[#210] Do not allocate for the C++ Sample

iceoryx2-ffi/cxx/include/iox2/publisher.hpp

@@ -169,12 +169,12 @@ template <ServiceType S, typename Payload, typename UserHeader>
 inline auto Publisher<S, Payload, UserHeader>::loan_uninit()
     -> iox::expected<SampleMut<S, Payload, UserHeader>, PublisherLoanError> {
     auto* ref_handle = iox2_cast_publisher_ref_h(m_handle);
-    iox2_sample_mut_h sample_handle {};
+    SampleMut<S, Payload, UserHeader> sample;
 
-    auto result = iox2_publisher_loan(ref_handle, nullptr, &sample_handle);
+    auto result = iox2_publisher_loan(ref_handle, &sample.m_sample, &sample.m_handle);
 
     if (result == IOX2_OK) {
-        return iox::ok(SampleMut<S, Payload, UserHeader>(sample_handle));
+        return iox::ok(std::move(sample));
     }
 
     return iox::err(iox::into<PublisherLoanError>(result));

iceoryx2-ffi/cxx/include/iox2/sample.hpp

@@ -32,6 +32,7 @@ namespace iox2 {
 ///
 /// DO NOT MOVE THE SAMPLE INTO ANOTHER THREAD!
 template <ServiceType, typename Payload, typename UserHeader>
+// NOLINTNEXTLINE(cppcoreguidelines-pro-type-member-init,hicpp-member-init) 'm_sample' is not used directly but only via the initialized 'm_handle'; furthermore, it will be initialized on the call site
 class Sample {
   public:
     Sample(Sample&& rhs) noexcept;
@@ -64,17 +65,14 @@ class Sample {
     template <ServiceType, typename, typename>
     friend class Subscriber;
 
-    explicit Sample(iox2_sample_h handle);
+    // The sample is defaulted since both members are initialized in Subscriber::receive
+    explicit Sample() = default;
     void drop();
 
+    iox2_sample_t m_sample;
     iox2_sample_h m_handle { nullptr };
 };
 
-template <ServiceType S, typename Payload, typename UserHeader>
-inline Sample<S, Payload, UserHeader>::Sample(iox2_sample_h handle)
-    : m_handle { handle } {
-}
-
 template <ServiceType S, typename Payload, typename UserHeader>
 inline void Sample<S, Payload, UserHeader>::drop() {
     if (m_handle != nullptr) {
@@ -83,16 +81,24 @@ inline void Sample<S, Payload, UserHeader>::drop() {
     }
 }
 
+// NOLINTNEXTLINE(cppcoreguidelines-pro-type-member-init,hicpp-member-init) m_sample will be initialized in the move assignment operator
 template <ServiceType S, typename Payload, typename UserHeader>
 inline Sample<S, Payload, UserHeader>::Sample(Sample&& rhs) noexcept {
     *this = std::move(rhs);
 }
 
+namespace internal {
+extern "C" {
+void iox2_sample_move(iox2_sample_t*, iox2_sample_t*, iox2_sample_h*);
+}
+} // namespace internal
+
 template <ServiceType S, typename Payload, typename UserHeader>
 inline auto Sample<S, Payload, UserHeader>::operator=(Sample&& rhs) noexcept -> Sample& {
     if (this != &rhs) {
         drop();
-        m_handle = std::move(rhs.m_handle);
+
+        internal::iox2_sample_move(&rhs.m_sample, &m_sample, &m_handle);
         rhs.m_handle = nullptr;
     }
 

iceoryx2-ffi/cxx/include/iox2/sample_mut.hpp

@@ -47,6 +47,7 @@ namespace iox2 {
 ///
 /// DO NOT MOVE THE SAMPLE INTO ANOTHER THREAD!
 template <ServiceType S, typename Payload, typename UserHeader>
+// NOLINTNEXTLINE(cppcoreguidelines-pro-type-member-init,hicpp-member-init) 'm_sample' is not used directly but only via the initialized 'm_handle'; furthermore, it will be initialized on the call site
 class SampleMut {
   public:
     SampleMut(SampleMut&& rhs) noexcept;
@@ -100,17 +101,15 @@ class SampleMut {
     template <ServiceType ST, typename PayloadT, typename UserHeaderT>
     friend auto send_sample(SampleMut<ST, PayloadT, UserHeaderT>&& sample) -> iox::expected<size_t, PublisherSendError>;
 
-    explicit SampleMut(iox2_sample_mut_h handle);
+    // The sample is defaulted since both members are initialized in Subscriber::receive
+    explicit SampleMut() = default;
     void drop();
 
+    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-member-init,hicpp-member-init) will not be accessed directly but only via m_handle and will be set together with m_handle
+    iox2_sample_mut_t m_sample;
     iox2_sample_mut_h m_handle { nullptr };
 };
 
-template <ServiceType S, typename Payload, typename UserHeader>
-inline SampleMut<S, Payload, UserHeader>::SampleMut(iox2_sample_mut_h handle)
-    : m_handle { handle } {
-}
-
 template <ServiceType S, typename Payload, typename UserHeader>
 inline void SampleMut<S, Payload, UserHeader>::drop() {
     if (m_handle != nullptr) {
@@ -119,16 +118,24 @@ inline void SampleMut<S, Payload, UserHeader>::drop() {
     }
 }
 
+// NOLINTNEXTLINE(cppcoreguidelines-pro-type-member-init,hicpp-member-init) m_sample will be initialized in the move assignment operator
 template <ServiceType S, typename Payload, typename UserHeader>
 inline SampleMut<S, Payload, UserHeader>::SampleMut(SampleMut&& rhs) noexcept {
     *this = std::move(rhs);
 }
 
+namespace internal {
+extern "C" {
+void iox2_sample_mut_move(iox2_sample_mut_t*, iox2_sample_mut_t*, iox2_sample_mut_h*);
+}
+} // namespace internal
+
 template <ServiceType S, typename Payload, typename UserHeader>
 inline auto SampleMut<S, Payload, UserHeader>::operator=(SampleMut&& rhs) noexcept -> SampleMut& {
     if (this != &rhs) {
         drop();
-        m_handle = std::move(rhs.m_handle);
+
+        internal::iox2_sample_mut_move(&rhs.m_sample, &m_sample, &m_handle);
         rhs.m_handle = nullptr;
     }
 

iceoryx2-ffi/cxx/include/iox2/subscriber.hpp

@@ -132,13 +132,14 @@ template <ServiceType S, typename Payload, typename UserHeader>
 inline auto Subscriber<S, Payload, UserHeader>::receive() const
     -> iox::expected<iox::optional<Sample<S, Payload, UserHeader>>, SubscriberReceiveError> {
     auto* ref_handle = iox2_cast_subscriber_ref_h(m_handle);
+
+    Sample<S, Payload, UserHeader> sample;
     iox2_sample_h sample_handle {};
-    auto result = iox2_subscriber_receive(ref_handle, nullptr, &sample_handle);
+    auto result = iox2_subscriber_receive(ref_handle, &sample.m_sample, &sample.m_handle);
 
     if (result == IOX2_OK) {
-        if (sample_handle != nullptr) {
-            return iox::ok(
-                iox::optional<Sample<S, Payload, UserHeader>>(Sample<S, Payload, UserHeader>(sample_handle)));
+        if (sample.m_handle != nullptr) {
+            return iox::ok(iox::optional<Sample<S, Payload, UserHeader>>(std::move(sample)));
         }
         return iox::ok(iox::optional<Sample<S, Payload, UserHeader>>(iox::nullopt));
     }