Function SHGetDiskFreeSpaceExA 

pub unsafe extern "system" fn SHGetDiskFreeSpaceExA(
    pszdirectoryname: PCSTR,
    pulfreebytesavailabletocaller: *mut u64,
    pultotalnumberofbytes: *mut u64,
    pultotalnumberoffreebytes: *mut u64,
) -> BOOL