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//! Asynchronous streams //! //! This module contains the `Stream` trait and a number of adaptors for this //! trait. This trait is very similar to the `Iterator` trait in the standard //! library except that it expresses the concept of blocking as well. A stream //! here is a sequential sequence of values which may take some amount of time //! in between to produce. //! //! A stream may request that it is blocked between values while the next value //! is calculated, and provides a way to get notified once the next value is //! ready as well. //! //! You can find more information/tutorials about streams [online at //! https://tokio.rs][online] //! //! [online]: https://tokio.rs/docs/getting-started/streams-and-sinks/ use {IntoFuture, Poll}; mod iter; pub use self::iter::{iter, Iter}; #[cfg(feature = "with-deprecated")] pub use self::Iter as IterStream; mod repeat; pub use self::repeat::{repeat, Repeat}; mod and_then; mod chain; mod concat; mod empty; mod filter; mod filter_map; mod flatten; mod fold; mod for_each; mod from_err; mod fuse; mod future; mod map; mod map_err; mod merge; mod once; mod or_else; mod peek; mod select; mod skip; mod skip_while; mod take; mod take_while; mod then; mod unfold; mod zip; mod forward; pub use self::and_then::AndThen; pub use self::chain::Chain; pub use self::concat::Concat; pub use self::empty::{Empty, empty}; pub use self::filter::Filter; pub use self::filter_map::FilterMap; pub use self::flatten::Flatten; pub use self::fold::Fold; pub use self::for_each::ForEach; pub use self::from_err::FromErr; pub use self::fuse::Fuse; pub use self::future::StreamFuture; pub use self::map::Map; pub use self::map_err::MapErr; pub use self::merge::{Merge, MergedItem}; pub use self::once::{Once, once}; pub use self::or_else::OrElse; pub use self::peek::Peekable; pub use self::select::Select; pub use self::skip::Skip; pub use self::skip_while::SkipWhile; pub use self::take::Take; pub use self::take_while::TakeWhile; pub use self::then::Then; pub use self::unfold::{Unfold, unfold}; pub use self::zip::Zip; pub use self::forward::Forward; use sink::{Sink}; if_std! { use std; mod buffered; mod buffer_unordered; mod catch_unwind; mod chunks; mod collect; mod wait; mod channel; mod split; mod futures_unordered; pub use self::buffered::Buffered; pub use self::buffer_unordered::BufferUnordered; pub use self::catch_unwind::CatchUnwind; pub use self::chunks::Chunks; pub use self::collect::Collect; pub use self::wait::Wait; pub use self::split::{SplitStream, SplitSink}; pub use self::futures_unordered::{futures_unordered, FuturesUnordered}; #[doc(hidden)] #[cfg(feature = "with-deprecated")] #[allow(deprecated)] pub use self::channel::{channel, Sender, Receiver, FutureSender, SendError}; /// A type alias for `Box<Stream + Send>` pub type BoxStream<T, E> = ::std::boxed::Box<Stream<Item = T, Error = E> + Send>; impl<S: ?Sized + Stream> Stream for ::std::boxed::Box<S> { type Item = S::Item; type Error = S::Error; fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> { (**self).poll() } } } /// A stream of values, not all of which may have been produced yet. /// /// `Stream` is a trait to represent any source of sequential events or items /// which acts like an iterator but long periods of time may pass between /// items. Like `Future` the methods of `Stream` never block and it is thus /// suitable for programming in an asynchronous fashion. This trait is very /// similar to the `Iterator` trait in the standard library where `Some` is /// used to signal elements of the stream and `None` is used to indicate that /// the stream is finished. /// /// Like futures a stream has basic combinators to transform the stream, perform /// more work on each item, etc. /// /// You can find more information/tutorials about streams [online at /// https://tokio.rs][online] /// /// [online]: https://tokio.rs/docs/getting-started/streams-and-sinks/ /// /// # Streams as Futures /// /// Any instance of `Stream` can also be viewed as a `Future` where the resolved /// value is the next item in the stream along with the rest of the stream. The /// `into_future` adaptor can be used here to convert any stream into a future /// for use with other future methods like `join` and `select`. /// /// # Errors /// /// Streams, like futures, can also model errors in their computation. All /// streams have an associated `Error` type like with futures. Currently as of /// the 0.1 release of this library an error on a stream **does not terminate /// the stream**. That is, after one error is received, another error may be /// received from the same stream (it's valid to keep polling). /// /// This property of streams, however, is [being considered] for change in 0.2 /// where an error on a stream