wwa::coro::task< Result > Class Template Reference

A coroutine task. More...

#include <task.h>

Collaboration diagram for wwa::coro::task< Result >:

Public Types
using	const_reference = std::add_lvalue_reference_t<std::add_const_t<value_type>>
	Constant version of reference.
using	promise_type = detail::promise_type<Result>
	The promise type associated with the task.
using	reference
	Reference type; Result&& if Result is an rvalue reference, Result& otherwise.
using	rvalue_reference = std::add_rvalue_reference_t<std::remove_cv_t<value_type>>
	Rvalue reference type.
using	value_type = std::remove_reference_t<Result>
	Value type; a Result with all references stripped.

Public Member Functions
	task () noexcept=default
	Default constructor.
	task (task &&other) noexcept
	Move constructor.
	~task ()
	Destructor.
bool	destroy ()
	Destroys the task.
constexpr bool	is_ready () const noexcept
	Checks if the task is ready.
auto	operator co_await () &&noexcept
	Await the result of the task.
auto	operator co_await () const &noexcept
	Await the result of the task.
task &	operator= (task &&other) noexcept
	Move assignment operator.
reference	result_value () &
	Returns the result produced by the task.
rvalue_reference	result_value () &&
	Returns the result produced by the task.
const_reference	result_value () const &
	Returns the result produced by the task.
bool	resume () const
	Resumes the task.

Detailed Description

template<typename Result = void>
class wwa::coro::task< Result >

A coroutine task.

The task class represents a coroutine task that can be used to perform asynchronous operations. A task is a lightweight object that wraps a coroutine and provides a mechanism for resuming the coroutine and obtaining the result of the operation.

Example:

wwa::coro::task<int> task1()
{
    co_return 123;
}
 
wwa::coro::task<int> task2()
{
    co_return 456;
}
 
wwa::coro::task<int> sum()
{
    const auto a = co_await task1();
    const auto b = co_await task2();
    co_return a + b;
}
 
wwa::coro::task<> print()
{
    std::cout << "The result is " << co_await sum() << "\n";
}

Template Parameters

Result

The type of the result produced by the task.

Examples

advance_with_begin.cpp, async_generator.cpp, eager_task.cpp, run_awaitable.cpp, and task.cpp.

Definition at line 196 of file task.h.

Member Typedef Documentation

const_reference

template<typename Result = void>

using wwa::coro::task< Result >::const_reference = std::add_lvalue_reference_t<std::add_const_t<value_type>>

Constant version of reference.

Definition at line 324 of file task.h.

promise_type

template<typename Result = void>

using wwa::coro::task< Result >::promise_type = detail::promise_type<Result>

The promise type associated with the task.

The promise_type alias is a type alias for the promise type associated with the task.

Definition at line 203 of file task.h.

reference

template<typename Result = void>

using wwa::coro::task< Result >::reference

Initial value:

 
        std::conditional_t<std::is_rvalue_reference_v<Result>, Result, std::add_lvalue_reference_t<value_type>>

Reference type; Result&& if Result is an rvalue reference, Result& otherwise.

Definition at line 321 of file task.h.

rvalue_reference

template<typename Result = void>

using wwa::coro::task< Result >::rvalue_reference = std::add_rvalue_reference_t<std::remove_cv_t<value_type>>

Rvalue reference type.

Definition at line 326 of file task.h.

value_type

template<typename Result = void>

using wwa::coro::task< Result >::value_type = std::remove_reference_t<Result>

Value type; a Result with all references stripped.

Definition at line 319 of file task.h.

Constructor & Destructor Documentation

task() [1/2]

template<typename Result = void>

wwa::coro::task< Result >::task ( )

defaultnoexcept

Default constructor.

task() [2/2]

template<typename Result = void>

wwa::coro::task< Result >::task ( task< Result > && other )

inlinenoexcept

Move constructor.

Definition at line 224 of file task.h.

~task()

template<typename Result = void>

wwa::coro::task< Result >::~task ( )

inline

Destructor.

Definition at line 250 of file task.h.

Member Function Documentation

destroy()

template<typename Result = void>

bool wwa::coro::task< Result >::destroy ( )

inline

Destroys the task.

Destroys the task by destroying the associated coroutine handle.

Returns

Operation status.

Return values

true	The task was destroyed.
false	The task was already destroyed or was default-constructed.

Definition at line 307 of file task.h.

is_ready()

template<typename Result = void>

bool wwa::coro::task< Result >::is_ready ( ) const

inlinenodiscardconstexprnoexcept

Checks if the task is ready.

A task is considered ready if it has finished executing or has an empty coroutine handle associated with (for example, a default-constructed task).

A task that is ready cannot be resumed.

Returns

Task state.

Return values

true	The task has finished executing; the result is available.

Returns

false The task has not yet finished executing.

Definition at line 269 of file task.h.

operator co_await() [1/2]

template<typename Result = void>

auto wwa::coro::task< Result >::operator co_await ( ) &&

inlinenoexcept

Await the result of the task.

This operator allows the task to be co_await'ed, returning the result produced by the task. It is used when the task is an rvalue, ensuring that the result is moved.

Definition at line 445 of file task.h.

operator co_await() [2/2]

template<typename Result = void>

auto wwa::coro::task< Result >::operator co_await ( ) const &

inlinenoexcept

Await the result of the task.

This operator allows the task to be co_await'ed, returning the result produced by the task. If the task's result type is an rvalue reference, it returns an rvalue reference to the result. Otherwise, it returns an lvalue reference to the result.

Returns

An awaiter that retrieves the result of the task.

Definition at line 405 of file task.h.

operator=()

template<typename Result = void>

task & wwa::coro::task< Result >::operator= ( task< Result > && other )

inlinenoexcept

Move assignment operator.

Definition at line 234 of file task.h.

result_value() [1/3]

template<typename Result = void>

reference wwa::coro::task< Result >::result_value ( ) &

inline

Returns the result produced by the task.

Returns an lvalue or rvalue (if Result template parameter of the task is an rvalue reference) reference to the result produced by the task.

Returns

The result produced by the task.

Exceptions

bad_task	The task is empty or has been destroyed.
bad_result_access	The result is not yet available.

Definition at line 343 of file task.h.

result_value() [2/3]

template<typename Result = void>

rvalue_reference wwa::coro::task< Result >::result_value ( ) &&

inline

Returns the result produced by the task.

Returns an rvalue reference to the result produced by the task.

Returns

The result produced by the task.

Exceptions

bad_task	The task is empty or has been destroyed.
bad_result_access	The result is not yet available.

Definition at line 386 of file task.h.

result_value() [3/3]

template<typename Result = void>

const_reference wwa::coro::task< Result >::result_value ( ) const &

inline

Returns the result produced by the task.

Returns a constant lvalue reference to the result produced by the task.

Returns

The result produced by the task.

Exceptions

bad_task	The task is empty or has been destroyed.
bad_result_access	The result is not yet available.

Definition at line 368 of file task.h.

resume()

template<typename Result = void>

bool wwa::coro::task< Result >::resume ( ) const

inline

Resumes the task.

Resuming a task causes the associated coroutine to be resumed. A task can only be resumed if it is not ready.

Returns

Task state.

Return values

true	The task has not yet finished executing.
false	The task has finished executing; the result is available.

See also

is_ready()

Definition at line 286 of file task.h.

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

• task.h