Reading Variable length messages in Qtcp readyRead() - c++

Question

The following code is intended to display an Image sent over network. I sent a header of 16 bytes which I use to calculate the size of image that follows and then read that many bytes and display the image.
I used the concept at this link Tcp packets using QTcpSocket
void socket::readyRead()
{
while(socket->bytesAvailable() > 0) {
quint8 Data[16];
socket->read((char *)&Data,16);
img_size = (((quint8)Data[1]<<8)+ (quint8)Data[0]) * (((quint8)Data[3]<<8)+ (quint8)Data[2]) * 1;
QByteArray buffer = socket->read(img_size);
while(buffer.size() < (img_size))
{
// qDebug() << buffer.size();
socket->waitForReadyRead();
buffer.append(socket->read((img_size)-(buffer.size()) ));
}
unsigned char* imgdatara = (unsigned char*)&buffer.data()[0];
if( !image )
image = new QImage(imgdatara,32,640,QImage::Format_Grayscale8);
else
{
delete image;
image = new QImage(imgdatara,32,640,QImage::Format_Grayscale8);
}
emit msg(image);
}
}
My GUI says "not responding". How should I solve this?
Thanks

Answer 1

This is 100% working code from the book of Max Schlee's "Qt 4.8 Professional programming". This is not a simple question, because on the readyRead() signal you can receive:
1. A complete block
2. Only a part of block
3. Several blocks together
void MyClass::onReceive()
{
QDataStream in(m_pClient);
in.setVersion(QDataStream::Qt_4_6); // Your version. Not necessary.
for(;;)
{
if(m_nextBlockSize == 0)
{
if(m_pClient->bytesAvailable() < sizeof(m_nextBlockSize))
{
break;
}
else
{
in >> m_nextBlockSize;
}
}
if(m_pClient->bytesAvailable() < m_nextBlockSize)
{
break;
}
// Here you have each complete block
processYourBlockHere(); // <=====
m_nextBlockSize = 0;
}
}
Update: useful links for you: Serializing Qt Data Types and QDataStream