CECCO::details::OnceCache< T > Class Template Reference

Thread-safe single-value cache. More...

#include <helpers.hpp>

Inheritance diagram for CECCO::details::OnceCache< T >:

Public Member Functions
	OnceCache ()=default
	OnceCache (const OnceCache &other)
	OnceCache (OnceCache &&other)
OnceCache &	operator= (const OnceCache &other)
OnceCache &	operator= (OnceCache &&other)
OnceCache &	operator= (const T &value)
OnceCache &	operator= (T &&value)
template<class F>
void	call_once (F &&f) const
template<class... Args>
T &	emplace (Args &&... args) const
bool	has_value () const noexcept
	operator bool () const noexcept
T &	value ()
const T &	value () const
T &	operator* ()
const T &	operator* () const
T *	operator-> ()
const T *	operator-> () const
void	reset () const

Detailed Description

template<class T>
class CECCO::details::OnceCache< T >

Thread-safe single-value cache.

Template Parameters

T	Value type stored in the cache

Stores one optional value together with a std::once_flag. Use call_once() to guard lazy initialization when multiple threads may read the same object. Copying or moving a cache copies or moves the stored value, if any, and creates a fresh once flag.

Note

Classes containing OnceCache members need no hand-written copy or move operations: compiler-generated memberwise operations use the cache's copy and move operations, transferring the cached value while giving each destination cache its own fresh std::once_flag.

Warning

Concurrent reads through call_once() are thread-safe. Assignment, emplace(), and manual value changes are not synchronization points and must not race with other operations.

Usage_Example

mutable OnceCache<size_t> weight;
 
weight.call_once([this] {
    if (weight.has_value()) return;
    weight.emplace(calculate_weight());
});
 
return weight.value();

Definition at line 639 of file helpers.hpp.

Constructor & Destructor Documentation

OnceCache() [1/3]

template<class T>

CECCO::details::OnceCache< T >::OnceCache ( )

default

OnceCache() [2/3]

template<class T>

CECCO::details::OnceCache< T >::OnceCache ( const OnceCache< T > & other )

inline

Definition at line 643 of file helpers.hpp.

OnceCache() [3/3]

template<class T>

CECCO::details::OnceCache< T >::OnceCache ( OnceCache< T > && other )

inline

Definition at line 647 of file helpers.hpp.

Member Function Documentation

call_once()

template<class T>

template<class F>

void CECCO::details::OnceCache< T >::call_once ( F && f ) const

inline

Definition at line 678 of file helpers.hpp.

emplace()

template<class T>

template<class... Args>

T & CECCO::details::OnceCache< T >::emplace ( Args &&... args ) const

inline

Definition at line 683 of file helpers.hpp.

has_value()

template<class T>

bool CECCO::details::OnceCache< T >::has_value ( ) const

inlinenoexcept

Definition at line 687 of file helpers.hpp.

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operator bool()

template<class T>

CECCO::details::OnceCache< T >::operator bool ( ) const

inlineexplicitnoexcept

Definition at line 689 of file helpers.hpp.

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operator*() [1/2]

template<class T>

T & CECCO::details::OnceCache< T >::operator* ( )

inline

Definition at line 695 of file helpers.hpp.

operator*() [2/2]

template<class T>

const T & CECCO::details::OnceCache< T >::operator* ( ) const

inline

Definition at line 697 of file helpers.hpp.

operator->() [1/2]

template<class T>

T * CECCO::details::OnceCache< T >::operator-> ( )

inline

Definition at line 699 of file helpers.hpp.

operator->() [2/2]

template<class T>

const T * CECCO::details::OnceCache< T >::operator-> ( ) const

inline

Definition at line 701 of file helpers.hpp.

operator=() [1/4]

template<class T>

OnceCache & CECCO::details::OnceCache< T >::operator= ( const OnceCache< T > & other )

inline

Definition at line 651 of file helpers.hpp.

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operator=() [2/4]

template<class T>

OnceCache & CECCO::details::OnceCache< T >::operator= ( const T & value )

inline

Definition at line 667 of file helpers.hpp.

operator=() [3/4]

template<class T>

OnceCache & CECCO::details::OnceCache< T >::operator= ( OnceCache< T > && other )

inline

Definition at line 659 of file helpers.hpp.

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operator=() [4/4]

template<class T>

OnceCache & CECCO::details::OnceCache< T >::operator= ( T && value )

inline

Definition at line 672 of file helpers.hpp.

reset()

template<class T>

void CECCO::details::OnceCache< T >::reset ( ) const

inline

Definition at line 703 of file helpers.hpp.

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value() [1/2]

template<class T>

T & CECCO::details::OnceCache< T >::value ( )

inline

Definition at line 691 of file helpers.hpp.

value() [2/2]

template<class T>

const T & CECCO::details::OnceCache< T >::value ( ) const

inline

Definition at line 693 of file helpers.hpp.

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

• helpers.hpp