Trait choices::warp::Future 1.36.0[−][src]
#[must_use = "futures do nothing unless you `.await` or poll them"] pub trait Future { type Output; fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>; }
A future represents an asynchronous computation.
A future is a value that may not have finished computing yet. This kind of “asynchronous value” makes it possible for a thread to continue doing useful work while it waits for the value to become available.
The poll
method
The core method of future, poll
, attempts to resolve the future into a
final value. This method does not block if the value is not ready. Instead,
the current task is scheduled to be woken up when it’s possible to make
further progress by poll
ing again. The context
passed to the poll
method can provide a Waker
, which is a handle for waking up the current
task.
When using a future, you generally won’t call poll
directly, but instead
.await
the value.
Associated Types
Loading content...Required methods
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>
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Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.
Return value
This function returns:
Poll::Pending
if the future is not ready yetPoll::Ready(val)
with the resultval
of this future if it finished successfully.
Once a future has finished, clients should not poll
it again.
When a future is not ready yet, poll
returns Poll::Pending
and
stores a clone of the Waker
copied from the current Context
.
This Waker
is then woken once the future can make progress.
For example, a future waiting for a socket to become
readable would call .clone()
on the Waker
and store it.
When a signal arrives elsewhere indicating that the socket is readable,
Waker::wake
is called and the socket future’s task is awoken.
Once a task has been woken up, it should attempt to poll
the future
again, which may or may not produce a final value.
Note that on multiple calls to poll
, only the Waker
from the
Context
passed to the most recent call should be scheduled to
receive a wakeup.
Runtime characteristics
Futures alone are inert; they must be actively poll
ed to make
progress, meaning that each time the current task is woken up, it should
actively re-poll
pending futures that it still has an interest in.
The poll
function is not called repeatedly in a tight loop – instead,
it should only be called when the future indicates that it is ready to
make progress (by calling wake()
). If you’re familiar with the
poll(2)
or select(2)
syscalls on Unix it’s worth noting that futures
typically do not suffer the same problems of “all wakeups must poll
all events”; they are more like epoll(4)
.
An implementation of poll
should strive to return quickly, and should
not block. Returning quickly prevents unnecessarily clogging up
threads or event loops. If it is known ahead of time that a call to
poll
may end up taking awhile, the work should be offloaded to a
thread pool (or something similar) to ensure that poll
can return
quickly.
Panics
Once a future has completed (returned Ready
from poll
), calling its
poll
method again may panic, block forever, or cause other kinds of
problems; the Future
trait places no requirements on the effects of
such a call. However, as the poll
method is not marked unsafe
,
Rust’s usual rules apply: calls must never cause undefined behavior
(memory corruption, incorrect use of unsafe
functions, or the like),
regardless of the future’s state.
Trait Implementations
Implementations on Foreign Types
impl<F> Future for AssertUnwindSafe<F> where
F: Future,
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impl<F> Future for AssertUnwindSafe<F> where
F: Future,
