Is it possible to get rawHeaders from QNetworkReply without waiting to finished?

[Alir3z4]

Hi!
the title describes everything! :|
for more details:
i want o download a file, but before to download it, i want to get the file size by the Url, but i couldn't get it till QNetworkAccessManager or QNetworkReply signals[finished, readyRead] emited.
Can i retrieve the headers before to those signals emit ?

[ChrisW67]

Assuming you are talking about HTTP here are some options:

• Send a head() request to get the headers without the body.
• Connect something to the QNetworkReply::metaDataChanged() signal and look at the headers at that point.

[Alir3z4]

Simply i give-up so far done that in separate function to handle something like that, similar to startRequest() function from DownloadManager example.

[ChrisW67]

I could not make any sense of your last post. You've given up? Did you try anything I suggested?

Here is a working example:

#include <QtCore>
#include <QtNetwork>
#include <QDebug>
 
class Fetcher: public QObject
{
    Q_OBJECT
public:
    Fetcher(QObject *p = 0): QObject(p)
    { 
        QTimer::singleShot(0, this, SLOT(start()));
    }
 
public slots:
    void start() {
        fetched = 0;
        size = 0;
        QNetworkRequest req(QUrl("http://qt.nokia.com/files/pdf/faster-more-cost-effective-development-using-the-qt-cross-platform-application-ui-framework"));
        reply = nam.get(req);
 
        connect(reply, SIGNAL(metaDataChanged()), this, SLOT(replyMetaDataChanged()));
        connect(reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead()));
        connect(reply, SIGNAL(finished()), this, SLOT(replyFinished()));
    }
 
    void replyMetaDataChanged() {
        qDebug() << "Metadata changed";
        qDebug() << "Content-Length:" << reply->header(QNetworkRequest::ContentLengthHeader);
        size = reply->header(QNetworkRequest::ContentLengthHeader).toLongLong();
    }
 
    void slotReadyRead() {
        QByteArray ba = reply->readAll();
        fetched += ba.size();
        qDebug() << "Read" << fetched << "of" << size;
 
    }
 
    void replyFinished() {
        qDebug() << "Finished";
    }
 
private:
    QNetworkAccessManager nam;
    QNetworkReply *reply;
    qint64 fetched;
    qint64 size;
};
 
int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);
 
    Fetcher f;
    return app.exec();
}
#include "main.moc"

#include <QtCore>
#include <QtNetwork>
#include <QDebug>

class Fetcher: public QObject
{
    Q_OBJECT
public:
    Fetcher(QObject *p = 0): QObject(p)
    { 
        QTimer::singleShot(0, this, SLOT(start()));
    }

public slots:
    void start() {
        fetched = 0;
        size = 0;
        QNetworkRequest req(QUrl("http://qt.nokia.com/files/pdf/faster-more-cost-effective-development-using-the-qt-cross-platform-application-ui-framework"));
        reply = nam.get(req);

        connect(reply, SIGNAL(metaDataChanged()), this, SLOT(replyMetaDataChanged()));
        connect(reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead()));
        connect(reply, SIGNAL(finished()), this, SLOT(replyFinished()));
    }

    void replyMetaDataChanged() {
        qDebug() << "Metadata changed";
        qDebug() << "Content-Length:" << reply->header(QNetworkRequest::ContentLengthHeader);
        size = reply->header(QNetworkRequest::ContentLengthHeader).toLongLong();
    }

    void slotReadyRead() {
        QByteArray ba = reply->readAll();
        fetched += ba.size();
        qDebug() << "Read" << fetched << "of" << size;

    }

    void replyFinished() {
        qDebug() << "Finished";
    }

private:
    QNetworkAccessManager nam;
    QNetworkReply *reply;
    qint64 fetched;
    qint64 size;
};

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);

    Fetcher f;
    return app.exec();
}
#include "main.moc"

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You will strike problems with the Content-Length header as it is not mandatory.

[Alir3z4]

Yes, But after that i figure it out

before to download it, i want to get the file size by the Url, but i couldn't get it till QNetworkAccessManager or QNetworkReply signals[finished, readyRead] emited.

is somehow or totally stupid, i could simply just move the logic of retrieving the file size after the those signals emitted then do whatever on it.

[ChrisW67]

Take a look at my last post (I edited it while you were replying). If you do head() rather than get() you only get the headers - the example actually fetches the file but sees the headers before it sees the data.

[Alir3z4]

Wow, thank you! :x
now i got it.
This way you provide, it's make code more clear and logical !