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//! Abstractions for asynchronous programming. //! //! This crate provides a number of core abstractions for writing asynchronous //! code: //! //! - [Futures](crate::future::Future) are single eventual values produced by //! asynchronous computations. Some programming languages (e.g. JavaScript) //! call this concept "promise". //! - [Streams](crate::stream::Stream) represent a series of values //! produced asynchronously. //! - [Sinks](crate::sink::Sink) provide support for asynchronous writing of //! data. //! - [Executors](crate::executor) are responsible for running asynchronous //! tasks. //! //! The crate also contains abstractions for [asynchronous I/O](crate::io) and //! [cross-task communication](crate::channel). //! //! Underlying all of this is the *task system*, which is a form of lightweight //! threading. Large asynchronous computations are built up using futures, //! streams and sinks, and then spawned as independent tasks that are run to //! completion, but *do not block* the thread running them. #![cfg_attr(feature = "cfg-target-has-atomic", feature(cfg_target_has_atomic))] #![cfg_attr(feature = "read_initializer", feature(read_initializer))] #![cfg_attr(not(feature = "std"), no_std)] #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms, unreachable_pub)] // It cannot be included in the published code because this lints have false positives in the minimum required version. #![cfg_attr(test, warn(single_use_lifetimes))] #![warn(clippy::all)] #![doc(test(attr(deny(warnings), allow(dead_code, unused_assignments, unused_variables))))] #![doc(html_root_url = "https://rust-lang-nursery.github.io/futures-api-docs/0.3.0-alpha.19/futures")] #[cfg(all(feature = "cfg-target-has-atomic", not(feature = "unstable")))] compile_error!("The `cfg-target-has-atomic` feature requires the `unstable` feature as an explicit opt-in to unstable features"); #[cfg(all(feature = "bilock", not(feature = "unstable")))] compile_error!("The `bilock` feature requires the `unstable` feature as an explicit opt-in to unstable features"); #[cfg(all(feature = "read_initializer", not(feature = "unstable")))] compile_error!("The `read_initializer` feature requires the `unstable` feature as an explicit opt-in to unstable features"); #[doc(hidden)] pub use futures_core::core_reexport; #[doc(hidden)] pub use futures_core::future::Future; #[doc(hidden)] pub use futures_core::future::TryFuture; #[doc(hidden)] pub use futures_util::future::FutureExt; #[doc(hidden)] pub use futures_util::try_future::TryFutureExt; #[doc(hidden)] pub use futures_core::stream::Stream; #[doc(hidden)] pub use futures_core::stream::TryStream; #[doc(hidden)] pub use futures_util::stream::StreamExt; #[doc(hidden)] pub use futures_util::try_stream::TryStreamExt; #[doc(hidden)] pub use futures_sink::Sink; #[doc(hidden)] pub use futures_util::sink::SinkExt; #[cfg(feature = "std")] #[doc(hidden)] pub use futures_io::{AsyncRead, AsyncWrite, AsyncSeek, AsyncBufRead}; #[cfg(feature = "std")] #[doc(hidden)] pub use futures_util::{AsyncReadExt, AsyncWriteExt, AsyncSeekExt, AsyncBufReadExt}; #[doc(hidden)] pub use futures_core::task::Poll; #[doc(hidden)] pub use futures_util::never::Never; // Macro reexports pub use futures_core::ready; // Readiness propagation pub use futures_util::pin_mut; #[cfg(feature = "std")] #[cfg(feature = "async-await")] pub use futures_util::{pending, poll}; // Async-await #[cfg_attr( feature = "cfg-target-has-atomic", cfg(all(target_has_atomic = "cas", target_has_atomic = "ptr")) )] #[cfg(feature = "alloc")] pub mod channel { //! Cross-task communication. //! //! Like threads, concurrent tasks sometimes need to communicate with each //! other. This module contains two basic abstractions for doing so: //! //! - [oneshot](crate::channel::oneshot), a way of sending a single value //! from one task to another. //! - [mpsc](crate::channel::mpsc), a multi-producer, single-consumer //! channel for sending values between tasks, analogous to the //! similarly-named structure in the standard library. //! //! This module is only available when the `std` or `alloc` feature of this //! library is activated, and it is activated by default. pub use futures_channel::oneshot; #[cfg(feature = "std")] pub use futures_channel::mpsc; } #[cfg(feature = "compat")] pub mod compat { //! Interop between `futures` 