pub struct Fuse<T> { /* private fields */ }
Expand description
A fusing adapter around a value.
A Fuse<T>
is similar to Option<T>
, with the exception that it provides
and API which is more suitable for interacting with asynchronous tasks and
pinned values.
For most polling operations (except Fuse::poll_inner
), if the value
completes, the adapter will switch to an empty state and
return Poll::Pending
. It can later be updated again with
set.
See Fuse::new
for more details.
Implementations§
Source§impl<T> Fuse<Pin<Box<T>>>
impl<T> Fuse<Pin<Box<T>>>
Sourcepub fn pin(value: T) -> Self
Available on crate feature alloc
only.
pub fn pin(value: T) -> Self
alloc
only.Construct a fusing adapter around a value that is already pinned.
§Examples
use async_fuse::Fuse;
use std::future::Future;
use tokio::time;
async fn foo() -> u32 { 1 }
let mut fut = Fuse::pin(foo());
assert!(!fut.is_empty());
let value = (&mut fut).await;
assert!(fut.is_empty());
Source§impl<T> Fuse<T>
impl<T> Fuse<T>
Sourcepub fn new(value: T) -> Self
pub fn new(value: T) -> Self
Construct a fusing adapter around a value.
§Examples
use std::pin::pin;
use async_fuse::Fuse;
use std::time::Duration;
use tokio::time;
let mut sleep = pin!(Fuse::new(time::sleep(Duration::from_millis(200))));
tokio::select! {
_ = &mut sleep => {
assert!(sleep.is_empty());
sleep.set(Fuse::new(time::sleep(Duration::from_millis(200))));
}
}
assert!(!sleep.is_empty());
§Example using an unsized trait object
use async_fuse::Fuse;
use std::future::Future;
use std::pin::Pin;
use tokio::time;
async fn foo() -> u32 { 1 }
async fn bar() -> u32 { 2 }
let mut fut = Fuse::<Pin<Box<dyn Future<Output = u32>>>>::new(Box::pin(foo()));
let mut total = 0;
while !fut.is_empty() {
let value = (&mut fut).await;
if value == 1 {
fut.set(Box::pin(bar()));
}
total += value;
}
assert_eq!(total, 3);
Sourcepub fn set(&mut self, value: T)where
Self: Unpin,
pub fn set(&mut self, value: T)where
Self: Unpin,
Set the fused value.
§Examples
use async_fuse::Fuse;
use std::time::Duration;
use tokio::time;
let mut sleep = Fuse::new(Box::pin(time::sleep(Duration::from_millis(200))));
assert!(!sleep.is_empty());
sleep.set(Box::pin(time::sleep(Duration::from_millis(200))));
assert!(!sleep.is_empty());
§Example setting an unsized trait object
use async_fuse::Fuse;
use std::future::Future;
use std::pin::Pin;
use tokio::time;
async fn foo() -> u32 { 1 }
async fn bar() -> u32 { 2 }
let mut fut = Fuse::<Pin<Box<dyn Future<Output = u32>>>>::empty();
assert!(fut.is_empty());
fut.set(Box::pin(foo()));
assert!(!fut.is_empty());
fut.set(Box::pin(bar()));
assert!(!fut.is_empty());
Sourcepub fn clear(&mut self)where
Self: Unpin,
pub fn clear(&mut self)where
Self: Unpin,
Clear the fused value.
§Examples
use async_fuse::Fuse;
use std::time::Duration;
use tokio::time;
let mut sleep = Fuse::new(Box::pin(time::sleep(Duration::from_millis(200))));
assert!(!sleep.is_empty());
sleep.clear();
assert!(sleep.is_empty());
Sourcepub fn empty() -> Self
pub fn empty() -> Self
Construct an empty fuse.
§Examples
use std::pin::pin;
use async_fuse::Fuse;
use tokio::time;
let mut sleep = pin!(Fuse::<time::Sleep>::empty());
assert!(sleep.is_empty());
Sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Test if the polled for value is empty.
§Examples
use std::pin::pin;
use async_fuse::Fuse;
use std::time::Duration;
use tokio::time;
let mut sleep = pin!(Fuse::new(time::sleep(Duration::from_millis(200))));
assert!(!sleep.is_empty());
sleep.set(Fuse::empty());
assert!(sleep.is_empty());
Sourcepub fn as_inner_ref(&self) -> Option<&T>
pub fn as_inner_ref(&self) -> Option<&T>
Access the interior value as a reference.
§Examples
use std::pin::pin;
use std::time::Duration;
use async_fuse::Fuse;
use tokio::time;
let mut sleep = pin!(Fuse::new(time::sleep(Duration::from_millis(200))));
assert!(sleep.as_inner_ref().is_some());
sleep.set(Fuse::empty());
assert!(sleep.as_inner_ref().is_none());
Sourcepub async fn poll_inner<P, O>(self: Pin<&mut Self>, poll: P) -> O
pub async fn poll_inner<P, O>(self: Pin<&mut Self>, poll: P) -> O
Poll the current value with the given polling implementation.
