stdlib/hcreate-fbsd.c

   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: src/lib/libc/stdlib/hcreate.c,v 1.3 2002/06/27 13:18:27 deischen Exp $");
  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 }