file_id	IN:	File identifier returned by Hopen
	isfirst	IN:	Determines the description the retrieved length information applies to

	Purpose	Returns the length of a file description.
	Return value	Returns the length of the file description if successful and FAIL (or -1) otherwise.
	Description	When DFANgetfdslen is first called for a given file, it returns the length of the first file description. In order to get the lengths of successive file descriptions, you must call DFANgetfds between calls to DFANgetfdslen. Successive calls to DFANgetfdslen without calling DFANgetfds between them will return the length of the same file description.
		Valid values for isfirst are: 1 to read the length of the first description and 0 to read the length of the next description.

	FORTRAN	integer function dagfdsl(file_id, isfirst)
		integer file_id, isfirst