uni20::async::shared_storage< T > Class Template Reference

A lightweight, thread-safe, reference-counted storage for a single object. More...

#include <shared_storage.hpp>

Public Types
using	element_type = T

Public Member Functions
bool	constructed () const noexcept
	Reports whether a value is currently constructed.
void const *	control_address () const noexcept
	Returns the storage control-block address for diagnostics.
void	destroy () noexcept
	Destroy the contained object while keeping the control block alive.
template<typename... Args> requires std::constructible_from<T, Args...>
T &	emplace (Args &&... args)
	Destroy any existing value and construct a new one in place.
const T *	get () const noexcept
	Returns a const pointer to the constructed value.
T *	get () noexcept
	Returns a mutable pointer to the constructed value.
bool	has_lifetime_owner () const noexcept
	Reports whether this value retains another storage control block.
	operator bool () const noexcept
	Returns true when a control block is present.
bool	operator! () const noexcept
	Returns true when no control block is present.
const T &	operator* () const noexcept
	Dereference access to the constructed value.
T &	operator* () noexcept
	Dereference access to the constructed value.
const T *	operator-> () const noexcept
	Pointer-style const access to the constructed value.
T *	operator-> () noexcept
	Pointer-style mutable access to the constructed value.
shared_storage &	operator= (const shared_storage &other) noexcept
	Copy assignment shares the control block.
shared_storage &	operator= (shared_storage &&other) noexcept
	Move assignment transfers the control block pointer.
void	reset () noexcept
	Release this handle's reference to the control block.
	shared_storage () noexcept=default
	Construct an empty handle with no control block.
	shared_storage (const shared_storage &other) noexcept
	Copy constructor increments control block reference count.
	shared_storage (shared_storage &&other) noexcept
	Move constructor transfers ownership of the control block pointer.
T const *	storage_address () const noexcept
	Return the const address reserved for the contained value.
T *	storage_address () noexcept
	Return the address reserved for the contained value.
T	take () noexcept(std::is_nothrow_move_constructible_v< T >)
	Move the contained value out and destroy the in-place object.
size_t	use_count () const noexcept
	Returns the current strong reference count.
bool	valid () const noexcept
	Reports whether a control block is present.
	~shared_storage ()
	Destructor releases one reference to the control block.

Static Public Member Functions
template<typename... Args>
static shared_storage	make_constructed (Args &&... args)
	Construct storage with an immediately-constructed value.
template<typename... Args>
static shared_storage	make_constructed_alias (detail::shared_storage_control_block *lifetime_owner, Args &&... args)
	Construct a value whose control block retains a separate lifetime owner.

Friends
template<typename U , typename... Args>
shared_storage< U >	make_shared_storage (Args &&... args)
	Create a new shared_storage<T> with T(args...) in-place.
template<typename U , typename Owner , typename... Args>
shared_storage< U >	make_shared_storage_alias (shared_storage< Owner > const &owner, Args &&... args)
	Create storage for a value that keeps another storage value alive.
template<typename U >
shared_storage< U >	make_unconstructed_shared_storage ()
	Create a new shared_storage<T> with an unconstructed T.
class	NodeInfo
bool	operator== (const shared_storage &a, const shared_storage &b) noexcept
	Compare whether two handles reference the same control block.

Detailed Description

template<typename T>
class uni20::async::shared_storage< T >

A lightweight, thread-safe, reference-counted storage for a single object.

Unlike std::shared_ptr<T>, shared_storage<T> can exist in an unconstructed state, allowing delayed or conditional in-place construction via .emplace().

This is useful for async or deferred initialization scenarios, where the lifetime and ownership of an object must be shared across tasks, but construction may not yet have occurred.

Key features:

• Shared ownership via atomic reference counting
• Deferred or repeated construction via .emplace()
• Thread-safe refcounting (like std::shared_ptr)
• Minimal overhead (single heap allocation)

Example:

shared_storage<MyType> s = make_shared_storage<MyType>();
 
if (!s.constructed())
    s.emplace(42, "hello");
 
MyType& ref = s.get();
s.destroy();  // explicitly destroy the contained object

Alias storage can own a lightweight value such as a tensor-view descriptor while retaining one strong reference to another shared_storage control block that owns the underlying data.

