Invoke.h

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// Copyright Epic Games, Inc. All Rights Reserved.
// Templates for invoking functors
 
#pragma once
 
#include "uLang/Common/Common.h"
#include "uLang/Common/Templates/References.h"
#include "uLang/Common/Templates/TypeTraits.h"
 
namespace uLang
{
 
//------------------------------------------------------------------
// From Invoke.h
 
namespace Private
{
    template <typename BaseType, typename CallableType>
    ULANG_FORCEINLINE auto DereferenceIfNecessary(CallableType&& Callable)
        -> typename TEnableIf<TPointerIsConvertibleFromTo<typename TDecay<CallableType>::Type, typename TDecay<BaseType>::Type>::Value, decltype((CallableType&&)Callable)>::Type
    {
        return (CallableType&&)Callable;
    }
 
    template <typename BaseType, typename CallableType>
    ULANG_FORCEINLINE auto DereferenceIfNecessary(CallableType&& Callable)
        -> typename TEnableIf<!TPointerIsConvertibleFromTo<typename TDecay<CallableType>::Type, typename TDecay<BaseType>::Type>::Value, decltype(*(CallableType&&)Callable)>::Type
    {
        return *(CallableType&&)Callable;
    }
}
 
 
template <typename FuncType, typename... ArgTypes>
ULANG_FORCEINLINE auto Invoke(FuncType&& Func, ArgTypes&&... Args)
    -> decltype(uLang::ForwardArg<FuncType>(Func)(uLang::ForwardArg<ArgTypes>(Args)...))
{
    return uLang::ForwardArg<FuncType>(Func)(uLang::ForwardArg<ArgTypes>(Args)...);
}
 
template <typename ReturnType, typename ObjType, typename CallableType>
ULANG_FORCEINLINE auto Invoke(ReturnType ObjType::*pdm, CallableType&& Callable)
    -> decltype(Private::DereferenceIfNecessary<ObjType>(uLang::ForwardArg<CallableType>(Callable)).*pdm)
{
    return Private::DereferenceIfNecessary<ObjType>(uLang::ForwardArg<CallableType>(Callable)).*pdm;
}
 
template <typename ReturnType, typename ObjType, typename... PMFArgTypes, typename CallableType, typename... ArgTypes>
ULANG_FORCEINLINE auto Invoke(ReturnType (ObjType::*PtrMemFun)(PMFArgTypes...), CallableType&& Callable, ArgTypes&&... Args)
    -> decltype((Private::DereferenceIfNecessary<ObjType>(uLang::ForwardArg<CallableType>(Callable)).*PtrMemFun)(uLang::ForwardArg<ArgTypes>(Args)...))
{
    return (Private::DereferenceIfNecessary<ObjType>(uLang::ForwardArg<CallableType>(Callable)).*PtrMemFun)(uLang::ForwardArg<ArgTypes>(Args)...);
}
 
template <typename ReturnType, typename ObjType, typename... PMFArgTypes, typename CallableType, typename... ArgTypes>
ULANG_FORCEINLINE auto Invoke(ReturnType (ObjType::*PtrMemFun)(PMFArgTypes...) const, CallableType&& Callable, ArgTypes&&... Args)
    -> decltype((Private::DereferenceIfNecessary<ObjType>(uLang::ForwardArg<CallableType>(Callable)).*PtrMemFun)(uLang::ForwardArg<ArgTypes>(Args)...))
{
    return (Private::DereferenceIfNecessary<ObjType>(uLang::ForwardArg<CallableType>(Callable)).*PtrMemFun)(uLang::ForwardArg<ArgTypes>(Args)...);
}
 
 
#define ULANG_PROJECTION(FuncName) \
    [](auto&&... Args) \
    { \
        return FuncName(uLang::ForwardArg<decltype(Args)>(Args)...); \
    }
 
#define ULANG_PROJECTION_MEMBER(Type, FuncName) \
    [](auto&& Obj, auto&&... Args) \
    { \
        return Private::DereferenceIfNecessary<Type>(uLang::ForwardArg<decltype(Obj)>(Obj)).FuncName(uLang::ForwardArg<decltype(Args)>(Args)...); \
    }
 
 //------------------------------------------------------------------
 // From IsInvocable.h
 
namespace Private
{
    template <typename T>
    T&& DeclVal();
 
    template <typename T>
    struct TVoid
    {
        typedef void Type;
    };
 
    template <typename, typename CallableType, typename... ArgTypes>
    struct TIsInvocableImpl
    {
        enum { Value = false };
    };
 
    template <typename CallableType, typename... ArgTypes>
    struct TIsInvocableImpl<typename TVoid<decltype(uLang::Invoke(DeclVal<CallableType>(), DeclVal<ArgTypes>()...))>::Type, CallableType, ArgTypes...>
    {
        enum { Value = true };
    };
}
 
template <typename CallableType, typename... ArgTypes>
struct TIsInvocable : Private::TIsInvocableImpl<void, CallableType, ArgTypes...>
{
};
 
}