Struct wait_list::Wait

pub struct Wait<'wait_list, L: Lock, I, O, OnCancel> where
    OnCancel: CancelCallback<'wait_list, L, I, O>,  { /* private fields */ }

The future of a waiting operation.

This type provides a lower-level API than LockedExclusive::init_and_wait, but is useful if your guard types are !Send but you still want the outer future to remain Send.

Awaiting and polling this future will panic if you have not called init yet.

Implementations

impl<'wait_list, L: Lock, I, O, OnCancel> Wait<'wait_list, L, I, O, OnCancel> where
    OnCancel: CancelCallback<'wait_list, L, I, O>, 

pub fn new() -> Self

Create a new Wait future.

The returned future will be in its “completed” state, so attempting to .await it will panic unless init is called.

pub fn is_completed(&self) -> bool

Check whether this future is in its completed state or not.

pub fn init(
    self: Pin<&mut Self>,
    waker: Waker,
    guard: &mut LockedExclusive<'wait_list, L, I, O>,
    input: I,
    on_cancel: OnCancel
)

Initialize the future, moving it from a completed to waiting state.

This function is mostly only useful inside a poll function (when you have a cx variable to hand). After calling this, you should return Poll::Pending as the given waker has been successfully registered in the wait list.

A callback must be supplied to call in the event that the future has been woken but was cancelled before it could complete. You will often want to re-call LockedExclusive::wake_one in this case to pass on the notification to someone else.

Panics

Panics if called on a non-completed future.

pub fn init_without_waker(
    self: Pin<&mut Self>,
    guard: &mut LockedExclusive<'wait_list, L, I, O>,
    input: I,
    on_cancel: OnCancel
)

The same as init but not requiring a task::Waker, instead substituting in a temporary no-op waker.

Using this API is always less efficient than writing a poll function manually that calls init, but it can be useful if you (a) need Send futures but have !Send mutex guards and (b) want to stay in an async context.

Trait Implementations

impl<'wait_list, L: Lock, I: Debug, O, OnCancel> Debug for Wait<'wait_list, L, I, O, OnCancel> where
    OnCancel: CancelCallback<'wait_list, L, I, O>,
    L: Debug,
    <L as Lifetime<'wait_list>>::ExclusiveGuard: Debug, 

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

Formats the value using the given formatter.

impl<'wait_list, L: Lock, I, O, OnCancel> Default for Wait<'wait_list, L, I, O, OnCancel> where
    OnCancel: CancelCallback<'wait_list, L, I, O>, 

fn default() -> Self

Returns the “default value” for a type.

impl<'wait_list, L: Lock, I, O, OnCancel> Drop for Wait<'wait_list, L, I, O, OnCancel> where
    OnCancel: CancelCallback<'wait_list, L, I, O>, 

fn drop(&mut self)

Executes the destructor for this type.

impl<'wait_list, L: Lock, I, O, OnCancel> Future for Wait<'wait_list, L, I, O, OnCancel> where
    OnCancel: CancelCallback<'wait_list, L, I, O>, 

type Output = (LockedExclusive<'wait_list, L, I, O>, O)

The type of value produced on completion.

fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.