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. 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 }

Cache object: d7c54260b59a37d8b4442171b6fdec89


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