The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/libkern/qsort.c

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    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  * $FreeBSD: src/sys/libkern/qsort.c,v 1.12 2002/11/09 12:55:06 alfred Exp $
   34  */
   35 
   36 #include <sys/libkern.h>
   37 
   38 typedef int              cmp_t(const void *, const void *);
   39 static __inline char    *med3(char *, char *, char *, cmp_t *);
   40 static __inline void     swapfunc(char *, char *, int, int);
   41 
   42 #define min(a, b)       (a) < (b) ? (a) : (b)
   43 
   44 /*
   45  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
   46  */
   47 #define swapcode(TYPE, parmi, parmj, n) {               \
   48         long i = (n) / sizeof (TYPE);                   \
   49         register TYPE *pi = (TYPE *) (parmi);           \
   50         register TYPE *pj = (TYPE *) (parmj);           \
   51         do {                                            \
   52                 register TYPE   t = *pi;                \
   53                 *pi++ = *pj;                            \
   54                 *pj++ = t;                              \
   55         } while (--i > 0);                              \
   56 }
   57 
   58 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
   59         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
   60 
   61 static __inline void
   62 swapfunc(a, b, n, swaptype)
   63         char *a, *b;
   64         int n, 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 char *
   83 med3(a, b, c, cmp)
   84         char *a, *b, *c;
   85         cmp_t *cmp;
   86 {
   87         return cmp(a, b) < 0 ?
   88                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
   89               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
   90 }
   91 
   92 void
   93 qsort(a, n, es, cmp)
   94         void *a;
   95         size_t n, es;
   96         cmp_t *cmp;
   97 {
   98         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
   99         int d, r, swaptype, swap_cnt;
  100 
  101 loop:   SWAPINIT(a, es);
  102         swap_cnt = 0;
  103         if (n < 7) {
  104                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
  105                         for (pl = pm; pl > (char *)a && cmp(pl - es, pl) > 0;
  106                              pl -= es)
  107                                 swap(pl, pl - es);
  108                 return;
  109         }
  110         pm = (char *)a + (n / 2) * es;
  111         if (n > 7) {
  112                 pl = a;
  113                 pn = (char *)a + (n - 1) * es;
  114                 if (n > 40) {
  115                         d = (n / 8) * es;
  116                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
  117                         pm = med3(pm - d, pm, pm + d, cmp);
  118                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
  119                 }
  120                 pm = med3(pl, pm, pn, cmp);
  121         }
  122         swap(a, pm);
  123         pa = pb = (char *)a + es;
  124 
  125         pc = pd = (char *)a + (n - 1) * es;
  126         for (;;) {
  127                 while (pb <= pc && (r = cmp(pb, a)) <= 0) {
  128                         if (r == 0) {
  129                                 swap_cnt = 1;
  130                                 swap(pa, pb);
  131                                 pa += es;
  132                         }
  133                         pb += es;
  134                 }
  135                 while (pb <= pc && (r = cmp(pc, a)) >= 0) {
  136                         if (r == 0) {
  137                                 swap_cnt = 1;
  138                                 swap(pc, pd);
  139                                 pd -= es;
  140                         }
  141                         pc -= es;
  142                 }
  143                 if (pb > pc)
  144                         break;
  145                 swap(pb, pc);
  146                 swap_cnt = 1;
  147                 pb += es;
  148                 pc -= es;
  149         }
  150         if (swap_cnt == 0) {  /* Switch to insertion sort */
  151                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
  152                         for (pl = pm; pl > (char *)a && cmp(pl - es, pl) > 0;
  153                              pl -= es)
  154                                 swap(pl, pl - es);
  155                 return;
  156         }
  157 
  158         pn = (char *)a + n * es;
  159         r = min(pa - (char *)a, pb - pa);
  160         vecswap(a, pb - r, r);
  161         r = min(pd - pc, pn - pd - es);
  162         vecswap(pb, pn - r, r);
  163         if ((r = pb - pa) > es)
  164                 qsort(a, r / es, es, cmp);
  165         if ((r = pd - pc) > es) {
  166                 /* Iterate rather than recurse to save stack space */
  167                 a = pn - r;
  168                 n = r / es;
  169                 goto loop;
  170         }
  171 /*              qsort(pn - r, r / es, es, cmp);*/
  172 }

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