Question

I need help from some one to convert the following line of code from ruby to qt c++:

KEY = %w(30 81 9F 30 0D 06 09 2A 86 48 86 F7 0D 01 01 01 05 00 03 81 8D 00).map{|s| s.hex}.pack(‘C*’)

Answer 1

QByteArray key = QByteArray::fromHex(QByteArray("30 81 9F 30 0D 06 09 2A 86 48 86 F7 0D 01 01 01 05 00 03 81 8D 00").replace(' ', QString()));

Quick explanation:

QByteArray("30 81 9F 30 0D 06 09 2A 86 48 86 F7 0D 01 01 01 05 00 03 81 8D 00")

creates temporary QByteArray with your key as string

.replace(' ', QString())

removes all spaces in temporary QByteArray, so it contains only characters 0..F

QByteArray::fromHex()

converts hex-encoded QByteArray into QByteArray containing unsigned 8-bit integers (i.e. C++ char type). It means that it takes every pair of hex digits from original QByteArray ( for example “41”) and converts it to integer (“41” will be converted to 65 = 4*16 + 1) and appends this value into new QByteArray.

If you need key as a “const char *” you can use QByteArray::constData() method, but you have to remember that the pointer returned by this method is valid only as long as original QByteArray is valid (quote from documentation: “as long as the byte array isn’t reallocated or destroyed”). So if you need to store the key data, keep it as QByteArray or make a copy of const char * returned by constData().