Function BCryptExportKey 

pub unsafe extern "system" fn BCryptExportKey(
    hkey: BCRYPT_KEY_HANDLE,
    hexportkey: BCRYPT_KEY_HANDLE,
    pszblobtype: PCWSTR,
    pboutput: *mut u8,
    cboutput: u32,
    pcbresult: *mut u32,
    dwflags: u32,
) -> NTSTATUS