is similar to `None`, it terminates the stream /// entirely. If one of these use cases suits you perfectly and not the other, /// please feel welcome to comment on [the issue][being considered]! /// /// [being considered]: https://github.com/alexcrichton/futures-rs/issues/206 pub trait Stream { /// The type of item this stream will yield on success. type Item; /// The type of error this stream may generate. type Error; /// Attempt to pull out the next value of this stream, returning `None` if /// the stream is finished. /// /// This method, like `Future::poll`, is the sole method of pulling out a /// value from a stream. This method must also be run within the context of /// a task typically and implementors of this trait must ensure that /// implementations of this method do not block, as it may cause consumers /// to behave badly. /// /// # Return value /// /// If `NotReady` is returned then this stream's next value is not ready /// yet and implementations will ensure that the current task will be /// notified when the next value may be ready. If `Some` is returned then /// the returned value represents the next value on the stream. `Err` /// indicates an error happened, while `Ok` indicates whether there was a /// new item on the stream or whether the stream has terminated. /// /// # Panics /// /// Once a stream is finished, that is `Ready(None)` has been returned, /// further calls to `poll` may result in a panic or other "bad behavior". /// If this is difficult to guard against then the `fuse` adapter can be /// used to ensure that `poll` always has well-defined semantics. // TODO: more here fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error>; // TODO: should there also be a method like `poll` but doesn't return an // item? basically just says "please make more progress internally" // seems crucial for buffering to actually make any sense. /// Creates an iterator which blocks the current thread until each item of /// this stream is resolved. /// /// This method will consume ownership of this stream, returning an /// implementation of a standard iterator. This iterator will *block the /// current thread* on each call to `next` if the item in the stream isn't /// ready yet. /// /// > **Note:** This method is not appropriate to call on event loops or /// > similar I/O situations because it will prevent the event /// > loop from making progress (this blocks the thread). This /// > method should only be called when it's guaranteed that the /// > blocking work associated with this stream will be completed /// > by another thread. /// /// This method is only available when the `use_std` feature of this /// library is activated, and it is activated by default. /// /// # Panics /// /// The returned iterator does not attempt to catch panics. If the `poll` /// function panics, panics will be propagated to the caller of `next`. #[cfg(feature = "use_std")] fn wait(self) -> Wait<Self> where Self: Sized { wait::new(self) } /// Convenience function for turning this stream into a trait object. /// /// This simply avoids the need to write `Box::new` and can often help with /// type inference as well by always returning a trait object. Note that /// this method requires the `Send` bound and returns a `BoxStream`, which /// also encodes this. If you'd like to create a `Box<Stream>` without the /// `Send` bound, then the `Box::new` function can be used instead. /// /// This method is only available when the `use_std` feature of this /// library is activated, and it is activated by default. /// /// # Examples /// /// ``` /// use futures::stream::*; /// use futures::sync::mpsc; /// /// let (_tx, rx) = mpsc::channel(1); /// let a: BoxStream<i32, ()> = rx.boxed(); /// ``` #[cfg(feature = "use_std")] fn boxed(self) -> BoxStream<Self::Item, Self::Error> where Self: Sized + Send + 'static, { ::std::boxed::Box::new(self) } /// Converts this stream into a `Future`. /// /// A stream can be viewed as a future which will resolve to a pair containing /// the next element of the stream plus the remaining stream. If the stream /// terminates, then the next element is `None` and the remaining stream is /// still passed back, to allow reclamation of its resources. /// /// The returned future can be used to compose streams and futures together by /// placing everything into the "world of futures". fn into_future(self) -> StreamFuture<Self> where Self: Sized { future::new(self) } /// Converts a stream of type `T` to a stream of type `U`. /// /// The provided closure is executed over all elements of this stream as /// they are made available, and the callback will be executed inline with /// calls to `poll`. /// /// Note that this function consumes the receiving stream and returns a /// wrapped version of it, similar to the existing `map` methods