common/include/QtNetwork/5.5.0/QtNetwork/private/qhostinfo_p.h

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**
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#ifndef QHOSTINFO_P_H
#define QHOSTINFO_P_H

//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists for the convenience
// of the QHostInfo class.  This header file may change from
// version to version without notice, or even be removed.
//
// We mean it.
//

#include "QtCore/qcoreapplication.h"
#include "private/qcoreapplication_p.h"
#include "QtNetwork/qhostinfo.h"
#include "QtCore/qmutex.h"
#include "QtCore/qwaitcondition.h"
#include "QtCore/qobject.h"
#include "QtCore/qpointer.h"
#include "QtCore/qthread.h"
#include "QtCore/qthreadpool.h"
#include "QtCore/qrunnable.h"
#include "QtCore/qlist.h"
#include "QtCore/qqueue.h"
#include <QElapsedTimer>
#include <QCache>

#include <QNetworkSession>
#include <QSharedPointer>


QT_BEGIN_NAMESPACE


class QHostInfoResult : public QObject
{
    Q_OBJECT
public Q_SLOTS:
    inline void emitResultsReady(const QHostInfo &info)
    {
        emit resultsReady(info);
    }

Q_SIGNALS:
    void resultsReady(const QHostInfo &info);
};

// needs to be QObject because fromName calls tr()
class QHostInfoAgent : public QObject
{
    Q_OBJECT
public:
    static QHostInfo fromName(const QString &hostName);
#ifndef QT_NO_BEARERMANAGEMENT
    static QHostInfo fromName(const QString &hostName, QSharedPointer<QNetworkSession> networkSession);
#endif
};

class QHostInfoPrivate
{
public:
    inline QHostInfoPrivate()
        : err(QHostInfo::NoError),
          errorStr(QLatin1String(QT_TRANSLATE_NOOP("QHostInfo", "Unknown error"))),
          lookupId(0)
    {
    }
#ifndef QT_NO_BEARERMANAGEMENT
    //not a public API yet
    static QHostInfo fromName(const QString &hostName, QSharedPointer<QNetworkSession> networkSession);
#endif

    QHostInfo::HostInfoError err;
    QString errorStr;
    QList<QHostAddress> addrs;
    QString hostName;
    int lookupId;
};

// These functions are outside of the QHostInfo class and strictly internal.
// Do NOT use them outside of QAbstractSocket.
QHostInfo Q_NETWORK_EXPORT qt_qhostinfo_lookup(const QString &name, QObject *receiver, const char *member, bool *valid, int *id);
void Q_AUTOTEST_EXPORT qt_qhostinfo_clear_cache();
void Q_AUTOTEST_EXPORT qt_qhostinfo_enable_cache(bool e);
void Q_AUTOTEST_EXPORT qt_qhostinfo_cache_inject(const QString &hostname, const QHostInfo &resolution);

class QHostInfoCache
{
public:
    QHostInfoCache();
    const int max_age; // seconds

    QHostInfo get(const QString &name, bool *valid);
    void put(const QString &name, const QHostInfo &info);
    void clear();

    bool isEnabled();
    void setEnabled(bool e);
private:
    bool enabled;
    struct QHostInfoCacheElement {
        QHostInfo info;
        QElapsedTimer age;
    };
    QCache<QString,QHostInfoCacheElement> cache;
    QMutex mutex;
};

// the following classes are used for the (normal) case: We use multiple threads to lookup DNS

class QHostInfoRunnable : public QRunnable
{
public:
    QHostInfoRunnable(const QString &hn, int i);
    void run() Q_DECL_OVERRIDE;

    QString toBeLookedUp;
    int id;
    QHostInfoResult resultEmitter;
};


class QAbstractHostInfoLookupManager : public QObject
{
    Q_OBJECT

public:
    ~QAbstractHostInfoLookupManager() {}
    virtual void clear() = 0;

    QHostInfoCache cache;

protected:
     QAbstractHostInfoLookupManager() {}
     static QAbstractHostInfoLookupManager* globalInstance();

};

class QHostInfoLookupManager : public QAbstractHostInfoLookupManager
{
    Q_OBJECT
public:
    QHostInfoLookupManager();
    ~QHostInfoLookupManager();

    void clear() Q_DECL_OVERRIDE;
    void work();

    // called from QHostInfo
    void scheduleLookup(QHostInfoRunnable *r);
    void abortLookup(int id);

    // called from QHostInfoRunnable
    void lookupFinished(QHostInfoRunnable *r);
    bool wasAborted(int id);

    friend class QHostInfoRunnable;
protected:
    QList<QHostInfoRunnable*> currentLookups; // in progress
    QList<QHostInfoRunnable*> postponedLookups; // postponed because in progress for same host
    QQueue<QHostInfoRunnable*> scheduledLookups; // not yet started
    QList<QHostInfoRunnable*> finishedLookups; // recently finished
    QList<int> abortedLookups; // ids of aborted lookups

    QThreadPool threadPool;

    QMutex mutex;

    bool wasDeleted;

private slots:
    void waitForThreadPoolDone() { threadPool.waitForDone(); }
};

QT_END_NAMESPACE

#endif // QHOSTINFO_P_H