diff options
Diffstat (limited to 'vendor/futures-core-0.3.14')
| -rw-r--r-- | vendor/futures-core-0.3.14/.cargo-checksum.json | 1 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/Cargo.toml | 36 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/LICENSE-APACHE | 202 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/LICENSE-MIT | 26 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/src/future.rs | 105 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/src/lib.rs | 32 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/src/stream.rs | 246 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/src/task/__internal/atomic_waker.rs | 416 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/src/task/__internal/mod.rs | 4 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/src/task/mod.rs | 10 | ||||
| -rw-r--r-- | vendor/futures-core-0.3.14/src/task/poll.rs | 11 |
11 files changed, 1089 insertions, 0 deletions
diff --git a/vendor/futures-core-0.3.14/.cargo-checksum.json b/vendor/futures-core-0.3.14/.cargo-checksum.json new file mode 100644 index 00000000..471358fe --- /dev/null +++ b/vendor/futures-core-0.3.14/.cargo-checksum.json @@ -0,0 +1 @@ +{"files":{"Cargo.toml":"f8a951e3e361761a130130376db573bdfb30473ac11cdd34b754465d7361c2e2","LICENSE-APACHE":"275c491d6d1160553c32fd6127061d7f9606c3ea25abfad6ca3f6ed088785427","LICENSE-MIT":"6652c868f35dfe5e8ef636810a4e576b9d663f3a17fb0f5613ad73583e1b88fd","src/future.rs":"6af2f8f9673156b2849e367b6efdebbbd31ed5f242b9ad647c208c09f2327050","src/lib.rs":"97990a26be132054507c9afc538ac01f7fcae0283c2bafb7574f49ce23359d86","src/stream.rs":"ae0c90b45e44c0690824d84be19927d4f8e950835ff9e7586dae4f0cf6102b36","src/task/__internal/atomic_waker.rs":"cc22cf315a639bdf469538c47128113295195dba86ee325f8b017f2bf3f04a20","src/task/__internal/mod.rs":"c9dc3f5f75274b1c682f62f3cf04d2c1755aceefffd9f4bfdad59d8cbb4c4768","src/task/mod.rs":"37b7d5e26daf726911fbbd564dba31a68076b0fc8f40a1201ad6ec8ebf63cea6","src/task/poll.rs":"da03409f230c63f5226402217007d853116a9d6bf0e35572e60005acb032b6ef"},"package":"098cd1c6dda6ca01650f1a37a794245eb73181d0d4d4e955e2f3c37db7af1815"}
\ No newline at end of file diff --git a/vendor/futures-core-0.3.14/Cargo.toml b/vendor/futures-core-0.3.14/Cargo.toml new file mode 100644 index 00000000..94033e6c --- /dev/null +++ b/vendor/futures-core-0.3.14/Cargo.toml @@ -0,0 +1,36 @@ +# 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-core" +version = "0.3.14" +authors = ["Alex Crichton <alex@alexcrichton.com>"] +description = "The core traits and types in for the `futures` library.\n" +homepage = "https://rust-lang.github.io/futures-rs" +documentation = "https://docs.rs/futures-core/0.3" +license = "MIT OR Apache-2.0" +repository = "https://github.com/rust-lang/futures-rs" +[package.metadata.docs.rs] +all-features = true +rustdoc-args = ["--cfg", "docsrs"] + +[dependencies] + +[dev-dependencies] + +[features] +alloc = [] +cfg-target-has-atomic = [] +default = ["std"] +std = ["alloc"] +unstable = [] diff --git a/vendor/futures-core-0.3.14/LICENSE-APACHE b/vendor/futures-core-0.3.14/LICENSE-APACHE new file mode 100644 index 00000000..9eb0b097 --- /dev/null +++ b/vendor/futures-core-0.3.14/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. 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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/vendor/futures-core-0.3.14/LICENSE-MIT b/vendor/futures-core-0.3.14/LICENSE-MIT new file mode 100644 index 00000000..8ad082ec --- /dev/null +++ b/vendor/futures-core-0.3.14/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/vendor/futures-core-0.3.14/src/future.rs b/vendor/futures-core-0.3.14/src/future.rs new file mode 100644 index 00000000..d9327c01 --- /dev/null +++ b/vendor/futures-core-0.3.14/src/future.rs @@ -0,0 +1,105 @@ +//! Futures. + +use core::ops::DerefMut; +use core::pin::Pin; +use core::task::{Context, Poll}; + +#[doc(no_inline)] +pub use core::future::Future; + +/// An owned dynamically typed [`Future`] for use in cases