[src]impl<Fut1, Fut2, Fut3, Fut4, Fut5> Future for TryJoin5<Fut1, Fut2, Fut3, Fut4, Fut5> where
Fut1: TryFuture,
Fut2: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut3: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut4: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut5: TryFuture<Error = <Fut1 as TryFuture>::Error>,
impl<Fut1, Fut2, Fut3, Fut4, Fut5> Future for TryJoin5<Fut1, Fut2, Fut3, Fut4, Fut5> where
Fut1: TryFuture,
Fut2: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut3: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut4: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut5: TryFuture<Error = <Fut1 as TryFuture>::Error>,
type Output = Result<(<Fut1 as TryFuture>::Ok, <Fut2 as TryFuture>::Ok, <Fut3 as TryFuture>::Ok, <Fut4 as TryFuture>::Ok, <Fut5 as TryFuture>::Ok), <Fut1 as TryFuture>::Error>
pub fn poll(
self: Pin<&mut TryJoin5<Fut1, Fut2, Fut3, Fut4, Fut5>>,
cx: &mut Context<'_>
) -> Poll<<TryJoin5<Fut1, Fut2, Fut3, Fut4, Fut5> as Future>::Output>
self: Pin<&mut TryJoin5<Fut1, Fut2, Fut3, Fut4, Fut5>>,
cx: &mut Context<'_>
) -> Poll<<TryJoin5<Fut1, Fut2, Fut3, Fut4, Fut5> as Future>::Output>
impl<Fut1, Fut2, Fut3> Future for Join3<Fut1, Fut2, Fut3> where
Fut1: Future,
Fut2: Future,
Fut3: Future,
impl<Fut1, Fut2, Fut3> Future for Join3<Fut1, Fut2, Fut3> where
Fut1: Future,
Fut2: Future,
Fut3: Future,
impl<F> Future for TryJoinAll<F> where
F: TryFuture,
impl<F> Future for TryJoinAll<F> where
F: TryFuture,
impl<St, Fut, T, F> Future for Fold<St, Fut, T, F> where
F: FnMut(T, <St as Stream>::Item) -> Fut,
Fut: Future<Output = T>,
St: Stream,
impl<St, Fut, T, F> Future for Fold<St, Fut, T, F> where
F: FnMut(T, <St as Stream>::Item) -> Fut,
Fut: Future<Output = T>,
St: Stream,
impl<St, Si> Future for Forward<St, Si> where
St: TryStream,
Forward<St, Si, <St as TryStream>::Ok>: Future,
impl<St, Si> Future for Forward<St, Si> where
St: TryStream,
Forward<St, Si, <St as TryStream>::Ok>: Future,
impl<St, C> Future for TryCollect<St, C> where
C: Default + Extend<<St as TryStream>::Ok>,
St: TryStream,
impl<St, C> Future for TryCollect<St, C> where
C: Default + Extend<<St as TryStream>::Ok>,
St: TryStream,
impl<Fut1, Fut2, F> Future for AndThen<Fut1, Fut2, F> where
TryFlatten<MapOk<Fut1, F>, Fut2>: Future,
impl<Fut1, Fut2, F> Future for AndThen<Fut1, Fut2, F> where
TryFlatten<MapOk<Fut1, F>, Fut2>: Future,
impl<St, Fut, F> Future for ForEachConcurrent<St, Fut, F> where
F: FnMut(<St as Stream>::Item) -> Fut,
Fut: Future<Output = ()>,
St: Stream,
impl<St, Fut, F> Future for ForEachConcurrent<St, Fut, F> where
F: FnMut(<St as Stream>::Item) -> Fut,
Fut: Future<Output = ()>,
St: Stream,
impl<T> Future for Pending<T>
impl<T> Future for Pending<T>
impl<Fut1, Fut2, Fut3, Fut4, Fut5> Future for Join5<Fut1, Fut2, Fut3, Fut4, Fut5> where
Fut1: Future,
Fut2: Future,
Fut3: Future,
Fut4: Future,
Fut5: Future,
impl<Fut1, Fut2, Fut3, Fut4, Fut5> Future for Join5<Fut1, Fut2, Fut3, Fut4, Fut5> where
Fut1: Future,
Fut2: Future,
Fut3: Future,
Fut4: Future,
Fut5: Future,
impl<Fut> Future for TryMaybeDone<Fut> where
Fut: TryFuture,
impl<Fut> Future for TryMaybeDone<Fut> where
Fut: TryFuture,
impl<St, Fut, T, F> Future for TryFold<St, Fut, T, F> where
F: FnMut(T, <St as TryStream>::Ok) -> Fut,
Fut: TryFuture<Ok = T, Error = <St as TryStream>::Error>,
St: TryStream,
impl<St, Fut, T, F> Future for TryFold<St, Fut, T, F> where
F: FnMut(T, <St as TryStream>::Ok) -> Fut,
Fut: TryFuture<Ok = T, Error = <St as TryStream>::Error>,
St: TryStream,
impl<St, Fut, F> Future for TryForEach<St, Fut, F> where
F: FnMut(<St as TryStream>::Ok) -> Fut,
Fut: TryFuture<Ok = (), Error = <St as TryStream>::Error>,
St: TryStream,
impl<St, Fut, F> Future for TryForEach<St, Fut, F> where
