Add simple alternative to std::function without smart pointers or move semantics

examples/knx-linux/CMakeLists.txt

@@ -107,6 +107,7 @@ add_executable(knx-linux
         ../../src/knx/secure_application_layer.h
         ../../src/knx/security_interface_object.cpp
         ../../src/knx/security_interface_object.h
+        ../../src/knx/simple_functional.h
         ../../src/knx/simple_map.h
         ../../src/knx/table_object.cpp
         ../../src/knx/save_restore.h

src/knx/simple_functional.h

@@ -0,0 +1,82 @@
+#pragma once
+#include <memory>
+
+//
+// Basis is https://shaharmike.com/cpp/naive-std-function/
+//
+// Do not forget to call cleanup() once you do not need the function object (functor) anymore to free the memory.
+// No move semantics and/or smart pointers are used
+
+template <typename T>
+class function;
+
+template <typename ReturnValue, typename... Args>
+class function<ReturnValue(Args...)>
+{
+  public:
+    function()
+    {
+        //printf("function()\n");
+        callable_ = nullptr;
+    }
+
+    ~function()
+    {
+        //printf("~function()\n");
+    }
+
+    template<typename T>
+    function(T t)
+    {
+        //printf("function(T)\n");
+        callable_ = new CallableT<T>(t);
+    }
+
+    template <typename T>
+    function& operator=(T t)
+    {
+        //printf("operator=(T)\n");
+        callable_ = new CallableT<T>(t);
+        return *this;
+    }
+
+    ReturnValue operator()(Args... args) const
+    {
+        //assert(callable_);
+        return callable_->Invoke(args...);
+    }
+
+    void cleanup()
+    {
+        delete callable_;
+    }
+
+  private:
+    class ICallable
+    {
+    public:
+        virtual ~ICallable() = default;
+        virtual ReturnValue Invoke(Args...) = 0;
+    };
+
+    template <typename T>
+    class CallableT : public ICallable
+    {
+      public:
+        CallableT(const T& t)
+            : t_(t) {
+        }
+
+        ~CallableT() override = default;
+
+        ReturnValue Invoke(Args... args) override
+        {
+            return t_(args...);
+        }
+
+      private:
+        T t_;
+    };
+
+    ICallable* callable_;
+};