/*$OpenBSD : qsort.c, v 1.14 2017 / 01 / 04 15 : 20 : 30 millert Exp $ * /
/*-
 * 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 <sys/types.h>
#include <stdlib.h>

static __inline char *med3(char *, char *, char *, int (*)(const void *, const void *));
static __inline void swapfunc(char *, char *, size_t, 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) \
    {                                   \
        size_t i = (n) / sizeof(TYPE);  \
        TYPE *pi = (TYPE *)(parmi);     \
        TYPE *pj = (TYPE *)(parmj);     \
        do                              \
        {                               \
            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
swapfunc(char *a, char *b, size_t n, 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 *
med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *))
{
    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 qsort(void *aa, size_t n, size_t es, int (*cmp)(const void *, const void *))
{
    char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
    int cmp_result, swaptype;
    size_t d, r;
    char *a = aa;

loop:
    SWAPINIT(a, es);
    if (n < 7)
    {
        for (pm = a + es; pm < a + n * es; pm += es)
            for (pl = pm; pl > a && cmp(pl - es, pl) > 0;
                 pl -= es)
                swap(pl, pl - es);
        return;
    }
    pm = a + (n / 2) * es;
    if (n > 7)
    {
        pl = a;
        pn = 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 = a + es;

    pc = pd = a + (n - 1) * es;
    for (;;)
    {
        while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0)
        {
            if (cmp_result == 0)
            {
                swap(pa, pb);
                pa += es;
            }
            pb += es;
        }
        while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0)
        {
            if (cmp_result == 0)
            {
                swap(pc, pd);
                pd -= es;
            }
            pc -= es;
        }
        if (pb > pc)
            break;
        swap(pb, pc);
        pb += es;
        pc -= es;
    }

    pn = a + n * es;
    r = min(pa - 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);*/
}
DEF_STRONG(qsort);