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