Import crossbeam-queue rust crate am: f2469bb2e5 am: fcdc67c253 am: 404154f244 am: e78a924b12
Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/crossbeam-queue/+/1814088
Change-Id: I51d0ebd6143ab5ca43f775f750aec4571d1d3838
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..51832d2
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,108 @@
+// This file is generated by cargo2android.py --run --device --dependencies --tests.
+// Do not modify this file as changes will be overridden on upgrade.
+
+
+
+rust_defaults {
+ name: "crossbeam-queue_test_defaults",
+ crate_name: "crossbeam_queue",
+ srcs: ["src/lib.rs"],
+ test_suites: ["general-tests"],
+ auto_gen_config: true,
+ edition: "2018",
+ features: [
+ "alloc",
+ "default",
+ "std",
+ ],
+ rustlibs: [
+ "libcfg_if",
+ "libcrossbeam_utils",
+ "librand",
+ ],
+}
+
+rust_test_host {
+ name: "crossbeam-queue_host_test_src_lib",
+ defaults: ["crossbeam-queue_test_defaults"],
+ test_options: {
+ unit_test: true,
+ },
+}
+
+rust_test {
+ name: "crossbeam-queue_device_test_src_lib",
+ defaults: ["crossbeam-queue_test_defaults"],
+}
+
+rust_defaults {
+ name: "crossbeam-queue_test_defaults_crossbeam_queue",
+ crate_name: "crossbeam_queue",
+ test_suites: ["general-tests"],
+ auto_gen_config: true,
+ edition: "2018",
+ features: [
+ "alloc",
+ "default",
+ "std",
+ ],
+ rustlibs: [
+ "libcfg_if",
+ "libcrossbeam_queue",
+ "libcrossbeam_utils",
+ "librand",
+ ],
+}
+
+rust_test_host {
+ name: "crossbeam-queue_host_test_tests_array_queue",
+ defaults: ["crossbeam-queue_test_defaults_crossbeam_queue"],
+ srcs: ["tests/array_queue.rs"],
+ test_options: {
+ unit_test: true,
+ },
+}
+
+rust_test {
+ name: "crossbeam-queue_device_test_tests_array_queue",
+ defaults: ["crossbeam-queue_test_defaults_crossbeam_queue"],
+ srcs: ["tests/array_queue.rs"],
+}
+
+rust_test_host {
+ name: "crossbeam-queue_host_test_tests_seg_queue",
+ defaults: ["crossbeam-queue_test_defaults_crossbeam_queue"],
+ srcs: ["tests/seg_queue.rs"],
+ test_options: {
+ unit_test: true,
+ },
+}
+
+rust_test {
+ name: "crossbeam-queue_device_test_tests_seg_queue",
+ defaults: ["crossbeam-queue_test_defaults_crossbeam_queue"],
+ srcs: ["tests/seg_queue.rs"],
+}
+
+rust_library {
+ name: "libcrossbeam_queue",
+ host_supported: true,
+ crate_name: "crossbeam_queue",
+ cargo_env_compat: true,
+ cargo_pkg_version: "0.3.2",
+ srcs: ["src/lib.rs"],
+ edition: "2018",
+ features: [
+ "alloc",
+ "default",
+ "std",
+ ],
+ rustlibs: [
+ "libcfg_if",
+ "libcrossbeam_utils",
+ ],
+ apex_available: [
+ "//apex_available:platform",
+ "com.android.virt",
+ ],
+}
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..68306c8
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,42 @@
+# 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/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..dc16305
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,38 @@
+# 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 = "crossbeam-queue"
+version = "0.3.2"
+authors = ["The Crossbeam Project Developers"]
+description = "Concurrent queues"
+homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-queue"
+documentation = "https://docs.rs/crossbeam-queue"
+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/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..dbefdc5
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,49 @@
+[package]
+name = "crossbeam-queue"
+# When publishing a new version:
+# - Update CHANGELOG.md
+# - Update README.md
+# - Create "crossbeam-queue-X.Y.Z" git tag
+version = "0.3.2"
+authors = ["The Crossbeam Project Developers"]
+edition = "2018"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/crossbeam-rs/crossbeam"
+homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-queue"
+documentation = "https://docs.rs/crossbeam-queue"
+description = "Concurrent queues"
+keywords = ["queue", "mpmc", "lock-free", "producer", "consumer"]
+categories = ["concurrency", "data-structures", "no-std"]
+
+[features]
+default = ["std"]
+
+# Enable to use APIs that require `std`.
