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Public Member Functions | List of all members
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
 
Taskoperator= (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
WaitInterruptedExceptionwhen current_task::IsCancelRequested() and no TaskCancellationBlockers are present.
TaskCancelledExceptionif no result is available because the task was cancelled

Definition at line 50 of file shared_task_with_result.hpp.


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