UserdataMetatable enable custom gc function.

[aster2013]

Sometimes user want to custom __gc function for some userdata, for example: I have a RefCounted object, when GC, it may call following function.

void RefCountedGC(RefCounted* obj)
{
    obj->ref --;
    if (obj->ref == 0)
        delete obj;
}

So it is better add a argument to UserdataMetatable enable user custom the gc funciton.

UserdataMetatable(bool registerGC= true)
{
    if (registerGC)
    {
        addStaticFunction("__gc", &class_userdata::destructor<ObjectWrapperBase>);
    }

[satoren]

Why don't you use shared_ptr?

state["data"] = std::shared_ptr<RefCounted>(refcounted_ptr,RefCountedGC) ;

[aster2013]

it is an existed game engine, it use tolua to binding cpp code to lua, as you know tolua is slow and has memory leak with ref object.

[satoren]

How unique_ptr? example: e0e4009aff982cbf223ef50cf37d62efd34f80fe

[satoren]

What are you doing to care? Performance cost of unique_ptr is less than shared_ptr, and neary equal raw pointer. Them member function invoke cost is nearly equal.

member function invoke performance benchmark results:

data type	seconds	benchmark function name
allocated by lua_newuserdata data with plain API	1.675	original_api_no_type_check::simple_get_set
allocated by lua_newuserdata data	1.554	kaguya_api_benchmark__::simple_get_set
raw pointer	1.729	kaguya_api_benchmark__::simple_get_set_raw_ptr
shared_ptr	1.784	kaguya_api_benchmark__::simple_get_set_shared_ptr
unique_ptr	1.773	kaguya_api_benchmark__::simple_get_set_unique_ptr

[aster2013]

I am working on the Urho3D game engine, Urho3D/new-luascript-test branch, If you have spare time, please take a look on it.

[satoren]

Wow, interesting work.

[satoren]

Please import e9214b955f1d021c1bc5c5c1fec484f3ecd51eef this fix and specialized for Urho3D::SharedPtr. e.g.

    // Urho3D::SharedPtr<T>
    template<typename T> struct lua_type_traits<Urho3D::SharedPtr<T> > {
        typedef Urho3D::SharedPtr<T>& push_type;
        typedef Urho3D::SharedPtr<T>& get_type;
        typedef Urho3D::SharedPtr<T> type;

        //If need Urho3D::SharedPtr type get.
        static bool strictCheckType(lua_State* l, int index)
        {
            return object_wrapper<type>(l, index, false) != 0;
        }

        //If need Urho3D::SharedPtr type get.
        static bool checkType(lua_State* l, int index)
        {
            return object_wrapper<type>(l, index) != 0 ||
                lua_isnil(l, index);
        }

        //If need Urho3D::SharedPtr type get.
        static get_type get(lua_State* l, int index)
        {
            type* pointer = get_pointer(l, index, types::typetag<type>());
            if (!pointer)
            {
                throw LuaTypeMismatch("type mismatch!!");
            }
            return *pointer;
        }

        static int push(lua_State* l, push_type v)
        {
            if (v)
            {
                typedef ObjectSmartPointerWrapper<type,T> wrapper_type;
                void *storage = lua_newuserdata(l, sizeof(wrapper_type));
                new(storage) wrapper_type(v);
                class_userdata::setmetatable<T>(l);
            }
            else
            {
                lua_pushnil(l);
            }
            return 1;
        }
    };

[aster2013]

What I want is like this:

template<typename T>
SharedPtr<T> KCreateObject()
{
    SharedPtr<T> tPtr(new T(globalContext));
    return tPtr;
}

template<typename T>
void KReleaseObject(T* t)
{
    if (t)
        t->ReleaseRef();
}

template<typename T> struct lua_type_traits<Urho3D::SharedPtr<T>>
{
    typedef const Urho3D::SharedPtr<T>& push_type;

    static int push(lua_State* l, push_type p)
    {
        T* o = p;
        o->AddRef();

            // Push the raw pointer to Lua
        return util::push_args(l, o);
    }
};

So current I disable the default gc function in UserdataMetatable constructor, and add custom gc function.

lua["KImage"].setClass(UserdataMetatable<Image, Resource>(false)  // don't use defaut gc function
    .addStaticFunction("new", &KCreateObject<Image>) // Custom new function
    .addStaticFunction("__gc", &KReleaseObject<Image>) // Custom gc function

    // ...

[satoren]

Why want? kaguya is wrapped for all user data by ObjectWrapper. That is raw-pointer too. Default gcfunction is call ObjectWrapperBase’s destructor.Your code has not been called.

[aster2013]

Thanks, you are right. I have write a shared ptr object wrapper. Please check it

[satoren]

OK!