0.1 and 0.3. //! //! This module is only available when the `compat` feature of this //! library is activated. pub use futures_util::compat::{ Compat, CompatSink, Compat01As03, Compat01As03Sink, Executor01Future, Executor01As03, Executor01CompatExt, Future01CompatExt, Stream01CompatExt, Sink01CompatExt, }; #[cfg(feature = "io-compat")] pub use futures_util::compat::{ AsyncRead01CompatExt, AsyncWrite01CompatExt, }; } #[cfg(feature = "std")] pub mod executor { //! Task execution. //! //! All asynchronous computation occurs within an executor, which is //! capable of spawning futures as tasks. This module provides several //! built-in executors, as well as tools for building your own. //! //! This module is only available when the `std` feature of this //! library is activated, and it is activated by default. //! //! # Using a thread pool (M:N task scheduling) //! //! Most of the time tasks should be executed on a [thread //! pool](crate::executor::ThreadPool). A small set of worker threads can //! handle a very large set of spawned tasks (which are much lighter weight //! than threads). //! //! The simplest way to use a thread pool is to //! [`run`](crate::executor::ThreadPool::run) an initial task on it, which //! can then spawn further tasks back onto the pool to complete its work: //! //! ``` //! use futures::executor::ThreadPool; //! # use futures::future::lazy; //! # let my_app = lazy(|_| 42); //! //! // assuming `my_app: Future` //! ThreadPool::new().expect("Failed to create threadpool").run(my_app); //! ``` //! //! The call to [`run`](crate::executor::ThreadPool::run) will block the //! current thread until the future defined by `my_app` completes, and will //! return the result of that future. //! //! # Spawning additional tasks //! //! Tasks can be spawned onto a spawner by calling its //! [`spawn_obj`](crate::task::Spawn::spawn_obj) method directly. //! In the case of `!Send` futures, //! [`spawn_local_obj`](crate::task::LocalSpawn::spawn_local_obj) //! can be used instead. //! //! # Single-threaded execution //! //! In addition to thread pools, it's possible to run a task (and the tasks //! it spawns) entirely within a single thread via the //! [`LocalPool`](crate::executor::LocalPool) executor. Aside from cutting //! down on synchronization costs, this executor also makes it possible to //! spawn non-`Send` tasks, via //! [`spawn_local_obj`](crate::task::LocalSpawn::spawn_local_obj). //! The `LocalPool` is best suited for running I/O-bound tasks that do //! relatively little work between I/O operations. //! //! There is also a convenience function, //! [`block_on`](crate::executor::block_on), for simply running a future to //! completion on the current thread, while routing any spawned tasks //! to a global thread pool. pub use futures_executor::{ BlockingStream, Enter, EnterError, LocalSpawner, LocalPool, ThreadPool, ThreadPoolBuilder, block_on, block_on_stream, enter, }; } pub mod future { //! Asynchronous values. //! //! This module contains: //! //! - The [`Future` trait](crate::future::Future). //! - The [`FutureExt`](crate::future::FutureExt) trait, which provides //! adapters for chaining and composing futures. //! - Top-level future combinators like [`lazy`](crate::future::lazy) which //! creates a future from a closure that defines its return value, and //! [`ready`](crate::future::ready), which constructs a future with an //! immediate defined value. pub use futures_core::future::{ Future, TryFuture, FusedFuture, FutureObj, LocalFutureObj, UnsafeFutureObj, }; #[cfg(feature = "alloc")] pub use futures_core::future::{BoxFuture, LocalBoxFuture}; pub use futures_util::future::{ lazy, Lazy, maybe_done, MaybeDone, pending, Pending, poll_fn, PollFn, ready, ok, err, Ready, select, Select, join, join3, join4, join5, Join, Join3, Join4, Join5, Either, OptionFuture, FutureExt, FlattenStream, Flatten, Fuse, Inspect, IntoStream, Map, Then, UnitError, NeverError, }; #[cfg(feature = "alloc")] pub use futures_util::future::{ join_all, JoinAll, select_all, SelectAll, }; #[cfg_attr( feature = "cfg-target-has-atomic", cfg(all(target_has_atomic = "cas", target_has_atomic = "ptr")) )] #[cfg(feature = "alloc")] pub use futures_util::future::{ abortable, Abortable, AbortHandle, AbortRegistration, Aborted, }; #[cfg(feature = "std")] pub use futures_util::future::{ Remote, RemoteHandle, // For FutureExt: