/// <summary>
 /// ctor for filesystem that comes from within a volume
 /// </summary>
 /// <param name="volume"></param>
 /// <param name="fstype"></param>
 internal FileSystem(Volume volume, FileSystemType fstype)
 {
     this._image  = volume.VolumeSystem.DiskImage;
     this._volume = volume;
     this._handle = NativeMethods.tsk_fs_open_vol(volume._ptr_volinfo, fstype);
     this._struct = _handle.GetStruct();
 }
 /// <summary>
 /// ctor for when there is no volume system (like thumb drives, floppies, etc. things with no MBR.. they just start with the filesystem)
 /// </summary>
 /// <param name="diskImage"></param>
 /// <param name="type"></param>
 /// <param name="offset"></param>
 internal FileSystem(DiskImage diskImage, FileSystemType type, long offset)
 {
     this._image  = diskImage;
     this._volume = null; //no luck on this, no volume system!
     this._handle = diskImage._handle.OpenFileSystemHandle(type, offset);
     this._struct = _handle.GetStruct();
 }