Using QDataStream with an updating file

[DRoscoe]

I am writing a tool that will parse a binary recording file real-time. I was planning on using QDataStream for this purpose. The intention is to open the file and initially parse as much of the file as is currently available, and then set a timer, to periodically read whatever was recorded in the interim. My question is, if I leave data in the stream and the file is written to in the meantime, will the QDataStream update to reflect the current state of the file, in particular bytesAvailable when I next query it?

[VRonin]

Depends if the QIODevice does that, if you are using QFile it should be fine

[DRoscoe]

@VRonin yes, the QIODevice is a QFile

[VRonin]

#include <QApplication>
#include <QTimer>
#include <QFile>
#include <QDataStream>
#include <QTime>
#include <QDebug>
int main(int argc, char* argv[])
{
    QApplication a(argc, argv);
    QFile readFile("test.dat");
    QFile writeFile("test.dat");
    if (!writeFile.open(QIODevice::WriteOnly))
        Q_ASSERT(false);
    if (!readFile.open(QIODevice::ReadOnly))
        Q_ASSERT(false);
    QDataStream readStream(&readFile);
    QDataStream writeStream(&writeFile);
    QTimer writeTimer;
    writeTimer.setInterval(3000);
    QTimer readTimer;
    readTimer.setInterval(500);
    readTimer.setSingleShot(true);
    QObject::connect(&writeTimer, &QTimer::timeout, [&writeStream, &readTimer]()->void {
        const QTime currTime = QTime::currentTime();
        qDebug() << "Saving: " << currTime;
        writeStream << currTime;
        qDebug() << "bytesAvailable: " << writeStream.device()->bytesAvailable();
        readTimer.start();
    });
    QObject::connect(&readTimer, &QTimer::timeout, [&readStream]()->void {
        qDebug() << "bytesAvailable: " << readStream.device()->bytesAvailable();
        QTime currTime;
        readStream >> currTime;
        qDebug() << "Loading: " << currTime;
    });
    QTimer::singleShot(0, &writeTimer, SLOT(start()));
    QTimer::singleShot(10000, &writeTimer, SLOT(stop()));
    return a.exec();
}

[DRoscoe]

@VRonin Thanks... that's exactly what I was hoping for!