NitrokeyManager: Also return serial number as u32

This patch adds the get_serial_number_as_u32 method to NitrokeyManager.
It returns the serial number as a 32-bit unsigned integer.  Previously,
we only returned it as a string generated from the integer value,
get_serial_number.

While get_serial_number returns an empty string if no device is
connected and "NA" if an unknown model is connected, the new method
throws a DeviceNotConnected exception in the first case and returns zero
in the second case as we cannot express the three states in one integer
return value.

1 files changed, 4 insertions, 0 deletions

diff --git a/unittest/test_offline.cc b/unittest/test_offline.cc
index 320ad48..3ca3905 100644
--- a/unittest/test_offline.cc
+++ b/unittest/test_offline.cc
@@ -67,6 +67,10 @@ TEST_CASE("Test C++ side behaviour in offline", "[fast]") {
   REQUIRE(serial_number.empty());
 
   REQUIRE_THROWS_AS(
+    i->get_serial_number_as_u32(), DeviceNotConnected
+  );
+
+  REQUIRE_THROWS_AS(
     i->get_status(), DeviceNotConnected
   );