Simple read / write verification of qdatastream

The purpose is to write binary files and read contents ：

#include <QApplication>
#include <QFile>

int main(int argc, char *argv[])
{
    
    QApplication a(argc, argv);

    QFile aFile1("file.dat");
    if (!(aFile1.open(QIODevice::WriteOnly)))// Open file in write only mode 
        return -1;
    QDataStream bStream(&aFile1);
    bStream.setVersion(QDataStream::Qt_5_9);

    // Write the total size information space in turn , File name size information space , file name 
    QString currentFileName = "abcdFile" ;
    qint64 v1 = 0,v2 = 0;
    bStream << qint64(v1) << qint64(v2) << currentFileName;

    // Cursor returns to the beginning of the file qint64 Make changes 
    bStream.device()->seek(0);
    v1 = 13548,v2 = 8;
    bStream<< qint64(v1) << qint64(v2);

    // This step is to refresh the file , Let the written document take effect 
    aFile1.flush();
    aFile1.close();

 //  Read dat file 
    QFile aFile2("file.dat");
    if (!(aFile2.open(QIODevice::ReadOnly)))// Open file in write only mode 
        return -1;

    QDataStream aStream(&aFile2);
    aStream.setVersion(QDataStream::Qt_5_9);
    qint64 v3 = 0,v4 = 0;
    aStream >> v3 >> v4 >> currentFileName;// Reading data , Deposit in tem and str
    qDebug() << v3 << v4 << currentFileName ;// Print it out and see the result 
    aFile2.close();

    return a.exec();
}