Struct Borrowed

Source

pub struct Borrowed<'wait_list, I, O> { /* private fields */ }

Expand description

The borrowed contents of a WaitList.

For a given WaitList only one of these may exist at once.

Implementations§

Source §

impl<I, O> Borrowed<'_, I, O>

Source

pub fn is_empty(&self) -> bool

Check whether there are any futures waiting in this list.

Source

pub fn head_input(&self) -> Option<&I>

Retrieve a shared reference to the input given by the head entry in the list, if there is one.

Source

pub fn head_input_mut(&mut self) -> Option<&mut I>

Retrieve a unique reference to the input given by the head entry in the list, if there is one.

Source

pub fn wake_one(&mut self, output: O) -> Result<I, WakeOneError<O>>

Wake and dequeue the first waiter in the queue, if there is one.

Returns ownership of that waiter’s input value.

§Examples

use std::future::Future;
use std::task::Poll;

use unsync::wait_list::WaitList;

let list = WaitList::<u32, u32>::new();
let mut future = Box::pin(list.wait(5));
assert_eq!(future.as_mut().poll(cx), Poll::Pending);
assert_eq!(list.borrow().head_input(), Some(&5));

list.borrow().wake_one(6).unwrap();
assert_eq!(future.as_mut().poll(cx), Poll::Ready(6));
assert_eq!(list.borrow().head_input(), None);

Example waking multiple tasks:

use std::future::Future;
use std::task::Poll;

use unsync::wait_list::WaitList;

let list = WaitList::<u32, u32>::new();

let mut f1 = Box::pin(list.wait(1));
let mut f2 = Box::pin(list.wait(2));
let mut f3 = Box::pin(list.wait(3));

assert_eq!(f1.as_mut().poll(cx), Poll::Pending);
assert_eq!(f2.as_mut().poll(cx), Poll::Pending);

assert!(list.borrow().wake_one(1).is_ok());
assert_eq!(f3.as_mut().poll(cx), Poll::Pending);

assert!(list.borrow().wake_one(2).is_ok());
assert!(list.borrow().wake_one(3).is_ok());

assert_eq!(f1.as_mut().poll(cx), Poll::Ready(1));
assert_eq!(f2.as_mut().poll(cx), Poll::Ready(2));
assert_eq!(f3.as_mut().poll(cx), Poll::Ready(3));

§Errors

Returns an error when there are no wakers in the list.

use unsync::wait_list::WaitList;

let list = WaitList::<(), ()>::new();
list.borrow().wake_one(()).unwrap_err();
assert_eq!(list.borrow().head_input(), None);