dpp::detail::promise::promise< T > Class Template Reference

Generic promise class, represents the owning potion of an asynchronous value. More...

Inheritance diagram for dpp::detail::promise::promise< T >:

Collaboration diagram for dpp::detail::promise::promise< T >:

Public Member Functions
template<bool Notify = true, typename... Args>
	requires (std::constructible_from< T, Args... >) void emplace_value(Args &&... args)
	Construct the result in place by forwarding the arguments, and by default resume any awaiter. More...
template<bool Notify = true>
void	set_value (const T &v) requires(std
	Construct the result by copy, and resume any awaiter. More...
template<bool Notify = true>
void	set_value (T &&v) requires(std
	Construct the result by move, and resume any awaiter. More...
template<bool Notify = true>
void	set_exception (std::exception_ptr ptr)
	Set this promise to an exception and resume any awaiter. More...
void	notify_awaiter ()
	Notify a currently awaiting coroutine that the result is ready. More...
awaitable< T >	get_awaitable ()
	Get an awaitable object for this promise. More...

Protected Types
using	storage_type = std::variant< std::monostate, std::conditional_t< std::is_void_v< T >, empty, T >, std::exception_ptr >
	Variant representing one of either 3 states of the result value : empty, result, exception. More...

Protected Member Functions
void	throw_if_not_empty ()
	Check if the result is empty, throws otherwise. More...
std_coroutine::coroutine_handle	release_awaiter ()

Protected Attributes
storage_type	value = std::monostate{}
	State of the result value. More...
std::atomic< uint8_t >	state = sf_none
	State of the awaitable tied to this promise. More...
std_coroutine::coroutine_handle	awaiter = nullptr
	Coroutine handle currently awaiting the completion of this promise. More...

Detailed Description

template<typename T>
class dpp::detail::promise::promise< T >

Generic promise class, represents the owning potion of an asynchronous value.

This class is roughly equivalent to std::promise, with the crucial distinction that the promise IS the shared state. As such, the promise needs to be kept alive for the entire time a value can be retrieved.

Template Parameters

T	Type of the asynchronous value

See also

awaitable

Member Typedef Documentation

storage_type

template<typename T >

using dpp::detail::promise::promise_base< T >::storage_type = std::variant<std::monostate, std::conditional_t<std::is_void_v<T>, empty, T>, std::exception_ptr>

protectedinherited

Variant representing one of either 3 states of the result value : empty, result, exception.

Member Function Documentation

get_awaitable()

template<typename T >

awaitable<T> dpp::detail::promise::promise_base< T >::get_awaitable ( )

inlineinherited

Get an awaitable object for this promise.

Exceptions

dpp::logic_exception

if get_awaitable has already been called on this object.

Returns

awaitable<T> An object that can be co_await-ed to retrieve the value of this promise.

notify_awaiter()

template<typename T >

void dpp::detail::promise::promise_base< T >::notify_awaiter ( )

inlineinherited

Notify a currently awaiting coroutine that the result is ready.

release_awaiter()

template<typename T >

std_coroutine::coroutine_handle dpp::detail::promise::promise_base< T >::release_awaiter ( )

inlineprotectedinherited

requires()

template<typename T >

template<bool Notify = true, typename... Args>

dpp::detail::promise::promise< T >::requires ( std::constructible_from< T, Args... >  ) &&

inline

Construct the result in place by forwarding the arguments, and by default resume any awaiter.

Template Parameters

Notify

Whether to resume any awaiter or not.

Exceptions

dpp::logic_exception

if the promise is not empty.

set_exception()

template<typename T >

template<bool Notify = true>

void dpp::detail::promise::promise_base< T >::set_exception ( std::exception_ptr  ptr )

inlineinherited

Set this promise to an exception and resume any awaiter.

Template Parameters

Notify

Whether to resume any awaiter or not.

Exceptions

dpp::logic_exception

if the promise is not empty.

set_value() [1/2]

template<typename T >

template<bool Notify = true>

void dpp::detail::promise::promise< T >::set_value ( const T &  v )

inline

Construct the result by copy, and resume any awaiter.

Template Parameters

Notify

Whether to resume any awaiter or not.

Exceptions

dpp::logic_exception

if the promise is not empty.

set_value() [2/2]

template<typename T >

template<bool Notify = true>

void dpp::detail::promise::promise< T >::set_value ( T &&  v )

inline

Construct the result by move, and resume any awaiter.

Template Parameters

Notify

Whether to resume any awaiter or not.

Exceptions

dpp::logic_exception

if the promise is not empty.

throw_if_not_empty()

template<typename T >

void dpp::detail::promise::promise_base< T >::throw_if_not_empty ( )

inlineprotectedinherited

Check if the result is empty, throws otherwise.

Exceptions

dpp::logic_exception

if the result isn't empty.

Member Data Documentation

awaiter

template<typename T >

std_coroutine::coroutine_handle dpp::detail::promise::promise_base< T >::awaiter = nullptr

protectedinherited

Coroutine handle currently awaiting the completion of this promise.

state

template<typename T >

std::atomic<uint8_t> dpp::detail::promise::promise_base< T >::state = sf_none

protectedinherited

State of the awaitable tied to this promise.

value

template<typename T >

storage_type dpp::detail::promise::promise_base< T >::value = std::monostate{}

protectedinherited

State of the result value.

See also

storage_type