Converting big number to base 24

[MartinD]

I want to display array of 20 bytes as a number with base 24. Can Qt do this conversion?

[Ni.Sumi]

@MartinD

yes, it possible in Qt. int QString::toInt(bool *ok = Q_NULLPTR, int base = 10) const

http://doc.qt.io/qt-5/qstring.html#toInt

[MartinD]

My big number has 160 bits. QString.toInt can't handle it.

[Ni.Sumi]

@MartinD

you can use ::ToULongLong , ::toULong ..

[MartinD]

Still only 64 bits...

[kshegunov]

@MartinD
Hi,
It's very basic math:

BigIntType x;
QString number;

while (x != 0)  {
    char reminder = x % 24;
    x /= 24;

    number += reminder < 10 ? '0' + reminder : 'A' + reminder - 10;
}

std::reverse(number.begin(), number.end());

Your number system is bad, chose one that's a power of 2, so you can skip the divisions and use bit-wise operations instead.

Kind regards.

[MartinD]

I used the class in http://stackoverflow.com/questions/4735622/convert-large-hex-string-to-decimal-string . Nice code, easy to implement base 24 conversions.

[VRonin]

Boost multiprecision is probably the most ready available bignum library you could use for this task. just use cpp_int as BigIntType in @kshegunov 's algorithm