Trait tokio::stream::Stream[−][src]

#[must_use = "streams do nothing unless polled"]
pub trait Stream {
    type Item;
    pub fn poll_next(
        self: Pin<&mut Self>, 
        cx: &mut Context<'_>
    ) -> Poll<Option<Self::Item>>;

    pub fn size_hint(&self) -> (usize, Option<usize>) { ... }
}
[−]

A stream of values produced asynchronously.

If Future<Output = T> is an asynchronous version of T, then Stream<Item = T> is an asynchronous version of Iterator<Item = T>. A stream represents a sequence of value-producing events that occur asynchronously to the caller.

The trait is modeled after Future, but allows poll_next to be called even after a value has been produced, yielding None once the stream has been fully exhausted.

Associated Types

type Item[src][−]

Values yielded by the stream.

Required methods

pub fn poll_next(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>
) -> Poll<Option<Self::Item>>[src][−]

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

Return value

There are several possible return values, each indicating a distinct stream state:

  • Poll::Pending means that this stream’s next value is not ready yet. Implementations will ensure that the current task will be notified when the next value may be ready.

  • Poll::Ready(Some(val)) means that the stream has successfully produced a value, val, and may produce further values on subsequent poll_next calls.

  • Poll::Ready(None) means that the stream has terminated, and poll_next should not be invoked again.

Panics

Once a stream has finished (returned Ready(None) from poll_next), calling its poll_next method again may panic, block forever, or cause other kinds of problems; the Stream trait places no requirements on the effects of such a call. However, as the poll_next 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 stream’s state.

If this is difficult to guard against then the fuse adapter can be used to ensure that poll_next always returns Ready(None) in subsequent calls.

Provided methods

pub fn size_hint(&self) -> (usize, Option<usize>)[src][−]

Returns the bounds on the remaining length of the stream.

Specifically, size_hint() returns a tuple where the first element is the lower bound, and the second element is the upper bound.

The second half of the tuple that is returned is an Option<usize>. A None here means that either there is no known upper bound, or the upper bound is larger than usize.

Implementation notes

It is not enforced that a stream implementation yields the declared number of elements. A buggy stream may yield less than the lower bound or more than the upper bound of elements.

size_hint() is primarily intended to be used for optimizations such as reserving space for the elements of the stream, but must not be trusted to e.g., omit bounds checks in unsafe code. An incorrect implementation of size_hint() should not lead to memory safety violations.

That said, the implementation should provide a correct estimation, because otherwise it would be a violation of the trait’s protocol.

The default implementation returns (0, None) which is correct for any stream.

Implementations on Foreign Types

impl<S> Stream for Box<S, Global> where
    S: Stream + Unpin + ?Sized, [src]

type Item = <S as Stream>::Item

impl<P> Stream for Pin<P> where
    P: DerefMut + Unpin,
    <P as Deref>::Target: Stream, [src]

type Item = <<P as Deref>::Target as Stream>::Item

impl<'_, S> Stream for &'_ mut S where
    S: Stream + Unpin + ?Sized, [src]

type Item = <S as Stream>::Item

impl<S> Stream for AssertUnwindSafe<S> where
    S: Stream, [src]

type Item = <S as Stream>::Item

Implementors

impl Stream for TcpListener[src]

type Item = Result<TcpStream>

impl Stream for Incoming<'_>[src]

type Item = Result<TcpStream>

impl Stream for Signal[src]

type Item = ()

impl Stream for Interval[src]

type Item = Instant

impl<I> Stream for Iter<I> where
    I: Iterator, [src]

type Item = I::Item

impl<K, V> Stream for StreamMap<K, V> where
    K: Clone + Unpin,
    V: Stream + Unpin, [src]

type Item = (K, V::Item)

impl<R> Stream for ReaderStream<R> where
    R: AsyncRead, [src]

type Item = Result<Bytes>

impl<R: AsyncBufRead> Stream for Lines<R>[src]

type Item = Result<String>

impl<R: AsyncBufRead> Stream for Split<R>[src]

type Item = Result<Vec<u8>>

impl<T> Stream for tokio::sync::mpsc::Receiver<T>[src]

type Item = T

impl<T> Stream for UnboundedReceiver<T>[src]

