Snap for 6435660 from 3e38deba2a5b538a2aca805cc0c27378e1c5c2d7 to sdk-release
Change-Id: I8060e269c025c3093ef55ec4181ce61db4b3798e
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..27261e5
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,13 @@
+// This file is generated by cargo2android.py.
+
+rust_library_host_rlib {
+ name: "libfutures_task",
+ crate_name: "futures_task",
+ srcs: ["src/lib.rs"],
+ edition: "2018",
+ features: [
+ "alloc",
+ "default",
+ "std",
+ ],
+}
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..35a136e
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,33 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies
+#
+# If you believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+edition = "2018"
+name = "futures-task"
+version = "0.3.4"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+description = "Tools for working with tasks.\n"
+homepage = "https://rust-lang.github.io/futures-rs"
+documentation = "https://rust-lang.github.io/futures-api-docs/0.3.0-alpha.18/futures_core"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-lang/futures-rs"
+[package.metadata.docs.rs]
+all-features = true
+
+[dependencies]
+
+[features]
+alloc = []
+cfg-target-has-atomic = []
+default = ["std"]
+std = ["alloc"]
+unstable = []
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..0b4b62a
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,28 @@
+[package]
+name = "futures-task"
+edition = "2018"
+version = "0.3.4"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-lang/futures-rs"
+homepage = "https://rust-lang.github.io/futures-rs"
+documentation = "https://rust-lang.github.io/futures-api-docs/0.3.0-alpha.18/futures_core"
+description = """
+Tools for working with tasks.
+"""
+
+[features]
+default = ["std"]
+std = ["alloc"]
+alloc = []
+
+# Unstable features
+# These features are outside of the normal semver guarantees and require the
+# `unstable` feature as an explicit opt-in to unstable API.
+unstable = []
+cfg-target-has-atomic = []
+
+[dependencies]
+
+[package.metadata.docs.rs]
+all-features = true
diff --git a/LICENSE b/LICENSE
new file mode 120000
index 0000000..6b579aa
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1 @@
+LICENSE-APACHE
\ No newline at end of file
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..9eb0b09
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,202 @@
+ Apache License
+ Version 2.0, January 2004
+ http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+ "License" shall mean the terms and conditions for use, reproduction,
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+ "Derivative Works" shall mean any work, whether in Source or Object
+ form, that is based on (or derived from) the Work and for which the
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+ "Contribution" shall mean any work of authorship, including
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+ "Contributor" shall mean Licensor and any individual or Legal Entity
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+4. Redistribution. You may reproduce and distribute copies of the
+ Work or Derivative Works thereof in any medium, with or without
+ modifications, and in Source or Object form, provided that You
+ meet the following conditions:
+
+ (a) You must give any other recipients of the Work or
+ Derivative Works a copy of this License; and
+
+ (b) You must cause any modified files to carry prominent notices
+ stating that You changed the files; and
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+ (c) You must retain, in the Source form of any Derivative Works
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+ (d) If the Work includes a "NOTICE" text file as part of its
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+ of the following places: within a NOTICE text file distributed
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+ wherever such third-party notices normally appear. The contents
+ of the NOTICE file are for informational purposes only and
+ do not modify the License. You may add Your own attribution
+ notices within Derivative Works that You distribute, alongside
+ or as an addendum to the NOTICE text from the Work, provided
+ that such additional attribution notices cannot be construed
+ as modifying the License.
+
+ You may add Your own copyright statement to Your modifications and
+ may provide additional or different license terms and conditions
+ for use, reproduction, or distribution of Your modifications, or
+ for any such Derivative Works as a whole, provided Your use,
+ reproduction, and distribution of the Work otherwise complies with
+ the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise,
+ any Contribution intentionally submitted for inclusion in the Work
+ by You to the Licensor shall be under the terms and conditions of
+ this License, without any additional terms or conditions.
+ Notwithstanding the above, nothing herein shall supersede or modify
+ the terms of any separate license agreement you may have executed
+ with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+ names, trademarks, service marks, or product names of the Licensor,
+ except as required for reasonable and customary use in describing the
+ origin of the Work and reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or
+ agreed to in writing, Licensor provides the Work (and each
+ Contributor provides its Contributions) on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ implied, including, without limitation, any warranties or conditions
+ of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+ PARTICULAR PURPOSE. You are solely responsible for determining the
+ appropriateness of using or redistributing the Work and assume any
+ risks associated with Your exercise of permissions under this License.
+
+8. Limitation of Liability. In no event and under no legal theory,
+ whether in tort (including negligence), contract, or otherwise,
+ unless required by applicable law (such as deliberate and grossly
+ negligent acts) or agreed to in writing, shall any Contributor be
+ liable to You for damages, including any direct, indirect, special,
+ incidental, or consequential damages of any character arising as a
+ result of this License or out of the use or inability to use the
+ Work (including but not limited to damages for loss of goodwill,
+ work stoppage, computer failure or malfunction, or any and all
+ other commercial damages or losses), even if such Contributor
+ has been advised of the possibility of such damages.
