hash.c revision 11815 
1/*
2 * Copyright (c) 1995
3 *	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by Bill Paul.
16 * 4. Neither the name of the author nor the names of any co-contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY Bill Paul AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL Bill Paul OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 *	$Id$
33 */
34
35#include <stdio.h>
36#include <stdlib.h>
37#include <string.h>
38#include <sys/types.h>
39#include "hash.h"
40
41/*
42 * This hash function is stolen directly from the
43 * Berkeley DB package. It already exists inside libc, but
44 * it's declared static which prevents us from calling it
45 * from here.
46 */
47/*
48 * OZ's original sdbm hash
49 */
50u_int32_t
51hash(keyarg, len)
52	const void *keyarg;
53	register size_t len;
54{
55	register const u_char *key;
56	register size_t loop;
57	register u_int32_t h;
58
59#define HASHC   h = *key++ + 65599 * h
60
61	h = 0;
62	key = keyarg;
63	if (len > 0) {
64		loop = (len + 8 - 1) >> 3;
65
66		switch (len & (8 - 1)) {
67		case 0:
68			do {
69				HASHC;
70				/* FALLTHROUGH */
71		case 7:
72				HASHC;
73				/* FALLTHROUGH */
74		case 6:
75				HASHC;
76				/* FALLTHROUGH */
77		case 5:
78				HASHC;
79				/* FALLTHROUGH */
80		case 4:
81				HASHC;
82				/* FALLTHROUGH */
83		case 3:
84				HASHC;
85				/* FALLTHROUGH */
86		case 2:
87				HASHC;
88				/* FALLTHROUGH */
89		case 1:
90				HASHC;
91			} while (--loop);
92		}
93	}
94	return (h);
95}
96
97/*
98 * Generate a hash value for a given key (character string).
99 * We mask off all but the lower 8 bits since our table array
100 * can only hole 256 elements.
101 */
102u_int32_t hashkey(key)
103	char *key;
104{
105
106	if (key == NULL)
107		return (-1);
108	return(hash((void *)key, strlen(key)) & HASH_MASK);
109}
110
111/* Find an entry in the hash table (may be hanging off a linked list). */
112char *lookup(table, key)
113	struct group_entry *table[];
114	char *key;
115{
116	struct group_entry *cur;
117
118	cur = table[hashkey(key)];
119
120	while (cur) {
121		if (!strcmp(cur->key, key))
122			return(cur->data);
123		cur = cur->next;
124	}
125
126	return(NULL);
127}
128
129/*
130 * Store an entry in the main netgroup hash table. Here's how this
131 * works: the table can only be so big when we initialize it (TABLESIZE)
132 * but the number of netgroups in the /etc/netgroup file could easily be
133 * much larger than the table. Since our hash values are adjusted to
134 * never be greater than TABLESIZE too, this means it won't be long before
135 * we find ourselves with two keys that hash to the same value.
136 *
137 * One way to deal with this is to malloc(2) a second table and start
138 * doing indirection, but this is a pain in the butt and it's not worth
139 * going to all that trouble for a dinky littke program like this. Instead,
140 * we turn each table entry into a linked list and simply link keys
141 * with the same hash value together at the same index location within
142 * the table.
143 *
144 * That's a lot of comment for such a small piece of code, isn't it.
145 */
146void store (table, key, data)
147	struct group_entry *table[];
148	char *key, *data;
149{
150	struct group_entry *new;
151	u_int32_t i;
152
153	i = hashkey(key);
154
155	new = (struct group_entry *)malloc(sizeof(struct group_entry));
156	new->key = strdup(key);
157	new->data = strdup(data);
158	new->next = table[i];
159	table[i] = new;
160
161	return;
162}
163
164/*
165 * Store an group member entry and/or update its grouplist. This is
166 * a bit more complicated than the previous function since we have to
167 * maintain not only the hash table of group members, each group member
168 * structure also has a linked list of groups hung off it. If handed
169 * a member name that we haven't encountered before, we have to do
170 * two things: add that member to the table (possibly hanging them
171 * off the end of a linked list, as above), and add a group name to
172 * the member's grouplist list. If we're handed a name that already has
173 * an entry in the table, then we just have to do one thing, which is
174 * to update its grouplist.
175 */
176void mstore (table, key, data, domain)
177	struct member_entry *table[];
178	char *key, *data, *domain;
179{
180	struct member_entry *cur, *new;
181	struct grouplist *tmp;
182	u_int32_t i;
183
184	i = hashkey(key);
185	cur = table[i];
186
187	tmp = (struct grouplist *)malloc(sizeof(struct grouplist));
188	tmp->groupname = strdup(data);
189	tmp->next = NULL;
190
191	/* Check if all we have to do is insert a new groupname. */
192	while (cur) {
193		if (!strcmp(cur->key, key)) {
194			tmp->next = cur->groups;
195			cur->groups = tmp;
196			return;
197		}
198		cur = cur->next;
199	}
200
201	/* Didn't find a match -- add the whole mess to the table. */
202	new = (struct member_entry *)malloc(sizeof(struct member_entry));
203	new->key = strdup(key);
204	new->domain = domain ? strdup(domain) : "*";
205	new->groups = tmp;
206	new->next = table[i];
207	table[i] = new;
208
209	return;
210}
211