path: root/src/inc/clr_std/type_traits

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

//
// clr_std/utility
//
// Copy of some key Standard Template Library functionality.
// See http://msdn.microsoft.com/en-us/library/bb982077.aspx for documentation.
//

#ifdef _MSC_VER
#pragma once
#endif

#ifndef __clr_std_type_traits_h__
#define __clr_std_type_traits_h__

#ifdef USE_STL

#include <type_traits>

#else

namespace std
{
    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS remove_const
    template<class _Ty>
    struct remove_const
    {   // remove top level const qualifier
        typedef _Ty type;
    };

    template<class _Ty>
    struct remove_const<const _Ty>
    {   // remove top level const qualifier
        typedef _Ty type;
    };

    template<class _Ty>
    struct remove_const<const _Ty[]>
    {   // remove top level const qualifier
        typedef _Ty type[];
    };

    template<class _Ty, unsigned int _Nx>
    struct remove_const<const _Ty[_Nx]>
    {   // remove top level const qualifier
        typedef _Ty type[_Nx];
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS remove_volatile
    template<class _Ty>
    struct remove_volatile
    {   // remove top level volatile qualifier
        typedef _Ty type;
    };

    template<class _Ty>
    struct remove_volatile<volatile _Ty>
    {   // remove top level volatile qualifier
        typedef _Ty type;
    };

    template<class _Ty>
    struct remove_volatile<volatile _Ty[]>
    {   // remove top level volatile qualifier
        typedef _Ty type[];
    };

    template<class _Ty, unsigned int _Nx>
    struct remove_volatile<volatile _Ty[_Nx]>
    {   // remove top level volatile qualifier
        typedef _Ty type[_Nx];
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS remove_cv
    template<class _Ty>
    struct remove_cv
    {   // remove top level const and volatile qualifiers
        typedef typename remove_const<typename remove_volatile<_Ty>::type>::type type;
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE remove_reference
    template<class T>
    struct remove_reference
    {   // remove reference
        typedef T type;
    };

    template<class T>
    struct remove_reference<T&>
    {   // remove reference
        typedef T type;
    };

    template<class T>
    struct remove_reference<T&&>
    {   // remove rvalue reference
        typedef T type;
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE remove_pointer
    template<class T>
    struct remove_pointer
    {   // remove pointer
        typedef T type;
    };

    template<class T>
    struct remove_pointer<T*>
    {   // remove pointer
        typedef T type;
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE FUNCTION identity
    template<class T>
    struct identity
    {   // map T to type unchanged
        typedef T type;

        inline
        const T& operator()(const T& left) const
        {   // apply identity operator to operand
            return (left);
        }
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS integral_constant
    template<class _Ty, _Ty _Val>
    struct integral_constant
    {   // convenient template for integral constant types
        static const _Ty value = _Val;

        typedef _Ty value_type;
        typedef integral_constant<_Ty, _Val> type;
    };

    typedef integral_constant<bool, true> true_type;
    typedef integral_constant<bool, false> false_type;

    // TEMPLATE CLASS _Cat_base
    template<bool>
    struct _Cat_base
        : false_type
    {    // base class for type predicates
    };

    template<>
    struct _Cat_base<true>
        : true_type
    {    // base class for type predicates
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS enable_if
    template<bool _Test, class _Type = void>
    struct enable_if
    {   // type is undefined for assumed !_Test
    };

    template<class _Type>
    struct enable_if<true, _Type>
    {   // type is _Type for _Test
        typedef _Type type;
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS conditional
    template<bool _Test, class _Ty1, class _Ty2>
    struct conditional
    {   // type is _Ty2 for assumed !_Test
        typedef _Ty2 type;
    };

    template<class _Ty1, class _Ty2>
    struct conditional<true, _Ty1, _Ty2>
    {   // type is _Ty1 for _Test
        typedef _Ty1 type;
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS is_lvalue_reference
    template<class _Ty>
    struct is_lvalue_reference
        : false_type
    {   // determine whether _Ty is an lvalue reference
    };

    template<class _Ty>
    struct is_lvalue_reference<_Ty&>
        : true_type
    {   // determine whether _Ty is an lvalue reference
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS is_rvalue_reference
    template<class _Ty>
    struct is_rvalue_reference
        : false_type
    {   // determine whether _Ty is an rvalue reference
    };

    template<class _Ty>
    struct is_rvalue_reference<_Ty&&>
        : true_type
    {   // determine whether _Ty is an rvalue reference
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS is_reference
    template<class _Ty>
    struct is_reference
        : conditional<
            is_lvalue_reference<_Ty>::value || is_rvalue_reference<_Ty>::value,
            true_type,
            false_type>::type
    {   // determine whether _Ty is a reference
    };

