signature.hpp

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#pragma once
 
namespace flecs {
namespace _ {
 
    template <typename T, if_t< is_const_p<T>::value > = 0>
    constexpr flecs::inout_kind_t type_to_inout() {
        return flecs::In;
    }
 
    template <typename T, if_t< is_reference<T>::value > = 0>
    constexpr flecs::inout_kind_t type_to_inout() {
        return flecs::InOut;
    }
 
    template <typename T, if_not_t< 
        is_const_p<T>::value || is_reference<T>::value > = 0>
    constexpr flecs::inout_kind_t type_to_inout() {
        return flecs::InOutDefault;
    }
 
    template <typename T, if_t< is_pointer<T>::value > = 0>
    constexpr flecs::oper_kind_t type_to_oper() {
        return flecs::Optional;
    }
 
    template <typename T, if_not_t< is_pointer<T>::value > = 0>
    constexpr flecs::oper_kind_t type_to_oper() {
        return flecs::And;
    }
 
    template <typename ... Components>
    struct sig {
        sig(flecs::world_t *world) 
            : world_(world)
            , ids({ (_::type<remove_pointer_t<Components>>::id(world))... })
            , inout ({ (type_to_inout<Components>())... })
            , oper ({ (type_to_oper<Components>())... }) 
        { }
 
        flecs::world_t *world_;
        flecs::array<flecs::id_t, sizeof...(Components)> ids;
        flecs::array<flecs::inout_kind_t, sizeof...(Components)> inout;
        flecs::array<flecs::oper_kind_t, sizeof...(Components)> oper;
 
        template <typename Builder>
        void populate(const Builder& b) {
            size_t i = 0;
            for (auto id : ids) {
               if (!(id & ECS_ID_FLAGS_MASK)) {
                    const flecs::type_info_t *ti = ecs_get_type_info(world_, id);
                    if (ti) {
                        // Union relationships always return a value of type
                        // flecs::entity_t which holds the target id of the 
                        // union relationship.
                        // If a union component with a non-zero size (like an 
                        // enum) is added to the query signature, the each/iter
                        // functions would accept a parameter of the component
                        // type instead of flecs::entity_t, which would cause
                        // an assert.
                        ecs_assert(
                            !ti->size || !ecs_has_id(world_, id, flecs::Union),
                            ECS_INVALID_PARAMETER,
                            "use with() method to add union relationship");
                    }
                }
 
                b->with(id).inout(inout[i]).oper(oper[i]);
                i ++;
            }
        }
    };
 
} // namespace _
} // namespace flecs