+
+9. Accepting Warranty or Additional Liability. While redistributing
+ the Work or Derivative Works thereof, You may choose to offer,
+ and charge a fee for, acceptance of support, warranty, indemnity,
+ or other liability obligations and/or rights consistent with this
+ License. However, in accepting such obligations, You may act only
+ on Your own behalf and on Your sole responsibility, not on behalf
+ of any other Contributor, and only if You agree to indemnify,
+ defend, and hold each Contributor harmless for any liability
+ incurred by, or claims asserted against, such Contributor by reason
+ of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+ To apply the Apache License to your work, attach the following
+ boilerplate notice, with the fields enclosed by brackets "[]"
+ replaced with your own identifying information. (Don't include
+ the brackets!) The text should be enclosed in the appropriate
+ comment syntax for the file format. We also recommend that a
+ file or class name and description of purpose be included on the
+ same "printed page" as the copyright notice for easier
+ identification within third-party archives.
+
+Copyright (c) 2016 Alex Crichton
+Copyright (c) 2017 The Tokio Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..8ad082e
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,26 @@
+Copyright (c) 2016 Alex Crichton
+Copyright (c) 2017 The Tokio Authors
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. 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/METADATA b/METADATA
new file mode 100644
index 0000000..77fddf1
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,17 @@
+name: "futures-task"
+description:
+ "Tools for working with tasks."
+
+third_party {
+ url {
+ type: HOMEPAGE
+ value: "https://crates.io/crates/futures-task"
+ }
+ url {
+ type: GIT
+ value: "https://github.com/rust-lang/futures-rs"
+ }
+ version: "0.3.4"
+ last_upgrade_date { year: 2020 month: 3 day: 17 }
+ license_type: NOTICE
+}
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/NOTICE b/NOTICE
new file mode 120000
index 0000000..7a694c9
--- /dev/null
+++ b/NOTICE
@@ -0,0 +1 @@
+LICENSE
\ No newline at end of file
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..46fc303
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/prebuilts/rust:/OWNERS
diff --git a/src/arc_wake.rs b/src/arc_wake.rs
new file mode 100644
index 0000000..aa6de0f
--- /dev/null
+++ b/src/arc_wake.rs
@@ -0,0 +1,49 @@
+use alloc::sync::Arc;
+
+/// A way of waking up a specific task.
+///
+/// By implementing this trait, types that are expected to be wrapped in an `Arc`
+/// can be converted into [`Waker`] objects.
+/// Those Wakers can be used to signal executors that a task it owns
+/// is ready to be `poll`ed again.
+///
+/// Currently, there are two ways to convert `ArcWake` into [`Waker`]:
+///
+/// * [`waker`](super::waker()) converts `Arc<impl ArcWake>` into [`Waker`].
+/// * [`waker_ref`](super::waker_ref()) converts `&Arc<impl ArcWake>` into [`WakerRef`] that
+/// provides access to a [`&Waker`][`Waker`].
+///
+/// [`Waker`]: std::task::Waker
+/// [`WakerRef`]: super::WakerRef
+// Note: Send + Sync required because `Arc<T>` doesn't automatically imply
+// those bounds, but `Waker` implements them.
+pub trait ArcWake: Send + Sync {
+ /// Indicates that the associated task is ready to make progress and should
+ /// be `poll`ed.
+ ///
+ /// This function can be called from an arbitrary thread, including threads which
+ /// did not create the `ArcWake` based [`Waker`].
+ ///
+ /// Executors generally maintain a queue of "ready" tasks; `wake` should place
+ /// the associated task onto this queue.
+ ///
+ /// [`Waker`]: std::task::Waker
+ fn wake(self: Arc<Self>) {
+ Self::wake_by_ref(&self)
+ }
+
+ /// Indicates that the associated task is ready to make progress and should
+ /// be `poll`ed.
+ ///
+ /// This function can be called from an arbitrary thread, including threads which
+ /// did not create the `ArcWake` based [`Waker`].
+ ///
+ /// Executors generally maintain a queue of "ready" tasks; `wake_by_ref` should place
+ /// the associated task onto this queue.
+ ///
+ /// This function is similar to [`wake`](ArcWake::wake), but must not consume the provided data
+ /// pointer.
