anchor.diff:    int _position;
     int _filePosition;
     int _fileLength;
  +  bool _activeFillBufferCall = false;
   }
   
   
  
positive.code:         _data = _data.getRange(0, read);
        }
        _position = 0;
  
        if (_fileLength == _filePosition) {
          _closeFile();
        }
        _checkScheduleCallbacks();
      });
    }
  
  
negative.code:     List<int> result;
      if (_position == 0 && bytesToRead == _data.length) {
        result = _data;
        _data = const [];
      } else {
        result = new Uint8List(bytesToRead);
        result.setRange(0, bytesToRead, _data, _position);
  