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/* $OpenBSD: qsort.c,v 1.17 2017/05/24 21:18:25 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".
*
* This version differs from Bentley & McIlroy in the following ways:
* 1. The partition value is swapped into a[0] instead of being
* stored out of line.
*
* 2. The swap function can swap 32-bit aligned elements on 64-bit
* platforms instead of swapping them as byte-aligned.
*
* 3. It uses David Musser's introsort algorithm to fall back to
* heapsort(3) when the recursion depth reaches 2*lg(n + 1).
* This avoids quicksort's quadratic behavior for pathological
* input without appreciably changing the average run time.
*
* 4. Tail recursion is eliminated when sorting the larger of two
* subpartitions to save stack space.
*/
#define SWAPTYPE_BYTEV 1
#define SWAPTYPE_INTV 2
#define SWAPTYPE_LONGV 3
#define SWAPTYPE_INT 4
#define SWAPTYPE_LONG 5
#define TYPE_ALIGNED(TYPE, a, es) \
(((char *)a - (char *)0) % sizeof(TYPE) == 0 && es % sizeof(TYPE) == 0)
#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); \
}
static __inline void
swapfunc(char *a, char *b, size_t n, int swaptype)
{
switch (swaptype) {
case SWAPTYPE_INT:
case SWAPTYPE_INTV:
swapcode(int, a, b, n);
break;
case SWAPTYPE_LONG:
case SWAPTYPE_LONGV:
swapcode(long, a, b, n);
break;
default:
swapcode(char, a, b, n);
break;
}
}
#define swap(a, b) do { \
switch (swaptype) { \
case SWAPTYPE_INT: { \
int t = *(int *)(a); \
*(int *)(a) = *(int *)(b); \
*(int *)(b) = t; \
break; \
} \
case SWAPTYPE_LONG: { \
long t = *(long *)(a); \
*(long *)(a) = *(long *)(b); \
*(long *)(b) = t; \
break; \
} \
default: \
swapfunc(a, b, es, swaptype); \
} \
} while (0)
#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 ));
}
static void
introsort(char *a, size_t n, size_t es, size_t maxdepth, int swaptype,
int (*cmp)(const void *, const void *))
{
char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
int cmp_result;
size_t r, s;
loop: if (maxdepth == 0) {
if (heapsort(a, n, es, cmp) == 0)
return;
}
maxdepth--;
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) {
s = (n / 8) * es;
pl = med3(pl, pl + s, pl + 2 * s, cmp);
pm = med3(pm - s, pm, pm + s, cmp);
pn = med3(pn - 2 * s, pn - s, 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);
/*
* 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) {
introsort(a, r / es, es, maxdepth,
swaptype, cmp);
}
a = pn - s;
n = s / es;
goto loop;
}
} else {
/* Recurse for 2nd side, iterate for 1st side. */
if (r > es) {
if (s > es) {
introsort(pn - s, s / es, es, maxdepth,
swaptype, cmp);
}
n = r / es;
goto loop;
}
}
}
void
qsort(void *a, size_t n, size_t es, int (*cmp)(const void *, const void *))
{
size_t i, maxdepth = 0;
int swaptype;
/* Approximate 2*ceil(lg(n + 1)) */
for (i = n; i > 0; i >>= 1)
maxdepth++;
maxdepth *= 2;
if (TYPE_ALIGNED(long, a, es))
swaptype = es == sizeof(long) ? SWAPTYPE_LONG : SWAPTYPE_LONGV;
else if (sizeof(int) != sizeof(long) && TYPE_ALIGNED(int, a, es))
swaptype = es == sizeof(int) ? SWAPTYPE_INT : SWAPTYPE_INTV;
else
swaptype = SWAPTYPE_BYTEV;
introsort(a, n, es, maxdepth, swaptype, cmp);
}
DEF_STRONG(qsort);
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