FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_hash.c

     /*      $NetBSD: subr_hash.c,v 1.3 2008/05/05 17:11:17 ad Exp $ */
     
     /*
      * Copyright (c) 1982, 1986, 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * All or some portions of this file are derived from material licensed
      * to the University of California by American Telephone and Telegraph
      * Co. or Unix System Laboratories, Inc. and are reproduced herein with
     * the permission of UNIX System Laboratories, Inc.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)kern_subr.c 8.4 (Berkeley) 2/14/95
     */
    
    #include <sys/cdefs.h>
    __KERNEL_RCSID(0, "$NetBSD: subr_hash.c,v 1.3 2008/05/05 17:11:17 ad Exp $");
    
    #include <sys/param.h>
    #include <sys/kmem.h>
    #include <sys/systm.h>
    
    /*
     * General routine to allocate a hash table.
     * Allocate enough memory to hold at least `elements' list-head pointers.
     * Return a pointer to the allocated space and set *hashmask to a pattern
     * suitable for masking a value to use as an index into the returned array.
     */
    void *
    hashinit(u_int elements, enum hashtype htype, bool waitok, u_long *hashmask)
    {
            u_long hashsize, i;
            LIST_HEAD(, generic) *hashtbl_list;
            SLIST_HEAD(, generic) *hashtbl_slist;
            TAILQ_HEAD(, generic) *hashtbl_tailq;
            size_t esize;
            void *p;
    
            if (elements == 0)
                    panic("hashinit: bad cnt");
            for (hashsize = 1; hashsize < elements; hashsize <<= 1)
                    continue;
    
            switch (htype) {
            case HASH_LIST:
                    esize = sizeof(*hashtbl_list);
                    break;
            case HASH_SLIST:
                    esize = sizeof(*hashtbl_slist);
                    break;
            case HASH_TAILQ:
                    esize = sizeof(*hashtbl_tailq);
                    break;
            default:
                    panic("hashinit: invalid table type");
            }
    
            p = kmem_alloc(hashsize * esize, (waitok ? KM_SLEEP : KM_NOSLEEP));
            if (p == NULL)
                    return (NULL);
    
            switch (htype) {
            case HASH_LIST:
                    hashtbl_list = p;
                    for (i = 0; i < hashsize; i++)
                            LIST_INIT(&hashtbl_list[i]);
                    break;
            case HASH_SLIST:
                    hashtbl_slist = p;
                    for (i = 0; i < hashsize; i++)
                            SLIST_INIT(&hashtbl_slist[i]);
                    break;
            case HASH_TAILQ:
                    hashtbl_tailq = p;
                    for (i = 0; i < hashsize; i++)
                            TAILQ_INIT(&hashtbl_tailq[i]);
                   break;
           }
           *hashmask = hashsize - 1;
           return (p);
   }
   
   /*
    * Free memory from hash table previosly allocated via hashinit().
    */
   void
   hashdone(void *hashtbl, enum hashtype htype, u_long hashmask)
   {
           LIST_HEAD(, generic) *hashtbl_list;
           SLIST_HEAD(, generic) *hashtbl_slist;
           TAILQ_HEAD(, generic) *hashtbl_tailq;
           size_t esize;
   
           switch (htype) {
           case HASH_LIST:
                   esize = sizeof(*hashtbl_list);
                   break;
           case HASH_SLIST:
                   esize = sizeof(*hashtbl_slist);
                   break;
           case HASH_TAILQ:
                   esize = sizeof(*hashtbl_tailq);
                   break;
           default:
                   panic("hashdone: invalid table type");
           }
   
           kmem_free(hashtbl, esize * (hashmask + 1));
   }

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