src/system/libroot/posix/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  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34
  35 #include <stdlib.h>
  36
  37 #define min(a, b)       (a) < (b) ? a : b
  38
  39
  40 typedef int              cmp_t(void const *, void const *);
  41 static inline char      *med3(char *, char *, char *, cmp_t *);
  42 static inline void       swapfunc(char *, char *, int, int);
  43
  44
  45 /*
  46  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  47  */
  48 #define swapcode(TYPE, parmi, parmj, n) {               \
  49         long i = (n) / sizeof (TYPE);                   \
  50         register TYPE *pi = (TYPE *) (parmi);           \
  51         register TYPE *pj = (TYPE *) (parmj);           \
  52         do {                                            \
  53                 register TYPE   t = *pi;                \
  54                 *pi++ = *pj;                            \
  55                 *pj++ = t;                              \
  56         } while (--i > 0);                              \
  57 }
  58
  59 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  60         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  61
  62 static inline
  63 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 static inline
  83 char *
  84 med3(char *a, char *b, char *c, cmp_t *cmp)
  85 {
  86         return cmp(a, b) < 0 ?
  87                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
  88               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
  89 }
  90
  91 void
  92 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
  93 {
  94         char *pa;
  95         char *pb;
  96         char *pc;
  97         char *pd;
  98         char *pl;
  99         char *pm;
 100         char *pn;
 101         int d;
 102         int r;
 103         int swaptype;
 104         int swap_cnt;
 105
 106 loop:   SWAPINIT(a, es);
 107         swap_cnt = 0;
 108         if (n < 7) {
 109                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 110                         for (pl = pm; pl > (char *)a && cmp(pl - es, pl) > 0;
 111                              pl -= es)
 112                                 swap(pl, pl - es);
 113                 return;
 114         }
 115         pm = (char *)a + (n / 2) * es;
 116         if (n > 7) {
 117                 pl = a;
 118                 pn = (char *)a + (n - 1) * es;
 119                 if (n > 40) {
 120                         d = (n / 8) * es;
 121                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
 122                         pm = med3(pm - d, pm, pm + d, cmp);
 123                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
 124                 }
 125                 pm = med3(pl, pm, pn, cmp);
 126         }
 127         swap(a, pm);
 128         pa = pb = (char *)a + es;
 129
 130         pc = pd = (char *)a + (n - 1) * es;
 131         for (;;) {
 132                 while (pb <= pc && (r = cmp(pb, a)) <= 0) {
 133                         if (r == 0) {
 134                                 swap_cnt = 1;
 135                                 swap(pa, pb);
 136                                 pa += es;
 137                         }
 138                         pb += es;
 139                 }
 140                 while (pb <= pc && (r = cmp(pc, a)) >= 0) {
 141                         if (r == 0) {
 142                                 swap_cnt = 1;
 143                                 swap(pc, pd);
 144                                 pd -= es;
 145                         }
 146                         pc -= es;
 147                 }
 148                 if (pb > pc)
 149                         break;
 150                 swap(pb, pc);
 151                 swap_cnt = 1;
 152                 pb += es;
 153                 pc -= es;
 154         }
 155         if (swap_cnt == 0) {  /* Switch to insertion sort */
 156                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 157                         for (pl = pm; pl > (char *)a && cmp(pl - es, pl) > 0;
 158                              pl -= es)
 159                                 swap(pl, pl - es);
 160                 return;
 161         }
 162
 163         pn = (char *)a + n * es;
 164         r = min(pa - (char *)a, pb - pa);
 165         vecswap(a, pb - r, r);
 166         r = min((int)(pd - pc), (int)(pn - pd - es));
 167         vecswap(pb, pn - r, r);
 168         if ((r = pb - pa) > (int)es)
 169                 qsort(a, r / es, es, cmp);
 170         if ((r = pd - pc) > (int)es) {
 171                 /* Iterate rather than recurse to save stack space */
 172                 a = pn - r;
 173                 n = r / es;
 174                 goto loop;
 175         }
 176 /*              qsort(pn - r, r / es, es, cmp);*/
 177 }