| //! Streams |
| //! |
| //! This module contains a number of functions for working with `Stream`s, |
| //! including the `StreamExt` trait which adds methods to `Stream` types. |
| |
| use core::marker::Unpin; |
| use core::pin::Pin; |
| use either::Either; |
| use futures_core::future::Future; |
| use futures_core::stream::{FusedStream, Stream}; |
| use futures_core::task::{LocalWaker, Poll}; |
| use futures_sink::Sink; |
| |
| mod iter; |
| pub use self::iter::{iter, Iter}; |
| |
| mod repeat; |
| pub use self::repeat::{repeat, Repeat}; |
| |
| mod chain; |
| pub use self::chain::Chain; |
| |
| mod concat; |
| pub use self::concat::Concat; |
| |
| mod empty; |
| pub use self::empty::{empty, Empty}; |
| |
| mod filter; |
| pub use self::filter::Filter; |
| |
| mod filter_map; |
| pub use self::filter_map::FilterMap; |
| |
| mod flatten; |
| pub use self::flatten::Flatten; |
| |
| mod fold; |
| pub use self::fold::Fold; |
| |
| mod forward; |
| pub use self::forward::Forward; |
| |
| mod for_each; |
| pub use self::for_each::ForEach; |
| |
| mod fuse; |
| pub use self::fuse::Fuse; |
| |
| mod into_future; |
| pub use self::into_future::StreamFuture; |
| |
| mod inspect; |
| pub use self::inspect::Inspect; |
| |
| mod map; |
| pub use self::map::Map; |
| |
| mod next; |
| pub use self::next::Next; |
| |
| mod select_next_some; |
| pub use self::select_next_some::SelectNextSome; |
| |
| mod once; |
| pub use self::once::{once, Once}; |
| |
| mod peek; |
| pub use self::peek::Peekable; |
| |
| mod poll_fn; |
| pub use self::poll_fn::{poll_fn, PollFn}; |
| |
| mod select; |
| pub use self::select::Select; |
| |
| mod skip; |
| pub use self::skip::Skip; |
| |
| mod skip_while; |
| pub use self::skip_while::SkipWhile; |
| |
| mod take; |
| pub use self::take::Take; |
| |
| mod take_while; |
| pub use self::take_while::TakeWhile; |
| |
| mod then; |
| pub use self::then::Then; |
| |
| mod unfold; |
| pub use self::unfold::{unfold, Unfold}; |
| |
| mod zip; |
| pub use self::zip::Zip; |
| |
| #[cfg(feature = "std")] |
| use std; |
| #[cfg(feature = "std")] |
| use std::iter::Extend; |
| |
| #[cfg(feature = "std")] |
| mod buffer_unordered; |
| #[cfg(feature = "std")] |
| pub use self::buffer_unordered::BufferUnordered; |
| |
| #[cfg(feature = "std")] |
| mod buffered; |
| #[cfg(feature = "std")] |
| pub use self::buffered::Buffered; |
| |
| #[cfg(feature = "std")] |
| mod catch_unwind; |
| #[cfg(feature = "std")] |
| pub use self::catch_unwind::CatchUnwind; |
| |
| #[cfg(feature = "std")] |
| mod chunks; |
| #[cfg(feature = "std")] |
| pub use self::chunks::Chunks; |
| |
| #[cfg(feature = "std")] |
| mod collect; |
| #[cfg(feature = "std")] |
| pub use self::collect::Collect; |
| |
| #[cfg(feature = "std")] |
| mod for_each_concurrent; |
| #[cfg(feature = "std")] |
| pub use self::for_each_concurrent::ForEachConcurrent; |
| |
| #[cfg(feature = "std")] |
| mod futures_ordered; |
| #[cfg(feature = "std")] |
| pub use self::futures_ordered::{futures_ordered, FuturesOrdered}; |
| |
| #[cfg(feature = "std")] |
| mod futures_unordered; |
| #[cfg(feature = "std")] |
| pub use self::futures_unordered::{futures_unordered, FuturesUnordered}; |
| |
| #[cfg(feature = "std")] |
| mod split; |
| #[cfg(feature = "std")] |
| pub use self::split::{SplitStream, SplitSink, ReuniteError}; |
| |
| #[cfg(feature = "std")] |
| mod select_all; |
| #[cfg(feature = "std")] |
| pub use self::select_all::{select_all, SelectAll}; |
| |
| impl<T: ?Sized> StreamExt for T where T: Stream {} |
| |
| /// An extension trait for `Stream`s that provides a variety of convenient |
| /// combinator functions. |
| pub trait StreamExt: Stream { |
| /// Creates a future that resolves to the next item in the stream. |
| /// |
| /// Note that because `next` doesn't take ownership over the stream, |
| /// the [`Stream`] type must be [`Unpin`]. If you want to use `next` with a |
| /// [`!Unpin`](Unpin) stream, you'll first have to pin the stream. This can |
| /// be done by boxing the stream using [`Box::pinned`] or |
| /// pinning it to the stack using the `pin_mut!` macro from the `pin_utils` |
| /// crate. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let mut stream = stream::iter(1..=3); |
| /// |