in the /// standard library. /// /// # Examples /// /// ``` /// use futures::Stream; /// use futures::sync::mpsc; /// /// let (_tx, rx) = mpsc::channel::<i32>(1); /// let rx = rx.map(|x| x + 3); /// ``` fn map<U, F>(self, f: F) -> Map<Self, F> where F: FnMut(Self::Item) -> U, Self: Sized { map::new(self, f) } /// Converts a stream of error type `T` to a stream of error type `U`. /// /// The provided closure is executed over all errors of this stream as /// they are made available, and the callback will be executed inline with /// calls to `poll`. /// /// Note that this function consumes the receiving stream and returns a /// wrapped version of it, similar to the existing `map_err` methods in the /// standard library. /// /// # Examples /// /// ``` /// use futures::Stream; /// use futures::sync::mpsc; /// /// let (_tx, rx) = mpsc::channel::<i32>(1); /// let rx = rx.map_err(|()| 3); /// ``` fn map_err<U, F>(self, f: F) -> MapErr<Self, F> where F: FnMut(Self::Error) -> U, Self: Sized { map_err::new(self, f) } /// Filters the values produced by this stream according to the provided /// predicate. /// /// As values of this stream are made available, the provided predicate will /// be run against them. If the predicate returns `true` then the stream /// will yield the value, but if the predicate returns `false` then the /// value will be discarded and the next value will be produced. /// /// All errors are passed through without filtering in this combinator. /// /// Note that this function consumes the receiving stream and returns a /// wrapped version of it, similar to the existing `filter` methods in the /// standard library. /// /// # Examples /// /// ``` /// use futures::Stream; /// use futures::sync::mpsc; /// /// let (_tx, rx) = mpsc::channel::<i32>(1); /// let evens = rx.filter(|x| x % 0 == 2); /// ``` fn filter<F>(self, f: F) -> Filter<Self, F> where F: FnMut(&Self::Item) -> bool, Self: Sized { filter::new(self, f) } /// Filters the values produced by this stream while simultaneously mapping /// them to a different type. /// /// As values of this stream are made available, the provided function will /// be run on them. If the predicate returns `Some(e)` then the stream will /// yield the value `e`, but if the predicate returns `None` then the next /// value will be produced. /// /// All errors are passed through without filtering in this combinator. /// /// Note that this function consumes the receiving stream and returns a /// wrapped version of it, similar to the existing `filter_map` methods in the /// standard library. /// /// # Examples /// /// ``` /// use futures::Stream; /// use futures::sync::mpsc; /// /// let (_tx, rx) = mpsc::channel::<i32>(1); /// let evens_plus_one = rx.filter_map(|x| { /// if x % 0 == 2 { /// Some(x + 1) /// } else { /// None /// } /// }); /// ``` fn filter_map<F, B>(self, f: F) -> FilterMap<Self, F> where F: FnMut(Self::Item) -> Option<B>, Self: Sized { filter_map::new(self, f) } /// Chain on a computation for when a value is ready, passing the resulting /// item to the provided closure `f`. /// /// This function can be used to ensure a computation runs regardless of /// the next value on the stream. The closure provided will be yielded a /// `Result` once a value is ready, and the returned future will then be run /// to completion to produce the next value on this stream. /// /// The returned value of the closure must implement the `IntoFuture` trait /// and can represent some more work to be done before the composed stream /// is finished. Note that the `Result` type implements the `IntoFuture` /// trait so it is possible to simply alter the `Result` yielded to the /// closure and return it. /// /// Note that this function consumes the receiving stream and returns a /// wrapped version of it. /// /// # Examples /// /// ``` /// use futures::Stream; /// use futures::sync::mpsc; /// /// let (_tx, rx) = mpsc::channel::<i32>(1); /// /// let rx = rx.then(|result| { /// match result { /// Ok(e) => Ok(e + 3), /// Err(()) => Err(4), /// } /// }); /// ``` fn then<F, U>(self, f: F) -> Then<Self, F, U> where F: FnMut(Result<Self::Item, Self::Error>) -> U, U: IntoFuture, Self: Sized { then::new(self, f) } /// Chain on a computation for when a value is ready, passing the successful /// results to the provided closure `f`. /// /// This function can be used to run a unit of work when the next successful /// value on a stream is ready. The closure provided will be yielded a value /// when ready, and the returned future will then be run to completion to /// produce the next value on this stream. /// /// Any errors produced by this stream will not be passed to the closure, /// and will be passed through. /// /// The returned value of the closure must implement the `IntoFuture` trait /// and can