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/lib/libsa/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  * $NetBSD: qsort.c,v 1.1.2.2 2004/05/22 17:12:43 he Exp $
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 #include <sys/types.h>
   39 
   40 typedef int              cmp_t(const void *, const void *);
   41 static __inline char    *med3(char *, char *, char *, cmp_t *);
   42 static __inline void     swapfunc(char *, char *, int, int);
   43 
   44 #define min(a, b)       (a) < (b) ? (a) : (b)
   45 
   46 void qsort(void *a, size_t n, size_t es, cmp_t *cmp);
   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         register TYPE *pi = (TYPE *) (parmi);           \
   54         register TYPE *pj = (TYPE *) (parmj);           \
   55         do {                                            \
   56                 register 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 static __inline char *
   87 med3(a, b, c, cmp)
   88         char *a, *b, *c;
   89         cmp_t *cmp;
   90 {
   91         return cmp(a, b) < 0 ?
   92                (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
   93               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
   94 }
   95 
   96 void
   97 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
   98 {
   99         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
  100         int d, r, swaptype, swap_cnt;
  101 
  102 loop:   SWAPINIT(a, es);
  103         swap_cnt = 0;
  104         if (n < 7) {
  105                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
  106                         for (pl = pm; pl > (char *)a && cmp(pl - es, pl) > 0;
  107                              pl -= es)
  108                                 swap(pl, pl - es);
  109                 return;
  110         }
  111         pm = (char *)a + (n / 2) * es;
  112         if (n > 7) {
  113                 pl = a;
  114                 pn = (char *)a + (n - 1) * es;
  115                 if (n > 40) {
  116                         d = (n / 8) * es;
  117                         pl = med3(pl, pl + d, pl + 2 * d, cmp);
  118                         pm = med3(pm - d, pm, pm + d, cmp);
  119                         pn = med3(pn - 2 * d, pn - d, pn, cmp);
  120                 }
  121                 pm = med3(pl, pm, pn, cmp);
  122         }
  123         swap(a, pm);
  124         pa = pb = (char *)a + es;
  125 
  126         pc = pd = (char *)a + (n - 1) * es;
  127         for (;;) {
  128                 while (pb <= pc && (r = cmp(pb, a)) <= 0) {
  129                         if (r == 0) {
  130                                 swap_cnt = 1;
  131                                 swap(pa, pb);
  132                                 pa += es;
  133                         }
  134                         pb += es;
  135                 }
  136                 while (pb <= pc && (r = cmp(pc, a)) >= 0) {
  137                         if (r == 0) {
  138                                 swap_cnt = 1;
  139                                 swap(pc, pd);
  140                                 pd -= es;
  141                         }
  142                         pc -= es;
  143                 }
  144                 if (pb > pc)
  145                         break;
  146                 swap(pb, pc);
  147                 swap_cnt = 1;
  148                 pb += es;
  149                 pc -= es;
  150         }
  151         if (swap_cnt == 0) {  /* Switch to insertion sort */
  152                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
  153                         for (pl = pm; pl > (char *)a && cmp(pl - es, pl) > 0;
  154                              pl -= es)
  155                                 swap(pl, pl - es);
  156                 return;
  157         }
  158 
  159         pn = (char *)a + n * es;
  160         r = min(pa - (char *)a, pb - pa);
  161         vecswap(a, pb - r, r);
  162         r = min(pd - pc, pn - pd - es);
  163         vecswap(pb, pn - r, r);
  164         if ((r = pb - pa) > es)
  165                 qsort(a, r / es, es, cmp);
  166         if ((r = pd - pc) > es) {
  167                 /* Iterate rather than recurse to save stack space */
  168                 a = pn - r;
  169                 n = r / es;
  170                 goto loop;
  171         }
  172 /*              qsort(pn - r, r / es, es, cmp);*/
  173 }

Cache object: fc59c9ff9c2e23fb5038a2b1793b33d5


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