F: FnMut(<St as TryStream>::Ok) -> Fut,
Fut: TryFuture<Ok = (), Error = <St as TryStream>::Error>,
St: TryStream,
impl<St, A, B, FromA, FromB> Future for Unzip<St, FromA, FromB> where
St: Stream<Item = (A, B)>,
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
impl<St, A, B, FromA, FromB> Future for Unzip<St, FromA, FromB> where
St: Stream<Item = (A, B)>,
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
impl<Fut1, Fut2, F> Future for OrElse<Fut1, Fut2, F> where
TryFlattenErr<MapErr<Fut1, F>, Fut2>: Future,
impl<Fut1, Fut2, F> Future for OrElse<Fut1, Fut2, F> where
TryFlattenErr<MapErr<Fut1, F>, Fut2>: Future,
impl<Fut> Future for CatchUnwind<Fut> where
Fut: Future + UnwindSafe,
impl<Fut> Future for CatchUnwind<Fut> where
Fut: Future + UnwindSafe,
impl<St> Future for TryConcat<St> where
St: TryStream,
<St as TryStream>::Ok: Extend<<<St as TryStream>::Ok as IntoIterator>::Item>,
<St as TryStream>::Ok: IntoIterator,
<St as TryStream>::Ok: Default,
impl<St> Future for TryConcat<St> where
St: TryStream,
<St as TryStream>::Ok: Extend<<<St as TryStream>::Ok as IntoIterator>::Item>,
<St as TryStream>::Ok: IntoIterator,
<St as TryStream>::Ok: Default,
impl<Fut1, Fut2, Fut3, Fut4> Future for TryJoin4<Fut1, Fut2, Fut3, Fut4> where
Fut1: TryFuture,
Fut2: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut3: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut4: TryFuture<Error = <Fut1 as TryFuture>::Error>,
impl<Fut1, Fut2, Fut3, Fut4> Future for TryJoin4<Fut1, Fut2, Fut3, Fut4> where
Fut1: TryFuture,
Fut2: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut3: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut4: TryFuture<Error = <Fut1 as TryFuture>::Error>,
impl<St, Fut, F> Future for TryForEachConcurrent<St, Fut, F> where
F: FnMut(<St as TryStream>::Ok) -> Fut,
Fut: Future<Output = Result<(), <St as TryStream>::Error>>,
St: TryStream,
impl<St, Fut, F> Future for TryForEachConcurrent<St, Fut, F> where
F: FnMut(<St as TryStream>::Ok) -> Fut,
Fut: Future<Output = Result<(), <St as TryStream>::Error>>,
St: TryStream,
impl<St> Future for Concat<St> where
St: Stream,
<St as Stream>::Item: Extend<<<St as Stream>::Item as IntoIterator>::Item>,
<St as Stream>::Item: IntoIterator,
<St as Stream>::Item: Default,
impl<St> Future for Concat<St> where
St: Stream,
<St as Stream>::Item: Extend<<<St as Stream>::Item as IntoIterator>::Item>,
<St as Stream>::Item: IntoIterator,
<St as Stream>::Item: Default,
impl<Fut1, Fut2> Future for TryJoin<Fut1, Fut2> where
Fut1: TryFuture,
Fut2: TryFuture<Error = <Fut1 as TryFuture>::Error>,
impl<Fut1, Fut2> Future for TryJoin<Fut1, Fut2> where
Fut1: TryFuture,
Fut2: TryFuture<Error = <Fut1 as TryFuture>::Error>,
impl<Fut, F, G> Future for MapOkOrElse<Fut, F, G> where
Map<IntoFuture<Fut>, ChainFn<MapOkFn<F>, ChainFn<MapErrFn<G>, MergeResultFn>>>: Future,
impl<Fut, F, G> Future for MapOkOrElse<Fut, F, G> where
Map<IntoFuture<Fut>, ChainFn<MapOkFn<F>, ChainFn<MapErrFn<G>, MergeResultFn>>>: Future,
impl<Fut> Future for NeverError<Fut> where
Map<Fut, OkFn<Infallible>>: Future,
impl<Fut> Future for NeverError<Fut> where
Map<Fut, OkFn<Infallible>>: Future,
impl<Fut1, Fut2, Fut3, Fut4> Future for Join4<Fut1, Fut2, Fut3, Fut4> where
Fut1: Future,
Fut2: Future,
Fut3: Future,
Fut4: Future,
impl<Fut1, Fut2, Fut3, Fut4> Future for Join4<Fut1, Fut2, Fut3, Fut4> where
Fut1: Future,
Fut2: Future,
Fut3: Future,
Fut4: Future,
impl<St, Fut, F> Future for ForEach<St, Fut, F> where
F: FnMut(<St as Stream>::Item) -> Fut,
Fut: Future<Output = ()>,
St: Stream,
impl<St, Fut, F> Future for ForEach<St, Fut, F> where
F: FnMut(<St as Stream>::Item) -> Fut,
Fut: Future<Output = ()>,
St: Stream,
impl<Fut> Future for IntoFuture<Fut> where
