stdlib/FreeBSD/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 #if defined(LIBC_SCCS) && !defined(lint)
  35 static char sccsid[] = "@(#)qsort.c     8.1 (Berkeley) 6/4/93";
  36 #endif /* LIBC_SCCS and not lint */
  37 #include <sys/cdefs.h>
  38 __FBSDID("$FreeBSD: src/lib/libc/stdlib/qsort.c,v 1.12 2002/09/10 02:04:49 wollman Exp $");
  39
  40 #include <stdlib.h>
  41
  42 #ifdef I_AM_QSORT_R
  43 typedef int              cmp_t(void *, const void *, const void *);
  44 #else
  45 typedef int              cmp_t(const void *, const void *);
  46 #endif
  47 static inline char      *med3(char *, char *, char *, cmp_t *, void *);
  48 static inline void       swapfunc(char *, char *, int, int);
  49
  50 #define min(a, b)       (a) < (b) ? a : b
  51
  52 /*
  53  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  54  */
  55 #define swapcode(TYPE, parmi, parmj, n) {               \
  56         long i = (n) / sizeof (TYPE);                   \
  57         TYPE *pi = (TYPE *) (parmi);            \
  58         TYPE *pj = (TYPE *) (parmj);            \
  59         do {                                            \
  60                 TYPE    t = *pi;                \
  61                 *pi++ = *pj;                            \
  62                 *pj++ = t;                              \
  63         } while (--i > 0);                              \
  64 }
  65
  66 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  67         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  68
  69 static inline void
  70 swapfunc(a, b, n, swaptype)
  71         char *a, *b;
  72         int n, swaptype;
  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 *)(a);                  \
  83                 *(long *)(a) = *(long *)(b);            \
  84                 *(long *)(b) = t;                       \
  85         } else                                          \
  86                 swapfunc(a, b, es, swaptype)
  87
  88 #define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)
  89
  90 #ifdef I_AM_QSORT_R
  91 #define CMP(t, x, y) (cmp((t), (x), (y)))
  92 #else
  93 #define CMP(t, x, y) (cmp((x), (y)))
  94 #endif
  95
  96 static inline char *
  97 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
  98 #ifndef I_AM_QSORT_R
  99 __unused
 100 #endif
 101 )
 102 {
 103         return CMP(thunk, a, b) < 0 ?
 104                (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
 105               :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
 106 }
 107
 108 #ifdef I_AM_QSORT_R
 109 void
 110 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
 111 #else
 112 #define thunk NULL
 113 void
 114 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
 115 #endif
 116 {
 117         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 118         int d, r, swaptype, swap_cnt;
 119
 120 loop:   SWAPINIT(a, es);
 121         swap_cnt = 0;
 122         if (n < 7) {
 123                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 124                         for (pl = pm;
 125                              pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 126                              pl -= es)
 127                                 swap(pl, pl - es);
 128                 return;
 129         }
 130         pm = (char *)a + (n / 2) * es;
 131         if (n > 7) {
 132                 pl = a;
 133                 pn = (char *)a + (n - 1) * es;
 134                 if (n > 40) {
 135                         d = (n / 8) * es;
 136                         pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
 137                         pm = med3(pm - d, pm, pm + d, cmp, thunk);
 138                         pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
 139                 }
 140                 pm = med3(pl, pm, pn, cmp, thunk);
 141         }
 142         swap(a, pm);
 143         pa = pb = (char *)a + es;
 144
 145         pc = pd = (char *)a + (n - 1) * es;
 146         for (;;) {
 147                 while (pb <= pc && (r = CMP(thunk, pb, a)) <= 0) {
 148                         if (r == 0) {
 149                                 swap_cnt = 1;
 150                                 swap(pa, pb);
 151                                 pa += es;
 152                         }
 153                         pb += es;
 154                 }
 155                 while (pb <= pc && (r = CMP(thunk, pc, a)) >= 0) {
 156                         if (r == 0) {
 157                                 swap_cnt = 1;
 158                                 swap(pc, pd);
 159                                 pd -= es;
 160                         }
 161                         pc -= es;
 162                 }
 163                 if (pb > pc)
 164                         break;
 165                 swap(pb, pc);
 166                 swap_cnt = 1;
 167                 pb += es;
 168                 pc -= es;
 169         }
 170         if (swap_cnt == 0) {  /* Switch to insertion sort */
 171                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 172                         for (pl = pm;
 173                              pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 174                              pl -= es)
 175                                 swap(pl, pl - es);
 176                 return;
 177         }
 178
 179         pn = (char *)a + n * es;
 180         r = min(pa - (char *)a, pb - pa);
 181         vecswap(a, pb - r, r);
 182         r = min(pd - pc, pn - pd - es);
 183         vecswap(pb, pn - r, r);
 184         if ((r = pb - pa) > es)
 185 #ifdef I_AM_QSORT_R
 186                 qsort_r(a, r / es, es, thunk, cmp);
 187 #else
 188                 qsort(a, r / es, es, cmp);
 189 #endif
 190         if ((r = pd - pc) > es) {
 191                 /* Iterate rather than recurse to save stack space */
 192                 a = pn - r;
 193                 n = r / es;
 194                 goto loop;
 195         }
 196 /*              qsort(pn - r, r / es, es, cmp);*/
 197 }