swt::Task< T > Class Template Reference

RAII wrapper for coroutines with proper continuation chaining. More...

#include <Task.h>

Collaboration diagram for swt::Task< T >:

Public Types
using	promise_type = TaskPromise< T >
using	Handle = typename promise_type::Handle

Public Member Functions
	Task (Handle handle)
	Construct task with coroutine handle.
	~Task ()
	Destructor - automatically destroys coroutine handle.
	Task (const Task &)=delete
Task &	operator= (const Task &)=delete
	Task (Task &&other) noexcept
	Move constructor.
Task &	operator= (Task &&other) noexcept
	Move assignment operator.
void	start ()
	Start the coroutine execution.
bool	done () const noexcept
	Check if the task has completed.
auto	getResult () -> T
	Get the result value (non-blocking)
void	getResult ()
	Get the result for void tasks (non-blocking)
bool	await_ready () const noexcept
	Check if task is ready (awaitable interface)
void	await_suspend (std::coroutine_handle<> waiter) noexcept
	Suspend awaiting coroutine until this task completes.
auto	await_resume () -> T
	Get result when co_await completes (non-void version)
void	await_resume ()
	Complete co_await for void tasks.
bool	isReady () const noexcept
	Check if task is ready without blocking.

Detailed Description

template<typename T>
class swt::Task< T >

RAII wrapper for coroutines with proper continuation chaining.

Task<T> provides a type-safe, move-only wrapper around C++20 coroutines with support for proper asynchronous execution and continuation chaining.

Template Parameters

T	The return type of the coroutine

Key features:

• RAII management: Automatic coroutine handle cleanup
• Move-only semantics: Prevents accidental copying
• Awaitable interface: Can be co_awaited by other coroutines
• Thread-safe: Safe to await from multiple threads
• Exception propagation: Proper exception handling across await boundaries

Task<int> computeAsync() {
    co_await std::suspend_always{};
    co_return 42;
}
 
Task<void> example() {
    int result = co_await computeAsync();
    std::cout << "Result: " << result << std::endl;
}

Note

Tasks must be started manually with start() and are lazy by default

Warning

Task objects must not be copied - move-only for resource safety

Definition at line 303 of file Task.h.

Member Typedef Documentation

Handle

template<typename T >

using swt::Task< T >::Handle = typename promise_type::Handle

Definition at line 306 of file Task.h.

promise_type

template<typename T >

using swt::Task< T >::promise_type = TaskPromise<T>

Definition at line 305 of file Task.h.

Constructor & Destructor Documentation

Task() [1/3]

template<typename T >

swt::Task< T >::Task ( Handle  handle )

inlineexplicit

Construct task with coroutine handle.

Parameters

handle

Coroutine handle from promise.get_return_object()

Definition at line 312 of file Task.h.

~Task()

template<typename T >

swt::Task< T >::~Task ( )

inline

Destructor - automatically destroys coroutine handle.

Definition at line 317 of file Task.h.

Task() [2/3]

template<typename T >

swt::Task< T >::Task ( const Task< T > &  )

delete

Task() [3/3]

template<typename T >

swt::Task< T >::Task ( Task< T > &&  other )

inlinenoexcept

Move constructor.

Parameters

other

Task to move from

Definition at line 331 of file Task.h.

Member Function Documentation

await_ready()

template<typename T >

bool swt::Task< T >::await_ready ( ) const

inlinenoexcept

Check if task is ready (awaitable interface)

Returns

true if task completed, false if still running

Definition at line 409 of file Task.h.

References swt::Task< T >::done().

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await_resume() [1/2]

template<typename T >

void swt::Task< T >::await_resume ( )

inline

Complete co_await for void tasks.

Exceptions

std::exception_ptr

if coroutine threw an exception

Definition at line 449 of file Task.h.

References swt::Task< T >::getResult().

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await_resume() [2/2]

template<typename T >

auto swt::Task< T >::await_resume ( ) -> T

inline

Get result when co_await completes (non-void version)

Returns

The result value

Exceptions

std::exception_ptr

if coroutine threw an exception

Definition at line 441 of file Task.h.

References swt::Task< T >::getResult().

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await_suspend()

template<typename T >

void swt::Task< T >::await_suspend ( std::coroutine_handle<>  waiter )

inlinenoexcept

Suspend awaiting coroutine until this task completes.

Parameters

waiter

Handle to the coroutine that's awaiting this task

This method implements proper continuation chaining. The waiting coroutine will be resumed when this task completes.

Definition at line 420 of file Task.h.

done()

template<typename T >

bool swt::Task< T >::done ( ) const

inlinenoexcept

Check if the task has completed.

Returns

true if coroutine has finished execution

Definition at line 364 of file Task.h.

Referenced by swt::Task< T >::await_ready().

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getResult() [1/2]

template<typename T >

void swt::Task< T >::getResult ( )

inline

Get the result for void tasks (non-blocking)

Exceptions

std::runtime_error	if task not completed or invalid handle
std::exception_ptr	if coroutine threw an exception

Definition at line 393 of file Task.h.

getResult() [2/2]

template<typename T >

auto swt::Task< T >::getResult ( ) -> T

inline

Get the result value (non-blocking)

Returns

The result value

Exceptions

std::runtime_error	if task not completed or invalid handle
std::exception_ptr	if coroutine threw an exception

This method does not block. Use co_await or check done() first.

Definition at line 376 of file Task.h.

Referenced by swt::Task< T >::await_resume(), and swt::Task< T >::await_resume().

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isReady()

template<typename T >

bool swt::Task< T >::isReady ( ) const

inlinenoexcept

Check if task is ready without blocking.

Returns

true if task completed, false if still running

Definition at line 457 of file Task.h.

operator=() [1/2]

template<typename T >

Task & swt::Task< T >::operator= ( const Task< T > &  )

delete

operator=() [2/2]

template<typename T >

Task & swt::Task< T >::operator= ( Task< T > &&  other )

inlinenoexcept

Move assignment operator.

Parameters

other

Task to move from

Returns

Reference to this task

Definition at line 338 of file Task.h.

start()

template<typename T >

void swt::Task< T >::start ( )

inline

Start the coroutine execution.

Tasks are lazy by default and must be explicitly started. This resumes the coroutine from its initial suspend point.

Definition at line 354 of file Task.h.

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The documentation for this class was generated from the following file:

• include/Task.h