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  * 4. 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 <sys/cdefs.h>
   31 __FBSDID("$FreeBSD: releng/6.1/sys/libkern/qsort.c 132228 2004-07-15 23:58:23Z glebius $");
   32 
   33 #include <sys/param.h>
   34 #include <sys/libkern.h>
   35 
   36 #ifdef  I_AM_QSORT_R
   37 typedef int             cmp_t(void *, const void *, const void *);
   38 #else
   39 typedef int             cmp_t(const void *, const void *);
   40 #endif
   41 static __inline char    *med3(char *, char *, char *, cmp_t *, void *);
   42 static __inline void     swapfunc(char *, char *, int, int);
   43 
   44 #define min(a, b)       (a) < (b) ? (a) : (b)
   45 
   46 /*
   47  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
   48  */
   49 #define swapcode(TYPE, parmi, parmj, n) {               \
   50         long i = (n) / sizeof (TYPE);                   \
   51         register TYPE *pi = (TYPE *) (parmi);           \
   52         register TYPE *pj = (TYPE *) (parmj);           \
   53         do {                                            \
   54                 register TYPE   t = *pi;                \
   55                 *pi++ = *pj;                            \
   56                 *pj++ = t;                              \
   57         } while (--i > 0);                              \
   58 }
   59 
   60 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
   61         es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
   62 
   63 static __inline void
   64 swapfunc(char *a, char *b, int n, int 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 #ifdef I_AM_QSORT_R
   83 #define CMP(t, x, y) (cmp((t), (x), (y)))
   84 #else
   85 #define CMP(t, x, y) (cmp((x), (y)))
   86 #endif
   87 
   88 static __inline char *
   89 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
   90 #ifndef I_AM_QSORT_R
   91 __unused
   92 #endif
   93 )
   94 {
   95         return CMP(thunk, a, b) < 0 ?
   96                (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
   97               :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
   98 }
   99 
  100 #ifdef I_AM_QSORT_R
  101 void
  102 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
  103 #else
  104 #define thunk NULL
  105 void
  106 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
  107 #endif
  108 {
  109         char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
  110         int d, r, swaptype, swap_cnt;
  111 
  112 loop:   SWAPINIT(a, es);
  113         swap_cnt = 0;
  114         if (n < 7) {
  115                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
  116                         for (pl = pm; pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
  117                              pl -= es)
  118                                 swap(pl, pl - es);
  119                 return;
  120         }
  121         pm = (char *)a + (n / 2) * es;
  122         if (n > 7) {
  123                 pl = a;
  124                 pn = (char *)a + (n - 1) * es;
  125                 if (n > 40) {
  126                         d = (n / 8) * es;
  127                         pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
  128                         pm = med3(pm - d, pm, pm + d, cmp, thunk);
  129                         pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
  130                 }
  131                 pm = med3(pl, pm, pn, cmp, thunk);
  132         }
  133         swap(a, pm);
  134         pa = pb = (char *)a + es;
  135 
  136         pc = pd = (char *)a + (n - 1) * es;
  137         for (;;) {
  138                 while (pb <= pc && (r = CMP(thunk, pb, a)) <= 0) {
  139                         if (r == 0) {
  140                                 swap_cnt = 1;
  141                                 swap(pa, pb);
  142                                 pa += es;
  143                         }
  144                         pb += es;
  145                 }
  146                 while (pb <= pc && (r = CMP(thunk, pc, a)) >= 0) {
  147                         if (r == 0) {
  148                                 swap_cnt = 1;
  149                                 swap(pc, pd);
  150                                 pd -= es;
  151                         }
  152                         pc -= es;
  153                 }
  154                 if (pb > pc)
  155                         break;
  156                 swap(pb, pc);
  157                 swap_cnt = 1;
  158                 pb += es;
  159                 pc -= es;
  160         }
  161         if (swap_cnt == 0) {  /* Switch to insertion sort */
  162                 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
  163                         for (pl = pm; pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
  164                              pl -= es)
  165                                 swap(pl, pl - es);
  166                 return;
  167         }
  168 
  169         pn = (char *)a + n * es;
  170         r = min(pa - (char *)a, pb - pa);
  171         vecswap(a, pb - r, r);
  172         r = min(pd - pc, pn - pd - es);
  173         vecswap(pb, pn - r, r);
  174         if ((r = pb - pa) > es)
  175 #ifdef  I_AM_QSORT_R
  176                 qsort_r(a, r / es, es, thunk, cmp);
  177 #else
  178                 qsort(a, r / es, es, cmp);
  179 #endif
  180         if ((r = pd - pc) > es) {
  181                 /* Iterate rather than recurse to save stack space */
  182                 a = pn - r;
  183                 n = r / es;
  184                 goto loop;
  185         }
  186 }

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