src/system/libroot/posix/stdlib/heapsort.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. 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
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)heapsort.c  8.1 (Berkeley) 6/4/93";
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include <errno.h>
  42 #include <stdlib.h>
  43
  44 #include <errno_private.h>
  45
  46 /*
  47  * Swap two areas of size number of bytes.  Although qsort(3) permits random
  48  * blocks of memory to be sorted, sorting pointers is almost certainly the
  49  * common case (and, were it not, could easily be made so).  Regardless, it
  50  * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
  51  * arithmetic gets lost in the time required for comparison function calls.
  52  */
  53 #define SWAP(a, b, count, size, tmp) { \
  54         count = size; \
  55         do { \
  56                 tmp = *a; \
  57                 *a++ = *b; \
  58                 *b++ = tmp; \
  59         } while (--count); \
  60 }
  61
  62 /* Copy one block of size size to another. */
  63 #define COPY(a, b, count, size, tmp1, tmp2) { \
  64         count = size; \
  65         tmp1 = a; \
  66         tmp2 = b; \
  67         do { \
  68                 *tmp1++ = *tmp2++; \
  69         } while (--count); \
  70 }
  71
  72 /*
  73  * Build the list into a heap, where a heap is defined such that for
  74  * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
  75  *
  76  * There two cases.  If j == nmemb, select largest of Ki and Kj.  If
  77  * j < nmemb, select largest of Ki, Kj and Kj+1.
  78  */
  79 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
  80         for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
  81             par_i = child_i) { \
  82                 child = base + child_i * size; \
  83                 if (child_i < nmemb && compar(child, child + size) < 0) { \
  84                         child += size; \
  85                         ++child_i; \
  86                 } \
  87                 par = base + par_i * size; \
  88                 if (compar(child, par) <= 0) \
  89                         break; \
  90                 SWAP(par, child, count, size, tmp); \
  91         } \
  92 }
  93
  94 /*
  95  * Select the top of the heap and 'heapify'.  Since by far the most expensive
  96  * action is the call to the compar function, a considerable optimization
  97  * in the average case can be achieved due to the fact that k, the displaced
  98  * elememt, is ususally quite small, so it would be preferable to first
  99  * heapify, always maintaining the invariant that the larger child is copied
 100  * over its parent's record.
 101  *
 102  * Then, starting from the *bottom* of the heap, finding k's correct place,
 103  * again maintianing the invariant.  As a result of the invariant no element
 104  * is 'lost' when k is assigned its correct place in the heap.
 105  *
 106  * The time savings from this optimization are on the order of 15-20% for the
 107  * average case. See Knuth, Vol. 3, page 158, problem 18.
 108  *
 109  * XXX Don't break the #define SELECT line, below.  Reiser cpp gets upset.
 110  */
 111 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
 112         for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
 113                 child = base + child_i * size; \
 114                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 115                         child += size; \
 116                         ++child_i; \
 117                 } \
 118                 par = base + par_i * size; \
 119                 COPY(par, child, count, size, tmp1, tmp2); \
 120         } \
 121         for (;;) { \
 122                 child_i = par_i; \
 123                 par_i = child_i / 2; \
 124                 child = base + child_i * size; \
 125                 par = base + par_i * size; \
 126                 if (child_i == 1 || compar(k, par) < 0) { \
 127                         COPY(child, k, count, size, tmp1, tmp2); \
 128                         break; \
 129                 } \
 130                 COPY(child, par, count, size, tmp1, tmp2); \
 131         } \
 132 }
 133
 134 /*
 135  * Heapsort -- Knuth, Vol. 3, page 145.  Runs in O (N lg N), both average
 136  * and worst.  While heapsort is faster than the worst case of quicksort,
 137  * the BSD quicksort does median selection so that the chance of finding
 138  * a data set that will trigger the worst case is nonexistent.  Heapsort's
 139  * only advantage over quicksort is that it requires little additional memory.
 140  */
 141 int
 142 heapsort(void *vbase, size_t nmemb, size_t size, int (*compar)(void const *, void const *))
 143 {
 144         size_t cnt;
 145         size_t i;
 146         size_t j;
 147         size_t l;
 148         char tmp;
 149         char *tmp1;
 150         char *tmp2;
 151         char *base;
 152         char *k;
 153         char *p;
 154         char *t;
 155
 156         if (nmemb <= 1) {
 157                 return (0);
 158         }
 159
 160         if (!size) {
 161 //              __set_errno(EINVAL);
 162                 return (-1);
 163         }
 164
 165         if ((k = malloc(size)) == NULL) {
 166                 return (-1);
 167         }
 168
 169         /*
 170          * Items are numbered from 1 to nmemb, so offset from size bytes
 171          * below the starting address.
 172          */
 173         base = (char *)vbase - size;
 174
 175         for (l = nmemb / 2 + 1; --l;)
 176                 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
 177
 178         /*
 179          * For each element of the heap, save the largest element into its
 180          * final slot, save the displaced element (k), then recreate the
 181          * heap.
 182          */
 183         while (nmemb > 1) {
 184                 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
 185                 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
 186                 --nmemb;
 187                 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
 188         }
 189         free(k);
 190         return (0);
 191 }