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

Base class defining logic common to all promise types, aka the "write" end of an awaitable. More...

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

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

Public Member Functions
promise_base &	operator= (const promise_base &)=delete
	Copy assignment is disabled. More...
promise_base &	operator= (promise_base &&rhs)=delete
	Move assignment is disabled. 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 = result_t< T >
	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 ()
	Unlinks this promise from its currently linked awaiter and returns it. More...
	promise_base ()=default
	Construct a new promise, with empty result. More...
	promise_base (const promise_base &)=delete
	Copy construction is disabled. More...
	promise_base (promise_base &&rhs)=delete
	Move construction is disabled. More...

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...

Friends
class	awaitable< T >

Detailed Description

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

Base class defining logic common to all promise types, aka the "write" end of an awaitable.

Member Typedef Documentation

storage_type

template<typename T >

using dpp::detail::promise::promise_base< T >::storage_type = result_t<T>

protected

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

Constructor & Destructor Documentation

promise_base() [1/3]

template<typename T >

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

protecteddefault

Construct a new promise, with empty result.

promise_base() [2/3]

template<typename T >

dpp::detail::promise::promise_base< T >::promise_base ( const promise_base< T > &  )

protecteddelete

Copy construction is disabled.

promise_base() [3/3]

template<typename T >

dpp::detail::promise::promise_base< T >::promise_base ( promise_base< T > &&  rhs )

protecteddelete

Move construction is disabled.

awaitable hold a pointer to this object so moving is not possible.

Member Function Documentation

get_awaitable()

template<typename T >

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

inline

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 ( )

inline

Notify a currently awaiting coroutine that the result is ready.

Note

This may resume the coroutine on the current thread.

Exceptions

?	Any exception thrown by the coroutine if resumed will propagate

operator=() [1/2]

template<typename T >

promise_base& dpp::detail::promise::promise_base< T >::operator= ( const promise_base< T > &  )

delete

Copy assignment is disabled.

operator=() [2/2]

template<typename T >

promise_base& dpp::detail::promise::promise_base< T >::operator= ( promise_base< T > &&  rhs )

delete

Move assignment is disabled.

release_awaiter()

template<typename T >

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

inlineprotected

Unlinks this promise from its currently linked awaiter and returns it.

At the time of writing this is only used in the case of a serious internal error in dpp::task. Avoid using this as this will crash if the promise is used after this.

set_exception()

template<typename T >

template<bool Notify = true>

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

inline

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.
?	Any exception thrown by the coroutine if resumed will propagate

throw_if_not_empty()

template<typename T >

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

inlineprotected

Check if the result is empty, throws otherwise.

Exceptions

dpp::logic_exception

if the result isn't empty.

Friends And Related Function Documentation

awaitable< T >

template<typename T >

friend class awaitable< T >

friend

Member Data Documentation

awaiter

template<typename T >

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

protected

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

protected

State of the awaitable tied to this promise.

value

template<typename T >

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

protected

State of the result value.

See also

storage_type

Note

use .index() instead of std::holds_alternative to support promise_base<std::exception_ptr> and promise_base<std::monostate> :)