| /// assert_eq!(block_on(stream.next()), Some(1)); |
| /// assert_eq!(block_on(stream.next()), Some(2)); |
| /// assert_eq!(block_on(stream.next()), Some(3)); |
| /// assert_eq!(block_on(stream.next()), None); |
| /// ``` |
| fn next(&mut self) -> Next<'_, Self> |
| where Self: Sized + Unpin, |
| { |
| Next::new(self) |
| } |
| |
| /// Converts this stream into a future of `(next_item, tail_of_stream)`. |
| /// If the stream terminates, then the next item is [`None`]. |
| /// |
| /// The returned future can be used to compose streams and futures together |
| /// by placing everything into the "world of futures". |
| /// |
| /// Note that because `into_future` moves the stream, the [`Stream`] type |
| /// must be [`Unpin`]. If you want to use `into_future` with a |
| /// [`!Unpin`](Unpin) stream, you'll first have to pin the stream. This can |
| /// be done by boxing the stream using [`Box::pinned`] or |
| /// pinning it to the stack using the `pin_mut!` macro from the `pin_utils` |
| /// crate. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=3); |
| /// |
| /// let (item, stream) = block_on(stream.into_future()); |
| /// assert_eq!(Some(1), item); |
| /// |
| /// let (item, stream) = block_on(stream.into_future()); |
| /// assert_eq!(Some(2), item); |
| /// ``` |
| fn into_future(self) -> StreamFuture<Self> |
| where Self: Sized + Unpin, |
| { |
| StreamFuture::new(self) |
| } |
| |
| /// Maps this stream's items to a different type, returning a new stream of |
| /// the resulting type. |
| /// |
| /// The provided closure is executed over all elements of this stream as |
| /// they are made available. It is executed inline with calls to |
| /// [`poll_next`](Stream::poll_next). |
| /// |
| /// Note that this function consumes the stream passed into it and returns a |
| /// wrapped version of it, similar to the existing `map` methods in the |
| /// standard library. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=3); |
| /// let stream = stream.map(|x| x + 3); |
| /// |
| /// assert_eq!(vec![4, 5, 6], block_on(stream.collect::<Vec<_>>())); |
| /// ``` |
| fn map<T, F>(self, f: F) -> Map<Self, F> |
| where F: FnMut(Self::Item) -> T, |
| Self: Sized |
| { |
| Map::new(self, f) |
| } |
| |
| /// Filters the values produced by this stream according to the provided |
| /// asynchronous predicate. |
| /// |
| /// As values of this stream are made available, the provided predicate `f` |
| /// will be run against them. If the predicate returns a `Future` which |
| /// resolves to `true`, then the stream will yield the value, but if the |
| /// predicate returns a `Future` which resolves to `false`, then the value |
| /// will be discarded and the next value will be produced. |
| /// |
| /// Note that this function consumes the stream passed into it and returns a |
| /// wrapped version of it, similar to the existing `filter` methods in the |
| /// standard library. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::future; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=10); |
| /// let evens = stream.filter(|x| future::ready(x % 2 == 0)); |
| /// |
| /// assert_eq!(vec![2, 4, 6, 8, 10], block_on(evens.collect::<Vec<_>>())); |
| /// ``` |
| fn filter<Fut, F>(self, f: F) -> Filter<Self, Fut, F> |
| where F: FnMut(&Self::Item) -> Fut, |
| Fut: Future<Output = bool>, |
| Self: Sized, |
| { |
| Filter::new(self, f) |
| } |
| |
| /// Filters the values produced by this stream while simultaneously mapping |
| /// them to a different type according to the provided asynchronous closure. |
| /// |
| /// As values of this stream are made available, the provided function will |
| /// be run on them. If the future returned by the predicate `f` resolves to |
| /// [`Some(item)`](Some) then the stream will yield the value `item`, but if |
| /// it resolves to [`None`] then the next value will be produced. |
| /// |
| /// Note that this function consumes the stream passed into it and returns a |
| /// wrapped version of it, similar to the existing `filter_map` methods in |
| /// the standard library. |
| /// |
| /// # Examples |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::future; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=10); |
