fs/xfs/support/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
  30 #include <linux/kernel.h>
  31 #include <linux/string.h>
  32
  33 /*
  34  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  35  */
  36 #define swapcode(TYPE, parmi, parmj, n) {               \
  37         long i = (n) / sizeof (TYPE);                   \
  38         register TYPE *pi = (TYPE *) (parmi);           \
  39         register TYPE *pj = (TYPE *) (parmj);           \
  40         do {                                            \
  41                 register TYPE   t = *pi;                \
  42                 *pi++ = *pj;                            \
  43                 *pj++ = t;                              \
  44         } while (--i > 0);                              \
  45 }
  46
  47 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
  48         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
  49
  50 static __inline void
  51 swapfunc(char *a, char *b, int n, int swaptype)
  52 {
  53         if (swaptype <= 1)
  54                 swapcode(long, a, b, n)
  55         else
  56                 swapcode(char, a, b, n)
  57 }
  58
  59 #define swap(a, b)                                      \
  60         if (swaptype == 0) {                            \
  61                 long t = *(long *)(a);                  \
  62                 *(long *)(a) = *(long *)(b);            \
  63                 *(long *)(b) = t;                       \
  64         } else                                          \
  65                 swapfunc(a, b, es, swaptype)
  66
  67 #define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)
  68
  69 static __inline char *
  70 med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *))
  71 {
  72         return cmp(a, b) < 0 ?
  73                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
  74               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
  75 }
  76
  77 void
  78 qsort(void *aa, size_t n, size_t es, int (*cmp)(const void *, const void *))
  79 {
  80         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
  81         int d, r, swaptype, swap_cnt;
  82         register char *a = aa;
  83
  84 loop:   SWAPINIT(a, es);
  85         swap_cnt = 0;
  86         if (n < 7) {
  87                 for (pm = (char *)a + es; pm < (char *) a + n * es; pm += es)
  88                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
  89                              pl -= es)
  90                                 swap(pl, pl - es);
  91                 return;
  92         }
  93         pm = (char *)a + (n / 2) * es;
  94         if (n > 7) {
  95                 pl = (char *)a;
  96                 pn = (char *)a + (n - 1) * es;
  97                 if (n > 40) {
  98                         d = (n / 8) * es;
  99                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
 100                         pm = med3(pm - d, pm, pm + d, cmp);
 101                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
 102                 }
 103                 pm = med3(pl, pm, pn, cmp);
 104         }
 105         swap(a, pm);
 106         pa = pb = (char *)a + es;
 107
 108         pc = pd = (char *)a + (n - 1) * es;
 109         for (;;) {
 110                 while (pb <= pc && (r = cmp(pb, a)) <= 0) {
 111                         if (r == 0) {
 112                                 swap_cnt = 1;
 113                                 swap(pa, pb);
 114                                 pa += es;
 115                         }
 116                         pb += es;
 117                 }
 118                 while (pb <= pc && (r = cmp(pc, a)) >= 0) {
 119                         if (r == 0) {
 120                                 swap_cnt = 1;
 121                                 swap(pc, pd);
 122                                 pd -= es;
 123                         }
 124                         pc -= es;
 125                 }
 126                 if (pb > pc)
 127                         break;
 128                 swap(pb, pc);
 129                 swap_cnt = 1;
 130                 pb += es;
 131                 pc -= es;
 132         }
 133         if (swap_cnt == 0) {  /* Switch to insertion sort */
 134                 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
 135                         for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
 136                              pl -= es)
 137                                 swap(pl, pl - es);
 138                 return;
 139         }
 140
 141         pn = (char *)a + n * es;
 142         r = min(pa - (char *)a, pb - pa);
 143         vecswap(a, pb - r, r);
 144         r = min((long)(pd - pc), (long)(pn - pd - es));
 145         vecswap(pb, pn - r, r);
 146         if ((r = pb - pa) > es)
 147                 qsort(a, r / es, es, cmp);
 148         if ((r = pd - pc) > es) {
 149                 /* Iterate rather than recurse to save stack space */
 150                 a = pn - r;
 151                 n = r / es;
 152                 goto loop;
 153         }
 154 /*              qsort(pn - r, r / es, es, cmp);*/
 155 }