How to change the byte order of a boost::multiprecision::cpp_int and store in a QByteArry

[Infinity]

I have to change the byte order of a boost::multiprecision::cpp_int and store it in a QByteArry.

That is how I do it for quint64:

QByteArray MyLongNumber::intToByteArray(QDataStream::ByteOrder byteOrder)
{
    // Convert the int to bianry QByteArray according to byteOrder (QDataStream::BigEndian | QDataStream::LittleEndian)

    QByteArray intByteArray;
    QDataStream intDataStream(&intByteArray, QIODevice::WriteOnly);

    intDataStream.setByteOrder(byteOrder);
    intDataStream << m_intNumber;

    return intByteArray;
}

How can I do it for a boost::multiprecision::cpp_int. I tried it like this:

QByteArray MyBigNumber::cppIntToByteArray(QDataStream::ByteOrder byteOrder)
{
    // Convert the int to bianry QByteArray according to byteOrder (QDataStream::BigEndian | QDataStream::LittleEndian)

    boost::multiprecision::cpp_int m_cppInt(4000000000000000);

    QByteArray intByteArray;
    QDataStream intDataStream(&intByteArray, QIODevice::WriteOnly);

    intDataStream.setByteOrder(byteOrder);
    intDataStream << m_cppInt;

    return intByteArray;
}

But that doesn't work. How can I do that?

[SGaist]

Hi,

In what does it not work ?
On what OS ?
With which compiler ?

[Kent-Dorfman]

How/why would QDataStream know anything about boost::multiprecision?

They are from different frameworks, so unless the intDataStream is taught how to handle
intDataStream << m_cppInt
the operation is going to be undefined. I think you'll need to look under the hood to see how boost stores its mutliprecision types before making any assumptions about compatibility with Qt.