1 /* $OpenBSD: hcreate.c,v 1.4 2007/09/02 15:19:17 deraadt Exp $ */ 2 /* $NetBSD: hcreate.c,v 1.5 2004/04/23 02:48:12 simonb Exp $ */ 3 4 /* 5 * Copyright (c) 2001 Christopher G. Demetriou 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed for the 19 * NetBSD Project. See http://www.NetBSD.org/ for 20 * information about NetBSD. 21 * 4. The name of the author may not be used to endorse or promote products 22 * derived from this software without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 25 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 26 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 27 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 28 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 29 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 30 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 31 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 32 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 33 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 34 * 35 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>> 36 */ 37 38 /* 39 * hcreate() / hsearch() / hdestroy() 40 * 41 * SysV/XPG4 hash table functions. 42 * 43 * Implementation done based on NetBSD manual page and Solaris manual page, 44 * plus my own personal experience about how they're supposed to work. 45 * 46 * I tried to look at Knuth (as cited by the Solaris manual page), but 47 * nobody had a copy in the office, so... 48 */ 49 50 #include "namespace.h" 51 #include <assert.h> 52 #include <errno.h> 53 #include <inttypes.h> 54 #include <search.h> 55 #include <stdlib.h> 56 #include <string.h> 57 #include <sys/queue.h> 58 59 #ifndef _DIAGASSERT 60 #define _DIAGASSERT(x) 61 #endif 62 63 /* 64 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit 65 * ptr machine) without adjusting MAX_BUCKETS_LG2 below. 66 */ 67 struct internal_entry { 68 SLIST_ENTRY(internal_entry) link; 69 ENTRY ent; 70 }; 71 SLIST_HEAD(internal_head, internal_entry); 72 73 #define MIN_BUCKETS_LG2 4 74 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2) 75 76 /* 77 * max * sizeof internal_entry must fit into size_t. 78 * assumes internal_entry is <= 32 (2^5) bytes. 79 */ 80 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5) 81 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2) 82 83 /* Default hash function, from db/hash/hash_func.c */ 84 extern u_int32_t (*__default_hash)(const void *, size_t); 85 86 static struct internal_head *htable; 87 static size_t htablesize; 88 89 int 90 hcreate(size_t nel) 91 { 92 size_t idx; 93 unsigned int p2; 94 95 /* Make sure this isn't called when a table already exists. */ 96 _DIAGASSERT(htable == NULL); 97 if (htable != NULL) { 98 errno = EINVAL; 99 return 0; 100 } 101 102 /* If nel is too small, make it min sized. */ 103 if (nel < MIN_BUCKETS) 104 nel = MIN_BUCKETS; 105 106 /* If it's too large, cap it. */ 107 if (nel > MAX_BUCKETS) 108 nel = MAX_BUCKETS; 109 110 /* If it's is not a power of two in size, round up. */ 111 if ((nel & (nel - 1)) != 0) { 112 for (p2 = 0; nel != 0; p2++) 113 nel >>= 1; 114 _DIAGASSERT(p2 <= MAX_BUCKETS_LG2); 115 nel = 1 << p2; 116 } 117 118 /* Allocate the table. */ 119 htablesize = nel; 120 htable = calloc(htablesize, sizeof htable[0]); 121 if (htable == NULL) { 122 errno = ENOMEM; 123 return 0; 124 } 125 126 /* Initialize it. */ 127 for (idx = 0; idx < htablesize; idx++) 128 SLIST_INIT(&htable[idx]); 129 130 return 1; 131 } 132 133 void 134 hdestroy(void) 135 { 136 struct internal_entry *ie; 137 size_t idx; 138 139 _DIAGASSERT(htable != NULL); 140 if (htable == NULL) 141 return; 142 143 for (idx = 0; idx < htablesize; idx++) { 144 while (!SLIST_EMPTY(&htable[idx])) { 145 ie = SLIST_FIRST(&htable[idx]); 146 SLIST_REMOVE_HEAD(&htable[idx], link); 147 free(ie->ent.key); 148 free(ie); 149 } 150 } 151 free(htable); 152 htable = NULL; 153 } 154 155 ENTRY * 156 hsearch(ENTRY item, ACTION action) 157 { 158 struct internal_head *head; 159 struct internal_entry *ie; 160 uint32_t hashval; 161 size_t len; 162 163 _DIAGASSERT(htable != NULL); 164 _DIAGASSERT(item.key != NULL); 165 _DIAGASSERT(action == ENTER || action == FIND); 166 167 len = strlen(item.key); 168 hashval = (*__default_hash)(item.key, len); 169 170 head = &htable[hashval & (htablesize - 1)]; 171 ie = SLIST_FIRST(head); 172 while (ie != NULL) { 173 if (strcmp(ie->ent.key, item.key) == 0) 174 break; 175 ie = SLIST_NEXT(ie, link); 176 } 177 178 if (ie != NULL) 179 return &ie->ent; 180 else if (action == FIND) 181 return NULL; 182 183 ie = malloc(sizeof *ie); 184 if (ie == NULL) 185 return NULL; 186 ie->ent.key = item.key; 187 ie->ent.data = item.data; 188 189 SLIST_INSERT_HEAD(head, ie, link); 190 return &ie->ent; 191 } 192