Convert Union to QByteArray and vice-versa using QUdpSocket in Qt

Question

I have one Union like below

#define no_of_bits 240
#define word_size 16

struct bits
{
    unsigned short int bit1:1;
    unsigned short int bit2:1;
    unsigned short int bit3:1;
    unsigned short int bit4:1;
    unsigned short int bit5:1;
    unsigned short int bit6:1;
    unsigned short int bit7:1;
    unsigned short int bit8:1;
    unsigned short int bit9:1;
    unsigned short int bit10:1;
    unsigned short int bit11:1;
    unsigned short int bit12:1;
    unsigned short int bit13:1;
    unsigned short int bit14:1;
    unsigned short int bit15:1;
    unsigned short int bit16:1;
};

union myData
{
        unsigned short int data[no_of_bits/word_size];
        struct bits word[no_of_bits/word_size];
};

I want to convert myData union into a QByteArray so that I can send it through socket using QUdpSocket using writeDatagram() function. So first tell me how can I convert this into QByteArray.

Next thing is that, On the receiver side how can I convert the QByteArray into the this Union myData again.

Answer 1

Use QByteArray constructor or QByteArray::fromRawData.

See example for converting to QByteArray:

#include <QCoreApplication>
#include <QByteArray>


#define no_of_bits 240
#define word_size 16

struct bits
{
    unsigned short int bit1:1;
    unsigned short int bit2:1;
    unsigned short int bit3:1;
    unsigned short int bit4:1;
    unsigned short int bit5:1;
    unsigned short int bit6:1;
    unsigned short int bit7:1;
    unsigned short int bit8:1;
    unsigned short int bit9:1;
    unsigned short int bit10:1;
    unsigned short int bit11:1;
    unsigned short int bit12:1;
    unsigned short int bit13:1;
    unsigned short int bit14:1;
    unsigned short int bit15:1;
    unsigned short int bit16:1;
};

union myData
{
        unsigned short int data[no_of_bits/word_size];
        struct bits word[no_of_bits/word_size];
};



int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    myData data;

    // Variant 1  (no copy data)
    auto byteArray = QByteArray::fromRawData(reinterpret_cast<const char*>(&data), sizeof(data));

    // Variant 2  (copy data)
    QByteArray byteArray2(reinterpret_cast<const char*>(&data), sizeof(data));

    return a.exec();
}

Convert from QByteArray:

assert(byteArray.size() == sizeof(data));
memcpy(&data, byteArray.data(), sizeof(data)); // Copy

// OR

assert(byteArray.size() == sizeof(data));
myData* data2 = reinterpret_cast<myData*>(byteArray.data()); // No copy

Actually, you can call writeDatagram directly:

QUdpSocket socket;
socket.writeDatagram(reinterpret_cast<const char*>(&data), sizeof(data), QHostAddress("127.0.0.1"), 1234);