when QBuffer emits readyRead signal?

[mastupristi]

So when you write to the QBuffer instance, that is when the readyRead signal is emitted. Your slot can then retrieve the QByteArray and read the new contents.

I tried a little example
qt-buffer.tar.gz

class Dialog : public QDialog
{
    Q_OBJECT
 
public:
    explicit Dialog(QWidget *parent = 0);
    ~Dialog();
 
private:
    Ui::Dialog *ui;
 
    QBuffer *m_buffer;
    QByteArray *m_bytearray;
 
public slots:
    void onClick(void);
    void onDataReady(void);
};
 
 
Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);
 
    m_bytearray = new QByteArray;
    m_buffer = new QBuffer(m_bytearray);
    m_buffer->open(QIODevice::ReadWrite);
 
    connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(onClick()));
    connect(m_buffer, SIGNAL(readyRead()), this, SLOT(onDataReady()));
}
 
Dialog::~Dialog()
{
    delete m_buffer;
    delete m_bytearray;
    delete ui;
}
 
void Dialog::onClick(void)
{
    qDebug() << "write in buffer";
    m_buffer->write("hallo");
}
 
void Dialog::onDataReady(void)
{
    QByteArray ba;
    ba = m_buffer->readAll();
    qDebug() << "read" << ba.size() << "bytes";
}

class Dialog : public QDialog
{
    Q_OBJECT

public:
    explicit Dialog(QWidget *parent = 0);
    ~Dialog();

private:
    Ui::Dialog *ui;

    QBuffer *m_buffer;
    QByteArray *m_bytearray;

public slots:
    void onClick(void);
    void onDataReady(void);
};


Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);

    m_bytearray = new QByteArray;
    m_buffer = new QBuffer(m_bytearray);
    m_buffer->open(QIODevice::ReadWrite);

    connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(onClick()));
    connect(m_buffer, SIGNAL(readyRead()), this, SLOT(onDataReady()));
}

Dialog::~Dialog()
{
    delete m_buffer;
    delete m_bytearray;
    delete ui;
}

void Dialog::onClick(void)
{
    qDebug() << "write in buffer";
    m_buffer->write("hallo");
}

void Dialog::onDataReady(void)
{
    QByteArray ba;
    ba = m_buffer->readAll();
    qDebug() << "read" << ba.size() << "bytes";
}

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when write() is called the readyRead() actually emitted.
But once in the onDataReady(), the call to readAll() returns an empty bytearray, though in m_bytearray is present the string "hallo".

It seems that it is positioned to the end of the bytearray. I tried to modify:

void Dialog::onClick(void)
{
    qDebug() << "write in buffer";
    m_buffer->write("hallo");
    m_buffer->reset();
}

void Dialog::onClick(void)
{
    qDebug() << "write in buffer";
    m_buffer->write("hallo");
    m_buffer->reset();
}

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This works, but the second time I click the button it read a string "hallohallo", the third I read "hallohallohallo", an so on...

what is the proper way to read only bytes written in onClick()?

best regards
max