Member Typedef Documentation

element_type

template<typename T >

using uni20::async::shared_storage< T >::element_type = T

Constructor & Destructor Documentation

shared_storage() [1/3]

template<typename T >

uni20::async::shared_storage< T >::shared_storage ( )

defaultnoexcept

Construct an empty handle with no control block.

shared_storage() [2/3]

template<typename T >

uni20::async::shared_storage< T >::shared_storage ( const shared_storage< T > &  other )

inlinenoexcept

Copy constructor increments control block reference count.

Parameters

other

Source handle.

shared_storage() [3/3]

template<typename T >

uni20::async::shared_storage< T >::shared_storage ( shared_storage< T > &&  other )

inlinenoexcept

Move constructor transfers ownership of the control block pointer.

Parameters

other

Source handle.

~shared_storage()

template<typename T >

uni20::async::shared_storage< T >::~shared_storage ( )

inline

Destructor releases one reference to the control block.

Member Function Documentation

constructed()

template<typename T >

bool uni20::async::shared_storage< T >::constructed ( ) const

inlinenoexcept

Reports whether a value is currently constructed.

Returns

true if the control block exists and holds a constructed value.

control_address()

template<typename T >

void const * uni20::async::shared_storage< T >::control_address ( ) const

inlinenoexcept

Returns the storage control-block address for diagnostics.

Returns

Raw control-block address, or nullptr when no control block is present.

destroy()

template<typename T >

void uni20::async::shared_storage< T >::destroy ( )

inlinenoexcept

Destroy the contained object while keeping the control block alive.

emplace()

template<typename T >

template<typename... Args>
requires std::constructible_from<T, Args...>

T & uni20::async::shared_storage< T >::emplace ( Args &&...  args )

inline

Destroy any existing value and construct a new one in place.

Template Parameters

Args	Constructor argument types.

Parameters

args	Constructor arguments forwarded to T.

Returns

Reference to the newly constructed value.

get() [1/2]

template<typename T >

const T * uni20::async::shared_storage< T >::get ( ) const

inlinenoexcept

Returns a const pointer to the constructed value.

Returns

nullptr when no constructed value is present.

get() [2/2]

template<typename T >

T * uni20::async::shared_storage< T >::get ( )

inlinenoexcept

Returns a mutable pointer to the constructed value.

Returns

nullptr when no constructed value is present.

has_lifetime_owner()

template<typename T >

bool uni20::async::shared_storage< T >::has_lifetime_owner ( ) const

inlinenoexcept

Reports whether this value retains another storage control block.

Returns

true for an alias value with a separate lifetime owner.

make_constructed()

template<typename T >

template<typename... Args>

static shared_storage uni20::async::shared_storage< T >::make_constructed ( Args &&...  args )

inlinestatic

Construct storage with an immediately-constructed value.

Template Parameters

Args	Constructor argument types.

Parameters

args	Constructor arguments forwarded to T.

Returns

New shared_storage<T> containing a constructed value.

make_constructed_alias()

template<typename T >

template<typename... Args>

static shared_storage uni20::async::shared_storage< T >::make_constructed_alias ( detail::shared_storage_control_block *  lifetime_owner, Args &&...  args  )

inlinestatic

Construct a value whose control block retains a separate lifetime owner.

operator bool()

template<typename T >

uni20::async::shared_storage< T >::operator bool ( ) const

inlineexplicitnoexcept

Returns true when a control block is present.

Returns

Equivalent to valid().

operator!()

template<typename T >

bool uni20::async::shared_storage< T >::operator! ( ) const

inlinenoexcept

Returns true when no control block is present.

Returns

Negation of valid().

operator*() [1/2]

template<typename T >

const T & uni20::async::shared_storage< T >::operator* ( ) const

inlinenoexcept

Dereference access to the constructed value.

Returns

Const reference to the contained value.

operator*() [2/2]

template<typename T >

T & uni20::async::shared_storage< T >::operator* ( )

inlinenoexcept

Dereference access to the constructed value.

