Struct LocalWaker

pub struct LocalWaker { /* private fields */ }

A synchronization primitive for task wakeup.

Sometimes the task interested in a given event will change over time. An LocalWaker can coordinate concurrent notifications with the consumer potentially “updating” the underlying task to wake up. This is useful in scenarios where a computation completes in another task and wants to notify the consumer, but the consumer is in the process of being migrated to a new logical task.

Consumers should call register before checking the result of a computation and producers should call wake after producing the computation (this differs from the usual thread::park pattern). It is also permitted for wake to be called before register. This results in a no-op.

A single LocalWaker may be reused for any number of calls to register or wake.

Implementations

impl LocalWaker

pub fn new() -> Self

Create an LocalWaker.

pub fn with(waker: Option<Waker>) -> Self

Create an LocalWaker.

pub fn register(&self, waker: &Waker) -> bool

Registers the waker to be notified on calls to wake.

Returns true if waker was registered before.

pub fn wake(&self)

Calls wake on the last Waker passed to register.

If register has not been called yet, then this does nothing.

pub fn wake_checked(&self) -> bool

Calls wake on the last Waker passed to register.

If register has not been called yet, then this returns false.

pub fn take(&self) -> Option<Waker>

Returns the last Waker passed to register, so that the user can wake it.

If a waker has not been registered, this returns None.

Trait Implementations

impl Clone for LocalWaker

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LocalWaker

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for LocalWaker

fn default() -> LocalWaker

Returns the “default value” for a type.