Redcraft/Redcraft.Utility/Source/Public/Templates/Any.h

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#pragma once
#include "CoreTypes.h"
#include "Memory/Memory.h"
#include "Memory/Alignment.h"
#include "Templates/Utility.h"
#include "Templates/TypeHash.h"
#include "TypeTraits/TypeTraits.h"
#include "Miscellaneous/Compare.h"
#include "Miscellaneous/AssertionMacros.h"
NAMESPACE_REDCRAFT_BEGIN
NAMESPACE_MODULE_BEGIN(Redcraft)
NAMESPACE_MODULE_BEGIN(Utility)
// NOTE: In the STL, the assignment operation of the std::any type uses the copy-and-swap idiom
// instead of directly calling the assignment operation of the contained value.
// The purpose of this is as follows:
// 1) the copy assignment might not exist.
// 2) the typical case is that the objects are different.
// 3) it is less exception-safe
// But we don't follow the the copy-and-swap idiom, because we assume that no function throws an exception.
NAMESPACE_PRIVATE_BEGIN
template <typename T>
concept CFAnyPlaceable = CDestructible<TDecay<T>> && CCopyConstructible<TDecay<T>> && CMoveConstructible<TDecay<T>>;
NAMESPACE_PRIVATE_END
/**
* The class any describes a type-safe container for single values of any copy and move constructible type.
* An object of class any stores an instance of any type that satisfies the constructor requirements or is empty,
* and this is referred to as the state of the class any object. The stored instance is called the contained object.
*/
class alignas(16) FAny final
{
public:
/** Constructs an empty object. */
FORCEINLINE constexpr FAny() { Invalidate(); }
/** Constructs an empty object. */
FORCEINLINE constexpr FAny(FInvalid) : FAny() { }
/** Copies content of other into a new instance. This may use the object's copy constructor. */
FAny(const FAny& InValue)
: TypeInfo(InValue.TypeInfo)
{
if (!IsValid()) return;
switch (GetRepresentation())
{
case ERepresentation::Empty:
break;
case ERepresentation::Trivial:
Memory::Memcpy(TrivialStorage.Internal, InValue.TrivialStorage.Internal);
break;
case ERepresentation::Small:
SmallStorage.RTTI = InValue.SmallStorage.RTTI;
SmallStorage.RTTI->CopyConstruct(&SmallStorage.Internal, &InValue.SmallStorage.Internal);
break;
case ERepresentation::Big:
BigStorage.RTTI = InValue.BigStorage.RTTI;
BigStorage.External = Memory::Malloc(BigStorage.RTTI->TypeSize, BigStorage.RTTI->TypeAlignment);
BigStorage.RTTI->CopyConstruct(BigStorage.External, InValue.BigStorage.External);
break;
default: check_no_entry();
}
}
/** Moves content of other into a new instance. This may use the object's move constructor. */
FAny(FAny&& InValue)
: TypeInfo(InValue.TypeInfo)
{
if (!IsValid()) return;
switch (GetRepresentation())
{
case ERepresentation::Empty:
break;
case ERepresentation::Trivial:
Memory::Memmove(TrivialStorage.Internal, InValue.TrivialStorage.Internal);
break;
case ERepresentation::Small:
SmallStorage.RTTI = InValue.SmallStorage.RTTI;
SmallStorage.RTTI->MoveConstruct(&SmallStorage.Internal, &InValue.SmallStorage.Internal);
break;
case ERepresentation::Big:
BigStorage.RTTI = InValue.BigStorage.RTTI;
BigStorage.External = InValue.BigStorage.External;
InValue.Invalidate();
break;
default: check_no_entry();
}
}
/** Constructs an object with initial content an object of type TDecay<T>, direct-initialized from Forward<T>(InValue). */
