From 0cf2c2be8368ef8117467b9b47576a08389d00a0 Mon Sep 17 00:00:00 2001
From: Jeff Ithier <jeff@ithier.dev>
Date: Tue, 5 Nov 2024 19:55:06 +0100
Subject: [PATCH] [#490] Add trait to determine payload value type of any
 payload

---
 .../cxx/include/iox2/payload_info.hpp         | 31 +++++++++++++++++++
 .../include/iox2/port_factory_publisher.hpp   | 16 +++-------
 .../service_builder_publish_subscribe.hpp     | 13 ++------
 3 files changed, 38 insertions(+), 22 deletions(-)
 create mode 100644 iceoryx2-ffi/cxx/include/iox2/payload_info.hpp

diff --git a/iceoryx2-ffi/cxx/include/iox2/payload_info.hpp b/iceoryx2-ffi/cxx/include/iox2/payload_info.hpp
new file mode 100644
index 00000000..30f2634b
--- /dev/null
+++ b/iceoryx2-ffi/cxx/include/iox2/payload_info.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2024 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Apache Software License 2.0 which is available at
+// https://www.apache.org/licenses/LICENSE-2.0, or the MIT license
+// which is available at https://opensource.org/licenses/MIT.
+//
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#ifndef IOX2_PAYLOAD_INFO_HPP
+#define IOX2_PAYLOAD_INFO_HPP
+
+#include "iox/slice.hpp"
+
+namespace iox2 {
+
+template <typename T>
+struct PayloadInfo {
+    using TYPE = T;
+};
+
+template <typename T>
+struct PayloadInfo<iox::Slice<T>> {
+    using TYPE = typename iox::Slice<T>::ValueType;
+};
+
+} // namespace iox2
+#endif
diff --git a/iceoryx2-ffi/cxx/include/iox2/port_factory_publisher.hpp b/iceoryx2-ffi/cxx/include/iox2/port_factory_publisher.hpp
index 164f5a7e..47487992 100644
--- a/iceoryx2-ffi/cxx/include/iox2/port_factory_publisher.hpp
+++ b/iceoryx2-ffi/cxx/include/iox2/port_factory_publisher.hpp
@@ -17,6 +17,7 @@
 #include "iox/builder_addendum.hpp"
 #include "iox/expected.hpp"
 #include "iox2/internal/iceoryx2.hpp"
+#include "iox2/payload_info.hpp"
 #include "iox2/publisher.hpp"
 #include "iox2/service_type.hpp"
 #include "iox2/unable_to_deliver_strategy.hpp"
@@ -76,20 +77,13 @@ PortFactoryPublisher<S, Payload, UserHeader>::create() && -> iox::expected<Publi
             // The payload type used by the C API is always a [u8].
             // Thus need to convert from N to N * sizeof(payload).
             // TODO: Consider alignment... not aligning each element properly will impact performance
-            if constexpr (iox::IsSlice<Payload>::VALUE) {
-                iox2_port_factory_publisher_builder_set_max_slice_len(&m_handle,
-                                                                      value * sizeof(typename Payload::ValueType));
-            } else {
-                iox2_port_factory_publisher_builder_set_max_slice_len(&m_handle, value * sizeof(Payload));
-            }
+            iox2_port_factory_publisher_builder_set_max_slice_len(&m_handle,
+                                                                  value * sizeof(typename PayloadInfo<Payload>::TYPE));
         })
         .or_else([&]() {
             // Assume only one element if not otherwise specified
-            if constexpr (iox::IsSlice<Payload>::VALUE) {
-                iox2_port_factory_publisher_builder_set_max_slice_len(&m_handle, sizeof(typename Payload::ValueType));
-            } else {
-                iox2_port_factory_publisher_builder_set_max_slice_len(&m_handle, sizeof(Payload));
-            }
+            iox2_port_factory_publisher_builder_set_max_slice_len(&m_handle,
+                                                                  sizeof(typename PayloadInfo<Payload>::TYPE));
         });
     m_max_loaned_samples.and_then(
         [&](auto value) { iox2_port_factory_publisher_builder_set_max_loaned_samples(&m_handle, value); });
diff --git a/iceoryx2-ffi/cxx/include/iox2/service_builder_publish_subscribe.hpp b/iceoryx2-ffi/cxx/include/iox2/service_builder_publish_subscribe.hpp
index 4cf9a70b..757252a4 100644
--- a/iceoryx2-ffi/cxx/include/iox2/service_builder_publish_subscribe.hpp
+++ b/iceoryx2-ffi/cxx/include/iox2/service_builder_publish_subscribe.hpp
@@ -19,6 +19,7 @@
 #include "iox2/attribute_specifier.hpp"
 #include "iox2/attribute_verifier.hpp"
 #include "iox2/internal/iceoryx2.hpp"
+#include "iox2/payload_info.hpp"
 #include "iox2/port_factory_publish_subscribe.hpp"
 #include "iox2/service_builder_publish_subscribe_error.hpp"
 #include "iox2/service_type.hpp"
@@ -27,16 +28,6 @@
 
 namespace iox2 {
 
-template <typename T>
-struct PayloadValueType {
-    using TYPE = T;
-};
-
-template <typename T>
-struct PayloadValueType<iox::Slice<T>> {
-    using TYPE = typename iox::Slice<T>::ValueType;
-};
-
 /// Builder to create new [`MessagingPattern::PublishSubscribe`] based [`Service`]s
 template <typename Payload, typename UserHeader, ServiceType S>
 class ServiceBuilderPublishSubscribe {
@@ -149,7 +140,7 @@ inline void ServiceBuilderPublishSubscribe<Payload, UserHeader, S>::set_paramete
         [&](auto value) { iox2_service_builder_pub_sub_set_payload_alignment(&m_handle, value); });
     m_max_nodes.and_then([&](auto value) { iox2_service_builder_pub_sub_set_max_nodes(&m_handle, value); });
 
-    using ValueType = typename PayloadValueType<Payload>::TYPE;
+    using ValueType = typename PayloadInfo<Payload>::TYPE;
     auto type_variant = iox::IsSlice<Payload>::VALUE ? iox2_type_variant_e_DYNAMIC : iox2_type_variant_e_FIXED_SIZE;
 
     // payload type details