represent some more work to be done before the composed stream /// is finished. Note that the `Result` type implements the `IntoFuture` /// trait so it is possible to simply alter the `Result` yielded to the /// closure and return it. /// /// Note that this function consumes the receiving stream and returns a /// wrapped version of it. /// /// # Examples /// /// ``` /// use futures::stream::*; /// use futures::sync::mpsc; /// /// let (_tx, rx) = mpsc::channel::<i32>(1); /// /// let rx = rx.and_then(|result| { /// if result % 2 == 0 { /// Ok(result) /// } else { /// Err(()) /// } /// }); /// ``` 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 { and_then::new(self, f) } /// Chain on a computation for when an error happens, passing the /// erroneous result to the provided closure `f`. /// /// This function can be used to run a unit of work and attempt to recover from /// an error if one happens. The closure provided will be yielded an error /// when one appears, and the returned future will then be run to completion /// to produce the next value on this stream. /// /// Any successful values produced by this stream will not be passed to the /// closure, and will be passed through. /// /// The returned value of the closure must implement the `IntoFuture` trait /// and can represent some more work to be done before the composed stream /// is finished. Note that the `Result` type implements the `IntoFuture` /// trait so it is possible to simply alter the `Result` yielded to the /// closure and return it. /// /// Note that this function consumes the receiving stream and returns a /// wrapped version of it. 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 { or_else::new(self, f) } /// Collect all of the values of this stream into a vector, returning a /// future representing the result of that computation. /// /// This combinator will collect all successful results of this stream and /// collect them into a `Vec<Self::Item>`. If an error happens then all /// collected elements will be dropped and the error will be returned. /// /// The returned future will be resolved whenever an error happens or when /// the stream returns `Ok(None)`. /// /// This method is only available when the `use_std` feature of this /// library is activated, and it is activated by default. /// /// # Examples /// /// ``` /// use std::thread; /// /// use futures::{Stream, Future, Sink}; /// use futures::sync::mpsc; /// /// let (mut tx, rx) = mpsc::channel(1); /// /// thread::spawn(|| { /// for i in (0..5).rev() { /// tx = tx.send(i + 1).wait().unwrap(); /// } /// }); /// /// let mut result = rx.collect(); /// assert_eq!(result.wait(), Ok(vec![5, 4, 3, 2, 1])); /// ``` #[cfg(feature = "use_std")] fn collect(self) -> Collect<Self> where Self: Sized { collect::new(self) } /// Concatenate all results 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 successful results of the stream. If an error /// occurs, all the results will be dropped and the error will be /// returned. /// /// # Examples /// /// ``` /// use std::thread; /// /// use futures::{Future, Sink, Stream}; /// use futures::sync::mpsc; /// /// let (mut tx, rx) = mpsc::channel(1); /// /// thread::spawn(move || { /// for i in (0..3).rev() { /// let n = i * 3; /// tx = tx.send(vec![n + 1, n + 2, n + 3]).wait().unwrap(); /// } /// }); /// let result = rx.concat(); /// assert_eq!(result.wait(), Ok(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, { concat::new(self) } /// Execute an accumulating computation over a stream, collecting all the /// values into one final result. /// /// This combinator will collect all successful results of 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. /// /// If an error happens then collected state will be dropped and the error /// will be returned. /// /// # Examples /// /// ``` /// use futures::stream::{self, Stream}; /// use futures::future::{ok, Future}; /// /// let number_stream = stream::iter::<_, _, ()>((0..6).map(Ok)); /// let sum = number_stream.fold(0, |a, b| ok(a + b)); /// assert_eq!(sum.wait(), Ok(15)); /// ``` 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 { fold::new(self, f, init) } /// Flattens a stream of streams into just one continuous stream. /// /// If this stream's elements are themselves streams then this combinator /// will flatten out the entire stream to one long chain of elements. Any /// errors are passed through without looking at them, but otherwise each /// individual stream will get exhausted before moving on to the next. /// /// ``` /// use std::thread; /// /// use futures::{Future, Stream, Poll, Sink}; /// use futures::sync::mpsc; /// /// let (tx1, rx1) = mpsc::channel::<i32>(1); /// let (tx2, rx2) = mpsc::channel::<i32>(1); /// let (tx3, rx3) = mpsc::channel(1); /// /// thread::spawn(|| { /// tx1.send(1).wait().unwrap() /// .send(2).wait().unwrap(); /// }); /// thread::spawn(|| { /// tx2.send(3).wait().unwrap() /// .send(4).wait().unwrap(); /// }); /// thread::spawn(|| { /// tx3.send(rx1).wait().unwrap() /// .send(rx2).wait().unwrap(); /// }); /// /// let mut result = rx3.flatten().collect(); /// assert_eq!