template <typename T> requires (!CSameAs<FAny, TDecay<T>> && !CTInPlaceType<TDecay<T>>
&& NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<TDecay<T>, T&&>)
FORCEINLINE FAny(T&& InValue) : FAny(InPlaceType<T>, Forward<T>(InValue))
{ }
/** Constructs an object with initial content an object of type TDecay<T>, direct-non-list-initialized from Forward<Ts>(Args).... */
template <typename T, typename... Ts> requires (NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<TDecay<T>, Ts&&...>)
FORCEINLINE explicit FAny(TInPlaceType<T>, Ts&&... Args)
{
EmplaceImpl<T>(Forward<Ts>(Args)...);
}
/** Constructs an object with initial content an object of type TDecay<T>, direct-non-list-initialized from IL, Forward<Ts>(Args).... */
template <typename T, typename U, typename... Ts> requires (NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<TDecay<T>, initializer_list<U>, Ts&&...>)
FORCEINLINE explicit FAny(TInPlaceType<T>, initializer_list<U> IL, Ts&&... Args)
{
EmplaceImpl<T>(IL, Forward<Ts>(Args)...);
}
/** Destroys the contained object, if any, as if by a call to Reset(). */
FORCEINLINE ~FAny()
{
Destroy();
}
/** Assigns by copying the state of 'InValue'. This may use the object's copy constructor or copy assignment operator. */
FAny& operator=(const FAny& InValue)
{
if (&InValue == this) UNLIKELY return *this;
if (!InValue.IsValid())
{
Reset();
}
else if (GetTypeInfo() == InValue.GetTypeInfo())
{
switch (GetRepresentation())
{
case ERepresentation::Empty:
break;
case ERepresentation::Trivial:
Memory::Memcpy(TrivialStorage.Internal, InValue.TrivialStorage.Internal);
break;
case ERepresentation::Small:
SmallStorage.RTTI = InValue.SmallStorage.RTTI;
SmallStorage.RTTI->CopyAssign(&SmallStorage.Internal, &InValue.SmallStorage.Internal);
break;
case ERepresentation::Big:
BigStorage.RTTI = InValue.BigStorage.RTTI;
BigStorage.RTTI->CopyAssign(BigStorage.External, InValue.BigStorage.External);
break;
default: check_no_entry();
}
}
else
{
Destroy();
TypeInfo = InValue.TypeInfo;
switch (GetRepresentation())
{
case ERepresentation::Empty:
break;
case ERepresentation::Trivial:
Memory::Memcpy(TrivialStorage.Internal, InValue.TrivialStorage.Internal);
break;
case ERepresentation::Small:
SmallStorage.RTTI = InValue.SmallStorage.RTTI;
SmallStorage.RTTI->CopyConstruct(&SmallStorage.Internal, &InValue.SmallStorage.Internal);
break;
case ERepresentation::Big:
BigStorage.RTTI = InValue.BigStorage.RTTI;
BigStorage.External = Memory::Malloc(BigStorage.RTTI->TypeSize, BigStorage.RTTI->TypeAlignment);
BigStorage.RTTI->CopyConstruct(BigStorage.External, InValue.BigStorage.External);
break;
default: check_no_entry();
}
}
return *this;
}
/** Assigns by moving the state of 'InValue'. This may use the object's move constructor or move assignment operator. */
FAny& operator=(FAny&& InValue)
{
if (&InValue == this) UNLIKELY return *this;
if (!InValue.IsValid())
{
Reset();
}
else if (GetTypeInfo() == InValue.GetTypeInfo())
{
switch (GetRepresentation())
{
case ERepresentation::Empty:
break;
case ERepresentation::Trivial:
Memory::Memmove(TrivialStorage.Internal, InValue.TrivialStorage.Internal);
break;
case ERepresentation::Small:
SmallStorage.RTTI = InValue.SmallStorage.RTTI;
SmallStorage.RTTI->MoveAssign(&SmallStorage.Internal, &InValue.SmallStorage.Internal);
break;
case ERepresentation::Big:
Destroy();
BigStorage.RTTI = InValue.BigStorage.RTTI;
