Function get_file_size 

pub unsafe extern "C" fn get_file_size(
    handle: ClientHandle,
    info: *mut CardGetFileSizeInputInfo,
    out: *mut FileSizeInfo,
) -> ErrorCode

Available on non-ag35 only.

Sends a command to the modem to retrieve the file type, file size(transparent files) or record size and record count (record based files).