
200	len = strlen(item.key);
201	hashval = (*__default_hash)(item.key, len);
202
203	chain = &table[hashval & (head->size - 1)];
204	ie = SLIST_FIRST(chain);
205	while (ie != NULL) {
206		if (strcmp(ie->ent.key, item.key) == 0)
207			break;
208		ie = SLIST_NEXT(ie, link);
209	}
210
211	if (ie != NULL) {
212		*itemp = &ie->ent;
213		return 1;
214	} else if (action == FIND) {
215		*itemp = NULL;
216		errno = ESRCH;
217		return 1;
218	}
219
220	ie = malloc(sizeof *ie);
221	if (ie == NULL)
222		return 0;
223	ie->ent.key = item.key;
224	ie->ent.data = item.data;
225
226	SLIST_INSERT_HEAD(chain, ie, link);
227	*itemp = &ie->ent;
228	head->filled++;
229	return 1;
230}
231