CatchUnwind, Shared, }; pub use futures_util::try_future::{ try_join, try_join3, try_join4, try_join5, TryJoin, TryJoin3, TryJoin4, TryJoin5, try_select, TrySelect, TryFutureExt, AndThen, ErrInto, FlattenSink, IntoFuture, MapErr, MapOk, OrElse, InspectOk, InspectErr, TryFlattenStream, UnwrapOrElse, }; #[cfg(feature = "alloc")] pub use futures_util::try_future::{ try_join_all, TryJoinAll, select_ok, SelectOk, }; } #[cfg(feature = "std")] pub mod io { //! Asynchronous I/O. //! //! This module is the asynchronous version of `std::io`. It defines four //! traits, [`AsyncRead`](crate::io::AsyncRead), //! [`AsyncWrite`](crate::io::AsyncWrite), //! [`AsyncSeek`](crate::io::AsyncSeek), and //! [`AsyncBufRead`](crate::io::AsyncBufRead), which mirror the `Read`, //! `Write`, `Seek`, and `BufRead` traits of the standard library. However, //! these traits integrate //! with the asynchronous task system, so that if an I/O object isn't ready //! for reading (or writing), the thread is not blocked, and instead the //! current task is queued to be woken when I/O is ready. //! //! In addition, the [`AsyncReadExt`](crate::io::AsyncReadExt), //! [`AsyncWriteExt`](crate::io::AsyncWriteExt), //! [`AsyncSeekExt`](crate::io::AsyncSeekExt), and //! [`AsyncBufReadExt`](crate::io::AsyncBufReadExt) extension traits offer a //! variety of useful combinators for operating with asynchronous I/O //! objects, including ways to work with them using futures, streams and //! sinks. //! //! This module is only available when the `std` feature of this //! library is activated, and it is activated by default. pub use futures_io::{ AsyncRead, AsyncWrite, AsyncSeek, AsyncBufRead, Error, ErrorKind, IoSlice, IoSliceMut, Result, SeekFrom, }; #[cfg(feature = "read_initializer")] pub use futures_io::Initializer; pub use futures_util::io::{ AsyncReadExt, AsyncWriteExt, AsyncSeekExt, AsyncBufReadExt, AllowStdIo, BufReader, BufWriter, Chain, Close, CopyInto, CopyBufInto, empty, Empty, Flush, IntoSink, Lines, Read, ReadExact, ReadHalf, ReadLine, ReadToEnd, ReadToString, ReadUntil, ReadVectored, repeat, Repeat, Seek, sink, Sink, Take, Window, Write, WriteAll, WriteHalf, WriteVectored, }; } #[cfg_attr( feature = "cfg-target-has-atomic", cfg(all(target_has_atomic = "cas", target_has_atomic = "ptr")) )] #[cfg(feature = "alloc")] pub mod lock { //! Futures-powered synchronization primitives. //! //! This module is only available when the `std` or `alloc` feature of this //! library is activated, and it is activated by default. #[cfg(feature = "bilock")] pub use futures_util::lock::{BiLock, BiLockAcquire, BiLockGuard, ReuniteError}; #[cfg(feature = "std")] pub use futures_util::lock::{Mutex, MutexLockFuture, MutexGuard}; } pub mod prelude { //! A "prelude" for crates using the `futures` crate. //! //! This prelude is similar to the standard library's prelude in that you'll //! almost always want to import its entire contents, but unlike the //! standard library's prelude you'll have to do so manually: //! //! ``` //! # #[allow(unused_imports)] //! use futures::prelude::*; //! ``` //! //! The prelude may grow over time as additional items see ubiquitous use. pub use crate::future::{self, Future, TryFuture}; pub use crate::stream::{self, Stream, TryStream}; pub use crate::sink::{self, Sink}; #[doc(no_inline)] pub use crate::future::{FutureExt as _, TryFutureExt as _}; #[doc(no_inline)] pub use crate::stream::{StreamExt as _, TryStreamExt as _}; #[doc(no_inline)] pub use crate::sink::SinkExt as _; #[cfg(feature = "std")] pub use crate::io::{ AsyncRead, AsyncWrite, AsyncSeek, AsyncBufRead, }; #[cfg(feature = "std")] #[doc(no_inline)] pub use crate::io::{ AsyncReadExt as _, AsyncWriteExt as _, AsyncSeekExt as _, AsyncBufReadExt as _, }; } pub mod sink { //! Asynchronous sinks. //! //! This module contains: //! //! - The [`Sink` trait](crate::sink::Sink), which allows you to //! asynchronously write data. //! - The [`SinkExt`](crate::sink::SinkExt) trait, which provides adapters //! for chaining and composing sinks. pub use futures_sink::Sink; pub use futures_util::sink::{ Close, Flush, Send, SendAll, SinkErrInto, SinkMapErr, With, SinkExt, Fanout, Drain, drain, WithFlatMap, }; #[cfg(feature = "alloc")] pub use futures_util::sink::Buffer; } pub mod stream { //! Asynchronous streams. //! //! This module contains: //! //! - The [`Stream` trait](crate::stream::Stream), for