public static extern int avio_read_dir(AVIODirContext* @s, AVIODirEntry** @next);
 public static extern int avio_close_dir(AVIODirContext** @s);
 public static extern int avio_open_dir(AVIODirContext** @s, [MarshalAs(UnmanagedType.LPStr)] string @url, AVDictionary** @options);