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. More...
void	emplace_value (Args &&... args)
	Construct the result in place by forwarding the arguments, and by default resume any awaiter. More...
final_awaiter< R >	final_suspend () const noexcept
	Function called by the standard library when the coroutine reaches its last suspension point. More...
awaitable< T >	get_awaitable ()
	Get an awaitable object for this promise. More...
dpp::task< R >	get_return_object () noexcept
	Function called by the standard library when the coroutine is created. 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...
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. More...
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. More...
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. More...
template<bool Notify = true>
void	set_exception (std::exception_ptr ptr)
	Set this promise to an exception and resume any awaiter. More...
void	set_value ()
	Construct a void result, and resume any awaiter. More...
void	set_value (U &&v)
	Construct the result by forwarding reference, 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...

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

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

inlinenoexceptinherited

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

inlinenoexcept

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()

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.

get_return_object()

template<typename R >

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

inlinenoexcept

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()

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.

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()

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

set_value() [1/2]

void dpp::basic_promise< R >::set_value ( )

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_value() [2/2]

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()

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 ( )

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 Function Documentation

final_awaiter< R >

template<typename R >

friend struct final_awaiter< R >

friend

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

inherited

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> :)