Struct ActualWaker

struct ActualWaker {
    data: Weak<Shared>,
    id: Ti,
}

Actual implementor of Wake for use in a Waker

Futures (eg, channels from [futures]) will use this to wake a task when it should be polled.

This type must not be Cloned with the Data lock held. Consequently, a Waker mustn’t either.

Fields

data: Weak<Shared>

Executor state

The Waker mustn’t to hold a strong reference to the executor, since typically a task holds a future that holds a Waker, and the executor holds the task - so that would be a cycle.

id: Ti

Which task this is

Implementations

impl ActualWaker

fn upgrade_data(&self) -> Option<Arc<Shared>>

Obtain a strong reference to the executor’s data

fn wake(&self)

Wake the task corresponding to this ActualWaker

This is like <Self as std::task::Wake>::wake() but takes &self, not Arc

fn make_waker(shared: &Arc<Shared>, id: TaskId) -> Waker

Create and return a Waker for task id

impl ActualWaker

Using ActualWaker in a RawWaker

We need to make a Waker (the safe, type-erased, waker, used by actual futures) which contains an ActualWaker (our actual waker implementation, also safe).

std offers Waker::from<Arc<impl Wake>>. But we want a bespoke Clone implementation, so we don’t want to use Arc.

So instead, we implement the RawWaker API in terms of ActualWaker. We keep the ActualWaker in a Box, and actually clone it (and the Box).

SAFETY

• The data pointer is Box::<ActualWaker>::into_raw()
• We share these when we clone
• No-one is allowed &mut ActualWaker unless there are no other clones
• So we may make references &ActualWaker

fn new_waker(self) -> Waker

Wrap up an ActualWaker as a type-erased Waker for passing to futures etc.

fn raw_new(self) -> RawWaker

Helper: wrap up an ActualWaker as a RawWaker.

unsafe fn raw_clone(self_: *const ()) -> RawWaker

Implementation of RawWakerVTable’s clone

unsafe fn raw_wake(self_: *const ())

Implementation of RawWakerVTable’s wake

unsafe fn raw_wake_by_ref(self_: *const ())

Implementation of RawWakerVTable’s wake_ref_by

unsafe fn raw_drop(self_: *const ())

Implementation of RawWakerVTable’s drop

Trait Implementations

impl Clone for ActualWaker

Track sleep locations via <Waker as Clone>.

See MockExecutor::debug_dump for the explanation.

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl EnsureSyncSend for ActualWaker