common/lib/libc/stdlib/heapsort.c

   1 /*      $NetBSD: heapsort.c,v 1.3 2008/11/17 10:21:30 jnemeth Exp $     */
   2
   3 /*-
   4  * Copyright (c) 1991, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Ronnie Kon at Mindcraft Inc., Kevin Lew and Elmer Yglesias.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #if HAVE_NBTOOL_CONFIG_H
  36 #include "nbtool_config.h"
  37 /*
  38  * XXX Undefine the renames of these functions so that we don't
  39  * XXX rename the versions found in the host's headers by mistake!
  40  */
  41 #undef heapsort
  42 #endif
  43
  44 #include <sys/cdefs.h>
  45 #if defined(LIBC_SCCS) && !defined(lint)
  46 #if 0
  47 static char sccsid[] = "from: @(#)heapsort.c    8.1 (Berkeley) 6/4/93";
  48 #else
  49 __RCSID("$NetBSD: heapsort.c,v 1.3 2008/11/17 10:21:30 jnemeth Exp $");
  50 #endif
  51 #endif /* LIBC_SCCS and not lint */
  52
  53 #if defined(_KERNEL) || defined(_STANDALONE)
  54 #include <sys/types.h>
  55
  56 #include <lib/libkern/libkern.h>
  57 #else   /* _KERNEL || _STANDALONE */
  58 #include "namespace.h"
  59 #include <sys/types.h>
  60
  61 #include <assert.h>
  62 #include <errno.h>
  63 #include <stdlib.h>
  64
  65 #if HAVE_NBTOOL_CONFIG_H
  66 /* XXX Now, re-apply the renaming that we undid above. */
  67 #define heapsort        __nbcompat_heapsort
  68 #endif
  69
  70 #ifdef __weak_alias
  71 __weak_alias(heapsort,_heapsort)
  72 #endif
  73 #endif  /* _KERNEL || _STANDALONE */
  74
  75 /*
  76  * Swap two areas of size number of bytes.  Although qsort(3) permits random
  77  * blocks of memory to be sorted, sorting pointers is almost certainly the
  78  * common case (and, were it not, could easily be made so).  Regardless, it
  79  * isn't worth optimizing; the SWAP's get sped up by the cache, and pointer
  80  * arithmetic gets lost in the time required for comparison function calls.
  81  */
  82 #define SWAP(a, b, count, size, tmp) { \
  83         count = size; \
  84         do { \
  85                 tmp = *a; \
  86                 *a++ = *b; \
  87                 *b++ = tmp; \
  88         } while (--count); \
  89 }
  90
  91 /* Copy one block of size size to another. */
  92 #define COPY(a, b, count, size, tmp1, tmp2) { \
  93         count = size; \
  94         tmp1 = a; \
  95         tmp2 = b; \
  96         do { \
  97                 *tmp1++ = *tmp2++; \
  98         } while (--count); \
  99 }
 100
 101 /*
 102  * Build the list into a heap, where a heap is defined such that for
 103  * the records K1 ... KN, Kj/2 >= Kj for 1 <= j/2 <= j <= N.
 104  *
 105  * There are two cases.  If j == nmemb, select largest of Ki and Kj.  If
 106  * j < nmemb, select largest of Ki, Kj and Kj+1.
 107  */
 108 #define CREATE(initval, nmemb, par_i, child_i, par, child, size, count, tmp) { \
 109         for (par_i = initval; (child_i = par_i * 2) <= nmemb; \
 110             par_i = child_i) { \
 111                 child = base + child_i * size; \
 112                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 113                         child += size; \
 114                         ++child_i; \
 115                 } \
 116                 par = base + par_i * size; \
 117                 if (compar(child, par) <= 0) \
 118                         break; \
 119                 SWAP(par, child, count, size, tmp); \
 120         } \
 121 }
 122
 123 /*
 124  * Select the top of the heap and 'heapify'.  Since by far the most expensive
 125  * action is the call to the compar function, a considerable optimization
 126  * in the average case can be achieved due to the fact that k, the displaced
 127  * element, is usually quite small, so it would be preferable to first
 128  * heapify, always maintaining the invariant that the larger child is copied
 129  * over its parent's record.
