src/Reactor/Traits.hpp

// Copyright 2019 The SwiftShader Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef rr_Traits_hpp
#define rr_Traits_hpp

#include <stdint.h>
#include <type_traits>

#ifdef Bool
#undef Bool // b/127920555
#endif

namespace rr
{
	// Forward declarations
	class Value;

	class Void;
	class Bool;
	class Byte;
	class SByte;
	class Short;
	class UShort;
	class Int;
	class UInt;
	class Long;
	class Half;
	class Float;

	template<class T> class Pointer;
	template<class T> class LValue;
	template<class T> class RValue;

	// enabled_if_t is identical to C++14's std::enable_if_t.
	// std::enable_if_t was introduced in C++14, but Reactor must support
	// C++11.
	template<bool Condition, class TrueType = void>
	using enable_if_t = typename std::enable_if<Condition, TrueType>::type;

	// IsDefined<T>::value is true if T is a valid type, otherwise false.
	template <typename T, typename Enable = void>
	struct IsDefined
	{
		static constexpr bool value = false;
	};

	template <typename T>
	struct IsDefined<T, enable_if_t<(sizeof(T)>0)> >
	{
		static constexpr bool value = true;
	};

	template <>
	struct IsDefined<void>
	{
		static constexpr bool value = true;
	};

	// CToReactorT<T> resolves to the corresponding Reactor type for the given C
	// template type T.
	template<typename T, typename ENABLE = void> struct CToReactor;
	template<typename T> using CToReactorT = typename CToReactor<T>::type;

	// CToReactor specializations for POD types.
	template<> struct CToReactor<void>    	{ using type = Void; };
	template<> struct CToReactor<bool>    	{ using type = Bool;   static Bool   cast(bool);     };
	template<> struct CToReactor<uint8_t> 	{ using type = Byte;   static Byte   cast(uint8_t);  };
	template<> struct CToReactor<int8_t>  	{ using type = SByte;  static SByte  cast(int8_t);   };
	template<> struct CToReactor<int16_t> 	{ using type = Short;  static Short  cast(int16_t);  };
	template<> struct CToReactor<uint16_t>	{ using type = UShort; static UShort cast(uint16_t); };
	template<> struct CToReactor<int32_t> 	{ using type = Int;    static Int    cast(int32_t);  };
	template<> struct CToReactor<uint32_t>	{ using type = UInt;   static UInt   cast(uint32_t); };
	template<> struct CToReactor<float>   	{ using type = Float;  static Float  cast(float);    };

	// TODO: Long has no constructor that takes a uint64_t
	template<> struct CToReactor<uint64_t>	{ using type = Long;  /* static Long   cast(uint64_t); */ };

	// HasReactorType<T>::value resolves to true iff there exists a
	// CToReactorT specialization for type T.
	template<typename T>
	using HasReactorType = IsDefined< CToReactorT<T> >;

	// CToReactorPtr<T>::type resolves to the corresponding Reactor Pointer<>
	// type for T*.
	// For T types that have a CToReactorT<> specialization,
	// CToReactorPtr<T>::type resolves to Pointer< CToReactorT<T> >, otherwise
	// CToReactorPtr<T>::type resolves to Pointer<Byte>.
	template<typename T, typename ENABLE = void> struct CToReactorPtr
	{
		using type = Pointer<Byte>;
		static inline type cast(const T* v); // implemented in Traits.inl
	};

	// CToReactorPtr specialization for T types that have a CToReactorT<>
	// specialization.
	template<typename T> struct CToReactorPtr<T, enable_if_t< HasReactorType<T>::value > >
	{
		using type = Pointer< CToReactorT<T> >;
		static inline type cast(const T* v); // implemented in Traits.inl
	};

	// CToReactorPtr specialization for void*.
	// Maps to Pointer<Byte> instead of Pointer<Void>.
	template<> struct CToReactorPtr<void, void>
	{
		using type = Pointer<Byte>;
		static inline type cast(const void* v); // implemented in Traits.inl
	};

	// CToReactorPtr specialization for function pointer types.
	// Maps to Pointer<Byte>.
	// Drops the 'const' qualifier from the cast() method to avoid warnings
	// about const having no meaning for function types.
	template<typename T> struct CToReactorPtr<T, enable_if_t< std::is_function<T>::value > >
	{
		using type = Pointer<Byte>;
		static inline type cast(T* v); // implemented in Traits.inl
	};

	template<typename T> using CToReactorPtrT = typename CToReactorPtr<T>::type;

	// CToReactor specialization for pointer types.
	// For T types that have a CToReactorT<> specialization,
	// CToReactorT<T*>::type resolves to Pointer< CToReactorT<T> >, otherwise
	// CToReactorT<T*>::type resolves to Pointer<Byte>.
	template<typename T>
	struct CToReactor<T, enable_if_t<std::is_pointer<T>::value> >
	{
		using elem = typename std::remove_pointer<T>::type;
		using type = CToReactorPtrT<elem>;
		static inline type cast(T v); // implemented in Traits.inl
	};

