# qsort.c

/*-
*
* 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);*/
}