+# This is enabled by default.
+std = ["alloc", "crossbeam-utils/std"]
+
+# Enable to use APIs that require `alloc`.
+# This is enabled by default and also enabled if the `std` feature is enabled.
+#
+# NOTE: Disabling both `std` *and* `alloc` features is not supported yet.
+alloc = []
+
+# These features are no longer used.
+# TODO: remove in the next major version.
+# Enable to use of unstable functionality.
+# This is disabled by default and requires recent nightly compiler.
+#
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
+nightly = ["crossbeam-utils/nightly"]
+
+[dependencies]
+cfg-if = "1"
+
+[dependencies.crossbeam-utils]
+version = "0.8.5"
+path = "../crossbeam-utils"
+default-features = false
+
+[dev-dependencies]
+rand = "0.8"
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..16fe87b
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
+ Apache License
+ Version 2.0, January 2004
+ http://www.apache.org/licenses/
+
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+ 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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+ To apply the Apache License to your work, attach the following
+ boilerplate notice, with the fields enclosed by brackets "[]"
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+Unless required by applicable law or agreed to in writing, software
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diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..068d491
--- /dev/null
+++ b/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/METADATA b/METADATA
new file mode 100644
index 0000000..37b8868
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,20 @@
+name: "crossbeam-queue"
+description: "Concurrent queues"
+third_party {
+ url {
+ type: HOMEPAGE
+ value: "https://crates.io/crates/crossbeam-queue"
+ }
+ url {
+ type: ARCHIVE
+ value: "https://static.crates.io/crates/crossbeam-queue/crossbeam-queue-0.3.2.crate"
+ }
+ version: "0.3.2"
+ # Dual-licensed, using the least restrictive per go/thirdpartylicenses#same.
+ license_type: NOTICE
+ last_upgrade_date {
+ year: 2021
+ month: 8
+ day: 30
+ }
+}
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/OWNERS b/OWNERS
new file mode 100644
index 0000000..45dc4dd
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/prebuilts/rust:master:/OWNERS
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..2f30b39
--- /dev/null
+++ b/README.md
@@ -0,0 +1,54 @@
+# Crossbeam Queue
+
+[](
+https://github.com/crossbeam-rs/crossbeam/actions)
+[](
+https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-queue#license)
+[](
+https://crates.io/crates/crossbeam-queue)
+[](
+https://docs.rs/crossbeam-queue)
+[](
+https://www.rust-lang.org)
+[](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 1.36.
+
+## 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/build.rs b/build.rs
new file mode 100644
index 0000000..4ef1279
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,32 @@
+#![warn(rust_2018_idioms)]
+
+use std::env;
+
+include!("no_atomic.rs");
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+ let target = match env::var("TARGET") {
+ Ok(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
+ // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+ // run. This is needed for compatibility with 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/no_atomic.rs b/no_atomic.rs
new file mode 100644
index 0000000..522b3b8
--- /dev/null
+++ b/no_atomic.rs
@@ -0,0 +1,59 @@
+// This file is @generated by no_atomic.sh.
+// It is not intended for manual editing.
