1 /* $NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $ */ 2 /* $FreeBSD: src/lib/libc/stdlib/hcreate.c,v 1.1.2.2 2001/10/02 11:22:56 ru 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 <sys/cdefs.h> 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 55 #include <sys/types.h> 56 #include <sys/queue.h> 57 #include <errno.h> 58 #include <search.h> 59 #include <stdlib.h> 60 #include <string.h> 61 62 /* 63 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit 64 * ptr machine) without adjusting MAX_BUCKETS_LG2 below. 65 */ 66 struct internal_entry { 67 SLIST_ENTRY(internal_entry) link; 68 ENTRY ent; 69 }; 70 SLIST_HEAD(internal_head, internal_entry); 71 72 #define MIN_BUCKETS_LG2 4 73 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2) 74 75 /* 76 * max * sizeof internal_entry must fit into size_t. 77 * assumes internal_entry is <= 32 (2^5) bytes. 78 */ 79 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5) 80 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2) 81 82 /* Default hash function, from db/hash/hash_func.c */ 83 extern u_int32_t (*__default_hash)(const void *, size_t); 84 85 static struct internal_head *htable; 86 static size_t htablesize; 87 88 int 89 hcreate(size_t nel) 90 { 91 size_t idx; 92 unsigned int p2; 93 94 /* Make sure this this isn't called when a table already exists. */ 95 if (htable != NULL) { 96 errno = EINVAL; 97 return 0; 98 } 99 100 /* If nel is too small, make it min sized. */ 101 if (nel < MIN_BUCKETS) 102 nel = MIN_BUCKETS; 103 104 /* If it's too large, cap it. */ 105 if (nel > MAX_BUCKETS) 106 nel = MAX_BUCKETS; 107 108 /* If it's is not a power of two in size, round up. */ 109 if ((nel & (nel - 1)) != 0) { 110 for (p2 = 0; nel != 0; p2++) 111 nel >>= 1; 112 nel = 1 << p2; 113 } 114 115 /* Allocate the table. */ 116 htablesize = nel; 117 htable = malloc(htablesize * sizeof htable[0]); 118 if (htable == NULL) { 119 errno = ENOMEM; 120 return 0; 121 } 122 123 /* Initialize it. */ 124 for (idx = 0; idx < htablesize; idx++) 125 SLIST_INIT(&htable[idx]); 126 127 return 1; 128 } 129 130 void 131 hdestroy(void) 132 { 133 struct internal_entry *ie; 134 size_t idx; 135 136 if (htable == NULL) 137 return; 138 139 for (idx = 0; idx < htablesize; idx++) { 140 while (!SLIST_EMPTY(&htable[idx])) { 141 ie = SLIST_FIRST(&htable[idx]); 142 SLIST_REMOVE_HEAD(&htable[idx], link); 143 free(ie->ent.key); 144 free(ie); 145 } 146 } 147 free(htable); 148 htable = NULL; 149 } 150 151 ENTRY * 152 hsearch(ENTRY item, ACTION action) 153 { 154 struct internal_head *head; 155 struct internal_entry *ie; 156 uint32_t hashval; 157 size_t len; 158 159 len = strlen(item.key); 160 hashval = (*__default_hash)(item.key, len); 161 162 head = &htable[hashval & (htablesize - 1)]; 163 ie = SLIST_FIRST(head); 164 while (ie != NULL) { 165 if (strcmp(ie->ent.key, item.key) == 0) 166 break; 167 ie = SLIST_NEXT(ie, link); 168 } 169 170 if (ie != NULL) 171 return &ie->ent; 172 else if (action == FIND) 173 return NULL; 174 175 ie = malloc(sizeof *ie); 176 if (ie == NULL) 177 return NULL; 178 ie->ent.key = item.key; 179 ie->ent.data = item.data; 180 181 SLIST_INSERT_HEAD(head, ie, link); 182 return &ie->ent; 183 } 184