where you can't +/// statically type your result or need to add some indirection. +#[cfg(feature = "alloc")] +pub type BoxFuture<'a, T> = Pin<alloc::boxed::Box<dyn Future<Output = T> + Send + 'a>>; + +/// `BoxFuture`, but without the `Send` requirement. +#[cfg(feature = "alloc")] +pub type LocalBoxFuture<'a, T> = Pin<alloc::boxed::Box<dyn Future<Output = T> + 'a>>; + +/// A future which tracks whether or not the underlying future +/// should no longer be polled. +/// +/// `is_terminated` will return `true` if a future should no longer be polled. +/// Usually, this state occurs after `poll` (or `try_poll`) returned +/// `Poll::Ready`. However, `is_terminated` may also return `true` if a future +/// has become inactive and can no longer make progress and should be ignored +/// or dropped rather than being `poll`ed again. +pub trait FusedFuture: Future { + /// Returns `true` if the underlying future should no longer be polled. + fn is_terminated(&self) -> bool; +} + +impl<F: FusedFuture + ?Sized + Unpin> FusedFuture for &mut F { + fn is_terminated(&self) -> bool { + <F as FusedFuture>::is_terminated(&**self) + } +} + +impl<P> FusedFuture for Pin<P> +where + P: DerefMut + Unpin, + P::Target: FusedFuture, +{ + fn is_terminated(&self) -> bool { + <P::Target as FusedFuture>::is_terminated(&**self) + } +} + +mod private_try_future { + use super::Future; + + pub trait Sealed {} + + impl<F, T, E> Sealed for F where F: ?Sized + Future<Output = Result<T, E>> {} +} + +/// A convenience for futures that return `Result` values that includes +/// a variety of adapters tailored to such futures. +pub trait TryFuture: Future + private_try_future::Sealed { + /// The type of successful values yielded by this future + type Ok; + + /// The type of failures yielded by this future + type Error; + + /// Poll this `TryFuture` as if it were a `Future`. + /// + /// This method is a stopgap for a compiler limitation that prevents us from + /// directly inheriting from the `Future` trait; in the future it won't be + /// needed. + fn try_poll( + self: Pin<&mut Self>, + cx: &mut Context<'_>, + ) -> Poll<Result<Self::Ok, Self::Error>>; +} + +impl<F, T, E> TryFuture for F + where F: ?Sized + Future<Output = Result<T, E>> +{ + type Ok = T; + type Error = E; + + #[inline] + fn try_poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { + self.poll(cx) + } +} + +#[cfg(feature = "alloc")] +mod if_alloc { + use alloc::boxed::Box; + use super::*; + + impl<F: FusedFuture + ?Sized + Unpin> FusedFuture for Box<F> { + fn is_terminated(&self) -> bool { + <F as FusedFuture>::is_terminated(&**self) + } + } + + #[cfg(feature = "std")] + impl<F: FusedFuture> FusedFuture for std::panic::AssertUnwindSafe<F> { + fn is_terminated(&self) -> bool { + <F as FusedFuture>::is_terminated(&**self) + } + } +} diff --git a/vendor/futures-core-0.3.14/src/lib.rs b/vendor/futures-core-0.3.14/src/lib.rs new file mode 100644 index 00000000..ec14adba --- /dev/null +++ b/vendor/futures-core-0.3.14/src/lib.rs @@ -0,0 +1,32 @@ +//! Core traits and types for asynchronous operations in Rust. + +#![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))))] + +#[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; + +pub mod future; +#[doc(hidden)] pub use self::future::{Future, FusedFuture, TryFuture}; + +pub mod stream; +#[doc(hidden)] pub use self::stream::{Stream, FusedStream, TryStream}; + +#[macro_use] +pub mod task; + +// Not public API. +#[doc(hidden)] +pub mod __private { + pub use core::task::Poll; +} diff --git a/vendor/futures-core-0.3.14/src/stream.rs b/vendor/futures-core-0.3.14/src/stream.rs new file mode 100644 index 00000000..4a13e3bd --- /dev/null +++ b/vendor/futures-core-0.3.14/src/stream.rs @@ -0,0 +1,246 @@ +//! Asynchronous streams. + +use core::ops::DerefMut; +use core::pin::Pin; +use core::task::{Context, Poll}; + +/// An owned dynamically typed [`Stream`] for use in cases where you can't +/// statically type your result or need to add some indirection. +#[cfg(feature = "alloc")] +pub