concurrent-queue-2.3.0/.cargo_vcs_info.json0000644000000001360000000000100143420ustar { "git": { "sha1": "22b5e83c4fbd126eddc1990647d0ce35ee754467" }, "path_in_vcs": "" }concurrent-queue-2.3.0/CHANGELOG.md000064400000000000000000000022261046102023000147450ustar 00000000000000# Version 2.3.0 - Implement `UnwindSafe` without libstd. (#49) - Bump `fastrand` to `v2.0.0`. (#43) - Use inline assembly in the `full_fence` funtion. (#47) # Version 2.2.0 - Add the try_iter method. (#36) # Version 2.1.0 - Update `portable-atomic` to 1.0. (#33) # Version 2.0.0 - Add support for the `portable-atomic` and `loom` crates. (#27) - **Breaking:** Add an `std` feature that can be disabled to use this crate on `no_std` platforms. (#22) - Replace usage of `cache-padded` with `crossbeam-utils`. (#26) # Version 1.2.4 - Fix fence on x86 and miri. (#18) - Revert 1.2.3. (#18) # Version 1.2.3 **Note:** This release has been yanked, see #17 for details. - Fix fence on non-x86 architectures and miri. (#16) # Version 1.2.2 - Add a special, efficient `bounded(1)` implementation. # Version 1.2.1 - In the bounded queue, use boxed slice instead of raw pointers. # Version 1.2.0 - Update dependencies. - Implement `UnwindSafe` and `RefUnwindSafe` for `ConcurrentQueue`. # Version 1.1.2 - Optimize `SeqCst` fences. # Version 1.1.1 - Clarify errors in docs. # Version 1.1.0 - Add extra methods to error types. # Version 1.0.0 - Initial version concurrent-queue-2.3.0/Cargo.toml0000644000000027110000000000100123410ustar # 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 = "1.59" name = "concurrent-queue" version = "2.3.0" authors = [ "Stjepan Glavina ", "Taiki Endo ", "John Nunley ", ] exclude = ["/.*"] description = "Concurrent multi-producer multi-consumer queue" readme = "README.md" keywords = [ "channel", "mpmc", "spsc", "spmc", "mpsc", ] categories = ["concurrency"] license = "Apache-2.0 OR MIT" repository = "https://github.com/smol-rs/concurrent-queue" [lib] bench = false [[bench]] name = "bench" harness = false [dependencies.crossbeam-utils] version = "0.8.11" default-features = false [dependencies.portable-atomic] version = "1" optional = true default-features = false [dev-dependencies.criterion] version = "0.4.0" [dev-dependencies.easy-parallel] version = "3.1.0" [dev-dependencies.fastrand] version = "2.0.0" [features] default = ["std"] std = [] [target."cfg(loom)".dependencies.loom] version = "0.7" optional = true concurrent-queue-2.3.0/Cargo.toml.orig000064400000000000000000000021071046102023000160210ustar 00000000000000[package] name = "concurrent-queue" # When publishing a new version: # - Update CHANGELOG.md # - Create "v2.x.y" git tag version = "2.3.0" authors = [ "Stjepan Glavina ", "Taiki Endo ", "John Nunley " ] edition = "2018" rust-version = "1.59" description = "Concurrent multi-producer multi-consumer queue" license = "Apache-2.0 OR MIT" repository = "https://github.com/smol-rs/concurrent-queue" keywords = ["channel", "mpmc", "spsc", "spmc", "mpsc"] categories = ["concurrency"] exclude = ["/.*"] [lib] bench = false [dependencies] crossbeam-utils = { version = "0.8.11", default-features = false } portable-atomic = { version = "1", default-features = false, optional = true } # Enables loom testing. This feature is permanently unstable and the API may # change at any time. [target.'cfg(loom)'.dependencies] loom = { version = "0.7", optional = true } [[bench]] name = "bench" harness = false [dev-dependencies] criterion = "0.4.0" easy-parallel = "3.1.0" fastrand = "2.0.0" [features] default = ["std"] std = [] concurrent-queue-2.3.0/LICENSE-APACHE000064400000000000000000000251371046102023000150660ustar 00000000000000 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, and distribution as defined by Sections 1 through 9 of this document. "Licensor" shall mean the copyright owner or entity authorized by the copyright owner that is granting the License. "Legal Entity" shall mean the union of the acting entity and all other entities that control, are controlled by, or are under common control with that entity. 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See the License for the specific language governing permissions and limitations under the License. concurrent-queue-2.3.0/LICENSE-MIT000064400000000000000000000017771046102023000146020ustar 00000000000000Permission 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. concurrent-queue-2.3.0/README.md000064400000000000000000000031431046102023000144120ustar 00000000000000# concurrent-queue [![Build](https://github.com/smol-rs/concurrent-queue/workflows/Build%20and%20test/badge.svg)]( https://github.com/smol-rs/concurrent-queue/actions) [![License](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue.svg)]( https://github.com/smol-rs/concurrent-queue) [![Cargo](https://img.shields.io/crates/v/concurrent-queue.svg)]( https://crates.io/crates/concurrent-queue) [![Documentation](https://docs.rs/concurrent-queue/badge.svg)]( https://docs.rs/concurrent-queue) A concurrent multi-producer multi-consumer queue. There are two kinds of queues: 1. Bounded queue with limited capacity. 2. Unbounded queue with unlimited capacity. Queues also have the capability to get closed at any point. When closed, no more items can be pushed into the queue, although the remaining items can still be popped. These features make it easy to build channels similar to `std::sync::mpsc` on top of this crate. ## Examples ```rust use concurrent_queue::ConcurrentQueue; let q = ConcurrentQueue::unbounded(); q.push(1).unwrap(); q.push(2).unwrap(); assert_eq!(q.pop(), Ok(1)); assert_eq!(q.pop(), Ok(2)); ``` ## 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. concurrent-queue-2.3.0/benches/bench.rs000064400000000000000000000053721046102023000161750ustar 00000000000000use std::{any::type_name, fmt::Debug}; use concurrent_queue::{ConcurrentQueue, PopError}; use criterion::{black_box, criterion_group, criterion_main, Criterion}; use easy_parallel::Parallel; const COUNT: usize = 100_000; const THREADS: usize = 7; fn spsc(recv: &ConcurrentQueue, send: &ConcurrentQueue) { Parallel::new() .add(|| loop { match recv.pop() { Ok(_) => (), Err(PopError::Empty) => (), Err(PopError::Closed) => break, } }) .add(|| { for _ in 0..COUNT { send.push(T::default()).unwrap(); } send.close(); }) .run(); } fn mpsc(recv: &ConcurrentQueue, send: &ConcurrentQueue) { Parallel::new() .each(0..THREADS, |_| { for _ in 0..COUNT { send.push(T::default()).unwrap(); } }) .add(|| { let mut recieved = 0; while recieved < THREADS * COUNT { match recv.pop() { Ok(_) => recieved += 1, Err(PopError::Empty) => (), Err(PopError::Closed) => unreachable!