+ ///
+ /// [`Waker`]: std::task::Waker
+ fn wake_by_ref(arc_self: &Arc<Self>);
+}
diff --git a/src/future_obj.rs b/src/future_obj.rs
new file mode 100644
index 0000000..6acdf7c
--- /dev/null
+++ b/src/future_obj.rs
@@ -0,0 +1,344 @@
+use core::{
+ mem,
+ fmt,
+ future::Future,
+ marker::PhantomData,
+ pin::Pin,
+ task::{Context, Poll},
+};
+
+/// A custom trait object for polling futures, roughly akin to
+/// `Box<dyn Future<Output = T> + 'a>`.
+///
+/// This custom trait object was introduced as currently it is not possible to
+/// take `dyn Trait` by value and `Box<dyn Trait>` is not available in no_std
+/// contexts.
+pub struct LocalFutureObj<'a, T> {
+ future: *mut (dyn Future<Output = T> + 'static),
+ drop_fn: unsafe fn(*mut (dyn Future<Output = T> + 'static)),
+ _marker: PhantomData<&'a ()>,
+}
+
+// As LocalFutureObj only holds pointers, even if we move it, the pointed to values won't move,
+// so this is safe as long as we don't provide any way for a user to directly access the pointers
+// and move their values.
+impl<T> Unpin for LocalFutureObj<'_, T> {}
+
+#[allow(single_use_lifetimes)]
+#[allow(clippy::transmute_ptr_to_ptr)]
+unsafe fn remove_future_lifetime<'a, T>(ptr: *mut (dyn Future<Output = T> + 'a))
+ -> *mut (dyn Future<Output = T> + 'static)
+{
+ mem::transmute(ptr)
+}
+
+#[allow(single_use_lifetimes)]
+unsafe fn remove_drop_lifetime<'a, T>(ptr: unsafe fn (*mut (dyn Future<Output = T> + 'a)))
+ -> unsafe fn(*mut (dyn Future<Output = T> + 'static))
+{
+ mem::transmute(ptr)
+}
+
+impl<'a, T> LocalFutureObj<'a, T> {
+ /// Create a `LocalFutureObj` from a custom trait object representation.
+ #[inline]
+ pub fn new<F: UnsafeFutureObj<'a, T> + 'a>(f: F) -> LocalFutureObj<'a, T> {
+ LocalFutureObj {
+ future: unsafe { remove_future_lifetime(f.into_raw()) },
+ drop_fn: unsafe { remove_drop_lifetime(F::drop) },
+ _marker: PhantomData,
+ }
+ }
+
+ /// Converts the `LocalFutureObj` into a `FutureObj`.
+ ///
+ /// # Safety
+ ///
+ /// To make this operation safe one has to ensure that the `UnsafeFutureObj`
+ /// instance from which this `LocalFutureObj` was created actually
+ /// implements `Send`.
+ #[inline]
+ pub unsafe fn into_future_obj(self) -> FutureObj<'a, T> {
+ FutureObj(self)
+ }
+}
+
+impl<T> fmt::Debug for LocalFutureObj<'_, T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.debug_struct("LocalFutureObj")
+ .finish()
+ }
+}
+
+impl<'a, T> From<FutureObj<'a, T>> for LocalFutureObj<'a, T> {
+ #[inline]
+ fn from(f: FutureObj<'a, T>) -> LocalFutureObj<'a, T> {
+ f.0
+ }
+}
+
+impl<T> Future for LocalFutureObj<'_, T> {
+ type Output = T;
+
+ #[inline]
+ fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
+ unsafe {
+ Pin::new_unchecked(&mut *self.future).poll(cx)
+ }
+ }
+}
+
+impl<T> Drop for LocalFutureObj<'_, T> {
+ fn drop(&mut self) {
+ unsafe {
+ (self.drop_fn)(self.future)
+ }
+ }
+}
+
+/// A custom trait object for polling futures, roughly akin to
+/// `Box<dyn Future<Output = T> + Send + 'a>`.
+///
+/// This custom trait object was introduced as currently it is not possible to
+/// take `dyn Trait` by value and `Box<dyn Trait>` is not available in no_std
+/// contexts.
+///
+/// You should generally not need to use this type outside of `no_std` or when
+/// implementing `Spawn`, consider using `BoxFuture` instead.
+pub struct FutureObj<'a, T>(LocalFutureObj<'a, T>);
+
+impl<T> Unpin for FutureObj<'_, T> {}
+unsafe impl<T> Send for FutureObj<'_, T> {}
+
+impl<'a, T> FutureObj<'a, T> {
+ /// Create a `FutureObj` from a custom trait object representation.
+ #[inline]
+ pub fn new<F: UnsafeFutureObj<'a, T> + Send>(f: F) -> FutureObj<'a, T> {
+ FutureObj(LocalFutureObj::new(f))
+ }
+}
+
+impl<T> fmt::Debug for FutureObj<'_, T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.debug_struct("FutureObj")
+ .finish()
+ }
+}
+
+impl<T> Future for FutureObj<'_, T> {
+ type Output = T;
+
+ #[inline]
+ fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
+ Pin::new( &mut self.0 ).poll(cx)
+ }
+}
+
+/// A custom implementation of a future trait object for `FutureObj`, providing
+/// a vtable with drop support.
