feat: add NiRTTI

Author: shad0wshayd3

include/RE/N/NiRTTI.h

@@ -0,0 +1,129 @@
+#pragma once
+
+namespace RE
+{
+	struct NiRTTI
+	{
+	public:
+		[[nodiscard]] constexpr const char*   GetName() const noexcept { return name; }
+		[[nodiscard]] constexpr const NiRTTI* GetBaseRTTI() const noexcept { return baseRTTI; }
+
+		[[nodiscard]] constexpr bool IsKindOf(const NiRTTI* a_rtti) const noexcept
+		{
+			for (auto iter = this; iter; iter = iter->GetBaseRTTI()) {
+				if (iter == a_rtti) {
+					return true;
+				}
+			}
+			return false;
+		}
+
+		// members
+		const char* name;      // 00
+		NiRTTI*     baseRTTI;  // 08
+	};
+	static_assert(sizeof(NiRTTI) == 0x10);
+
+	namespace Ni_Impl
+	{
+		template <class T>
+		using remove_cvpr_t =
+			std::remove_pointer_t<
+				std::remove_reference_t<
+					std::remove_cv_t<T>>>;
+
+		template <class To, class From>
+		struct types_are_compat :
+			std::false_type
+		{};
+
+		template <class To, class From>
+		struct types_are_compat<To&, From> :
+			std::is_lvalue_reference<
+				std::remove_cv_t<From>>
+		{};
+
+		template <class To, class From>
+		struct types_are_compat<To*, From> :
+			std::is_pointer<
+				std::remove_cv_t<From>>
+		{};
+
+		template <class Base, class Derived>
+		struct is_base_of_no_cvpr :
+			std::is_base_of<
+				remove_cvpr_t<Base>,
+				remove_cvpr_t<Derived>>
+		{};
+
+		template <class T, class Enable = void>
+		struct _has_rtti :
+			std::false_type
+		{};
+
+		template <class T>
+		struct _has_rtti<T, std::void_t<decltype(T::Ni_RTTI)>> :
+			std::true_type
+		{};
+
+		template <class T>
+		struct has_rtti :
+			_has_rtti<remove_cvpr_t<T>>
+		{};
+
+		template <class To, class From>
+		struct cast_is_valid :
+			std::conjunction<
+				types_are_compat<To, From>,
+				is_base_of_no_cvpr<From, To>,
+				has_rtti<To>,
+				has_rtti<From>>
+		{};
+
+		template <class To, class From>
+		inline constexpr bool cast_is_valid_v = cast_is_valid<To, From>::value;
+	}
+}
+
+// downcast
+template <
+	class To,
+	class From,
+	std::enable_if_t<
+		RE::Ni_Impl::cast_is_valid_v<
+			To,
+			const From*>,
+		int> = 0>
+To netimmerse_cast(const From* a_from)
+{
+	if (!a_from) {
+		return nullptr;
+	}
+
+	static REL::Relocation<const RE::NiRTTI*> to{ RE::Ni_Impl::remove_cvpr_t<To>::Ni_RTTI };
+
+	const RE::NiRTTI* toRTTI = to.get();
+	const RE::NiRTTI* fromRTTI = a_from->GetRTTI();
+	while (fromRTTI) {
+		if (fromRTTI == toRTTI) {
+			return static_cast<To>(const_cast<From*>(a_from));
+		}
+		fromRTTI = fromRTTI->GetBaseRTTI();
+	}
+
+	return nullptr;
+}
+
+// upcast
+template <
+	class To,
+	class From,
+	std::enable_if_t<
+		RE::Ni_Impl::cast_is_valid_v<
+			const From*,
+			To>,
+		int> = 0>
+To netimmerse_cast(const From* a_from)
+{
+	return static_cast<To>(const_cast<From*>(a_from));
+}