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/***************************************************************************
* Copyright (C) 2012 by Peter Penz <[email protected]> *
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
* This program is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program; if not, write to the *
* Free Software Foundation, Inc., *
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA *
***************************************************************************/
#include "kfileitemmodelsortalgorithm.h"
#include <QThread>
#include <QtCore>
#include <algorithm>
class KFileItemModelLessThan
{
public:
KFileItemModelLessThan(KFileItemModel* model) :
m_model(model)
{
}
bool operator()(const KFileItemModel::ItemData* a, const KFileItemModel::ItemData* b)
{
return m_model->lessThan(a, b);
}
private:
KFileItemModel* m_model;
};
void KFileItemModelSortAlgorithm::sort(KFileItemModel* model,
QList<KFileItemModel::ItemData*>::iterator begin,
QList<KFileItemModel::ItemData*>::iterator end)
{
KFileItemModelLessThan lessThan(model);
if (model->sortRole() == model->roleForType(KFileItemModel::NameRole)) {
// Sorting by name can be expensive, in particular if natural sorting is
// enabled. Use all CPU cores to speed up the sorting process.
static const int numberOfThreads = QThread::idealThreadCount();
parallelSort(begin, end, lessThan, numberOfThreads);
} else {
// Sorting by other roles is quite fast. Use only one thread to prevent
// problems caused by non-reentrant comparison functions, see
// https://bugs.kde.org/show_bug.cgi?id=312679
sequentialSort(begin, end, lessThan);
}
}
template <typename RandomAccessIterator, typename LessThan>
static void sequentialSort(RandomAccessIterator begin,
RandomAccessIterator end,
LessThan lessThan)
{
// The implementation is based on qStableSortHelper() from qalgorithms.h
// Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
const int span = end - begin;
if (span < 2) {
return;
}
const RandomAccessIterator middle = begin + span / 2;
sequentialSort(begin, middle, lessThan);
sequentialSort(middle, end, lessThan);
merge(begin, middle, end, lessThan);
}
template <typename RandomAccessIterator, typename LessThan>
static void parallelSort(RandomAccessIterator begin,
RandomAccessIterator end,
LessThan lessThan,
int numberOfThreads,
int parallelSortingThreshold)
{
const int span = end - begin;
if (numberOfThreads > 1 && span > parallelSortingThreshold) {
const int newNumberOfThreads = numberOfThreads / 2;
const RandomAccessIterator middle = begin + span / 2;
QFuture<void> future = QtConcurrent::run(parallelSort<RandomAccessIterator, LessThan>, begin, middle, lessThan, newNumberOfThreads, parallelSortingThreshold);
parallelSort(middle, end, lessThan, newNumberOfThreads, parallelSortingThreshold);
future.waitForFinished();
merge(begin, middle, end, lessThan);
} else {
sequentialSort(begin, end, lessThan);
}
}
template <typename RandomAccessIterator, typename LessThan>
static void merge(RandomAccessIterator begin,
RandomAccessIterator pivot,
RandomAccessIterator end,
LessThan lessThan)
{
// The implementation is based on qMerge() from qalgorithms.h
// Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
const int len1 = pivot - begin;
const int len2 = end - pivot;
if (len1 == 0 || len2 == 0) {
return;
}
if (len1 + len2 == 2) {
if (lessThan(*(begin + 1), *(begin))) {
qSwap(*begin, *(begin + 1));
}
return;
}
RandomAccessIterator firstCut;
RandomAccessIterator secondCut;
int len2Half;
if (len1 > len2) {
const int len1Half = len1 / 2;
firstCut = begin + len1Half;
secondCut = std::lower_bound(pivot, end, *firstCut, lessThan);
len2Half = secondCut - pivot;
} else {
len2Half = len2 / 2;
secondCut = pivot + len2Half;
firstCut = std::upper_bound(begin, pivot, *secondCut, lessThan);
}
std::rotate(firstCut, pivot, secondCut);
RandomAccessIterator newPivot = firstCut + len2Half;
merge(begin, firstCut, newPivot, lessThan);
merge(newPivot, secondCut, end, lessThan);
}
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