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 1.2 2003/06/17 04:27:07 dillon 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 u_int32_t
  52 hash(keyarg, len)
  53         const void *keyarg;
  54         register size_t len;
  55 {
  56         register const u_char *key;
  57         register size_t loop;
  58         register u_int32_t h;
  59
  60 #define HASHC   h = *key++ + 65599 * h
  61
  62         h = 0;
  63         key = keyarg;
  64         if (len > 0) {
  65                 loop = (len + 8 - 1) >> 3;
  66
  67                 switch (len & (8 - 1)) {
  68                 case 0:
  69                         do {
  70                                 HASHC;
  71                                 /* FALLTHROUGH */
  72                 case 7:
  73                                 HASHC;
  74                                 /* FALLTHROUGH */
  75                 case 6:
  76                                 HASHC;
  77                                 /* FALLTHROUGH */
  78                 case 5:
  79                                 HASHC;
  80                                 /* FALLTHROUGH */
  81                 case 4:
  82                                 HASHC;
  83                                 /* FALLTHROUGH */
  84                 case 3:
  85                                 HASHC;
  86                                 /* FALLTHROUGH */
  87                 case 2:
  88                                 HASHC;
  89                                 /* FALLTHROUGH */
  90                 case 1:
  91                                 HASHC;
  92                         } while (--loop);
  93                 }
  94         }
  95         return (h);
  96 }
  97
  98 /*
  99  * Generate a hash value for a given key (character string).
 100  * We mask off all but the lower 8 bits since our table array
 101  * can only hold 256 elements.
 102  */
 103 u_int32_t hashkey(key)
 104         char *key;
 105 {
 106
 107         if (key == NULL)
 108                 return (-1);
 109         return(hash((void *)key, strlen(key)) & HASH_MASK);
 110 }
 111
 112 /* Find an entry in the hash table (may be hanging off a linked list). */
 113 char *lookup(table, key)
 114         struct group_entry *table[];
 115         char *key;
 116 {
 117         struct group_entry *cur;
 118
 119         cur = table[hashkey(key)];
 120
 121         while (cur) {
 122                 if (!strcmp(cur->key, key))
 123                         return(cur->data);
 124                 cur = cur->next;
 125         }
 126
 127         return(NULL);
 128 }
 129
 130 /*
 131  * Store an entry in the main netgroup hash table. Here's how this
 132  * works: the table can only be so big when we initialize it (TABLESIZE)
 133  * but the number of netgroups in the /etc/netgroup file could easily be
 134  * much larger than the table. Since our hash values are adjusted to
 135  * never be greater than TABLESIZE too, this means it won't be long before
 136  * we find ourselves with two keys that hash to the same value.
 137  *
 138  * One way to deal with this is to malloc(2) a second table and start
 139  * doing indirection, but this is a pain in the butt and it's not worth
 140  * going to all that trouble for a dinky little program like this. Instead,
 141  * we turn each table entry into a linked list and simply link keys
 142  * with the same hash value together at the same index location within
 143  * the table.
 144  *
 145  * That's a lot of comment for such a small piece of code, isn't it.
 146  */
 147 void store (table, key, data)
 148         struct group_entry *table[];
 149         char *key, *data;
 150 {
 151         struct group_entry *new;
 152         u_int32_t i;
 153
 154         i = hashkey(key);
 155
 156         new = (struct group_entry *)malloc(sizeof(struct group_entry));
 157         new->key = strdup(key);
 158         new->data = strdup(data);
 159         new->next = table[i];
 160         table[i] = new;
 161
 162         return;
 163 }
 164
 165 /*
 166  * Store a group member entry and/or update its grouplist. This is
 167  * a bit more complicated than the previous function since we have to
 168  * maintain not only the hash table of group members, each group member
 169  * structure also has a linked list of groups hung off it. If handed
 170  * a member name that we haven't encountered before, we have to do
 171  * two things: add that member to the table (possibly hanging them
 172  * off the end of a linked list, as above), and add a group name to
 173  * the member's grouplist list. If we're handed a name that already has
 174  * an entry in the table, then we just have to do one thing, which is
 175  * to update its grouplist.
 176  */
 177 void mstore (table, key, data, domain)
 178         struct member_entry *table[];
 179         char *key, *data, *domain;
 180 {
 181         struct member_entry *cur, *new;
 182         struct grouplist *tmp;
 183         u_int32_t i;
 184
 185         i = hashkey(key);
 186         cur = table[i];
 187
 188         tmp = (struct grouplist *)malloc(sizeof(struct grouplist));
 189         tmp->groupname = strdup(data);
 190         tmp->next = NULL;
 191
 192         /* Check if all we have to do is insert a new groupname. */
 193         while (cur) {
 194                 if (!strcmp(cur->key, key)) {
 195                         tmp->next = cur->groups;
 196                         cur->groups = tmp;
 197                         return;
 198                 }
 199                 cur = cur->next;
 200         }
 201
 202         /* Didn't find a match -- add the whole mess to the table. */
 203         new = (struct member_entry *)malloc(sizeof(struct member_entry));
 204         new->key = strdup(key);
 205         new->domain = domain ? strdup(domain) : "*";
 206         new->groups = tmp;
 207         new->next = table[i];
 208         table[i] = new;
 209
 210         return;
 211 }