How to: Tokenization (Splitting) QBytearray data?

ahsan737

Greetings,

I am writing the Qt app, which receives the data over a Bluetooth connection. The data format is as following sensor_1,sensor_2,Sensor_3,\r\n. How the received data In QBytearray can be split into relevant variables without losing the data being received continuously.

Best regards,
Ahsan

JonB

@ahsan737
You can split a QByteArray into a list on a character via QList<QByteArray> QByteArray::split(char sep) const. Or just use int QByteArray::indexOf(char ch, int from = 0) const. (Or convert to QString and use corresponding methods, if appropriate.) Buffer received data as necessary. This will have no impact on the continuous arrival of data.

SGaist

Hi,

Cumulate the data until you have a full frame and then extract it and parse it.

ahsan737

@JonB @SGaist

I've tried this code to buffer incoming data, but it shows the error Segmentation Fault.
How can I eliminate this error?

incoming data: "315,317,1926,\r\n316,3"

data is continuously being received, but currently, Bluetooth <characteristic changed> has received this chunk.

void MainWindow::dataReceived(QByteArray data) 
{
buffer.setBuffer(&data);
buffer.open(QIODevice::ReadWrite);
while (buffer.canReadLine())
  {
     QByteArray line = buffer.readLine().trimmed();   //reading data from bluetooth channel
     QString list= QString::fromUtf8(line.constData(), line.length());    //reading incoming ASCII data
     
     ui->receivedTextEdit->append(list);
     ui->receivedTextEdit->append("\n");
  }
}

JonB

@ahsan737 said in How to: Tokenization (Splitting) QBytearray data?:

but it shows the error Segmentation Fault.

Run from debugger and look at the stack trace window.

ahsan737

@JonB
This is the stack trace screenshot

JonB

@ahsan737
Who knows. This code no longer is the same as what you posted earlier. You don't show anything about buffer is. I don't know about the scope of your data. You do not verify the return result from buffer.open(). And so on.

You can see for yourself from the stack trace that it's having trouble seeking for the `readLine(). You can use debugger to have a look at what's in the variables.

ahsan737

@JonB codes are the same, I just have removed while loop because it wasn't making any difference, the error is being caused at readLine.