DnsPrefetchHelper.h   [plain text]

/*
    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

            currentLookups++;
            QHostInfo::lookupHost(hostname, this, SLOT(lookedUp(QHostInfo)));
        }

        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:
        int currentLookups;
    };


}

#endif // DnsPrefetchHelper_h