Struct futures::stream::FuturesUnordered

#[must_use = "streams do nothing unless polled"]
pub struct FuturesUnordered<F> { /* fields omitted */ }

An unbounded queue of futures.

This "combinator" also serves a special function in this library, providing the ability to maintain a queue of futures that and manage driving them all to completion.

Futures are pushed into this queue and their realized values are yielded as they are ready. This structure is optimized to manage a large number of futures. Futures managed by FuturesUnordered will only be polled when they generate notifications. This reduces the required amount of work needed to coordinate large numbers of futures.

When a FuturesUnordered is first created, it does not contain any futures. Calling poll in this state will result in Ok(Async::Ready(None)) to be returned. Futures are submitted to the queue using push; however, the future will not be polled at this point. FuturesUnordered will only poll managged futures when FuturesUnordered::poll is called. As such, it is important to call poll after pushing new futures.

If FuturesUnordered::poll returns Ok(Async::Ready(None)) this means that the queue is currently not managing any futures. A future may be submitted to the queue at a later time. At that point, a call to FuturesUnordered::poll will either return the future's resolved value or Ok(Async::NotReady) if the future has not yet completed.

Note that you can create a ready-made FuturesUnordered via the futures_unordered function in the stream module, or you can start with a blank queue with the FuturesUnordered::new constructor.

Methods

impl<T> FuturesUnordered<T> where T: Future

fn new() -> FuturesUnordered<T>

Constructs a new, empty FuturesUnordered

The returned FuturesUnordered does not contain any futures and, in this state, FuturesUnordered::poll will return Ok(Async::Ready(None)).

impl<T> FuturesUnordered<T>

fn len(&self) -> usize

Returns the number of futures contained by the queue.

This represents the total number of in-flight futures.

fn is_empty(&self) -> bool

Returns true if the queue contains no futures

fn push(&mut self, future: T)

Push a future into the queue.

This function submits the given future to the queue for managing. This function will not call poll on the submitted future. The caller must ensure that FuturesUnordered::poll is called in order to receive task notifications.

Trait Implementations

impl<T: Send> Send for FuturesUnordered<T>

impl<T: Sync> Sync for FuturesUnordered<T>

impl<T> Stream for FuturesUnordered<T> where T: Future

type Item = T::Item

The type of item this stream will yield on success.

type Error = T::Error

The type of error this stream may generate.

fn poll(&mut self) -> Poll<Option<T::Item>, T::Error>

Attempt to pull out the next value of this stream, returning None if the stream is finished.

fn wait(self) -> Wait<Self> where Self: Sized

Creates an iterator which blocks the current thread until each item of this stream is resolved.

fn boxed(self) -> BoxStream<Self::Item, Self::Error> where Self: Sized + Send + 'static

Convenience function for turning this stream into a trait object.

fn into_future(self) -> StreamFuture<Self> where Self: Sized

Converts this stream into a Future.

fn map<U, F>(self, f: F) -> Map<Self, F> where F: FnMut(Self::Item) -> U, Self: Sized

Converts a stream of type T to a stream of type U.

fn map_err<U, F>(self, f: F) -> MapErr<Self, F> where F: FnMut(Self::Error) -> U, Self: Sized

Converts a stream of error type T to a stream of error type U.

fn filter<F>(self, f: F) -> Filter<Self, F> where F: FnMut(&Self::Item) -> bool, Self: Sized

Filters the values produced by this stream according to the provided predicate.

fn filter_map<F, B>(self, f: F) -> FilterMap<Self, F> where F: FnMut(Self::Item) -> Option<B>, Self: Sized

Filters the values produced by this stream while simultaneously mapping them to a different type.

fn then<F, U>(self, f: F) -> Then<Self, F, U> where F: FnMut(Result<Self::Item, Self::Error>) -> U,
        U: IntoFuture,
        Self: Sized

Chain on a computation for when a value is ready, passing the resulting item to the provided closure f.

fn and_then<F, U>(self, f: F) -> AndThen<Self, F, U> where F: FnMut(Self::Item) -> U,
        U: IntoFuture<Error=Self::Error>,
        Self: Sized

Chain on a computation for when a value is ready, passing the successful results to the provided closure f.

fn or_else<F, U>(self, f: F) -> OrElse<Self, F, U> where F: FnMut(Self::Error) -> U, U: IntoFuture<Item=Self::Item>, Self: Sized

Chain on a computation for when an error happens, passing the erroneous result to the provided closure f.

fn collect(self) -> Collect<Self> where Self: Sized

Collect all of the values of this stream into a vector, returning a future representing the result of that computation.

