sys/kern/subr_hash.c

   1 /*      $NetBSD: subr_hash.c,v 1.2 2008/03/17 21:16:03 rmind Exp $      */
   2
   3 /*
   4  * Copyright (c) 1982, 1986, 1991, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  * (c) UNIX System Laboratories, Inc.
   7  * All or some portions of this file are derived from material licensed
   8  * to the University of California by American Telephone and Telegraph
   9  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
  10  * the permission of UNIX System Laboratories, Inc.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  * 3. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  *      @(#)kern_subr.c 8.4 (Berkeley) 2/14/95
  37  */
  38
  39 #include <sys/cdefs.h>
  40 __KERNEL_RCSID(0, "$NetBSD: subr_hash.c,v 1.2 2008/03/17 21:16:03 rmind Exp $");
  41
  42 #include <sys/param.h>
  43 #include <sys/kmem.h>
  44 #include <sys/systm.h>
  45
  46 /*
  47  * General routine to allocate a hash table.
  48  * Allocate enough memory to hold at least `elements' list-head pointers.
  49  * Return a pointer to the allocated space and set *hashmask to a pattern
  50  * suitable for masking a value to use as an index into the returned array.
  51  */
  52 void *
  53 hashinit(u_int elements, enum hashtype htype, bool waitok, u_long *hashmask)
  54 {
  55         u_long hashsize, i;
  56         LIST_HEAD(, generic) *hashtbl_list;
  57         SLIST_HEAD(, generic) *hashtbl_slist;
  58         TAILQ_HEAD(, generic) *hashtbl_tailq;
  59         size_t esize;
  60         void *p;
  61
  62         if (elements == 0)
  63                 panic("hashinit: bad cnt");
  64         for (hashsize = 1; hashsize < elements; hashsize <<= 1)
  65                 continue;
  66
  67         switch (htype) {
  68         case HASH_LIST:
  69                 esize = sizeof(*hashtbl_list);
  70                 break;
  71         case HASH_SLIST:
  72                 esize = sizeof(*hashtbl_slist);
  73                 break;
  74         case HASH_TAILQ:
  75                 esize = sizeof(*hashtbl_tailq);
  76                 break;
  77         default:
  78                 panic("hashinit: invalid table type");
  79         }
  80
  81         p = kmem_alloc(hashsize * esize, (waitok ? KM_SLEEP : KM_NOSLEEP));
  82         if (p == NULL)
  83                 return (NULL);
  84
  85         switch (htype) {
  86         case HASH_LIST:
  87                 hashtbl_list = p;
  88                 for (i = 0; i < hashsize; i++)
  89                         LIST_INIT(&hashtbl_list[i]);
  90                 break;
  91         case HASH_SLIST:
  92                 hashtbl_slist = p;
  93                 for (i = 0; i < hashsize; i++)
  94                         SLIST_INIT(&hashtbl_slist[i]);
  95                 break;
  96         case HASH_TAILQ:
  97                 hashtbl_tailq = p;
  98                 for (i = 0; i < hashsize; i++)
  99                         TAILQ_INIT(&hashtbl_tailq[i]);
 100                 break;
 101         }
 102         *hashmask = hashsize - 1;
 103         return (p);
 104 }
 105
 106 /*
 107  * Free memory from hash table previosly allocated via hashinit().
 108  */
 109 void
 110 hashdone(void *hashtbl, enum hashtype htype, u_long hashmask)
 111 {
 112         LIST_HEAD(, generic) *hashtbl_list;
 113         SLIST_HEAD(, generic) *hashtbl_slist;
 114         TAILQ_HEAD(, generic) *hashtbl_tailq;
 115         size_t esize;
 116
 117         switch (htype) {
 118         case HASH_LIST:
 119                 esize = sizeof(*hashtbl_list);
 120                 break;
 121         case HASH_SLIST:
 122                 esize = sizeof(*hashtbl_slist);
 123                 break;
 124         case HASH_TAILQ:
 125                 esize = sizeof(*hashtbl_tailq);
 126                 break;
 127         default:
 128                 panic("hashdone: invalid table type");
 129         }
 130
 131         kmem_free(hashtbl, esize * (hashmask + 1));
 132 }