rockbox/firmware/libc/qsort.c

/*
FUNCTION
<<qsort>>---sort an array

INDEX
        qsort

ANSI_SYNOPSIS
        #include <stdlib.h>
        void qsort(void *<[base]>, size_t <[nmemb]>, size_t <[size]>,
                   int (*<[compar]>)(const void *, const void *) );

TRAD_SYNOPSIS
        #include <stdlib.h>
        qsort(<[base]>, <[nmemb]>, <[size]>, <[compar]> )
        char *<[base]>;
        size_t <[nmemb]>;
        size_t <[size]>;
        int (*<[compar]>)();

DESCRIPTION
<<qsort>> sorts an array (beginning at <[base]>) of <[nmemb]> objects.
<[size]> describes the size of each element of the array.

You must supply a pointer to a comparison function, using the argument
shown as <[compar]>.  (This permits sorting objects of unknown
properties.)  Define the comparison function to accept two arguments,
each a pointer to an element of the array starting at <[base]>.  The
result of <<(*<[compar]>)>> must be negative if the first argument is
less than the second, zero if the two arguments match, and positive if
the first argument is greater than the second (where ``less than'' and
``greater than'' refer to whatever arbitrary ordering is appropriate).

The array is sorted in place; that is, when <<qsort>> returns, the
array elements beginning at <[base]> have been reordered.

RETURNS
<<qsort>> does not return a result.

PORTABILITY
<<qsort>> is required by ANSI (without specifying the sorting algorithm).
*/

/*-
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <_ansi.h>
#include <stdlib.h>

#ifndef __GNUC__
#define inline
#endif

static inline char      *med3 _PARAMS((char *, char *, char *, int (*cmp)(const _PTR,const _PTR)));
static inline void       swapfunc _PARAMS((char *, char *, int, int));

#define min(a, b)       (a) < (b) ? a : b

/*
 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
 */
#define swapcode(TYPE, parmi, parmj, n) {               \
        long i = (n) / sizeof (TYPE);                   \
        register TYPE *pi = (TYPE *) (parmi);           \
        register TYPE *pj = (TYPE *) (parmj);           \
        do {                                            \
                register TYPE   t = *pi;                \
                *pi++ = *pj;                            \
                *pj++ = t;                              \
        } while (--i > 0);                              \
}

#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
        es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;

static inline void
_DEFUN(swapfunc, (a, b, n, swaptype),
        char *a _AND
        char *b _AND
        int n _AND
        int swaptype)
{
        if(swaptype <= 1) 
                swapcode(long, a, b, n)
        else
                swapcode(char, a, b, n)
}

#define swap(a, b)                                      \
        if (swaptype == 0) {                            \
                long t = *(long *)(a);                  \
                *(long *)(a) = *(long *)(b);            \
                *(long *)(b) = t;                       \
        } else                                          \
                swapfunc(a, b, es, swaptype)

#define vecswap(a, b, n)        if ((n) > 0) swapfunc(a, b, n, swaptype)

static inline char *
_DEFUN(med3, (a, b, c, cmp),
        char *a _AND
        char *b _AND
        char *c _AND
        int (*cmp)(const _PTR,const _PTR))
{
        return cmp(a, b) < 0 ?
               (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
              :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
}

void
_DEFUN(qsort, (a, n, es, cmp),
        void *a _AND
        size_t n _AND
        size_t es _AND
        int (*cmp)(const _PTR,const _PTR))
{
        char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
        int d, r, swaptype, swap_cnt;

loop:   SWAPINIT(a, es);
        swap_cnt = 0;
        if (n < 7) {
                for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
                        for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
                             pl -= es)
                                swap(pl, pl - es);
                return;
        }
        pm = (char *) a + (n / 2) * es;
        if (n > 7) {
                pl = a;
                pn = (char *) a + (n - 1) * es;
                if (n > 40) {
                        d = (n / 8) * es;
                        pl = med3(pl, pl + d, pl + 2 * d, cmp);
                        pm = med3(pm - d, pm, pm + d, cmp);
                        pn = med3(pn - 2 * d, pn - d, pn, cmp);
                }
                pm = med3(pl, pm, pn, cmp);
        }
        swap(a, pm);
        pa = pb = (char *) a + es;

        pc = pd = (char *) a + (n - 1) * es;
        for (;;) {
                while (pb <= pc && (r = cmp(pb, a)) <= 0) {
                        if (r == 0) {
                                swap_cnt = 1;
                                swap(pa, pb);
                                pa += es;
                        }
                        pb += es;
                }
                while (pb <= pc && (r = cmp(pc, a)) >= 0) {
                        if (r == 0) {
                                swap_cnt = 1;
                                swap(pc, pd);
                                pd -= es;
                        }
                        pc -= es;
                }
                if (pb > pc)
                        break;
                swap(pb, pc);
                swap_cnt = 1;
                pb += es;
                pc -= es;
        }
        if (swap_cnt == 0) {  /* Switch to insertion sort */
                for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
                        for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0; 
                             pl -= es)
                                swap(pl, pl - es);
                return;
        }

        pn = (char *) a + n * es;
        r = min(pa - (char *)a, pb - pa);
        vecswap(a, pb - r, r);
        r = min((unsigned int)(pd - pc), pn - pd - es);
        vecswap(pb, pn - r, r);
        if ((unsigned int)(r = pb - pa) > es)
                qsort(a, r / es, es, cmp);
        if ((unsigned int)(r = pd - pc) > es) { 
                /* Iterate rather than recurse to save stack space */
                a = pn - r;
                n = r / es;
                goto loop;
        }
/*              qsort(pn - r, r / es, es, cmp);*/
}