| /// let evens = stream.filter_map(|x| { |
| /// let ret = if x % 2 == 0 { Some(x + 1) } else { None }; |
| /// future::ready(ret) |
| /// }); |
| /// |
| /// assert_eq!(vec![3, 5, 7, 9, 11], block_on(evens.collect::<Vec<_>>())); |
| /// ``` |
| fn filter_map<Fut, T, F>(self, f: F) -> FilterMap<Self, Fut, F> |
| where F: FnMut(Self::Item) -> Fut, |
| Fut: Future<Output = Option<T>>, |
| Self: Sized, |
| { |
| FilterMap::new(self, f) |
| } |
| |
| /// Computes from this stream's items new items of a different type using |
| /// an asynchronous closure. |
| /// |
| /// The provided closure `f` will be called with an `Item` once a value is |
| /// ready, it returns a future which will then be run to completion |
| /// to produce the next value on this stream. |
| /// |
| /// Note that this function consumes the stream passed into it and returns a |
| /// wrapped version of it. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::future; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=3); |
| /// let stream = stream.then(|x| future::ready(x + 3)); |
| /// |
| /// assert_eq!(vec![4, 5, 6], block_on(stream.collect::<Vec<_>>())); |
| /// ``` |
| fn then<Fut, F>(self, f: F) -> Then<Self, Fut, F> |
| where F: FnMut(Self::Item) -> Fut, |
| Fut: Future, |
| Self: Sized |
| { |
| Then::new(self, f) |
| } |
| |
| /// Collect all of the values of this stream into a vector, returning a |
| /// future representing the result of that computation. |
| /// |
| /// The returned future will be resolved when the stream terminates. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::channel::mpsc; |
| /// use futures::executor::block_on; |
| /// use futures::stream::StreamExt; |
| /// use std::thread; |
| /// |
| /// let (mut tx, rx) = mpsc::unbounded(); |
| /// |
| /// thread::spawn(move || { |
| /// for i in (1..=5) { |
| /// tx.unbounded_send(i).unwrap(); |
| /// } |
| /// }); |
| /// |
| /// let output = block_on(rx.collect::<Vec<i32>>()); |
| /// assert_eq!(output, vec![1, 2, 3, 4, 5]); |
| /// ``` |
| #[cfg(feature = "std")] |
| fn collect<C: Default + Extend<Self::Item>>(self) -> Collect<Self, C> |
| where Self: Sized |
| { |
| Collect::new(self) |
| } |
| |
| /// Concatenate all items of a stream into a single extendable |
| /// destination, returning a future representing the end result. |
| /// |
| /// This combinator will extend the first item with the contents |
| /// of all the subsequent results of the stream. If the stream is |
| /// empty, the default value will be returned. |
| /// |
| /// Works with all collections that implement the |
| /// [`Extend`](std::iter::Extend) trait. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::channel::mpsc; |
| /// use futures::executor::block_on; |
| /// use futures::stream::StreamExt; |
| /// use std::thread; |
| /// |
| /// let (mut tx, rx) = mpsc::unbounded(); |
| /// |
| /// thread::spawn(move || { |
| /// for i in (0..3).rev() { |
| /// let n = i * 3; |
| /// tx.unbounded_send(vec![n + 1, n + 2, n + 3]).unwrap(); |
| /// } |
| /// }); |
| /// |
| /// let result = block_on(rx.concat()); |
| /// |
| /// assert_eq!(result, vec![7, 8, 9, 4, 5, 6, 1, 2, 3]); |
| /// ``` |
| fn concat(self) -> Concat<Self> |
| where Self: Sized, |
| Self::Item: Extend<<<Self as Stream>::Item as IntoIterator>::Item> + |
| IntoIterator + Default, |
| { |
| Concat::new(self) |
| } |
| |
| /// Execute an accumulating asynchronous computation over a stream, |
| /// collecting all the values into one final result. |
| /// |
| /// This combinator will accumulate all values returned by this stream |
| /// according to the closure provided. The initial state is also provided to |
| /// this method and then is returned again by each execution of the closure. |
| /// Once the entire stream has been exhausted the returned future will |
| /// resolve to this value. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::future; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let number_stream = stream::iter(0..6); |
| /// let sum = number_stream.fold(0, |acc, x| future::ready(acc + x)); |
| /// assert_eq!(block_on(sum), 15); |
| /// ``` |
| fn fold<T, Fut, F>(self, init: T, f: F) -> Fold<Self, Fut, T, F> |
| where F: FnMut(T, Self::Item) -> Fut, |
