dpp::task< R > Class Template Reference

A coroutine task. It starts immediately on construction and can be co_await-ed, making it perfect for parallel coroutines returning a value. More...

#include <coro/task.h>

Inheritance diagram for dpp::task< R >:

Collaboration diagram for dpp::task< R >:

Public Member Functions
	task ()=default
	Default constructor, creates a task not bound to a coroutine. More...
	task (const task &)=delete
	Copy constructor is disabled. More...
	task (task &&other) noexcept
	Move constructor, grabs another task's coroutine handle. More...
	~task ()
	Destructor. More...
task &	operator= (const task &)=delete
	Copy assignment is disabled. More...
task &	operator= (task &&other) noexcept
	Move assignment, grabs another task's coroutine handle. More...
bool	done () const noexcept
	Function to check if the task has finished its execution entirely. More...
dpp::task< R > &	cancel () &noexcept
	Cancel the task, it will stop the next time it uses co_await. On co_await-ing this task, throws dpp::task_cancelled_exception. More...
bool	await_ready () const
	Check whether or not a call to co_await will suspend the caller. More...
auto &	operator co_await () &noexcept
	Suspend the current coroutine until the task completes. More...
const auto &	operator co_await () const &noexcept
	Suspend the current coroutine until the task completes. More...
auto &&	operator co_await () &&noexcept
	Suspend the current coroutine until the task completes. More...

Private Member Functions
dpp::task< R > &&	cancel () &&noexcept
	Cancel the task, it will stop the next time it uses co_await. On co_await-ing this task, throws dpp::task_cancelled_exception. More...

Friends
class	detail::task::task_base< R >
	Internal use only base class containing common logic between task<R> and task<void>. It also serves to prevent await_suspend and await_resume from being used directly. More...

Detailed Description

template<typename R>
class dpp::task< R >

A coroutine task. It starts immediately on construction and can be co_await-ed, making it perfect for parallel coroutines returning a value.

Warning

- This feature is EXPERIMENTAL. The API may change at any time and there may be bugs. Please report any to GitHub Issues or to our Discord Server.

Template Parameters

R	Return type of the task. Cannot be a reference but can be void.

Constructor & Destructor Documentation

task() [1/3]

template<typename R >

dpp::task< R >::task ( )

default

Default constructor, creates a task not bound to a coroutine.

task() [2/3]

template<typename R >

dpp::task< R >::task ( const task< R > &  )

delete

Copy constructor is disabled.

task() [3/3]

template<typename R >

dpp::task< R >::task ( task< R > &&  other )

noexcept

Move constructor, grabs another task's coroutine handle.

Parameters

other

Task to move the handle from

~task()

template<typename R >

dpp::task< R >::~task

(

)

Destructor.

Destroys the handle.

Warning

The coroutine must be finished before this is called, otherwise it runs the risk of being resumed after it is destroyed, resuming in use-after-free undefined behavior.

Member Function Documentation

await_ready()

template<typename R >

bool dpp::task< R >::await_ready

(

)

const

Check whether or not a call to co_await will suspend the caller.

This function is called by the standard library as a first step when using co_await. If it returns true then the caller is not suspended.

Exceptions

logic_exception

if the task is empty.

Returns

bool Whether not to suspend the caller or not

cancel()

template<typename R >

dpp::task< R > & dpp::task< R >::cancel ( ) &

noexcept

Cancel the task, it will stop the next time it uses co_await. On co_await-ing this task, throws dpp::task_cancelled_exception.

done()

template<typename R >

bool dpp::task< R >::done ( ) const

noexcept

Function to check if the task has finished its execution entirely.

Returns

bool Whether the task is finished.

operator co_await() [1/3]

template<typename R >

auto && dpp::task< R >::operator co_await ( ) &&

inlinenoexcept

Suspend the current coroutine until the task completes.

Exceptions

On	resumption, any exception thrown by the coroutine is propagated to the caller.

Returns

On resumption, this expression evaluates to the result object of type R, as an rvalue reference.

operator co_await() [2/3]

template<typename R >

auto & dpp::task< R >::operator co_await ( ) &

inlinenoexcept

Suspend the current coroutine until the task completes.

Exceptions

On	resumption, any exception thrown by the coroutine is propagated to the caller.

Returns

On resumption, this expression evaluates to the result object of type R, as a reference.

operator co_await() [3/3]

template<typename R >

const auto & dpp::task< R >::operator co_await ( ) const &

inlinenoexcept

Suspend the current coroutine until the task completes.

Exceptions

On	resumption, any exception thrown by the coroutine is propagated to the caller.

Returns

On resumption, this expression evaluates to the result object of type R, as a const reference.

operator=() [1/2]

template<typename R >

task & dpp::task< R >::operator= ( const task< R > &  )

delete

Copy assignment is disabled.

operator=() [2/2]

template<typename R >

task & dpp::task< R >::operator= ( task< R > &&  other )

noexcept

Move assignment, grabs another task's coroutine handle.

Parameters

other

Task to move the handle from

Friends And Related Function Documentation

detail::task::task_base< R >

template<typename R >

friend class detail::task::task_base< R >

friend

Internal use only base class containing common logic between task<R> and task<void>. It also serves to prevent await_suspend and await_resume from being used directly.

Warning

For internal use only, do not use.

See also

operator co_await()