BigStorage.External = InValue.BigStorage.External;
InValue.Invalidate();
break;
default: check_no_entry();
}
}
else
{
Destroy();
TypeInfo = InValue.TypeInfo;
switch (GetRepresentation())
{
case ERepresentation::Empty:
break;
case ERepresentation::Trivial:
Memory::Memmove(TrivialStorage.Internal, InValue.TrivialStorage.Internal);
break;
case ERepresentation::Small:
SmallStorage.RTTI = InValue.SmallStorage.RTTI;
SmallStorage.RTTI->MoveConstruct(&SmallStorage.Internal, &InValue.SmallStorage.Internal);
break;
case ERepresentation::Big:
BigStorage.RTTI = InValue.BigStorage.RTTI;
BigStorage.External = InValue.BigStorage.External;
InValue.Invalidate();
break;
default: check_no_entry();
}
}
return *this;
}
/** Assigns the type and value of 'InValue'. This may use the object's constructor or assignment operator. */
template <typename T> requires (!CSameAs<FAny, TDecay<T>> && !CTInPlaceType<TDecay<T>>
&& NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<TDecay<T>, T&&>)
FORCEINLINE FAny& operator=(T&& InValue)
{
using DecayedType = TDecay<T>;
if constexpr (CAssignableFrom<DecayedType, T&&>)
{
if (HoldsAlternative<DecayedType>())
{
GetValue<DecayedType>() = Forward<T>(InValue);
return *this;
}
}
Destroy();
EmplaceImpl<DecayedType>(Forward<T>(InValue));
return *this;
}
/** Check if the contained value is equivalent to 'InValue'. */
template <typename T> requires (!CSameAs<FAny, TRemoveCVRef<T>> && NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CEqualityComparable<T>)
NODISCARD FORCEINLINE constexpr bool operator==(const T& InValue) const&
{
return HoldsAlternative<T>() ? GetValue<T>() == InValue : false;
}
/** Check that the contained value is in ordered relationship with 'InValue'. */
template <typename T> requires (!CSameAs<FAny, TRemoveCVRef<T>> && NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CSynthThreeWayComparable<T>)
NODISCARD FORCEINLINE constexpr partial_ordering operator<=>(const T& InValue) const&
{
return HoldsAlternative<T>() ? SynthThreeWayCompare(GetValue<T>(), InValue) : partial_ordering::unordered;
}
/** @return true if instance does not contain a value, otherwise false. */
NODISCARD FORCEINLINE constexpr bool operator==(FInvalid) const& { return !IsValid(); }
/**
* Changes the contained object to one of type TDecay<T> constructed from the arguments.
* First destroys the current contained object (if any) by Reset(), then constructs an object of type
* TDecay<T>, direct-non-list-initialized from Forward<Ts>(Args)..., as the contained object.
*
* @param Args - The arguments to be passed to the constructor of the contained object.
*
* @return A reference to the new contained object.
*/
template <typename T, typename... Ts> requires (NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<TDecay<T>, Ts&&...>)
FORCEINLINE TDecay<T>& Emplace(Ts&&... Args)
{
Destroy();
EmplaceImpl<T>(Forward<Ts>(Args)...);
return GetValue<TDecay<T>>();
}
/**
* Changes the contained object to one of type TDecay<T> constructed from the arguments.
* First destroys the current contained object (if any) by Reset(), then constructs an object of type
* TDecay<T>, direct-non-list-initialized from IL, Forward<Ts>(Args)..., as the contained object.
*
* @param IL, Args - The arguments to be passed to the constructor of the contained object.
*
* @return A reference to the new contained object.