| Fut: Future<Output = T>, |
| Self: Sized |
| { |
| Fold::new(self, f, init) |
| } |
| |
| /// Flattens a stream of streams into just one continuous stream. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::channel::mpsc; |
| /// use futures::executor::block_on; |
| /// use futures::stream::StreamExt; |
| /// use std::thread; |
| /// |
| /// let (tx1, rx1) = mpsc::unbounded(); |
| /// let (tx2, rx2) = mpsc::unbounded(); |
| /// let (tx3, rx3) = mpsc::unbounded(); |
| /// |
| /// thread::spawn(move || { |
| /// tx1.unbounded_send(1).unwrap(); |
| /// tx1.unbounded_send(2).unwrap(); |
| /// }); |
| /// thread::spawn(move || { |
| /// tx2.unbounded_send(3).unwrap(); |
| /// tx2.unbounded_send(4).unwrap(); |
| /// }); |
| /// thread::spawn(move || { |
| /// tx3.unbounded_send(rx1).unwrap(); |
| /// tx3.unbounded_send(rx2).unwrap(); |
| /// }); |
| /// |
| /// let output = block_on(rx3.flatten().collect::<Vec<i32>>()); |
| /// assert_eq!(output, vec![1, 2, 3, 4]); |
| /// ``` |
| fn flatten(self) -> Flatten<Self> |
| where Self::Item: Stream, |
| Self: Sized |
| { |
| Flatten::new(self) |
| } |
| |
| /// Skip elements on this stream while the provided asynchronous predicate |
| /// resolves to `true`. |
| /// |
| /// This function, like `Iterator::skip_while`, will skip elements on the |
| /// stream until the predicate `f` resolves to `false`. Once one element |
| /// returns false all future elements will be returned from the underlying |
| /// stream. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::future; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=10); |
| /// |
| /// let stream = stream.skip_while(|x| future::ready(*x <= 5)); |
| /// |
| /// assert_eq!(vec![6, 7, 8, 9, 10], block_on(stream.collect::<Vec<_>>())); |
| /// ``` |
| fn skip_while<Fut, F>(self, f: F) -> SkipWhile<Self, Fut, F> |
| where F: FnMut(&Self::Item) -> Fut, |
| Fut: Future<Output = bool>, |
| Self: Sized |
| { |
| SkipWhile::new(self, f) |
| } |
| |
| /// Take elements from this stream while the provided asynchronous predicate |
| /// resolves to `true`. |
| /// |
| /// This function, like `Iterator::take_while`, will take elements from the |
| /// stream until the predicate `f` resolves to `false`. Once one element |
| /// returns false it will always return that the stream is done. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::future; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=10); |
| /// |
| /// let stream = stream.take_while(|x| future::ready(*x <= 5)); |
| /// |
| /// assert_eq!(vec![1, 2, 3, 4, 5], block_on(stream.collect::<Vec<_>>())); |
| /// ``` |
| fn take_while<Fut, F>(self, f: F) -> TakeWhile<Self, Fut, F> |
| where F: FnMut(&Self::Item) -> Fut, |
| Fut: Future<Output = bool>, |
| Self: Sized |
| { |
| TakeWhile::new(self, f) |
| } |
| |
| /// Runs this stream to completion, executing the provided asynchronous |
| /// closure for each element on the stream. |
| /// |
| /// The closure provided will be called for each item this stream produces, |
| /// yielding a future. That future will then be executed to completion |
| /// before moving on to the next item. |
| /// |
| /// The returned value is a `Future` where the `Output` type is `()`; it is |
| /// executed entirely for its side effects. |
| /// |
| /// To process each item in the stream and produce another stream instead |
| /// of a single future, use `then` instead. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::future; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let mut x = 0; |
| /// |
| /// { |
| /// let fut = stream::repeat(1).take(3).for_each(|item| { |
| /// x += item; |
| /// future::ready(()) |
| /// }); |
| /// block_on(fut); |
| /// } |
| /// |
| /// assert_eq!(x, 3); |
| /// ``` |
| fn for_each<Fut, F>(self, f: F) -> ForEach<Self, Fut, F> |
| where F: FnMut(Self::Item) -> Fut, |
| Fut: Future<Output = ()>, |
| Self: Sized |
| { |
| ForEach::new(self, f) |
| } |
| |
| /// Runs this stream to completion, executing the provided asynchronous |
| /// closure for each element on the stream concurrently as elements become |
| /// available. |
| /// |
| /// This is similar to [`StreamExt::for_each`], but the futures |
| /// produced by the closure are run concurrently (but not in parallel-- |
