sys/libkern/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. 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  * $FreeBSD: src/sys/libkern/qsort.c,v 1.15 2004/07/15 23:58:23 glebius Exp $
  30  */
  31
  32 #include <sys/param.h>
  33 #include <sys/libkern.h>
  34
  35 #ifdef  I_AM_KQSORT_R
  36 typedef int             cmp_t(void *, const void *, const void *);
  37 #else
  38 typedef int             cmp_t(const void *, const void *);
  39 #endif
  40 static __inline char    *med3(char *, char *, char *, cmp_t *, void *);
  41 static __inline void     swapfunc(char *, char *, int, int);
  42
  43 #define min(a, b)       (a) < (b) ? (a) : (b)
  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         TYPE *pi = (TYPE *) (parmi);            \
  51         TYPE *pj = (TYPE *) (parmj);            \
  52         do {                                            \
  53                 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 void
  63 swapfunc(char *a, char *b, int n, int swaptype)
  64 {
  65         if(swaptype <= 1)
  66                 swapcode(long, a, b, n)
  67         else
  68                 swapcode(char, a, b, n)
  69 }
  70
  71 #define swap(a, b)                                      \
  72         if (swaptype == 0) {                            \
  73                 long t = *(long *)(a);                  \
  74                 *(long *)(a) = *(long *)(b);            \
  75                 *(long *)(b) = t;                       \
  76         } else                                          \
  77                 swapfunc(a, b, es, swaptype)
  78
  79 #define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)
  80
  81 #ifdef I_AM_KQSORT_R
  82 #define CMP(t, x, y) (cmp((t), (x), (y)))
  83 #else
  84 #define CMP(t, x, y) (cmp((x), (y)))
  85 #endif
  86
  87 static __inline char *
  88 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
  89 #ifndef I_AM_KQSORT_R
  90 __unused
  91 #endif
  92 )
  93 {
  94         return CMP(thunk, a, b) < 0 ?
  95                (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
  96               :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
  97 }
  98
  99 #ifdef I_AM_KQSORT_R
 100 void
 101 kqsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
 102 #else
 103 #define thunk NULL
 104 void
 105 kqsort(void *a, size_t n, size_t es, cmp_t *cmp)
 106 #endif
 107 {
 108         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
 109         int d, r, swaptype, swap_cnt;
 110
 111 loop:   SWAPINIT(a, es);
 112         swap_cnt = 0;
 113         if (n < 7) {
 114                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 115                         for (pl = pm; pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 116                              pl -= es)
 117                                 swap(pl, pl - es);
 118                 return;
 119         }
 120         pm = (char *)a + (n / 2) * es;
 121         if (n > 7) {
 122                 pl = a;
 123                 pn = (char *)a + (n - 1) * es;
 124                 if (n > 40) {
 125                         d = (n / 8) * es;
 126                         pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
 127                         pm = med3(pm - d, pm, pm + d, cmp, thunk);
 128                         pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
 129                 }
 130                 pm = med3(pl, pm, pn, cmp, thunk);
 131         }
 132         swap(a, pm);
 133         pa = pb = (char *)a + es;
 134
 135         pc = pd = (char *)a + (n - 1) * es;
 136         for (;;) {
 137                 while (pb <= pc && (r = CMP(thunk, pb, a)) <= 0) {
 138                         if (r == 0) {
 139                                 swap_cnt = 1;
 140                                 swap(pa, pb);
 141                                 pa += es;
 142                         }
 143                         pb += es;
 144                 }
 145                 while (pb <= pc && (r = CMP(thunk, pc, a)) >= 0) {
 146                         if (r == 0) {
 147                                 swap_cnt = 1;
 148                                 swap(pc, pd);
 149                                 pd -= es;
 150                         }
 151                         pc -= es;
 152                 }
 153                 if (pb > pc)
 154                         break;
 155                 swap(pb, pc);
 156                 swap_cnt = 1;
 157                 pb += es;
 158                 pc -= es;
 159         }
 160         if (swap_cnt == 0) {  /* Switch to insertion sort */
 161                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
 162                         for (pl = pm; pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
 163                              pl -= es)
 164                                 swap(pl, pl - es);
 165                 return;
 166         }
 167
 168         pn = (char *)a + n * es;
 169         r = min(pa - (char *)a, pb - pa);
 170         vecswap(a, pb - r, r);
 171         r = min(pd - pc, pn - pd - es);
 172         vecswap(pb, pn - r, r);
 173         if ((r = pb - pa) > es)
 174 #ifdef  I_AM_KQSORT_R
 175                 kqsort_r(a, r / es, es, thunk, cmp);
 176 #else
 177                 kqsort(a, r / es, es, cmp);
 178 #endif
 179         if ((r = pd - pc) > es) {
 180                 /* Iterate rather than recurse to save stack space */
 181                 a = pn - r;
 182                 n = r / es;
 183                 goto loop;
 184         }
 185 }