在C++中,我们可以使用宏或constexpr(如C++11所说)。我们可以用 C# 做什么?
请参阅“无法声明...”评论了解上下文:
static class Constant
{
// we must ensure this is compile time const, have to calculate it from ground...
public const int SIZEOF_TEXUTRE_RGBA_U8C4_640x480 = 4 * sizeof(byte) * 640 * 480;
// Cannot declare compile time constant as following in C#
//public const int SIZEOF_TEXUTRE_RGBA_U8C4_640x480_2 = 4 * PixelType._8UC4.PixelSize() * 640 * 480;
}
public static class PixelTypeMethods
{
public static /*constexpr*/ int PixelSize(this PixelType type)
{
int value = (int)type;
int unit_size = value & 0xFF;
int unit_count = (value & 0xFF00) >> 8;
return unit_count * unit_size;
}
}
[Flags]
public enum PixelType
{
RGBA_8UC4 = RGBA | _8U | _C4,
/////////////////////////
RGBA = 1 << 16,
/////////////////////////
_8UC4 = _8U | _C4,
/////////////////////////
_C4 = 4 << 8,
/////////////////////////
_8U = sizeof(byte)
}
要声明常量 (
const
),分配的值需要是编译时常量。自动调用方法使其不再是编译时常量。
替代方法是使用
static readonly
:
public static readonly int SIZEOF_TEXUTRE_RGBA_U8C4_640x480_2 =
4 * PixelType._8UC4.PixelSize() * 640 * 480;