| /// this combinator does not introduce any threads). |
| /// |
| /// The closure provided will be called for each item this stream produces, |
| /// yielding a future. That future will then be executed to completion |
| /// concurrently with the other futures produced by the closure. |
| /// |
| /// The first argument is an optional limit on the number of concurrent |
| /// futures. If this limit is not `None`, no more than `limit` futures |
| /// will be run concurrently. The `limit` argument is of type |
| /// `Into<Option<usize>>`, and so can be provided as either `None`, |
| /// `Some(10)`, or just `10`. Note: a limit of zero is interpreted as |
| /// no limit at all, and will have the same result as passing in `None`. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(async_await, await_macro)] |
| /// # futures::executor::block_on(async { |
| /// use futures::channel::oneshot; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let (tx1, rx1) = oneshot::channel(); |
| /// let (tx2, rx2) = oneshot::channel(); |
| /// let (tx3, rx3) = oneshot::channel(); |
| /// |
| /// let fut = stream::iter(vec![rx1, rx2, rx3]).for_each_concurrent( |
| /// /* limit */ 2, |
| /// async move |rx| { |
| /// await!(rx).unwrap(); |
| /// } |
| /// ); |
| /// tx1.send(()).unwrap(); |
| /// tx2.send(()).unwrap(); |
| /// tx3.send(()).unwrap(); |
| /// await!(fut); |
| /// # }) |
| /// ``` |
| #[cfg(feature = "std")] |
| fn for_each_concurrent<Fut, F>( |
| self, |
| limit: impl Into<Option<usize>>, |
| f: F, |
| ) -> ForEachConcurrent<Self, Fut, F> |
| where F: FnMut(Self::Item) -> Fut, |
| Fut: Future<Output = ()>, |
| Self: Sized, |
| { |
| ForEachConcurrent::new(self, limit.into(), f) |
| } |
| |
| /// Creates a new stream of at most `n` items of the underlying stream. |
| /// |
| /// Once `n` items have been yielded from this stream then it will always |
| /// return that the stream is done. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=10).take(3); |
| /// |
| /// assert_eq!(vec![1, 2, 3], block_on(stream.collect::<Vec<_>>())); |
| /// ``` |
| fn take(self, n: u64) -> Take<Self> |
| where Self: Sized |
| { |
| Take::new(self, n) |
| } |
| |
| /// Creates a new stream which skips `n` items of the underlying stream. |
| /// |
| /// Once `n` items have been skipped from this stream then it will always |
| /// return the remaining items on this stream. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(1..=10).skip(5); |
| /// |
| /// assert_eq!(vec![6, 7, 8, 9, 10], block_on(stream.collect::<Vec<_>>())); |
| /// ``` |
| fn skip(self, n: u64) -> Skip<Self> |
| where Self: Sized |
| { |
| Skip::new(self, n) |
| } |
| |
| /// Fuse a stream such that [`poll_next`](Stream::poll_next) will never |
| /// again be called once it has finished. This method can be used t turn |
| /// any `Stream` into a `FusedStream`. |
| /// |
| /// Normally, once a stream has returned [`None`] from |
| /// [`poll_next`](Stream::poll_next) any further calls could exhibit bad |
| /// behavior such as block forever, panic, never return, etc. If it is known |
| /// that [`poll_next`](Stream::poll_next) may be called after stream |
| /// has already finished, then this method can be used to ensure that it has |
| /// defined semantics. |
| /// |
| /// The [`poll_next`](Stream::poll_next) method of a `fuse`d stream |
| /// is guaranteed to return [`None`] after the underlying stream has |
| /// finished. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(futures_api)] |
| /// use futures::executor::block_on_stream; |
| /// use futures::stream::{self, StreamExt}; |
| /// use futures::task::Poll; |
| /// |
| /// let mut x = 0; |
| /// let stream = stream::poll_fn(|_| { |
| /// x += 1; |
| /// match x { |
| /// 0..=2 => Poll::Ready(Some(x)), |
| /// 3 => Poll::Ready(None), |
| /// _ => panic!("should not happen") |
| /// } |
| /// }).fuse(); |
| /// |
| /// let mut iter = block_on_stream(stream); |
| /// assert_eq!(Some(1), iter.next()); |
| /// assert_eq!(Some(2), iter.next()); |
| /// assert_eq!(None, iter.next()); |
| /// assert_eq!(None, iter.next()); |
| /// // ... |
| /// ``` |
| fn fuse(self) -> Fuse<Self> |
| where Self: Sized |
| { |
| Fuse::new(self) |
| } |
| |
