diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml index 016498b..9c4f0e2 100644 --- a/.github/workflows/ci.yml +++ b/.github/workflows/ci.yml @@ -37,8 +37,8 @@ jobs: - name: Run cargo check (without dev-dependencies to catch missing feature flags) if: startsWith(matrix.rust, 'nightly') run: cargo check -Z features=dev_dep - - run: cargo test --features __test - - run: cargo build --no-default-features + - run: cargo test --features __test --all + - run: cargo build --no-default-features --all - name: Install cargo-hack uses: taiki-e/install-action@cargo-hack - run: rustup target add thumbv7m-none-eabi @@ -55,7 +55,7 @@ jobs: - uses: actions/checkout@v3 - name: Install Rust run: rustup update ${{ matrix.rust }} && rustup default ${{ matrix.rust }} - - run: cargo build + - run: cargo build --all clippy: runs-on: ubuntu-latest @@ -63,7 +63,7 @@ jobs: - uses: actions/checkout@v3 - name: Install Rust run: rustup update stable - - run: cargo clippy --all-features --all-targets + - run: cargo clippy --all --all-features --all-targets fmt: runs-on: ubuntu-latest @@ -79,7 +79,7 @@ jobs: - uses: actions/checkout@v3 - name: Install Rust run: rustup toolchain install nightly --component miri && rustup default nightly - - run: cargo miri test --features __test + - run: cargo miri test --features __test --all env: MIRIFLAGS: -Zmiri-strict-provenance -Zmiri-symbolic-alignment-check -Zmiri-disable-isolation RUSTFLAGS: ${{ env.RUSTFLAGS }} -Z randomize-layout diff --git a/Cargo.toml b/Cargo.toml index dfffc9c..f601937 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -40,3 +40,6 @@ harness = false [lib] bench = false + +[workspace] +members = ["strategy"] diff --git a/strategy/Cargo.toml b/strategy/Cargo.toml new file mode 100644 index 0000000..fba9632 --- /dev/null +++ b/strategy/Cargo.toml @@ -0,0 +1,28 @@ +[package] +name = "event-listener-strategy" +version = "0.1.0" +edition = "2018" +authors = ["John Nunley "] +rust-version = "1.39" +description = "Block or poll on event_listener easily" +license = "Apache-2.0 OR MIT" +repository = "https://github.com/smol-rs/event-listener" +keywords = ["condvar", "envcount", "wake", "blocking", "park"] +categories = ["asynchronous", "concurrency"] +exclude = ["/.*"] + +[dependencies] +event-listener = { path = "..", version = "2", default-features = false } +pin-project-lite = "0.2.9" +pin-utils = "0.1.0" + +[features] +default = ["std"] +std = ["event-listener/std"] + +[dev-dependencies] +futures-lite = "1.12.0" + +[package.metadata.docs.rs] +all-features = true +rustdoc-args = ["--cfg", "docsrs"] diff --git a/strategy/LICENSE-APACHE b/strategy/LICENSE-APACHE new file mode 100644 index 0000000..16fe87b --- /dev/null +++ b/strategy/LICENSE-APACHE @@ -0,0 +1,201 @@ + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + +TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + +1. 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IN NO EVENT +SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY +CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION +OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR +IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +DEALINGS IN THE SOFTWARE. diff --git a/strategy/src/lib.rs b/strategy/src/lib.rs new file mode 100644 index 0000000..756b59e --- /dev/null +++ b/strategy/src/lib.rs @@ -0,0 +1,427 @@ +// SPDX-Licenser-Identifier: MIT OR Apache-2.0 +//! A strategy for using the [`event-listener`] crate in both blocking and non-blocking contexts. +//! +//! One of the stand-out features of the [`event-listener`] crate is the ability to use it in both +//! asynchronous and synchronous contexts. However, sometimes using it like this causes a lot of +//! boilerplate to be duplicated. This crate aims to reduce that boilerplate by providing an +//! [`EventListenerFuture`] trait that implements both blocking and non-blocking functionality. +//! +//! # Examples +//! +//! ``` +//! use event_listener::{Event, EventListener}; +//! use event_listener_strategy::{EventListenerFuture, FutureWrapper, Strategy}; +//! +//! use std::pin::Pin; +//! use std::task::Poll; +//! use std::thread; +//! use std::sync::Arc; +//! +//! // A future that waits three seconds for an event to be fired. +//! fn wait_three_seconds() -> WaitThreeSeconds { +//! let event = Event::new(); +//! let listener = event.listen(); +//! +//! thread::spawn(move || { +//! thread::sleep(std::time::Duration::from_secs(3)); +//! event.notify(1); +//! }); +//! +//! WaitThreeSeconds { listener: Some(listener) } +//! } +//! +//! struct WaitThreeSeconds { +//! listener: Option, +//! } +//! +//! impl EventListenerFuture for WaitThreeSeconds { +//! type Output = (); +//! +//! fn poll_with_strategy( +//! mut self: Pin<&mut Self>, +//! strategy: &mut