1 /* $OpenBSD: hcreate.c,v 1.1 2004/06/24 04:43:33 millert 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 #ifndef lint 51 static const char copyright[] = 52 "@(#) Copyright (c) 2001 Christopher G. Demetriou. All rights reserved.\n"; 53 #endif /* not lint */ 54 55 #ifndef lint 56 static const char rcsid[] = "$OpenBSD: hcreate.c,v 1.1 2004/06/24 04:43:33 millert Exp $"; 57 #endif /* not lint */ 58 59 #include "namespace.h" 60 #include <assert.h> 61 #include <errno.h> 62 #include <inttypes.h> 63 #include <search.h> 64 #include <stdlib.h> 65 #include <string.h> 66 #include <sys/queue.h> 67 68 #ifndef _DIAGASSERT 69 #define _DIAGASSERT 70 #endif 71 72 /* 73 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit 74 * ptr machine) without adjusting MAX_BUCKETS_LG2 below. 75 */ 76 struct internal_entry { 77 SLIST_ENTRY(internal_entry) link; 78 ENTRY ent; 79 }; 80 SLIST_HEAD(internal_head, internal_entry); 81 82 #define MIN_BUCKETS_LG2 4 83 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2) 84 85 /* 86 * max * sizeof internal_entry must fit into size_t. 87 * assumes internal_entry is <= 32 (2^5) bytes. 88 */ 89 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5) 90 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2) 91 92 /* Default hash function, from db/hash/hash_func.c */ 93 extern u_int32_t (*__default_hash)(const void *, size_t); 94 95 static struct internal_head *htable; 96 static size_t htablesize; 97 98 int 99 hcreate(size_t nel) 100 { 101 size_t idx; 102 unsigned int p2; 103 104 /* Make sure this isn't called when a table already exists. */ 105 _DIAGASSERT(htable == NULL); 106 if (htable != NULL) { 107 errno = EINVAL; 108 return 0; 109 } 110 111 /* If nel is too small, make it min sized. */ 112 if (nel < MIN_BUCKETS) 113 nel = MIN_BUCKETS; 114 115 /* If it's too large, cap it. */ 116 if (nel > MAX_BUCKETS) 117 nel = MAX_BUCKETS; 118 119 /* If it's is not a power of two in size, round up. */ 120 if ((nel & (nel - 1)) != 0) { 121 for (p2 = 0; nel != 0; p2++) 122 nel >>= 1; 123 _DIAGASSERT(p2 <= MAX_BUCKETS_LG2); 124 nel = 1 << p2; 125 } 126 127 /* Allocate the table. */ 128 htablesize = nel; 129 htable = malloc(htablesize * sizeof htable[0]); 130 if (htable == NULL) { 131 errno = ENOMEM; 132 return 0; 133 } 134 135 /* Initialize it. */ 136 for (idx = 0; idx < htablesize; idx++) 137 SLIST_INIT(&htable[idx]); 138 139 return 1; 140 } 141 142 void 143 hdestroy(void) 144 { 145 struct internal_entry *ie; 146 size_t idx; 147 148 _DIAGASSERT(htable != NULL); 149 if (htable == NULL) 150 return; 151 152 for (idx = 0; idx < htablesize; idx++) { 153 while (!SLIST_EMPTY(&htable[idx])) { 154 ie = SLIST_FIRST(&htable[idx]); 155 SLIST_REMOVE_HEAD(&htable[idx], link); 156 free(ie->ent.key); 157 free(ie); 158 } 159 } 160 free(htable); 161 htable = NULL; 162 } 163 164 ENTRY * 165 hsearch(ENTRY item, ACTION action) 166 { 167 struct internal_head *head; 168 struct internal_entry *ie; 169 uint32_t hashval; 170 size_t len; 171 172 _DIAGASSERT(htable != NULL); 173 _DIAGASSERT(item.key != NULL); 174 _DIAGASSERT(action == ENTER || action == FIND); 175 176 len = strlen(item.key); 177 hashval = (*__default_hash)(item.key, len); 178 179 head = &htable[hashval & (htablesize - 1)]; 180 ie = SLIST_FIRST(head); 181 while (ie != NULL) { 182 if (strcmp(ie->ent.key, item.key) == 0) 183 break; 184 ie = SLIST_NEXT(ie, link); 185 } 186 187 if (ie != NULL) 188 return &ie->ent; 189 else if (action == FIND) 190 return NULL; 191 192 ie = malloc(sizeof *ie); 193 if (ie == NULL) 194 return NULL; 195 ie->ent.key = item.key; 196 ie->ent.data = item.data; 197 198 SLIST_INSERT_HEAD(head, ie, link); 199 return &ie->ent; 200 } 201