1 /* $NetBSD: hcreate.c,v 1.3 2001/02/21 16:31:01 lukem 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 defined(LIBC_SCCS) && !defined(lint) 51 __RCSID("$NetBSD: hcreate.c,v 1.3 2001/02/21 16:31:01 lukem Exp $"); 52 #endif /* LIBC_SCCS and not lint */ 53 54 #if !defined(lint) 55 __COPYRIGHT( 56 "@(#) Copyright (c) 2001 Christopher G. Demetriou. All rights reserved.\n"); 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 /* 69 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit 70 * ptr machine) without adjusting MAX_BUCKETS_LG2 below. 71 */ 72 struct internal_entry { 73 SLIST_ENTRY(internal_entry) link; 74 ENTRY ent; 75 }; 76 SLIST_HEAD(internal_head, internal_entry); 77 78 #define MIN_BUCKETS_LG2 4 79 #define MIN_BUCKETS (1 << MIN_BUCKETS_LG2) 80 81 /* 82 * max * sizeof internal_entry must fit into size_t. 83 * assumes internal_entry is <= 32 (2^5) bytes. 84 */ 85 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5) 86 #define MAX_BUCKETS ((size_t)1 << MAX_BUCKETS_LG2) 87 88 /* Default hash function, from db/hash/hash_func.c */ 89 extern u_int32_t (*__default_hash)(const void *, size_t); 90 91 static struct internal_head *htable; 92 static size_t htablesize; 93 94 int 95 hcreate(size_t nel) 96 { 97 size_t idx; 98 unsigned int p2; 99 100 /* Make sure this this isn't called when a table already exists. */ 101 _DIAGASSERT(htable == NULL); 102 if (htable != NULL) { 103 errno = EINVAL; 104 return 0; 105 } 106 107 /* If nel is too small, make it min sized. */ 108 if (nel < MIN_BUCKETS) 109 nel = MIN_BUCKETS; 110 111 /* If it's too large, cap it. */ 112 if (nel > MAX_BUCKETS) 113 nel = MAX_BUCKETS; 114 115 /* If it's is not a power of two in size, round up. */ 116 if ((nel & (nel - 1)) != 0) { 117 for (p2 = 0; nel != 0; p2++) 118 nel >>= 1; 119 _DIAGASSERT(p2 <= MAX_BUCKETS_LG2); 120 nel = 1 << p2; 121 } 122 123 /* Allocate the table. */ 124 htablesize = nel; 125 htable = malloc(htablesize * sizeof htable[0]); 126 if (htable == NULL) { 127 errno = ENOMEM; 128 return 0; 129 } 130 131 /* Initialize it. */ 132 for (idx = 0; idx < htablesize; idx++) 133 SLIST_INIT(&htable[idx]); 134 135 return 1; 136 } 137 138 void 139 hdestroy(void) 140 { 141 struct internal_entry *ie; 142 size_t idx; 143 144 _DIAGASSERT(htable != NULL); 145 if (htable == NULL) 146 return; 147 148 for (idx = 0; idx < htablesize; idx++) { 149 while (!SLIST_EMPTY(&htable[idx])) { 150 ie = SLIST_FIRST(&htable[idx]); 151 SLIST_REMOVE_HEAD(&htable[idx], link); 152 free(ie->ent.key); 153 free(ie); 154 } 155 } 156 free(htable); 157 htable = NULL; 158 } 159 160 ENTRY * 161 hsearch(ENTRY item, ACTION action) 162 { 163 struct internal_head *head; 164 struct internal_entry *ie; 165 uint32_t hashval; 166 size_t len; 167 168 _DIAGASSERT(htable != NULL); 169 _DIAGASSERT(item.key != NULL); 170 _DIAGASSERT(action == ENTER || action == FIND); 171 172 len = strlen(item.key); 173 hashval = (*__default_hash)(item.key, len); 174 175 head = &htable[hashval & (htablesize - 1)]; 176 ie = SLIST_FIRST(head); 177 while (ie != NULL) { 178 if (strcmp(ie->ent.key, item.key) == 0) 179 break; 180 ie = SLIST_NEXT(ie, link); 181 } 182 183 if (ie != NULL) 184 return &ie->ent; 185 else if (action == FIND) 186 return NULL; 187 188 ie = malloc(sizeof *ie); 189 if (ie == NULL) 190 return NULL; 191 ie->ent.key = item.key; 192 ie->ent.data = item.data; 193 194 SLIST_INSERT_HEAD(head, ie, link); 195 return &ie->ent; 196 } 197