| /// Borrows a stream, rather than consuming it. |
| /// |
| /// This is useful to allow applying stream adaptors while still retaining |
| /// ownership of the original stream. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::future; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let mut stream = stream::iter(1..5); |
| /// |
| /// let sum = block_on(stream.by_ref() |
| /// .take(2) |
| /// .fold(0, |a, b| future::ready(a + b))); |
| /// assert_eq!(sum, 3); |
| /// |
| /// // You can use the stream again |
| /// let sum = block_on(stream.take(2).fold(0, |a, b| future::ready(a + b))); |
| /// assert_eq!(sum, 7); |
| /// ``` |
| fn by_ref(&mut self) -> &mut Self |
| where Self: Sized |
| { |
| self |
| } |
| |
| /// Catches unwinding panics while polling the stream. |
| /// |
| /// Caught panic (if any) will be the last element of the resulting stream. |
| /// |
| /// In general, panics within a stream can propagate all the way out to the |
| /// task level. This combinator makes it possible to halt unwinding within |
| /// the stream itself. It's most commonly used within task executors. This |
| /// method should not be used for error handling. |
| /// |
| /// Note that this method requires the `UnwindSafe` bound from the standard |
| /// library. This isn't always applied automatically, and the standard |
| /// library provides an `AssertUnwindSafe` wrapper type to apply it |
| /// after-the fact. To assist using this method, the [`Stream`] trait is |
| /// also implemented for `AssertUnwindSafe<St>` where `St` implements |
| /// [`Stream`]. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream = stream::iter(vec![Some(10), None, Some(11)]); |
| /// // Panic on second element |
| /// let stream_panicking = stream.map(|o| o.unwrap()); |
| /// // Collect all the results |
| /// let stream = stream_panicking.catch_unwind(); |
| /// |
| /// let results: Vec<Result<i32, _>> = block_on(stream.collect()); |
| /// match results[0] { |
| /// Ok(10) => {} |
| /// _ => panic!("unexpected result!"), |
| /// } |
| /// assert!(results[1].is_err()); |
| /// assert_eq!(results.len(), 2); |
| /// ``` |
| #[cfg(feature = "std")] |
| fn catch_unwind(self) -> CatchUnwind<Self> |
| where Self: Sized + std::panic::UnwindSafe |
| { |
| CatchUnwind::new(self) |
| } |
| |
| /// Wrap the stream in a Box, pinning it. |
| #[cfg(feature = "std")] |
| fn boxed(self) -> Pin<Box<Self>> |
| where Self: Sized |
| { |
| Box::pin(self) |
| } |
| |
| /// An adaptor for creating a buffered list of pending futures. |
| /// |
| /// If this stream's item can be converted into a future, then this adaptor |
| /// will buffer up to at most `n` futures and then return the outputs in the |
| /// same order as the underlying stream. No more than `n` futures will be |
| /// buffered at any point in time, and less than `n` may also be buffered |
| /// depending on the state of each future. |
| /// |
| /// The returned stream will be a stream of each future's output. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| #[cfg(feature = "std")] |
| fn buffered(self, n: usize) -> Buffered<Self> |
| where Self::Item: Future, |
| Self: Sized |
| { |
| Buffered::new(self, n) |
| } |
| |
| /// An adaptor for creating a buffered list of pending futures (unordered). |
| /// |
| /// If this stream's item can be converted into a future, then this adaptor |
| /// will buffer up to `n` futures and then return the outputs in the order |
| /// in which they complete. No more than `n` futures will be buffered at |
| /// any point in time, and less than `n` may also be buffered depending on |
| /// the state of each future. |
| /// |
| /// The returned stream will be a stream of each future's output. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(async_await, await_macro)] |
| /// # futures::executor::block_on(async { |
| /// use futures::channel::oneshot; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let (send_one, recv_one) = oneshot::channel(); |
| /// let (send_two, recv_two) = oneshot::channel(); |
| /// |
| /// let stream_of_futures = stream::iter(vec![recv_one, recv_two]); |
| /// let mut buffered = stream_of_futures.buffer_unordered(10); |
| /// |
| /// send_two.send(2i32); |