Fut: TryFuture,
impl<Fut> Future for IntoFuture<Fut> where
Fut: TryFuture,
impl<Fut1, Fut2, Fut3> Future for TryJoin3<Fut1, Fut2, Fut3> where
Fut1: TryFuture,
Fut2: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut3: TryFuture<Error = <Fut1 as TryFuture>::Error>,
impl<Fut1, Fut2, Fut3> Future for TryJoin3<Fut1, Fut2, Fut3> where
Fut1: TryFuture,
Fut2: TryFuture<Error = <Fut1 as TryFuture>::Error>,
Fut3: TryFuture<Error = <Fut1 as TryFuture>::Error>,
impl<'_, Si, St, Ok, Error> Future for SendAll<'_, Si, St> where
St: Stream<Item = Result<Ok, Error>> + Unpin + ?Sized,
Si: Sink<Ok, Error = Error> + Unpin + ?Sized,
impl<'_, Si, St, Ok, Error> Future for SendAll<'_, Si, St> where
St: Stream<Item = Result<Ok, Error>> + Unpin + ?Sized,
Si: Sink<Ok, Error = Error> + Unpin + ?Sized,
impl<T> Future for Ready<T>
impl<T> Future for Ready<T>
impl<'_, T> Future for FutureObj<'_, T>
impl<'_, T> Future for FutureObj<'_, T>
impl<'_, T> Future for LocalFutureObj<'_, T>
impl<'_, T> Future for LocalFutureObj<'_, T>
impl<T> Future for Receiver<T>
impl<T> Future for Receiver<T>
impl<'_, T> Future for Cancellation<'_, T>
impl<'_, T> Future for Cancellation<'_, T>
impl<T> Future for Instrumented<T> where
T: Future,
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impl<T> Future for Instrumented<T> where
T: Future,
[src]impl<T> Future for JoinHandle<T>
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impl<T> Future for JoinHandle<T>
[src]impl<T, B> Future for Handshake<T, B> where
T: AsyncRead + AsyncWrite + Unpin,
B: Buf + 'static,
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impl<T, B> Future for Handshake<T, B> where
T: AsyncRead + AsyncWrite + Unpin,
B: Buf + 'static,
[src]impl<T, B> Future for Connection<T, B> where
T: AsyncRead + AsyncWrite + Unpin,
B: Buf + 'static,
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impl<T, B> Future for Connection<T, B> where
T: AsyncRead + AsyncWrite + Unpin,
B: Buf + 'static,
[src]impl<B> Future for ReadySendRequest<B> where
B: Buf + 'static,
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impl<B> Future for ReadySendRequest<B> where
B: Buf + 'static,
[src]type Output = Result<SendRequest<B>, Error>
pub fn poll(
self: Pin<&mut ReadySendRequest<B>>,
cx: &mut Context<'_>
) -> Poll<<ReadySendRequest<B> as Future>::Output>
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self: Pin<&mut ReadySendRequest<B>>,
cx: &mut Context<'_>
) -> Poll<<ReadySendRequest<B> as Future>::Output>
impl Future for ResponseFuture
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impl Future for ResponseFuture
[src]type Output = Result<Response<RecvStream>, Error>
pub fn poll(
self: Pin<&mut ResponseFuture>,
cx: &mut Context<'_>
) -> Poll<<ResponseFuture as Future>::Output>
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self: Pin<&mut ResponseFuture>,
cx: &mut Context<'_>
) -> Poll<<ResponseFuture as Future>::Output>
impl Future for PushedResponseFuture
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impl Future for PushedResponseFuture
[src]type Output = Result<Response<RecvStream>, Error>
pub fn poll(
self: Pin<&mut PushedResponseFuture>,
cx: &mut Context<'_>
) -> Poll<<PushedResponseFuture as Future>::Output>
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self: Pin<&mut PushedResponseFuture>,
cx: &mut Context<'_>
) -> Poll<<PushedResponseFuture as Future>::Output>
impl<'a> Future for WaitForCancellationFuture<'a>
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impl<'a> Future for WaitForCancellationFuture<'a>
[src]impl<T> Future for ReusableBoxFuture<T>
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impl<T> Future for ReusableBoxFuture<T>
[src]impl<T> Future for Instrumented<T> where