+///
+/// This custom representation is typically used only in `no_std` contexts,
+/// where the default `Box`-based implementation is not available.
+///
+/// # Safety
+///
+/// See the safety notes on individual methods for what guarantees an
+/// implementor must provide.
+pub unsafe trait UnsafeFutureObj<'a, T>: 'a {
+ /// Convert an owned instance into a (conceptually owned) fat pointer.
+ ///
+ /// # Safety
+ ///
+ /// ## Implementor
+ ///
+ /// The trait implementor must guarantee that it is safe to convert the
+ /// provided `*mut (dyn Future<Output = T> + 'a)` into a `Pin<&mut (dyn
+ /// Future<Output = T> + 'a)>` and call methods on it, non-reentrantly,
+ /// until `UnsafeFutureObj::drop` is called with it.
+ fn into_raw(self) -> *mut (dyn Future<Output = T> + 'a);
+
+ /// Drops the future represented by the given fat pointer.
+ ///
+ /// # Safety
+ ///
+ /// ## Implementor
+ ///
+ /// The trait implementor must guarantee that it is safe to call this
+ /// function once per `into_raw` invocation.
+ ///
+ /// ## Caller
+ ///
+ /// The caller must ensure:
+ ///
+ /// * the pointer passed was obtained from an `into_raw` invocation from
+ /// this same trait object
+ /// * the pointer is not currently in use as a `Pin<&mut (dyn Future<Output
+ /// = T> + 'a)>`
+ /// * the pointer must not be used again after this function is called
+ unsafe fn drop(ptr: *mut (dyn Future<Output = T> + 'a));
+}
+
+unsafe impl<'a, T, F> UnsafeFutureObj<'a, T> for &'a mut F
+where
+ F: Future<Output = T> + Unpin + 'a
+{
+ fn into_raw(self) -> *mut (dyn Future<Output = T> + 'a) {
+ self as *mut dyn Future<Output = T>
+ }
+
+ unsafe fn drop(_ptr: *mut (dyn Future<Output = T> + 'a)) {}
+}
+
+unsafe impl<'a, T> UnsafeFutureObj<'a, T> for &'a mut (dyn Future<Output = T> + Unpin + 'a)
+{
+ fn into_raw(self) -> *mut (dyn Future<Output = T> + 'a) {
+ self as *mut dyn Future<Output = T>
+ }
+
+ unsafe fn drop(_ptr: *mut (dyn Future<Output = T> + 'a)) {}
+}
+
+unsafe impl<'a, T, F> UnsafeFutureObj<'a, T> for Pin<&'a mut F>
+where
+ F: Future<Output = T> + 'a
+{
+ fn into_raw(self) -> *mut (dyn Future<Output = T> + 'a) {
+ unsafe { self.get_unchecked_mut() as *mut dyn Future<Output = T> }
+ }
+
+ unsafe fn drop(_ptr: *mut (dyn Future<Output = T> + 'a)) {}
+}
+
+unsafe impl<'a, T> UnsafeFutureObj<'a, T> for Pin<&'a mut (dyn Future<Output = T> + 'a)>
+{
+ fn into_raw(self) -> *mut (dyn Future<Output = T> + 'a) {
+ unsafe { self.get_unchecked_mut() as *mut dyn Future<Output = T> }
+ }
+
+ unsafe fn drop(_ptr: *mut (dyn Future<Output = T> + 'a)) {}
+}
+
+#[cfg(feature = "alloc")]
+mod if_alloc {
+ use super::*;
+ use alloc::boxed::Box;
+
+ unsafe impl<'a, T, F> UnsafeFutureObj<'a, T> for Box<F>
+ where F: Future<Output = T> + 'a
+ {
+ fn into_raw(self) -> *mut (dyn Future<Output = T> + 'a) {
+ Box::into_raw(self)
+ }
+
+ unsafe fn drop(ptr: *mut (dyn Future<Output = T> + 'a)) {
+ drop(Box::from_raw(ptr as *mut F))
+ }
+ }
+
+ unsafe impl<'a, T: 'a> UnsafeFutureObj<'a, T> for Box<dyn Future<Output = T> + 'a> {
+ fn into_raw(self) -> *mut (dyn Future<Output = T> + 'a) {