type Item = T

impl<T> Stream for DelayQueue<T>[src]

type Item = Result<Expired<T>, Error>

impl<T> Stream for Empty<T>[src]

type Item = T

impl<T> Stream for Once<T>[src]

type Item = T

impl<T> Stream for Pending<T>[src]

type Item = T

impl<T: Clone> Stream for tokio::sync::watch::Receiver<T>[src]

type Item = T

impl<T: Stream> Stream for Throttle<T>[src]

type Item = T::Item

impl<T> Stream for Receiver<T>

impl Stream for Timer

impl<T, U> Stream for Framed<T, U> where
    T: AsyncRead + Unpin,
    U: Decoder, 

impl<T, D> Stream for FramedRead<T, D> where
    T: AsyncRead + Unpin,
    D: Decoder, 

impl<T: Iterator + Send + 'static> Stream for Unblock<T> where
    T::Item: Send + 'static, 

impl<T> Stream for Receiver<T>

impl<T> Stream for UnboundedReceiver<T>

impl<T> Stream for Empty<T>

impl<I: Iterator> Stream for Iter<I>

impl<T> Stream for Once<T>

impl<T> Stream for Pending<T>

impl<T, F> Stream for PollFn<F> where
    F: FnMut(&mut Context<'_>) -> Poll<Option<T>>, 

impl<T: Clone> Stream for Repeat<T>

impl<T, F> Stream for RepeatWith<F> where
    F: FnMut() -> T, 

impl<T, F, Fut, Item> Stream for Unfold<T, F, Fut> where
    F: FnMut(T) -> Fut,
    Fut: Future<Output = Option<(Item, T)>>, 

impl<T, E, F, Fut, Item> Stream for TryUnfold<T, F, Fut> where
    F: FnMut(T) -> Fut,
    Fut: Future<Output = Result<Option<(Item, T)>, E>>, 

impl<S, St, F, B> Stream for Scan<S, St, F> where
    S: Stream,
    F: FnMut(&mut St, S::Item) -> Option<B>, 

impl<S: Stream> Stream for Fuse<S>

impl<S, F, T> Stream for Map<S, F> where
    S: Stream,
    F: FnMut(S::Item) -> T, 

impl<S, U, F> Stream for FlatMap<S, U, F> where
    S: Stream,
    U: Stream,
    F: FnMut(S::Item) -> U, 

impl<S, U> Stream for Flatten<S> where
    S: Stream<Item = U>,
    U: Stream, 

impl<S, F, Fut> Stream for Then<S, F, Fut> where
    S: Stream,
    F: FnMut(S::Item) -> Fut,
    Fut: Future, 

impl<S, P> Stream for Filter<S, P> where
    S: Stream,
    P: FnMut(&S::Item) -> bool, 

impl<T, S1, S2> Stream for Or<S1, S2> where
    S1: Stream<Item = T>,
    S2: Stream<Item = T>, 

impl<T, S1, S2> Stream for Race<S1, S2> where
    S1: Stream<Item = T>,
    S2: Stream<Item = T>, 

impl<S, F, T> Stream for FilterMap<S, F> where
    S: Stream,
    F: FnMut(S::Item) -> Option<T>, 

impl<S: Stream> Stream for Take<S>

impl<S, P> Stream for TakeWhile<S, P> where
    S: Stream,
    P: FnMut(&S::Item) -> bool, 

impl<S: Stream> Stream for Skip<S>

impl<S, P> Stream for SkipWhile<S, P> where
    S: Stream,
    P: FnMut(&S::Item) -> bool, 

impl<S: Stream> Stream for StepBy<S>

impl<S: Stream, U: Stream<Item = S::Item>> Stream for Chain<S, U>

impl<'a, S, T: 'a> Stream for Cloned<S> where
    S: Stream<Item = &'a T>,
    T: Clone, 

impl<'a, S, T: 'a> Stream for Copied<S> where
    S: Stream<Item = &'a T>,
    T: Copy, 