(), } } }) .run(); } fn single_thread( recv: &ConcurrentQueue, send: &ConcurrentQueue, ) { for _ in 0..COUNT { send.push(T::default()).unwrap(); } for _ in 0..COUNT { recv.pop().unwrap(); } } // Because we can't pass generic functions as const parameters. macro_rules! bench_all( ($name:ident, $f:ident) => { fn $name(c: &mut Criterion) { fn helper(c: &mut Criterion) { let name = format!("unbounded_{}_{}", stringify!($f), type_name::()); c.bench_function(&name, |b| b.iter(|| { let q = ConcurrentQueue::unbounded(); $f::(black_box(&q), black_box(&q)); })); let name = format!("bounded_{}_{}", stringify!($f), type_name::()); c.bench_function(&name, |b| b.iter(|| { let q = ConcurrentQueue::bounded(THREADS * COUNT); $f::(black_box(&q), black_box(&q)); })); } helper::(c); helper::(c); helper::(c); helper::(c); helper::(c); } } ); bench_all!(bench_spsc, spsc); bench_all!(bench_mpsc, mpsc); bench_all!(bench_single_thread, single_thread); criterion_group!(generic_group, bench_single_thread, bench_spsc, bench_mpsc); criterion_main!(generic_group); concurrent-queue-2.3.0/src/bounded.rs000064400000000000000000000273601046102023000157170ustar 00000000000000use alloc::{boxed::Box, vec::Vec}; use core::mem::MaybeUninit; use crossbeam_utils::CachePadded; use crate::sync::atomic::{AtomicUsize, Ordering}; use crate::sync::cell::UnsafeCell; #[allow(unused_imports)] use crate::sync::prelude::*; use crate::{busy_wait, PopError, PushError}; /// A slot in a queue. struct Slot { /// The current stamp. stamp: AtomicUsize, /// The value in this slot. value: UnsafeCell>, } /// A bounded queue. pub struct Bounded { /// The head of the queue. /// /// This value is a "stamp" consisting of an index into the buffer, a mark bit, and a lap, but /// packed into a single `usize`. The lower bits represent the index, while the upper bits /// represent the lap. The mark bit in the head is always zero. /// /// Values are popped from the head of the queue. head: CachePadded, /// The tail of the queue. /// /// This value is a "stamp" consisting of an index into the buffer, a mark bit, and a lap, but /// packed into a single `usize`. The lower bits represent the index, while the upper bits /// represent the lap. The mark bit indicates that the queue is closed. /// /// Values are pushed into the tail of the queue. tail: CachePadded, /// The buffer holding slots. buffer: Box<[Slot]>, /// A stamp with the value of `{ lap: 1, mark: 0, index: 0 }`. one_lap: usize, /// If this bit is set in the tail, that means the queue is closed. mark_bit: usize, } impl Bounded { /// Creates a new bounded queue. pub fn new(cap: usize) -> Bounded { assert!(cap > 0, "capacity must be positive"); // Head is initialized to `{ lap: 0, mark: 0, index: 0 }`. let head = 0; // Tail is initialized to `{ lap: 0, mark: 0, index: 0 }`. let tail = 0; // Allocate a buffer of `cap` slots initialized with stamps. let mut buffer = Vec::with_capacity(cap); for i in 0..cap { // Set the stamp to `{ lap: 0, mark: 0, index: i }`. buffer.push(Slot { stamp: AtomicUsize::new(i), value: UnsafeCell::new(MaybeUninit::uninit()), }); } // Compute constants `mark_bit` and `one_lap`. let mark_bit = (cap + 1).next_power_of_two(); let one_lap = mark_bit * 2; Bounded { buffer: buffer.into(), one_lap, mark_bit, head: CachePadded::new(AtomicUsize::new(head)), tail: CachePadded::new(AtomicUsize::new(tail)), } } /// Attempts to push an item into the queue. pub fn push(&self, value: T) -> Result<(), PushError> { let mut tail = self.tail.load(Ordering::Relaxed); loop { // Check if the queue is closed. if tail & self.mark_bit != 0 { return Err(PushError::Closed(value)); } // Deconstruct the tail. let index = tail & (self.mark_bit - 1); let lap = tail & !(self.one_lap - 1); // Inspect the corresponding slot. let slot = &self.buffer[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.buffer.len() { // Same lap, incremented index. // Set to `{ lap: lap, mark: 0, index: index + 1 }`. tail + 1 } else { // One lap forward, index wraps around to zero. // Set to `{ lap: lap.wrapping_add(1), mark: 0, 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. slot.value.with_mut(|slot| unsafe { slot.write(MaybeUninit::new(value)); }); slot.stamp.store(tail + 1, Ordering::Release); return Ok(()); } Err(t) => { tail = t; } } } else if stamp.wrapping_add(self.one_lap) == tail + 1 { crate::full_fence(); 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(PushError::Full(value)); } // Loom complains if there isn't an explicit busy wait here. #[cfg(loom)] busy_wait(); tail = self.tail.load(Ordering::Relaxed); } else { // Yield because we need to wait for the stamp to get updated. busy_wait(); tail = self.tail.load(Ordering::Relaxed); } } } /// Attempts to pop an item from the queue. pub fn pop(&self) -> Result { let mut head = self.head.load(Ordering::Relaxed); loop { // Deconstruct the head. let index = head & (self.mark_bit - 1); let lap = head & !(self.one_lap - 1); // Inspect the corresponding slot. let slot = &self.buffer[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.buffer.len() { // Same lap, incremented index. // Set to `{ lap: lap, mark: 0, index: index + 1 }`. head + 1 } else { // One lap forward, index wraps around to zero. // Set to `{ lap: lap.wrapping_add(1), mark: 0, 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 value = slot .value .with_mut(|slot| unsafe { slot.read().assume_init() }); slot.stamp .store(head.wrapping_add(self.one_lap), Ordering::Release); return Ok(value); } Err(h) => { head = h; } } } else if stamp == head { crate::full_fence(); let tail = self.tail.load(Ordering::Relaxed); // If the tail equals the head, that means the queue is empty. if (tail & !self.mark_bit) == head { // Check if the queue is closed. if tail & self.mark_bit != 0 { return Err(PopError::Closed); } else { return Err(PopError::Empty); } } // Loom complains if there isn't a busy-wait here. #[cfg(loom)] busy_wait(); head = self.head.load(Ordering::Relaxed); } else { // Yield because we need to wait for the stamp to get updated. busy_wait(); head = self.head.load(Ordering::Relaxed); } } } /// Returns the number of items in the queue. 