Src := NewReadFileStream(ReadString(_Data, _data_SrcFileName, ''));
  if Src.Handle = INVALID_HANDLE_VALUE then
  begin
    Err := ERROR_OPEN_SRC_FILE;
    goto finish;
  end;
  
  Fn := ReadString(_Data, _data_DstFileName, '');
  Dst := NewFileStream(Fn, ofOpenWrite or ofCreateAlways or ofShareDenyWrite);
  if Dst.Handle = INVALID_HANDLE_VALUE then
  begin
    Fn := '';
    Err := ERROR_OPEN_DST_FILE;
    goto finish;
  end;
  
  Count := Src.Size;