+ Box::into_raw(self)
+ }
+
+ unsafe fn drop(ptr: *mut (dyn Future<Output = T> + 'a)) {
+ drop(Box::from_raw(ptr))
+ }
+ }
+
+ unsafe impl<'a, T: 'a> UnsafeFutureObj<'a, T> for Box<dyn Future<Output = T> + Send + 'a> {
+ fn into_raw(self) -> *mut (dyn Future<Output = T> + 'a) {
+ Box::into_raw(self)
+ }
+
+ unsafe fn drop(ptr: *mut (dyn Future<Output = T> + 'a)) {
+ drop(Box::from_raw(ptr))
+ }
+ }
+
+ unsafe impl<'a, T, F> UnsafeFutureObj<'a, T> for Pin<Box<F>>
+ where
+ F: Future<Output = T> + 'a
+ {
+ fn into_raw(mut self) -> *mut (dyn Future<Output = T> + 'a) {
+ let ptr = unsafe { self.as_mut().get_unchecked_mut() as *mut _ };
+ mem::forget(self);
+ ptr
+ }
+
+ unsafe fn drop(ptr: *mut (dyn Future<Output = T> + 'a)) {
+ drop(Pin::from(Box::from_raw(ptr)))
+ }
+ }
+
+ unsafe impl<'a, T: 'a> UnsafeFutureObj<'a, T> for Pin<Box<dyn Future<Output = T> + 'a>> {
+ fn into_raw(mut self) -> *mut (dyn Future<Output = T> + 'a) {
+ let ptr = unsafe { self.as_mut().get_unchecked_mut() as *mut _ };
+ mem::forget(self);
+ ptr
+ }
+
+ unsafe fn drop(ptr: *mut (dyn Future<Output = T> + 'a)) {
+ drop(Pin::from(Box::from_raw(ptr)))
+ }
+ }
+
+ unsafe impl<'a, T: 'a> UnsafeFutureObj<'a, T> for Pin<Box<dyn Future<Output = T> + Send + 'a>> {
+ fn into_raw(mut self) -> *mut (dyn Future<Output = T> + 'a) {
+ let ptr = unsafe { self.as_mut().get_unchecked_mut() as *mut _ };
+ mem::forget(self);
+ ptr
+ }
+
+ unsafe fn drop(ptr: *mut (dyn Future<Output = T> + 'a)) {
+ drop(Pin::from(Box::from_raw(ptr)))
+ }
+ }
+
+ impl<'a, F: Future<Output = ()> + Send + 'a> From<Box<F>> for FutureObj<'a, ()> {
+ fn from(boxed: Box<F>) -> Self {
+ FutureObj::new(boxed)
+ }
+ }
+
+ impl<'a> From<Box<dyn Future<Output = ()> + Send + 'a>> for FutureObj<'a, ()> {
+ fn from(boxed: Box<dyn Future<Output = ()> + Send + 'a>) -> Self {
+ FutureObj::new(boxed)
+ }
+ }
+
+ impl<'a, F: Future<Output = ()> + Send + 'a> From<Pin<Box<F>>> for FutureObj<'a, ()> {
+ fn from(boxed: Pin<Box<F>>) -> Self {
+ FutureObj::new(boxed)
+ }
+ }
+
+ impl<'a> From<Pin<Box<dyn Future<Output = ()> + Send + 'a>>> for FutureObj<'a, ()> {
+ fn from(boxed: Pin<Box<dyn Future<Output = ()> + Send + 'a>>) -> Self {
+ FutureObj::new(boxed)
+ }
+ }
+
+ impl<'a, F: Future<Output = ()> + 'a> From<Box<F>> for LocalFutureObj<'a, ()> {
+ fn from(boxed: Box<F>) -> Self {
+ LocalFutureObj::new(boxed)
+ }
+ }
+
+ impl<'a> From<Box<dyn Future<Output = ()> + 'a>> for LocalFutureObj<'a, ()> {
+ fn from(boxed: Box<dyn Future<Output = ()> + 'a>) -> Self {
+ LocalFutureObj::new(boxed)
+ }
+ }
+
+ impl<'a, F: Future<Output = ()> + 'a> From<Pin<Box<F>>> for LocalFutureObj<'a, ()> {
+ fn from(boxed: Pin<Box<F>>) -> Self {
+ LocalFutureObj::new(boxed)
+ }
+ }
+
+ impl<'a> From<Pin<Box<dyn Future<Output = ()> + 'a>>> for LocalFutureObj<'a, ()> {
+ fn from(boxed: Pin<Box<dyn Future<Output = ()> + 'a>>) -> Self {
+ LocalFutureObj::new(boxed)
+ }
+ }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..b18a33a
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,57 @@
+//! Tools for working with tasks.