    // TEMPLATE CLASS is_pointer
    template<class _Ty>
    struct is_pointer
        : false_type
    {   // determine whether _Ty is a pointer
    };

    template<class _Ty>
    struct is_pointer<_Ty *>
        : true_type
    {   // determine whether _Ty is a pointer
    };

    // TEMPLATE CLASS _Is_integral
    template<class _Ty>
    struct _Is_integral
        : false_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<bool>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<char>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<unsigned char>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<signed char>
        : true_type
    {    // determine whether _Ty is integral
    };

 #ifdef _NATIVE_WCHAR_T_DEFINED
    template<>
    struct _Is_integral<wchar_t>
        : true_type
    {    // determine whether _Ty is integral
    };
 #endif /* _NATIVE_WCHAR_T_DEFINED */

    template<>
    struct _Is_integral<unsigned short>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<signed short>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<unsigned int>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<signed int>
        : true_type
    {    // determine whether _Ty is integral
    };

// On Unix 'long' is a 64-bit type (same as __int64) and the following two definitions
// conflict with _Is_integral<unsigned __int64> and _Is_integral<signed __int64>.
#ifndef PLATFORM_UNIX
    template<>
    struct _Is_integral<unsigned long>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<signed long>
        : true_type
    {    // determine whether _Ty is integral
    };
#endif /* PLATFORM_UNIX */

 #if _HAS_CHAR16_T_LANGUAGE_SUPPORT
    template<>
    struct _Is_integral<char16_t>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<char32_t>
        : true_type
    {    // determine whether _Ty is integral
    };
 #endif /* _HAS_CHAR16_T_LANGUAGE_SUPPORT */

    template<>
    struct _Is_integral<unsigned __int64>
        : true_type
    {    // determine whether _Ty is integral
    };

    template<>
    struct _Is_integral<signed __int64>
        : true_type
    {    // determine whether _Ty is integral
    };

    // TEMPLATE CLASS is_integral
    template<class _Ty>
    struct is_integral
        : _Is_integral<typename remove_cv<_Ty>::type>
    {    // determine whether _Ty is integral
    };

    // TEMPLATE CLASS _Is_floating_point
    template<class _Ty>
    struct _Is_floating_point
        : false_type
    {    // determine whether _Ty is floating point
    };

    template<>
    struct _Is_floating_point<float>
        : true_type
    {    // determine whether _Ty is floating point
    };

    template<>
    struct _Is_floating_point<double>
        : true_type
    {    // determine whether _Ty is floating point
    };

// In PAL, we define long as int and so this becomes int double,
// which is a nonsense
#ifndef FEATURE_PAL  
    template<>
    struct _Is_floating_point<long double>
        : true_type
    {    // determine whether _Ty is floating point
    };
#endif

    // TEMPLATE CLASS is_floating_point
    template<class _Ty>
    struct is_floating_point
        : _Is_floating_point<typename remove_cv<_Ty>::type>
    {    // determine whether _Ty is floating point
    };

    // TEMPLATE CLASS is_arithmetic
    template<class _Ty>
    struct is_arithmetic
    : _Cat_base<is_integral<_Ty>::value
        || is_floating_point<_Ty>::value>
    {    // determine whether _Ty is an arithmetic type
    };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS is_signed
    template <typename T>
    struct is_signed : conditional<
        static_cast<typename remove_const<T>::type>(-1) < 0, true_type, false_type>::type {};

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS is_same
    template<class T1, class T2>
    struct is_same : false_type { };

    //-----------------------------------------------------------------------------------------
    template<class T1>
    struct is_same<T1, T1> : true_type { };