type BoxStream<'a, T> = Pin<alloc::boxed::Box<dyn Stream<Item = T> + Send + 'a>>; + +/// `BoxStream`, but without the `Send` requirement. +#[cfg(feature = "alloc")] +pub type LocalBoxStream<'a, T> = Pin<alloc::boxed::Box<dyn Stream<Item = T> + 'a>>; + +/// A stream of values produced asynchronously. +/// +/// If `Future<Output = T>` is an asynchronous version of `T`, then `Stream<Item +/// = T>` is an asynchronous version of `Iterator<Item = T>`. A stream +/// represents a sequence of value-producing events that occur asynchronously to +/// the caller. +/// +/// The trait is modeled after `Future`, but allows `poll_next` to be called +/// even after a value has been produced, yielding `None` once the stream has +/// been fully exhausted. +#[must_use = "streams do nothing unless polled"] +pub trait Stream { + /// Values yielded by the stream. + type Item; + + /// Attempt to pull out the next value of this stream, registering the + /// current task for wakeup if the value is not yet available, and returning + /// `None` if the stream is exhausted. + /// + /// # Return value + /// + /// There are several possible return values, each indicating a distinct + /// stream state: + /// + /// - `Poll::Pending` means that this stream's next value is not ready + /// yet. Implementations will ensure that the current task will be notified + /// when the next value may be ready. + /// + /// - `Poll::Ready(Some(val))` means that the stream has successfully + /// produced a value, `val`, and may produce further values on subsequent + /// `poll_next` calls. + /// + /// - `Poll::Ready(None)` means that the stream has terminated, and + /// `poll_next` should not be invoked again. + /// + /// # Panics + /// + /// Once a stream has finished (returned `Ready(None)` from `poll_next`), calling its + /// `poll_next` method again may panic, block forever, or cause other kinds of + /// problems; the `Stream` trait places no requirements on the effects of + /// such a call. However, as the `poll_next` method is not marked `unsafe`, + /// Rust's usual rules apply: calls must never cause undefined behavior + /// (memory corruption, incorrect use of `unsafe` functions, or the like), + /// regardless of the stream's state. + /// + /// If this is difficult to guard against then the [`fuse`] adapter can be used + /// to ensure that `poll_next` always returns `Ready(None)` in subsequent + /// calls. + /// + /// [`fuse`]: https://docs.rs/futures/0.3/futures/stream/trait.StreamExt.html#method.fuse + fn poll_next( + self: Pin<&mut Self>, + cx: &mut Context<'_>, + ) -> Poll<Option<Self::Item>>; + + /// Returns the bounds on the remaining length of the stream. + /// + /// Specifically, `size_hint()` returns a tuple where the first element + /// is the lower bound, and the second element is the upper bound. + /// + /// The second half of the tuple that is returned is an [`Option`]`<`[`usize`]`>`. + /// A [`None`] here means that either there is no known upper bound, or the + /// upper bound is larger than [`usize`]. + /// + /// # Implementation notes + /// + /// It is not enforced that a stream implementation yields the declared + /// number of elements. A buggy stream may yield less than the lower bound + /// or more than the upper bound of elements. + /// + /// `size_hint()` is primarily intended to be used for optimizations such as + /// reserving space for the elements of the stream, but must not be + /// trusted to e.g., omit bounds checks in unsafe code. An incorrect + /// implementation of `size_hint()` should not lead to memory safety + /// violations. + /// + /// That said, the implementation should provide a correct estimation, + /// because otherwise it would be a violation of the trait's protocol. + /// + /// The default implementation returns `(0, `[`None`]`)` which is correct for any + /// stream. + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + (0, None) + } +} + +impl<S: ?Sized + Stream + Unpin> Stream for &mut S { + type Item = S::Item; + + fn