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-rw-r--r--third_party/rust/crossbeam-queue/.cargo-checksum.json1
-rw-r--r--third_party/rust/crossbeam-queue/CHANGELOG.md68
-rw-r--r--third_party/rust/crossbeam-queue/Cargo.toml52
-rw-r--r--third_party/rust/crossbeam-queue/LICENSE-APACHE201
-rw-r--r--third_party/rust/crossbeam-queue/LICENSE-MIT27
-rw-r--r--third_party/rust/crossbeam-queue/README.md54
-rw-r--r--third_party/rust/crossbeam-queue/build-common.rs13
-rw-r--r--third_party/rust/crossbeam-queue/build.rs41
-rw-r--r--third_party/rust/crossbeam-queue/no_atomic.rs82
-rw-r--r--third_party/rust/crossbeam-queue/src/array_queue.rs536
-rw-r--r--third_party/rust/crossbeam-queue/src/lib.rs34
-rw-r--r--third_party/rust/crossbeam-queue/src/seg_queue.rs547
-rw-r--r--third_party/rust/crossbeam-queue/tests/array_queue.rs374
-rw-r--r--third_party/rust/crossbeam-queue/tests/seg_queue.rs195
14 files changed, 2225 insertions, 0 deletions
diff --git a/third_party/rust/crossbeam-queue/.cargo-checksum.json b/third_party/rust/crossbeam-queue/.cargo-checksum.json
new file mode 100644
index 0000000000..be7a7c7163
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"CHANGELOG.md":"2821f0a64845f2a8046b8c78c40c31f5d67c6b89ab94ea56951aa7a30b27cdab","Cargo.toml":"146684572cc251b02395a6e6112b3a9a3e00ae77faf125f97dc9853eece16123","LICENSE-APACHE":"a60eea817514531668d7e00765731449fe14d059d3249e0bc93b36de45f759f2","LICENSE-MIT":"5734ed989dfca1f625b40281ee9f4530f91b2411ec01cb748223e7eb87e201ab","README.md":"43d55c46767a4f4a78f6df4324dafd702723a4986f5b13b18f3400ee56d6c8c6","build-common.rs":"502cb7494549bed6fa10ac7bea36e880eeb60290dc69b679ac5c92b376469562","build.rs":"466741d1347312cc8d7587dc1730c8fe8e8797813f5cea81ac696dd665cf5656","no_atomic.rs":"3314524d2afa0360c947455a6e6566fb54ebf909c99479ca3b7435741fd3293e","src/array_queue.rs":"066305ca224ffff1626d3d2361a315fea6d50fb25ce60bbe31bb06e749f1bb12","src/lib.rs":"effccc001c5168217291e435ae79f4889495cb943a6720d1e73e65b64831e4ed","src/seg_queue.rs":"7cfc4aa1a681192ccec964880771a6e08e945a38ccf8be4730ed89de3dc48c1a","tests/array_queue.rs":"426dd0ff6698bd63108b3a567703ec2e635bce0f337134116e237b11925a7716","tests/seg_queue.rs":"7abb1008638a947440b201e1ad15f273020730715fae1f876407f1b967ae28ff"},"package":"d1cfb3ea8a53f37c40dea2c7bedcbd88bdfae54f5e2175d6ecaff1c988353add"} \ No newline at end of file
diff --git a/third_party/rust/crossbeam-queue/CHANGELOG.md b/third_party/rust/crossbeam-queue/CHANGELOG.md
new file mode 100644
index 0000000000..79aaacdccd
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/CHANGELOG.md
@@ -0,0 +1,68 @@
+# Version 0.3.8
+
+- Fix build script bug introduced in 0.3.7. (#932)
+
+# Version 0.3.7
+
+**Note:** This release has been yanked due to regression fixed in 0.3.8.
+
+- Improve support for custom targets. (#922)
+
+# Version 0.3.6
+
+- Bump the minimum supported Rust version to 1.38. (#877)
+
+# Version 0.3.5
+
+- Add `ArrayQueue::force_push`. (#789)
+
+# Version 0.3.4
+
+- Implement `IntoIterator` for `ArrayQueue` and `SegQueue`. (#772)
+
+# Version 0.3.3
+
+- Fix stacked borrows violation in `ArrayQueue` when `-Zmiri-tag-raw-pointers` is enabled. (#763)
+
+# Version 0.3.2
+
+- Support targets that do not have atomic CAS on stable Rust. (#698)
+
+# Version 0.3.1
+
+- Make `SegQueue::new` const fn. (#584)
+- Change license to "MIT OR Apache-2.0".
+
+# Version 0.3.0
+
+- Bump the minimum supported Rust version to 1.36.
+- Remove `PushError` and `PopError`.
+
+# Version 0.2.3
+
+- Fix bug in release (yanking 0.2.2)
+
+# Version 0.2.2
+
+- Fix unsoundness issues by adopting `MaybeUninit`. (#458)
+
+# Version 0.2.1
+
+- Add `no_std` support.
+
+# Version 0.2.0
+
+- Bump the minimum required version to 1.28.
+- Bump `crossbeam-utils` to `0.7`.
+
+# Version 0.1.2
+
+- Update `crossbeam-utils` to `0.6.5`.
+
+# Version 0.1.1
+
+- Update `crossbeam-utils` to `0.6.4`.
+
+# Version 0.1.0
+
+- Initial version with `ArrayQueue` and `SegQueue`.
diff --git a/third_party/rust/crossbeam-queue/Cargo.toml b/third_party/rust/crossbeam-queue/Cargo.toml
new file mode 100644
index 0000000000..2b775fbc6e
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/Cargo.toml
@@ -0,0 +1,52 @@
+# 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 are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+rust-version = "1.38"
+name = "crossbeam-queue"
+version = "0.3.8"
+description = "Concurrent queues"
+homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-queue"
+readme = "README.md"
+keywords = [
+ "queue",
+ "mpmc",
+ "lock-free",
+ "producer",
+ "consumer",
+]
+categories = [
+ "concurrency",
+ "data-structures",
+ "no-std",
+]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/crossbeam-rs/crossbeam"
+
+[dependencies.cfg-if]
+version = "1"
+
+[dependencies.crossbeam-utils]
+version = "0.8.5"
+default-features = false
+
+[dev-dependencies.rand]
+version = "0.8"
+
+[features]
+alloc = []
+default = ["std"]
+nightly = ["crossbeam-utils/nightly"]
+std = [
+ "alloc",
+ "crossbeam-utils/std",
+]
diff --git a/third_party/rust/crossbeam-queue/LICENSE-APACHE b/third_party/rust/crossbeam-queue/LICENSE-APACHE
new file mode 100644
index 0000000000..16fe87b06e
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/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. Definitions.
+
+ "License" shall mean the terms and conditions for use, reproduction,
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+ any Contribution intentionally submitted for inclusion in the Work
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+ Contributor provides its Contributions) on an "AS IS" BASIS,
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+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
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+ incidental, or consequential damages of any character arising as a
+ result of this License or out of the use or inability to use the
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+ 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.
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+ To apply the Apache License to your work, attach the following
+ boilerplate notice, with the fields enclosed by brackets "[]"
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+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
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+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/third_party/rust/crossbeam-queue/LICENSE-MIT b/third_party/rust/crossbeam-queue/LICENSE-MIT
new file mode 100644
index 0000000000..068d491fd5
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/LICENSE-MIT
@@ -0,0 +1,27 @@
+The MIT License (MIT)
+
+Copyright (c) 2019 The Crossbeam Project Developers
+
+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/third_party/rust/crossbeam-queue/README.md b/third_party/rust/crossbeam-queue/README.md
new file mode 100644
index 0000000000..85671ef174
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/README.md
@@ -0,0 +1,54 @@
+# Crossbeam Queue
+
+[![Build Status](https://github.com/crossbeam-rs/crossbeam/workflows/CI/badge.svg)](
+https://github.com/crossbeam-rs/crossbeam/actions)
+[![License](https://img.shields.io/badge/license-MIT_OR_Apache--2.0-blue.svg)](
+https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-queue#license)
+[![Cargo](https://img.shields.io/crates/v/crossbeam-queue.svg)](
+https://crates.io/crates/crossbeam-queue)
+[![Documentation](https://docs.rs/crossbeam-queue/badge.svg)](
+https://docs.rs/crossbeam-queue)
+[![Rust 1.38+](https://img.shields.io/badge/rust-1.38+-lightgray.svg)](
+https://www.rust-lang.org)
+[![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ)
+
+This crate provides concurrent queues that can be shared among threads:
+
+* [`ArrayQueue`], a bounded MPMC queue that allocates a fixed-capacity buffer on construction.
