/*      $NetBSD: qsort.c,v 1.24 2025/03/02 16:35:41 riastradh 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/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)qsort.c     8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: qsort.c,v 1.24 2025/03/02 16:35:41 riastradh Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>

#include <assert.h>
#include <errno.h>
#include <stdlib.h>

static inline char      *med3(char *, char *, char *,
                            int (*)(const void *, const void *, void *),
                            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 *)(void *)(parmi);             \
        TYPE *pj = (TYPE *)(void *)(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 *)(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 inline char *
med3(char *a, char *b, char *c,
    int (*cmp)(const void *, const void *, void *), void *cookie)
{

        return cmp(a, b, cookie) < 0 ?
               (cmp(b, c, cookie) < 0 ? b : (cmp(a, c, cookie) < 0 ? c : a ))
              :(cmp(b, c, cookie) > 0 ? b : (cmp(a, c, cookie) < 0 ? a : c ));
}

void
qsort_r(void *a, size_t n, size_t es,
    int (*cmp)(const void *, const void *, void *), void *cookie)
{
        char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
        size_t d, r, s;
        int swaptype, cmp_result;

        _DIAGASSERT(a != NULL || n == 0 || es == 0);
        _DIAGASSERT(cmp != NULL);

loop:   SWAPINIT(a, es);
        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, cookie) > 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, cookie);
                        pm = med3(pm - d, pm, pm + d, cmp, cookie);
                        pn = med3(pn - 2 * d, pn - d, pn, cmp, cookie);
                }
                pm = med3(pl, pm, pn, cmp, cookie);
        }
        swap(a, pm);
        pa = pb = (char *) a + es;

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

        pn = (char *) a + n * es;
        r = min(pa - (char *) a, pb - pa);
        vecswap(a, pb - r, r);
        r = min((size_t)(pd - pc), pn - pd - es);
        vecswap(pb, pn - r, r);
        /*
         * To save stack space we sort the smaller side of the partition first
         * using recursion and eliminate tail recursion for the larger side.
         */
        r = pb - pa;
        s = pd - pc;
        if (r < s) {
                /* Recurse for 1st side, iterate for 2nd side. */
                if (s > es) {
                        if (r > es)
                                qsort_r(a, r / es, es, cmp, cookie);
                        a = pn - s;
                        n = s / es;
                        goto loop;
                }
        } else {
                /* Recurse for 2nd side, iterate for 1st side. */
                if (r > es) {
                        if (s > es)
                                qsort_r(pn - s, s / es, es, cmp, cookie);
                        n = r / es;
                        goto loop;
                }
        }
}

static int
cmpnocookie(const void *a, const void *b, void *cookie)
{
        int (*cmp)(const void *, const void *) = cookie;

        return cmp(a, b);
}

void
qsort(void *a, size_t n, size_t es,
    int (*cmp)(const void *, const void *))
{

        qsort_r(a, n, es, cmpnocookie, cmp);
}