Display progress bar as copying one file

]class MyClass : ...
{
...
public slots:
void onWrite( qint64 );
};

MyClass::MyClass( ... )
{
// ...
progress->setMaximum( QFileInfo(fromFile).size() / 1024 );
written = 0;
connect( &toFile, SIGNAL(bytesWritten(qint64)), SLOT(onWrite(qint64)) );
// ...
}

void MyClass::onWrite( qint64 w )
{
written += w;
progress->setValue( written / 1024 );
}