+* [`SegQueue`], an unbounded MPMC queue that allocates small buffers, segments, on demand.
+
+Everything in this crate can be used in `no_std` environments, provided that `alloc` feature is
+enabled.
+
+[`ArrayQueue`]: https://docs.rs/crossbeam-queue/*/crossbeam_queue/struct.ArrayQueue.html
+[`SegQueue`]: https://docs.rs/crossbeam-queue/*/crossbeam_queue/struct.SegQueue.html
+
+## Usage
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+crossbeam-queue = "0.3"
+```
+
+## Compatibility
+
+Crossbeam Queue supports stable Rust releases going back at least six months,
+and every time the minimum supported Rust version is increased, a new minor
+version is released. Currently, the minimum supported Rust version is 1.38.
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+#### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.
diff --git a/third_party/rust/crossbeam-queue/build-common.rs b/third_party/rust/crossbeam-queue/build-common.rs
new file mode 100644
index 0000000000..e91bb4d471
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/build-common.rs
@@ -0,0 +1,13 @@
+// The target triplets have the form of 'arch-vendor-system'.
+//
+// When building for Linux (e.g. the 'system' part is
+// 'linux-something'), replace the vendor with 'unknown'
+// so that mapping to rust standard targets happens correctly.
+fn convert_custom_linux_target(target: String) -> String {
+ let mut parts: Vec<&str> = target.split('-').collect();
+ let system = parts.get(2);
+ if system == Some(&"linux") {
+ parts[1] = "unknown";
+ };
+ parts.join("-")
+}
diff --git a/third_party/rust/crossbeam-queue/build.rs b/third_party/rust/crossbeam-queue/build.rs
new file mode 100644
index 0000000000..6975dd8c2c
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/build.rs
@@ -0,0 +1,41 @@
+// The rustc-cfg listed below are considered public API, but it is *unstable*
+// and outside of the normal semver guarantees:
+//
+// - `crossbeam_no_atomic_cas`
+// Assume the target does *not* support atomic CAS operations.
+// This is usually detected automatically by the build script, but you may
+// need to enable it manually when building for custom targets or using
+// non-cargo build systems that don't run the build script.
+//
+// With the exceptions mentioned above, the rustc-cfg emitted by the build
+// script are *not* public API.
+
+#![warn(rust_2018_idioms)]
+
+use std::env;
+
+include!("no_atomic.rs");
+include!("build-common.rs");
+
+fn main() {
+ let target = match env::var("TARGET") {
+ Ok(target) => convert_custom_linux_target(target),
+ Err(e) => {
+ println!(
+ "cargo:warning={}: unable to get TARGET environment variable: {}",
+ env!("CARGO_PKG_NAME"),
+ e
+ );
+ return;
+ }
+ };
+
+ // Note that this is `no_`*, not `has_*`. This allows treating as the latest
+ // stable rustc is used when the build script doesn't run. This is useful
+ // for non-cargo build systems that don't run the build script.
+ if NO_ATOMIC_CAS.contains(&&*target) {
+ println!("cargo:rustc-cfg=crossbeam_no_atomic_cas");
+ }
+
+ println!("cargo:rerun-if-changed=no_atomic.rs");
+}
diff --git a/third_party/rust/crossbeam-queue/no_atomic.rs b/third_party/rust/crossbeam-queue/no_atomic.rs
new file mode 100644
index 0000000000..8ce0d311fb
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/no_atomic.rs
@@ -0,0 +1,82 @@
+// This file is @generated by no_atomic.sh.
+// It is not intended for manual editing.
+
+const NO_ATOMIC_CAS: &[&str] = &[
+ "armv4t-none-eabi",
+ "armv5te-none-eabi",
+ "avr-unknown-gnu-atmega328",
+ "bpfeb-unknown-none",
+ "bpfel-unknown-none",
+ "msp430-none-elf",
+ "riscv32i-unknown-none-elf",
+ "riscv32im-unknown-none-elf",
+ "riscv32imc-unknown-none-elf",
+ "thumbv4t-none-eabi",
+ "thumbv5te-none-eabi",
+ "thumbv6m-none-eabi",
+];
+
+#[allow(dead_code)] // Only crossbeam-utils uses this.
+const NO_ATOMIC_64: &[&str] = &[
+ "arm-linux-androideabi",
+ "armebv7r-none-eabi",
+ "armebv7r-none-eabihf",
+ "armv4t-none-eabi",
+ "armv4t-unknown-linux-gnueabi",
+ "armv5te-none-eabi",
+ "armv5te-unknown-linux-gnueabi",
+ "armv5te-unknown-linux-musleabi",
+ "armv5te-unknown-linux-uclibceabi",
+ "armv6k-nintendo-3ds",
+ "armv7r-none-eabi",
+ "armv7r-none-eabihf",
+ "avr-unknown-gnu-atmega328",
+ "hexagon-unknown-linux-musl",
+ "m68k-unknown-linux-gnu",
+ "mips-unknown-linux-gnu",
+ "mips-unknown-linux-musl",
+ "mips-unknown-linux-uclibc",
+ "mipsel-sony-psp",
+ "mipsel-sony-psx",
+ "mipsel-unknown-linux-gnu",
+ "mipsel-unknown-linux-musl",
+ "mipsel-unknown-linux-uclibc",
+ "mipsel-unknown-none",
+ "mipsisa32r6-unknown-linux-gnu",
+ "mipsisa32r6el-unknown-linux-gnu",
+ "msp430-none-elf",
+ "powerpc-unknown-freebsd",
+ "powerpc-unknown-linux-gnu",
+ "powerpc-unknown-linux-gnuspe",
+ "powerpc-unknown-linux-musl",
+ "powerpc-unknown-netbsd",
+ "powerpc-unknown-openbsd",
+ "powerpc-wrs-vxworks",
+ "powerpc-wrs-vxworks-spe",
+ "riscv32gc-unknown-linux-gnu",
+ "riscv32gc-unknown-linux-musl",
+ "riscv32i-unknown-none-elf",
+ "riscv32im-unknown-none-elf",
+ "riscv32imac-unknown-none-elf",
+ "riscv32imac-unknown-xous-elf",
+ "riscv32imc-unknown-none-elf",
+ "thumbv4t-none-eabi",
+ "thumbv5te-none-eabi",
+ "thumbv6m-none-eabi",
+ "thumbv7em-none-eabi",
+ "thumbv7em-none-eabihf",
+ "thumbv7m-none-eabi",
+ "thumbv8m.base-none-eabi",
+ "thumbv8m.main-none-eabi",
+ "thumbv8m.main-none-eabihf",
+];
+
+#[allow(dead_code)] // Only crossbeam-utils uses this.
+const NO_ATOMIC: &[&str] = &[
+ "avr-unknown-gnu-atmega328",
+ "mipsel-sony-psx",
+ "msp430-none-elf",
+ "riscv32i-unknown-none-elf",
+ "riscv32im-unknown-none-elf",
+ "riscv32imc-unknown-none-elf",
+];
diff --git a/third_party/rust/crossbeam-queue/src/array_queue.rs b/third_party/rust/crossbeam-queue/src/array_queue.rs
new file mode 100644
index 0000000000..e07fde8a8a
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/src/array_queue.rs
@@ -0,0 +1,536 @@
+//! The implementation is based on Dmitry Vyukov's bounded MPMC queue.
+//!
+//! Source:
+//! - <http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue>
+
+use alloc::boxed::Box;
+use core::cell::UnsafeCell;
+use core::fmt;
+use core::mem::MaybeUninit;
+use core::sync::atomic::{self, AtomicUsize, Ordering};
+
+use crossbeam_utils::{Backoff, CachePadded};
+
+/// A slot in a queue.
+struct Slot<T> {
+ /// The current stamp.
+ ///
+ /// If the stamp equals the tail, this node will be next written to. If it equals head + 1,
+ /// this node will be next read from.