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.mark_bit - 1); let tix = tail & (self.mark_bit - 1); return if hix < tix { tix - hix } else if hix > tix { self.buffer.len() - hix + tix } else if (tail & !self.mark_bit) == head { 0 } else { self.buffer.len() }; } } } /// Returns `true` if the queue 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 equal to the head? // // Note: If the head changes just before we load the tail, that means there was a moment // when the queue was not empty, so it is safe to just return `false`. (tail & !self.mark_bit) == head } /// Returns `true` if the queue 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 & !self.mark_bit } /// Returns the capacity of the queue. pub fn capacity(&self) -> usize { self.buffer.len() } /// Closes the queue. /// /// Returns `true` if this call closed the queue. pub fn close(&self) -> bool { let tail = self.tail.fetch_or(self.mark_bit, Ordering::SeqCst); tail & self.mark_bit == 0 } /// Returns `true` if the queue is closed. pub fn is_closed(&self) -> bool { self.tail.load(Ordering::SeqCst) & self.mark_bit != 0 } } impl Drop for Bounded { fn drop(&mut self) { // Get the index of the head. let Self { head, tail, buffer, mark_bit, .. } = self; let mark_bit = *mark_bit; head.with_mut(|&mut head| { tail.with_mut(|&mut tail| { let hix = head & (mark_bit - 1); let tix = tail & (mark_bit - 1); let len = if hix < tix { tix - hix } else if hix > tix { buffer.len() - hix + tix } else if (tail & !mark_bit) == head { 0 } else { buffer.len() }; // Loop over all slots that hold a value and drop them. for i in 0..len { // Compute the index of the next slot holding a value. let index = if hix + i < buffer.len() { hix + i } else { hix + i - buffer.len() }; // Drop the value in the slot. let slot = &buffer[index]; slot.value.with_mut(|slot| unsafe { let value = &mut *slot; value.as_mut_ptr().drop_in_place(); }); } }); }); } } concurrent-queue-2.3.0/src/lib.rs000064400000000000000000000406161046102023000150440ustar 00000000000000//! A concurrent multi-producer multi-consumer queue. //! //! There are two kinds of queues: //! //! 1. [Bounded] queue with limited capacity. //! 2. [Unbounded] queue with unlimited capacity. //! //! Queues also have the capability to get [closed] at any point. When closed, no more items can be //! pushed into the queue, although the remaining items can still be popped. //! //! These features make it easy to build channels similar to [`std::sync::mpsc`] on top of this //! crate. //! //! # Examples //! //! ``` //! use concurrent_queue::ConcurrentQueue; //! //! let q = ConcurrentQueue::unbounded(); //! q.push(1).unwrap(); //! q.push(2).unwrap(); //! //! assert_eq!(q.pop(), Ok(1)); //! assert_eq!(q.pop(), Ok(2)); //! ``` //! //! # Features //! //! `concurrent-queue` uses an `std` default feature. With this feature enabled, this crate will //! use [`std::thread::yield_now`] to avoid busy waiting in tight loops. However, with this //! feature disabled, [`core::hint::spin_loop`] will be used instead. Disabling `std` will allow //! this crate to be used on `no_std` platforms at the potential expense of more busy waiting. //! //! There is also a `portable-atomic` feature, which uses a polyfill from the //! [`portable-atomic`] crate to provide atomic operations on platforms that do not support them. //! See the [`README`] for the [`portable-atomic`] crate for more information on how to use it. //! Note that even with this feature enabled, `concurrent-queue` still requires a global allocator //! to be available. See the documentation for the [`std::alloc::GlobalAlloc`] trait for more //! information. //! //! [Bounded]: `ConcurrentQueue::bounded()` //! [Unbounded]: `ConcurrentQueue::unbounded()` //! [closed]: `ConcurrentQueue::close()` //! [`portable-atomic`]: https://crates.io/crates/portable-atomic //! [`README`]: https://github.com/taiki-e/portable-atomic/blob/main/README.md#optional-cfg #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)] #![no_std] #![doc( html_favicon_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png" )] #![doc( html_logo_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png" )] extern crate alloc; #[cfg(feature = "std")] extern crate std; use alloc::boxed::Box; use core::fmt; use core::panic::{RefUnwindSafe, UnwindSafe}; use sync::atomic::{self, Ordering}; #[cfg(feature = "std")] use std::error; use crate::bounded::Bounded; use crate::single::Single; use crate::sync::busy_wait; use crate::unbounded::Unbounded; mod bounded; mod single; mod unbounded; mod sync; /// A concurrent queue. /// /// # Examples /// /// ``` /// use concurrent_queue::{ConcurrentQueue, PopError, PushError}; /// /// let q = ConcurrentQueue::bounded(2); /// /// assert_eq!(q.push('a'), Ok(())); /// assert_eq!(q.push('b'), Ok(())); /// assert_eq!(q.push('c'), Err(PushError::Full('c'))); /// /// assert_eq!(q.pop(), Ok('a')); /// assert_eq!(q.pop(), Ok('b')); /// assert_eq!(q.pop(), Err(PopError::Empty)); /// ``` pub struct ConcurrentQueue(Inner); unsafe impl Send for ConcurrentQueue {} unsafe impl Sync for ConcurrentQueue {} impl UnwindSafe for ConcurrentQueue {} impl RefUnwindSafe for ConcurrentQueue {} enum Inner { Single(Single), Bounded(Box>), Unbounded(Box>), } impl ConcurrentQueue { /// Creates a new bounded queue. /// /// The queue allocates enough space for `cap` items. /// /// # Panics /// /// If the capacity is zero, this constructor will panic. /// /// # Examples /// /// ``` /// use concurrent_queue::ConcurrentQueue; /// /// let q = ConcurrentQueue::::bounded(100); /// ``` pub fn bounded(cap: usize) -> ConcurrentQueue { if cap == 1 { ConcurrentQueue(Inner::Single(Single::new())) } else { ConcurrentQueue(Inner::Bounded(Box::new(Bounded::new(cap)))) } } /// Creates a new unbounded queue. /// /// # Examples /// /// ``` /// use concurrent_queue::ConcurrentQueue; /// /// let q = ConcurrentQueue::::unbounded(); /// ``` pub fn unbounded() -> ConcurrentQueue { ConcurrentQueue(Inner::Unbounded(Box::new(Unbounded::new()))) } /// Attempts to push an item into the queue. /// /// If the queue is full or closed, the item is returned back as an error. /// /// # Examples /// /// ``` /// use concurrent_queue::{ConcurrentQueue, PushError}; /// /// let q = ConcurrentQueue::bounded(1); /// /// // Push succeeds because there is space in the queue. /// assert_eq!(q.push(10), Ok(())); /// /// // Push errors because the queue is now full. /// assert_eq!(q.push(20), Err(PushError::Full(20))); /// /// // Close the queue, which will prevent further pushes. /// q.close(); /// /// // Pushing now errors indicating the queue is closed. /// assert_eq!(q.push(20), Err(PushError::Closed(20))); /// /// // Pop the single item in the queue. /// assert_eq!(q.pop(), Ok(10)); /// /// // Even though there is space, no more items can be pushed. /// assert_eq!(q.push(20), Err(PushError::Closed(20))); /// ``` pub fn push(&self, value: T) -> Result<(), PushError> { match &self.0 { Inner::Single(q) => q.push(value), Inner::Bounded(q) => q.push(value), Inner::Unbounded(q) => q.push(value), } } /// Attempts to pop an item from the queue. /// /// If the queue is empty, an error is returned. /// /// # Examples /// /// ``` /// use concurrent_queue::{ConcurrentQueue, PopError}; /// /// let q = ConcurrentQueue::bounded(1); /// /// // Pop errors when the queue is empty. /// assert_eq!