/*
* Copyright (c) 2017 Jiri Svoboda
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - 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.
* - The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
/** @addtogroup libc
* @{
*/
/**
* @file
* @brief Quicksort.
*/
#include <qsort.h>
#include <stdbool.h>
#include <stddef.h>
/** Quicksort spec */
typedef struct {
void *base;
size_t nmemb;
size_t size;
int (*compar)(const void *, const void *, void *);
void *arg;
} qs_spec_t;
/** Comparison function wrapper.
*
* Performs qsort_r comparison using qsort comparison function
*
* @param a First element
* @param b Second element
* @param arg qsort comparison function
*/
static int compar_wrap(const void *a, const void *b, void *arg)
{
int (*compar)(const void *, const void *) =
(int (*)(const void *, const void *))arg;
return compar(a, b);
}
/** Determine if one element is less-than another element.
*
* @param qs Quicksort spec
* @param i First element index
* @param j Second element index
*/
static bool elem_lt(qs_spec_t *qs, size_t i, size_t j)
{
const void *a;
const void *b;
int r;
a = qs->base + i * qs->size;
b = qs->base + j * qs->size;
r = qs->compar(a, b, qs->arg);
return r < 0;
}
/** Swap two elements.
*
* @param qs Quicksort spec
* @param i First element index
* @param j Second element index
*/
static void elem_swap(qs_spec_t *qs, size_t i, size_t j)
{
char *a;
char *b;
char t;
size_t k;
a = qs->base + i * qs->size;
b = qs->base + j * qs->size;
for (k = 0; k < qs->size; k++) {
t = a[k];
a[k] = b[k];
b[k] = t;
}
}
/** Partition a range of indices.
*
* @param qs Quicksort spec
* @param lo Lower bound (inclusive)
* @param hi Upper bound (inclusive)
* @return Pivot index
*/
static size_t partition(qs_spec_t *qs, size_t lo, size_t hi)
{
size_t pivot;
size_t i, j;
pivot = lo + (hi - lo) / 2;
i = lo;
j = hi;
while (true) {
while (elem_lt(qs, i, pivot))
++i;
while (elem_lt(qs, pivot, j))
--j;
if (i >= j)
return j;
elem_swap(qs, i, j);
/* Need to follow pivot movement */
if (i == pivot)
pivot = j;
else if (j == pivot)
pivot = i;
i++;
j--;
}
}
/** Sort a range of indices.
*
* @param qs Quicksort spec
* @param lo Lower bound (inclusive)
* @param hi Upper bound (inclusive)
*/
static void quicksort(qs_spec_t *qs, size_t lo, size_t hi)
{
size_t p;
if (lo < hi) {
p = partition(qs, lo, hi);
quicksort(qs, lo, p);
quicksort(qs, p + 1, hi);
}
}
/** Quicksort.
*
* @param base Array to sort
* @param nmemb Number of array members
* @param size Size of member in bytes
* @param compar Comparison function
*/
void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *,
const void *))
{
qs_spec_t qs;
if (nmemb == 0)
return;
qs.base = base;
qs.nmemb = nmemb;
qs.size = size;
qs.compar = compar_wrap;
qs.arg = compar;
quicksort(&qs, 0, nmemb - 1);
}
/** Quicksort with extra argument to comparison function.
*
* @param base Array to sort
* @param nmemb Number of array members
* @param size Size of member in bytes
* @param compar Comparison function
* @param arg Argument to comparison function
*/
void qsort_r(void *base, size_t nmemb, size_t size, int (*compar)(const void *,
const void *, void *), void *arg)
{
qs_spec_t qs;
if (nmemb == 0)
return;
qs.base = base;
qs.nmemb = nmemb;
qs.size = size;
qs.compar = compar;
qs.arg = arg;
quicksort(&qs, 0, nmemb - 1);
}
/** @}
*/