Sophiar2/src/core/small_obj.hpp

#ifndef SOPHIAR2_SMALL_OBJ_H
#define SOPHIAR2_SMALL_OBJ_H

#include <boost/core/noncopyable.hpp>
#include <boost/pool/object_pool.hpp>
#include <boost/smart_ptr/intrusive_ptr.hpp>

#include <memory>
#include <type_traits>

namespace sophiar {

    template<typename DeriveT>
    struct small_obj_ref_counter : private boost::noncopyable {
        uint32_t ref_count = 0;
    };

    template<typename DeriveT>
    void intrusive_ptr_add_ref(small_obj_ref_counter<DeriveT> *pointer) {
        ++pointer->ref_count;
    }

    template<typename DeriveT>
    void intrusive_ptr_release(small_obj_ref_counter<DeriveT> *pointer) {
        if (--pointer->ref_count == 0) {
            DeriveT::allocator.destroy(static_cast<DeriveT *>(pointer));
        }
    }

    template<typename DeriveT>
    struct small_obj : public small_obj_ref_counter<DeriveT> {

        using pointer = boost::intrusive_ptr<DeriveT>;
        using allocator_type = boost::object_pool<DeriveT>;

//      static allocator_type allocator;
        inline static allocator_type allocator;

        template<typename... Args>
        std::enable_if_t<std::is_constructible_v<DeriveT, Args...>, pointer>
        static new_instance(Args &&... args) {
            auto ret_pointer = allocator.malloc();
            std::construct_at(ret_pointer, std::forward<Args>(args)...);
            return ret_pointer;
        }

    };

//    template<typename DeriveT>
//    typename small_obj<DeriveT>::allocator_type small_obj<DeriveT>::allocator{};

#define FORWARD_CONSTRUCT(DerivedT, BaseT) \
template<typename... Args> \
    explicit DerivedT(Args &&...args) \
    :BaseT(std::forward<Args>(args)...) { \
    static_assert(std::is_constructible_v<BaseT, Args...>); \
}

}

#endif //SOPHIAR2_SMALL_OBJ_H