Add Future and task system to the standard library

1 files changed, 140 insertions, 0 deletions

diff --git a/src/liballoc/task.rs b/src/liballoc/task.rs
new file mode 100644
index 00000000000..7b1947b56b8
--- /dev/null
+++ b/src/liballoc/task.rs
@@ -0,0 +1,140 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Types and Traits for working with asynchronous tasks.
+
+pub use core::task::*;
+
+#[cfg(target_has_atomic = "ptr")]
+pub use self::if_arc::*;
+
+#[cfg(target_has_atomic = "ptr")]
+mod if_arc {
+    use super::*;
+    use arc::Arc;
+    use core::marker::PhantomData;
+    use core::mem;
+    use core::ptr::{self, NonNull};
+
+    /// A way of waking up a specific task.
+    ///
+    /// Any task executor must provide a way of signaling that a task it owns
+    /// is ready to be `poll`ed again. Executors do so by implementing this trait.
+    pub trait Wake: Send + Sync {
+        /// Indicates that the associated task is ready to make progress and should
+        /// be `poll`ed.
+        ///
+        /// Executors generally maintain a queue of "ready" tasks; `wake` should place
+        /// the associated task onto this queue.
+        fn wake(arc_self: &Arc<Self>);
+
+        /// Indicates that the associated task is ready to make progress and should
+        /// be `poll`ed. This function is like `wake`, but can only be called from the
+        /// thread on which this `Wake` was created.
+        ///
+        /// Executors generally maintain a queue of "ready" tasks; `wake_local` should place
+        /// the associated task onto this queue.
+        #[inline]
+        unsafe fn wake_local(arc_self: &Arc<Self>) {
+            Self::wake(arc_self);
+        }
+    }
+
+    #[cfg(target_has_atomic = "ptr")]
+    struct ArcWrapped<T>(PhantomData<T>);
+
+    unsafe impl<T: Wake + 'static> UnsafeWake for ArcWrapped<T> {
+        #[inline]
+        unsafe fn clone_raw(&self) -> Waker {
+            let me: *const ArcWrapped<T> = self;
+            let arc = (*(&me as *const *const ArcWrapped<T> as *const Arc<T>)).clone();
+            Waker::from(arc)
+        }
+
+        #[inline]
+        unsafe fn drop_raw(&self) {
+            let mut me: *const ArcWrapped<T> = self;
+            let me = &mut me as *mut *const ArcWrapped<T> as *mut Arc<T>;
+            ptr::drop_in_place(me);
+        }
+
+        #[inline]
+        unsafe fn wake(&self) {
+            let me: *const ArcWrapped<T> = self;
+            T::wake(&*(&me as *const *const ArcWrapped<T> as *const Arc<T>))
+        }
+
+        #[inline]
+        unsafe fn wake_local(&self) {
+            let me: *const ArcWrapped<T> = self;
+            T::wake_local(&*(&me as *const *const ArcWrapped<T> as *const Arc<T>))
+        }
+    }
+
+    impl<T> From<Arc<T>> for Waker
+        where T: Wake + 'static,
+    {
+        fn from(rc: Arc<T>) -> Self {
+            unsafe {
+                let ptr = mem::transmute::<Arc<T>, NonNull<ArcWrapped<T>>>(rc);
+                Waker::new(ptr)
+            }
+        }
+    }
+
+    /// Creates a `LocalWaker` from a local `wake`.
+    ///
+    /// This function requires that `wake` is "local" (created on the current thread).
+    /// The resulting `LocalWaker` will call `wake.wake_local()` when awoken, and
+    /// will call `wake.wake()` if awoken after being converted to a `Waker`.
+    #[inline]
+    pub unsafe fn local_waker<W: Wake + 'static>(wake: Arc<W>) -> LocalWaker {
+        let ptr = mem::transmute::<Arc<W>, NonNull<ArcWrapped<W>>>(wake);
+        LocalWaker::new(ptr)
+    }
+
+    struct NonLocalAsLocal<T>(ArcWrapped<T>);
+
+    unsafe impl<T: Wake + 'static> UnsafeWake for NonLocalAsLocal<T> {
+        #[inline]
+        unsafe fn clone_raw(&self) -> Waker {
+            self.0.clone_raw()
+        }
+
+        #[inline]
+        unsafe fn drop_raw(&self) {
+            self.0.drop_raw()
+        }
+
+        #[inline]
+        unsafe fn wake(&self) {
+            self.0.wake()
+        }
+
+        #[inline]
+        unsafe fn wake_local(&self) {
+            // Since we're nonlocal, we can't call wake_local
+            self.0.wake()
+        }
+    }
+
+    /// Creates a `LocalWaker` from a non-local `wake`.
+    ///
+    /// This function is similar to `local_waker`, but does not require that `wake`
+    /// is local to the current thread. The resulting `LocalWaker` will call
+    /// `wake.wake()` when awoken.
+    #[inline]
+    pub fn local_waker_from_nonlocal<W: Wake + 'static>(wake: Arc<W>) -> LocalWaker {
+        unsafe {
+            let ptr = mem::transmute::<Arc<W>, NonNull<NonLocalAsLocal<W>>>(wake);
+            LocalWaker::new(ptr)
+        }
+    }
+}