(q.pop(), Err(PopError::Empty)); /// /// // Push one item and close the queue. /// assert_eq!(q.push(10), Ok(())); /// q.close(); /// /// // Remaining items can be popped. /// assert_eq!(q.pop(), Ok(10)); /// /// // Again, pop errors when the queue is empty, /// // but now also indicates that the queue is closed. /// assert_eq!(q.pop(), Err(PopError::Closed)); /// ``` pub fn pop(&self) -> Result { match &self.0 { Inner::Single(q) => q.pop(), Inner::Bounded(q) => q.pop(), Inner::Unbounded(q) => q.pop(), } } /// Get an iterator over the items in the queue. /// /// The iterator will continue until the queue is empty or closed. It will never block; /// if the queue is empty, the iterator will return `None`. If new items are pushed into /// the queue, the iterator may return `Some` in the future after returning `None`. /// /// # Examples /// /// ``` /// use concurrent_queue::ConcurrentQueue; /// /// let q = ConcurrentQueue::bounded(5); /// q.push(1).unwrap(); /// q.push(2).unwrap(); /// q.push(3).unwrap(); /// /// let mut iter = q.try_iter(); /// assert_eq!(iter.by_ref().sum::(), 6); /// assert_eq!(iter.next(), None); /// /// // Pushing more items will make them available to the iterator. /// q.push(4).unwrap(); /// assert_eq!(iter.next(), Some(4)); /// assert_eq!(iter.next(), None); /// ``` pub fn try_iter(&self) -> TryIter<'_, T> { TryIter { queue: self } } /// Returns `true` if the queue is empty. /// /// # Examples /// /// ``` /// use concurrent_queue::ConcurrentQueue; /// /// let q = ConcurrentQueue::::unbounded(); /// /// assert!(q.is_empty()); /// q.push(1).unwrap(); /// assert!(!q.is_empty()); /// ``` pub fn is_empty(&self) -> bool { match &self.0 { Inner::Single(q) => q.is_empty(), Inner::Bounded(q) => q.is_empty(), Inner::Unbounded(q) => q.is_empty(), } } /// Returns `true` if the queue is full. /// /// An unbounded queue is never full. /// /// # Examples /// /// ``` /// use concurrent_queue::ConcurrentQueue; /// /// let q = ConcurrentQueue::bounded(1); /// /// assert!(!q.is_full()); /// q.push(1).unwrap(); /// assert!(q.is_full()); /// ``` pub fn is_full(&self) -> bool { match &self.0 { Inner::Single(q) => q.is_full(), Inner::Bounded(q) => q.is_full(), Inner::Unbounded(q) => q.is_full(), } } /// Returns the number of items in the queue. /// /// # Examples /// /// ``` /// use concurrent_queue::ConcurrentQueue; /// /// let q = ConcurrentQueue::unbounded(); /// assert_eq!(q.len(), 0); /// /// assert_eq!(q.push(10), Ok(())); /// assert_eq!(q.len(), 1); /// /// assert_eq!(q.push(20), Ok(())); /// assert_eq!(q.len(), 2); /// ``` pub fn len(&self) -> usize { match &self.0 { Inner::Single(q) => q.len(), Inner::Bounded(q) => q.len(), Inner::Unbounded(q) => q.len(), } } /// Returns the capacity of the queue. /// /// Unbounded queues have infinite capacity, represented as [`None`]. /// /// # Examples /// /// ``` /// use concurrent_queue::ConcurrentQueue; /// /// let q = ConcurrentQueue::::bounded(7); /// assert_eq!(q.capacity(), Some(7)); /// /// let q = ConcurrentQueue::::unbounded(); /// assert_eq!(q.capacity(), None); /// ``` pub fn capacity(&self) -> Option { match &self.0 { Inner::Single(_) => Some(1), Inner::Bounded(q) => Some(q.capacity()), Inner::Unbounded(_) => None, } } /// Closes the queue. /// /// Returns `true` if this call closed the queue, or `false` if it was already closed. /// /// When a queue is closed, no more items can be pushed but the remaining items can still be /// popped. /// /// # Examples /// /// ``` /// use concurrent_queue::{ConcurrentQueue, PopError, PushError}; /// /// let q = ConcurrentQueue::unbounded(); /// assert_eq!(q.push(10), Ok(())); /// /// assert!(q.close()); // `true` because this call closes the queue. /// assert!(!q.close()); // `false` because the queue is already closed. /// /// // Cannot push any more items when closed. /// assert_eq!(q.push(20), Err(PushError::Closed(20))); /// /// // Remaining items can still be popped. /// assert_eq!(q.pop(), Ok(10)); /// /// // When no more items are present, the error is `Closed`. /// assert_eq!(q.pop(), Err(PopError::Closed)); /// ``` pub fn close(&self) -> bool { match &self.0 { Inner::Single(q) => q.close(), Inner::Bounded(q) => q.close(), Inner::Unbounded(q) => q.close(), } } /// Returns `true` if the queue is closed. /// /// # Examples /// /// ``` /// use concurrent_queue::ConcurrentQueue; /// /// let q = ConcurrentQueue::::unbounded(); /// /// assert!(!q.is_closed()); /// q.close(); /// assert!(q.is_closed()); /// ``` pub fn is_closed(&self) -> bool { match &self.0 { Inner::Single(q) => q.is_closed(), Inner::Bounded(q) => q.is_closed(), Inner::Unbounded(q) => q.is_closed(), } } } impl fmt::Debug for ConcurrentQueue { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_struct("ConcurrentQueue") .field("len", &self.len()) .field("capacity", &self.capacity()) .field("is_closed", &self.is_closed()) .finish() } } /// An iterator that pops items from a [`ConcurrentQueue`]. /// /// This iterator will never block; it will return `None` once the queue has /// been exhausted. Calling `next` after `None` may yield `Some(item)` if more items /// are pushed to the queue. #[must_use = "iterators are lazy and do nothing unless consumed"] #[derive(Clone)] pub struct TryIter<'a, T> { queue: &'a ConcurrentQueue, } impl fmt::Debug for TryIter<'_, T> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.debug_tuple("Iter").field(&self.queue).finish() } } impl Iterator for TryIter<'_, T> { type Item = T; fn next(&mut self) -> Option { self.queue.pop().ok() } } /// Error which occurs when popping from an empty queue. #[derive(Clone, Copy, Eq, PartialEq)] pub enum PopError { /// The queue is empty but not closed. Empty, /// The queue is empty and closed. Closed, } impl PopError { /// Returns `true` if the queue is empty but not closed. pub fn is_empty(&self) -> bool { match self { PopError::Empty => true, PopError::Closed => false, } } /// Returns `true` if the queue is empty and closed. pub fn is_closed(&self) -> bool { match self { PopError::Empty => false, PopError::Closed => true, } } } #[cfg(feature = "std")] impl error::Error for PopError {} impl fmt::Debug for PopError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self { PopError::Empty => write!(f, "Empty"), PopError::Closed => write!(f, "Closed"), } } } impl fmt::Display for PopError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self { PopError::Empty => write!(f, "Empty"), PopError::Closed => write!