How to convert a Qstring to QByteArray Such that to read hex values from a file

Indicoder

i need to read a hex value from a file and use it my file has hex values and integer 0 0x05 1 0xf5 2 0x00 3 0x00 4 0x02 and so on...i need to read it from the file and use it to convert those hex value.
my code is something like this

void MyUDP::HelloUDP()
{
int i;
QFile file("2.txt");
if(!file.exists()) qDebug() << "not found file";
file.open(QIODevice::ReadWrite);
QByteArray Data;
// read whole content
QByteArray content = file.readAll();
// extract words
QByteArray a=content.split(" ");
for(i=0;i<list.size();i++)
{
Data.append(list[i]);
}
// Data.append(0x05);
//Data.append(0xf5);need something equivalent to this but read many values from file
file.close();
// Sends the datagram datagram
// to the host address and at port.
// qint64 QUdpSocket::writeDatagram(const QByteArray & datagram,
// const QHostAddress & host, quint16 port)
socket->writeDatagram(Data, QHostAddress::LocalHost, 1234);
}

void MyUDP::readyRead()
{
//unsigned int inp0,inp1,inp2,inp3;
//int pos0,pos1,pos2,pos3;
int temp;
float roll;
QByteArray buffer;
//unsigned int a;
buffer.resize(socket->pendingDatagramSize());
QHostAddress sender;
quint16 senderPort;
socket->readDatagram(buffer.data(), buffer.size(),&sender, &senderPort);
//a=static_cast<unsigned char>(buffer[1]);
//scanf(buffer.constData(),"%d\t%x\t%d\t%x\t%d\t%x\t%d\t%x",&pos0,&inp0,&pos1,&inp1,&pos2,&inp2,&pos3,&inp3);
temp=(static_cast<unsigned char>(buffer[0]) << 8) | static_cast<unsigned char>(buffer[1]);
roll=temp*0.01;
//printf("%f",roll);
qDebug() << "Message from: " << sender.toString();
qDebug() << "Message port: " << senderPort;
qDebug() << "Message: " << roll; // it should print 15.25 if my file values are 0x05 0xf5 using buffer[0] and buffer[1] respectively

}

Christian Ehrlicher

So what do you want to achieve? Send the file content via udp?

Indicoder

yes send it through udp and and the file content should not be in string it should take it as a hex value

Christian Ehrlicher

So just read the content with QFile::readAll() and send it with QUdpSocket::writeDatagram.
There is no need to convert the data to hex string representation.

Indicoder

when i send it through readAll() if file contains 0x05 it just prints 0 for buffer[0] and buffer[1] prints x and so on....but i need 0x05 as a whole

Christian Ehrlicher

How do you print it out? 0x05 is a non-printable character. If you want to print the values out for e.g. debuggin you can for example use QByteArray::toHex() or similar

Indicoder

void MyUDP::HelloUDP()
{
int i;
QFile file("2.txt");
if(!file.exists()) qDebug() << "not found file";
file.open(QIODevice::ReadWrite);

 QByteArray Data = file.readLine();

 //QByteArray Data;
 //Data.append(0x05);
 //Data.append(0xF5);

 file.close();

 socket->writeDatagram(Data, QHostAddress::LocalHost, 1234);

}

void MyUDP::readyRead()
{
//unsigned int inp0,inp1,inp2,inp3;
//int pos0,pos1,pos2,pos3;
int temp;
float roll;
QByteArray buffer;
//unsigned int a;
buffer.resize(socket->pendingDatagramSize());
QHostAddress sender;
quint16 senderPort;
socket->readDatagram(buffer.data(), buffer.size(),&sender, &senderPort);
temp=(static_cast<unsigned char>(buffer[0]) << 8) | static_cast<unsigned char>(buffer[1]);
roll=temp*0.01;
//printf("%f",roll);
qDebug() << "Message from: " << sender.toString();
qDebug() << "Message port: " << senderPort;
qDebug() << "Message: " << roll;

}
file contains: 0x05 0xF5

if i run the above code as u said reading it from the file its roll output is coming as 124.5 as buffer[0] is 0 and buffer [1] is x
but when i use manual sending the data by Data.append(0x05) ; Data.append(0xF5) then buffer[0] is 0x05 and buffer[1] is 0xF5 and roll output is 15.25 which is correct

basically i want the second point output using the first method through file

can you help me out in more detail please

Christian Ehrlicher

QFile::readLine() reads a line (which ends with \0) - see documentation. You want QFile::read(int) or QFile::readAll().

Indicoder

sorry i tried with readAll() it was the same

Christian Ehrlicher

@Indicoder said in How to convert a Qstring to QByteArray Such that to read hex values from a file:

sorry i tried with readAll() it was the same

So you should output via qDebug() and toHex() to see what you've actually read from the file