#include <QImage>
#include <QImageReader>
#include <QImageWriter>
#include <QTemporaryFile>
#include <QDebug>
#include <limits>

int main(int argc, char *argv[])
{
    QTemporaryFile tempFile;
    tempFile.open();

    QImage outputImg(QSize(30,30), QImage::Format_Grayscale8);
    outputImg.fill(QColor("black"));


    QList<quint64> positions;
    positions << 0
              << std::numeric_limits<int>::max()
              << std::numeric_limits<uint>::max();

    for(qint64 pos: positions)
    {
        qDebug() << "Seeking to " << pos;
        tempFile.seek(pos);

        QImageWriter w((QIODevice*)&tempFile, "bmp");
        w.write(outputImg);
        qDebug() << "Wrote from " << pos << " to " << tempFile.pos();
        Q_ASSERT(tempFile.pos() > pos);

        // Now go back to where we wrote it and read it
        tempFile.seek(pos);
        qDebug() << "Reading from " << pos;

        QImageReader r((QIODevice*)&tempFile, "bmp");

        QImage resultImg = r.read();
        Q_ASSERT(!resultImg.isNull());

        qDebug() << "Read from " << pos << " to " << tempFile.pos();
        Q_ASSERT(tempFile.pos() > pos);
    }
    qDebug() << "Done";
    return 0;
}