2.2 整数对齐

// 向上大小对齐
 template <typename T>
inline constexpr T alignup(T num, T base) { return (num + base - 1) & (~(base - 1)); }
// 向下大小对齐
template <typename T>
inline constexpr T aligndown(T num, T base) { return (num & ~(base - 1)); }