Commonwealth-Online-Public/plugin/lib/commonlibf4/include/RE/RTTI.h

#pragma once

namespace RE
{
	namespace msvc
	{
		class type_info;
	}

	namespace RTTI
	{
		template <class T>
		class RVA
		{
		public:
			using value_type = T;
			using pointer = value_type*;
			using reference = value_type&;

			constexpr RVA() noexcept = default;

			constexpr RVA(std::uint32_t a_rva) noexcept :
				_rva(a_rva)
			{}

			[[nodiscard]] pointer            get() const { return is_good() ? REL::Relocation<T*>{ REL::Offset(_rva) }.get() : nullptr; }
			[[nodiscard]] std::uint32_t      offset() const noexcept { return _rva; }
			[[nodiscard]] reference          operator*() const { return *get(); }
			[[nodiscard]] pointer            operator->() const { return get(); }
			[[nodiscard]] explicit constexpr operator bool() const noexcept { return is_good(); }

		protected:
			[[nodiscard]] constexpr bool is_good() const noexcept { return _rva != 0; }

			// members
			std::uint32_t _rva{ 0 };  // 00
		};
		static_assert(sizeof(RVA<void*>) == 0x4);

		using TypeDescriptor = std::type_info;

		class PMD
		{
		public:
			// members
			std::int32_t mDisp;  // 0
			std::int32_t pDisp;  // 4
			std::int32_t vDisp;  // 8
		};
		static_assert(sizeof(PMD) == 0xC);

		class BaseClassDescriptor
		{
		public:
			enum class Attribute : std::uint32_t
			{
				kNone = 0,
				kNotVisible = 1 << 0,
				kAmbiguous = 1 << 1,
				kPrivate = 1 << 2,
				kPrivateOrProtectedBase = 1 << 3,
				kVirtual = 1 << 4,
				kNonPolymorphic = 1 << 5,
				kHasHierarchyDescriptor = 1 << 6
			};

			// members
			RVA<TypeDescriptor>                     typeDescriptor;     // 00
			std::uint32_t                           numContainedBases;  // 04
			PMD                                     pmd;                // 08
			REX::TEnumSet<Attribute, std::uint32_t> attributes;         // 14
		};
		static_assert(sizeof(BaseClassDescriptor) == 0x18);

		class ClassHierarchyDescriptor
		{
		public:
			enum class Attribute
			{
				kNoInheritance = 0,
				kMultipleInheritance = 1 << 0,
				kVirtualInheritance = 1 << 1,
				kAmbiguousInheritance = 1 << 2
			};

			// members
			std::uint32_t                           signature;       // 00
			REX::TEnumSet<Attribute, std::uint32_t> attributes;      // 04
			std::uint32_t                           numBaseClasses;  // 08
			RVA<BaseClassDescriptor>                baseClassArray;  // 0C
		};
		static_assert(sizeof(ClassHierarchyDescriptor) == 0x10);

		class CompleteObjectLocator
		{
		public:
			enum class Signature
			{
				x86 = 0,
				x64 = 1
			};

			// members
			REX::TEnumSet<Signature, std::uint32_t> signature;        // 00
			std::uint32_t                           offset;           // 04
			std::uint32_t                           ctorDispOffset;   // 08
			RVA<TypeDescriptor>                     typeDescriptor;   // 0C
			RVA<ClassHierarchyDescriptor>           classDescriptor;  // 10
		};
		static_assert(sizeof(CompleteObjectLocator) == 0x14);
	}

	inline void* RTDynamicCast(void* a_inptr, std::int32_t a_vfDelta, void* a_srcType, void* a_targetType, std::int32_t a_isReference)
	{
		using func_t = decltype(&RTDynamicCast);
		static REL::Relocation<func_t> func{ ID::RTDynamicCast };
		return func(a_inptr, a_vfDelta, a_srcType, a_targetType, a_isReference);
	}

	namespace detail
	{
		template <class T>
		using remove_cvpr_t =
			std::remove_cv_t<
				std::remove_pointer_t<
					std::remove_reference_t<T>>>;

		template <class T>
		struct target_is_valid :
			std::disjunction<
				std::is_polymorphic<
					remove_cvpr_t<T>>,
				std::is_same<
					void*,
					std::remove_cv_t<T>>>
		{};

		template <class, class>
		struct types_are_compat :
			std::false_type
		{};

		template <class To, class From>
		struct types_are_compat<To, From*> :
			std::is_pointer<To>
		{};

		template <class To, class From>
		struct types_are_compat<To, const From*> :
			std::conjunction<
				std::is_pointer<To>,
				std::is_const<
					std::remove_pointer_t<To>>>
		{};

		template <class To, class From>
		struct types_are_compat<To, volatile From*> :
			std::conjunction<
				std::is_pointer<To>,
				std::is_volatile<
					std::remove_pointer_t<To>>>
		{};

		template <class To, class From>
		struct types_are_compat<To, const volatile From*> :
			std::conjunction<
				std::is_pointer<To>,
				std::is_const<
					std::remove_pointer_t<To>>,
				std::is_volatile<
					std::remove_pointer_t<To>>>
		{};

		template <class, class = void>
		struct implements_rtti :
			std::false_type
		{};

		template <class T>
		struct implements_rtti<
			T,
			std::void_t<
				decltype(remove_cvpr_t<T>::RTTI)>> :
			std::true_type
		{};

		template <class To, class From>
		struct cast_is_valid :
			std::conjunction<
				types_are_compat<
					To,
					From>,
				target_is_valid<
					To>,
				implements_rtti<To>,
				implements_rtti<From>>
		{};

		template <class To, class From>
		inline constexpr bool cast_is_valid_v = cast_is_valid<To, From>::value;
	}

	template <class To, class From>
	To fallout_cast(From* a_from)  //
		requires(detail::cast_is_valid_v<To, From*>)
	{
		REL::Relocation<void*> from{ detail::remove_cvpr_t<From>::RTTI };
		REL::Relocation<void*> to{ detail::remove_cvpr_t<To>::RTTI };
		return static_cast<To>(
			RE::RTDynamicCast(
				const_cast<void*>(
					static_cast<const volatile void*>(a_from)),
				0,
				from.get(),
				to.get(),
				false));
	}
}