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

A task's promise_t type, with special logic for handling nested tasks. More...

#include <task.h>

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

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

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.
void	emplace_value (Args &&... args)
	Construct the result in place by forwarding the arguments, and by default resume any awaiter.
final_awaiter< R >	final_suspend () const noexcept
	Function called by the standard library when the coroutine reaches its last suspension point.
awaitable< R >	get_awaitable ()
	Get an awaitable object for this promise.
dpp::task< R >	get_return_object () noexcept
	Function called by the standard library when the coroutine is created.
std_coroutine::suspend_never	initial_suspend () const noexcept
	Function called by the standard library when the coroutine is created.
void	notify_awaiter ()
	Notify a currently awaiting coroutine that the result is ready.
void	return_value (const R &expr) noexcept(std::is_nothrow_copy_constructible_v< R >)
	Function called by the standard library when the coroutine co_returns a value.
void	return_value (R &&expr) noexcept(std::is_nothrow_move_constructible_v< R >)
	Function called by the standard library when the coroutine co_returns a value.
template<typename T> requires (!std::is_same_v<R, std::remove_cvref_t<T>> && std::convertible_to<T, R>)
void	return_value (T &&expr) noexcept(std::is_nothrow_convertible_v< T, R >)
	Function called by the standard library when the coroutine co_returns a value.
void	set_exception (std::exception_ptr ptr)
	Set this promise to an exception and resume any awaiter.
void	set_value (U &&v)
	Construct the result by forwarding reference, and resume any awaiter.
void	unhandled_exception ()
	Function called by the standard library when an exception is thrown and not caught in the coroutine.

Public Attributes
std::atomic< bool >	cancelled = false
	Whether the task is cancelled or not.

Protected Types
using	storage_type
	Variant representing one of either 3 states of the result value : empty, result, exception.

Protected Member Functions
std_coroutine::coroutine_handle	release_awaiter ()
	Unlinks this promise from its currently linked awaiter and returns it.
void	throw_if_not_empty ()
	Check if the result is empty, throws otherwise.

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

Friends
struct	final_awaiter< R >

Detailed Description

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

A task's promise_t type, with special logic for handling nested tasks.

Implementation of task::promise_t for non-void return type.

Template Parameters

R	Return type of the task

Member Typedef Documentation

storage_type

using dpp::detail::promise::promise_base< R >::storage_type

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

inlinenodiscardnoexceptinherited

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

emplace_value()

void dpp::basic_promise< R >::emplace_value ( Args &&... 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.

final_suspend()

template<typename R>

final_awaiter< R > dpp::detail::task::promise_t< R >::final_suspend ( ) const

inlinenodiscardnoexcept

Function called by the standard library when the coroutine reaches its last suspension point.

Returns

final_awaiter Special object containing the chain resolution and clean-up logic.

get_awaitable()

awaitable< R > dpp::detail::promise::promise_base< R >::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.

get_return_object()

template<typename R>

dpp::task< R > dpp::detail::task::promise_t< R >::get_return_object ( )

inlinenodiscardnoexcept

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

Returns

dpp::task The coroutine object

initial_suspend()

template<typename R>

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

inlinenoexceptinherited

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

Returns

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

notify_awaiter()

void dpp::detail::promise::promise_base< R >::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()

std_coroutine::coroutine_handle dpp::detail::promise::promise_base< R >::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.

return_value() [1/3]

template<typename R>

void dpp::detail::task::promise_t< R >::return_value ( const R & expr )

inlinenoexcept

Function called by the standard library when the coroutine co_returns a value.

Stores the value internally to hand to the caller when it resumes.

Parameters

expr	The value given to co_return

return_value() [2/3]

template<typename R>

void dpp::detail::task::promise_t< R >::return_value ( R && expr )

inlinenoexcept

Function called by the standard library when the coroutine co_returns a value.

Stores the value internally to hand to the caller when it resumes.

Parameters

expr	The value given to co_return

return_value() [3/3]

template<typename R>

template<typename T>
requires (!std::is_same_v<R, std::remove_cvref_t<T>> && std::convertible_to<T, R>)

void dpp::detail::task::promise_t< R >::return_value ( T && expr )

inlinenoexcept

Function called by the standard library when the coroutine co_returns a value.

Stores the value internally to hand to the caller when it resumes.

Parameters

expr	The value given to co_return

set_exception()

void dpp::detail::promise::promise_base< R >::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

set_value()

void dpp::basic_promise< R >::set_value ( U && v )

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.

throw_if_not_empty()

void dpp::detail::promise::promise_base< R >::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 ( )

inlineinherited

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

Friends And Related Symbol Documentation

final_awaiter< R >

template<typename R>

friend struct final_awaiter< R >

friend

Member Data Documentation

awaiter

std_coroutine::coroutine_handle dpp::detail::promise::promise_base< R >::awaiter

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

inherited

Whether the task is cancelled or not.

state

std::atomic<uint8_t> dpp::detail::promise::promise_base< R >::state

protectedinherited

State of the awaitable tied to this promise.

value

storage_type dpp::detail::promise::promise_base< R >::value

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> :)