(f, "Closed"), } } } /// Error which occurs when pushing into a full or closed queue. #[derive(Clone, Copy, Eq, PartialEq)] pub enum PushError { /// The queue is full but not closed. Full(T), /// The queue is closed. Closed(T), } impl PushError { /// Unwraps the item that couldn't be pushed. pub fn into_inner(self) -> T { match self { PushError::Full(t) => t, PushError::Closed(t) => t, } } /// Returns `true` if the queue is full but not closed. pub fn is_full(&self) -> bool { match self { PushError::Full(_) => true, PushError::Closed(_) => false, } } /// Returns `true` if the queue is closed. pub fn is_closed(&self) -> bool { match self { PushError::Full(_) => false, PushError::Closed(_) => true, } } } #[cfg(feature = "std")] impl error::Error for PushError {} impl fmt::Debug for PushError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self { PushError::Full(t) => f.debug_tuple("Full").field(t).finish(), PushError::Closed(t) => f.debug_tuple("Closed").field(t).finish(), } } } impl fmt::Display for PushError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self { PushError::Full(_) => write!(f, "Full"), PushError::Closed(_) => write!(f, "Closed"), } } } /// Equivalent to `atomic::fence(Ordering::SeqCst)`, but in some cases faster. #[inline] fn full_fence() { #[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), not(miri), not(loom)))] { use core::{arch::asm, cell::UnsafeCell}; // HACK(stjepang): On x86 architectures there are two different ways of executing // a `SeqCst` fence. // // 1. `atomic::fence(SeqCst)`, which compiles into a `mfence` instruction. // 2. A `lock ` instruction. // // Both instructions have the effect of a full barrier, but empirical benchmarks have shown // that the second one is sometimes a bit faster. let a = UnsafeCell::new(0_usize); // It is common to use `lock or` here, but when using a local variable, `lock not`, which // does not change the flag, should be slightly more efficient. // Refs: https://www.felixcloutier.com/x86/not unsafe { #[cfg(target_pointer_width = "64")] asm!("lock not qword ptr [{0}]", in(reg) a.get(), options(nostack, preserves_flags)); #[cfg(target_pointer_width = "32")] asm!("lock not dword ptr [{0:e}]", in(reg) a.get(), options(nostack, preserves_flags)); } return; } #[allow(unreachable_code)] { atomic::fence(Ordering::SeqCst); } } concurrent-queue-2.3.0/src/single.rs000064400000000000000000000072741046102023000155620ustar 00000000000000use core::mem::MaybeUninit; use crate::sync::atomic::{AtomicUsize, Ordering}; use crate::sync::cell::UnsafeCell; #[allow(unused_imports)] use crate::sync::prelude::*; use crate::{busy_wait, PopError, PushError}; const LOCKED: usize = 1 << 0; const PUSHED: usize = 1 << 1; const CLOSED: usize = 1 << 2; /// A single-element queue. pub struct Single { state: AtomicUsize, slot: UnsafeCell>, } impl Single { /// Creates a new single-element queue. pub fn new() -> Single { Single { state: AtomicUsize::new(0), slot: UnsafeCell::new(MaybeUninit::uninit()), } } /// Attempts to push an item into the queue. pub fn push(&self, value: T) -> Result<(), PushError> { // Lock and fill the slot. let state = self .state .compare_exchange(0, LOCKED | PUSHED, Ordering::SeqCst, Ordering::SeqCst) .unwrap_or_else(|x| x); if state == 0 { // Write the value and unlock. self.slot.with_mut(|slot| unsafe { slot.write(MaybeUninit::new(value)); }); self.state.fetch_and(!LOCKED, Ordering::Release); Ok(()) } else if state & CLOSED != 0 { Err(PushError::Closed(value)) } else { Err(PushError::Full(value)) } } /// Attempts to pop an item from the queue. pub fn pop(&self) -> Result { let mut state = PUSHED; loop { // Lock and empty the slot. let prev = self .state .compare_exchange( state, (state | LOCKED) & !PUSHED, Ordering::SeqCst, Ordering::SeqCst, ) .unwrap_or_else(|x| x); if prev == state { // Read the value and unlock. let value = self .slot .with_mut(|slot| unsafe { slot.read().assume_init() }); self.state.fetch_and(!LOCKED, Ordering::Release); return Ok(value); } if prev & PUSHED == 0 { if prev & CLOSED == 0 { return Err(PopError::Empty); } else { return Err(PopError::Closed); } } if prev & LOCKED == 0 { state = prev; } else { busy_wait(); state = prev & !LOCKED; } } } /// Returns the number of items in the queue. pub fn len(&self) -> usize { usize::from(self.state.load(Ordering::SeqCst) & PUSHED != 0) } /// Returns `true` if the queue is empty. pub fn is_empty(&self) -> bool { self.len() == 0 } /// Returns `true` if the queue is full. pub fn is_full(&self) -> bool { self.len() == 1 } /// Closes the queue. /// /// Returns `true` if this call closed the queue. pub fn close(&self) -> bool { let state = self.state.fetch_or(CLOSED, Ordering::SeqCst); state & CLOSED == 0 } /// Returns `true` if the queue is closed. pub fn is_closed(&self) -> bool { self.state.load(Ordering::SeqCst) & CLOSED != 0 } } impl Drop for Single { fn drop(&mut self) { // Drop the value in the slot. let Self { state, slot } = self; state.with_mut(|state| { if *state & PUSHED != 0 { slot.with_mut(|slot| unsafe { let value = &mut *slot; value.as_mut_ptr().drop_in_place(); }); } }); } } concurrent-queue-2.3.0/src/sync.rs000064400000000000000000000051531046102023000152470ustar 00000000000000//! Synchronization facade to choose between `core` primitives and `loom` primitives. #[cfg(all(feature = "portable-atomic", not(loom)))] mod sync_impl { pub(crate) use core::cell; pub(crate) use portable_atomic as atomic; #[cfg(not(feature = "std"))] pub(crate) use atomic::hint::spin_loop; #[cfg(feature = "std")] pub(crate) use std::thread::yield_now; } #[cfg(all(not(feature = "portable-atomic"), not(loom)))] mod sync_impl { pub(crate) use core::cell; pub(crate) use core::sync::atomic; #[cfg(not(feature = "std"))] #[inline] pub(crate) fn spin_loop() { #[allow(deprecated)] atomic::spin_loop_hint(); } #[cfg(feature = "std")] pub(crate) use std::thread::yield_now; } #[cfg(loom)] mod sync_impl { pub(crate) use loom::cell; pub(crate) mod atomic { pub(crate) use loom::sync::atomic::*; } pub(crate) use loom::thread::yield_now; } pub(crate) use sync_impl::*; /// Notify the CPU that we are currently busy-waiting. #[inline] pub(crate) fn busy_wait() { #[cfg(feature = "std")] yield_now(); #[cfg(not(feature = "std"))] spin_loop(); } #[cfg(loom)] pub(crate) mod prelude {} #[cfg(not(loom))] pub(crate) mod prelude { use super::{atomic, cell}; /// Emulate `loom::UnsafeCell`'s API. pub(crate) trait UnsafeCellExt { type Value; fn with(&self, f: F) -> R where F: FnOnce(*const Self::Value) -> R; fn with_mut(&self, f: F) -> R where F: FnOnce(*mut Self::Value) -> R; } impl UnsafeCellExt for cell::UnsafeCell { type Value = T; fn with(&self, f: F) -> R where F: FnOnce(*const Self::Value) -> R, { f(self.get()) } fn with_mut(&self, f: F) -> R where F: FnOnce(*mut Self::Value) -> R, { f(self.get()) } } /// Emulate `loom::Atomic*`'s API. pub(crate) trait AtomicExt { type Value; fn with_mut(&mut self, f: F) -> R where F: FnOnce(&mut Self::Value) -> R; } impl AtomicExt for