TUAFCoWRef | Unreal Engine 5.8 Documentation

API > API/Plugins > API/Plugins/UAFAnimNode

A reference to a value type that performs Copy-on-Write. A reference is never invalid, it must always be constructed from valid data.

A CoW Reference tracks 3 things:

A pointer to an allocated value
Whether or not it owns the allocated memory (if we own it, the reference is unique)
Whether or not the reference is immutable

For performance reasons, this tracking is performed using a single pointer where the bottom two bits are used to store our metadata. We thus require an alignment of 4 bytes for all allocations.

Mutability is enforced at runtime not through the type system (e.g. with 'const'). The specified allocator will be used when a copy is made and memory is owned by the reference.

Copying or assigning a reference to another always performs a copy where the new reference owns the resulting memory. This occurs regardless whether or not the source/target are mutable/immutable.

It is always safe to query for a const reference using TUAFCoWRef::Get() regardless of whether or not the underlying reference is immutable. However, care must be taken when using TUAFCoWRef::GetMutable(). It is the responsibility of the caller to ensure that the reference is mutable before attempting to use it as such. If the reference is not mutable, TUAFCoWRef::ForceMutable() can be used to convert it.

Two allocators are supported: FDefaultAllocator and TMemStackAllocator.


Name	TUAFCoWRef
Type	class
Header File	/Engine/Plugins/Experimental/UAF/UAFAnimNode/Source/UAFAnimNode/Public/UAF/UAFCoWRef.h
Include Path	#include "UAF/UAFCoWRef.h"

Syntax

template<class ValueType, class AllocatorType>  
class TUAFCoWRef

Constructors

Name	Remarks	Include Path
TUAFCoWRef ( const TUAFCoWRef< ValueType, OtherAllocatorType >& Other )	Constructs a new mutable reference by performing a copy of the input reference.	UAF/UAFCoWRef.h
TUAFCoWRef ()	Disable construction of empty references.	UAF/UAFCoWRef.h
TUAFCoWRef ( const TUAFCoWRef< ValueType, AllocatorType >& Other )	Constructs a new mutable reference by performing a copy of the input reference.	UAF/UAFCoWRef.h
TUAFCoWRef ( TUAFCoWRef< ValueType, AllocatorType >&& Other )	Move a reference into another.	UAF/UAFCoWRef.h

Destructors

Name	Remarks	Include Path	Unreal Specifiers
~TUAFCoWRef()	Destroys the current reference If it owned the memory within, it is freed	UAF/UAFCoWRef.h

Constants

Name	Type	Include Path
FLAGS_MASK	uintptr_t	UAF/UAFCoWRef.h
IS_MUTABLE_FLAG_BIT	uintptr_t	UAF/UAFCoWRef.h
OWNS_MEMORY_FLAG_BIT	uintptr_t	UAF/UAFCoWRef.h
VALUE_PTR_MASK	uintptr_t	UAF/UAFCoWRef.h

Variables

Protected

Name	Type	Remarks	Include Path	Unreal Specifiers
ValuePtrAndFlags	uintptr_t	Stores a pointer to a value and 2 flags in the LSBs.	UAF/UAFCoWRef.h

Functions

Public

Name	Remarks	Include Path
void ForceMutable()	Ensures that this reference is mutable If the current reference was immutable and we do not own the memory, this performs a copy (Copy-on-Write) Note that any existing const references will remain valid since the original owner is keeping it alive	UAF/UAFCoWRef.h
const ValueType & Get()	Returns an immutable reference to the value contained within.	UAF/UAFCoWRef.h
ValueType & GetMutable()	Returns a mutable reference to the value contained within.	UAF/UAFCoWRef.h
bool IsMutable()	Returns whether or not this reference is mutable.	UAF/UAFCoWRef.h
bool IsUnique()	Returns whether or not this reference is unique A reference is unique if we own its memory	UAF/UAFCoWRef.h

Static

Name	Remarks	Include Path
static TUAFCoWRef< ValueType, AllocatorType > MakeFrom ( ValueType&& Value )	Constructs a new mutable reference from the specified value by performing a move of the input.	UAF/UAFCoWRef.h
static TUAFCoWRef< ValueType, AllocatorType > MakeImmutable ( const ValueType* ValuePtr )	Constructs a new immutable reference from the specified value pointer.	UAF/UAFCoWRef.h
static TUAFCoWRef< ValueType, AllocatorType > MakeMutable ( ValueType* ValuePtr )	Constructs a new mutable reference from the specified value pointer.	UAF/UAFCoWRef.h

Operators

Name	Remarks	Include Path
TUAFCoWRef< ValueType, AllocatorType > & operator= ( const TUAFCoWRef< ValueType, AllocatorType >& Other )	Assign a new mutable reference by performing a copy of the input reference.	UAF/UAFCoWRef.h
TUAFCoWRef< ValueType, AllocatorType > & operator= ( const TUAFCoWRef< ValueType, OtherAllocatorType >& Other )	Assign a new mutable reference by performing a copy of the input reference.	UAF/UAFCoWRef.h
TUAFCoWRef< ValueType, AllocatorType > & operator= ( TUAFCoWRef< ValueType, AllocatorType >&& Other )	Move assign a reference into another.	UAF/UAFCoWRef.h
TUAFCoWRef< ValueType, AllocatorType > & operator= ( ValueType&& Value )	Move assign a value into a reference by performing a move of the input.	UAF/UAFCoWRef.h

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