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