poll_next( + mut self: Pin<&mut Self>, + cx: &mut Context<'_>, + ) -> Poll<Option<Self::Item>> { + S::poll_next(Pin::new(&mut **self), cx) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + (**self).size_hint() + } +} + +impl<P> Stream for Pin<P> +where + P: DerefMut + Unpin, + P::Target: Stream, +{ + type Item = <P::Target as Stream>::Item; + + fn poll_next( + self: Pin<&mut Self>, + cx: &mut Context<'_>, + ) -> Poll<Option<Self::Item>> { + self.get_mut().as_mut().poll_next(cx) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + (**self).size_hint() + } +} + +/// A stream which tracks whether or not the underlying stream +/// should no longer be polled. +/// +/// `is_terminated` will return `true` if a future should no longer be polled. +/// Usually, this state occurs after `poll_next` (or `try_poll_next`) returned +/// `Poll::Ready(None)`. However, `is_terminated` may also return `true` if a +/// stream has become inactive and can no longer make progress and should be +/// ignored or dropped rather than being polled again. +pub trait FusedStream: Stream { + /// Returns `true` if the stream should no longer be polled. + fn is_terminated(&self) -> bool; +} + +impl<F: ?Sized + FusedStream + Unpin> FusedStream for &mut F { + fn is_terminated(&self) -> bool { + <F as FusedStream>::is_terminated(&**self) + } +} + +impl<P> FusedStream for Pin<P> +where + P: DerefMut + Unpin, + P::Target: FusedStream, +{ + fn is_terminated(&self) -> bool { + <P::Target as FusedStream>::is_terminated(&**self) + } +} + +mod private_try_stream { + use super::Stream; + + pub trait Sealed {} + + impl<S, T, E> Sealed for S where S: ?Sized + Stream<Item = Result<T, E>> {} +} + +/// A convenience for streams that return `Result` values that includes +/// a variety of adapters tailored to such futures. +pub trait TryStream: Stream + private_try_stream::Sealed { + /// The type of successful values yielded by this future + type Ok; + + /// The type of failures yielded by this future + type Error; + + /// Poll this `TryStream` as if it were a `Stream`. + /// + /// This method is a stopgap for a compiler limitation that prevents us from + /// directly inheriting from the `Stream` trait; in the future it won't be + /// needed. + fn try_poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) + -> Poll<Option<Result<Self::Ok, Self::Error>>>; +} + +impl<S, T, E> TryStream for S + where S: ?Sized + Stream<Item = Result<T, E>> +{ + type Ok = T; + type Error = E; + + fn try_poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) + -> Poll<Option<Result<Self::Ok, Self::Error>>> + { + self.poll_next(cx) + } +} + +#[cfg(feature = "alloc")] +mod if_alloc { + use alloc::boxed::Box; + use super::*; + + impl<S: ?Sized + Stream + Unpin> Stream for Box<S> { + type Item = S::Item; + + fn poll_next( + mut self: Pin<&mut Self>, + cx: &mut Context<'_>, + ) -> Poll<Option<Self::Item>> { + Pin::new(&mut **self).poll_next(cx) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + (**self).size_hint() + } + } + + #[cfg(feature = "std")] + impl<S: Stream> Stream for std::panic::AssertUnwindSafe<S> { + type Item = S::Item; + + fn poll_next( + self: Pin<&mut Self>, + cx: &mut Context<'_>, + ) -> Poll<Option<S::Item>> { + unsafe { self.map_unchecked_mut(|x| &mut x.0) }.poll_next(cx) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + self.0.size_hint() + } + } + + impl<S: ?Sized + FusedStream + Unpin> FusedStream for Box<S> { + fn is_terminated(&self) -> bool { + <S as FusedStream>::is_terminated(&**self) + } + } +} diff --git a/vendor/futures-core-0.3.14/src/task/__internal/atomic_waker.rs b/vendor/futures-core-0.3.14/src/task/__internal/atomic_waker.rs new file mode 100644 index 00000000..213355bc --- /dev/null +++ b/vendor/futures-core-0.3.14/src/task/__internal/atomic_waker.rs @@ -0,0 +1,416 @@ +use core::cell::UnsafeCell; +use core::fmt; +use core::sync::atomic::AtomicUsize; +use core::sync::atomic::Ordering::{Acquire, Release, AcqRel}; +use core::task::Waker; + +/// A synchronization