RTTI.h

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#pragma once
 
struct __type_info_node;
 
namespace RE
{
    namespace msvc
    {
        class __declspec(novtable) type_info
        {
        public:
            virtual ~type_info();  // 00
 
            [[nodiscard]] const char* mangled_name() const noexcept { return _name; }
 
        private:
            // members
            void* _data;     // 08
            char  _name[1];  // 10
        };
        static_assert(sizeof(type_info) == 0x18);
    }
 
    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 = msvc::type_info;
 
        struct PMD
        {
        public:
            // members
            std::int32_t mDisp;  // 0
            std::int32_t pDisp;  // 4
            std::int32_t vDisp;  // 8
        };
        static_assert(sizeof(PMD) == 0xC);
 
        struct 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
            stl::enumeration<Attribute, std::uint32_t> attributes;         // 14
        };
        static_assert(sizeof(BaseClassDescriptor) == 0x18);
 
        struct ClassHierarchyDescriptor
        {
        public:
            enum class Attribute
            {
                kNoInheritance = 0,
                kMultipleInheritance = 1 << 0,
                kVirtualInheritance = 1 << 1,
                kAmbiguousInheritance = 1 << 2
            };
 
            // members
            std::uint32_t                              signature;       // 00
            stl::enumeration<Attribute, std::uint32_t> attributes;      // 04
            std::uint32_t                              numBaseClasses;  // 08
            RVA<BaseClassDescriptor>                   baseClassArray;  // 0C
        };
        static_assert(sizeof(ClassHierarchyDescriptor) == 0x10);
 
        struct CompleteObjectLocator
        {
        public:
            enum class Signature
            {
                x86 = 0,
                x64 = 1
            };
 
            // members
            stl::enumeration<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);
        REL::Relocation<func_t> func{ Offset::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,
    std::enable_if_t<
        RE::detail::cast_is_valid_v<
            To,
            From*>,
        int> = 0>
To skyrim_cast(From* a_from)
{
    REL::Relocation<void*> from{ RE::detail::remove_cvpr_t<From>::RTTI };
    REL::Relocation<void*> to{ RE::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));
}