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subr_hash.c revision 1.3.34.2 
      1 /*	$NetBSD: subr_hash.c,v 1.3.34.2 2012/10/30 17:22:33 yamt 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 1.3.34.2 2012/10/30 17:22:33 yamt Exp $");
     41 
     42 #include <sys/param.h>
     43 #include <sys/kmem.h>
     44 #include <sys/systm.h>
     45 
     46 static size_t
     47 hash_list_size(enum hashtype htype)
     48 {
     49 	LIST_HEAD(, generic) *hashtbl_list;
     50 	SLIST_HEAD(, generic) *hashtbl_slist;
     51 	TAILQ_HEAD(, generic) *hashtbl_tailq;
     52 	size_t esize;
     53 
     54 	switch (htype) {
     55 	case HASH_LIST:
     56 		esize = sizeof(*hashtbl_list);
     57 		break;
     58 	case HASH_SLIST:
     59 		esize = sizeof(*hashtbl_slist);
     60 		break;
     61 	case HASH_TAILQ:
     62 		esize = sizeof(*hashtbl_tailq);
     63 		break;
     64 	default:
     65 		panic("hashdone: invalid table type");
     66 	}
     67 	return esize;
     68 }
     69 
     70 /*
     71  * General routine to allocate a hash table.
     72  * Allocate enough memory to hold at least `elements' list-head pointers.
     73  * Return a pointer to the allocated space and set *hashmask to a pattern
     74  * suitable for masking a value to use as an index into the returned array.
     75  */
     76 void *
     77 hashinit(u_int elements, enum hashtype htype, bool waitok, u_long *hashmask)
     78 {
     79 	LIST_HEAD(, generic) *hashtbl_list;
     80 	SLIST_HEAD(, generic) *hashtbl_slist;
     81 	TAILQ_HEAD(, generic) *hashtbl_tailq;
     82 	u_long hashsize, i;
     83 	size_t esize;
     84 	void *p;
     85 
     86 	KASSERT(elements > 0);
     87 
     88 #define MAXELEMENTS (1U << ((sizeof(elements) * NBBY) - 1))
     89 	if (elements > MAXELEMENTS)
     90 		elements = MAXELEMENTS;
     91 
     92 	for (hashsize = 1; hashsize < elements; hashsize <<= 1)
     93 		continue;
     94 
     95 	esize = hash_list_size(htype);
     96 	p = kmem_alloc(hashsize * esize, waitok ? KM_SLEEP : KM_NOSLEEP);
     97 	if (p == NULL)
     98 		return NULL;
     99 
    100 	switch (htype) {
    101 	case HASH_LIST:
    102 		hashtbl_list = p;
    103 		for (i = 0; i < hashsize; i++)
    104 			LIST_INIT(&hashtbl_list[i]);
    105 		break;
    106 	case HASH_SLIST:
    107 		hashtbl_slist = p;
    108 		for (i = 0; i < hashsize; i++)
    109 			SLIST_INIT(&hashtbl_slist[i]);
    110 		break;
    111 	case HASH_TAILQ:
    112 		hashtbl_tailq = p;
    113 		for (i = 0; i < hashsize; i++)
    114 			TAILQ_INIT(&hashtbl_tailq[i]);
    115 		break;
    116 	}
    117 	*hashmask = hashsize - 1;
    118 	return p;
    119 }
    120 
    121 /*
    122  * Free memory from hash table previosly allocated via hashinit().
    123  */
    124 void
    125 hashdone(void *hashtbl, enum hashtype htype, u_long hashmask)
    126 {
    127 	const size_t esize = hash_list_size(htype);
    128 	kmem_free(hashtbl, esize * (hashmask + 1));
    129 }
    130