dpp::detail::task::promise_base< R > Struct Template Reference

Base implementation of task::promise_t, without the logic that would depend on the return type. Meant to be inherited from. More...

Inheritance diagram for dpp::detail::task::promise_base< R >:

Collaboration diagram for dpp::detail::task::promise_base< R >:

Classes
struct	proxy_awaiter
	Proxy awaitable that wraps any co_await inside the task and checks for cancellation on resumption. More...

Public Member Functions
template<awaitable_type T>
auto	await_transform (T &&expr) const noexcept(noexcept(co_await_resolve(std::forward< T >(expr))))
	Function called whenever co_await is used inside of the task. More...
awaitable< T >	get_awaitable ()
	Get an awaitable object for this promise. More...
std_coroutine::suspend_never	initial_suspend () const noexcept
	Function called by the standard library when the coroutine is created. More...
void	notify_awaiter ()
	Notify a currently awaiting coroutine that the result is ready. More...
	requires (std::constructible_from< R, Args... >) void emplace_value(Args &&... args)
	Construct the result in place by forwarding the arguments, and by default resume any awaiter. More...
	requires (std::convertible_to< U &&, R >) void set_value(U &&v)
	Construct the result by forwarding reference, and resume any awaiter. More...
	requires (std::is_void_v< R >) void set_value()
	Construct a void result, 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	unhandled_exception ()
	Function called by the standard library when an exception is thrown and not caught in the coroutine. More...

Public Attributes
std::atomic< bool >	cancelled = false
	Whether the task is cancelled or not. 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
std_coroutine::coroutine_handle	release_awaiter ()
	Unlinks this promise from its currently linked awaiter and returns it. More...
void	throw_if_not_empty ()
	Check if the result is empty, throws otherwise. More...

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

Detailed Description

template<typename R>
struct dpp::detail::task::promise_base< R >

Base implementation of task::promise_t, without the logic that would depend on the return type. Meant to be inherited from.

Member Typedef Documentation

storage_type

template<typename T >

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

protectedinherited

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

Member Function Documentation

await_transform()

template<typename R >

template<awaitable_type T>

auto dpp::detail::task::promise_base< R >::await_transform ( T &&  expr ) const

inlinenoexcept

Function called whenever co_await is used inside of the task.

Exceptions

dpp::task_cancelled_exception

On resumption if the task was cancelled

Returns

proxy_awaiter Returns a proxy awaiter that will check for cancellation on resumption

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.

initial_suspend()

template<typename R >

std_coroutine::suspend_never dpp::detail::task::promise_base< R >::initial_suspend ( ) const

inlinenoexcept

Function called by the standard library when the coroutine is created.

Returns

std::suspend_never Don't suspend, the coroutine starts immediately.

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.

Note

This may resume the coroutine on the current thread.

Exceptions

?	Any exception thrown by the coroutine if resumed will propagate

release_awaiter()

template<typename T >

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

inlineprotectedinherited

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.

requires() [1/3]

dpp::basic_promise< R >::requires ( std::constructible_from< R , Args... >  ) &&

inlineinherited

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.

requires() [2/3]

dpp::basic_promise< R >::requires ( std::convertible_to< U &&, R >  ) &&

inlineinherited

Construct the result by forwarding reference, and resume any awaiter.

Template Parameters

Notify

Whether to resume any awaiter or not.

Exceptions

dpp::logic_exception

if the promise is not empty.

requires() [3/3]

dpp::basic_promise< R >::requires ( std::is_void_v< R >  )

inlineinherited

Construct a void result, 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_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.
?	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 ( )

inlineprotectedinherited

Check if the result is empty, throws otherwise.

Exceptions

dpp::logic_exception

if the result isn't empty.

unhandled_exception()

template<typename R >

void dpp::detail::task::promise_base< R >::unhandled_exception ( )

inline

Function called by the standard library when an exception is thrown and not caught in the coroutine.

Stores the exception pointer to rethrow on co_await. If the task object is destroyed and was not cancelled, throw instead

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.

cancelled

template<typename R >

std::atomic<bool> dpp::detail::task::promise_base< R >::cancelled = false

Whether the task is cancelled or not.

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

Note

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