*/
template <typename T, typename U, typename... Ts> requires (NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<TDecay<T>, initializer_list<U>, Ts&&...>)
FORCEINLINE TDecay<T>& Emplace(initializer_list<U> IL, Ts&&... Args)
{
Destroy();
EmplaceImpl<T>(IL, Forward<Ts>(Args)...);
return GetValue<TDecay<T>>();
}
/** @return The typeid of the contained value if instance is non-empty, otherwise typeid(void). */
NODISCARD FORCEINLINE constexpr const type_info& GetTypeInfo() const { return IsValid() ? GetTypeInfoImpl() : typeid(void); }
/** @return true if instance contains a value, otherwise false. */
NODISCARD FORCEINLINE constexpr bool IsValid() const { return TypeInfo != 0; }
NODISCARD FORCEINLINE constexpr explicit operator bool() const { return TypeInfo != 0; }
/** @return true if the any currently holds the alternative 'T', false otherwise. */
template <typename T> NODISCARD FORCEINLINE constexpr bool HoldsAlternative() const { return IsValid() ? GetTypeInfo() == typeid(T) : false; }
/** @return The contained object. */
template <typename T> requires (CSameAs<T, TDecay<T>> && NAMESPACE_PRIVATE::CFAnyPlaceable<T>)
NODISCARD FORCEINLINE constexpr T& GetValue() & { checkf(HoldsAlternative<T>(), TEXT("It is an error to call GetValue() on an wrong TAny. Please either check HoldsAlternative() or use Get(DefaultValue) instead.")); return *reinterpret_cast< T*>(GetStorage()); }
/** @return The contained object. */
template <typename T> requires (CSameAs<T, TDecay<T>> && NAMESPACE_PRIVATE::CFAnyPlaceable<T>)
NODISCARD FORCEINLINE constexpr T&& GetValue() && { checkf(HoldsAlternative<T>(), TEXT("It is an error to call GetValue() on an wrong TAny. Please either check HoldsAlternative() or use Get(DefaultValue) instead.")); return MoveTemp(*reinterpret_cast< T*>(GetStorage())); }
/** @return The contained object. */
template <typename T> requires (CSameAs<T, TDecay<T>> && NAMESPACE_PRIVATE::CFAnyPlaceable<T>)
NODISCARD FORCEINLINE constexpr const T& GetValue() const& { checkf(HoldsAlternative<T>(), TEXT("It is an error to call GetValue() on an wrong TAny. Please either check HoldsAlternative() or use Get(DefaultValue) instead.")); return *reinterpret_cast<const T*>(GetStorage()); }
/** @return The contained object. */
template <typename T> requires (CSameAs<T, TDecay<T>> && NAMESPACE_PRIVATE::CFAnyPlaceable<T>)
NODISCARD FORCEINLINE constexpr const T&& GetValue() const&& { checkf(HoldsAlternative<T>(), TEXT("It is an error to call GetValue() on an wrong TAny. Please either check HoldsAlternative() or use Get(DefaultValue) instead.")); return MoveTemp(*reinterpret_cast<const T*>(GetStorage())); }
/** @return The contained object when HoldsAlternative<T>() returns true, 'DefaultValue' otherwise. */
template <typename T> requires (CSameAs<T, TDecay<T>> && NAMESPACE_PRIVATE::CFAnyPlaceable<T>)
NODISCARD FORCEINLINE constexpr T& Get( T& DefaultValue) & { return HoldsAlternative<T>() ? GetValue<T>() : DefaultValue; }
/** @return The contained object when HoldsAlternative<T>() returns true, 'DefaultValue' otherwise. */
template <typename T> requires (CSameAs<T, TDecay<T>> && NAMESPACE_PRIVATE::CFAnyPlaceable<T>)
NODISCARD FORCEINLINE constexpr const T& Get(const T& DefaultValue) const& { return HoldsAlternative<T>() ? GetValue<T>() : DefaultValue; }
/** If not empty, destroys the contained object. */
FORCEINLINE void Reset()
{
Destroy();
Invalidate();
}
/** Overloads the Swap algorithm for FAny. */
