BitField Class Wrapper

BitField.hpp

#include <cstdint>
#include <cstdlib>

template <class T = uint_least64_t, size_t size = 64, T first = 0, T last = first>
constexpr T genMask() {
    static_assert(first <= last, "");
    static_assert(first < size && last < size, "");
    return (1ULL << last) | ((1ULL << (last - first)) - 1ULL) << first;
}

template <class T = uint_least64_t, T first = 0, T last = first>
class BitField {
    T mask {genMask<T, sizeof(T) * 8, first, last>()};
    T negMask {~mask};
    T& value;

public:
    constexpr BitField(T& value) noexcept : value(value) {}
    constexpr operator T() const noexcept {
        return (this->value & mask) >> first;
    }
    BitField& operator = (T value) noexcept {
        this->value &= negMask | ((value << first) & mask);
        return *this;
    }
};