1 /* $OpenBSD: hash.c,v 1.3 2004/09/16 18:35:43 deraadt Exp $ */ 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 #include "dhcpd.h" 44 45 static int do_hash(unsigned char *, int, int); 46 47 struct hash_table * 48 new_hash(void) 49 { 50 struct hash_table *rv = new_hash_table(DEFAULT_HASH_SIZE, "new_hash"); 51 if (!rv) 52 return (rv); 53 memset(&rv->buckets[0], 0, 54 DEFAULT_HASH_SIZE * sizeof(struct hash_bucket *)); 55 return (rv); 56 } 57 58 static int 59 do_hash(unsigned char *name, int len, int size) 60 { 61 int accum = 0; 62 unsigned char *s = name; 63 int i = len; 64 65 while (i--) { 66 /* Add the character in... */ 67 accum += *s++; 68 /* Add carry back in... */ 69 while (accum > 255) 70 accum = (accum & 255) + (accum >> 8); 71 } 72 return (accum % size); 73 } 74 75 void add_hash(struct hash_table *table, unsigned char *name, int len, 76 unsigned char *pointer) 77 { 78 int hashno; 79 struct hash_bucket *bp; 80 81 if (!table) 82 return; 83 if (!len) 84 len = strlen((char *)name); 85 86 hashno = do_hash(name, len, table->hash_count); 87 bp = new_hash_bucket("add_hash"); 88 89 if (!bp) { 90 warning("Can't add %s to hash table.", name); 91 return; 92 } 93 bp->name = name; 94 bp->value = pointer; 95 bp->next = table->buckets[hashno]; 96 bp->len = len; 97 table->buckets[hashno] = bp; 98 } 99 100 void 101 delete_hash_entry(struct hash_table *table, unsigned char *name, int len) 102 { 103 int hashno; 104 struct hash_bucket *bp, *pbp = NULL; 105 106 if (!table) 107 return; 108 if (!len) 109 len = strlen((char *)name); 110 111 hashno = do_hash(name, len, table->hash_count); 112 113 /* 114 * Go through the list looking for an entry that matches; if we 115 * find it, delete it. 116 */ 117 for (bp = table->buckets[hashno]; bp; bp = bp->next) { 118 if ((!bp->len && 119 !strcmp((char *)bp->name, (char *)name)) || 120 (bp->len == len && !memcmp(bp->name, name, len))) { 121 if (pbp) 122 pbp->next = bp->next; 123 else 124 table->buckets[hashno] = bp->next; 125 free_hash_bucket(bp, "delete_hash_entry"); 126 break; 127 } 128 pbp = bp; /* jwg, 9/6/96 - nice catch! */ 129 } 130 } 131 132 unsigned char * 133 hash_lookup(struct hash_table *table, unsigned char *name, int len) 134 { 135 int hashno; 136 struct hash_bucket *bp; 137 138 if (!table) 139 return (NULL); 140 141 if (!len) 142 len = strlen((char *)name); 143 144 hashno = do_hash(name, len, table->hash_count); 145 146 for (bp = table->buckets[hashno]; bp; bp = bp->next) 147 if (len == bp->len && !memcmp(bp->name, name, len)) 148 return (bp->value); 149 150 return (NULL); 151 } 152