port futures 0.3 to std futures

Cargo.toml

@@ -9,6 +9,5 @@ members = [
 #  "futures-macro-async",
 #  "futures-macro-await",
   "futures-sink",
-#  "futures-stable",
   "futures-util",
 ]

futures-channel/src/lib.rs

@@ -3,7 +3,7 @@
 //! This crate provides channels that can be used to communicate between
 //! asynchronous tasks.
 
-#![feature(pin, arbitrary_self_types)]
+#![feature(pin, arbitrary_self_types, futures_api)]
 
 #![deny(missing_docs, missing_debug_implementations)]
 #![doc(html_root_url = "https://docs.rs/futures-channel/0.2.0")]

futures-core/src/executor.rs

@@ -1,61 +1,4 @@
 //! Executors.
 
-use task::TaskObj;
+pub use core::task::{Executor, SpawnErrorKind, SpawnObjError};
 
-/// A task executor.
-///
-/// A *task* is a `()`-producing future that runs at the top level, and will
-/// be `poll`ed until completion. It's also the unit at which wake-up
-/// notifications occur. Executors, such as thread pools, allow tasks to be
-/// spawned and are responsible for putting tasks onto ready queues when
-/// they are woken up, and polling them when they are ready.
-pub trait Executor {
-    /// Spawn the given task object, polling it until completion.
-    ///
-    /// # Errors
-    ///
-    /// The executor may be unable to spawn tasks, either because it has
-    /// been shut down or is resource-constrained.
-    fn spawn_obj(&mut self, task: TaskObj) -> Result<(), SpawnObjError>;
-
-    /// Determine whether the executor is able to spawn new tasks.
-    ///
-    /// # Returns
-    ///
-    /// An `Ok` return means the executor is *likely* (but not guaranteed)
-    /// to accept a subsequent spawn attempt. Likewise, an `Err` return
-    /// means that `spawn` is likely, but not guaranteed, to yield an error.
-    fn status(&self) -> Result<(), SpawnErrorKind> {
-        Ok(())
-    }
-
-    // TODO: downcasting hooks
-}
-
-/// Provides the reason that an executor was unable to spawn.
-#[derive(Debug)]
-pub struct SpawnErrorKind {
-    _a: ()
-}
-
-impl SpawnErrorKind {
-    /// Spawning is failing because the executor has been shut down.
-    pub fn shutdown() -> SpawnErrorKind {
-        SpawnErrorKind { _a: () }
-    }
-
-    /// Check whether this error is the `shutdown` error.
-    pub fn is_shutdown() -> bool {
-        true
-    }
-}
-
-/// The result of a failed spawn
-#[derive(Debug)]
-pub struct SpawnObjError {
-    /// The kind of error
-    pub kind: SpawnErrorKind,
-
-    /// The task for which spawning was attempted
-    pub task: TaskObj,
-}

futures-core/src/future/either.rs

@@ -1,24 +1,24 @@
-use {task, Future, Stream, Poll};
+use {task, Stream, Poll};
 
 use core::mem::PinMut;
 
 use either::Either;
 
-impl<A, B> Future for Either<A, B>
-    where A: Future,
-          B: Future<Output = A::Output>
-{
-    type Output = A::Output;
+// impl<A, B> Future for Either<A, B>
+//     where A: Future,
+//           B: Future<Output = A::Output>
+// {
+//     type Output = A::Output;
 
-    fn poll(self: PinMut<Self>, cx: &mut task::Context) -> Poll<A::Output> {
-        unsafe {
-            match PinMut::get_mut(self) {
-                Either::Left(a) => PinMut::new_unchecked(a).poll(cx),
-                Either::Right(b) => PinMut::new_unchecked(b).poll(cx),
-            }
-        }
-    }
-}
+//     fn poll(self: PinMut<Self>, cx: &mut task::Context) -> Poll<A::Output> {
+//         unsafe {
+//             match PinMut::get_mut(self) {
+//                 Either::Left(a) => PinMut::new_unchecked(a).poll(cx),
+//                 Either::Right(b) => PinMut::new_unchecked(b).poll(cx),
+//             }
+//         }
+//     }
+// }
 
 impl<A, B> Stream for Either<A, B>
     where A: Stream,

futures-core/src/future/mod.rs

@@ -12,106 +12,10 @@ pub use self::option::FutureOption;
 #[cfg(feature = "either")]
 mod either;
 
