1 /* $OpenBSD: hash.c,v 1.6 2010/01/01 20:30:25 krw 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; 51 52 rv = calloc(1, sizeof(struct hash_table)); 53 if (!rv) 54 warning("No memory for new hash."); 55 else 56 rv->hash_count = DEFAULT_HASH_SIZE; 57 58 return (rv); 59 } 60 61 static int 62 do_hash(unsigned char *name, int len, int size) 63 { 64 int accum = 0; 65 unsigned char *s = name; 66 int i = len; 67 68 while (i--) { 69 /* Add the character in... */ 70 accum += *s++; 71 /* Add carry back in... */ 72 while (accum > 255) 73 accum = (accum & 255) + (accum >> 8); 74 } 75 return (accum % size); 76 } 77 78 void add_hash(struct hash_table *table, unsigned char *name, int len, 79 unsigned char *pointer) 80 { 81 int hashno; 82 struct hash_bucket *bp; 83 84 if (!table) 85 return; 86 if (!len) 87 len = strlen((char *)name); 88 89 hashno = do_hash(name, len, table->hash_count); 90 bp = calloc(1, sizeof(struct hash_bucket)); 91 if (!bp) { 92 warning("Can't add %s to hash table.", name); 93 return; 94 } 95 bp->name = name; 96 bp->value = pointer; 97 bp->next = table->buckets[hashno]; 98 bp->len = len; 99 table->buckets[hashno] = bp; 100 } 101 102 void 103 delete_hash_entry(struct hash_table *table, unsigned char *name, int len) 104 { 105 int hashno; 106 struct hash_bucket *bp, *pbp = NULL; 107 108 if (!table) 109 return; 110 if (!len) 111 len = strlen((char *)name); 112 113 hashno = do_hash(name, len, table->hash_count); 114 115 /* 116 * Go through the list looking for an entry that matches; if we 117 * find it, delete it. 118 */ 119 for (bp = table->buckets[hashno]; bp; bp = bp->next) { 120 if ((!bp->len && 121 !strcmp((char *)bp->name, (char *)name)) || 122 (bp->len == len && !memcmp(bp->name, name, len))) { 123 if (pbp) 124 pbp->next = bp->next; 125 else 126 table->buckets[hashno] = bp->next; 127 free(bp); 128 break; 129 } 130 pbp = bp; /* jwg, 9/6/96 - nice catch! */ 131 } 132 } 133 134 unsigned char * 135 hash_lookup(struct hash_table *table, unsigned char *name, int len) 136 { 137 int hashno; 138 struct hash_bucket *bp; 139 140 if (!table) 141 return (NULL); 142 143 if (!len) 144 len = strlen((char *)name); 145 146 hashno = do_hash(name, len, table->hash_count); 147 148 for (bp = table->buckets[hashno]; bp; bp = bp->next) 149 if (len == bp->len && !memcmp(bp->name, name, len)) 150 return (bp->value); 151 152 return (NULL); 153 } 154