Struct futures_util::stream::Peekable

#[must_use = "streams do nothing unless polled"]
pub struct Peekable<St: Stream> { /* fields omitted */ }

A Stream that implements a peek method.

The peek method can be used to retrieve a reference to the next Stream::Item if available. A subsequent call to poll will return the owned item.

Methods

impl<St: Stream> Peekable<St>

pub fn get_ref(&self) -> &St

Acquires a reference to the underlying stream that this combinator is pulling from.

pub fn get_mut(&mut self) -> &mut St

Acquires a mutable reference to the underlying stream that this combinator is pulling from.

Note that care must be taken to avoid tampering with the state of the stream which may otherwise confuse this combinator.

Important traits for Pin<P>

impl<P> Future for Pin<P> where
    P: Unpin + DerefMut,
    <P as Deref>::Target: Future,  type Output = <<P as Deref>::Target as Future>::Output;

pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut St>

Acquires a pinned mutable reference to the underlying stream that this combinator is pulling from.

Note that care must be taken to avoid tampering with the state of the stream which may otherwise confuse this combinator.

pub fn into_inner(self) -> St

Consumes this combinator, returning the underlying stream.

Note that this may discard intermediate state of this combinator, so care should be taken to avoid losing resources when this is called.

pub fn poll_peek(
    self: Pin<&mut Self>,
    cx: &mut Context
) -> Poll<Option<&St::Item>>

Peek retrieves a reference to the next item in the stream.

This method polls the underlying stream and return either a reference to the next item if the stream is ready or passes through any errors.

Trait Implementations

impl<St: Debug + Stream> Debug for Peekable<St> where
    St::Item: Debug, 

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

Formats the value using the given formatter.

impl<St: Stream + Unpin> Unpin for Peekable<St>

impl<S: Stream> Stream for Peekable<S>

type Item = S::Item

Values yielded by the stream.

fn poll_next(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>>

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.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.

impl<St: Stream> FusedStream for Peekable<St>

fn is_terminated(&self) -> bool

Returns true if the stream should no longer be polled.

impl<S, Item> Sink<Item> for Peekable<S> where
    S: Sink<Item> + Stream, 

type Error = S::Error

The type of value produced by the sink when an error occurs.

fn poll_ready(
    self: Pin<&mut Self>,
    cx: &mut Context
) -> Poll<Result<(), Self::Error>>

Attempts to prepare the Sink to receive a value.

fn start_send(self: Pin<&mut Self>, item: Item) -> Result<(), Self::Error>

Begin the process of sending a value to the sink. Each call to this function must be preceded by a successful call to poll_ready which returned Poll::Ready(Ok(())).

fn poll_flush(
    self: Pin<&mut Self>,
    cx: &mut Context
) -> Poll<Result<(), Self::Error>>

Flush any remaining output from this sink.

fn poll_close(
    self: Pin<&mut Self>,
    cx: &mut Context
) -> Poll<Result<(), Self::Error>>

Flush any remaining output and close this sink, if necessary.