(result.wait(), Ok(vec![1, 2, 3, 4])); /// ``` fn flatten(self) -> Flatten<Self> where Self::Item: Stream, <Self::Item as Stream>::Error: From<Self::Error>, Self: Sized { flatten::new(self) } /// Skip elements on this stream while the predicate provided resolves to /// `true`. /// /// This function, like `Iterator::skip_while`, will skip elements on the /// stream until the `predicate` resolves to `false`. Once one element /// returns false all future elements will be returned from the underlying /// 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_while::new(self, pred) } /// Take elements from this stream while the predicate provided resolves to /// `true`. /// /// This function, like `Iterator::take_while`, will take elements from the /// stream until the `predicate` resolves to `false`. Once one element /// returns false it will always return that the stream is done. 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_while::new(self, pred) } /// Runs this stream to completion, executing the provided closure for each /// element on the stream. /// /// The closure provided will be called for each item this stream resolves /// to successfully, producing 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 `Item` type is `()` and /// errors are otherwise threaded through. Any error on the stream or in the /// closure will cause iteration to be halted immediately and the future /// will resolve to that error. 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 { for_each::new(self, f) } /// Map this stream's error to any error implementing `From` for /// this stream's `Error`, returning a new stream. /// /// This function does for streams what `try!` does for `Result`, /// by letting the compiler infer the type of the resulting error. /// Just as `map_err` above, this is useful for example to ensure /// that streams have the same error type when used with /// combinators. /// /// Note that this function consumes the receiving stream and returns a /// wrapped version of it. fn from_err<E: From<Self::Error>>(self) -> FromErr<Self, E> where Self: Sized, { from_err::new(self) } /// Creates a new stream of at most `amt` items of the underlying stream. /// /// Once `amt` items have been yielded from this stream then it will always /// return that the stream is done. /// /// # Errors /// /// Any errors yielded from underlying stream, before the desired amount of /// items is reached, are passed through and do not affect the total number /// of items taken. fn take(self, amt: u64) -> Take<Self> where Self: Sized { take::new(self, amt) } /// Creates a new stream which skips `amt` items of the underlying stream. /// /// Once `amt` items have been skipped from this stream then it will always /// return the remaining items on this stream. /// /// # Errors /// /// All errors yielded from underlying stream are passed through and do not /// affect the total number of items skipped. fn skip(self, amt: u64) -> Skip<Self> where Self: Sized { skip::new(self, amt) } /// Fuse a stream such that `poll` will never again be called once it has /// finished. /// /// Currently once a stream has returned `None` from `poll` any further /// calls could exhibit bad behavior such as block forever, panic, never /// return, etc. If it is known that `poll` may be called after stream has /// already finished, then this method can be used to ensure that it has /// defined semantics. /// /// Once a stream has been `fuse`d and it finishes, then it will forever /// return `None` from `poll`. This, unlike for the traits `poll` method, /// is guaranteed. /// /// Also note that as soon as this stream returns `None` it will be dropped /// to reclaim resources associated with it. fn fuse(self) -> Fuse<Self> where Self: Sized { fuse::new(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<S>` where `S` implements `Stream`. /// /// This method is only available when the `use_std` feature of this /// library is activated, and it is activated by default. /// /// # Examples /// /// ```rust /// use futures::stream; /// use futures::stream::Stream; /// /// let stream = stream::iter::<_, Option<i32>, bool>(vec![ /// Some(10), None, Some(11)].into_iter().map(Ok)); /// // panic on second element /// let stream_panicking = stream.map(|o| o.unwrap()); /// let mut iter = stream_panicking.catch_unwind().wait(); /// /// assert_eq!(Ok(10), iter.next().unwrap().ok().unwrap()); /// assert!(iter.next().unwrap().is_err()); /// assert!