Struct completion::stream::Peekable

pub struct Peekable<S: CompletionStream> { /* fields omitted */ }

Stream for CompletionStreamExt::peekable.

Implementations

impl<S: CompletionStream> Peekable<S>

#[must_use]pub fn peek(self: Pin<&mut Self>) -> Peek<'_, S>

Peek the next value in the stream.

Cancellation

If the returned future is cancelled and the next value in the stream has not been peeked yet, the entire stream is cancelled, otherwise nothing happens.

Examples

use completion::{CompletionStreamExt, StreamExt};
use futures_lite::{stream, pin};

let stream = stream::once(5).into_completion().peekable();
pin!(stream);

assert_eq!(stream.as_mut().peek().await, Some(&5));
assert_eq!(stream.as_mut().peek().await, Some(&5));
assert_eq!(stream.next().await, Some(5));
assert_eq!(stream.as_mut().peek().await, None);
assert_eq!(stream.next().await, None);

#[must_use]pub fn peek_unpin(&mut self) -> Peek<'_, S> where
    Self: Unpin, 

Peek the next value in the stream if the underlying type implements Unpin.

stream.peek_unpin() is equivalent to Pin::new(&mut stream).peek(). See peek for more information.

Examples

use completion::{CompletionStreamExt, StreamExt};
use futures_lite::stream;

let mut stream = stream::once(8).into_completion().peekable();

assert_eq!(stream.peek_unpin().await, Some(&8));
assert_eq!(stream.peek_unpin().await, Some(&8));
assert_eq!(stream.next().await, Some(8));
assert_eq!(stream.peek_unpin().await, None);
assert_eq!(stream.next().await, None);

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

Attempt to peek the next value in the stream.

This function is quite low level, use peek or peek_unpin for a higher-level equivalent.

Safety

See CompletionStream::poll_next.

pub unsafe fn poll_peek_cancel(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>
) -> Poll<()>

Attempt to cancel peeking the next value in the stream.

This will cancel the underlying stream if the next value in the stream has not already been peeked.

This function is quite low level, use peek or peek_unpin for a higher-level equivalent.

Safety

See CompletionStream::poll_cancel.

Trait Implementations

impl<S: Clone + CompletionStream> Clone for Peekable<S> where
    S::Item: Clone, 

fn clone(&self) -> Peekable<S>

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<S: CompletionStream> CompletionStream for Peekable<S>

type Item = S::Item

Values yielded by the stream.

unsafe 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.

unsafe fn poll_cancel(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()>

Attempt to cancel the stream, registering the current task for wakeup if it has not finished cancelling yet.

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

Returns the bounds on the remaining length of the stream.

impl<S: Debug + CompletionStream> Debug for Peekable<S> where
    S::Item: Debug, 

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

Formats the value using the given formatter.

impl<S> Stream for Peekable<S> where
    S: CompletionStream + Stream<Item = <S as CompletionStream>::Item>, 

type Item = <S as CompletionStream>::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<'__pin, S: CompletionStream> Unpin for Peekable<S> where
    __Origin<'__pin, S>: Unpin,