Returns

Reference to the contained value.

operator->() [1/2]

template<typename T >

const T * uni20::async::shared_storage< T >::operator-> ( ) const

inlinenoexcept

Pointer-style const access to the constructed value.

Returns

Pointer to the contained value.

operator->() [2/2]

template<typename T >

T * uni20::async::shared_storage< T >::operator-> ( )

inlinenoexcept

Pointer-style mutable access to the constructed value.

Returns

Pointer to the contained value.

operator=() [1/2]

template<typename T >

shared_storage & uni20::async::shared_storage< T >::operator= ( const shared_storage< T > &  other )

inlinenoexcept

Copy assignment shares the control block.

Parameters

other

Source handle.

Returns

Reference to *this.

operator=() [2/2]

template<typename T >

shared_storage & uni20::async::shared_storage< T >::operator= ( shared_storage< T > &&  other )

inlinenoexcept

Move assignment transfers the control block pointer.

Parameters

other

Source handle.

Returns

Reference to *this.

reset()

template<typename T >

void uni20::async::shared_storage< T >::reset ( )

inlinenoexcept

Release this handle's reference to the control block.

storage_address() [1/2]

template<typename T >

T const * uni20::async::shared_storage< T >::storage_address ( ) const

inlinenoexcept

Return the const address reserved for the contained value.

Warning

Do not dereference the returned pointer unless constructed() is true.

storage_address() [2/2]

template<typename T >

T * uni20::async::shared_storage< T >::storage_address ( )

inlinenoexcept

Return the address reserved for the contained value.

This address is stable for the lifetime of the control block and is available before the value is constructed. It is intended for lazy descriptors that store an address but do not dereference it until their shared epoch is readable.

Warning

Do not dereference the returned pointer unless constructed() is true.

take()

template<typename T >

T uni20::async::shared_storage< T >::take ( )

inlinenoexcept

Move the contained value out and destroy the in-place object.

Returns

Moved value.

use_count()

template<typename T >

size_t uni20::async::shared_storage< T >::use_count ( ) const

inlinenoexcept

Returns the current strong reference count.

Returns

Number of shared_storage handles sharing this control block.

valid()

template<typename T >

bool uni20::async::shared_storage< T >::valid ( ) const

inlinenoexcept

Reports whether a control block is present.

Returns

true when this handle owns or shares storage metadata.

Friends And Related Symbol Documentation

make_shared_storage

template<typename T >

template<typename U , typename... Args>

shared_storage< U > make_shared_storage ( Args &&...  args )

friend

Create a new shared_storage<T> with T(args...) in-place.

Template Parameters

T	Stored value type.
Args	Constructor argument types.

Parameters

args	Constructor arguments forwarded to T.

Returns

New shared_storage<T> with a constructed value.

make_shared_storage_alias

template<typename T >

template<typename U , typename Owner , typename... Args>

shared_storage< U > make_shared_storage_alias ( shared_storage< Owner > const &  owner, Args &&...  args  )

friend

Create storage for a value that keeps another storage value alive.

The alias has its own local strong count. Its control block retains one reference to owner, which is released after the alias value is destroyed. Copies of the alias increment only the local count.

Template Parameters

T	Alias value type.
Owner	Lifetime-owner value type.
Args	Alias constructor argument types.

Parameters

owner	Storage whose lifetime must cover the alias value.
args	Arguments forwarded to the alias value constructor.

Returns

Constructed alias storage sharing the owner's lifetime.

make_unconstructed_shared_storage

template<typename T >

template<typename U >

shared_storage< U > make_unconstructed_shared_storage ( )

friend

Create a new shared_storage<T> with an unconstructed T.

NodeInfo

template<typename T >

friend class NodeInfo

friend

operator==

template<typename T >

bool operator== ( const shared_storage< T > &  a, const shared_storage< T > &  b  )

friend

Compare whether two handles reference the same control block.

Parameters

a	Left operand.
b	Right operand.

Returns

true when both handles share identical storage metadata.

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

• shared_storage.hpp