xo-callback xo-alloc: + GC copy callbacks + unique_ptr cbset support

xo-callback/include/xo/callback/UpCallbackSet.hpp

@@ -0,0 +1,34 @@
+/* @file UpCallbackSet.hpp
+ *
+ * author: Roland Conybeare, Aug 2025
+ */
+
+#include "CallbackSetImpl.hpp"
+#include "callback_concept.hpp"
+#include <memory>
+
+namespace xo {
+    namespace fn {
+        template <typename NativeFn>
+        using UpCallbackSet = CallbackSetImpl<std::unique_ptr<NativeFn>>;
+
+        template <typename NativeFn, typename MemberFn>
+        requires(callback_concept<NativeFn>)
+        class UpNotifyCallbackSet : public UpCallbackSet<NativeFn> {
+        public:
+            explicit UpNotifyCallbackSet(MemberFn fn)
+                : privileged_member_fn_{fn} {}
+
+            template <typename... Tn>
+            void operator()(Tn&&... args) {
+                this->invoke(this->privileged_member_fn_, args...);
+            }
+
+        private:
+            /** implements UpNotifyCallbackSet's call operator **/
+            MemberFn privileged_member_fn_;
+        };
+    } /*namespace fn*/
+} /*namespace xo*/
+
+/* end UpCallbackSet.hpp */