T: Future,
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impl<T> Future for Instrumented<T> where
T: Future,
[src]Implementors
impl Future for choices::warp::hyper::client::conn::ResponseFuture
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impl Future for choices::warp::hyper::client::conn::ResponseFuture
[src]impl Future for choices::warp::hyper::client::ResponseFuture
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impl Future for choices::warp::hyper::client::ResponseFuture
[src]impl<I, B, S, E> Future for choices::warp::hyper::server::conn::Connection<I, S, E> where
E: ConnStreamExec<<S as HttpService<Body>>::Future, B>,
I: AsyncRead + AsyncWrite + Unpin + 'static,
S: HttpService<Body, ResBody = B>,
B: Body + 'static,
<S as HttpService<Body>>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
<B as Body>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
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impl<I, B, S, E> Future for choices::warp::hyper::server::conn::Connection<I, S, E> where
E: ConnStreamExec<<S as HttpService<Body>>::Future, B>,
I: AsyncRead + AsyncWrite + Unpin + 'static,
S: HttpService<Body, ResBody = B>,
B: Body + 'static,
<S as HttpService<Body>>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
<B as Body>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
[src]impl<I, F, S, FE, E, B> Future for Connecting<I, F, E> where
E: ConnStreamExec<<S as HttpService<Body>>::Future, B>,
I: AsyncRead + AsyncWrite + Unpin,
S: HttpService<Body, ResBody = B>,
B: Body + 'static,
F: Future<Output = Result<S, FE>>,
<B as Body>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
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impl<I, F, S, FE, E, B> Future for Connecting<I, F, E> where
E: ConnStreamExec<<S as HttpService<Body>>::Future, B>,
I: AsyncRead + AsyncWrite + Unpin,
S: HttpService<Body, ResBody = B>,
B: Body + 'static,
F: Future<Output = Result<S, FE>>,
<B as Body>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
[src]type Output = Result<Connection<I, S, E>, FE>
pub fn poll(
self: Pin<&mut Connecting<I, F, E>>,
cx: &mut Context<'_>
) -> Poll<<Connecting<I, F, E> as Future>::Output>
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self: Pin<&mut Connecting<I, F, E>>,
cx: &mut Context<'_>
) -> Poll<<Connecting<I, F, E> as Future>::Output>
impl<I, IO, IE, S, B, E> Future for Server<I, S, E> where
E: ConnStreamExec<<<S as MakeServiceRef<IO, Body>>::Service as HttpService<Body>>::Future, B> + NewSvcExec<IO, <S as MakeServiceRef<IO, Body>>::Future, <S as MakeServiceRef<IO, Body>>::Service, E, NoopWatcher>,
I: Accept<Conn = IO, Error = IE>,
S: MakeServiceRef<IO, Body, ResBody = B>,
B: Body + 'static,
IO: AsyncRead + AsyncWrite + Unpin + Send + 'static,
IE: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
<S as MakeServiceRef<IO, Body>>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
<B as Body>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
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impl<I, IO, IE, S, B, E> Future for Server<I, S, E> where
E: ConnStreamExec<<<S as MakeServiceRef<IO, Body>>::Service as HttpService<Body>>::Future, B> + NewSvcExec<IO, <S as MakeServiceRef<IO, Body>>::Future, <S as MakeServiceRef<IO, Body>>::Service, E, NoopWatcher>,
I: Accept<Conn = IO, Error = IE>,
S: MakeServiceRef<IO, Body, ResBody = B>,
B: Body + 'static,
IO: AsyncRead + AsyncWrite + Unpin + Send + 'static,
IE: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
<S as MakeServiceRef<IO, Body>>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
<B as Body>::Error: Into<Box<dyn Error + 'static + Sync + Send, Global>>,
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