lib/libc/stdlib/qsort.c

   1 /*-
   2  * Copyright (c) 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)qsort.c  8.1 (Berkeley) 6/4/93
  30  * $FreeBSD: src/lib/libc/stdlib/qsort.c,v 1.15 2008/01/14 09:21:34 das Exp $
  31  * $DragonFly: src/lib/libc/stdlib/qsort.c,v 1.5 2005/11/20 12:37:49 swildner Exp $
  32  */
  33
  34 #include <stdlib.h>
  35
  36 #ifdef I_AM_QSORT_R
  37 typedef int              cmp_t(void *, const void *, const void *);
  38 #else
  39 typedef int              cmp_t(const void *, const void *);
  40 #endif
  41 static inline char      *med3(char *, char *, char *, cmp_t *, void *);
  42 static inline void       swapfunc(char *, char *, int, int);
  43
  44 #define min(a, b)       (a) < (b) ? a : b
  45
  46 /*
  47  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  48  */
  49 #define swapcode(TYPE, parmi, parmj, n) {               \
  50         long i = (n) / sizeof (TYPE);                   \
  51         TYPE *pi = (TYPE *) (parmi);            \
  52         TYPE *pj = (TYPE *) (parmj);            \
  53         do {                                            \
  54                 TYPE    t = *pi;                \
  55                 *pi++ = *pj;                            \
  56                 *pj++ = t;                              \
  57         } while (--i > 0);                              \
  58 }
  59
  60 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  61         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  62
  63 static inline void
  64 swapfunc(char *a, char *b, int n, int swaptype)
  65 {
  66         if(swaptype <= 1)
  67                 swapcode(long, a, b, n)
  68         else
  69                 swapcode(char, a, b, n)
  70 }
  71
  72 #define swap(a, b)                                      \
  73         if (swaptype == 0) {                            \
  74                 long t = *(long *)(a);                  \
  75                 *(long *)(a) = *(long *)(b);            \
  76                 *(long *)(b) = t;                       \
  77         } else                                          \
  78                 swapfunc(a, b, es, swaptype)
  79
  80 #define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)
  81
  82 #ifdef I_AM_QSORT_R
  83 #define CMP(t, x, y) (cmp((t), (x), (y)))
  84 #else
  85 #define CMP(t, x, y) (cmp((x), (y)))
  86 #endif
  87
  88 static inline char *
  89 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
  90 #ifndef I_AM_QSORT_R
  91 __unused
  92 #endif
  93 )
  94 {
  95         return CMP(thunk, a, b) < 0 ?
  96                (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
  97               :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
  98 }
  99
 100 #ifdef I_AM_QSORT_R
 101 void
 102 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
 103 #else
 104 #define thunk NULL
 105 void
 106 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
 107 #endif
 108 {
 109         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 110         size_t d, r;
 111         int cmp_result;
 112         int swaptype, swap_cnt;
 113
 114 loop:   SWAPINIT(a, es);
 115         swap_cnt = 0;
 116         if (n < 7) {
 117                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 118                         for (pl = pm;
 119                              pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 120                              pl -= es)
 121                                 swap(pl, pl - es);
 122                 return;
 123         }
 124         pm = (char *)a + (n / 2) * es;
 125         if (n > 7) {
 126                 pl = a;
 127                 pn = (char *)a + (n - 1) * es;
 128                 if (n > 40) {
 129                         d = (n / 8) * es;
 130                         pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
 131                         pm = med3(pm - d, pm, pm + d, cmp, thunk);
 132                         pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
 133                 }
 134                 pm = med3(pl, pm, pn, cmp, thunk);
 135         }
 136         swap(a, pm);
 137         pa = pb = (char *)a + es;
 138
 139         pc = pd = (char *)a + (n - 1) * es;
 140         for (;;) {
 141                 while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
 142                         if (cmp_result == 0) {
 143                                 swap_cnt = 1;
 144                                 swap(pa, pb);
 145                                 pa += es;
 146                         }
 147                         pb += es;
 148                 }
 149                 while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
 150                         if (cmp_result == 0) {
 151                                 swap_cnt = 1;
 152                                 swap(pc, pd);
 153                                 pd -= es;
 154                         }
 155                         pc -= es;
 156                 }
 157                 if (pb > pc)
 158                         break;
 159                 swap(pb, pc);
 160                 swap_cnt = 1;
 161                 pb += es;
 162                 pc -= es;
 163         }
 164         if (swap_cnt == 0) {  /* Switch to insertion sort */
 165                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 166                         for (pl = pm;
 167                              pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 168                              pl -= es)
 169                                 swap(pl, pl - es);
 170                 return;
 171         }
 172
 173         pn = (char *)a + n * es;
 174         r = min(pa - (char *)a, pb - pa);
 175         vecswap(a, pb - r, r);
 176         r = min(pd - pc, pn - pd - es);
 177         vecswap(pb, pn - r, r);
 178         if ((r = pb - pa) > es)
 179 #ifdef I_AM_QSORT_R
 180                 qsort_r(a, r / es, es, thunk, cmp);
 181 #else
 182                 qsort(a, r / es, es, cmp);
 183 #endif
 184         if ((r = pd - pc) > es) {
 185                 /* Iterate rather than recurse to save stack space */
 186                 a = pn - r;
 187                 n = r / es;
 188                 goto loop;
 189         }
 190 /*              qsort(pn - r, r / es, es, cmp);*/
 191 }