Problem download bmp file

Hi, the problem is:

after filled int table with read dataset into... and check that this table is full i use ws_download to create local file, the problem is that the file is created but is of 0 kb. Why?

REFRESH tab_bmp.

DO.

READ DATASET file_def INTO tab_bmp-text.

APPEND tab_bmp.

IF sy-subrc NE 0.

EXIT.

ENDIF.

ENDDO.

CLOSE DATASET file_def.

CONCATENATE 'C:\' cid_open '.bmp' INTO file_dest.

CALL FUNCTION 'WS_DOWNLOAD'

EXPORTING

• BIN_FILESIZE = ' '

• CODEPAGE = ' '

filename = file_dest

filetype = 'BIN'

• MODE = ' '

• WK1_N_FORMAT = ' '

• WK1_N_SIZE = ' '

• WK1_T_FORMAT = ' '

• WK1_T_SIZE = ' '

• COL_SELECT = ' '

• COL_SELECTMASK = ' '

• NO_AUTH_CHECK = ' '

• IMPORTING

• FILELENGTH =

TABLES

data_tab = tab_bmp

• FIELDNAMES =

• EXCEPTIONS

• FILE_OPEN_ERROR = 1

• FILE_WRITE_ERROR = 2

• INVALID_FILESIZE = 3

• INVALID_TYPE = 4

• NO_BATCH = 5

• UNKNOWN_ERROR = 6

• INVALID_TABLE_WIDTH = 7

• GUI_REFUSE_FILETRANSFER = 8

• CUSTOMER_ERROR = 9

• OTHERS = 10

.

IF sy-subrc <> 0.

• MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO

• WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.

ENDIF.

thanks for answers.