1 /* $NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $ */ 2 /* $FreeBSD$ */ 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 #include "namespace.h" 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 this isn't called when a table already exists. */ 96 if (htable != NULL) { 97 errno = EINVAL; 98 return 0; 99 } 100 101 /* If nel is too small, make it min sized. */ 102 if (nel < MIN_BUCKETS) 103 nel = MIN_BUCKETS; 104 105 /* If it's too large, cap it. */ 106 if (nel > MAX_BUCKETS) 107 nel = MAX_BUCKETS; 108 109 /* If it's is not a power of two in size, round up. */ 110 if ((nel & (nel - 1)) != 0) { 111 for (p2 = 0; nel != 0; p2++) 112 nel >>= 1; 113 nel = 1 << p2; 114 } 115 116 /* Allocate the table. */ 117 htablesize = nel; 118 htable = malloc(htablesize * sizeof htable[0]); 119 if (htable == NULL) { 120 errno = ENOMEM; 121 return 0; 122 } 123 124 /* Initialize it. */ 125 for (idx = 0; idx < htablesize; idx++) 126 SLIST_INIT(&htable[idx]); 127 128 return 1; 129 } 130 131 void 132 hdestroy(void) 133 { 134 struct internal_entry *ie; 135 size_t idx; 136 137 if (htable == NULL) 138 return; 139 140 for (idx = 0; idx < htablesize; idx++) { 141 while (!SLIST_EMPTY(&htable[idx])) { 142 ie = SLIST_FIRST(&htable[idx]); 143 SLIST_REMOVE_HEAD(&htable[idx], link); 144 free(ie->ent.key); 145 free(ie); 146 } 147 } 148 free(htable); 149 htable = NULL; 150 } 151 152 ENTRY * 153 hsearch(ENTRY item, ACTION action) 154 { 155 struct internal_head *head; 156 struct internal_entry *ie; 157 uint32_t hashval; 158 size_t len; 159 160 len = strlen(item.key); 161 hashval = (*__default_hash)(item.key, len); 162 163 head = &htable[hashval & (htablesize - 1)]; 164 ie = SLIST_FIRST(head); 165 while (ie != NULL) { 166 if (strcmp(ie->ent.key, item.key) == 0) 167 break; 168 ie = SLIST_NEXT(ie, link); 169 } 170 171 if (ie != NULL) 172 return &ie->ent; 173 else if (action == FIND) 174 return NULL; 175 176 ie = malloc(sizeof *ie); 177 if (ie == NULL) 178 return NULL; 179 ie->ent.key = item.key; 180 ie->ent.data = item.data; 181 182 SLIST_INSERT_HEAD(head, ie, link); 183 return &ie->ent; 184 } 185