Signature:

      SUBROUTINE h5pget_virtual_filename_f(dcpl_id, index, name, hdferr, name_len)
        INTEGER(HID_T)  , INTENT(IN)  :: dcpl_id
        INTEGER(SIZE_T) , INTENT(IN)  :: index
        CHARACTER(LEN=*), INTENT(OUT) :: name
        INTEGER, INTENT(OUT)          :: hdferr
        INTEGER(SIZE_T), OPTIONAL     :: name_len

Optional parameters:

      name_len - The size of name needed to hold the filename. (OUT)

Inputs:

      dcpl_id - The identifier of the virtual dataset creation property list.
      index   - Mapping index.
                The value of index is 0 (zero) or greater and less than count
                (0 ≤ index < count), where count is the number of mappings
                returned by h5pget_virtual_count.

Outputs:

      name   - A buffer containing the name of the file containing the
               source dataset.
      hdferr - Returns 0 if successful and -1 if fails.