friend void Swap(FAny& A, FAny& B)
{
if (!A.IsValid() && !B.IsValid()) return;
if (A.IsValid() && !B.IsValid())
{
B = MoveTemp(A);
A.Reset();
}
else if (!A.IsValid() && B.IsValid())
{
A = MoveTemp(B);
B.Reset();
}
else
{
FAny Temp = MoveTemp(A);
A = MoveTemp(B);
B = MoveTemp(Temp);
}
}
private:
struct FRTTI
{
const size_t TypeSize;
const size_t TypeAlignment;
using FCopyConstruct = void(*)(void*, const void*);
using FMoveConstruct = void(*)(void*, void*);
using FCopyAssign = void(*)(void*, const void*);
using FMoveAssign = void(*)(void*, void*);
using FDestruct = void(*)(void* );
using FSwapObject = void(*)(void*, void*);
const FCopyConstruct CopyConstruct;
const FMoveConstruct MoveConstruct;
const FCopyAssign CopyAssign;
const FMoveAssign MoveAssign;
const FDestruct Destruct;
const FSwapObject SwapObject;
template <typename T>
FORCEINLINE constexpr FRTTI(TInPlaceType<T>)
: TypeSize( sizeof(T)), TypeAlignment(alignof(T))
, CopyConstruct(
[](void* A, const void* B)
{
new (A) T(*reinterpret_cast<const T*>(B));
}
)
, MoveConstruct(
[](void* A, void* B)
{
new (A) T(MoveTemp(*reinterpret_cast<T*>(B)));
}
)
, CopyAssign(
[](void* A, const void* B)
{
if constexpr (CCopyAssignable<T>)
{
*reinterpret_cast<T*>(A) = *reinterpret_cast<const T*>(B);
}
else
{
reinterpret_cast<T*>(A)->~T();
new (A) T(*reinterpret_cast<const T*>(B));
}
}
)
, MoveAssign(
[](void* A, void* B)
{
if constexpr (CMoveAssignable<T>)
{
*reinterpret_cast<T*>(A) = MoveTemp(*reinterpret_cast<T*>(B));
}
else
{
reinterpret_cast<T*>(A)->~T();
new (A) T(MoveTemp(*reinterpret_cast<T*>(B)));
}
}
)
, Destruct(
[](void* A)
{
reinterpret_cast<T*>(A)->~T();
}
)
, SwapObject{
[](void* A, void* B)
{
if constexpr (CSwappable<T>)
{
Swap(*reinterpret_cast<T*>(A), *reinterpret_cast<T*>(B));
}
else
{
TAlignedStorage<sizeof(T), alignof(T)> TempBuffer;
new (&TempBuffer) T(MoveTemp(*reinterpret_cast<T*>(A)));
reinterpret_cast<T*>(A)->~T();
new (A) T(MoveTemp(*reinterpret_cast<T*>(B)));
reinterpret_cast<T*>(B)->~T();
new (B) T(MoveTemp(*reinterpret_cast<T*>(&TempBuffer)));
reinterpret_cast<T*>(&TempBuffer)->~T();
}
}
}
{ }
};
struct FTrivialStorage
{
uint8 Internal[64 - sizeof(uintptr)];
};
struct FSmallStorage
{
uint8 Internal[sizeof(FTrivialStorage) - sizeof(const FRTTI*)];
const FRTTI* RTTI;
};
struct FBigStorage
{
uint8 Padding[sizeof(FTrivialStorage) - sizeof(void*) - sizeof(const FRTTI*)];
void* External;
const FRTTI* RTTI;
};
static_assert(sizeof(FTrivialStorage) == sizeof(FSmallStorage));
static_assert(sizeof(FTrivialStorage) == sizeof( FBigStorage));
static_assert(alignof(type_info) >= 4);
static constexpr uintptr_t RepresentationMask = 3;
enum class ERepresentation : uintptr
{
Empty = 0, // EmptyType
Trivial = 1, // TrivialStorage
Small = 2, // SmallStorage
Big = 3, // BigStorage
};
union
{
FTrivialStorage TrivialStorage;
FSmallStorage SmallStorage;
FBigStorage BigStorage;
};
uintptr TypeInfo;
FORCEINLINE ERepresentation GetRepresentation() const { return static_cast<ERepresentation>(TypeInfo & RepresentationMask); }
FORCEINLINE const type_info& GetTypeInfoImpl() const { return *reinterpret_cast<const type_info*>(TypeInfo & ~RepresentationMask); }
FORCEINLINE void* GetStorage()
{
switch (GetRepresentation())
{
case ERepresentation::Empty: return nullptr;
case ERepresentation::Trivial: return &TrivialStorage.Internal;
case ERepresentation::Small: return &SmallStorage.Internal;
case ERepresentation::Big: return BigStorage.External;
