/****************************************************************************
* libc/stdlib/lib_qsort.c
*
* Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Leveraged from:
*
* 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdlib.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define min(a, b) (a) < (b) ? a : b
#define swapcode(TYPE, parmi, parmj, n) \
{ \
long 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); \
}
#define SWAPINIT(a, width) \
swaptype = ((FAR char *)a - (FAR char *)0) % sizeof(long) || \
width % sizeof(long) ? 2 : width == sizeof(long)? 0 : 1;
#define swap(a, b) \
if (swaptype == 0) \
{ \
long t = *(long *)(a); \
*(long *)(a) = *(long *)(b); \
*(long *)(b) = t; \
} \
else \
{ \
swapfunc(a, b, width, swaptype); \
}
#define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static inline void swapfunc(FAR char *a, FAR char *b, int n, int swaptype);
static inline FAR char *med3(FAR char *a, FAR char *b, FAR char *c,
CODE int (*compar)(FAR const void *,
FAR const void *));
/****************************************************************************
* Private Functions
****************************************************************************/
static inline void swapfunc(FAR char *a, FAR char *b, int n, int swaptype)
{
if (swaptype <= 1)
{
swapcode(long, a, b, n)
}
else
{
swapcode(char, a, b, n)
}
}
static inline FAR char *med3(FAR char *a, FAR char *b, FAR char *c,
CODE int (*compar)(FAR const void *,
FAR const void *))
{
return compar(a, b) < 0 ?
(compar(b, c) < 0 ? b : (compar(a, c) < 0 ? c : a)) :
(compar(b, c) > 0 ? b : (compar(a, c) < 0 ? a : c));
}
/****************************************************************************
* Public Function
****************************************************************************/
/****************************************************************************
* Name: qsort
*
* Description:
* The qsort() function will sort an array of 'nel' objects, the initial
* element of which is pointed to by 'base'. The size of each object, in
* bytes, is specified by the 'width" argument. If the 'nel' argument has
* the value zero, the comparison function pointed to by 'compar' will not
* be called and no rearrangement will take place.
*
* The application will ensure that the comparison function pointed to by
* 'compar' does not alter the contents of the array. The implementation
* may reorder elements of the array between calls to the comparison
* function, but will not alter the contents of any individual element.
*
* When the same objects (consisting of 'width" bytes, irrespective of
* their current positions in the array) are passed more than once to
* the comparison function, the results will be consistent with one
* another. That is, they will define a total ordering on the array.
*
* The contents of the array will be sorted in ascending order according
* to a comparison function. The 'compar' argument is a pointer to the
* comparison function, which is called with two arguments that point to
* the elements being compared. The application will ensure that the
* function returns an integer less than, equal to, or greater than 0,
* if the first argument is considered respectively less than, equal to,
* or greater than the second. If two members compare as equal, their
* order in the sorted array is unspecified.
*
* (Based on description from OpenGroup.org).
*
* Returned Value:
* The qsort() function will not return a value.
*
* Notes from the original BSD version:
* Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
*
****************************************************************************/
void qsort(FAR void *base, size_t nel, size_t width,
CODE int(*compar)(FAR const void *, FAR const void *))
{
FAR char *pa;
FAR char *pb;
FAR char *pc;
FAR char *pd;
FAR char *pl;
FAR char *pm;
FAR char *pn;
int swaptype;
int swap_cnt;
int d;
int r;
loop:
SWAPINIT(base, width);
swap_cnt = 0;
if (nel < 7)
{
for (pm = (FAR char *)base + width;
pm < (FAR char *)base + nel * width;
pm += width)
{
for (pl = pm;
pl > (FAR char *)base && compar(pl - width, pl) > 0;
pl -= width)
{
swap(pl, pl - width);
}
}
return;
}
pm = (FAR char *)base + (nel / 2) * width;
if (nel > 7)
{
pl = base;
pn = (FAR char *)base + (nel - 1) * width;
if (nel > 40)
{
d = (nel / 8) * width;
pl = med3(pl, pl + d, pl + 2 * d, compar);
pm = med3(pm - d, pm, pm + d, compar);
pn = med3(pn - 2 * d, pn - d, pn, compar);
}
pm = med3(pl, pm, pn, compar);
}
swap(base, pm);
pa = pb = (FAR char *)base + width;
pc = pd = (FAR char *)base + (nel - 1) * width;
for (; ; )
{
while (pb <= pc && (r = compar(pb, base)) <= 0)
{
if (r == 0)
{
swap_cnt = 1;
swap(pa, pb);
pa += width;
}
pb += width;
}
while (pb <= pc && (r = compar(pc, base)) >= 0)
{
if (r == 0)
{
swap_cnt = 1;
swap(pc, pd);
pd -= width;
}
pc -= width;
}
if (pb > pc)
{
break;
}
swap(pb, pc);
swap_cnt = 1;
pb += width;
pc -= width;
}
if (swap_cnt == 0)
{
/* Switch to insertion sort */
for (pm = (FAR char *)base + width;
pm < (FAR char *)base + nel * width;
pm += width)
{
for (pl = pm;
pl > (FAR char *)base && compar(pl - width, pl) > 0;
pl -= width)
{
swap(pl, pl - width);
}
}
return;
}
pn = (FAR char *)base + nel * width;
r = min(pa - (FAR char *)base, pb - pa);
vecswap(base, pb - r, r);
r = min(pd - pc, pn - pd - width);
vecswap(pb, pn - r, r);
if ((r = pb - pa) > width)
{
qsort(base, r / width, width, compar);
}
if ((r = pd - pc) > width)
{
/* Iterate rather than recurse to save stack space */
base = pn - r;
nel = r / width;
goto loop;
}
}