+
+#![cfg_attr(feature = "cfg-target-has-atomic", feature(cfg_target_has_atomic))]
+
+#![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://docs.rs/futures-task/0.3.0")]
+
+#[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(feature = "alloc")]
+extern crate alloc;
+
+macro_rules! cfg_target_has_atomic {
+ ($($item:item)*) => {$(
+ #[cfg_attr(feature = "cfg-target-has-atomic", cfg(target_has_atomic = "ptr"))]
+ $item
+ )*};
+}
+
+mod spawn;
+pub use crate::spawn::{Spawn, SpawnError, LocalSpawn};
+
+cfg_target_has_atomic! {
+ #[cfg(feature = "alloc")]
+ mod arc_wake;
+ #[cfg(feature = "alloc")]
+ pub use crate::arc_wake::ArcWake;
+
+ #[cfg(feature = "alloc")]
+ mod waker;
+ #[cfg(feature = "alloc")]
+ pub use crate::waker::waker;
+
+ #[cfg(feature = "alloc")]
+ mod waker_ref;
+ #[cfg(feature = "alloc")]
+ pub use crate::waker_ref::{waker_ref, WakerRef};
+}
+
+mod future_obj;
+pub use crate::future_obj::{FutureObj, LocalFutureObj, UnsafeFutureObj};
+
+mod noop_waker;
+pub use crate::noop_waker::noop_waker;
+#[cfg(feature = "std")]
+pub use crate::noop_waker::noop_waker_ref;
+
+pub use core::task::{Context, Poll, Waker, RawWaker, RawWakerVTable};
diff --git a/src/noop_waker.rs b/src/noop_waker.rs
new file mode 100644
index 0000000..a0924ad
--- /dev/null
+++ b/src/noop_waker.rs
@@ -0,0 +1,55 @@
+//! Utilities for creating zero-cost wakers that don't do anything.
+
+use core::task::{RawWaker, RawWakerVTable, Waker};
+use core::ptr::null;
+#[cfg(feature = "std")]
+use core::cell::UnsafeCell;
+
+unsafe fn noop_clone(_data: *const ()) -> RawWaker {
+ noop_raw_waker()
+}
+
+unsafe fn noop(_data: *const ()) {}
+
+const NOOP_WAKER_VTABLE: RawWakerVTable = RawWakerVTable::new(noop_clone, noop, noop, noop);
+
+fn noop_raw_waker() -> RawWaker {
+ RawWaker::new(null(), &NOOP_WAKER_VTABLE)
+}
+
+/// Create a new [`Waker`] which does
+/// nothing when `wake()` is called on it.
+///
+/// # Examples
+///
+/// ```
+/// use futures::task::noop_waker;
+/// let waker = noop_waker();
+/// waker.wake();
+/// ```
+#[inline]
+pub fn noop_waker() -> Waker {
+ unsafe {
+ Waker::from_raw(noop_raw_waker())
+ }
+}
+
+/// Get a static reference to a [`Waker`] which
+/// does nothing when `wake()` is called on it.
+///
+/// # Examples
+///
+/// ```
+/// use futures::task::noop_waker_ref;
+/// let waker = noop_waker_ref();
+/// waker.wake_by_ref();
+/// ```
+#[inline]
+#[cfg(feature = "std")]
+pub fn noop_waker_ref() -> &'static Waker {
+ thread_local! {
+ static NOOP_WAKER_INSTANCE: UnsafeCell<Waker> =
+ UnsafeCell::new(noop_waker());
+ }
+ NOOP_WAKER_INSTANCE.with(|l| unsafe { &*l.get() })
+}
diff --git a/src/spawn.rs b/src/spawn.rs
new file mode 100644
index 0000000..a515dd4
--- /dev/null
+++ b/src/spawn.rs
@@ -0,0 +1,194 @@
+use crate::{FutureObj, LocalFutureObj};
+use core::fmt;
+
+/// The `Spawn` trait allows for pushing futures onto an executor that will
+/// run them to completion.
+pub trait Spawn {
+ /// Spawns a future that will be run to completion.
+ ///
+ /// # Errors
+ ///
+ /// The executor may be unable to spawn tasks. Spawn errors should
+ /// represent relatively rare scenarios, such as the executor
+ /// having been shut down so that it is no longer able to accept
+ /// tasks.
+ fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError>;
+
+ /// Determines whether the executor is able to spawn new tasks.
+ ///
+ /// This method will return `Ok` when 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.
+ #[inline]
+ fn status(&self) -> Result<(), SpawnError> {
+ Ok(())
+ }
+}
+
+/// The `LocalSpawn` is similar to [`Spawn`], but allows spawning futures
+/// that don't implement `Send`.
+pub trait LocalSpawn {
+ /// Spawns a future that will be run to completion.
+ ///
+ /// # Errors
+ ///
+ /// The executor may be unable to spawn tasks. Spawn errors should
+ /// represent relatively rare scenarios, such as the executor
+ /// having been shut down so that it is no longer able to accept
+ /// tasks.
+ fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError>;
+
+ /// Determines whether the executor is able to spawn new tasks.
+ ///
+ /// This method will return `Ok` when 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.
