hash.c revision 330897 
1/*	$OpenBSD: hash.c,v 1.9 2004/05/10 15:30:47 deraadt Exp $	*/
2
3/* Routines for manipulating hash tables... */
4
5/*-
6 * SPDX-License-Identifier: BSD-3-Clause
7 *
8 * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.
9 * All rights reserved.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 *
15 * 1. Redistributions of source code must retain the above copyright
16 *    notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of The Internet Software Consortium nor the names
21 *    of its contributors may be used to endorse or promote products derived
22 *    from this software without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
25 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
26 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
27 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
28 * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
29 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
32 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
33 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
34 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
35 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * This software has been written for the Internet Software Consortium
39 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
40 * Enterprises.  To learn more about the Internet Software Consortium,
41 * see ``http://www.vix.com/isc''.  To learn more about Vixie
42 * Enterprises, see ``http://www.vix.com''.
43 */
44
45#include <sys/cdefs.h>
46__FBSDID("$FreeBSD: stable/11/sbin/dhclient/hash.c 330897 2018-03-14 03:19:51Z eadler $");
47
48#include "dhcpd.h"
49
50static int do_hash(unsigned char *, int, int);
51
52struct hash_table *
53new_hash(void)
54{
55	struct hash_table *rv = new_hash_table(DEFAULT_HASH_SIZE);
56
57	if (!rv)
58		return (rv);
59	memset(&rv->buckets[0], 0,
60	    DEFAULT_HASH_SIZE * sizeof(struct hash_bucket *));
61	return (rv);
62}
63
64static int
65do_hash(unsigned char *name, int len, int size)
66{
67	unsigned char *s = name;
68	int accum = 0, i = len;
69
70	while (i--) {
71		/* Add the character in... */
72		accum += *s++;
73		/* Add carry back in... */
74		while (accum > 255)
75			accum = (accum & 255) + (accum >> 8);
76	}
77	return (accum % size);
78}
79
80void add_hash(struct hash_table *table, unsigned char *name, int len,
81    unsigned char *pointer)
82{
83	struct hash_bucket *bp;
84	int hashno;
85
86	if (!table)
87		return;
88	if (!len)
89		len = strlen((char *)name);
90
91	hashno = do_hash(name, len, table->hash_count);
92	bp = new_hash_bucket();
93
94	if (!bp) {
95		warning("Can't add %s to hash table.", name);
96		return;
97	}
98	bp->name = name;
99	bp->value = pointer;
100	bp->next = table->buckets[hashno];
101	bp->len = len;
102	table->buckets[hashno] = bp;
103}
104
105unsigned char *
106hash_lookup(struct hash_table *table, unsigned char *name, int len)
107{
108	struct hash_bucket *bp;
109	int hashno;
110
111	if (!table)
112		return (NULL);
113
114	if (!len)
115		len = strlen((char *)name);
116
117	hashno = do_hash(name, len, table->hash_count);
118
119	for (bp = table->buckets[hashno]; bp; bp = bp->next)
120		if (len == bp->len && !memcmp(bp->name, name, len))
121			return (bp->value);
122
123	return (NULL);
124}
125