pw::async2::FutureTask< T > Class Template Reference

Overview

template<typename T>
class pw::async2::FutureTask< T >

Creates a task that pends a future until it completes.

FutureTask can be initialized in a few ways:

• Move a future: FutureTask task(std::move(future))
• Construct a future in place:FutureTask<MyFuture> task(arg1, arg2)
• Refer to an existing future:FutureTask<MyFuture&> task(future)`

Warning

FutureTask is intended for test and occasional production use. A FutureTask does not contain logic, and relying too much on FutureTasks could push logic out of async tasks, which nullifies the benefits of pw_async2. Creating a task for each future is also less efficient than having one task work with multiple futures.

Inheritance diagram for pw::async2::FutureTask< T >:

Public Types
using	future_type = std::remove_reference_t< T >
	The type of the future that is pended by this task.
using	value_type = typename future_type::value_type
	The type produced by this tasks's future when it completes.

Public Member Functions
template<typename Arg , typename... Args>
constexpr	FutureTask (Arg &&arg, Args &&... args)
Poll< value_type >	TakePoll ()
FutureValue< future_type > &	value () &
const FutureValue< future_type > &	value () const &
FutureValue< future_type > &&	value () &&
const FutureValue< future_type > &&	value () const &&
FutureValue< future_type > &	Wait ()
Public Member Functions inherited from pw::async2::Task
constexpr	Task (log::Token name=kDefaultName)
	Task (const Task &)=delete
	Task (Task &&)=delete
Task &	operator= (const Task &)=delete
Task &	operator= (Task &&)=delete
virtual	~Task ()
Poll	Pend (Context &cx)
bool	IsRegistered () const
void	Deregister ()
void	Join ()

Private Member Functions
Poll	DoPend (Context &cx) override

Additional Inherited Members
Protected Member Functions inherited from pw::containers::future::IntrusiveList< T >::Item
constexpr	Item ()=default

Constructor & Destructor Documentation

FutureTask()

template<typename T >

template<typename Arg , typename... Args>

constexpr pw::async2::FutureTask< T >::FutureTask ( Arg &&  arg, Args &&...  args  )

inlineexplicitconstexpr

Constructs a FutureTask. Forwards arguments to the future's constructor for FutureTasks that own their future. Reference FutureTasks take a mutable reference to their future.

Requires at least one argument. Default constructed futures are not permitted since since they cannot be pended.

Member Function Documentation

DoPend()

template<typename T >

Poll pw::async2::FutureTask< T >::DoPend ( Context &  )

inlineoverrideprivatevirtual

Attempts to advance this Task to completion.

This method should not perform synchronous waiting, as doing so may block the main Dispatcher loop and prevent other Task s from progressing. Because of this, Task s should not invoke blocking Dispatcher methods such as RunUntilComplete.

Tasks should also avoid invoking RunUntilStalled on their own Dispatcher.

Returns Ready if complete, or Pending if the Task was not yet able to complete.

If Pending is returned, the Task must ensure it is woken up when it is able to make progress. To do this, Task::Pend must arrange for Waker::Wake to be called, either by storing a copy of the Waker away to be awoken by another system (such as an interrupt handler).

Implements pw::async2::Task.

TakePoll()

template<typename T >

Poll< value_type > pw::async2::FutureTask< T >::TakePoll ( )

inline

Takes the Poll result from the most recent task run. This function is NOT thread safe. It cannot be called when the task may run on another thread.

value() [1/4]

template<typename T >

FutureValue< future_type > & pw::async2::FutureTask< T >::value ( ) &

inline

Returns the value produced by the future.

Precondition

The task MUST have been joined first.

value() [2/4]

template<typename T >

FutureValue< future_type > && pw::async2::FutureTask< T >::value ( ) &&

inline

Returns the value produced by the future.

Precondition

The task MUST have been joined first.

value() [3/4]

template<typename T >

const FutureValue< future_type > & pw::async2::FutureTask< T >::value ( ) const &

inline

Returns the value produced by the future.

Precondition

The task MUST have been joined first.

value() [4/4]

template<typename T >

const FutureValue< future_type > && pw::async2::FutureTask< T >::value ( ) const &&

inline

Returns the value produced by the future.

Precondition

The task MUST have been joined first.

Wait()

template<typename T >

FutureValue< future_type > & pw::async2::FutureTask< T >::Wait ( )

inline

Joins that task, blocking until the future completes, then returns a reference its value.

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

• pw_async2/public/pw_async2/future_task.h