(iter.next().is_none()); /// ``` #[cfg(feature = "use_std")] fn catch_unwind(self) -> CatchUnwind<Self> where Self: Sized + std::panic::UnwindSafe { catch_unwind::new(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 `amt` futures and then return results in the /// same order as the underlying stream. No more than `amt` futures will be /// buffered at any point in time, and less than `amt` may also be buffered /// depending on the state of each future. /// /// The returned stream will be a stream of each future's result, with /// errors passed through whenever they occur. /// /// This method is only available when the `use_std` feature of this /// library is activated, and it is activated by default. #[cfg(feature = "use_std")] fn buffered(self, amt: usize) -> Buffered<Self> where Self::Item: IntoFuture<Error = <Self as Stream>::Error>, Self: Sized { buffered::new(self, amt) } /// 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 `amt` futures and then return results in the order /// in which they complete. No more than `amt` futures will be buffered at /// any point in time, and less than `amt` may also be buffered depending on /// the state of each future. /// /// The returned stream will be a stream of each future's result, with /// errors passed through whenever they occur. /// /// This method is only available when the `use_std` feature of this /// library is activated, and it is activated by default. #[cfg(feature = "use_std")] fn buffer_unordered(self, amt: usize) -> BufferUnordered<Self> where Self::Item: IntoFuture<Error = <Self as Stream>::Error>, Self: Sized { buffer_unordered::new(self, amt) } /// An adapter for merging the output of two streams. /// /// The merged stream produces items from one or both of the underlying /// streams as they become available. Errors, however, are not merged: you /// get at most one error at a time. fn merge<S>(self, other: S) -> Merge<Self, S> where S: Stream<Error = Self::Error>, Self: Sized, { merge::new(self, other) } /// An adapter for zipping two streams together. /// /// The zipped stream waits for both streams to produce an item, and then /// returns that pair. If an error happens, then that error will be returned /// immediately. If either stream ends then the zipped stream will also end. fn zip<S>(self, other: S) -> Zip<Self, S> where S: Stream<Error = Self::Error>, 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. /// /// ```rust /// use futures::stream; /// use futures::stream::Stream; /// /// let stream1 = stream::iter(vec![Ok(10), Err(false)]); /// let stream2 = stream::iter(vec![Err(true), Ok(20)]); /// let mut chain = stream1.chain(stream2).wait(); /// /// assert_eq!(Some(Ok(10)), chain.next()); /// assert_eq!(Some(Err(false)), chain.next()); /// assert_eq!(Some(Err(true)), chain.next()); /// assert_eq!(Some(Ok(20)), chain.next()); /// assert_eq!(None, chain.next()); /// ``` fn chain<S>(self, other: S) -> Chain<Self, S> where S: Stream<Item = Self::Item, Error = Self::Error>, 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 { peek::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. /// /// Errors are passed through the stream unbuffered. /// /// This method is only available when the `use_std` feature of this /// library is activated, and it is activated by default. /// /// # Panics /// /// This method will panic of `capacity` is zero. #[cfg(feature = "use_std")] fn chunks(self, capacity: usize) -> Chunks<Self> where Self: Sized { chunks::new(self, capacity) } /// Creates a stream that selects the next element from either this stream /// or the provided one, whichever is ready first. /// /// 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. /// /// The `select` function is similar to `merge` except that it requires both /// streams to have the same item and error types. /// /// Error are passed through from either stream. fn select<S>(self, other: S) -> Select<Self, S> where S: Stream<Item = Self::Item, Error = Self::Error>, 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 fully processed and flushed all of /// the items sent to it. /// /// Doing `stream.forward(sink)` is roughly equivalent to /// `sink.send_all(stream)`. /// /// On completion, the pair `(stream, sink)` is returned. fn forward<S>(self, sink: S) -> Forward<Self, S> where S: Sink<SinkItem = Self::Item>, Self::Error: From<S::SinkError>, Self: 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 `use_std` feature of this /// library is activated, and it is activated by default. #[cfg(feature = "use_std")] fn split(self) -> (SplitSink<Self>, SplitStream<Self>) where Self: super::sink::Sink + Sized { split::split(self) } } impl<'a, S: ?Sized + Stream> Stream for &'a mut S { type Item = S::Item; type Error = S::Error; fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> { (**self).poll() } }