atomic::AtomicUsize { type Value = usize; fn with_mut(&mut self, f: F) -> R where F: FnOnce(&mut Self::Value) -> R, { f(self.get_mut()) } } impl AtomicExt for atomic::AtomicPtr { type Value = *mut T; fn with_mut(&mut self, f: F) -> R where F: FnOnce(&mut Self::Value) -> R, { f(self.get_mut()) } } } concurrent-queue-2.3.0/src/unbounded.rs000064400000000000000000000366461046102023000162710ustar 00000000000000use alloc::boxed::Box; use core::mem::MaybeUninit; use core::ptr; use crossbeam_utils::CachePadded; use crate::sync::atomic::{AtomicPtr, AtomicUsize, Ordering}; use crate::sync::cell::UnsafeCell; #[allow(unused_imports)] use crate::sync::prelude::*; use crate::{busy_wait, PopError, PushError}; // 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 items a block can hold. const BLOCK_CAP: usize = LAP - 1; // How many lower bits are reserved for metadata. const SHIFT: usize = 1; // Has two different purposes: // * If set in head, indicates that the block is not the last one. // * If set in tail, indicates that the queue is closed. const MARK_BIT: usize = 1; /// A slot in a block. struct Slot { /// The value. value: UnsafeCell>, /// The state of the slot. state: AtomicUsize, } impl Slot { #[cfg(not(loom))] const UNINIT: Slot = Slot { value: UnsafeCell::new(MaybeUninit::uninit()), state: AtomicUsize::new(0), }; #[cfg(not(loom))] fn uninit_block() -> [Slot; BLOCK_CAP] { [Self::UNINIT; BLOCK_CAP] } #[cfg(loom)] fn uninit_block() -> [Slot; BLOCK_CAP] { // Repeat this expression 31 times. // Update if we change BLOCK_CAP macro_rules! repeat_31 { ($e: expr) => { [ $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, $e, ] }; } repeat_31!(Slot { value: UnsafeCell::new(MaybeUninit::uninit()), state: AtomicUsize::new(0), }) } /// Waits until a value is written into the slot. fn wait_write(&self) { while self.state.load(Ordering::Acquire) & WRITE == 0 { busy_wait(); } } } /// A block in a linked list. /// /// Each block in the list can hold up to `BLOCK_CAP` values. struct Block { /// The next block in the linked list. next: AtomicPtr>, /// Slots for values. slots: [Slot; BLOCK_CAP], } impl Block { /// Creates an empty block. fn new() -> Block { Block { next: AtomicPtr::new(ptr::null_mut()), slots: Slot::uninit_block(), } } /// Waits until the next pointer is set. fn wait_next(&self) -> *mut Block { loop { let next = self.next.load(Ordering::Acquire); if !next.is_null() { return next; } busy_wait(); } } /// Sets the `DESTROY` bit in slots starting from `start` and destroys the block. unsafe fn destroy(this: *mut Block, 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 { /// The index in the queue. index: AtomicUsize, /// The block in the linked list. block: AtomicPtr>, } /// An unbounded queue. pub struct Unbounded { /// The head of the queue. head: CachePadded>, /// The tail of the queue. tail: CachePadded>, } impl Unbounded { /// Creates a new unbounded queue. pub fn new() -> Unbounded { Unbounded { 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), }), } } /// Pushes an item into the queue. pub fn push(&self, value: T) -> Result<(), PushError> { let mut tail = self.tail.index.load(Ordering::Acquire); let mut block = self.tail.block.load(Ordering::Acquire); let mut next_block = None; loop { // Check if the queue is closed. if tail & MARK_BIT != 0 { return Err(PushError::Closed(value)); } // 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 { busy_wait(); 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::::new())); } // If this is the first value to be pushed into the queue, we need to allocate the // first block and install it. if block.is_null() { let new = Box::into_raw(Box::new(Block::::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()); self.tail.block.store(next_block, Ordering::Release); self.tail.index.fetch_add(1 << SHIFT, Ordering::Release); (*block).next.store(next_block, Ordering::Release); } // Write the value into the slot. let slot = (*block).slots.get_unchecked(offset); slot.value.with_mut(|slot| { slot.write(MaybeUninit::new(value)); }); slot.state.fetch_or(WRITE, Ordering::Release); return Ok(()); }, Err(t) => { tail = t; block = self.tail.block.load(Ordering::Acquire); } } } } /// Pops an item from the queue. pub fn pop(&self) -> Result { 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 { busy_wait(); 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 & MARK_BIT == 0 { crate::full_fence(); 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 { // Check if the queue is closed. if tail & MARK_BIT != 0 { return Err(PopError::Closed); } else { return Err(PopError::Empty); } } // If head and tail are not in the same block, set `MARK_BIT` in head. if (head >> SHIFT) / LAP != (tail >> SHIFT) / LAP { new_head |= MARK_BIT; } } // The block can be null here only if the first push operation is in progress. if block.is_null() { busy_wait(); 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 & !MARK_BIT).wrapping_add(1 << SHIFT); if !(*next).next.load(Ordering::Relaxed).is_null() { next_index |= MARK_BIT; } 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.with_mut(|slot| slot.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 Ok(value); }, Err(h) => { head = h; block = self.head.block.load(Ordering::Acquire); } } } } /// Returns the number of items in the queue. 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; } } } /// Returns `true` if the queue 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 `true` if the queue is full. pub fn is_full(&self) -> bool { false } /// Closes the queue. /// /// Returns `true` if this call closed the queue. pub fn close(&self) -> bool { let tail = self.tail.index.fetch_or(MARK_BIT, Ordering::SeqCst); tail & MARK_BIT == 0 } /// Returns `true` if the queue is closed. pub fn is_closed(&self) -> bool { self.tail.index.load(Ordering::SeqCst) & MARK_BIT != 0 } } impl Drop for Unbounded { fn drop(&mut self) { let Self { head, tail } = self; let Position { index: head, block } = &mut **head; head.with_mut(|&mut mut head| { tail.index.with_mut(|&mut mut tail| { // 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. block.with_mut(|block| { let slot = (**block).slots.get_unchecked(offset); slot.value.with_mut(|slot| { let value = &mut *slot; value.as_mut_ptr().drop_in_place(); }); }); } else { // Deallocate the block and move to the next one. block.with_mut(|block| { let next_block = (**block).next.with_mut(|next| *next); drop(Box::from_raw(*block)); *block = next_block; }); } head = head.wrapping_add(1 << SHIFT); } // Deallocate the last remaining block. block.with_mut(|block| { if !block.is_null() { drop(Box::from_raw(*block)); } }); } }); }); } } concurrent-queue-2.3.0/tests/bounded.rs000064400000000000000000000132751046102023000162720ustar 00000000000000#![allow(clippy::bool_assert_comparison)] use std::sync::atomic::{AtomicUsize, Ordering}; use concurrent_queue::{ConcurrentQueue, PopError, PushError}; use easy_parallel::Parallel; #[test] fn smoke() { let q = ConcurrentQueue::bounded(2); q.push(7).unwrap(); assert_eq!