    //-----------------------------------------------------------------------------------------
    // TEMPLATE CLASS is_base_of
#ifdef _MSC_VER

    template <typename TBase, typename TDerived>
    struct is_base_of :
        conditional<__is_base_of( TBase, TDerived), true_type, false_type>::type {};

#else
    namespace detail
    {
        //-------------------------------------------------------------------------------------
        // Helper types Small and Big - guarantee that sizeof(Small) < sizeof(Big)
        //

        template <class T, class U>
        struct conversion_helper
        {
            typedef char Small;
            struct Big { char dummy[2]; };
            static Big   Test(...);
            static Small Test(U);
            static T MakeT();
        };

        //-------------------------------------------------------------------------------------
        // class template conversion
        // Figures out the conversion relationships between two types
        // Invocations (T and U are types):
        // a) conversion<T, U>::exists
        // returns (at compile time) true if there is an implicit conversion from T
        // to U (example: Derived to Base)
        // b) conversion<T, U>::exists2Way
        // returns (at compile time) true if there are both conversions from T
        // to U and from U to T (example: int to char and back)
        // c) conversion<T, U>::sameType
        // returns (at compile time) true if T and U represent the same type
        //
        // NOTE: might not work if T and U are in a private inheritance hierarchy.
        //

        template <class T, class U>
        struct conversion
        {
            typedef detail::conversion_helper<T, U> H;
            static const bool exists = sizeof(typename H::Small) == sizeof((H::Test(H::MakeT())));
            static const bool exists2Way = exists && conversion<U, T>::exists;
            static const bool sameType = false;
        };

        template <class T>
        struct conversion<T, T>    
        {
            static const bool exists = true;
            static const bool exists2Way = true;
            static const bool sameType = true;
        };

        template <class T>
        struct conversion<void, T>    
        {
            static const bool exists = false;
            static const bool exists2Way = false;
            static const bool sameType = false;
        };

        template <class T>
        struct conversion<T, void>    
        {
            static const bool exists = false;
            static const bool exists2Way = false;
            static const bool sameType = false;
        };

        template <>
        struct conversion<void, void>    
        {
            static const bool exists = true;
            static const bool exists2Way = true;
            static const bool sameType = true;
        };
    } // detail

    // Note that we need to compare pointer types here, since conversion of types by-value
    // just tells us whether or not an implicit conversion constructor exists. We handle
    // type parameters that are already pointers specially; see below.
    template <typename TBase, typename TDerived>
    struct is_base_of :
        conditional<detail::conversion<TDerived *, TBase *>::exists, true_type, false_type>::type {};

    // Specialization to handle type parameters that are already pointers.
    template <typename TBase, typename TDerived>
    struct is_base_of<TBase *, TDerived *> :
        conditional<detail::conversion<TDerived *, TBase *>::exists, true_type, false_type>::type {};

    // Specialization to handle invalid mixing of pointer types.
    template <typename TBase, typename TDerived>
    struct is_base_of<TBase *, TDerived> :
        false_type {};

    // Specialization to handle invalid mixing of pointer types.
    template <typename TBase, typename TDerived>
    struct is_base_of<TBase, TDerived *> :
        false_type {};

#endif

    // Use to determine if a template type parameter is a string.
    template <typename T>
    struct is_cstr
        : public std::false_type
    {};

    template <typename T>
    struct is_cstr< T* >
        : public std::conditional<
            std::is_same<typename std::remove_cv<T>::type, char>::value ||
                std::is_same<typename std::remove_cv<T>::type, wchar_t>::value,
            std::true_type,
            std::false_type>::type
        
    { };

} // namespace std

#endif // !USE_STL

#define REM_CONST(T)    typename std::remove_const< T >::type
#define REM_CV(T)       typename std::remove_cv< T >::type
#define REM_REF(T)      typename std::remove_reference< T >::type

#define REF_T(T)        REM_REF(T) &
#define REF_CT(T)       REM_REF(REM_CONST(T)) const &

#endif // __clr_std_type_traits_h__

// Help the VIM editor figure out what kind of file this no-extension file is.
// vim: filetype=cpp