This can be used for types which only provides a polling function.
This will never empty the underlying value.
§Examples
use std::pin::pin;
use std::future::Future;
use async_fuse::Fuse;
use tokio::sync::mpsc;
async fn op(n: u32) -> u32 {
n
}
let mut op1 = pin!(Fuse::new(op(1)));
assert_eq!(op1.as_mut().poll_inner(|mut i, cx| i.poll(cx)).await, 1);
assert!(!op1.is_empty());
op1.set(Fuse::new(op(2)));
assert_eq!(op1.as_mut().poll_inner(|mut i, cx| i.poll(cx)).await, 2);
assert!(!op1.is_empty());
Sourcepub async fn poll_future<P, O>(self: Pin<&mut Self>, poll: P) -> O
pub async fn poll_future<P, O>(self: Pin<&mut Self>, poll: P) -> O
Poll the current value with the given polling implementation.
This can be used for types which only provides a polling function.
Once the underlying poll impl returns Poll::Ready
, the underlying
value will be emptied.
§Examples
use std::pin::pin;
use std::future::Future;
use async_fuse::Fuse;
use tokio::sync::mpsc;
async fn op(n: u32) -> u32 {
n
}
let mut op1 = pin!(Fuse::new(op(1)));
assert_eq!(op1.as_mut().poll_future(|mut i, cx| i.poll(cx)).await, 1);
assert!(op1.is_empty());
op1.set(Fuse::new(op(2)));
assert!(!op1.is_empty());
assert_eq!(op1.as_mut().poll_future(|mut i, cx| i.poll(cx)).await, 2);
assert!(op1.is_empty());
Sourcepub async fn poll_stream<P, O>(self: Pin<&mut Self>, poll: P) -> Option<O>
pub async fn poll_stream<P, O>(self: Pin<&mut Self>, poll: P) -> Option<O>
Poll the current value with the given polling implementation.
This can be used for types which only provides a polling function, or types which can be polled multiple streams. Like streams which do not provide a Stream implementation.
Will empty the fused value once the underlying poll returns
Poll::Ready(None)
.
§Examples
use std::pin::pin;
use std::future::Future;
use async_fuse::Fuse;
use futures_core::Stream;
use tokio::sync::mpsc;
fn op(n: u32) -> impl Stream<Item = u32> {
async_stream::stream! {
yield n;
yield n + 1;
}
}
let mut op1 = pin!(Fuse::new(op(1)));
assert!(!op1.is_empty());
assert_eq!(op1.as_mut().poll_stream(|mut i, cx| i.poll_next(cx)).await, Some(1));
assert_eq!(op1.as_mut().poll_stream(|mut i, cx| i.poll_next(cx)).await, Some(2));
assert!(!op1.is_empty());
assert_eq!(op1.as_mut().poll_stream(|mut i, cx| i.poll_next(cx)).await, None);
assert!(op1.is_empty());
Sourcepub fn as_inner_mut(&mut self) -> Option<&mut T>where
Self: Unpin,
pub fn as_inner_mut(&mut self) -> Option<&mut T>where
Self: Unpin,
Sourcepub fn as_pin_mut(&mut self) -> Pin<&mut Self>where
Self: Unpin,
pub fn as_pin_mut(&mut self) -> Pin<&mut Self>where
Self: Unpin,
Helper conversion to a pinned value.
§Examples
use async_fuse::Fuse;
use tokio::sync::mpsc;
let (tx, rx) = mpsc::unbounded_channel::<u32>();
let mut rx = Fuse::new(rx);
tx.send(42);
// Manually poll the sleep.
assert_eq!(rx.as_pin_mut().poll_stream(|mut i, cx| i.poll_recv(cx)).await, Some(42));
rx = Fuse::empty();
assert!(rx.is_empty());
Sourcepub async fn next(&mut self) -> Option<T::Item>
Available on crate feature stream03
only.
pub async fn next(&mut self) -> Option<T::Item>
stream03
only.Poll the next value in the stream where the underlying value is unpin.
Behaves the same as [poll_stream
], except that it only works for
values which are Unpin.
§Examples
use std::future::Future;
use async_fuse::Fuse;
use futures_core::Stream;
use tokio::sync::mpsc;
fn op(n: u32) -> impl Stream<Item = u32> {
async_stream::stream! {
yield n;
yield n + 1;
}
}
let mut stream = Fuse::new(Box::pin(op(1)));
assert!(!stream.is_empty());
assert_eq!(stream.next().await, Some(1));
assert_eq!(stream.next().await, Some(2));
assert_eq!(stream.next().await, None);
assert!(stream.is_empty());
Trait Implementations§
Source§impl<T> Stream for Fuse<T>where
T: Stream03,
Available on crate feature stream03
only.
impl<T> Stream for Fuse<T>where
T: Stream03,
stream03
only.