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 #include "namespace.h" 64 65 /* 66 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit 67 * ptr machine) without adjusting MAX_BUCKETS_LG2 below. 68 */ 69 struct internal_entry { 70 SLIST_ENTRY(internal_entry) link; 71 ENTRY ent; 72 }; 73 SLIST_HEAD(internal_head, internal_entry); 74 75 #define MIN_BUCKETS_LG2 4 76 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2) 77 78 /* 79 * max * sizeof internal_entry must fit into size_t. 80 * assumes internal_entry is <= 32 (2^5) bytes. 81 */ 82 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5) 83 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2) 84 85 /* Default hash function, from db/hash/hash_func.c */ 86 extern u_int32_t (*__default_hash)(const void *, size_t); 87 88 static struct internal_head *htable; 89 static size_t htablesize; 90 91 int 92 hcreate(size_t nel) 93 { 94 size_t idx; 95 unsigned int p2; 96 97 /* Make sure this this isn't called when a table already exists. */ 98 if (htable != NULL) { 99 errno = EINVAL; 100 return 0; 101 } 102 103 /* If nel is too small, make it min sized. */ 104 if (nel < MIN_BUCKETS) 105 nel = MIN_BUCKETS; 106 107 /* If it's too large, cap it. */ 108 if (nel > MAX_BUCKETS) 109 nel = MAX_BUCKETS; 110 111 /* If it's is not a power of two in size, round up. */ 112 if ((nel & (nel - 1)) != 0) { 113 for (p2 = 0; nel != 0; p2++) 114 nel >>= 1; 115 nel = 1 << p2; 116 } 117 118 /* Allocate the table. */ 119 htablesize = nel; 120 htable = malloc(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 if (htable == NULL) 140 return; 141 142 for (idx = 0; idx < htablesize; idx++) { 143 while (!SLIST_EMPTY(&htable[idx])) { 144 ie = SLIST_FIRST(&htable[idx]); 145 SLIST_REMOVE_HEAD(&htable[idx], link); 146 free(ie->ent.key); 147 free(ie); 148 } 149 } 150 free(htable); 151 htable = NULL; 152 } 153 154 ENTRY * 155 hsearch(ENTRY item, ACTION action) 156 { 157 struct internal_head *head; 158 struct internal_entry *ie; 159 uint32_t hashval; 160 size_t len; 161 162 len = strlen(item.key); 163 hashval = (*__default_hash)(item.key, len); 164 165 head = &htable[hashval & (htablesize - 1)]; 166 ie = SLIST_FIRST(head); 167 while (ie != NULL) { 168 if (strcmp(ie->ent.key, item.key) == 0) 169 break; 170 ie = SLIST_NEXT(ie, link); 171 } 172 173 if (ie != NULL) 174 return &ie->ent; 175 else if (action == FIND) 176 return NULL; 177 178 ie = malloc(sizeof *ie); 179 if (ie == NULL) 180 return NULL; 181 ie->ent.key = item.key; 182 ie->ent.data = item.data; 183 184 SLIST_INSERT_HEAD(head, ie, link); 185 return &ie->ent; 186 } 187