primitive for task wakeup. +/// +/// Sometimes the task interested in a given event will change over time. +/// An `AtomicWaker` can coordinate concurrent notifications with the consumer +/// potentially "updating" the underlying task to wake up. This is useful in +/// scenarios where a computation completes in another thread and wants to +/// notify the consumer, but the consumer is in the process of being migrated to +/// a new logical task. +/// +/// Consumers should call `register` before checking the result of a computation +/// and producers should call `wake` after producing the computation (this +/// differs from the usual `thread::park` pattern). It is also permitted for +/// `wake` to be called **before** `register`. This results in a no-op. +/// +/// A single `AtomicWaker` may be reused for any number of calls to `register` or +/// `wake`. +/// +/// # Memory ordering +/// +/// Calling `register` "acquires" all memory "released" by calls to `wake` +/// before the call to `register`. Later calls to `wake` will wake the +/// registered waker (on contention this wake might be triggered in `register`). +/// +/// For concurrent calls to `register` (should be avoided) the ordering is only +/// guaranteed for the winning call. +/// +/// # Examples +/// +/// Here is a simple example providing a `Flag` that can be signalled manually +/// when it is ready. +/// +/// ``` +/// use futures::future::Future; +/// use futures::task::{Context, Poll, AtomicWaker}; +/// use std::sync::Arc; +/// use std::sync::atomic::AtomicBool; +/// use std::sync::atomic::Ordering::Relaxed; +/// use std::pin::Pin; +/// +/// struct Inner { +/// waker: AtomicWaker, +/// set: AtomicBool, +/// } +/// +/// #[derive(Clone)] +/// struct Flag(Arc<Inner>); +/// +/// impl Flag { +/// pub fn new() -> Self { +/// Self(Arc::new(Inner { +/// waker: AtomicWaker::new(), +/// set: AtomicBool::new(false), +/// })) +/// } +/// +/// pub fn signal(&self) { +/// self.0.set.store(true, Relaxed); +/// self.0.waker.wake(); +/// } +/// } +/// +/// impl Future for Flag { +/// type Output = (); +/// +/// fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> { +/// // quick check to avoid registration if already done. +/// if self.0.set.load(Relaxed) { +/// return Poll::Ready(()); +/// } +/// +/// self.0.waker.register(cx.waker()); +/// +/// // Need to check condition **after** `register` to avoid a race +/// // condition that would result in lost notifications. +/// if self.0.set.load(Relaxed) { +/// Poll::Ready(()) +/// } else { +/// Poll::Pending +/// } +/// } +/// } +/// ``` +pub struct AtomicWaker { + state: AtomicUsize, + waker: UnsafeCell<Option<Waker>>, +} + +// `AtomicWaker` is a multi-consumer, single-producer transfer cell. The cell +// stores a `Waker` value produced by calls to `register` and many threads can +// race to take the waker (to wake it) by calling `wake`. +// +// If a new `Waker` instance is produced by calling `register` before an +// existing one is consumed, then the existing one is overwritten. +// +// While `AtomicWaker` is single-producer, the implementation ensures memory +// safety. In the event of concurrent calls to `register`, there will be a +// single winner whose waker will get stored in the cell. The losers will not +// have their tasks woken. As such, callers should ensure to add synchronization +// to calls to `register`. +// +// The implementation uses a single `AtomicUsize` value to coordinate access to +// the `Waker` cell. There are two bits that are operated on independently. +// These are represented by `REGISTERING` and `WAKING`. +// +// The `REGISTERING` bit is set when a producer enters the critical section. The +// `WAKING` bit is set when a consumer enters the critical section. Neither bit +// being set is represented by `WAITING`. +// +// A thread obtains an exclusive lock on the waker cell by transitioning the +// state from `WAITING` to `REGISTERING` or `WAKING`, depending on the operation +// the thread wishes to perform. When this |