qsort.c

/*-
 * 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. 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 <stdlib.h>
#include "sectionname.h"

typedef int cmp_t(const void *, const void *);
static char *med3(char *, char *, char *, cmp_t *);
static void swapfunc(char *, char *, 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) {               \
        int 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);                              \
}

ATTRIBUTE_CLIB_SECTION
static void
swapfunc(char *a, char *b, int n)
{
        swapcode(char, a, b, n)
}

#define swap(a, b) swapfunc(a, b, es)

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

ATTRIBUTE_CLIB_SECTION
static char *
med3(char *a, char *b, char *c, cmp_t *cmp)
{
        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 ));
}

ATTRIBUTE_CLIB_SECTION
void
qsort(void *a, size_t n, size_t es, cmp_t *cmp)
{
        char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
        int d, r, swap_cnt;

loop:
        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(pd - pc, pn - pd - es);
        vecswap(pb, pn - r, r);
        if ((r = pb - pa) > es)
                qsort(a, r / es, es, cmp);
        if ((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);*/
}