+ stamp: AtomicUsize,
+
+ /// The value in this slot.
+ value: UnsafeCell<MaybeUninit<T>>,
+}
+
+/// A bounded multi-producer multi-consumer queue.
+///
+/// This queue allocates a fixed-capacity buffer on construction, which is used to store pushed
+/// elements. The queue cannot hold more elements than the buffer allows. Attempting to push an
+/// element into a full queue will fail. Alternatively, [`force_push`] makes it possible for
+/// this queue to be used as a ring-buffer. Having a buffer allocated upfront makes this queue
+/// a bit faster than [`SegQueue`].
+///
+/// [`force_push`]: ArrayQueue::force_push
+/// [`SegQueue`]: super::SegQueue
+///
+/// # Examples
+///
+/// ```
+/// use crossbeam_queue::ArrayQueue;
+///
+/// let q = ArrayQueue::new(2);
+///
+/// assert_eq!(q.push('a'), Ok(()));
+/// assert_eq!(q.push('b'), Ok(()));
+/// assert_eq!(q.push('c'), Err('c'));
+/// assert_eq!(q.pop(), Some('a'));
+/// ```
+pub struct ArrayQueue<T> {
+ /// The head of the queue.
+ ///
+ /// This value is a "stamp" consisting of an index into the buffer and a lap, but packed into a
+ /// single `usize`. The lower bits represent the index, while the upper bits represent the lap.
+ ///
+ /// Elements are popped from the head of the queue.
+ head: CachePadded<AtomicUsize>,
+
+ /// The tail of the queue.
+ ///
+ /// This value is a "stamp" consisting of an index into the buffer and a lap, but packed into a
+ /// single `usize`. The lower bits represent the index, while the upper bits represent the lap.
+ ///
+ /// Elements are pushed into the tail of the queue.
+ tail: CachePadded<AtomicUsize>,
+
+ /// The buffer holding slots.
+ buffer: Box<[Slot<T>]>,
+
+ /// The queue capacity.
+ cap: usize,
+
+ /// A stamp with the value of `{ lap: 1, index: 0 }`.
+ one_lap: usize,
+}
+
+unsafe impl<T: Send> Sync for ArrayQueue<T> {}
+unsafe impl<T: Send> Send for ArrayQueue<T> {}
+
+impl<T> ArrayQueue<T> {
+ /// Creates a new bounded queue with the given capacity.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the capacity is zero.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::ArrayQueue;
+ ///
+ /// let q = ArrayQueue::<i32>::new(100);
+ /// ```
+ pub fn new(cap: usize) -> ArrayQueue<T> {
+ assert!(cap > 0, "capacity must be non-zero");
+
+ // Head is initialized to `{ lap: 0, index: 0 }`.
+ // Tail is initialized to `{ lap: 0, index: 0 }`.
+ let head = 0;
+ let tail = 0;
+
+ // Allocate a buffer of `cap` slots initialized
+ // with stamps.
+ let buffer: Box<[Slot<T>]> = (0..cap)
+ .map(|i| {
+ // Set the stamp to `{ lap: 0, index: i }`.
+ Slot {
+ stamp: AtomicUsize::new(i),
+ value: UnsafeCell::new(MaybeUninit::uninit()),
+ }
+ })
+ .collect();
+
+ // One lap is the smallest power of two greater than `cap`.
+ let one_lap = (cap + 1).next_power_of_two();
+
+ ArrayQueue {
+ buffer,
+ cap,
+ one_lap,
+ head: CachePadded::new(AtomicUsize::new(head)),
+ tail: CachePadded::new(AtomicUsize::new(tail)),
+ }
+ }
+
+ fn push_or_else<F>(&self, mut value: T, f: F) -> Result<(), T>
+ where
+ F: Fn(T, usize, usize, &Slot<T>) -> Result<T, T>,
+ {
+ let backoff = Backoff::new();
+ let mut tail = self.tail.load(Ordering::Relaxed);
+
+ loop {
+ // Deconstruct the tail.
+ let index = tail & (self.one_lap - 1);
+ let lap = tail & !(self.one_lap - 1);
+
+ let new_tail = if index + 1 < self.cap {
+ // Same lap, incremented index.
+ // Set to `{ lap: lap, index: index + 1 }`.
+ tail + 1
+ } else {
+ // One lap forward, index wraps around to zero.
+ // Set to `{ lap: lap.wrapping_add(1), index: 0 }`.
+ lap.wrapping_add(self.one_lap)
+ };
+
+ // Inspect the corresponding slot.
+ debug_assert!(index < self.buffer.len());
+ let slot = unsafe { self.buffer.get_unchecked(index) };
+ let stamp = slot.stamp.load(Ordering::Acquire);
+
+ // If the tail and the stamp match, we may attempt to push.
+ if tail == stamp {
+ // Try moving the tail.
+ match self.tail.compare_exchange_weak(
+ tail,
+ new_tail,
+ Ordering::SeqCst,
+ Ordering::Relaxed,
+ ) {
+ Ok(_) => {
+ // Write the value into the slot and update the stamp.
+ unsafe {
+ slot.value.get().write(MaybeUninit::new(value));
+ }
+ slot.stamp.store(tail + 1, Ordering::Release);
+ return Ok(());
+ }
+ Err(t) => {
+ tail = t;
+ backoff.spin();
+ }
+ }
+ } else if stamp.wrapping_add(self.one_lap) == tail + 1 {
+ atomic::fence(Ordering::SeqCst);
+ value = f(value, tail, new_tail, slot)?;
+ backoff.spin();
+ tail = self.tail.load(Ordering::Relaxed);
+ } else {
+ // Snooze because we need to wait for the stamp to get updated.
+ backoff.snooze();
+ tail = self.tail.load(Ordering::Relaxed);
+ }
+ }
+ }
+
+ /// Attempts to push an element into the queue.
+ ///
+ /// If the queue is full, the element is returned back as an error.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::ArrayQueue;
+ ///
+ /// let q = ArrayQueue::new(1);
+ ///
+ /// assert_eq!(q.push(10), Ok(()));
+ /// assert_eq!(q.push(20), Err(20));
+ /// ```
+ pub fn push(&self, value: T) -> Result<(), T> {
+ self.push_or_else(value, |v, tail, _, _| {
+ let head = self.head.load(Ordering::Relaxed);
+
+ // If the head lags one lap behind the tail as well...
+ if head.wrapping_add(self.one_lap) == tail {
+ // ...then the queue is full.
+ Err(v)
+ } else {
+ Ok(v)
+ }
+ })
+ }
+
+ /// Pushes an element into the queue, replacing the oldest element if necessary.
+ ///
+ /// If the queue is full, the oldest element is replaced and returned,
+ /// otherwise `None` is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::ArrayQueue;
+ ///
+ /// let q = ArrayQueue::new(2);
+ ///
+ /// assert_eq!(q.force_push(10), None);
+ /// assert_eq!(q.force_push(20), None);
+ /// assert_eq!(q.force_push(30), Some(10));
+ /// assert_eq!(q.pop(), Some(20));
+ /// ```
+ pub fn force_push(&self, value: T) -> Option<T> {
+ self.push_or_else(value, |v, tail, new_tail, slot| {
+ let head = tail.wrapping_sub(self.one_lap);
+ let new_head = new_tail.wrapping_sub(self.one_lap);
+
+ // Try moving the head.
+ if self
+ .head
+ .compare_exchange_weak(head, new_head, Ordering::SeqCst, Ordering::Relaxed)
+ .is_ok()
+ {
+ // Move the tail.
+ self.tail.store(new_tail, Ordering::SeqCst);
+
+ // Swap the previous value.
+ let old = unsafe { slot.value.get().replace(MaybeUninit::new(v)).assume_init() };
+
+ // Update the stamp.
+ slot.stamp.store(tail + 1, Ordering::Release);
+
+ Err(old)
+ } else {
+ Ok(v)
+ }
+ })
+ .err()
+ }
+
+ /// Attempts to pop an element from the queue.
+ ///
+ /// If the queue is empty, `None` is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::ArrayQueue;
+ ///
+ /// let q = ArrayQueue::new(1);
+ /// assert_eq!(q.push(10), Ok(()));
+ ///
+ /// assert_eq!(q.pop(), Some(10));
+ /// assert!(q.pop().is_none());
+ /// ```
+ pub fn pop(&self) -> Option<T> {
+ let backoff = Backoff::new();
+ let mut head = self.head.load(Ordering::Relaxed);
+
+ loop {
+ // Deconstruct the head.