 130  *
 131  * Then, starting from the *bottom* of the heap, finding k's correct place,
 132  * again maintaining the invariant.  As a result of the invariant no element
 133  * is 'lost' when k is assigned its correct place in the heap.
 134  *
 135  * The time savings from this optimization are on the order of 15-20% for the
 136  * average case. See Knuth, Vol. 3, page 158, problem 18.
 137  *
 138  * XXX Don't break the #define SELECT line, below.  Reiser cpp gets upset.
 139  */
 140 #define SELECT(par_i, child_i, nmemb, par, child, size, k, count, tmp1, tmp2) { \
 141         for (par_i = 1; (child_i = par_i * 2) <= nmemb; par_i = child_i) { \
 142                 child = base + child_i * size; \
 143                 if (child_i < nmemb && compar(child, child + size) < 0) { \
 144                         child += size; \
 145                         ++child_i; \
 146                 } \
 147                 par = base + par_i * size; \
 148                 COPY(par, child, count, size, tmp1, tmp2); \
 149         } \
 150         for (;;) { \
 151                 child_i = par_i; \
 152                 par_i = child_i / 2; \
 153                 child = base + child_i * size; \
 154                 par = base + par_i * size; \
 155                 if (child_i == 1 || compar(k, par) < 0) { \
 156                         COPY(child, k, count, size, tmp1, tmp2); \
 157                         break; \
 158                 } \
 159                 COPY(child, par, count, size, tmp1, tmp2); \
 160         } \
 161 }
 162
 163 /*
 164  * Heapsort -- Knuth, Vol. 3, page 145.  Runs in O (N lg N), both average
 165  * and worst.  While heapsort is faster than the worst case of quicksort,
 166  * the BSD quicksort does median selection so that the chance of finding
 167  * a data set that will trigger the worst case is nonexistent.  Heapsort's
 168  * only advantage over quicksort is that it requires little additional memory.
 169  */
 170 #if defined(_KERNEL) || defined(_STANDALONE)
 171 int
 172 kheapsort(void *vbase, size_t nmemb, size_t size,
 173     int (*compar)(const void *, const void *), void *k)
 174 #else
 175 int
 176 heapsort(void *vbase, size_t nmemb, size_t size,
 177     int (*compar)(const void *, const void *))
 178 #endif
 179 {
 180         size_t cnt, i, j, l;
 181         char tmp, *tmp1, *tmp2;
 182         char *base, *p, *t;
 183 #if !defined(_KERNEL) && !defined(_STANDALONE)
 184         char *k;
 185 #endif
 186
 187         _DIAGASSERT(vbase != NULL);
 188         _DIAGASSERT(compar != NULL);
 189
 190         if (nmemb <= 1)
 191                 return (0);
 192
 193         if (!size) {
 194 #if !defined(_KERNEL) && !defined(_STANDALONE)
 195                 errno = EINVAL;
 196 #endif
 197                 return (-1);
 198         }
 199
 200 #if !defined(_KERNEL) && !defined(_STANDALONE)
 201         if ((k = malloc(size)) == NULL)
 202                 return (-1);
 203 #endif
 204
 205         /*
 206          * Items are numbered from 1 to nmemb, so offset from size bytes
 207          * below the starting address.
 208          */
 209         base = (char *)vbase - size;
 210
 211         for (l = nmemb / 2 + 1; --l;)
 212                 CREATE(l, nmemb, i, j, t, p, size, cnt, tmp);
 213
 214         /*
 215          * For each element of the heap, save the largest element into its
 216          * final slot, save the displaced element (k), then recreate the
 217          * heap.
 218          */
 219         while (nmemb > 1) {
 220                 COPY(k, base + nmemb * size, cnt, size, tmp1, tmp2);
 221                 COPY(base + nmemb * size, base + size, cnt, size, tmp1, tmp2);
 222                 --nmemb;
 223                 SELECT(i, j, nmemb, t, p, size, k, cnt, tmp1, tmp2);
 224         }
 225 #if !defined(_KERNEL) && !defined(_STANDALONE)
 226         free(k);
 227 #endif
 228         return (0);
 229 }