S, +//! context: &mut S::Context, +//! ) -> Poll { +//! match strategy.poll(self.listener.take().unwrap(), context) { +//! Ok(()) => Poll::Ready(()), +//! Err(listener) => { +//! self.listener = Some(listener); +//! Poll::Pending +//! } +//! } +//! } +//! } +//! +//! // Use the future in a blocking context. +//! let future = wait_three_seconds(); +//! future.wait(); +//! +//! // Use the future in a non-blocking context. +//! futures_lite::future::block_on(async { +//! let future = FutureWrapper::new(wait_three_seconds()); +//! future.await; +//! }); +//! ``` + +#![cfg_attr(not(feature = "std"), no_std)] +#![cfg_attr(docsrs, feature(doc_cfg))] +#![forbid(future_incompatible, missing_docs)] + +use core::future::Future; +use core::marker::PhantomData; +use core::pin::Pin; +use core::task::{Context, Poll}; + +use event_listener::EventListener; + +#[doc(hidden)] +pub use pin_project_lite::pin_project; + +/// A wrapper around an [`EventListenerFuture`] that can be easily exported for use. +/// +/// This type implements [`Future`], has a `_new()` constructor, and a `wait()` method +/// that uses the [`Blocking`] strategy to poll the future until it is ready. +/// +/// # Examples +/// +/// ``` +/// mod my_future { +/// use event_listener_strategy::{easy_wrapper, EventListenerFuture, Strategy}; +/// use std::pin::Pin; +/// use std::task::Poll; +/// +/// struct MyFuture; +/// +/// impl EventListenerFuture for MyFuture { +/// type Output = (); +/// +/// fn poll_with_strategy( +/// self: Pin<&mut Self>, +/// strategy: &mut S, +/// context: &mut S::Context, +/// ) -> Poll { +/// /* ... */ +/// # Poll::Ready(()) +/// } +/// } +/// +/// easy_wrapper! { +/// /// A future that does something. +/// pub struct MyFutureWrapper(MyFuture => ()); +/// /// Wait for it. +/// pub wait(); +/// } +/// +/// impl MyFutureWrapper { +/// /// Create a new instance of the future. +/// pub fn new() -> Self { +/// Self::_new(MyFuture) +/// } +/// } +/// } +/// +/// use my_future::MyFutureWrapper; +/// +/// // Use the future in a blocking context. +/// let future = MyFutureWrapper::new(); +/// future.wait(); +/// +/// // Use the future in a non-blocking context. +/// futures_lite::future::block_on(async { +/// let future = MyFutureWrapper::new(); +/// future.await; +/// }); +/// ``` +#[macro_export] +macro_rules! easy_wrapper { + ( + $(#[$meta:meta])* + $vis:vis struct $name:ident ($inner:ty => $output:ty); + $(#[$wait_meta:meta])* + $wait_vis: vis wait(); + ) => { + $crate::pin_project! { + $(#[$meta])* + $vis struct $name { + #[pin] + _inner: $crate::FutureWrapper<$inner> + } + } + + impl $name { + #[inline] + fn _new(inner: $inner) -> Self { + Self { + _inner: $crate::FutureWrapper::new(inner) + } + } + + $(#[$wait_meta])* + #[inline] + $wait_vis fn wait(self) -> $output { + use $crate::EventListenerFuture; + self._inner.into_inner().wait() + } + } + + impl ::core::future::Future for $name { + type Output = $output; + + #[inline] + fn poll( + self: ::core::pin::Pin<&mut Self>, + context: &mut ::core::task::Context<'_> + ) -> ::core::task::Poll { + self.project()._inner.poll(context) + } + } + }; +} + +/// A future that runs using the [`event-listener`] crate. +/// +/// This is similar to the [`Future`] trait from libstd, with one notable difference: it takes +/// a strategy that tells it whether to operate in a blocking or non-blocking context. The +/// `poll_with_strategy` method is the equivalent of the `poll` method in this regard; it uses +/// the [`Strategy`] trait to determine how to poll the future. +/// +/// From here, there are two additional things one can do with this trait: +/// +/// - The `wait` method, which uses the [`Blocking`] strategy to poll the future until it is +/// ready, blocking the current thread until it is. +/// - The [`FutureWrapper`] type, which implements [`Future`] and uses the [`NonBlocking`] +/// strategy to poll the future. +pub trait EventListenerFuture { + /// The type of value produced on completion. + type Output; + + /// Poll the future using the provided strategy. + /// + /// This function should use the `Strategy::poll` method to poll the future, and proceed + /// based on the result. + fn poll_with_strategy( + self: Pin<&mut Self>, + strategy: &mut S, + context: &mut S::Context, + ) -> Poll; + + /// Wait for the future to complete, blocking the current thread. + /// + /// This function uses the [`Blocking`] strategy to poll the future until it is ready. + /// + /// The future should only return `Pending` if `Strategy::poll` returns error. Otherwise, + /// this function polls the future in a hot loop. + #[cfg(feature = "std")] + #[cfg_attr(docsrs, doc(cfg(feature = "std")))] + fn wait(mut self) -> Self::Output + where + Self: Sized, + { + // SAFETY: `self`/`this` is not moved