+ let index = head & (self.one_lap - 1);
+ let lap = head & !(self.one_lap - 1);
+
+ // Inspect the corresponding slot.
+ debug_assert!(index < self.buffer.len());
+ let slot = unsafe { self.buffer.get_unchecked(index) };
+ let stamp = slot.stamp.load(Ordering::Acquire);
+
+ // If the the stamp is ahead of the head by 1, we may attempt to pop.
+ if head + 1 == stamp {
+ let new = if index + 1 < self.cap {
+ // Same lap, incremented index.
+ // Set to `{ lap: lap, index: index + 1 }`.
+ head + 1
+ } else {
+ // One lap forward, index wraps around to zero.
+ // Set to `{ lap: lap.wrapping_add(1), index: 0 }`.
+ lap.wrapping_add(self.one_lap)
+ };
+
+ // Try moving the head.
+ match self.head.compare_exchange_weak(
+ head,
+ new,
+ Ordering::SeqCst,
+ Ordering::Relaxed,
+ ) {
+ Ok(_) => {
+ // Read the value from the slot and update the stamp.
+ let msg = unsafe { slot.value.get().read().assume_init() };
+ slot.stamp
+ .store(head.wrapping_add(self.one_lap), Ordering::Release);
+ return Some(msg);
+ }
+ Err(h) => {
+ head = h;
+ backoff.spin();
+ }
+ }
+ } else if stamp == head {
+ atomic::fence(Ordering::SeqCst);
+ let tail = self.tail.load(Ordering::Relaxed);
+
+ // If the tail equals the head, that means the channel is empty.
+ if tail == head {
+ return None;
+ }
+
+ backoff.spin();
+ head = self.head.load(Ordering::Relaxed);
+ } else {
+ // Snooze because we need to wait for the stamp to get updated.
+ backoff.snooze();
+ head = self.head.load(Ordering::Relaxed);
+ }
+ }
+ }
+
+ /// Returns the capacity of the queue.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::ArrayQueue;
+ ///
+ /// let q = ArrayQueue::<i32>::new(100);
+ ///
+ /// assert_eq!(q.capacity(), 100);
+ /// ```
+ pub fn capacity(&self) -> usize {
+ self.cap
+ }
+
+ /// Returns `true` if the queue is empty.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::ArrayQueue;
+ ///
+ /// let q = ArrayQueue::new(100);
+ ///
+ /// assert!(q.is_empty());
+ /// q.push(1).unwrap();
+ /// assert!(!q.is_empty());
+ /// ```
+ pub fn is_empty(&self) -> bool {
+ let head = self.head.load(Ordering::SeqCst);
+ let tail = self.tail.load(Ordering::SeqCst);
+
+ // Is the tail lagging one lap behind head?
+ // Is the tail equal to the head?
+ //
+ // Note: If the head changes just before we load the tail, that means there was a moment
+ // when the channel was not empty, so it is safe to just return `false`.
+ tail == head
+ }
+
+ /// Returns `true` if the queue is full.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::ArrayQueue;
+ ///
+ /// let q = ArrayQueue::new(1);
+ ///
+ /// assert!(!q.is_full());
+ /// q.push(1).unwrap();
+ /// assert!(q.is_full());
+ /// ```
+ pub fn is_full(&self) -> bool {
+ let tail = self.tail.load(Ordering::SeqCst);
+ let head = self.head.load(Ordering::SeqCst);
+
+ // Is the head lagging one lap behind tail?
+ //
+ // Note: If the tail changes just before we load the head, that means there was a moment
+ // when the queue was not full, so it is safe to just return `false`.
+ head.wrapping_add(self.one_lap) == tail
+ }
+
+ /// Returns the number of elements in the queue.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::ArrayQueue;
+ ///
+ /// let q = ArrayQueue::new(100);
+ /// assert_eq!(q.len(), 0);
+ ///
+ /// q.push(10).unwrap();
+ /// assert_eq!(q.len(), 1);
+ ///
+ /// q.push(20).unwrap();
+ /// assert_eq!(q.len(), 2);
+ /// ```
+ pub fn len(&self) -> usize {
+ loop {
+ // Load the tail, then load the head.
+ let tail = self.tail.load(Ordering::SeqCst);
+ let head = self.head.load(Ordering::SeqCst);
+
+ // If the tail didn't change, we've got consistent values to work with.
+ if self.tail.load(Ordering::SeqCst) == tail {
+ let hix = head & (self.one_lap - 1);
+ let tix = tail & (self.one_lap - 1);
+
+ return if hix < tix {
+ tix - hix
+ } else if hix > tix {
+ self.cap - hix + tix
+ } else if tail == head {
+ 0
+ } else {
+ self.cap
+ };
+ }
+ }
+ }
+}
+
+impl<T> Drop for ArrayQueue<T> {
+ fn drop(&mut self) {
+ // Get the index of the head.
+ let head = *self.head.get_mut();
+ let tail = *self.tail.get_mut();
+
+ let hix = head & (self.one_lap - 1);
+ let tix = tail & (self.one_lap - 1);
+
+ let len = if hix < tix {
+ tix - hix
+ } else if hix > tix {
+ self.cap - hix + tix
+ } else if tail == head {
+ 0
+ } else {
+ self.cap
+ };
+
+ // Loop over all slots that hold a message and drop them.
+ for i in 0..len {
+ // Compute the index of the next slot holding a message.
+ let index = if hix + i < self.cap {
+ hix + i
+ } else {
+ hix + i - self.cap
+ };
+
+ unsafe {
+ debug_assert!(index < self.buffer.len());
+ let slot = self.buffer.get_unchecked_mut(index);
+ let value = &mut *slot.value.get();
+ value.as_mut_ptr().drop_in_place();
+ }
+ }
+ }
+}
+
+impl<T> fmt::Debug for ArrayQueue<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.pad("ArrayQueue { .. }")
+ }
+}
+
+impl<T> IntoIterator for ArrayQueue<T> {
+ type Item = T;
+
+ type IntoIter = IntoIter<T>;
+
+ fn into_iter(self) -> Self::IntoIter {
+ IntoIter { value: self }
+ }
+}
+
+#[derive(Debug)]
+pub struct IntoIter<T> {
+ value: ArrayQueue<T>,
+}
+
+impl<T> Iterator for IntoIter<T> {
+ type Item = T;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ let value = &mut self.value;
+ let head = *value.head.get_mut();
+ if value.head.get_mut() != value.tail.get_mut() {
+ let index = head & (value.one_lap - 1);
+ let lap = head & !(value.one_lap - 1);
+ // SAFETY: We have mutable access to this, so we can read without
+ // worrying about concurrency. Furthermore, we know this is
+ // initialized because it is the value pointed at by `value.head`
+ // and this is a non-empty queue.
+ let val = unsafe {
+ debug_assert!(index < value.buffer.len());
+ let slot = value.buffer.get_unchecked_mut(index);
+ slot.value.get().read().assume_init()
+ };
+ let new = if index + 1 < value.cap {
+ // Same lap, incremented index.
+ // Set to `{ lap: lap, index: index + 1 }`.
+ head + 1
+ } else {
+ // One lap forward, index wraps around to zero.
+ // Set to `{ lap: lap.wrapping_add(1), index: 0 }`.
+ lap.wrapping_add(value.one_lap)
+ };
+ *value.head.get_mut() = new;
+ Option::Some(val)
+ } else {
+ Option::None
+ }
+ }
+}
diff --git a/third_party/rust/crossbeam-queue/src/lib.rs b/third_party/rust/crossbeam-queue/src/lib.rs
new file mode 100644
index 0000000000..846d7c2e1b
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/src/lib.rs
@@ -0,0 +1,34 @@
+//! Concurrent queues.
+//!
+//! This crate provides concurrent queues that can be shared among threads:
+//!
+//! * [`ArrayQueue`], a bounded MPMC queue that allocates a fixed-capacity buffer on construction.
+//! * [`SegQueue`], an unbounded MPMC queue that allocates small buffers, segments, on demand.