fn concat2(self) -> Concat2<Self> where Self: Sized,
        Self::Item: Extend<Self::Item::Item> + IntoIterator + Default

Concatenate all results of a stream into a single extendable destination, returning a future representing the end result.

fn concat(self) -> Concat<Self> where Self: Sized, Self::Item: Extend<Self::Item::Item> + IntoIterator

Deprecated since 0.1.14

: please use Stream::concat2 instead

Concatenate all results of a stream into a single extendable destination, returning a future representing the end result.

fn fold<F, T, Fut>(self, init: T, f: F) -> Fold<Self, F, Fut, T> where F: FnMut(T, Self::Item) -> Fut,
        Fut: IntoFuture<Item=T>,
        Self::Error: From<Fut::Error>,
        Self: Sized

Execute an accumulating computation over a stream, collecting all the values into one final result.

fn flatten(self) -> Flatten<Self> where Self::Item: Stream, Self::Item::Error: From<Self::Error>, Self: Sized

Flattens a stream of streams into just one continuous stream.

fn skip_while<P, R>(self, pred: P) -> SkipWhile<Self, P, R> where P: FnMut(&Self::Item) -> R,
        R: IntoFuture<Item=bool, Error=Self::Error>,
        Self: Sized

Skip elements on this stream while the predicate provided resolves to true.

fn take_while<P, R>(self, pred: P) -> TakeWhile<Self, P, R> where P: FnMut(&Self::Item) -> R,
        R: IntoFuture<Item=bool, Error=Self::Error>,
        Self: Sized

Take elements from this stream while the predicate provided resolves to true.

fn for_each<F, U>(self, f: F) -> ForEach<Self, F, U> where F: FnMut(Self::Item) -> U,
        U: IntoFuture<Item=(), Error=Self::Error>,
        Self: Sized

Runs this stream to completion, executing the provided closure for each element on the stream.

fn from_err<E: From<Self::Error>>(self) -> FromErr<Self, E> where Self: Sized

Map this stream's error to any error implementing From for this stream's Error, returning a new stream.

fn take(self, amt: u64) -> Take<Self> where Self: Sized

Creates a new stream of at most amt items of the underlying stream.

fn skip(self, amt: u64) -> Skip<Self> where Self: Sized

Creates a new stream which skips amt items of the underlying stream.

fn fuse(self) -> Fuse<Self> where Self: Sized

Fuse a stream such that poll will never again be called once it has finished.

fn by_ref(&mut self) -> &mut Self where Self: Sized

Borrows a stream, rather than consuming it.

fn catch_unwind(self) -> CatchUnwind<Self> where Self: Sized + UnwindSafe

Catches unwinding panics while polling the stream.

fn buffered(self, amt: usize) -> Buffered<Self> where Self::Item: IntoFuture<Error=Self::Error>, Self: Sized

An adaptor for creating a buffered list of pending futures.

fn buffer_unordered(self, amt: usize) -> BufferUnordered<Self> where Self::Item: IntoFuture<Error=Self::Error>, Self: Sized

An adaptor for creating a buffered list of pending futures (unordered).

fn merge<S>(self, other: S) -> Merge<Self, S> where S: Stream<Error=Self::Error>, Self: Sized

An adapter for merging the output of two streams.

fn zip<S>(self, other: S) -> Zip<Self, S> where S: Stream<Error=Self::Error>, Self: Sized

An adapter for zipping two streams together.

fn chain<S>(self, other: S) -> Chain<Self, S> where S: Stream<Item=Self::Item, Error=Self::Error>, Self: Sized

Adapter for chaining two stream.

fn peekable(self) -> Peekable<Self> where Self: Sized

Creates a new stream which exposes a peek method.

fn chunks(self, capacity: usize) -> Chunks<Self> where Self: Sized

An adaptor for chunking up items of the stream inside a vector.

fn select<S>(self, other: S) -> Select<Self, S> where S: Stream<Item=Self::Item, Error=Self::Error>, Self: Sized

Creates a stream that selects the next element from either this stream or the provided one, whichever is ready first.

fn forward<S>(self, sink: S) -> Forward<Self, S> where S: Sink<SinkItem=Self::Item>,
        Self::Error: From<S::SinkError>,
        Self: Sized

A future that completes after the given stream has been fully processed into the sink, including flushing.

fn split(self) -> (SplitSink<Self>, SplitStream<Self>) where Self: Sink + Sized

Splits this Stream + Sink object into separate Stream and Sink objects.

impl<T: Debug> Debug for FuturesUnordered<T>

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

Formats the value using the given formatter.

impl<T> Drop for FuturesUnordered<T>

fn drop(&mut self)

A method called when the value goes out of scope.