+
+const NO_ATOMIC_CAS: &[&str] = &[
+ "avr-unknown-gnu-atmega328",
+ "msp430-none-elf",
+ "riscv32i-unknown-none-elf",
+ "riscv32imc-unknown-none-elf",
+ "thumbv4t-none-eabi",
+ "thumbv6m-none-eabi",
+];
+#[allow(dead_code)]
+const NO_ATOMIC_64: &[&str] = &[
+ "arm-linux-androideabi",
+ "armebv7r-none-eabi",
+ "armebv7r-none-eabihf",
+ "armv4t-unknown-linux-gnueabi",
+ "armv5te-unknown-linux-gnueabi",
+ "armv5te-unknown-linux-musleabi",
+ "armv5te-unknown-linux-uclibceabi",
+ "armv7r-none-eabi",
+ "armv7r-none-eabihf",
+ "hexagon-unknown-linux-musl",
+ "mips-unknown-linux-gnu",
+ "mips-unknown-linux-musl",
+ "mips-unknown-linux-uclibc",
+ "mipsel-unknown-linux-gnu",
+ "mipsel-unknown-linux-musl",
+ "mipsel-unknown-linux-uclibc",
+ "mipsel-unknown-none",
+ "mipsisa32r6-unknown-linux-gnu",
+ "mipsisa32r6el-unknown-linux-gnu",
+ "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",
+ "riscv32imac-unknown-none-elf",
+ "thumbv7em-none-eabi",
+ "thumbv7em-none-eabihf",
+ "thumbv7m-none-eabi",
+ "thumbv8m.base-none-eabi",
+ "thumbv8m.main-none-eabi",
+ "thumbv8m.main-none-eabihf",
+ "mipsel-sony-psp",
+ "thumbv4t-none-eabi",
+ "thumbv6m-none-eabi",
+];
+#[allow(dead_code)]
+const NO_ATOMIC: &[&str] = &[
+ "avr-unknown-gnu-atmega328",
+ "msp430-none-elf",
+ "riscv32i-unknown-none-elf",
+ "riscv32imc-unknown-none-elf",
+];
diff --git a/src/array_queue.rs b/src/array_queue.rs
new file mode 100644
index 0000000..ff1efaa
--- /dev/null
+++ b/src/array_queue.rs
@@ -0,0 +1,434 @@
+//! 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::marker::PhantomData;
+use core::mem::{self, 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. Having a buffer allocated upfront makes this queue a bit
+/// faster than [`SegQueue`].
+///
+/// [`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: *mut Slot<T>,
+
+ /// The queue capacity.
+ cap: usize,
+
+ /// A stamp with the value of `{ lap: 1, index: 0 }`.
+ one_lap: usize,
+
+ /// Indicates that dropping an `ArrayQueue<T>` may drop elements of type `T`.
+ _marker: PhantomData<T>,
+}
+
+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 = {
+ let mut boxed: 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();
+ let ptr = boxed.as_mut_ptr();
+ mem::forget(boxed);
+ ptr
+ };
+
+ // 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)),
+ _marker: PhantomData,
+ }
+ }
+
+ /// 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> {
+ 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);
+
+ // Inspect the corresponding slot.
+ let slot = unsafe { &*self.buffer.add(index) };
+ let stamp = slot.stamp.load(Ordering::Acquire);
+
+ // If the tail and the stamp match, we may attempt to push.
+ if tail == stamp {
+ 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)
+ };
+
+ // 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);
+ 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.
+ return Err(value);
+ }
+
+ 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 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.
+ let slot = unsafe { &*self.buffer.add(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 hix = self.head.load(Ordering::Relaxed) & (self.one_lap - 1);
+
+ // Loop over all slots that hold a message and drop them.
+ for i in 0..self.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 {
+ let p = {
+ let slot = &mut *self.buffer.add(index);
+ let value = &mut *slot.value.get();
+ value.as_mut_ptr()
+ };
+ p.drop_in_place();
+ }
+ }
+
+ // Finally, deallocate the buffer, but don't run any destructors.
+ unsafe {
+ // Create a slice from the buffer to make
+ // a fat pointer. Then, use Box::from_raw
+ // to deallocate it.
