libexec/revnetgroup/hash.c

   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  * $FreeBSD: src/libexec/revnetgroup/hash.c,v 1.6 1999/08/28 00:09:47 peter Exp $
  33  * $DragonFly: src/libexec/revnetgroup/hash.c,v 1.3 2008/11/19 17:46:55 swildner Exp $
  34  */
  35
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <string.h>
  39 #include <sys/types.h>
  40 #include "hash.h"
  41
  42 /*
  43  * This hash function is stolen directly from the
  44  * Berkeley DB package. It already exists inside libc, but
  45  * it's declared static which prevents us from calling it
  46  * from here.
  47  */
  48 /*
  49  * OZ's original sdbm hash
  50  */
  51 static u_int32_t
  52 hash(const void *keyarg, size_t len)
  53 {
  54         const u_char *key;
  55         size_t loop;
  56         u_int32_t h;
  57
  58 #define HASHC   h = *key++ + 65599 * h
  59
  60         h = 0;
  61         key = keyarg;
  62         if (len > 0) {
  63                 loop = (len + 8 - 1) >> 3;
  64
  65                 switch (len & (8 - 1)) {
  66                 case 0:
  67                         do {
  68                                 HASHC;
  69                                 /* FALLTHROUGH */
  70                 case 7:
  71                                 HASHC;
  72                                 /* FALLTHROUGH */
  73                 case 6:
  74                                 HASHC;
  75                                 /* FALLTHROUGH */
  76                 case 5:
  77                                 HASHC;
  78                                 /* FALLTHROUGH */
  79                 case 4:
  80                                 HASHC;
  81                                 /* FALLTHROUGH */
  82                 case 3:
  83                                 HASHC;
  84                                 /* FALLTHROUGH */
  85                 case 2:
  86                                 HASHC;
  87                                 /* FALLTHROUGH */
  88                 case 1:
  89                                 HASHC;
  90                         } while (--loop);
  91                 }
  92         }
  93         return (h);
  94 }
  95
  96 /*
  97  * Generate a hash value for a given key (character string).
  98  * We mask off all but the lower 8 bits since our table array
  99  * can only hold 256 elements.
 100  */
 101 static u_int32_t
 102 hashkey(char *key)
 103 {
 104
 105         if (key == NULL)
 106                 return (-1);
 107         return(hash((void *)key, strlen(key)) & HASH_MASK);
 108 }
 109
 110 /* Find an entry in the hash table (may be hanging off a linked list). */
 111 char *
 112 lookup(struct group_entry *table[], char *key)
 113 {
 114         struct group_entry *cur;
 115
 116         cur = table[hashkey(key)];
 117
 118         while (cur) {
 119                 if (!strcmp(cur->key, key))
 120                         return(cur->data);
 121                 cur = cur->next;
 122         }
 123
 124         return(NULL);
 125 }
 126
 127 /*
 128  * Store an entry in the main netgroup hash table. Here's how this
 129  * works: the table can only be so big when we initialize it (TABLESIZE)
 130  * but the number of netgroups in the /etc/netgroup file could easily be
 131  * much larger than the table. Since our hash values are adjusted to
 132  * never be greater than TABLESIZE too, this means it won't be long before
 133  * we find ourselves with two keys that hash to the same value.
 134  *
 135  * One way to deal with this is to malloc(2) a second table and start
 136  * doing indirection, but this is a pain in the butt and it's not worth
 137  * going to all that trouble for a dinky little program like this. Instead,
 138  * we turn each table entry into a linked list and simply link keys
 139  * with the same hash value together at the same index location within
 140  * the table.
 141  *
 142  * That's a lot of comment for such a small piece of code, isn't it.
 143  */
 144 void
 145 store(struct group_entry *table[], char *key, char *data)
 146 {
 147         struct group_entry *new;
 148         u_int32_t i;
 149
 150         i = hashkey(key);
 151
 152         new = (struct group_entry *)malloc(sizeof(struct group_entry));
 153         new->key = strdup(key);
 154         new->data = strdup(data);
 155         new->next = table[i];
 156         table[i] = new;
 157
 158         return;
 159 }
 160
 161 /*
 162  * Store a group member entry and/or update its grouplist. This is
 163  * a bit more complicated than the previous function since we have to
 164  * maintain not only the hash table of group members, each group member
 165  * structure also has a linked list of groups hung off it. If handed
 166  * a member name that we haven't encountered before, we have to do
 167  * two things: add that member to the table (possibly hanging them
 168  * off the end of a linked list, as above), and add a group name to
 169  * the member's grouplist list. If we're handed a name that already has
 170  * an entry in the table, then we just have to do one thing, which is
 171  * to update its grouplist.
 172  */
 173 void
 174 mstore(struct member_entry *table[], char *key, char *data, char *domain)
 175 {
 176         struct member_entry *cur, *new;
 177         struct grouplist *tmp;
 178         u_int32_t i;
 179
 180         i = hashkey(key);
 181         cur = table[i];
 182
 183         tmp = (struct grouplist *)malloc(sizeof(struct grouplist));
 184         tmp->groupname = strdup(data);
 185         tmp->next = NULL;
 186
 187         /* Check if all we have to do is insert a new groupname. */
 188         while (cur) {
 189                 if (!strcmp(cur->key, key)) {
 190                         tmp->next = cur->groups;
 191                         cur->groups = tmp;
 192                         return;
 193                 }
 194                 cur = cur->next;
 195         }
 196
 197         /* Didn't find a match -- add the whole mess to the table. */
 198         new = (struct member_entry *)malloc(sizeof(struct member_entry));
 199         new->key = strdup(key);
 200         new->domain = domain ? strdup(domain) : "*";
 201         new->groups = tmp;
 202         new->next = table[i];
 203         table[i] = new;
 204
 205         return;
 206 }