(q.pop(), Ok(7)); q.push(8).unwrap(); assert_eq!(q.pop(), Ok(8)); assert!(q.pop().is_err()); } #[test] fn capacity() { for i in 1..10 { let q = ConcurrentQueue::::bounded(i); assert_eq!(q.capacity(), Some(i)); } } #[test] #[should_panic(expected = "capacity must be positive")] fn zero_capacity() { let _ = ConcurrentQueue::::bounded(0); } #[test] fn len_empty_full() { let q = ConcurrentQueue::bounded(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 = if cfg!(miri) { 50 } else { 25_000 }; const CAP: usize = if cfg!(miri) { 50 } else { 1000 }; let q = ConcurrentQueue::bounded(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); Parallel::new() .add(|| { for i in 0..COUNT { loop { if let Ok(x) = q.pop() { assert_eq!(x, i); break; } } let len = q.len(); assert!(len <= CAP); } }) .add(|| { for i in 0..COUNT { while q.push(i).is_err() {} let len = q.len(); assert!(len <= CAP); } }) .run(); assert_eq!(q.len(), 0); } #[test] fn close() { let q = ConcurrentQueue::bounded(2); assert_eq!(q.push(10), Ok(())); assert!(!q.is_closed()); assert!(q.close()); assert!(q.is_closed()); assert!(!q.close()); assert_eq!(q.push(20), Err(PushError::Closed(20))); assert_eq!(q.pop(), Ok(10)); assert_eq!(q.pop(), Err(PopError::Closed)); } #[test] fn spsc() { const COUNT: usize = if cfg!(miri) { 100 } else { 100_000 }; let q = ConcurrentQueue::bounded(3); Parallel::new() .add(|| { for i in 0..COUNT { loop { if let Ok(x) = q.pop() { assert_eq!(x, i); break; } } } assert!(q.pop().is_err()); }) .add(|| { for i in 0..COUNT { while q.push(i).is_err() {} } }) .run(); } #[test] fn mpmc() { const COUNT: usize = if cfg!(miri) { 100 } else { 25_000 }; const THREADS: usize = 4; let q = ConcurrentQueue::::bounded(3); let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::>(); Parallel::new() .each(0..THREADS, |_| { for _ in 0..COUNT { let n = loop { if let Ok(x) = q.pop() { break x; } }; v[n].fetch_add(1, Ordering::SeqCst); } }) .each(0..THREADS, |_| { for i in 0..COUNT { while q.push(i).is_err() {} } }) .run(); for c in v { assert_eq!(c.load(Ordering::SeqCst), THREADS); } } #[test] fn drops() { const RUNS: usize = if cfg!(miri) { 10 } else { 100 }; const STEPS: usize = if cfg!(miri) { 100 } else { 10_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); } } for _ in 0..RUNS { let steps = fastrand::usize(..STEPS); let additional = fastrand::usize(..50); DROPS.store(0, Ordering::SeqCst); let q = ConcurrentQueue::bounded(50); Parallel::new() .add(|| { for _ in 0..steps { while q.pop().is_err() {} } }) .add(|| { for _ in 0..steps { while q.push(DropCounter).is_err() { DROPS.fetch_sub(1, Ordering::SeqCst); } } }) .run(); 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 = if cfg!(miri) { 500 } else { 25_000 }; const THREADS: usize = 4; let q = ConcurrentQueue::bounded(THREADS); Parallel::new() .each(0..THREADS, |_| { for _ in 0..COUNT { while q.push(0).is_err() {} q.pop().unwrap(); } }) .run(); } concurrent-queue-2.3.0/tests/loom.rs000064400000000000000000000144401046102023000156130ustar 00000000000000#![cfg(loom)] use concurrent_queue::{ConcurrentQueue, PopError, PushError}; use loom::sync::atomic::{AtomicUsize, Ordering}; use loom::sync::{Arc, Condvar, Mutex}; use loom::thread; /// A basic MPMC channel based on a ConcurrentQueue and loom primitives. struct Channel { /// The queue used to contain items. queue: ConcurrentQueue, /// The number of senders. senders: AtomicUsize, /// The number of receivers. receivers: AtomicUsize, /// The event that is signaled when a new item is pushed. push_event: Event, /// The event that is signaled when a new item is popped. pop_event: Event, } /// The sending side of a channel. struct Sender { /// The channel. channel: Arc>, } /// The receiving side of a channel. struct Receiver { /// The channel. channel: Arc>, } /// Create a new pair of senders/receivers based on a queue. fn pair(queue: ConcurrentQueue) -> (Sender, Receiver) { let channel = Arc::new(Channel { queue, senders: AtomicUsize::new(1), receivers: AtomicUsize::new(1), push_event: Event::new(), pop_event: Event::new(), }); ( Sender { channel: channel.clone(), }, Receiver { channel }, ) } impl Clone for Sender { fn clone(&self) -> Self { self.channel.senders.fetch_add(1, Ordering::SeqCst); Sender { channel: self.channel.clone(), } } } impl Drop for Sender { fn drop(&mut self) { if self.channel.senders.fetch_sub(1, Ordering::SeqCst) == 1 { // Close the channel and notify the receivers. self.channel.queue.close(); self.channel.push_event.signal_all(); } } } impl Clone for Receiver { fn clone(&self) -> Self { self.channel.receivers.fetch_add(1, Ordering::SeqCst); Receiver { channel: self.channel.clone(), } } } impl Drop for Receiver { fn drop(&mut self) { if self.channel.receivers.fetch_sub(1, Ordering::SeqCst) == 1 { // Close the channel and notify the senders. self.channel.queue.close(); self.channel.pop_event.signal_all(); } } } impl Sender { /// Send a value. /// /// Returns an error with the value if the channel is closed. fn send(&self, mut value: T) -> Result<(), T> { loop { match self.channel.queue.push(value) { Ok(()) => { // Notify a single receiver. self.channel.push_event.signal(); return Ok(()); } Err(PushError::Closed(val)) => return Err(val), Err(PushError::Full(val)) => { // Wait for a receiver to pop an item. value = val; self.channel.pop_event.wait(); } } } } } impl Receiver { /// Receive a value. /// /// Returns an error if the channel is closed. fn recv(&self) -> Result { loop { match self.channel.queue.pop() { Ok(value) => { // Notify a single sender. self.channel.pop_event.signal(); return Ok(value); } Err(PopError::Closed) => return Err(()), Err(PopError::Empty) => { // Wait for a sender to push an item. self.channel.push_event.wait(); } } } } } /// An event that can be waited on and then signaled. struct Event { /// The condition variable used to wait on the event. condvar: Condvar, /// The mutex used to protect the event. /// /// Inside is the event's state. The first bit is used to indicate if the /// notify_one method was called. The second bit is used to indicate if the /// notify_all method was called. mutex: Mutex, } impl Event { /// Create a new event. fn new() -> Self { Self { condvar: Condvar::new(), mutex: Mutex::new(0), } } /// Wait for the event to be signaled. fn wait(&self) { let mut state = self.mutex.lock().unwrap(); loop { if *state & 0b11 != 0 { // The event was signaled. *state &= !0b01; return; } // Wait for the event to be signaled. state = self.condvar.wait(state).unwrap(); } } /// Signal the event. fn signal(&self) { let mut state = self.mutex.lock().unwrap(); *state |= 1; drop(state); self.condvar.notify_one(); } /// Signal the event, but notify all waiters. fn signal_all(&self) { let mut state = self.mutex.lock().unwrap(); *state |= 3; drop(state); self.condvar.notify_all(); } } /// Wrapper to run tests on all three queues. fn run_test, usize) + Send + Sync + Clone + 'static>(f: F) { // The length of a loom test seems to increase exponentially the higher this number is. const LIMIT: usize = 4; let fc = f.clone(); loom::model(move || { fc(ConcurrentQueue::bounded(1), LIMIT); }); let fc = f.clone(); loom::model(move || { fc(ConcurrentQueue::bounded(LIMIT / 2), LIMIT); }); loom::model(move || { f(ConcurrentQueue::unbounded(), LIMIT); }); } #[test] fn spsc() { run_test(|q, limit| { // Create a new pair of senders/receivers. let (tx, rx) = pair(q); // Push each onto a thread and run them. let handle = thread::spawn(move || { for i in 0..limit { if tx.send(i).is_err() { break; } } }); let mut recv_values = vec![]; loop { match rx.recv() { Ok(value) => recv_values.push(value), Err(()) => break, } } // Values may not be in order. recv_values.sort_unstable(); assert_eq!(recv_values, (0..limit).collect::>()); // Join the handle before we exit. handle.join().unwrap(); }); } concurrent-queue-2.3.0/tests/single.rs000064400000000000000000000102571046102023000161300ustar 00000000000000#![allow(clippy::bool_assert_comparison)] use std::sync::atomic::{AtomicUsize, Ordering}; use concurrent_queue::{ConcurrentQueue, PopError, PushError}; use easy_parallel::Parallel; #[test] fn smoke() { let q = ConcurrentQueue::bounded(1); q.push(7).unwrap(); assert_eq!(q.pop(), Ok(7)); q.push(8).unwrap(); assert_eq!(q.pop(), Ok(8)); assert!(q.pop().is_err()); } #[test] fn capacity() { let q = ConcurrentQueue::::bounded(1); assert_eq!(q.capacity(), Some(1)); } #[test] fn len_empty_full() { let q = ConcurrentQueue::bounded(1); 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(), true); q.pop().unwrap(); assert_eq!(q.len(), 0); assert_eq!(q.is_empty(), true); assert_eq!(q.is_full(), false); } #[test] fn close() { let q = ConcurrentQueue::::bounded(1); assert_eq!(q.push(10), Ok(())); assert!(!q.is_closed()); assert!(q.close()); assert!(q.is_closed()); assert!(!q.close()); assert_eq!(q.push(20), Err(PushError::Closed(20))); assert_eq!(q.pop(), Ok(10)); assert_eq!(q.pop(), Err(PopError::Closed)); } #[test] fn spsc() { const COUNT: usize = if cfg!(miri) { 100 } else { 100_000 }; let q = ConcurrentQueue::bounded(1); Parallel::new() .add(|| { for i in 0..COUNT { loop { if let Ok(x) = q.pop() { assert_eq!(x, i); break; } } } assert!(q.pop().is_err()); }) .add(|| { for i in 0..COUNT { while q.push(i).is_err() {} } }) .run(); } #[test] fn mpmc() { const COUNT: usize = if cfg!(miri) { 100 } else { 25_000 }; const THREADS: usize = 1; let q = ConcurrentQueue::::bounded(THREADS); let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::>(); Parallel::new() .each(0..THREADS, |_| { for _ in 0..COUNT { let n = loop { if let Ok(x) = q.pop() { break x; } }; v[n].fetch_add(1, Ordering::SeqCst); } }) .each(0..THREADS, |_| { for i in 0..COUNT { while q.push(i).is_err() {} } }) .run(); for c in v { assert_eq!(c.load(Ordering::SeqCst), THREADS); } } #[test] fn drops() { const RUNS: usize = if cfg!(miri) { 20 } else { 100 }; const STEPS: usize = if cfg!(miri) { 100 } else { 10_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); } } for _ in 0..RUNS { let steps = fastrand::usize(..STEPS); let additional = fastrand::usize(0..=1); DROPS.store(0, Ordering::SeqCst); let q = ConcurrentQueue::bounded(1); Parallel::new() .add(|| { for _ in 0..steps { while q.pop().is_err() {} } }) .add(|| { for _ in 0..steps { while q.push(DropCounter).is_err() { DROPS.fetch_sub(1, Ordering::SeqCst); } } }) .run(); 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 = if cfg!(miri) { 500 } else { 25_000 }; const THREADS: usize = 4; let q = ConcurrentQueue::bounded(1); Parallel::new() .each(0..THREADS, |_| { for _ in 0..COUNT { while q.push(0).is_err() {} q.pop().unwrap(); } }) .run(); } concurrent-queue-2.3.0/tests/unbounded.rs000064400000000000000000000074441046102023000166360ustar 00000000000000#![allow(clippy::bool_assert_comparison)] use std::sync::atomic::{AtomicUsize, Ordering}; use concurrent_queue::{ConcurrentQueue, PopError, PushError}; use easy_parallel::Parallel; #[test] fn smoke() { let q = ConcurrentQueue::unbounded(); q.push(7).unwrap(); assert_eq!(q.pop(), Ok(7)); q.push(8).unwrap(); assert_eq!(q.pop(), Ok(8)); assert!(q.pop().is_err()); } #[test] fn len_empty_full() { let q = ConcurrentQueue::unbounded(); assert_eq!(q.len(), 0); assert_eq!(q.is_empty(), true); q.push(()).unwrap(); 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 = ConcurrentQueue::unbounded(); assert_eq!(q.len(), 0); 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); } #[test] fn close() { let q = ConcurrentQueue::unbounded(); assert_eq!(q.push(10), Ok(())); assert!(!q.is_closed()); assert!(q.close()); assert!(q.is_closed()); assert!(!q.close()); assert_eq!(q.push(20), Err(PushError::Closed(20))); assert_eq!(q.pop(), Ok(10)); assert_eq!(q.pop(), Err(PopError::Closed)); } #[test] fn spsc() { const COUNT: usize = if cfg!(miri) { 100 } else { 100_000 }; let q = ConcurrentQueue::unbounded(); Parallel::new() .add(|| { for i in 0..COUNT { loop { if let Ok(x) = q.pop() { assert_eq!(x, i); break; } } } assert!(q.pop().is_err()); }) .add(|| { for i in 0..COUNT { q.push(i).unwrap(); } }) .run(); } #[test] fn mpmc() { const COUNT: usize = if cfg!(miri) { 100 } else { 25_000 }; const THREADS: usize = 4; let q = ConcurrentQueue::::unbounded(); let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::>(); Parallel::new() .each(0..THREADS, |_| { for _ in 0..COUNT { let n = loop { if let Ok(x) = q.pop() { break x; } }; v[n].fetch_add(1, Ordering::SeqCst); } }) .each(0..THREADS, |_| { for i in 0..COUNT { q.push(i).unwrap(); } }) .run(); for c in v { assert_eq!(c.load(Ordering::SeqCst), THREADS); } } #[test] fn drops() { const RUNS: usize = if cfg!(miri) { 20 } else { 100 }; const STEPS: usize = if cfg!(miri) { 100 } else { 10_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); } } for _ in 0..RUNS { let steps = fastrand::usize(0..STEPS); let additional = fastrand::usize(0..1000); DROPS.store(0, Ordering::SeqCst); let q = ConcurrentQueue::unbounded(); Parallel::new() .add(|| { for _ in 0..steps { while q.pop().is_err() {} } }) .add(|| { for _ in 0..steps { q.push(DropCounter).unwrap(); } }) .run(); 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); } }