Introduce SharedObject

refs #7361

lib/base/CMakeLists.txt

@@ -61,6 +61,7 @@ set(base_SOURCES
   scriptutils.cpp scriptutils.hpp
   serializer.cpp serializer.hpp
   shared.hpp
+  shared-object.hpp
   singleton.hpp
   socket.cpp socket.hpp
   stacktrace.cpp stacktrace.hpp

lib/base/shared-object.hpp

@@ -0,0 +1,73 @@
+/* Icinga 2 | (c) 2019 Icinga GmbH | GPLv2+ */
+
+#ifndef SHARED_OBJECT_H
+#define SHARED_OBJECT_H
+
+#include "base/atomic.hpp"
+#include "base/object.hpp"
+#include <cstdint>
+
+namespace icinga
+{
+
+class SharedObject;
+
+inline void intrusive_ptr_add_ref(SharedObject *object);
+inline void intrusive_ptr_release(SharedObject *object);
+
+/**
+ * Seemless and polymorphistic base for any class to create shared pointers of.
+ * Saves a memory allocation compared to std::shared_ptr.
+ *
+ * @ingroup base
+ */
+class SharedObject
+{
+	friend void intrusive_ptr_add_ref(SharedObject *object);
+	friend void intrusive_ptr_release(SharedObject *object);
+
+protected:
+	inline SharedObject() : m_References(0)
+	{
+	}
+
+	inline SharedObject(const SharedObject&) : SharedObject()
+	{
+	}
+
+	inline SharedObject(SharedObject&&) : SharedObject()
+	{
+	}
+
+	inline SharedObject& operator=(const SharedObject&)
+	{
+		return *this;
+	}
+
+	inline SharedObject& operator=(SharedObject&&)
+	{
+		return *this;
+	}
+
+	inline virtual
+	~SharedObject() = default;
+
+private:
+	Atomic<uint_fast64_t> m_References;
+};
+
+inline void intrusive_ptr_add_ref(SharedObject *object)
+{
+	object->m_References.fetch_add(1);
+}
+
+inline void intrusive_ptr_release(SharedObject *object)
+{
+	if (object->m_References.fetch_sub(1) == 1u) {
+		delete object;
+	}
+}
+
+}
+
+#endif /* SHARED_OBJECT_H */