feat: add cookie-related API to Message (#491)

Add `Message::getCookie()` and `MethodReply::getReplyCookie()` functions, based on underlying sd-bus cookie functions. They can be useful when pairing method call messages and method call reply messages.

---------

Co-authored-by: Dylan Howey <dylan.howey@evgo.com>
Co-authored-by: Stanislav Angelovič <stanislav.angelovic@protonmail.com>

tests/integrationtests/DBusMethodsTests.cpp

@@ -286,6 +286,14 @@ TYPED_TEST(SdbusTestObject, CanAccessAssociatedMethodCallMessageInMethodCallHand
     ASSERT_THAT(this->m_adaptor->m_methodName, Eq("doOperation"));
 }
 
+TYPED_TEST(SdbusTestObject, ProvidesSerialInMethodCallAndMethodReplyMessage)
+{
+    auto reply = this->m_proxy->doOperationOnBasicAPILevel(ANY_UNSIGNED_NUMBER);
+
+    ASSERT_THAT(this->m_proxy->m_methodCallMsg->getCookie(), Gt(0));
+    ASSERT_THAT(reply.getReplyCookie(), Eq(this->m_proxy->m_methodCallMsg->getCookie())); // Pairing method reply with method call message
+}
+
 TYPED_TEST(SdbusTestObject, CanAccessAssociatedMethodCallMessageInAsyncMethodCallHandler)
 {
     this->m_proxy->doOperationAsync(10); // This will save pointer to method call message on server side

tests/integrationtests/TestFixture.h

@@ -50,6 +50,8 @@
 
 namespace sdbus { namespace test {
 
+inline const uint32_t ANY_UNSIGNED_NUMBER{123};
+
 class BaseTestFixture : public ::testing::Test
 {
 public:

tests/integrationtests/TestProxy.cpp

@@ -113,6 +113,16 @@ uint32_t TestProxy::doOperationWithTimeout(const std::chrono::microseconds &time
     return result;
 }
 
+MethodReply TestProxy::doOperationOnBasicAPILevel(uint32_t param)
+{
+    auto methodCall = getProxy().createMethodCall(test::INTERFACE_NAME, MethodName{"doOperation"});
+    methodCall << param;
+
+    m_methodCallMsg = std::make_unique<MethodCall>(methodCall);
+
+    return getProxy().callMethod(methodCall);
+}
+
 sdbus::PendingAsyncCall TestProxy::doOperationClientSideAsync(uint32_t param)
 {
     return getProxy().callMethodAsync("doOperation")

tests/integrationtests/TestProxy.h

@@ -95,6 +95,7 @@ protected:
 public:
     void installDoOperationClientSideAsyncReplyHandler(std::function<void(uint32_t res, std::optional<sdbus::Error> err)> handler);
     uint32_t doOperationWithTimeout(const std::chrono::microseconds &timeout, uint32_t param);
+    MethodReply doOperationOnBasicAPILevel(uint32_t param);
     sdbus::PendingAsyncCall doOperationClientSideAsync(uint32_t param);
     [[nodiscard]] sdbus::Slot doOperationClientSideAsync(uint32_t param, sdbus::return_slot_t);
     std::future<uint32_t> doOperationClientSideAsync(uint32_t param, with_future_t);
@@ -121,6 +122,7 @@ public: // for tests
     std::function<void(uint32_t res, std::optional<sdbus::Error> err)> m_DoOperationClientSideAsyncReplyHandler;
     std::function<void(const sdbus::InterfaceName&, const std::map<PropertyName, sdbus::Variant>&, const std::vector<PropertyName>&)> m_onPropertiesChangedHandler;
 
+    std::unique_ptr<const MethodCall> m_methodCallMsg;
     std::unique_ptr<const Message> m_signalMsg;
     SignalName m_signalName;
 };