zero_higher_bits.hpp

#ifndef PASTELSYS_ZERO_HIGHER_BITS_HPP
#define PASTELSYS_ZERO_HIGHER_BITS_HPP

#include "pastel/sys/bit/zero_higher_bits.h"

namespace Pastel
{

    template <typename Integer>
    Integer zeroHigherBits(const Integer& that)
    {
        if (zero(that))
        {
            return that;
        }

        // u     = x...x10...0
        // u - 1 = x...x01...1
        // u ^ (u - 1) = 0...011...1
        // 
        // (u ^ (u - 1)) >> 1 = 0...001...1

        Integer a = (that ^ (that - 1));
        return a ^ (a >> 1);
    }

}

#endif