+
+#![doc(test(
+ no_crate_inject,
+ attr(
+ deny(warnings, rust_2018_idioms),
+ allow(dead_code, unused_assignments, unused_variables)
+ )
+))]
+#![warn(
+ missing_docs,
+ missing_debug_implementations,
+ rust_2018_idioms,
+ unreachable_pub
+)]
+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[cfg(not(crossbeam_no_atomic_cas))]
+cfg_if::cfg_if! {
+ if #[cfg(feature = "alloc")] {
+ extern crate alloc;
+
+ mod array_queue;
+ mod seg_queue;
+
+ pub use self::array_queue::ArrayQueue;
+ pub use self::seg_queue::SegQueue;
+ }
+}
diff --git a/third_party/rust/crossbeam-queue/src/seg_queue.rs b/third_party/rust/crossbeam-queue/src/seg_queue.rs
new file mode 100644
index 0000000000..2761dc07cd
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/src/seg_queue.rs
@@ -0,0 +1,547 @@
+use alloc::boxed::Box;
+use core::cell::UnsafeCell;
+use core::fmt;
+use core::marker::PhantomData;
+use core::mem::MaybeUninit;
+use core::ptr;
+use core::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+
+use crossbeam_utils::{Backoff, CachePadded};
+
+// Bits indicating the state of a slot:
+// * If a value has been written into the slot, `WRITE` is set.
+// * If a value has been read from the slot, `READ` is set.
+// * If the block is being destroyed, `DESTROY` is set.
+const WRITE: usize = 1;
+const READ: usize = 2;
+const DESTROY: usize = 4;
+
+// Each block covers one "lap" of indices.
+const LAP: usize = 32;
+// The maximum number of values a block can hold.
+const BLOCK_CAP: usize = LAP - 1;
+// How many lower bits are reserved for metadata.
+const SHIFT: usize = 1;
+// Indicates that the block is not the last one.
+const HAS_NEXT: usize = 1;
+
+/// A slot in a block.
+struct Slot<T> {
+ /// The value.
+ value: UnsafeCell<MaybeUninit<T>>,
+
+ /// The state of the slot.
+ state: AtomicUsize,
+}
+
+impl<T> Slot<T> {
+ const UNINIT: Self = Self {
+ value: UnsafeCell::new(MaybeUninit::uninit()),
+ state: AtomicUsize::new(0),
+ };
+
+ /// Waits until a value is written into the slot.
+ fn wait_write(&self) {
+ let backoff = Backoff::new();
+ while self.state.load(Ordering::Acquire) & WRITE == 0 {
+ backoff.snooze();
+ }
+ }
+}
+
+/// A block in a linked list.
+///
+/// Each block in the list can hold up to `BLOCK_CAP` values.
+struct Block<T> {
+ /// The next block in the linked list.
+ next: AtomicPtr<Block<T>>,
+
+ /// Slots for values.
+ slots: [Slot<T>; BLOCK_CAP],
+}
+
+impl<T> Block<T> {
+ /// Creates an empty block that starts at `start_index`.
+ fn new() -> Block<T> {
+ Self {
+ next: AtomicPtr::new(ptr::null_mut()),
+ slots: [Slot::UNINIT; BLOCK_CAP],
+ }
+ }
+
+ /// Waits until the next pointer is set.
+ fn wait_next(&self) -> *mut Block<T> {
+ let backoff = Backoff::new();
+ loop {
+ let next = self.next.load(Ordering::Acquire);
+ if !next.is_null() {
+ return next;
+ }
+ backoff.snooze();
+ }
+ }
+
+ /// Sets the `DESTROY` bit in slots starting from `start` and destroys the block.
+ unsafe fn destroy(this: *mut Block<T>, start: usize) {
+ // It is not necessary to set the `DESTROY` bit in the last slot because that slot has
+ // begun destruction of the block.
+ for i in start..BLOCK_CAP - 1 {
+ let slot = (*this).slots.get_unchecked(i);
+
+ // Mark the `DESTROY` bit if a thread is still using the slot.
+ if slot.state.load(Ordering::Acquire) & READ == 0
+ && slot.state.fetch_or(DESTROY, Ordering::AcqRel) & READ == 0
+ {
+ // If a thread is still using the slot, it will continue destruction of the block.
+ return;
+ }
+ }
+
+ // No thread is using the block, now it is safe to destroy it.
+ drop(Box::from_raw(this));
+ }
+}
+
+/// A position in a queue.
+struct Position<T> {
+ /// The index in the queue.
+ index: AtomicUsize,
+
+ /// The block in the linked list.
+ block: AtomicPtr<Block<T>>,
+}
+
+/// An unbounded multi-producer multi-consumer queue.
+///
+/// This queue is implemented as a linked list of segments, where each segment is a small buffer
+/// that can hold a handful of elements. There is no limit to how many elements can be in the queue
+/// at a time. However, since segments need to be dynamically allocated as elements get pushed,
+/// this queue is somewhat slower than [`ArrayQueue`].
+///
+/// [`ArrayQueue`]: super::ArrayQueue
+///
+/// # Examples
+///
+/// ```
+/// use crossbeam_queue::SegQueue;
+///
+/// let q = SegQueue::new();
+///
+/// q.push('a');
+/// q.push('b');
+///
+/// assert_eq!(q.pop(), Some('a'));
+/// assert_eq!(q.pop(), Some('b'));
+/// assert!(q.pop().is_none());
+/// ```
+pub struct SegQueue<T> {
+ /// The head of the queue.
+ head: CachePadded<Position<T>>,
+
+ /// The tail of the queue.
+ tail: CachePadded<Position<T>>,
+
+ /// Indicates that dropping a `SegQueue<T>` may drop values of type `T`.
+ _marker: PhantomData<T>,
+}
+
+unsafe impl<T: Send> Send for SegQueue<T> {}
+unsafe impl<T: Send> Sync for SegQueue<T> {}
+
+impl<T> SegQueue<T> {
+ /// Creates a new unbounded queue.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::SegQueue;
+ ///
+ /// let q = SegQueue::<i32>::new();
+ /// ```
+ pub const fn new() -> SegQueue<T> {
+ SegQueue {
+ head: CachePadded::new(Position {
+ block: AtomicPtr::new(ptr::null_mut()),
+ index: AtomicUsize::new(0),
+ }),
+ tail: CachePadded::new(Position {
+ block: AtomicPtr::new(ptr::null_mut()),
+ index: AtomicUsize::new(0),
+ }),
+ _marker: PhantomData,
+ }
+ }
+
+ /// Pushes an element into the queue.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::SegQueue;
+ ///
+ /// let q = SegQueue::new();
+ ///
+ /// q.push(10);
+ /// q.push(20);
+ /// ```
+ pub fn push(&self, value: T) {
+ let backoff = Backoff::new();
+ let mut tail = self.tail.index.load(Ordering::Acquire);
+ let mut block = self.tail.block.load(Ordering::Acquire);
+ let mut next_block = None;
+
+ loop {
+ // Calculate the offset of the index into the block.
+ let offset = (tail >> SHIFT) % LAP;
+
+ // If we reached the end of the block, wait until the next one is installed.
+ if offset == BLOCK_CAP {
+ backoff.snooze();
+ tail = self.tail.index.load(Ordering::Acquire);
+ block = self.tail.block.load(Ordering::Acquire);
+ continue;
+ }
+
+ // If we're going to have to install the next block, allocate it in advance in order to
+ // make the wait for other threads as short as possible.
+ if offset + 1 == BLOCK_CAP && next_block.is_none() {
+ next_block = Some(Box::new(Block::<T>::new()));
+ }
+
+ // If this is the first push operation, we need to allocate the first block.
+ if block.is_null() {
+ let new = Box::into_raw(Box::new(Block::<T>::new()));
+
+ if self
+ .tail
+ .block
+ .compare_exchange(block, new, Ordering::Release, Ordering::Relaxed)
+ .is_ok()
+ {
+ self.head.block.store(new, Ordering::Release);
+ block = new;
+ } else {
+ next_block = unsafe { Some(Box::from_raw(new)) };
+ tail = self.tail.index.load(Ordering::Acquire);
+ block = self.tail.block.load(Ordering::Acquire);
+ continue;
+ }
+ }
+
+ let new_tail = tail + (1 << SHIFT);
+
+ // Try advancing the tail forward.
