Qt/C++ Convert QString to Decimal

How Can I convert QString to decimal ?

In C# code it look like that:

public static decimal ConvertToDecimal(string tekst, bool upperOnly)
{
decimal num = 0m;
decimal num2 = 1m;
string text = upperOnly ? "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" : "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234";
int i = tekst.Length - 1;
while (i >= 0)
{
    num += text.IndexOf(tekst[i]) * num2;
    i--;
    num2 *= text.Length;
}
return num;
}