objects that can //! asynchronously produce a sequence of values. //! - The [`StreamExt`](crate::stream::StreamExt) trait, which provides //! adapters for chaining and composing streams. //! - Top-level stream contructors like [`iter`](crate::stream::iter) //! which creates a stream from an iterator. pub use futures_core::stream::{ Stream, TryStream, FusedStream, }; #[cfg(feature = "alloc")] pub use futures_core::stream::{BoxStream, LocalBoxStream}; pub use futures_util::stream::{ iter, Iter, repeat, Repeat, empty, Empty, pending, Pending, once, Once, poll_fn, PollFn, select, Select, unfold, Unfold, StreamExt, Chain, Collect, Concat, Enumerate, Filter, FilterMap, Flatten, Fold, Forward, ForEach, Fuse, StreamFuture, Inspect, Map, Next, SelectNextSome, Peekable, Skip, SkipWhile, Take, TakeWhile, Then, Zip }; #[cfg(feature = "alloc")] pub use futures_util::stream::{ // For StreamExt: Chunks, }; #[cfg_attr( feature = "cfg-target-has-atomic", cfg(all(target_has_atomic = "cas", target_has_atomic = "ptr")) )] #[cfg(feature = "alloc")] pub use futures_util::stream::{ FuturesOrdered, futures_unordered, FuturesUnordered, // For StreamExt: BufferUnordered, Buffered, ForEachConcurrent, SplitStream, SplitSink, ReuniteError, select_all, SelectAll, }; #[cfg(feature = "std")] pub use futures_util::stream::{ // For StreamExt: CatchUnwind, }; pub use futures_util::try_stream::{ TryStreamExt, AndThen, ErrInto, MapOk, MapErr, OrElse, InspectOk, InspectErr, TryNext, TryForEach, TryFilter, TryFilterMap, TryFlatten, TryCollect, TryConcat, TryFold, TrySkipWhile, IntoStream, }; #[cfg_attr( feature = "cfg-target-has-atomic", cfg(all(target_has_atomic = "cas", target_has_atomic = "ptr")) )] #[cfg(feature = "alloc")] pub use futures_util::try_stream::{ // For TryStreamExt: TryBufferUnordered, TryForEachConcurrent, }; #[cfg(feature = "std")] pub use futures_util::try_stream::IntoAsyncRead; } pub mod task { //! Tools for working with tasks. //! //! This module contains: //! //! - [`Spawn`](crate::task::Spawn), a trait for spawning new tasks. //! - [`Context`](crate::task::Context), a context of an asynchronous task, //! including a handle for waking up the task. //! - [`Waker`](crate::task::Waker), a handle for waking up a task. //! //! The remaining types and traits in the module are used for implementing //! executors or dealing with synchronization issues around task wakeup. pub use futures_core::task::{ Context, Poll, Spawn, LocalSpawn, SpawnError, Waker, RawWaker, RawWakerVTable }; pub use futures_util::task::noop_waker; #[cfg(feature = "std")] pub use futures_util::task::noop_waker_ref; #[cfg(feature = "alloc")] pub use futures_util::task::{SpawnExt, LocalSpawnExt}; #[cfg_attr( feature = "cfg-target-has-atomic", cfg(all(target_has_atomic = "cas", target_has_atomic = "ptr")) )] #[cfg(feature = "alloc")] pub use futures_util::task::{waker, waker_ref, WakerRef, ArcWake}; #[cfg_attr( feature = "cfg-target-has-atomic", cfg(all(target_has_atomic = "cas", target_has_atomic = "ptr")) )] pub use futures_util::task::AtomicWaker; } pub mod never { //! This module contains the `Never` type. //! //! Values of this type can never be created and will never exist. pub use futures_util::never::Never; } // proc-macro re-export -------------------------------------- #[cfg(feature = "std")] #[cfg(feature = "async-await")] #[doc(hidden)] pub use futures_util::async_await; #[cfg(feature = "std")] #[cfg(feature = "async-await")] #[doc(hidden)] pub mod inner_macro { pub use futures_util::join; pub use futures_util::try_join; pub use futures_util::select; } #[cfg(feature = "std")] #[cfg(feature = "async-await")] futures_util::document_join_macro! { #[macro_export] macro_rules! join { // replace `::futures_util` with `::futures` as the crate path ($($tokens:tt)*) => { $crate::inner_macro::join! { futures_crate_path ( ::futures ) $( $tokens )* } } } #[macro_export] macro_rules! try_join { // replace `::futures_util` with `::futures` as the crate path ($($tokens:tt)*) => { $crate::inner_macro::try_join! { futures_crate_path ( ::futures ) $( $tokens )* } } } } #[cfg(feature = "std")] #[cfg(feature = "async-await")] futures_util::document_select_macro! { #[macro_export] macro_rules! select { // replace `::futures_util` with `::futures` as the crate path ($($tokens:tt)*) => { $crate::inner_macro::select! { futures_crate_path ( ::futures ) $( $tokens )* } } } }