Fast way to convert a binary number to a decimal number

Question

I have to convert a binary number like for example unsigned int bin_number = 10101010 into its decimal representation (i.e. 170) as quickly as possible

Answer 1

Since C++11 (even if C++11 is more limited than C++14 in that regard), function can be constexpr so avoid necessity of template to have compile time value.

Here a version C++14 compatible:

constexpr unsigned binary_to_decimal(unsigned num)
{
    unsigned res = 0;

    while (num)
    {
        res = 10 * res + num % 10;
        num /= 10;
    }
    return res;
}

And for literals, you can even use binary literals since C++14:

0b1010'1010 // or 0b10101010 without separator