| /// assert_eq!(await!(buffered.next()), Some(Ok(2i32))); |
| /// |
| /// send_one.send(1i32); |
| /// assert_eq!(await!(buffered.next()), Some(Ok(1i32))); |
| /// |
| /// assert_eq!(await!(buffered.next()), None); |
| /// # }) |
| /// ``` |
| #[cfg(feature = "std")] |
| fn buffer_unordered(self, n: usize) -> BufferUnordered<Self> |
| where Self::Item: Future, |
| Self: Sized |
| { |
| BufferUnordered::new(self, n) |
| } |
| |
| /// An adapter for zipping two streams together. |
| /// |
| /// The zipped stream waits for both streams to produce an item, and then |
| /// returns that pair. If either stream ends then the zipped stream will |
| /// also end. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let mut stream1 = stream::iter(1..=3); |
| /// let mut stream2 = stream::iter(5..=10); |
| /// |
| /// let vec = block_on(stream1.zip(stream2) |
| /// .collect::<Vec<_>>()); |
| /// assert_eq!(vec![(1, 5), (2, 6), (3, 7)], vec); |
| /// ``` |
| /// |
| fn zip<St>(self, other: St) -> Zip<Self, St> |
| where St: Stream, |
| Self: Sized, |
| { |
| Zip::new(self, other) |
| } |
| |
| /// Adapter for chaining two stream. |
| /// |
| /// The resulting stream emits elements from the first stream, and when |
| /// first stream reaches the end, emits the elements from the second stream. |
| /// |
| /// ``` |
| /// use futures::executor::block_on; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream1 = stream::iter(vec![Ok(10), Err(false)]); |
| /// let stream2 = stream::iter(vec![Err(true), Ok(20)]); |
| /// |
| /// let stream = stream1.chain(stream2); |
| /// |
| /// let result: Vec<_> = block_on(stream.collect()); |
| /// assert_eq!(result, vec![ |
| /// Ok(10), |
| /// Err(false), |
| /// Err(true), |
| /// Ok(20), |
| /// ]); |
| /// ``` |
| fn chain<St>(self, other: St) -> Chain<Self, St> |
| where St: Stream<Item = Self::Item>, |
| Self: Sized |
| { |
| Chain::new(self, other) |
| } |
| |
| /// Creates a new stream which exposes a `peek` method. |
| /// |
| /// Calling `peek` returns a reference to the next item in the stream. |
| fn peekable(self) -> Peekable<Self> |
| where Self: Sized |
| { |
| Peekable::new(self) |
| } |
| |
| /// An adaptor for chunking up items of the stream inside a vector. |
| /// |
| /// This combinator will attempt to pull items from this stream and buffer |
| /// them into a local vector. At most `capacity` items will get buffered |
| /// before they're yielded from the returned stream. |
| /// |
| /// Note that the vectors returned from this iterator may not always have |
| /// `capacity` elements. If the underlying stream ended and only a partial |
| /// vector was created, it'll be returned. Additionally if an error happens |
| /// from the underlying stream then the currently buffered items will be |
| /// yielded. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| /// |
| /// # Panics |
| /// |
| /// This method will panic of `capacity` is zero. |
| #[cfg(feature = "std")] |
| fn chunks(self, capacity: usize) -> Chunks<Self> |
| where Self: Sized |
| { |
| Chunks::new(self, capacity) |
| } |
| |
| /// 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. |
| /// |
| /// After one of the two input stream completes, the remaining one will be |
| /// polled exclusively. The returned stream completes when both input |
| /// streams have completed. |
| /// |
| /// Note that this method consumes both streams and returns a wrapped |
| /// version of them. |
| fn select<St>(self, other: St) -> Select<Self, St> |
| where St: Stream<Item = Self::Item>, |
| Self: Sized, |
| { |
| Select::new(self, other) |
| } |
| |
| /// A future that completes after the given stream has been fully processed |
| /// into the sink, including flushing. |
| /// |
| /// This future will drive the stream to keep producing items until it is |
| /// exhausted, sending each item to the sink. It will complete once both the |
| /// stream is exhausted and the sink has received and flushed all items. |
| /// Note that the sink is **not** closed. |
| /// |
| /// On completion, the sink is returned. |
| /// |
| /// Note that this combinator is only usable with `Unpin` sinks. |
| /// Sinks that are not `Unpin` will need to be pinned in order to be used |
| /// with `forward`. |
