FreeBSD/Linux Kernel Cross Reference
sys/libsa/sort.c

     /*
      * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
      *
      * @APPLE_LICENSE_HEADER_START@
      * 
      * The contents of this file constitute Original Code as defined in and
      * are subject to the Apple Public Source License Version 1.1 (the
      * "License").  You may not use this file except in compliance with the
      * License.  Please obtain a copy of the License at
     * http://www.apple.com/publicsource and read it before using this file.
     * 
     * This Original Code and all software distributed under the License are
     * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
     * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
     * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
     * License for the specific language governing rights and limitations
     * under the License.
     * 
     * @APPLE_LICENSE_HEADER_END@
     */
    /*-
     * Copyright (c) 1991, 1993
     *      The Regents of the University of California.  All rights reserved.
     *
     * This code is derived from software contributed to Berkeley by
     * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
     *
     * 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. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. 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.
     */
    
    #if defined(LIBC_SCCS) && !defined(lint)
    static char sccsid[] = "@(#)heapsort.c  8.1 (Berkeley) 6/4/93";
    #endif /* LIBC_SCCS and not lint */
    
    
    #include <libsa/stdlib.h>
    
    
    /*
     * Swap two areas of size number of bytes.  Although qsort(3) permits random
     * blocks of memory to be sorted, sorting pointers is almost certainly the
     * common case (and, were it not, could easily be made so).  Regardless, it
     * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
     * arithmetic gets lost in the time required for comparison function calls.
     */
    #define SWAP(a, b, count, size, tmp) { \
            count = size; \
            do { \
                    tmp = *a; \
                    *a++ = *b; \
                    *b++ = tmp; \
            } while (--count); \
    }
    
    /* Copy one block of size size to another. */
    #define COPY(a, b, count, size, tmp1, tmp2) { \
            count = size; \
            tmp1 = a; \
            tmp2 = b; \
            do { \
                    *tmp1++ = *tmp2++; \
            } while (--count); \
    }
    
    /*
     * Build the list into a heap, where a heap is defined such that for
     * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
     *
     * There two cases.  If j == nmemb, select largest of Ki and Kj.  If
     * j < nmemb, select largest of Ki, Kj and Kj+1.
     */
    #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
           for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
               par_i = child_i) { \
                   child = base + child_i * size; \
                   if (child_i < nmemb && compar(child, child + size) < 0) { \
                           child += size; \
                           ++child_i; \
                   } \
                   par = base + par_i * size; \
                   if (compar(child, par) <= 0) \
                           break; \
                   SWAP(par, child, count, size, tmp); \
           } \
   }
   
   /*
    * Select the top of the heap and 'heapify'.  Since by far the most expensive
    * action is the call to the compar function, a considerable optimization
    * in the average case can be achieved due to the fact that k, the displaced
    * elememt, is ususally quite small, so it would be preferable to first
    * heapify, always maintaining the invariant that the larger child is copied
    * over its parent's record.
    *
    * Then, starting from the *bottom* of the heap, finding k's correct place,
    * again maintianing the invariant.  As a result of the invariant no element
    * is 'lost' when k is assigned its correct place in the heap.
    *
    * The time savings from this optimization are on the order of 15-20% for the
    * average case. See Knuth, Vol. 3, page 158, problem 18.
    *
    * XXX Don't break the #define SELECT line, below.  Reiser cpp gets upset.
    */
   #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
           for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
                   child = base + child_i * size; \
                   if (child_i < nmemb && compar(child, child + size) < 0) { \
                           child += size; \
                           ++child_i; \
                   } \
                   par = base + par_i * size; \
                   COPY(par, child, count, size, tmp1, tmp2); \
           } \
           for (;;) { \
                   child_i = par_i; \
                   par_i = child_i / 2; \
                   child = base + child_i * size; \
                   par = base + par_i * size; \
                   if (child_i == 1 || compar(k, par) < 0) { \
                           COPY(child, k, count, size, tmp1, tmp2); \
                           break; \
                   } \
                   COPY(child, par, count, size, tmp1, tmp2); \
           } \
   }
   
   /* Pass heapsort off as qsort for krld. -- Nik Gervae
    *
    * Heapsort -- Knuth, Vol. 3, page 145.  Runs in O (N lg N), both average
    * and worst.  While heapsort is faster than the worst case of quicksort,
    * the BSD quicksort does median selection so that the chance of finding
    * a data set that will trigger the worst case is nonexistent.  Heapsort's
    * only advantage over quicksort is that it requires little additional memory.
    */
   __private_extern__
   void qsort(void * vbase, size_t nmemb, size_t size,
           int (*compar)(const void *, const void *)) {
   
           register int cnt, i, j, l;
           register char tmp, *tmp1, *tmp2;
           char *base, *k, *p, *t;
   
           if (nmemb <= 1) {
               return;
           }
   
           if (!size) {
               return;
           }
   
           if ((k = (char *)malloc(size)) == NULL) {
   //            panic();
               return;
           }
   
           /*
            * Items are numbered from 1 to nmemb, so offset from size bytes
            * below the starting address.
            */
           base = (char *)vbase - size;
   
           for (l = nmemb / 2 + 1; --l;)
                   CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
   
           /*
            * For each element of the heap, save the largest element into its
            * final slot, save the displaced element (k), then recreate the
            * heap.
            */
           while (nmemb > 1) {
                   COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
                   COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
                   --nmemb;
                   SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
           }
           free(k);
           return;
   }

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