lib/libc/stdlib/qsort.c

   1 /*      $NetBSD: qsort.c,v 1.22 2012/05/26 21:47:05 christos Exp $      */
   2
   3 /*-
   4  * Copyright (c) 1992, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 #if 0
  35 static char sccsid[] = "@(#)qsort.c     8.1 (Berkeley) 6/4/93";
  36 #else
  37 __RCSID("$NetBSD: qsort.c,v 1.22 2012/05/26 21:47:05 christos Exp $");
  38 #endif
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include <sys/types.h>
  42
  43 #include <assert.h>
  44 #include <errno.h>
  45 #include <stdlib.h>
  46
  47 static inline char      *med3(char *, char *, char *,
  48     int (*)(const void *, const void *));
  49 static inline void       swapfunc(char *, char *, size_t, int);
  50
  51 #define min(a, b)       (a) < (b) ? a : b
  52
  53 /*
  54  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  55  */
  56 #define swapcode(TYPE, parmi, parmj, n) {               \
  57         size_t i = (n) / sizeof (TYPE);                 \
  58         TYPE *pi = (TYPE *)(void *)(parmi);             \
  59         TYPE *pj = (TYPE *)(void *)(parmj);             \
  60         do {                                            \
  61                 TYPE    t = *pi;                        \
  62                 *pi++ = *pj;                            \
  63                 *pj++ = t;                              \
  64         } while (--i > 0);                              \
  65 }
  66
  67 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  68         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  69
  70 static inline void
  71 swapfunc(char *a, char *b, size_t n, int swaptype)
  72 {
  73
  74         if (swaptype <= 1)
  75                 swapcode(long, a, b, n)
  76         else
  77                 swapcode(char, a, b, n)
  78 }
  79
  80 #define swap(a, b)                                              \
  81         if (swaptype == 0) {                                    \
  82                 long t = *(long *)(void *)(a);                  \
  83                 *(long *)(void *)(a) = *(long *)(void *)(b);    \
  84                 *(long *)(void *)(b) = t;                       \
  85         } else                                                  \
  86                 swapfunc(a, b, es, swaptype)
  87
  88 #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
  89
  90 static inline char *
  91 med3(char *a, char *b, char *c,
  92     int (*cmp)(const void *, const void *))
  93 {
  94
  95         return cmp(a, b) < 0 ?
  96                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
  97               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
  98 }
  99
 100 void
 101 qsort(void *a, size_t n, size_t es,
 102     int (*cmp)(const void *, const void *))
 103 {
 104         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 105         size_t d, r;
 106         int swaptype, cmp_result;
 107
 108         _DIAGASSERT(a != NULL || n == 0 || es == 0);
 109         _DIAGASSERT(cmp != NULL);
 110
 111 loop:   SWAPINIT(a, es);
 112         if (n < 7) {
 113                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 114                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 115                              pl -= es)
 116                                 swap(pl, pl - es);
 117                 return;
 118         }
 119         pm = (char *) a + (n / 2) * es;
 120         if (n > 7) {
 121                 pl = (char *) a;
 122                 pn = (char *) a + (n - 1) * es;
 123                 if (n > 40) {
 124                         d = (n / 8) * es;
 125                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
 126                         pm = med3(pm - d, pm, pm + d, cmp);
 127                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
 128                 }
 129                 pm = med3(pl, pm, pn, cmp);
 130         }
 131         swap(a, pm);
 132         pa = pb = (char *) a + es;
 133
 134         pc = pd = (char *) a + (n - 1) * es;
 135         for (;;) {
 136                 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
 137                         if (cmp_result == 0) {
 138                                 swap(pa, pb);
 139                                 pa += es;
 140                         }
 141                         pb += es;
 142                 }
 143                 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
 144                         if (cmp_result == 0) {
 145                                 swap(pc, pd);
 146                                 pd -= es;
 147                         }
 148                         pc -= es;
 149                 }
 150                 if (pb > pc)
 151                         break;
 152                 swap(pb, pc);
 153                 pb += es;
 154                 pc -= es;
 155         }
 156
 157         pn = (char *) a + n * es;
 158         r = min(pa - (char *) a, pb - pa);
 159         vecswap(a, pb - r, r);
 160         r = min((size_t)(pd - pc), pn - pd - es);
 161         vecswap(pb, pn - r, r);
 162         if ((r = pb - pa) > es)
 163                 qsort(a, r / es, es, cmp);
 164         if ((r = pd - pc) > es) {
 165                 /* Iterate rather than recurse to save stack space */
 166                 a = pn - r;
 167                 n = r / es;
 168                 goto loop;
 169         }
 170 /*              qsort(pn - r, r / es, es, cmp);*/
 171 }