/*
 *    Modifications from vanilla NetBSD source:
 *        Add do ... while() macro fix
 *        Remove __inline, _DIAGASSERTs, __P
 *
 *      $PostgreSQL: pgsql/src/port/qsort.c,v 1.5 2004/10/05 00:12:49 neilc Exp $
 */

/*      $NetBSD: qsort.c,v 1.13 2003/08/07 16:43:42 agc 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 <stdlib.h>
#include <errno.h>
#include <sys/types.h>


static char    *med3(char *, char *, char *, int (*) (const void *, const void *));
static 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) \
do {		\
	size_t i = (n) / sizeof (TYPE);			\
	TYPE *pi = (TYPE *)(void *)(parmi);			\
	TYPE *pj = (TYPE *)(void *)(parmj);			\
	do {						\
		TYPE	t = *pi;			\
		*pi++ = *pj;				\
		*pj++ = t;				\
		} while (--i > 0);				\
} while (0)

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

static 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 *)(void *)(a);			\
		*(long *)(void *)(a) = *(long *)(void *)(b);	\
		*(long *)(void *)(b) = t;			\
	} else							\
		swapfunc(a, b, es, swaptype)

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

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

	SWAPINIT(a, es);
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 = (char *) 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)
        qsortB(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;
    }
}