rounding_duration_cast.hpp

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#pragma once
 
namespace fiber
{
 
    enum class RoundingMethod{
        Up,
        Down,
        Nearest,
    };

    template<class ToDuration, RoundingMethod rounding_type = RoundingMethod::Up, class Rep = unsigned int, fiber::CRatio Period = std::ratio<1>>
    constexpr ToDuration rounding_duration_cast( const std::chrono::duration<Rep, Period>& d ){
        using conversion = typename std::ratio_divide<Period, typename ToDuration::period>::type;
        if constexpr (rounding_type == RoundingMethod::Nearest){
            if constexpr (std::is_unsigned_v<Rep>){
                const auto mul = d.count() * conversion::num;
                const auto round = mul + conversion::den/2;
                const auto new_count = round / conversion::den;
                ToDuration result(static_cast<ToDuration::rep>(new_count));
                return result;
            }else{
                const auto mul = d.count() * conversion::num;
                const auto round =  ((d.count() > 0) ? (mul + conversion::den/2) : (mul - conversion::den/2));
                const auto new_count = round / conversion::den;
                ToDuration result(static_cast<ToDuration::rep>(new_count));
                return result;
            }
        }else if constexpr (rounding_type == RoundingMethod::Up){
            if constexpr (std::is_unsigned_v<Rep>){
                const auto mul = d.count() * conversion::num;
                const auto round =  mul + (conversion::den-1);
                const auto new_count = round / conversion::den;
                ToDuration result(static_cast<ToDuration::rep>(new_count));
                return result;
            }else{
                const auto mul = d.count() * conversion::num;
                const auto round =  ((d.count() > 0) ? (mul + (conversion::den-1)) : (mul - (conversion::den-1)));
                const auto new_count = round / conversion::den;
                ToDuration result(static_cast<ToDuration::rep>(new_count));
                return result;
            }
        }else /*if constexpr (rounding_type == RoundingMethod::Down)*/{
            const auto mul = d.count() * conversion::num;
            const auto round = mul;
            const auto new_count = round / conversion::den;
            ToDuration result(static_cast<ToDuration::rep>(new_count));
            return result;
        }
        
    }
    
} // namespace fiber