[][src]Struct futures::stream::FuturesOrdered

#[must_use = "streams do nothing unless polled"]
pub struct FuturesOrdered<T> where
    T: Future
{ /* fields omitted */ }

An unbounded queue of futures.

This "combinator" is similar to FuturesUnordered, but it imposes an order on top of the set of futures. While futures in the set will race to completion in parallel, results will only be returned in the order their originating futures were added to the queue.

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

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

If FuturesOrdered::poll returns Poll::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 FuturesOrdered::poll will either return the future's resolved value or Poll::Pending if the future has not yet completed. When multiple futures are submitted to the queue, FuturesOrdered::poll will return Poll::Pending until the first future completes, even if some of the later futures have already completed.

Note that you can create a ready-made FuturesOrdered via the futures_ordered function in the stream module, or you can start with an empty queue with the FuturesOrdered::new constructor.

Methods

impl<Fut> FuturesOrdered<Fut> where
    Fut: Future
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Constructs a new, empty FuturesOrdered

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

Returns the number of futures contained in the queue.

This represents the total number of in-flight futures, both those currently processing and those that have completed but which are waiting for earlier futures to complete.

Returns true if the queue contains no futures

Push a future into the queue.

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

Trait Implementations

impl<T> Unpin for FuturesOrdered<T> where
    T: Future
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impl<Fut> FromIterator<Fut> for FuturesOrdered<Fut> where
    Fut: Future
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Creates a value from an iterator. Read more

impl<Fut> Default for FuturesOrdered<Fut> where
    Fut: Future
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Returns the "default value" for a type. Read more

impl<Fut> Stream for FuturesOrdered<Fut> where
    Fut: Future
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Values yielded by the stream.

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. Read more

impl<Fut> Debug for FuturesOrdered<Fut> where
    Fut: Future
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Formats the value using the given formatter. Read more

Auto Trait Implementations

impl<T> Send for FuturesOrdered<T> where
    T: Send,
    <T as Future>::Output: Send

impl<T> Sync for FuturesOrdered<T> where
    T: Sync,
    <T as Future>::Output: Sync

Blanket Implementations

impl<T> From for T
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Performs the conversion.

impl<T, U> TryFrom for T where
    T: From<U>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from)

Performs the conversion.

impl<T, U> TryInto for T where
    U: TryFrom<T>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from)

Performs the conversion.

impl<T, U> Into for T where
    U: From<T>, 
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Performs the conversion.

impl<T> Borrow for T where
    T: ?Sized
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Important traits for &'a mut I

Immutably borrows from an owned value. Read more

impl<T> BorrowMut for T where
    T: ?Sized
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Important traits for &'a mut I

Mutably borrows from an owned value. Read more

impl<T> Any for T where
    T: 'static + ?Sized
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🔬 This is a nightly-only experimental API. (get_type_id)

this method will likely be replaced by an associated static

Gets the TypeId of self. Read more

impl<T> StreamExt for T where
    T: Stream + ?Sized
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Creates a future that resolves to the next item in the stream. Read more

Converts this stream into a future of (next_item, tail_of_stream). If the stream terminates, then the next item is [None]. Read more

Maps this stream's items to a different type, returning a new stream of the resulting type. Read more

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

Filters the values produced by this stream while simultaneously mapping them to a different type according to the provided asynchronous closure. Read more

Computes from this stream's items new items of a different type using an asynchronous closure. Read more

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

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

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

Flattens a stream of streams into just one continuous stream. Read more

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

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

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

Runs this stream to completion, executing the provided asynchronous closure for each element on the stream concurrently as elements become available. Read more

Creates a new stream of at most n items of the underlying stream. Read more

Creates a new stream which skips n items of the underlying stream. Read more

Fuse a stream such that poll_next will never again be called once it has finished. Read more

Important traits for &'a mut I

Borrows a stream, rather than consuming it. Read more

Catches unwinding panics while polling the stream. Read more

Wrap the stream in a Box, pinning it.

An adaptor for creating a buffered list of pending futures. Read more

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

An adapter for zipping two streams together. Read more

Adapter for chaining two stream. Read more

Creates a new stream which exposes a peek method. Read more

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

This combinator will attempt to pull items from both streams. Each stream will be polled in a round-robin fashion, and whenever a stream is ready to yield an item that item is yielded. Read more

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

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

Do something with each item of this stream, afterwards passing it on. Read more

Important traits for Either<L, R>

Wrap this stream in an Either stream, making it the left-hand variant of that Either. Read more

Important traits for Either<L, R>

Wrap this stream in an Either stream, making it the right-hand variant of that Either. Read more

A convenience method for calling [Stream::poll_next] on [Unpin] stream types. Read more

impl<S, T, E> TryStream for S where
    S: Stream<Item = Result<T, E>>, 
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The type of successful values yielded by this future

The type of failures yielded by this future

Poll this TryStream as if it were a Stream. Read more

impl<S> TryStreamExt for S where
    S: TryStream
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Wraps the current stream in a new stream which converts the error type into the one provided. Read more

Wraps the current stream in a new stream which maps the success value using the provided closure. Read more

Wraps the current stream in a new stream which maps the error value using the provided closure. Read more

Wraps a [TryStream] into a type that implements Stream Read more

Creates a future that attempts to resolve the next item in the stream. If an error is encountered before the next item, the error is returned instead. Read more

Attempts to run this stream to completion, executing the provided asynchronous closure for each element on the stream. Read more

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

Attempts to run this stream to completion, executing the provided asynchronous closure for each element on the stream concurrently as elements become available, exiting as soon as an error occurs. Read more

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

Attempt to filter the values produced by this stream while simultaneously mapping them to a different type according to the provided asynchronous closure. Read more

Attempt to execute an accumulating asynchronous computation over a stream, collecting all the values into one final result. Read more

Attempt to execute several futures from a stream concurrently. Read more

Wraps a [TryStream] into a stream compatible with libraries using futures 0.1 Stream. Requires the compat feature to be enabled. ``` #![feature(async_await, await_macro, futures_api)] use futures::future::{FutureExt, TryFutureExt}; use futures::spawn; use futures::compat::TokioDefaultSpawner; # let (tx, rx) = futures::channel::oneshot::channel(); Read more