default: check_no_entry(); return nullptr;
}
}
FORCEINLINE const void* GetStorage() const
{
switch (GetRepresentation())
{
case ERepresentation::Empty: return nullptr;
case ERepresentation::Trivial: return &TrivialStorage.Internal;
case ERepresentation::Small: return &SmallStorage.Internal;
case ERepresentation::Big: return BigStorage.External;
default: check_no_entry(); return nullptr;
}
}
template <typename T, typename... Ts>
void EmplaceImpl(Ts&&... Args)
{
using DecayedType = TDecay<T>;
TypeInfo = reinterpret_cast<uintptr>(&typeid(DecayedType));
if constexpr (CEmpty<DecayedType> && CTrivial<DecayedType>) return; // ERepresentation::Empty
constexpr bool bIsTriviallyStorable = sizeof(DecayedType) <= sizeof(TrivialStorage.Internal) && alignof(DecayedType) <= alignof(FAny) && CTriviallyCopyable<DecayedType>;
constexpr bool bIsSmallStorable = sizeof(DecayedType) <= sizeof( SmallStorage.Internal) && alignof(DecayedType) <= alignof(FAny);
static constexpr const FRTTI SelectedRTTI(InPlaceType<DecayedType>);
if constexpr (bIsTriviallyStorable)
{
new (&TrivialStorage.Internal) DecayedType(Forward<Ts>(Args)...);
TypeInfo |= static_cast<uintptr>(ERepresentation::Trivial);
}
else if constexpr (bIsSmallStorable)
{
new (&SmallStorage.Internal) DecayedType(Forward<Ts>(Args)...);
SmallStorage.RTTI = &SelectedRTTI;
TypeInfo |= static_cast<uintptr>(ERepresentation::Small);
}
else
{
BigStorage.External = Memory::Malloc(sizeof(DecayedType), alignof(DecayedType));
new (BigStorage.External) DecayedType(Forward<Ts>(Args)...);
BigStorage.RTTI = &SelectedRTTI;
TypeInfo |= static_cast<uintptr>(ERepresentation::Big);
}
}
void Destroy()
{
if (!IsValid()) return;
switch (GetRepresentation())
{
case ERepresentation::Empty:
case ERepresentation::Trivial:
break;
case ERepresentation::Small:
SmallStorage.RTTI->Destruct(&SmallStorage.Internal);
break;
case ERepresentation::Big:
BigStorage.RTTI->Destruct(BigStorage.External);
Memory::Free(BigStorage.External);
break;
default: check_no_entry();
}
}
FORCEINLINE constexpr void Invalidate() { TypeInfo = 0; }
};
static_assert(sizeof(FAny) == 64, "The byte size of FAny is unexpected");
static_assert(alignof(FAny) == 16, "The byte alignment of FAny is unexpected");
/** Creates an any object that does not contain a value. */
template <typename T> requires (NAMESPACE_PRIVATE::CFAnyPlaceable<T>)
NODISCARD FORCEINLINE constexpr FAny MakeAny(FInvalid)
{
return FAny(Invalid);
}
/** Creates an any object from value. */
template <typename T> requires (NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<TDecay<T>, T>)
NODISCARD FORCEINLINE constexpr FAny MakeAny(T&& InValue)
{
return FAny(Forward<T>(InValue));
}
/** Creates an any object constructed in-place from Args.... */
template <typename T, typename... Ts> requires (NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<T, Ts...>)
NODISCARD FORCEINLINE constexpr FAny MakeAny(Ts&&... Args)
{
return FAny(InPlaceType<TDecay<T>>, Forward<T>(Args)...);
}
/** Creates an any object constructed in-place from IL, Args.... */
template <typename T, typename U, typename... Ts> requires (NAMESPACE_PRIVATE::CFAnyPlaceable<T> && CConstructibleFrom<T, initializer_list<U>, Ts...>)
NODISCARD FORCEINLINE constexpr FAny MakeAny(initializer_list<U> IL, Ts&&... Args)
{
return FAny(InPlaceType<TDecay<T>>, IL, Forward<T>(Args)...);
}
NAMESPACE_MODULE_END(Utility)
NAMESPACE_MODULE_END(Redcraft)
NAMESPACE_REDCRAFT_END