-/// A future represents an asychronous computation.
-///
-/// A future is a value that may not have finished computing yet. This kind of
-/// "asynchronous value" makes it possible for a thread to continue doing useful
-/// work while it waits for the value to become available.
-///
-/// The ergonomics and implementation of the `Future` trait are very similar to
-/// the `Iterator` trait in that there is just one method you need to
-/// implement, but you get a whole lot of others for free as a result. These
-/// other methods allow you to chain together large computations based on
-/// futures, which will automatically handle asynchrony for you.
-///
-/// # The `poll` method
-///
-/// The core method of future, `poll`, *attempts* to resolve the future into a
-/// final value. This method does not block if the value is not ready. Instead,
-/// the current task is scheduled to be woken up when it's possible to make
-/// further progress by `poll`ing again. The wake up is performed using
-/// `cx.waker()`, a handle for waking up the current task.
-///
-/// When using a future, you generally won't call `poll` directly, but instead
-/// use combinators to build up asynchronous computations. A complete
-/// computation can then be spawned onto an
-/// [executor](../futures_core/executor/trait.Executor.html) as a new, independent
-/// task that will automatically be `poll`ed to completion.
-///
-/// # Combinators
-///
-/// Like iterators, futures provide a large number of combinators to work with
-/// futures to express computations in a much more natural method than
-/// scheduling a number of callbacks. As with iterators, the combinators are
-/// zero-cost: they compile away. You can find the combinators in the
-/// [future-util](https://docs.rs/futures-util) crate.
-pub trait Future {
-    /// The result of the future
-    type Output;
-
-    /// Attempt to resolve the future to a final value, registering
-    /// the current task for wakeup if the value is not yet available.
-    ///
-    /// # Return value
-    ///
-    /// This function returns:
-    ///
-    /// - `Poll::Pending` if the future is not ready yet
-    /// - `Poll::Ready(val)` with the result `val` of this future if it finished
-    /// successfully.
-    ///
-    /// Once a future has finished, clients should not `poll` it again.
-    ///
-    /// When a future is not ready yet, `poll` returns
-    /// [`Poll::Pending`](::Poll). The future will *also* register the
-    /// interest of the current task in the value being produced. For example,
-    /// if the future represents the availability of data on a socket, then the
-    /// task is recorded so that when data arrives, it is woken up (via
-    /// [`cx.waker()`](::task::Context::waker). Once a task has been woken up,
-    /// it should attempt to `poll` the future again, which may or may not
-    /// produce a final value.
-    ///
-    /// Note that if `Pending` is returned it only means that the *current* task
-    /// (represented by the argument `cx`) will receive a notification. Tasks
-    /// from previous calls to `poll` will *not* receive notifications.
-    ///
-    /// # Runtime characteristics
-    ///
-    /// Futures alone are *inert*; they must be *actively* `poll`ed to make
-    /// progress, meaning that each time the current task is woken up, it should
-    /// actively re-`poll` pending futures that it still has an interest in.
-    /// Usually this is done by building up a large computation as a single
-    /// future (using combinators), then spawning that future as a *task* onto
-    /// an [executor](../futures_core/executor/trait.Executor.html). Executors
-    /// ensure that each task is `poll`ed every time a future internal to that
-    /// task is ready to make progress.
-    ///
-    /// The `poll` function is not called repeatedly in a tight loop for
-    /// futures, but only whenever the future itself is ready, as signaled via
-    /// [`cx.waker()`](::task::Context::waker). If you're familiar with the
-    /// `poll(2)` or `select(2)` syscalls on Unix it's worth noting that futures
-    /// typically do *not* suffer the same problems of "all wakeups must poll
-    /// all events"; they are more like `epoll(4)`.
-    ///
-    /// An implementation of `poll` should strive to return quickly, and must
-    /// *never* block. Returning quickly prevents unnecessarily clogging up
-    /// threads or event loops. If it is known ahead of time that a call to
-    /// `poll` may end up taking awhile, the work should be offloaded to a
-    /// thread pool (or something similar) to ensure that `poll` can return
-    /// quickly.
-    ///
-    /// # Panics
-    ///
-    /// Once a future has completed (returned `Ready` from `poll`),
-    /// then any future calls to `poll` may panic, block forever, or otherwise
-    /// cause bad behavior. The `Future` trait itself provides no guarantees
-    /// about the behavior of `poll` after a future has completed.
-    ///
-    /// Callers who may call `poll` too many times may want to consider using
-    /// the `fuse` adaptor which defines the behavior of `poll`, but comes with
-    /// a little bit of extra cost.
-    fn poll(self: PinMut<Self>, cx: &mut task::Context) -> Poll<Self::Output>;
+pub use core::future::Future;
 
+/// Will probably merge with futures_util::FutureExt
+pub trait CoreFutureExt: Future {
     /// A convenience for calling `Future::poll` on `Unpin` future types.
     fn poll_unpin(&mut self, cx: &mut task::Context) -> Poll<Self::Output>
         where Self: Unpin
@@ -120,50 +24,8 @@ pub trait Future {
     }
 }
 