+ match self.tail.index.compare_exchange_weak(
+ tail,
+ new_tail,
+ Ordering::SeqCst,
+ Ordering::Acquire,
+ ) {
+ Ok(_) => unsafe {
+ // If we've reached the end of the block, install the next one.
+ if offset + 1 == BLOCK_CAP {
+ let next_block = Box::into_raw(next_block.unwrap());
+ let next_index = new_tail.wrapping_add(1 << SHIFT);
+
+ self.tail.block.store(next_block, Ordering::Release);
+ self.tail.index.store(next_index, Ordering::Release);
+ (*block).next.store(next_block, Ordering::Release);
+ }
+
+ // Write the value into the slot.
+ let slot = (*block).slots.get_unchecked(offset);
+ slot.value.get().write(MaybeUninit::new(value));
+ slot.state.fetch_or(WRITE, Ordering::Release);
+
+ return;
+ },
+ Err(t) => {
+ tail = t;
+ block = self.tail.block.load(Ordering::Acquire);
+ backoff.spin();
+ }
+ }
+ }
+ }
+
+ /// Pops an element from the queue.
+ ///
+ /// If the queue is empty, `None` is returned.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::SegQueue;
+ ///
+ /// let q = SegQueue::new();
+ ///
+ /// q.push(10);
+ /// assert_eq!(q.pop(), Some(10));
+ /// assert!(q.pop().is_none());
+ /// ```
+ pub fn pop(&self) -> Option<T> {
+ let backoff = Backoff::new();
+ let mut head = self.head.index.load(Ordering::Acquire);
+ let mut block = self.head.block.load(Ordering::Acquire);
+
+ loop {
+ // Calculate the offset of the index into the block.
+ let offset = (head >> SHIFT) % LAP;
+
+ // If we reached the end of the block, wait until the next one is installed.
+ if offset == BLOCK_CAP {
+ backoff.snooze();
+ head = self.head.index.load(Ordering::Acquire);
+ block = self.head.block.load(Ordering::Acquire);
+ continue;
+ }
+
+ let mut new_head = head + (1 << SHIFT);
+
+ if new_head & HAS_NEXT == 0 {
+ atomic::fence(Ordering::SeqCst);
+ let tail = self.tail.index.load(Ordering::Relaxed);
+
+ // If the tail equals the head, that means the queue is empty.
+ if head >> SHIFT == tail >> SHIFT {
+ return None;
+ }
+
+ // If head and tail are not in the same block, set `HAS_NEXT` in head.
+ if (head >> SHIFT) / LAP != (tail >> SHIFT) / LAP {
+ new_head |= HAS_NEXT;
+ }
+ }
+
+ // The block can be null here only if the first push operation is in progress. In that
+ // case, just wait until it gets initialized.
+ if block.is_null() {
+ backoff.snooze();
+ head = self.head.index.load(Ordering::Acquire);
+ block = self.head.block.load(Ordering::Acquire);
+ continue;
+ }
+
+ // Try moving the head index forward.
+ match self.head.index.compare_exchange_weak(
+ head,
+ new_head,
+ Ordering::SeqCst,
+ Ordering::Acquire,
+ ) {
+ Ok(_) => unsafe {
+ // If we've reached the end of the block, move to the next one.
+ if offset + 1 == BLOCK_CAP {
+ let next = (*block).wait_next();
+ let mut next_index = (new_head & !HAS_NEXT).wrapping_add(1 << SHIFT);
+ if !(*next).next.load(Ordering::Relaxed).is_null() {
+ next_index |= HAS_NEXT;
+ }
+
+ self.head.block.store(next, Ordering::Release);
+ self.head.index.store(next_index, Ordering::Release);
+ }
+
+ // Read the value.
+ let slot = (*block).slots.get_unchecked(offset);
+ slot.wait_write();
+ let value = slot.value.get().read().assume_init();
+
+ // Destroy the block if we've reached the end, or if another thread wanted to
+ // destroy but couldn't because we were busy reading from the slot.
+ if offset + 1 == BLOCK_CAP {
+ Block::destroy(block, 0);
+ } else if slot.state.fetch_or(READ, Ordering::AcqRel) & DESTROY != 0 {
+ Block::destroy(block, offset + 1);
+ }
+
+ return Some(value);
+ },
+ Err(h) => {
+ head = h;
+ block = self.head.block.load(Ordering::Acquire);
+ backoff.spin();
+ }
+ }
+ }
+ }
+
+ /// Returns `true` if the queue is empty.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::SegQueue;
+ ///
+ /// let q = SegQueue::new();
+ ///
+ /// assert!(q.is_empty());
+ /// q.push(1);
+ /// assert!(!q.is_empty());
+ /// ```
+ pub fn is_empty(&self) -> bool {
+ let head = self.head.index.load(Ordering::SeqCst);
+ let tail = self.tail.index.load(Ordering::SeqCst);
+ head >> SHIFT == tail >> SHIFT
+ }
+
+ /// Returns the number of elements in the queue.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_queue::SegQueue;
+ ///
+ /// let q = SegQueue::new();
+ /// assert_eq!(q.len(), 0);
+ ///
+ /// q.push(10);
+ /// assert_eq!(q.len(), 1);
+ ///
+ /// q.push(20);
+ /// assert_eq!(q.len(), 2);
+ /// ```
+ pub fn len(&self) -> usize {
+ loop {
+ // Load the tail index, then load the head index.
+ let mut tail = self.tail.index.load(Ordering::SeqCst);
+ let mut head = self.head.index.load(Ordering::SeqCst);
+
+ // If the tail index didn't change, we've got consistent indices to work with.
+ if self.tail.index.load(Ordering::SeqCst) == tail {
+ // Erase the lower bits.
+ tail &= !((1 << SHIFT) - 1);
+ head &= !((1 << SHIFT) - 1);
+
+ // Fix up indices if they fall onto block ends.
+ if (tail >> SHIFT) & (LAP - 1) == LAP - 1 {
+ tail = tail.wrapping_add(1 << SHIFT);
+ }
+ if (head >> SHIFT) & (LAP - 1) == LAP - 1 {
+ head = head.wrapping_add(1 << SHIFT);
+ }
+
+ // Rotate indices so that head falls into the first block.
+ let lap = (head >> SHIFT) / LAP;
+ tail = tail.wrapping_sub((lap * LAP) << SHIFT);
+ head = head.wrapping_sub((lap * LAP) << SHIFT);
+
+ // Remove the lower bits.
+ tail >>= SHIFT;
+ head >>= SHIFT;
+
+ // Return the difference minus the number of blocks between tail and head.
+ return tail - head - tail / LAP;
+ }
+ }
+ }
+}
+
+impl<T> Drop for SegQueue<T> {
+ fn drop(&mut self) {
+ let mut head = *self.head.index.get_mut();
+ let mut tail = *self.tail.index.get_mut();
+ let mut block = *self.head.block.get_mut();
+
+ // Erase the lower bits.
+ head &= !((1 << SHIFT) - 1);
+ tail &= !((1 << SHIFT) - 1);
+
+ unsafe {
+ // Drop all values between `head` and `tail` and deallocate the heap-allocated blocks.
+ while head != tail {
+ let offset = (head >> SHIFT) % LAP;
+
+ if offset < BLOCK_CAP {
+ // Drop the value in the slot.
+ let slot = (*block).slots.get_unchecked(offset);
+ let p = &mut *slot.value.get();
+ p.as_mut_ptr().drop_in_place();
+ } else {
+ // Deallocate the block and move to the next one.
+ let next = *(*block).next.get_mut();
+ drop(Box::from_raw(block));
+ block = next;
+ }
+
+ head = head.wrapping_add(1 << SHIFT);
+ }
+
+ // Deallocate the last remaining block.
