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optimizedbytearray.h
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optimizedbytearray.h
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/*
* This file is part of the KDE Nepomuk Project
* Copyright (C) 2012 Vishesh Handa <me@vhanda.in>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#ifndef OPTIMIZED_BYTE_ARRAY_H
#define OPTIMIZED_BYTE_ARRAY_H
#include <QHash>
#include <QVector>
#include <QByteArray>
#include <QSet>
#include <KDebug>
/**
* This class holds a QByteArray which corresponds to a file url in a
* more memory efficient manner.
*
* It does so by spliting the url along the directory separator '/', and
* saving each path separately in a QVector. This is more memory efficient
* than storing it together cause it uses a QSet<QByteArray> cache to lookup
* each part of the vector. This way, multiple OptimizedByteArrays share common
* parts of the url. This happens because Qt's containers are reference counted.
*
* \author Vishesh Handa <me@vhanda.in>
*
*/
class OptimizedByteArray
{
public:
OptimizedByteArray() {}
OptimizedByteArray(const QByteArray& array, QSet<QByteArray>& cache) {
QList<QByteArray> list = array.split('/');
QVector<QByteArray> vec;
vec.reserve(list.size());
Q_FOREACH (const QByteArray& ba, list) {
if (!ba.isEmpty())
vec << ba;
}
m_data.reserve(vec.size());
Q_FOREACH (const QByteArray& arr, vec) {
QSet< QByteArray >::iterator it = cache.find(arr);
if (it != cache.end())
m_data.append(*it);
else
m_data.append(*cache.insert(arr));
}
}
QByteArray toByteArray() const {
int size = 0;
Q_FOREACH (const QByteArray& arr, m_data)
size += arr.size() + 1;
QByteArray array;
array.reserve(size);
Q_FOREACH (const QByteArray& arr, m_data) {
array.append('/');
array.append(arr);
}
return array;
}
bool operator==(const OptimizedByteArray& other) const {
return m_data == other.m_data;
}
private:
QVector<QByteArray> m_data;
};
uint qHash(const OptimizedByteArray& arr)
{
return qHash(arr.toByteArray());
}
Q_DECLARE_METATYPE(OptimizedByteArray)
Q_DECLARE_TYPEINFO(OptimizedByteArray, Q_MOVABLE_TYPE);
#endif // OPTIMIZED_BYTE_ARRAY_H

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