reactos/base/services/dhcp/hash.c

   1 /* hash.c
   2
   3    Routines for manipulating hash tables... */
   4
   5 /*
   6  * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of The Internet Software Consortium nor the names
  19  *    of its contributors may be used to endorse or promote products derived
  20  *    from this software without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
  23  * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
  24  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  25  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  26  * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
  27  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  28  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  29  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  30  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  31  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  32  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  33  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * This software has been written for the Internet Software Consortium
  37  * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
  38  * Enterprises.  To learn more about the Internet Software Consortium,
  39  * see ``http://www.vix.com/isc''.  To learn more about Vixie
  40  * Enterprises, see ``http://www.vix.com''.
  41  */
  42
  43 #define lint
  44 #ifndef lint
  45 static char copyright[] =
  46 "$Id: hash.c,v 1.9.2.3 1999/04/09 17:39:41 mellon Exp $ Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.  All rights reserved.\n";
  47 #endif /* not lint */
  48
  49 #include "rosdhcp.h"
  50
  51 static __inline int do_hash PROTO ((unsigned char *, int, int));
  52
  53 struct hash_table *new_hash ()
  54 {
  55         struct hash_table *rv = new_hash_table (DEFAULT_HASH_SIZE);
  56         if (!rv)
  57                 return rv;
  58         memset (&rv -> buckets [0], 0,
  59                 DEFAULT_HASH_SIZE * sizeof (struct hash_bucket *));
  60         return rv;
  61 }
  62
  63 static __inline int do_hash (name, len, size)
  64         unsigned char *name;
  65         int len;
  66         int size;
  67 {
  68         register int accum = 0;
  69         register unsigned char *s = name;
  70         int i = len;
  71         while (i--) {
  72                 /* Add the character in... */
  73                 accum += *s++;
  74                 /* Add carry back in... */
  75                 while (accum > 255) {
  76                         accum = (accum & 255) + (accum >> 8);
  77                 }
  78         }
  79         return accum % size;
  80 }
  81
  82 void add_hash (table, name, len, pointer)
  83         struct hash_table *table;
  84         int len;
  85         unsigned char *name;
  86         unsigned char *pointer;
  87 {
  88         int hashno;
  89         struct hash_bucket *bp;
  90
  91         if (!table)
  92                 return;
  93         if (!len)
  94                 len = strlen ((char *)name);
  95
  96         hashno = do_hash (name, len, table -> hash_count);
  97         bp = new_hash_bucket ();
  98
  99         if (!bp) {
 100                 warn ("Can't add %s to hash table.", name);
 101                 return;
 102         }
 103         bp -> name = name;
 104         bp -> value = pointer;
 105         bp -> next = table -> buckets [hashno];
 106         bp -> len = len;
 107         table -> buckets [hashno] = bp;
 108 }
 109
 110 void delete_hash_entry (table, name, len)
 111         struct hash_table *table;
 112         int len;
 113         unsigned char *name;
 114 {
 115         int hashno;
 116         struct hash_bucket *bp, *pbp = (struct hash_bucket *)0;
 117
 118         if (!table)
 119                 return;
 120         if (!len)
 121                 len = strlen ((char *)name);
 122
 123         hashno = do_hash (name, len, table -> hash_count);
 124
 125         /* Go through the list looking for an entry that matches;
 126            if we find it, delete it. */
 127         for (bp = table -> buckets [hashno]; bp; bp = bp -> next) {
 128                 if ((!bp -> len &&
 129                      !strcmp ((char *)bp -> name, (char *)name)) ||
 130                     (bp -> len == len &&
 131                      !memcmp (bp -> name, name, len))) {
 132                         if (pbp) {
 133                                 pbp -> next = bp -> next;
 134                         } else {
 135                                 table -> buckets [hashno] = bp -> next;
 136                         }
 137                         free_hash_bucket (bp, "delete_hash_entry");
 138                         break;
 139                 }
 140                 pbp = bp;       /* jwg, 9/6/96 - nice catch! */
 141         }
 142 }
 143
 144 unsigned char *hash_lookup (table, name, len)
 145         struct hash_table *table;
 146         unsigned char *name;
 147         int len;
 148 {
 149         int hashno;
 150         struct hash_bucket *bp;
 151
 152         if (!table)
 153                 return (unsigned char *)0;
 154
 155         if (!len)
 156                 len = strlen ((char *)name);
 157
 158         hashno = do_hash (name, len, table -> hash_count);
 159
 160         for (bp = table -> buckets [hashno]; bp; bp = bp -> next) {
 161                 if (len == bp -> len && !memcmp (bp -> name, name, len))
 162                         return bp -> value;
 163         }
 164         return (unsigned char *)0;
 165 }