+ if !block.is_null() {
+ drop(Box::from_raw(block));
+ }
+ }
+ }
+}
+
+impl<T> fmt::Debug for SegQueue<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.pad("SegQueue { .. }")
+ }
+}
+
+impl<T> Default for SegQueue<T> {
+ fn default() -> SegQueue<T> {
+ SegQueue::new()
+ }
+}
+
+impl<T> IntoIterator for SegQueue<T> {
+ type Item = T;
+
+ type IntoIter = IntoIter<T>;
+
+ fn into_iter(self) -> Self::IntoIter {
+ IntoIter { value: self }
+ }
+}
+
+#[derive(Debug)]
+pub struct IntoIter<T> {
+ value: SegQueue<T>,
+}
+
+impl<T> Iterator for IntoIter<T> {
+ type Item = T;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ let value = &mut self.value;
+ let head = *value.head.index.get_mut();
+ let tail = *value.tail.index.get_mut();
+ if head >> SHIFT == tail >> SHIFT {
+ None
+ } else {
+ let block = *value.head.block.get_mut();
+ let offset = (head >> SHIFT) % LAP;
+
+ // SAFETY: We have mutable access to this, so we can read without
+ // worrying about concurrency. Furthermore, we know this is
+ // initialized because it is the value pointed at by `value.head`
+ // and this is a non-empty queue.
+ let item = unsafe {
+ let slot = (*block).slots.get_unchecked(offset);
+ let p = &mut *slot.value.get();
+ p.as_mut_ptr().read()
+ };
+ if offset + 1 == BLOCK_CAP {
+ // Deallocate the block and move to the next one.
+ // SAFETY: The block is initialized because we've been reading
+ // from it this entire time. We can drop it b/c everything has
+ // been read out of it, so nothing is pointing to it anymore.
+ unsafe {
+ let next = *(*block).next.get_mut();
+ drop(Box::from_raw(block));
+ *value.head.block.get_mut() = next;
+ }
+ // The last value in a block is empty, so skip it
+ *value.head.index.get_mut() = head.wrapping_add(2 << SHIFT);
+ // Double-check that we're pointing to the first item in a block.
+ debug_assert_eq!((*value.head.index.get_mut() >> SHIFT) % LAP, 0);
+ } else {
+ *value.head.index.get_mut() = head.wrapping_add(1 << SHIFT);
+ }
+ Some(item)
+ }
+ }
+}
diff --git a/third_party/rust/crossbeam-queue/tests/array_queue.rs b/third_party/rust/crossbeam-queue/tests/array_queue.rs
new file mode 100644
index 0000000000..b9d4e5fd46
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/tests/array_queue.rs
@@ -0,0 +1,374 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+use crossbeam_queue::ArrayQueue;
+use crossbeam_utils::thread::scope;
+use rand::{thread_rng, Rng};
+
+#[test]
+fn smoke() {
+ let q = ArrayQueue::new(1);
+
+ q.push(7).unwrap();
+ assert_eq!(q.pop(), Some(7));
+
+ q.push(8).unwrap();
+ assert_eq!(q.pop(), Some(8));
+ assert!(q.pop().is_none());
+}
+
+#[test]
+fn capacity() {
+ for i in 1..10 {
+ let q = ArrayQueue::<i32>::new(i);
+ assert_eq!(q.capacity(), i);
+ }
+}
+
+#[test]
+#[should_panic(expected = "capacity must be non-zero")]
+fn zero_capacity() {
+ let _ = ArrayQueue::<i32>::new(0);
+}
+
+#[test]
+fn len_empty_full() {
+ let q = ArrayQueue::new(2);
+
+ assert_eq!(q.len(), 0);
+ assert!(q.is_empty());
+ assert!(!q.is_full());
+
+ q.push(()).unwrap();
+
+ assert_eq!(q.len(), 1);
+ assert!(!q.is_empty());
+ assert!(!q.is_full());
+
+ q.push(()).unwrap();
+
+ assert_eq!(q.len(), 2);
+ assert!(!q.is_empty());
+ assert!(q.is_full());
+
+ q.pop().unwrap();
+
+ assert_eq!(q.len(), 1);
+ assert!(!q.is_empty());
+ assert!(!q.is_full());
+}
+
+#[test]
+fn len() {
+ #[cfg(miri)]
+ const COUNT: usize = 30;
+ #[cfg(not(miri))]
+ const COUNT: usize = 25_000;
+ #[cfg(miri)]
+ const CAP: usize = 40;
+ #[cfg(not(miri))]
+ const CAP: usize = 1000;
+ const ITERS: usize = CAP / 20;
+
+ let q = ArrayQueue::new(CAP);
+ assert_eq!(q.len(), 0);
+
+ for _ in 0..CAP / 10 {
+ for i in 0..ITERS {
+ q.push(i).unwrap();
+ assert_eq!(q.len(), i + 1);
+ }
+
+ for i in 0..ITERS {
+ q.pop().unwrap();
+ assert_eq!(q.len(), ITERS - i - 1);
+ }
+ }
+ assert_eq!(q.len(), 0);
+
+ for i in 0..CAP {
+ q.push(i).unwrap();
+ assert_eq!(q.len(), i + 1);
+ }
+
+ for _ in 0..CAP {
+ q.pop().unwrap();
+ }
+ assert_eq!(q.len(), 0);
+
+ scope(|scope| {
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ loop {
+ if let Some(x) = q.pop() {
+ assert_eq!(x, i);
+ break;
+ }
+ }
+ let len = q.len();
+ assert!(len <= CAP);
+ }
+ });
+
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ while q.push(i).is_err() {}
+ let len = q.len();
+ assert!(len <= CAP);
+ }
+ });
+ })
+ .unwrap();
+ assert_eq!(q.len(), 0);
+}
+
+#[test]
+fn spsc() {
+ #[cfg(miri)]
+ const COUNT: usize = 50;
+ #[cfg(not(miri))]
+ const COUNT: usize = 100_000;
+
+ let q = ArrayQueue::new(3);
+
+ scope(|scope| {
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ loop {
+ if let Some(x) = q.pop() {
+ assert_eq!(x, i);
+ break;
+ }
+ }
+ }
+ assert!(q.pop().is_none());
+ });
+
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ while q.push(i).is_err() {}
+ }
+ });
+ })
+ .unwrap();
+}
+
+#[test]
+fn spsc_ring_buffer() {
+ #[cfg(miri)]
+ const COUNT: usize = 50;
+ #[cfg(not(miri))]
+ const COUNT: usize = 100_000;
+
+ let t = AtomicUsize::new(1);
+ let q = ArrayQueue::<usize>::new(3);
+ let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::<Vec<_>>();
+
+ scope(|scope| {
+ scope.spawn(|_| loop {
+ match t.load(Ordering::SeqCst) {
+ 0 if q.is_empty() => break,
+
+ _ => {
+ while let Some(n) = q.pop() {
+ v[n].fetch_add(1, Ordering::SeqCst);
+ }
+ }
+ }
+ });
+
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ if let Some(n) = q.force_push(i) {
+ v[n].fetch_add(1, Ordering::SeqCst);
+ }
+ }
+
+ t.fetch_sub(1, Ordering::SeqCst);
+ });
+ })
+ .unwrap();
+
+ for c in v {
+ assert_eq!(c.load(Ordering::SeqCst), 1);
+ }
+}
+
+#[test]
+fn mpmc() {
+ #[cfg(miri)]
+ const COUNT: usize = 50;
+ #[cfg(not(miri))]
+ const COUNT: usize = 25_000;
+ const THREADS: usize = 4;
+
+ let q = ArrayQueue::<usize>::new(3);
+ let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::<Vec<_>>();
+
+ scope(|scope| {
+ for _ in 0..THREADS {
+ scope.spawn(|_| {
+ for _ in 0..COUNT {
+ let n = loop {
+ if let Some(x) = q.pop() {
+ break x;
+ }
+ };
+ v[n].fetch_add(1, Ordering::SeqCst);
+ }
+ });
+ }
+ for _ in 0..THREADS {
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ while q.push(i).is_err() {}
+ }
+ });
+ }
+ })
+ .unwrap();
