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

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * 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 8.3 (Berkeley) 1/21/94
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/12.0/sys/kern/subr_hash.c 328238 2018-01-22 02:08:10Z pfg $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/malloc.h>
    
    static __inline int
    hash_mflags(int flags)
    {
    
            return ((flags & HASH_NOWAIT) ? M_NOWAIT : M_WAITOK);
    }
    
    /*
     * General routine to allocate a hash table with control of memory flags.
     */
    void *
    hashinit_flags(int elements, struct malloc_type *type, u_long *hashmask,
        int flags)
    {
            long hashsize, i;
            LIST_HEAD(generic, generic) *hashtbl;
    
            KASSERT(elements > 0, ("%s: bad elements", __func__));
            /* Exactly one of HASH_WAITOK and HASH_NOWAIT must be set. */
            KASSERT((flags & HASH_WAITOK) ^ (flags & HASH_NOWAIT),
                ("Bad flags (0x%x) passed to hashinit_flags", flags));
    
            for (hashsize = 1; hashsize <= elements; hashsize <<= 1)
                    continue;
            hashsize >>= 1;
    
            hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl), type,
                hash_mflags(flags));
            if (hashtbl != NULL) {
                    for (i = 0; i < hashsize; i++)
                            LIST_INIT(&hashtbl[i]);
                    *hashmask = hashsize - 1;
            }
            return (hashtbl);
    }
    
    /*
     * Allocate and initialize a hash table with default flag: may sleep.
     */
    void *
    hashinit(int elements, struct malloc_type *type, u_long *hashmask)
    {
    
            return (hashinit_flags(elements, type, hashmask, HASH_WAITOK));
    }
    
    void
    hashdestroy(void *vhashtbl, struct malloc_type *type, u_long hashmask)
    {
            LIST_HEAD(generic, generic) *hashtbl, *hp;
    
            hashtbl = vhashtbl;
            for (hp = hashtbl; hp <= &hashtbl[hashmask]; hp++)
                    KASSERT(LIST_EMPTY(hp), ("%s: hashtbl %p not empty "
                       "(malloc type %s)", __func__, hashtbl, type->ks_shortdesc));
           free(hashtbl, type);
   }
   
   static const int primes[] = { 1, 13, 31, 61, 127, 251, 509, 761, 1021, 1531,
                           2039, 2557, 3067, 3583, 4093, 4603, 5119, 5623, 6143,
                           6653, 7159, 7673, 8191, 12281, 16381, 24571, 32749 };
   #define NPRIMES nitems(primes)
   
   /*
    * General routine to allocate a prime number sized hash table with control of
    * memory flags.
    */
   void *
   phashinit_flags(int elements, struct malloc_type *type, u_long *nentries, int flags)
   {
           long hashsize, i;
           LIST_HEAD(generic, generic) *hashtbl;
   
           KASSERT(elements > 0, ("%s: bad elements", __func__));
           /* Exactly one of HASH_WAITOK and HASH_NOWAIT must be set. */
           KASSERT((flags & HASH_WAITOK) ^ (flags & HASH_NOWAIT),
               ("Bad flags (0x%x) passed to phashinit_flags", flags));
   
           for (i = 1, hashsize = primes[1]; hashsize <= elements;) {
                   i++;
                   if (i == NPRIMES)
                           break;
                   hashsize = primes[i];
           }
           hashsize = primes[i - 1];
   
           hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl), type,
               hash_mflags(flags));
           if (hashtbl == NULL)
                   return (NULL);
   
           for (i = 0; i < hashsize; i++)
                   LIST_INIT(&hashtbl[i]);
           *nentries = hashsize;
           return (hashtbl);
   }
   
   /*
    * Allocate and initialize a prime number sized hash table with default flag:
    * may sleep.
    */
   void *
   phashinit(int elements, struct malloc_type *type, u_long *nentries)
   {
   
           return (phashinit_flags(elements, type, nentries, HASH_WAITOK));
   }

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