Convert QByteArray from big endian to little endian

Question

I think I’m a kind of at a loss here. I trying such a simple thing, I can’t believe that there is nothing build-in Qt (using Qt 5.6.2). I try to convert the data inside a QByteArray from big endian to little endian. Always starts with the same test QByteArray like this.

QByteArray value;
value.append(0x01);
value.append(0x02);
value.append(0x03);
qDebug() << "Original value is: " << value.toHex(); // “010203” like expected

What I need is the little endian, which means the output should be “030201”. Is there any build in thing so far in the Qt Framework? I don’t find one. What I tried so far

// Try with build in QtEndian stuff
QByteArray test = qToLittleEndian(value);
qDebug() << "Test value is: " << test.toHex(); // 010203

// Try via QDataStream
QByteArray data;
QDataStream out(&data, QIODevice::ReadWrite);
out.setByteOrder(QDataStream::LittleEndian);
out << value;
qDebug() << "Changed value is: " << data.toHex(); // "03000000010203"

Any good idea? Or do I really need to shift hands by hand? Found nothing helpfull on SO or on google or maybe ask the wrong question...

Answer 1

It sounds like you want to reverse the array, rather than manipulate the endianness of any of the multi-byte types inside the array. The standard library has a solution for this:

QByteArray arr;
std::reverse(arr.begin(), arr.end());
// arr is now in reversed order