+ let ptr = core::slice::from_raw_parts_mut(self.buffer, self.cap) as *mut [Slot<T>];
+ Box::from_raw(ptr);
+ }
+ }
+}
+
+impl<T> fmt::Debug for ArrayQueue<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.pad("ArrayQueue { .. }")
+ }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..846d7c2
--- /dev/null
+++ b/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/src/seg_queue.rs b/src/seg_queue.rs
new file mode 100644
index 0000000..8545541
--- /dev/null
+++ b/src/seg_queue.rs
@@ -0,0 +1,486 @@
+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> {
+ /// 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> {
+ // SAFETY: This is safe because:
+ // [1] `Block::next` (AtomicPtr) may be safely zero initialized.
+ // [2] `Block::slots` (Array) may be safely zero initialized because of [3, 4].
+ // [3] `Slot::value` (UnsafeCell) may be safely zero initialized because it
+ // holds a MaybeUninit.
+ // [4] `Slot::state` (AtomicUsize) may be safely zero initialized.
+ unsafe { MaybeUninit::zeroed().assume_init() }
+ }
+
+ /// 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.load(Ordering::Relaxed);
+ let mut tail = self.tail.index.load(Ordering::Relaxed);
+ let mut block = self.head.block.load(Ordering::Relaxed);
+
+ // 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.load(Ordering::Relaxed);
+ 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()
+ }
+}
diff --git a/tests/array_queue.rs b/tests/array_queue.rs
new file mode 100644
index 0000000..63007eb
--- /dev/null
+++ b/tests/array_queue.rs
@@ -0,0 +1,250 @@
+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_eq!(q.is_empty(), true);
+ assert_eq!(q.is_full(), false);
+
+ q.push(()).unwrap();
+
+ assert_eq!(q.len(), 1);
+ assert_eq!(q.is_empty(), false);
+ assert_eq!(q.is_full(), false);
+
+ q.push(()).unwrap();
+
+ assert_eq!(q.len(), 2);
+ assert_eq!(q.is_empty(), false);
+ assert_eq!(q.is_full(), true);
+
+ q.pop().unwrap();
+
+ assert_eq!(q.len(), 1);
+ assert_eq!(q.is_empty(), false);
+ assert_eq!(q.is_full(), false);
+}
+
+#[test]
+fn len() {
+ const COUNT: usize = 25_000;
+ const CAP: usize = 1000;
+
+ let q = ArrayQueue::new(CAP);
+ assert_eq!(q.len(), 0);
+
+ for _ in 0..CAP / 10 {
+ for i in 0..50 {
+ q.push(i).unwrap();
+ 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);
+
+ 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() {
+ 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 mpmc() {
+ 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 drops() {
+ const RUNS: usize = 100;
+
+ 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..10_000);
+ let additional = rng.gen_range(0..50);
+
+ 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() {
+ const COUNT: usize = 25_000;
+ const THREADS: usize = 4;
+
+ let q = ArrayQueue::new(THREADS);
+
+ scope(|scope| {
+ for _ in 0..THREADS {
+ scope.spawn(|_| {
+ for _ in 0..COUNT {
+ while q.push(0).is_err() {}
+ q.pop().unwrap();
+ }
+ });
+ }
+ })
+ .unwrap();
+}
diff --git a/tests/seg_queue.rs b/tests/seg_queue.rs
new file mode 100644
index 0000000..63df9a0
--- /dev/null
+++ b/tests/seg_queue.rs
@@ -0,0 +1,163 @@
+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_eq!(q.is_empty(), true);
+
+ q.push(());
+
+ assert_eq!(q.len(), 1);
+ assert_eq!(q.is_empty(), false);
+
+ q.pop().unwrap();
+
+ assert_eq!(q.len(), 0);
+ assert_eq!(q.is_empty(), true);
+}
+
+#[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() {
+ 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() {
+ 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() {
+ 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..100 {
+ let steps = rng.gen_range(0..10_000);
+ let additional = rng.gen_range(0..1000);
+
+ 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);
+ }
+}