	// CToReactor specialization for enum types.
	template<typename T>
	struct CToReactor<T, enable_if_t<std::is_enum<T>::value> >
	{
		using underlying = typename std::underlying_type<T>::type;
		using type = CToReactorT<underlying>;
		static type cast(T v); // implemented in Traits.inl
	};

	// IsRValue::value is true if T is of type RValue<X>, where X is any type.
	template <typename T, typename Enable = void> struct IsRValue { static constexpr bool value = false; };
	template <typename T> struct IsRValue<T, enable_if_t<IsDefined<typename T::rvalue_underlying_type>::value> > { static constexpr bool value = true; };

	// IsLValue::value is true if T is of, or derives from type LValue<T>.
	template <typename T> struct IsLValue { static constexpr bool value = std::is_base_of<LValue<T>, T>::value; };

	// IsReference::value is true if T is of type Reference<X>, where X is any type.
	template <typename T, typename Enable = void> struct IsReference { static constexpr bool value = false; };
	template <typename T> struct IsReference<T, enable_if_t<IsDefined<typename T::reference_underlying_type>::value> > { static constexpr bool value = true; };

	// ReactorTypeT<T> returns the LValue Reactor type for T.
	// T can be a C-type, RValue or LValue.
	template<typename T, typename ENABLE = void> struct ReactorType;
	template<typename T> using ReactorTypeT = typename ReactorType<T>::type;
	template<typename T> struct ReactorType<T, enable_if_t<IsDefined<CToReactorT<T>>::value> >
	{
		using type = CToReactorT<T>;
		static type cast(T v) { return CToReactor<T>::cast(v); }
	};
	template<typename T> struct ReactorType<T, enable_if_t<IsRValue<T>::value> >
	{
		using type = typename T::rvalue_underlying_type;
		static type cast(T v) { return type(v); }
	};
	template<typename T> struct ReactorType<T, enable_if_t<IsLValue<T>::value> >
	{
		using type = T;
		static type cast(T v) { return type(v); }
	};
	template<typename T> struct ReactorType<T, enable_if_t<IsReference<T>::value> >
	{
		using type = T;
		static type cast(T v) { return type(v); }
	};


	// Reactor types that can be used as a return type for a function.
	template <typename T> struct CanBeUsedAsReturn { static constexpr bool value = false; };
	template <> struct CanBeUsedAsReturn<Void>     { static constexpr bool value = true; };
	template <> struct CanBeUsedAsReturn<Int>      { static constexpr bool value = true; };
	template <> struct CanBeUsedAsReturn<UInt>     { static constexpr bool value = true; };
	template <> struct CanBeUsedAsReturn<Float>    { static constexpr bool value = true; };
	template <typename T> struct CanBeUsedAsReturn<Pointer<T>> { static constexpr bool value = true; };

	// Reactor types that can be used as a parameter types for a function.
	template <typename T> struct CanBeUsedAsParameter { static constexpr bool value = false; };
	template <> struct CanBeUsedAsParameter<Int>      { static constexpr bool value = true; };
	template <> struct CanBeUsedAsParameter<UInt>     { static constexpr bool value = true; };
	template <> struct CanBeUsedAsParameter<Float>    { static constexpr bool value = true; };
	template <typename T> struct CanBeUsedAsParameter<Pointer<T>> { static constexpr bool value = true; };

	// AssertParameterTypeIsValid statically asserts that all template parameter
	// types can be used as a Reactor function parameter.
	template<typename T, typename ... other>
	struct AssertParameterTypeIsValid : AssertParameterTypeIsValid<other...>
	{
		static_assert(CanBeUsedAsParameter<T>::value, "Invalid parameter type");
	};
	template<typename T>
	struct AssertParameterTypeIsValid<T>
	{
		static_assert(CanBeUsedAsParameter<T>::value, "Invalid parameter type");
	};

	// AssertFunctionSignatureIsValid statically asserts that the Reactor
	// function signature is valid.
	template<typename Return, typename... Arguments>
	class AssertFunctionSignatureIsValid;
	template<typename Return>
	class AssertFunctionSignatureIsValid<Return(Void)> {};
	template<typename Return, typename... Arguments>
	class AssertFunctionSignatureIsValid<Return(Arguments...)>
	{
		static_assert(CanBeUsedAsReturn<Return>::value, "Invalid return type");
		static_assert(sizeof(AssertParameterTypeIsValid<Arguments...>) >= 0, "");
	};

} // namespace rr

#endif // rr_Traits_hpp