C#把一片非托管内存 拷贝到 另一片非托管内存

[DllImport("msvcrt.dll", EntryPoint = "memcpy", CallingConvention = CallingConvention.Cdecl, SetLastError = false)]
public static extern IntPtr memcpy(IntPtr dest, IntPtr src, UIntPtr count);
 

 public static Bitmap Clone(Bitmap src)
    {
        // get source image size
        int width = src.Width;
        int height = src.Height;

        // lock source bitmap data
        BitmapData srcData = src.LockBits(
        new Rectangle(0, 0, width, height),
        ImageLockMode.ReadWrite, src.PixelFormat);

        // create new image
        Bitmap dst = new Bitmap(width, height, src.PixelFormat);

        // lock destination bitmap data
        BitmapData dstData = dst.LockBits(
        new Rectangle(0, 0, width, height),
        ImageLockMode.ReadWrite, dst.PixelFormat);

        memcpy(dstData.Scan0, srcData.Scan0, new UIntPtr((uint)height * (uint)srcData.Stride));

        // unlock both images
        dst.UnlockBits(dstData);
        src.UnlockBits(srcData);        

        return dst;
    }