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/*
Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies)
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public License
along with this library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
*/
#ifndef DNSPREFETCHHELPER_H
#define DNSPREFETCHHELPER_H
#include <QObject>
#include <QCache>
#include <QHostInfo>
#include <QSet>
#include <QString>
#include <QTime>
#include "qwebsettings.h"
namespace WebCore {
class DnsPrefetchHelper : public QObject {
Q_OBJECT
public:
DnsPrefetchHelper() : QObject(), currentLookups(0) {};
public slots:
void lookup(QString hostname)
{
if (hostname.isEmpty())
return; // this actually happens
if (currentLookups >= 10)
return; // do not launch more than 10 lookups at the same time
#if QT_VERSION >= QT_VERSION_CHECK(4, 6, 3)
currentLookups++;
QHostInfo::lookupHost(hostname, this, SLOT(lookedUp(QHostInfo)));
#else
// This code is only needed for Qt versions that do not have
// the small Qt DNS cache yet.
QTime* entryTime = lookupCache.object(hostname);
if (entryTime && entryTime->elapsed() > 300*1000) {
// delete knowledge about lookup if it is already 300 seconds old
lookupCache.remove(hostname);
} else if (!entryTime) {
// not in cache yet, can look it up
QTime *tmpTime = new QTime();
*tmpTime = QTime::currentTime();
lookupCache.insert(hostname, tmpTime);
currentLookups++;
QHostInfo::lookupHost(hostname, this, SLOT(lookedUp(QHostInfo)));
}
#endif
}
void lookedUp(const QHostInfo&)
{
// we do not cache the result, we throw it away.
// we currently rely on the OS to cache the results. If it does not do that
// then at least the ISP nameserver did it.
// Since Qt 4.6.3, Qt also has a small DNS cache.
currentLookups--;
}
protected:
#if QT_VERSION < QT_VERSION_CHECK(4, 6, 3)
QCache<QString, QTime> lookupCache; // 100 entries
#endif
int currentLookups;
};
}
#endif // DNSPREFETCHHELPER_H
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