| fn forward<S>(self, sink: S) -> Forward<Self, S> |
| where |
| S: Sink + Unpin, |
| Self: Stream<Item = Result<S::SinkItem, S::SinkError>> + Sized, |
| { |
| Forward::new(self, sink) |
| } |
| |
| /// Splits this `Stream + Sink` object into separate `Stream` and `Sink` |
| /// objects. |
| /// |
| /// This can be useful when you want to split ownership between tasks, or |
| /// allow direct interaction between the two objects (e.g. via |
| /// `Sink::send_all`). |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| #[cfg(feature = "std")] |
| fn split(self) -> (SplitSink<Self>, SplitStream<Self>) |
| where Self: Sink + Sized |
| { |
| split::split(self) |
| } |
| |
| /// Do something with each item of this stream, afterwards passing it on. |
| /// |
| /// This is similar to the `Iterator::inspect` method in the standard |
| /// library where it allows easily inspecting each value as it passes |
| /// through the stream, for example to debug what's going on. |
| fn inspect<F>(self, f: F) -> Inspect<Self, F> |
| where F: FnMut(&Self::Item), |
| Self: Sized, |
| { |
| Inspect::new(self, f) |
| } |
| |
| /// Wrap this stream in an `Either` stream, making it the left-hand variant |
| /// of that `Either`. |
| /// |
| /// This can be used in combination with the `right_stream` method to write `if` |
| /// statements that evaluate to different streams in different branches. |
| fn left_stream<B>(self) -> Either<Self, B> |
| where B: Stream<Item = Self::Item>, |
| Self: Sized |
| { |
| Either::Left(self) |
| } |
| |
| /// Wrap this stream in an `Either` stream, making it the right-hand variant |
| /// of that `Either`. |
| /// |
| /// This can be used in combination with the `left_stream` method to write `if` |
| /// statements that evaluate to different streams in different branches. |
| fn right_stream<B>(self) -> Either<B, Self> |
| where B: Stream<Item = Self::Item>, |
| Self: Sized |
| { |
| Either::Right(self) |
| } |
| |
| /// A convenience method for calling [`Stream::poll_next`] on [`Unpin`] |
| /// stream types. |
| fn poll_next_unpin( |
| &mut self, |
| lw: &LocalWaker |
| ) -> Poll<Option<Self::Item>> |
| where Self: Unpin + Sized |
| { |
| Pin::new(self).poll_next(lw) |
| } |
| |
| /// Returns a [`Future`] that resolves when the next item in this stream is |
| /// ready. |
| /// |
| /// This is similar to the [`next`][StreamExt::next] method, but it won't |
| /// resolve to [`None`] if used on an empty [`Stream`]. Instead, the |
| /// returned future type will return [`true`] from |
| /// [`FusedFuture::is_terminated`][] when the [`Stream`] is empty, allowing |
| /// [`select_next_some`][StreamExt::select_next_some] to be easily used with |
| /// the [`select!`] macro. |
| /// |
| /// If the future is polled after this [`Stream`] is empty it will panic. |
| /// Using the future with a [`FusedFuture`][]-aware primitive like the |
| /// [`select!`] macro will prevent this. |
| /// |
| /// [`FusedFuture`]: futures_core::future::FusedFuture |
| /// [`FusedFuture::is_terminated`]: futures_core::future::FusedFuture::is_terminated |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(async_await, await_macro, futures_api)] |
| /// # futures::executor::block_on(async { |
| /// use futures::{future, select}; |
| /// use futures::stream::{StreamExt, FuturesUnordered}; |
| /// |
| /// let mut fut = future::ready(1); |
| /// let mut async_tasks = FuturesUnordered::new(); |
| /// let mut total = 0; |
| /// loop { |
| /// select! { |
| /// num = fut => { |
| /// // First, the `ready` future completes. |
| /// total += num; |
| /// // Then we spawn a new task onto `async_tasks`, |
| /// async_tasks.push(async { 5 }); |
| /// }, |
| /// // On the next iteration of the loop, the task we spawned |
| /// // completes. |
| /// num = async_tasks.select_next_some() => { |
| /// total += num; |
| /// } |
| /// // Finally, both the `ready` future and `async_tasks` have |
| /// // finished, so we enter the `complete` branch. |
| /// complete => break, |
| /// } |
| /// } |
| /// assert_eq!(total, 6); |
| /// # }); |
| /// ``` |
| fn select_next_some(&mut self) -> SelectNextSome<'_, Self> where Self: Sized + Unpin + FusedStream { |
| SelectNextSome::new(self) |
| } |
| } |