impl<S> Stream for Cycle<S> where
    S: Stream + Clone, 

impl<S> Stream for Enumerate<S> where
    S: Stream, 

impl<S, F> Stream for Inspect<S, F> where
    S: Stream,
    F: FnMut(&S::Item), 

impl<A: Stream, B: Stream> Stream for Zip<A, B>

impl<R: AsyncBufRead> Stream for Lines<R>

impl<R: AsyncBufRead> Stream for Split<R>

impl<R: AsyncRead + Unpin> Stream for Bytes<R>

impl Stream for Body

impl Stream for ManualSignalInterval

impl<TInner, TConn, TErr> Stream for BandwidthListener<TInner> where
    TInner: TryStream<Ok = ListenerEvent<TConn, TErr>, Error = TErr>, 

impl<TTrans> Stream for ListenersStream<TTrans> where
    TTrans: Transport, 

impl<A, B, I> Stream for EitherOutput<A, B> where
    A: TryStream<Ok = I>,
    B: TryStream<Ok = I>, 

impl<AStream, BStream, AInner, BInner, AError, BError> Stream for EitherListenStream<AStream, BStream> where
    AStream: TryStream<Ok = ListenerEvent<AInner, AError>, Error = AError>,
    BStream: TryStream<Ok = ListenerEvent<BInner, BError>, Error = BError>, 

impl<TListener, TMap, TTransOut, TMapOut, TListUpgr, TTransErr> Stream for AndThenStream<TListener, TMap> where
    TListener: TryStream<Ok = ListenerEvent<TListUpgr, TTransErr>, Error = TTransErr>,
    TListUpgr: TryFuture<Ok = TTransOut, Error = TTransErr>,
    TMap: FnOnce(TTransOut, ConnectedPoint) -> TMapOut + Clone,
    TMapOut: TryFuture, 

impl<T, F, A, B, X, E> Stream for MapStream<T, F> where
    T: TryStream<Ok = ListenerEvent<X, E>, Error = E>,
    X: TryFuture<Ok = A>,
    F: FnOnce(A, ConnectedPoint) -> B + Clone, 

impl<T, F, TErr> Stream for MapErrListener<T, F> where
    T: Transport,
    F: FnOnce(T::Error) -> TErr + Clone,
    TErr: Error, 

impl Stream for Listener

impl<T> Stream for Chan<T>

impl<InnerStream, O, E> Stream for TimeoutListener<InnerStream> where
    InnerStream: TryStream<Ok = ListenerEvent<O, E>, Error = E>, 

impl<S, U, F, C, D, E> Stream for ListenerStream<S, U> where
    S: TryStream<Ok = ListenerEvent<F, E>, Error = E>,
    F: TryFuture<Ok = (PeerId, C)>,
    C: AsyncRead + AsyncWrite + Unpin,
    U: InboundUpgrade<Negotiated<C>, Output = D> + Clone, 

impl<TBehaviour, TInEvent, TOutEvent, THandler> Stream for ExpandedSwarm<TBehaviour, TInEvent, TOutEvent, THandler> where
    TBehaviour: NetworkBehaviour<ProtocolsHandler = THandler>,
    THandler: IntoProtocolsHandler + Send + 'static,
    TInEvent: Send + 'static,
    TOutEvent: Send + 'static,
    THandler::Handler: ProtocolsHandler<InEvent = TInEvent, OutEvent = TOutEvent>, 

impl<T> Stream for TcpListenStream<T> where
    T: Provider,
    T::Listener: Unpin,
    T::Stream: Unpin,
    T::IfWatcher: Unpin, 

impl Stream for Listen

impl<T> Stream for Connection<T> where
    T: AsyncRead + AsyncWrite + Send + Unpin + 'static, 

impl<T> Stream for BytesConnection<T> where
    T: AsyncRead + AsyncWrite + Send + Unpin + 'static, 

impl<T> Stream for Incoming<T>

impl<T> Stream for LocalIncoming<T>

impl<B: Block> Stream for LightClientRequestSender<B>

impl Stream for Peerset

impl<T> Stream for TracingUnboundedReceiver<T>

impl<T, U> Stream for Framed<T, U> where
    T: AsyncRead,
    U: Decoder, 

impl<T, D> Stream for FramedRead<T, D> where
    T: AsyncRead,
    D: Decoder, 

impl<T, D> Stream for FramedWrite<T, D> where
    T: Stream, 

impl<S> Stream for TimeoutStream<S> where
    S: TryStream,
    S::Error: From<Error>, 

impl Stream for Interval

impl Stream for Stream