-impl<'a, F: ?Sized + Future + Unpin> Future for &'a mut F {
-    type Output = F::Output;
-
-    fn poll(mut self: PinMut<Self>, cx: &mut task::Context) -> Poll<Self::Output> {
-        F::poll(PinMut::new(&mut **self), cx)
-    }
-}
-
-impl<'a, F: ?Sized + Future> Future for PinMut<'a, F> {
-    type Output = F::Output;
-
-    fn poll(mut self: PinMut<Self>, cx: &mut task::Context) -> Poll<Self::Output> {
-        F::poll((*self).reborrow(), cx)
-    }
-}
-
-if_std! {
-    use std::boxed::{Box, PinBox};
-
-    impl<'a, F: ?Sized + Future + Unpin> Future for Box<F> {
-        type Output = F::Output;
-
-        fn poll(mut self: PinMut<Self>, cx: &mut task::Context) -> Poll<Self::Output> {
-            (**self).poll_unpin(cx)
-        }
-    }
-
-    impl<'a, F: ?Sized + Future> Future for PinBox<F> {
-        type Output = F::Output;
-
-        fn poll(mut self: PinMut<Self>, cx: &mut task::Context) -> Poll<Self::Output> {
-            self.as_pin_mut().poll(cx)
-        }
-    }
-
-    impl<'a, F: Future> Future for ::std::panic::AssertUnwindSafe<F> {
-        type Output = F::Output;
-
-        fn poll(mut self: PinMut<Self>, cx: &mut task::Context) -> Poll<Self::Output> {
-            unsafe { pinned_field!(self, 0).poll(cx) }
-        }
-    }
-}
-
+impl<T: ?Sized> CoreFutureExt for T where T: Future {}
+
 /// A convenience for futures that return `Result` values that includes
 /// a variety of adapters tailored to such futures.
 pub trait TryFuture {

futures-core/src/lib.rs

@@ -1,6 +1,7 @@
 //! Core traits and types for asynchronous operations in Rust.
 
 #![feature(pin, arbitrary_self_types)]
+#![feature(futures_api)]
 
 #![no_std]
 #![deny(missing_docs, missing_debug_implementations, warnings)]

futures-core/src/poll.rs

@@ -1,3 +1,6 @@
+
+pub use core::task::Poll;
+
 /// A macro for extracting the successful type of a `Poll<Result<T, E>>`.
 ///
 /// This macro bakes in propagation of `Pending` and `Err` signals by returning early.
@@ -38,73 +41,3 @@ macro_rules! ready {
         $crate::Poll::Pending => return $crate::Poll::Pending,
     })
 }
-
-/// Indicates whether a value is available, or if the current task has been
-/// scheduled for later wake-up instead.
-#[derive(Copy, Clone, Debug, PartialEq)]
-pub enum Poll<T> {
-    /// Represents that a value is immediately ready.
-    Ready(T),
-
-    /// Represents that a value is not ready yet.
-    ///
-    /// When a function returns `Pending`, the function *must* also
-    /// ensure that the current task is scheduled to be awoken when
-    /// progress can be made.
-    Pending,
-}
-
-impl<T> Poll<T> {
-    /// Change the ready value of this `Poll` with the closure provided
-    pub fn map<U, F>(self, f: F) -> Poll<U>
-        where F: FnOnce(T) -> U
-    {
-        match self {
-            Poll::Ready(t) => Poll::Ready(f(t)),
-            Poll::Pending => Poll::Pending,
-        }
-    }
-
-    /// Returns whether this is `Poll::Ready`
-    pub fn is_ready(&self) -> bool {
-        match *self {
-            Poll::Ready(_) => true,
-            Poll::Pending => false,
-        }
-    }
-
-    /// Returns whether this is `Poll::Pending`
-    pub fn is_pending(&self) -> bool {
-        !self.is_ready()
-    }
-}
-
-impl<T, E> Poll<Result<T, E>> {
-    /// Change the success value of this `Poll` with the closure provided
-    pub fn map_ok<U, F>(self, f: F) -> Poll<Result<U, E>>
-        where F: FnOnce(T) -> U
-    {
-        match self {
-            Poll::Ready(Ok(t)) => Poll::Ready(Ok(f(t))),
-            Poll::Ready(Err(e)) => Poll::Ready(Err(e)),
-            Poll::Pending => Poll::Pending,
-        }
-    }
-
-    /// Change the error value of this `Poll` with the closure provided
-    pub fn map_err<U, F>(self, f: F) -> Poll<Result<T, U>>
-        where F: FnOnce(E) -> U
-    {
-        match self {
-            Poll::Ready(Ok(t)) => Poll::Ready(Ok(t)),
-            Poll::Ready(Err(e)) => Poll::Ready(Err(f(e))),
-            Poll::Pending => Poll::Pending,
-        }
-    }
-}
-
-impl<T> From<T> for Poll<T> {
-    fn from(t: T) -> Poll<T> {
-        Poll::Ready(t)
-    }
-}