+ #[inline]
+ fn status_local(&self) -> Result<(), SpawnError> {
+ Ok(())
+ }
+}
+
+/// An error that occurred during spawning.
+pub struct SpawnError {
+ _priv: (),
+}
+
+impl fmt::Debug for SpawnError {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.debug_tuple("SpawnError").field(&"shutdown").finish()
+ }
+}
+
+impl fmt::Display for SpawnError {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "Executor is shutdown")
+ }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for SpawnError {}
+
+impl SpawnError {
+ /// Spawning failed because the executor has been shut down.
+ pub fn shutdown() -> Self {
+ Self { _priv: () }
+ }
+
+ /// Check whether spawning failed to the executor being shut down.
+ pub fn is_shutdown(&self) -> bool {
+ true
+ }
+}
+
+impl<Sp: ?Sized + Spawn> Spawn for &Sp {
+ fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> {
+ Sp::spawn_obj(self, future)
+ }
+
+ fn status(&self) -> Result<(), SpawnError> {
+ Sp::status(self)
+ }
+}
+
+impl<Sp: ?Sized + Spawn> Spawn for &mut Sp {
+ fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> {
+ Sp::spawn_obj(self, future)
+ }
+
+ fn status(&self) -> Result<(), SpawnError> {
+ Sp::status(self)
+ }
+}
+
+impl<Sp: ?Sized + LocalSpawn> LocalSpawn for &Sp {
+ fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> {
+ Sp::spawn_local_obj(self, future)
+ }
+
+ fn status_local(&self) -> Result<(), SpawnError> {
+ Sp::status_local(self)
+ }
+}
+
+impl<Sp: ?Sized + LocalSpawn> LocalSpawn for &mut Sp {
+ fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> {
+ Sp::spawn_local_obj(self, future)
+ }
+
+ fn status_local(&self) -> Result<(), SpawnError> {
+ Sp::status_local(self)
+ }
+}
+
+#[cfg(feature = "alloc")]
+mod if_alloc {
+ use super::*;
+ use alloc::{ boxed::Box, rc::Rc };
+
+ impl<Sp: ?Sized + Spawn> Spawn for Box<Sp> {
+ fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> {
+ (**self).spawn_obj(future)
+ }
+
+ fn status(&self) -> Result<(), SpawnError> {
+ (**self).status()
+ }
+ }
+
+ impl<Sp: ?Sized + LocalSpawn> LocalSpawn for Box<Sp> {
+ fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> {
+ (**self).spawn_local_obj(future)
+ }
+
+ fn status_local(&self) -> Result<(), SpawnError> {
+ (**self).status_local()
+ }
+ }
+
+ impl<Sp: ?Sized + Spawn> Spawn for Rc<Sp> {
+ fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> {
+ (**self).spawn_obj(future)
+ }
+
+ fn status(&self) -> Result<(), SpawnError> {
+ (**self).status()
+ }
+ }
+
+ impl<Sp: ?Sized + LocalSpawn> LocalSpawn for Rc<Sp> {
+ fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> {
+ (**self).spawn_local_obj(future)
+ }
+
+ fn status_local(&self) -> Result<(), SpawnError> {
+ (**self).status_local()
+ }
+ }
+
+ cfg_target_has_atomic! {
+ use alloc::{ sync::Arc };
+
+ impl<Sp: ?Sized + Spawn> Spawn for Arc<Sp> {
+ fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> {
+ (**self).spawn_obj(future)
+ }
+
+ fn status(&self) -> Result<(), SpawnError> {
+ (**self).status()
+ }
+ }
+
+ impl<Sp: ?Sized + LocalSpawn> LocalSpawn for Arc<Sp> {
+ fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> {
+ (**self).spawn_local_obj(future)
+ }
+
+ fn status_local(&self) -> Result<(), SpawnError> {
+ (**self).status_local()
+ }
+ }
+ }
+}
diff --git a/src/waker.rs b/src/waker.rs
new file mode 100644
index 0000000..635bfe8
--- /dev/null
+++ b/src/waker.rs
@@ -0,0 +1,61 @@
+use super::arc_wake::ArcWake;
+use core::mem;
+use core::task::{Waker, RawWaker, RawWakerVTable};
+use alloc::sync::Arc;
+
+pub(super) fn waker_vtable<W: ArcWake>() -> &'static RawWakerVTable {
+ &RawWakerVTable::new(
+ clone_arc_raw::<W>,
+ wake_arc_raw::<W>,
+ wake_by_ref_arc_raw::<W>,
+ drop_arc_raw::<W>,
+ )
+}
+
+/// Creates a [`Waker`] from an `Arc<impl ArcWake>`.
+///
+/// The returned [`Waker`] will call
+/// [`ArcWake.wake()`](ArcWake::wake) if awoken.
