engine::SharedTaskWithResult< T > Class Template Reference

#include <userver/engine/task/shared_task_with_result.hpp>

Inheritance diagram for engine::SharedTaskWithResult< T >:

Collaboration diagram for engine::SharedTaskWithResult< T >:

Public Member Functions
	SharedTaskWithResult ()=default
	Default constructor.
decltype(auto)	Get () const &noexcept(false)
	Returns (or rethrows) the result of task invocation. Task remains valid after return from this method, thread(coro)-safe.
std::add_lvalue_reference< const T >	Get () &&
Public Member Functions inherited from engine::Task
	Task ()
	Default constructor.
virtual	~Task ()
	Destructor.
	Task (Task &&) noexcept
Task &	operator= (Task &&) noexcept
bool	IsValid () const
	Checks whether this Task object owns an actual task (not State::kInvalid)
State	GetState () const
	Gets the task State.
bool	IsFinished () const
	Returns whether the task finished execution.
void	Wait () const noexcept(false)
	Suspends execution until the task finishes or caller is cancelled. Can be called from coroutine context only. For non-coroutine context use BlockingWait().
template<typename Rep , typename Period >
void	WaitFor (const std::chrono::duration< Rep, Period > &) const noexcept(false)
	Suspends execution until the task finishes or after the specified timeout or until caller is cancelled.
template<typename Clock , typename Duration >
void	WaitUntil (const std::chrono::time_point< Clock, Duration > &) const noexcept(false)
	Suspends execution until the task finishes or until the specified time point is reached or until caller is cancelled.
void	WaitUntil (Deadline) const
	Suspends execution until the task finishes or until the specified deadline is reached or until caller is cancelled.
void	Detach () &&
	Detaches task, allowing it to continue execution out of scope; memory safety is much better with concurrent::BackgroundTaskStorage.
void	RequestCancel ()
	Queues task cancellation request.
void	SyncCancel () noexcept
	Cancels the task and suspends execution until it is finished. Can be called from coroutine context only. For non-coroutine context use RequestCancel() + BlockingWait().
TaskCancellationReason	CancellationReason () const
	Gets task cancellation reason.
void	BlockingWait () const

Additional Inherited Members
Public Types inherited from engine::Task
enum class	Importance {   kNormal ,   kCritical }
	Task importance. More...
enum class	State {   kInvalid ,   kNew ,   kQueued ,   kRunning ,   kSuspended ,   kCancelled ,   kCompleted }
	Task state. More...
enum class	WaitMode {   kSingleWaiter ,   kMultipleWaiters }
	Task wait mode. More...
Static Public Member Functions inherited from engine::Task
static const std::string &	GetStateName (State state)

Detailed Description

template<typename T>
class engine::SharedTaskWithResult< T >

Asynchronous task with result

Example usage:

  // Creating task that will be awaited in parallel
  auto shared_task = utils::SharedAsync("shared_task", []() {
    engine::InterruptibleSleepFor(std::chrono::milliseconds(100));
 
    return 1;
  });
 
  std::vector<engine::TaskWithResult<void>> tasks;
  std::atomic_int sum{0};
  for (size_t i = 0; i < 4; ++i) {
    // Getting shared_task's result in parallel
    tasks.push_back(
        utils::Async("waiter_task", [shared_task /* copy is allowed */,
                                     &sum]() { sum += shared_task.Get(); }));
  }
 
  for (auto& task : tasks) task.Wait();

See also

Synchronization Primitives

Definition at line 35 of file shared_task_with_result.hpp.

Constructor & Destructor Documentation

SharedTaskWithResult()

template<typename T >

engine::SharedTaskWithResult< T >::SharedTaskWithResult ( )

default

Default constructor.

Creates an invalid task.

Member Function Documentation

Get() [1/2]

template<typename T >

std::add_lvalue_reference< const T > engine::SharedTaskWithResult< T >::Get ( ) &&

inline

Definition at line 61 of file shared_task_with_result.hpp.

Get() [2/2]

template<typename T >

decltype(auto) engine::SharedTaskWithResult< T >::Get ( ) const &

inline

Returns (or rethrows) the result of task invocation. Task remains valid after return from this method, thread(coro)-safe.

Returns

const T& or void

Exceptions

WaitInterruptedException	when current_task::IsCancelRequested() and no TaskCancellationBlockers are present.
TaskCancelledException	if no result is available because the task was cancelled

Definition at line 50 of file shared_task_with_result.hpp.

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

• userver/engine/task/shared_task_with_result.hpp