out after this. + let mut this = unsafe { Pin::new_unchecked(&mut self) }; + + loop { + if let Poll::Ready(res) = this + .as_mut() + .poll_with_strategy(&mut Blocking::default(), &mut ()) + { + return res; + } + } + } +} + +pin_project_lite::pin_project! { + /// A wrapper around an [`EventListenerFuture`] that implements [`Future`]. + /// + /// [`Future`]: core::future::Future + #[derive(Debug, Clone)] + pub struct FutureWrapper { + #[pin] + inner: F, + } +} + +impl FutureWrapper { + /// Create a new `FutureWrapper` from the provided future. + #[inline] + pub fn new(inner: F) -> Self { + Self { inner } + } + + /// Consume the `FutureWrapper`, returning the inner future. + #[inline] + pub fn into_inner(self) -> F { + self.inner + } +} + +impl FutureWrapper { + /// Get a reference to the inner future. + #[inline] + pub fn get_ref(&self) -> &F { + &self.inner + } + + /// Get a mutable reference to the inner future. + #[inline] + pub fn get_mut(&mut self) -> &mut F { + &mut self.inner + } + + /// Get a pinned mutable reference to the inner future. + #[inline] + pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut F> { + self.project().inner + } + + /// Get a pinned reference to the inner future. + #[inline] + pub fn get_pin_ref(self: Pin<&Self>) -> Pin<&F> { + self.project_ref().inner + } +} + +impl From for FutureWrapper { + #[inline] + fn from(inner: F) -> Self { + Self { inner } + } +} + +impl Future for FutureWrapper { + type Output = F::Output; + + #[inline] + fn poll(self: Pin<&mut Self>, context: &mut Context<'_>) -> Poll { + self.project() + .inner + .poll_with_strategy(&mut NonBlocking::default(), context) + } +} + +/// A strategy for polling an [`EventListenerFuture`] or an [`EventListener`]. +/// +/// This trait is used by the [`EventListenerFuture::poll_with_strategy`] method to determine +/// how to poll the future. It can also be used standalone, by calling the [`Strategy::wait`] +/// method. +/// +/// [`EventListenerFuture::poll_with_strategy`]: EventListenerFuture::poll_with_strategy +/// [`EventListener`]: event_listener::EventListener +/// +/// # Examples +/// +/// ``` +/// use event_listener::{Event, EventListener}; +/// use event_listener_strategy::{EventListenerFuture, Strategy, Blocking, NonBlocking}; +/// +/// async fn wait_on(evl: EventListener, strategy: &mut S) { +/// strategy.wait(evl).await; +/// } +/// +/// # futures_lite::future::block_on(async { +/// // Block on the future. +/// let ev = Event::new(); +/// let listener = ev.listen(); +/// ev.notify(1); +/// +/// wait_on(listener, &mut Blocking::default()).await; +/// +/// // Poll the future. +/// let listener = ev.listen(); +/// ev.notify(1); +/// +/// wait_on(listener, &mut NonBlocking::default()).await; +/// # }); +/// ``` +pub trait Strategy { + /// The context needed to poll the future. + type Context: ?Sized; + + /// The future returned by the [`Strategy::wait`] method. + type Future: Future; + + /// Poll the event listener until it is ready. + fn poll( + &mut self, + event_listener: EventListener, + context: &mut Self::Context, + ) -> Result<(), EventListener>; + + /// Wait for the event listener to become ready. + fn wait(&mut self, evl: EventListener) -> Self::Future; +} + +/// A strategy that uses polling to efficiently wait for an event. +#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)] +pub struct NonBlocking<'a> { + _marker: PhantomData>, +} + +impl<'a> Strategy for NonBlocking<'a> { + type Context = Context<'a>; + type Future = EventListener; + + #[inline] + fn wait(&mut self, evl: EventListener) -> Self::Future { + evl + } + + #[inline] + fn poll( + &mut self, + mut event_listener: EventListener, + context: &mut Self::Context, + ) -> Result<(), EventListener> { + match Pin::new(&mut event_listener).poll(context) { + Poll::Ready(()) => Ok(()), + Poll::Pending => Err(event_listener), + } + } +} + +/// A strategy that blocks the current thread until the event is signalled. +#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)] +#[cfg(feature = "std")] +pub struct Blocking { + _private: (), +} + +#[cfg(feature = "std")] +impl Strategy for Blocking { + type Context = (); + type Future = Ready; + + #[inline] + fn wait(&mut self, evl: EventListener) -> Self::Future { + evl.wait(); + Ready { _private: () } + } + + #[inline] + fn poll( + &mut self, + event_listener: EventListener, + _context: &mut Self::Context, + ) -> Result<(), EventListener> { + event_listener.wait(); + Ok(()) + } +} + +/// A future that is always ready. +#[cfg(feature = "std")] +#[doc(hidden)] +#[derive(Debug, Clone)] +pub struct Ready { + _private: (), +} + +impl Future for Ready { + type Output = (); + + #[inline] + fn poll(self: Pin<&mut Self>, _context: &mut Context<'_>) -> Poll { + Poll::Ready(()) + } +}