CxxUtils::CachedUniquePtrT< T > Class Template Reference

Cached pointer with atomic update. More...

#include <CachedUniquePtr.h>

Collaboration diagram for CxxUtils::CachedUniquePtrT< T >:

Public Member Functions
	CachedUniquePtrT ()
	Default constructor. Sets the element to null. More...
	CachedUniquePtrT (std::unique_ptr< T > elt)
	Constructor from an element. More...
	CachedUniquePtrT (CachedUniquePtrT &&other) noexcept
	Move constructor. More...
CachedUniquePtrT &	operator= (CachedUniquePtrT &&other) noexcept
	Move. More...
	~CachedUniquePtrT ()
T *	set (std::unique_ptr< T > elt) const
	Atomically set the element. More...
void	store (std::unique_ptr< T > elt) noexcept
	Store a new value to the element. More...
T *	get () const
	Return the current value of the element. More...
T &	operator* () const
	Dereference the element. More...
T *	operator-> () const
	Dereference the element. More...
	operator bool () const
	Test if the element is null. More...
std::unique_ptr< T >	release () noexcept
	Transfer ownership from the element: return the current value as a unique_ptr, leaving the element null. More...

Private Attributes
std::atomic< T * >	m_ptr
	The cached element. More...

Detailed Description

template<class T>
class CxxUtils::CachedUniquePtrT< T >

Cached pointer with atomic update.

This acts as a unique_ptr that may be set atomically through a const method. If the pointer is already set, then the new value is deleted. The intended use case is where one maintains some cached object that is computed lazily. So one can do, for example,

CxxUtils::CachedUniquePtr<Payload> m_payload;
...
const Payload* ...::get() const
{
  if (!m_payload) {
    m_payload.set (std::make_unique<Payload> (...));
  }
  return m_payload.get());
}

This only makes sense if the objects passed to set() are equivalent in all threads. This is generally the case for a lazily-computed value, but this class has no way of enforcing this.

It is recommended to generally use the template CachedUniquePtr, which is specialized for const types. The more general template CachedUniquePtrT can be used with a non-const type (but you don't want to do that for the lazy-cache use case).

Definition at line 53 of file CachedUniquePtr.h.

Constructor & Destructor Documentation

CachedUniquePtrT() [1/3]

template<class T >

CxxUtils::CachedUniquePtrT< T >::CachedUniquePtrT

(

)

Default constructor. Sets the element to null.

CachedUniquePtrT() [2/3]

template<class T >

CxxUtils::CachedUniquePtrT< T >::CachedUniquePtrT

(

std::unique_ptr< T >

elt

)

Constructor from an element.

CachedUniquePtrT() [3/3]

template<class T >

CxxUtils::CachedUniquePtrT< T >::CachedUniquePtrT ( CachedUniquePtrT< T > &&  other )

noexcept

Move constructor.

~CachedUniquePtrT()

template<class T >

CxxUtils::CachedUniquePtrT< T >::~CachedUniquePtrT

(

)

Member Function Documentation

get()

template<class T >

T* CxxUtils::CachedUniquePtrT< T >::get

(

)

const

Return the current value of the element.

operator bool()

template<class T >

CxxUtils::CachedUniquePtrT< T >::operator bool ( ) const

explicit

Test if the element is null.

operator*()

template<class T >

T& CxxUtils::CachedUniquePtrT< T >::operator*

(

)

const

Dereference the element.

operator->()

template<class T >

T* CxxUtils::CachedUniquePtrT< T >::operator->

(

)

const

Dereference the element.

operator=()

template<class T >

CachedUniquePtrT& CxxUtils::CachedUniquePtrT< T >::operator= ( CachedUniquePtrT< T > &&  other )

noexcept

Move.

release()

template<class T >

std::unique_ptr<T> CxxUtils::CachedUniquePtrT< T >::release ( )

noexcept

Transfer ownership from the element: return the current value as a unique_ptr, leaving the element null.

set()

template<class T >

T* CxxUtils::CachedUniquePtrT< T >::set

(

std::unique_ptr< T >

elt

)

const

Atomically set the element.

If already set, then elt is discarded. Returns the final value of the element.

store()

template<class T >

void CxxUtils::CachedUniquePtrT< T >::store ( std::unique_ptr< T >  elt )

noexcept

Store a new value to the element.

Not compatible with other concurrent access.

Member Data Documentation

m_ptr

template<class T >

std::atomic<T*> CxxUtils::CachedUniquePtrT< T >::m_ptr

mutableprivate

The cached element.

Definition at line 109 of file CachedUniquePtr.h.

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The documentation for this class was generated from the following file:

• CachedUniquePtr.h