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  * 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
  30 #if defined(LIBC_SCCS) && !defined(lint)
  31 static char sccsid[] = "@(#)qsort.c     8.1 (Berkeley) 6/4/93";
  32 #endif /* LIBC_SCCS and not lint */
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD: src/lib/libc/stdlib/qsort.c,v 1.15 2008/01/14 09:21:34 das Exp $");
  35
  36 #include <stdlib.h>
  37
  38 #ifdef I_AM_QSORT_R
  39 typedef int              cmp_t(void *, const void *, const void *);
  40 #else
  41 typedef int              cmp_t(const void *, const void *);
  42 #endif
  43 static inline char      *med3(char *, char *, char *, cmp_t *, void *);
  44 static inline void       swapfunc(char *, char *, int, int);
  45
  46 #define min(a, b)       (a) < (b) ? a : b
  47
  48 /*
  49  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  50  */
  51 #define swapcode(TYPE, parmi, parmj, n) {               \
  52         long i = (n) / sizeof (TYPE);                   \
  53         TYPE *pi = (TYPE *) (parmi);            \
  54         TYPE *pj = (TYPE *) (parmj);            \
  55         do {                                            \
  56                 TYPE    t = *pi;                \
  57                 *pi++ = *pj;                            \
  58                 *pj++ = t;                              \
  59         } while (--i > 0);                              \
  60 }
  61
  62 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  63         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  64
  65 static inline void
  66 swapfunc(a, b, n, swaptype)
  67         char *a, *b;
  68         int n, swaptype;
  69 {
  70         if(swaptype <= 1)
  71                 swapcode(long, a, b, n)
  72         else
  73                 swapcode(char, a, b, n)
  74 }
  75
  76 #define swap(a, b)                                      \
  77         if (swaptype == 0) {                            \
  78                 long t = *(long *)(a);                  \
  79                 *(long *)(a) = *(long *)(b);            \
  80                 *(long *)(b) = t;                       \
  81         } else                                          \
  82                 swapfunc(a, b, es, swaptype)
  83
  84 #define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)
  85
  86 #ifdef I_AM_QSORT_R
  87 #define CMP(t, x, y) (cmp((t), (x), (y)))
  88 #else
  89 #define CMP(t, x, y) (cmp((x), (y)))
  90 #endif
  91
  92 static inline char *
  93 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
  94 #ifndef I_AM_QSORT_R
  95 __unused
  96 #endif
  97 )
  98 {
  99         return CMP(thunk, a, b) < 0 ?
 100                (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
 101               :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
 102 }
 103
 104 #ifdef I_AM_QSORT_R
 105 void
 106 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
 107 #else
 108 #define thunk NULL
 109 void
 110 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
 111 #endif
 112 {
 113         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 114         size_t d, r;
 115         int cmp_result;
 116         int swaptype, swap_cnt;
 117
 118 loop:   SWAPINIT(a, es);
 119         swap_cnt = 0;
 120         if (n < 7) {
 121                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 122                         for (pl = pm;
 123                              pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 124                              pl -= es)
 125                                 swap(pl, pl - es);
 126                 return;
 127         }
 128         pm = (char *)a + (n / 2) * es;
 129         if (n > 7) {
 130                 pl = a;
 131                 pn = (char *)a + (n - 1) * es;
 132                 if (n > 40) {
 133                         d = (n / 8) * es;
 134                         pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
 135                         pm = med3(pm - d, pm, pm + d, cmp, thunk);
 136                         pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
 137                 }
 138                 pm = med3(pl, pm, pn, cmp, thunk);
 139         }
 140         swap(a, pm);
 141         pa = pb = (char *)a + es;
 142
 143         pc = pd = (char *)a + (n - 1) * es;
 144         for (;;) {
 145                 while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
 146                         if (cmp_result == 0) {
 147                                 swap_cnt = 1;
 148                                 swap(pa, pb);
 149                                 pa += es;
 150                         }
 151                         pb += es;
 152                 }
 153                 while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
 154                         if (cmp_result == 0) {
 155                                 swap_cnt = 1;
 156                                 swap(pc, pd);
 157                                 pd -= es;
 158                         }
 159                         pc -= es;
 160                 }
 161                 if (pb > pc)
 162                         break;
 163                 swap(pb, pc);
 164                 swap_cnt = 1;
 165                 pb += es;
 166                 pc -= es;
 167         }
 168         if (swap_cnt == 0) {  /* Switch to insertion sort */
 169                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 170                         for (pl = pm;
 171                              pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 172                              pl -= es)
 173                                 swap(pl, pl - es);
 174                 return;
 175         }
 176
 177         pn = (char *)a + n * es;
 178         r = min(pa - (char *)a, pb - pa);
 179         vecswap(a, pb - r, r);
 180         r = min(pd - pc, pn - pd - es);
 181         vecswap(pb, pn - r, r);
 182         if ((r = pb - pa) > es)
 183 #ifdef I_AM_QSORT_R
 184                 qsort_r(a, r / es, es, thunk, cmp);
 185 #else
 186                 qsort(a, r / es, es, cmp);
 187 #endif
 188         if ((r = pd - pc) > es) {
 189                 /* Iterate rather than recurse to save stack space */
 190                 a = pn - r;
 191                 n = r / es;
 192                 goto loop;
 193         }
 194 /*              qsort(pn - r, r / es, es, cmp);*/
 195 }