file_id	IN:	File identifier returned by Hopen
	desc_buf	OUT:	The buffer allocated to hold the description
	buf_len	IN:	Size of the buffer allocated to hold the description
	isfirst	IN:	Determines the description to be retrieved

	Purpose	Reads the next file description.
	Return value	Returns the length of the file description if successful and FAIL (or -1) otherwise.
	Description	If isfirst is 0, DFANgetfds gets the next file description from an HDF file. For example, if there are three file descriptions in a file, three successive calls to DFANgetfds will get all three descriptions. If isfirst is 1, DFANgetfds gets the first file description.
		Valid values for isfirst are: 1 to read the first description and 0 to read the next description.

	FORTRAN	integer function dagfds(file_id, desc_buf, buf_len, isfirst)
		integer file_id, buf_len, isfirst
		character*(*) desc_buf