pw::async2::Task Class Reference

Overview

A task which may complete one or more asynchronous operations.

The Task interface is commonly implemented by users wishing to schedule work on an asynchronous Dispatcher. To do this, users may subclass Task, providing an implementation of the DoPend method which advances the state of the Task as far as possible before yielding back to the Dispatcher.

This process works similarly to cooperatively-scheduled green threads or coroutines, with a Task representing a single logical "thread" of execution. Unlike some green thread or coroutine implementations, Task does not imply a separately-allocated stack: Task state is most commonly stored in fields of the Task subclass.

Once defined by a user, Tasks may be run by passing them to a Dispatcher via Dispatcher::Post. The Dispatcher will then Pend the Task every time that the Task indicates it is able to make progress.

Note that Task objects must not be destroyed while they are actively being Pend'd by a Dispatcher. To protect against this, be sure to do one of the following:

• Create Task objects whose stack-based lifetimes outlive their associated Dispatcher.
• Call Deregister on the Task prior to its destruction. NOTE that Deregister may not be called from inside the Task's own Pend method.
• Use dynamic task lifetimes. Tasks may be allocated and posted with Dispatcher::Post(allocator_, ...) overloads. Or, a SharedPtr<Task> can be posted with Dispatcher::PostShared.

Inheritance diagram for pw::async2::Task:

Public Member Functions
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 ()

Protected Types
using	Context = ::pw::async2::Context

Private Member Functions
virtual Poll	DoPend (Context &)=0

Friends
class	Dispatcher
class	Waker

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

• pw_async2/public/pw_async2/task.h