+pub fn waker<W>(wake: Arc<W>) -> Waker
+where
+ W: ArcWake,
+{
+ let ptr = Arc::into_raw(wake) as *const ();
+
+ unsafe {
+ Waker::from_raw(RawWaker::new(ptr, waker_vtable::<W>()))
+ }
+}
+
+// FIXME: panics on Arc::clone / refcount changes could wreak havoc on the
+// code here. We should guard against this by aborting.
+
+#[allow(clippy::redundant_clone)] // The clone here isn't actually redundant.
+unsafe fn increase_refcount<T: ArcWake>(data: *const ()) {
+ // Retain Arc, but don't touch refcount by wrapping in ManuallyDrop
+ let arc = mem::ManuallyDrop::new(Arc::<T>::from_raw(data as *const T));
+ // Now increase refcount, but don't drop new refcount either
+ let _arc_clone: mem::ManuallyDrop<_> = arc.clone();
+}
+
+// used by `waker_ref`
+unsafe fn clone_arc_raw<T: ArcWake>(data: *const ()) -> RawWaker {
+ increase_refcount::<T>(data);
+ RawWaker::new(data, waker_vtable::<T>())
+}
+
+unsafe fn wake_arc_raw<T: ArcWake>(data: *const ()) {
+ let arc: Arc<T> = Arc::from_raw(data as *const T);
+ ArcWake::wake(arc);
+}
+
+// used by `waker_ref`
+unsafe fn wake_by_ref_arc_raw<T: ArcWake>(data: *const ()) {
+ // Retain Arc, but don't touch refcount by wrapping in ManuallyDrop
+ let arc = mem::ManuallyDrop::new(Arc::<T>::from_raw(data as *const T));
+ ArcWake::wake_by_ref(&arc);
+}
+
+unsafe fn drop_arc_raw<T: ArcWake>(data: *const ()) {
+ drop(Arc::<T>::from_raw(data as *const T))
+}
diff --git a/src/waker_ref.rs b/src/waker_ref.rs
new file mode 100644
index 0000000..8dda499
--- /dev/null
+++ b/src/waker_ref.rs
@@ -0,0 +1,70 @@
+use super::arc_wake::{ArcWake};
+use super::waker::waker_vtable;
+use alloc::sync::Arc;
+use core::mem::ManuallyDrop;
+use core::marker::PhantomData;
+use core::ops::Deref;
+use core::task::{Waker, RawWaker};
+
+/// A [`Waker`] that is only valid for a given lifetime.
+///
+/// Note: this type implements [`Deref<Target = Waker>`](std::ops::Deref),
+/// so it can be used to get a `&Waker`.
+#[derive(Debug)]
+pub struct WakerRef<'a> {
+ waker: ManuallyDrop<Waker>,
+ _marker: PhantomData<&'a ()>,
+}
+
+impl<'a> WakerRef<'a> {
+ /// Create a new [`WakerRef`] from a [`Waker`] reference.
+ pub fn new(waker: &'a Waker) -> Self {
+ // copy the underlying (raw) waker without calling a clone,
+ // as we won't call Waker::drop either.
+ let waker = ManuallyDrop::new(unsafe { core::ptr::read(waker) });
+ WakerRef {
+ waker,
+ _marker: PhantomData,
+ }
+ }
+
+ /// Create a new [`WakerRef`] from a [`Waker`] that must not be dropped.
+ ///
+ /// Note: this if for rare cases where the caller created a [`Waker`] in
+ /// an unsafe way (that will be valid only for a lifetime to be determined
+ /// by the caller), and the [`Waker`] doesn't need to or must not be
+ /// destroyed.
+ pub fn new_unowned(waker: ManuallyDrop<Waker>) -> Self {
+ WakerRef {
+ waker,
+ _marker: PhantomData,
+ }
+ }
+}
+
+impl Deref for WakerRef<'_> {
+ type Target = Waker;
+
+ fn deref(&self) -> &Waker {
+ &self.waker
+ }
+}
+
+/// Creates a reference to a [`Waker`] from a reference to `Arc<impl ArcWake>`.
+///
+/// The resulting [`Waker`] will call
+/// [`ArcWake.wake()`](ArcWake::wake) if awoken.
+#[inline]
+pub fn waker_ref<W>(wake: &Arc<W>) -> WakerRef<'_>
+where
+ W: ArcWake
+{
+ // simply copy the pointer instead of using Arc::into_raw,
+ // as we don't actually keep a refcount by using ManuallyDrop.<
+ let ptr = (&**wake as *const W) as *const ();
+
+ let waker = ManuallyDrop::new(unsafe {
+ Waker::from_raw(RawWaker::new(ptr, waker_vtable::<W>()))
+ });
+ WakerRef::new_unowned(waker)
+}
