hash.c revision 31404 
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
33#ifndef lint
34static const char rcsid[] =
35	"$Id$";
36#endif /* not lint */
37
38#include <stdio.h>
39#include <stdlib.h>
40#include <string.h>
41#include <sys/types.h>
42#include "hash.h"
43
44/*
45 * This hash function is stolen directly from the
46 * Berkeley DB package. It already exists inside libc, but
47 * it's declared static which prevents us from calling it
48 * from here.
49 */
50/*
51 * OZ's original sdbm hash
52 */
53u_int32_t
54hash(keyarg, len)
55	const void *keyarg;
56	register size_t len;
57{
58	register const u_char *key;
59	register size_t loop;
60	register u_int32_t h;
61
62#define HASHC   h = *key++ + 65599 * h
63
64	h = 0;
65	key = keyarg;
66	if (len > 0) {
67		loop = (len + 8 - 1) >> 3;
68
69		switch (len & (8 - 1)) {
70		case 0:
71			do {
72				HASHC;
73				/* FALLTHROUGH */
74		case 7:
75				HASHC;
76				/* FALLTHROUGH */
77		case 6:
78				HASHC;
79				/* FALLTHROUGH */
80		case 5:
81				HASHC;
82				/* FALLTHROUGH */
83		case 4:
84				HASHC;
85				/* FALLTHROUGH */
86		case 3:
87				HASHC;
88				/* FALLTHROUGH */
89		case 2:
90				HASHC;
91				/* FALLTHROUGH */
92		case 1:
93				HASHC;
94			} while (--loop);
95		}
96	}
97	return (h);
98}
99
100/*
101 * Generate a hash value for a given key (character string).
102 * We mask off all but the lower 8 bits since our table array
103 * can only hold 256 elements.
104 */
105u_int32_t hashkey(key)
106	char *key;
107{
108
109	if (key == NULL)
110		return (-1);
111	return(hash((void *)key, strlen(key)) & HASH_MASK);
112}
113
114/* Find an entry in the hash table (may be hanging off a linked list). */
115char *lookup(table, key)
116	struct group_entry *table[];
117	char *key;
118{
119	struct group_entry *cur;
120
121	cur = table[hashkey(key)];
122
123	while (cur) {
124		if (!strcmp(cur->key, key))
125			return(cur->data);
126		cur = cur->next;
127	}
128
129	return(NULL);
130}
131
132/*
133 * Store an entry in the main netgroup hash table. Here's how this
134 * works: the table can only be so big when we initialize it (TABLESIZE)
135 * but the number of netgroups in the /etc/netgroup file could easily be
136 * much larger than the table. Since our hash values are adjusted to
137 * never be greater than TABLESIZE too, this means it won't be long before
138 * we find ourselves with two keys that hash to the same value.
139 *
140 * One way to deal with this is to malloc(2) a second table and start
141 * doing indirection, but this is a pain in the butt and it's not worth
142 * going to all that trouble for a dinky little program like this. Instead,
143 * we turn each table entry into a linked list and simply link keys
144 * with the same hash value together at the same index location within
145 * the table.
146 *
147 * That's a lot of comment for such a small piece of code, isn't it.
148 */
149void store (table, key, data)
150	struct group_entry *table[];
151	char *key, *data;
152{
153	struct group_entry *new;
154	u_int32_t i;
155
156	i = hashkey(key);
157
158	new = (struct group_entry *)malloc(sizeof(struct group_entry));
159	new->key = strdup(key);
160	new->data = strdup(data);
161	new->next = table[i];
162	table[i] = new;
163
164	return;
165}
166
167/*
168 * Store a group member entry and/or update its grouplist. This is
169 * a bit more complicated than the previous function since we have to
170 * maintain not only the hash table of group members, each group member
171 * structure also has a linked list of groups hung off it. If handed
172 * a member name that we haven't encountered before, we have to do
173 * two things: add that member to the table (possibly hanging them
174 * off the end of a linked list, as above), and add a group name to
175 * the member's grouplist list. If we're handed a name that already has
176 * an entry in the table, then we just have to do one thing, which is
177 * to update its grouplist.
178 */
179void mstore (table, key, data, domain)
180	struct member_entry *table[];
181	char *key, *data, *domain;
182{
183	struct member_entry *cur, *new;
184	struct grouplist *tmp;
185	u_int32_t i;
186
187	i = hashkey(key);
188	cur = table[i];
189
190	tmp = (struct grouplist *)malloc(sizeof(struct grouplist));
191	tmp->groupname = strdup(data);
192	tmp->next = NULL;
193
194	/* Check if all we have to do is insert a new groupname. */
195	while (cur) {
196		if (!strcmp(cur->key, key)) {
197			tmp->next = cur->groups;
198			cur->groups = tmp;
199			return;
200		}
201		cur = cur->next;
202	}
203
204	/* Didn't find a match -- add the whole mess to the table. */
205	new = (struct member_entry *)malloc(sizeof(struct member_entry));
206	new->key = strdup(key);
207	new->domain = domain ? strdup(domain) : "*";
208	new->groups = tmp;
209	new->next = table[i];
210	table[i] = new;
211
212	return;
213}
214