lib/libc/stdlib/hcreate.c

   1 /*
   2  * Copyright (c) 2001 Christopher G. Demetriou
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *          This product includes software developed for the
  16  *          NetBSD Project.  See http://www.netbsd.org/ for
  17  *          information about NetBSD.
  18  * 4. The name of the author may not be used to endorse or promote products
  19  *    derived from this software without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  31  *
  32  * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
  33  *
  34  * $NetBSD: hcreate.c,v 1.2 2001/02/19 21:26:04 ross Exp $
  35  * $FreeBSD: src/lib/libc/stdlib/hcreate.c,v 1.4 2008/07/06 11:31:20 danger Exp $
  36  * $DragonFly: src/lib/libc/stdlib/hcreate.c,v 1.2 2003/06/17 04:26:46 dillon Exp $
  37  */
  38
  39 /*
  40  * hcreate() / hsearch() / hdestroy()
  41  *
  42  * SysV/XPG4 hash table functions.
  43  *
  44  * Implementation done based on NetBSD manual page and Solaris manual page,
  45  * plus my own personal experience about how they're supposed to work.
  46  *
  47  * I tried to look at Knuth (as cited by the Solaris manual page), but
  48  * nobody had a copy in the office, so...
  49  */
  50
  51 #include <sys/types.h>
  52 #include <sys/queue.h>
  53 #include <errno.h>
  54 #include <search.h>
  55 #include <stdlib.h>
  56 #include <string.h>
  57
  58 /*
  59  * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
  60  * ptr machine) without adjusting MAX_BUCKETS_LG2 below.
  61  */
  62 struct internal_entry {
  63         SLIST_ENTRY(internal_entry) link;
  64         ENTRY ent;
  65 };
  66 SLIST_HEAD(internal_head, internal_entry);
  67
  68 #define MIN_BUCKETS_LG2 4
  69 #define MIN_BUCKETS     (1 << MIN_BUCKETS_LG2)
  70
  71 /*
  72  * max * sizeof internal_entry must fit into size_t.
  73  * assumes internal_entry is <= 32 (2^5) bytes.
  74  */
  75 #define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
  76 #define MAX_BUCKETS     ((size_t)1 << MAX_BUCKETS_LG2)
  77
  78 /* Default hash function, from db/hash/hash_func.c */
  79 extern u_int32_t (*__default_hash)(const void *, size_t);
  80
  81 static struct internal_head *htable;
  82 static size_t htablesize;
  83
  84 int
  85 hcreate(size_t nel)
  86 {
  87         size_t idx;
  88         unsigned int p2;
  89
  90         /* Make sure this is not called when a table already exists. */
  91         if (htable != NULL) {
  92                 errno = EINVAL;
  93                 return 0;
  94         }
  95
  96         /* If nel is too small, make it min sized. */
  97         if (nel < MIN_BUCKETS)
  98                 nel = MIN_BUCKETS;
  99
 100         /* If it is too large, cap it. */
 101         if (nel > MAX_BUCKETS)
 102                 nel = MAX_BUCKETS;
 103
 104         /* If it is not a power of two in size, round up. */
 105         if ((nel & (nel - 1)) != 0) {
 106                 for (p2 = 0; nel != 0; p2++)
 107                         nel >>= 1;
 108                 nel = 1 << p2;
 109         }
 110
 111         /* Allocate the table. */
 112         htablesize = nel;
 113         htable = malloc(htablesize * sizeof htable[0]);
 114         if (htable == NULL) {
 115                 errno = ENOMEM;
 116                 return 0;
 117         }
 118
 119         /* Initialize it. */
 120         for (idx = 0; idx < htablesize; idx++)
 121                 SLIST_INIT(&htable[idx]);
 122
 123         return 1;
 124 }
 125
 126 void
 127 hdestroy(void)
 128 {
 129         struct internal_entry *ie;
 130         size_t idx;
 131
 132         if (htable == NULL)
 133                 return;
 134
 135         for (idx = 0; idx < htablesize; idx++) {
 136                 while (!SLIST_EMPTY(&htable[idx])) {
 137                         ie = SLIST_FIRST(&htable[idx]);
 138                         SLIST_REMOVE_HEAD(&htable[idx], link);
 139                         free(ie->ent.key);
 140                         free(ie);
 141                 }
 142         }
 143         free(htable);
 144         htable = NULL;
 145 }
 146
 147 ENTRY *
 148 hsearch(ENTRY item, ACTION action)
 149 {
 150         struct internal_head *head;
 151         struct internal_entry *ie;
 152         uint32_t hashval;
 153         size_t len;
 154
 155         len = strlen(item.key);
 156         hashval = (*__default_hash)(item.key, len);
 157
 158         head = &htable[hashval & (htablesize - 1)];
 159         ie = SLIST_FIRST(head);
 160         while (ie != NULL) {
 161                 if (strcmp(ie->ent.key, item.key) == 0)
 162                         break;
 163                 ie = SLIST_NEXT(ie, link);
 164         }
 165
 166         if (ie != NULL)
 167                 return &ie->ent;
 168         else if (action == FIND)
 169                 return NULL;
 170
 171         ie = malloc(sizeof *ie);
 172         if (ie == NULL)
 173                 return NULL;
 174         ie->ent.key = item.key;
 175         ie->ent.data = item.data;
 176
 177         SLIST_INSERT_HEAD(head, ie, link);
 178         return &ie->ent;
 179 }