+
+ for c in v {
+ assert_eq!(c.load(Ordering::SeqCst), THREADS);
+ }
+}
+
+#[test]
+fn mpmc_ring_buffer() {
+ #[cfg(miri)]
+ const COUNT: usize = 50;
+ #[cfg(not(miri))]
+ const COUNT: usize = 25_000;
+ const THREADS: usize = 4;
+
+ let t = AtomicUsize::new(THREADS);
+ let q = ArrayQueue::<usize>::new(3);
+ let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::<Vec<_>>();
+
+ scope(|scope| {
+ for _ in 0..THREADS {
+ scope.spawn(|_| loop {
+ match t.load(Ordering::SeqCst) {
+ 0 if q.is_empty() => break,
+
+ _ => {
+ while let Some(n) = q.pop() {
+ v[n].fetch_add(1, Ordering::SeqCst);
+ }
+ }
+ }
+ });
+ }
+
+ for _ in 0..THREADS {
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ if let Some(n) = q.force_push(i) {
+ v[n].fetch_add(1, Ordering::SeqCst);
+ }
+ }
+
+ t.fetch_sub(1, Ordering::SeqCst);
+ });
+ }
+ })
+ .unwrap();
+
+ for c in v {
+ assert_eq!(c.load(Ordering::SeqCst), THREADS);
+ }
+}
+
+#[test]
+fn drops() {
+ let runs: usize = if cfg!(miri) { 3 } else { 100 };
+ let steps: usize = if cfg!(miri) { 50 } else { 10_000 };
+ let additional: usize = if cfg!(miri) { 10 } else { 50 };
+
+ static DROPS: AtomicUsize = AtomicUsize::new(0);
+
+ #[derive(Debug, PartialEq)]
+ struct DropCounter;
+
+ impl Drop for DropCounter {
+ fn drop(&mut self) {
+ DROPS.fetch_add(1, Ordering::SeqCst);
+ }
+ }
+
+ let mut rng = thread_rng();
+
+ for _ in 0..runs {
+ let steps = rng.gen_range(0..steps);
+ let additional = rng.gen_range(0..additional);
+
+ DROPS.store(0, Ordering::SeqCst);
+ let q = ArrayQueue::new(50);
+
+ scope(|scope| {
+ scope.spawn(|_| {
+ for _ in 0..steps {
+ while q.pop().is_none() {}
+ }
+ });
+
+ scope.spawn(|_| {
+ for _ in 0..steps {
+ while q.push(DropCounter).is_err() {
+ DROPS.fetch_sub(1, Ordering::SeqCst);
+ }
+ }
+ });
+ })
+ .unwrap();
+
+ for _ in 0..additional {
+ q.push(DropCounter).unwrap();
+ }
+
+ assert_eq!(DROPS.load(Ordering::SeqCst), steps);
+ drop(q);
+ assert_eq!(DROPS.load(Ordering::SeqCst), steps + additional);
+ }
+}
+
+#[test]
+fn linearizable() {
+ #[cfg(miri)]
+ const COUNT: usize = 100;
+ #[cfg(not(miri))]
+ const COUNT: usize = 25_000;
+ const THREADS: usize = 4;
+
+ let q = ArrayQueue::new(THREADS);
+
+ scope(|scope| {
+ for _ in 0..THREADS / 2 {
+ scope.spawn(|_| {
+ for _ in 0..COUNT {
+ while q.push(0).is_err() {}
+ q.pop().unwrap();
+ }
+ });
+
+ scope.spawn(|_| {
+ for _ in 0..COUNT {
+ if q.force_push(0).is_none() {
+ q.pop().unwrap();
+ }
+ }
+ });
+ }
+ })
+ .unwrap();
+}
+
+#[test]
+fn into_iter() {
+ let q = ArrayQueue::new(100);
+ for i in 0..100 {
+ q.push(i).unwrap();
+ }
+ for (i, j) in q.into_iter().enumerate() {
+ assert_eq!(i, j);
+ }
+}
diff --git a/third_party/rust/crossbeam-queue/tests/seg_queue.rs b/third_party/rust/crossbeam-queue/tests/seg_queue.rs
new file mode 100644
index 0000000000..bf5fb998a5
--- /dev/null
+++ b/third_party/rust/crossbeam-queue/tests/seg_queue.rs
@@ -0,0 +1,195 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+use crossbeam_queue::SegQueue;
+use crossbeam_utils::thread::scope;
+use rand::{thread_rng, Rng};
+
+#[test]
+fn smoke() {
+ let q = SegQueue::new();
+ q.push(7);
+ assert_eq!(q.pop(), Some(7));
+
+ q.push(8);
+ assert_eq!(q.pop(), Some(8));
+ assert!(q.pop().is_none());
+}
+
+#[test]
+fn len_empty_full() {
+ let q = SegQueue::new();
+
+ assert_eq!(q.len(), 0);
+ assert!(q.is_empty());
+
+ q.push(());
+
+ assert_eq!(q.len(), 1);
+ assert!(!q.is_empty());
+
+ q.pop().unwrap();
+
+ assert_eq!(q.len(), 0);
+ assert!(q.is_empty());
+}
+
+#[test]
+fn len() {
+ let q = SegQueue::new();
+
+ assert_eq!(q.len(), 0);
+
+ for i in 0..50 {
+ q.push(i);
+ assert_eq!(q.len(), i + 1);
+ }
+
+ for i in 0..50 {
+ q.pop().unwrap();
+ assert_eq!(q.len(), 50 - i - 1);
+ }
+
+ assert_eq!(q.len(), 0);
+}
+
+#[test]
+fn spsc() {
+ #[cfg(miri)]
+ const COUNT: usize = 100;
+ #[cfg(not(miri))]
+ const COUNT: usize = 100_000;
+
+ let q = SegQueue::new();
+
+ scope(|scope| {
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ loop {
+ if let Some(x) = q.pop() {
+ assert_eq!(x, i);
+ break;
+ }
+ }
+ }
+ assert!(q.pop().is_none());
+ });
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ q.push(i);
+ }
+ });
+ })
+ .unwrap();
+}
+
+#[test]
+fn mpmc() {
+ #[cfg(miri)]
+ const COUNT: usize = 50;
+ #[cfg(not(miri))]
+ const COUNT: usize = 25_000;
+ const THREADS: usize = 4;
+
+ let q = SegQueue::<usize>::new();
+ let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::<Vec<_>>();
+
+ scope(|scope| {
+ for _ in 0..THREADS {
+ scope.spawn(|_| {
+ for _ in 0..COUNT {
+ let n = loop {
+ if let Some(x) = q.pop() {
+ break x;
+ }
+ };
+ v[n].fetch_add(1, Ordering::SeqCst);
+ }
+ });
+ }
+ for _ in 0..THREADS {
+ scope.spawn(|_| {
+ for i in 0..COUNT {
+ q.push(i);
+ }
+ });
+ }
+ })
+ .unwrap();
+
+ for c in v {
+ assert_eq!(c.load(Ordering::SeqCst), THREADS);
+ }
+}
+
+#[test]
+fn drops() {
+ let runs: usize = if cfg!(miri) { 5 } else { 100 };
+ let steps: usize = if cfg!(miri) { 50 } else { 10_000 };
+ let additional: usize = if cfg!(miri) { 100 } else { 1_000 };
+
+ static DROPS: AtomicUsize = AtomicUsize::new(0);
+
+ #[derive(Debug, PartialEq)]
+ struct DropCounter;
+
+ impl Drop for DropCounter {
+ fn drop(&mut self) {
+ DROPS.fetch_add(1, Ordering::SeqCst);
+ }
+ }
+
+ let mut rng = thread_rng();
+
+ for _ in 0..runs {
+ let steps = rng.gen_range(0..steps);
+ let additional = rng.gen_range(0..additional);
+
+ DROPS.store(0, Ordering::SeqCst);
+ let q = SegQueue::new();
+
+ scope(|scope| {
+ scope.spawn(|_| {
+ for _ in 0..steps {
+ while q.pop().is_none() {}
+ }
+ });
+
+ scope.spawn(|_| {
+ for _ in 0..steps {
+ q.push(DropCounter);
+ }
+ });
+ })
+ .unwrap();
+
+ for _ in 0..additional {
+ q.push(DropCounter);
+ }
+
+ assert_eq!(DROPS.load(Ordering::SeqCst), steps);
+ drop(q);
+ assert_eq!(DROPS.load(Ordering::SeqCst), steps + additional);
+ }
+}
+
+#[test]
+fn into_iter() {
+ let q = SegQueue::new();
+ for i in 0..100 {
+ q.push(i);
+ }
+ for (i, j) in q.into_iter().enumerate() {
+ assert_eq!(i, j);
+ }
+}
+
+#[test]
+fn into_iter_drop() {
+ let q = SegQueue::new();
+ for i in 0..100 {
+ q.push(i);
+ }
+ for (i, j) in q.into_iter().enumerate().take(50) {
+ assert_eq!(i, j);
+ }
+}