crossbeam-queue-0.3.11/.cargo_vcs_info.json0000644000000001550000000000100142170ustar { "git": { "sha1": "9c3182abebb36bdc9446d75d4644190fef70fa01" }, "path_in_vcs": "crossbeam-queue" }crossbeam-queue-0.3.11/CHANGELOG.md000064400000000000000000000033101046102023000146140ustar 00000000000000# Version 0.3.11 - Remove dependency on `cfg-if`. (#1072) # Version 0.3.10 - Relax the minimum supported Rust version to 1.60. (#1056) - Implement `UnwindSafe` and `RefUnwindSafe` for `ArrayQueue` and `SegQueue`. (#1053) - Optimize `Drop` implementation of `ArrayQueue`. (#1057) # Version 0.3.9 - Bump the minimum supported Rust version to 1.61. (#1037) - Improve support for targets without atomic CAS. (#1037) - Remove build script. (#1037) # Version 0.3.8 - Fix build script bug introduced in 0.3.7. (#932) # Version 0.3.7 **Note:** This release has been yanked due to regression fixed in 0.3.8. - Improve support for custom targets. (#922) # Version 0.3.6 - Bump the minimum supported Rust version to 1.38. (#877) # Version 0.3.5 - Add `ArrayQueue::force_push`. (#789) # Version 0.3.4 - Implement `IntoIterator` for `ArrayQueue` and `SegQueue`. (#772) # Version 0.3.3 - Fix stacked borrows violation in `ArrayQueue` when `-Zmiri-tag-raw-pointers` is enabled. (#763) # Version 0.3.2 - Support targets that do not have atomic CAS on stable Rust. (#698) # Version 0.3.1 - Make `SegQueue::new` const fn. (#584) - Change license to "MIT OR Apache-2.0". # Version 0.3.0 - Bump the minimum supported Rust version to 1.36. - Remove `PushError` and `PopError`. # Version 0.2.3 - Fix bug in release (yanking 0.2.2) # Version 0.2.2 - Fix unsoundness issues by adopting `MaybeUninit`. (#458) # Version 0.2.1 - Add `no_std` support. # Version 0.2.0 - Bump the minimum required version to 1.28. - Bump `crossbeam-utils` to `0.7`. # Version 0.1.2 - Update `crossbeam-utils` to `0.6.5`. # Version 0.1.1 - Update `crossbeam-utils` to `0.6.4`. # Version 0.1.0 - Initial version with `ArrayQueue` and `SegQueue`. crossbeam-queue-0.3.11/Cargo.toml0000644000000022510000000000100122140ustar # 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 = "2021" rust-version = "1.60" name = "crossbeam-queue" version = "0.3.11" description = "Concurrent queues" homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-queue" readme = "README.md" keywords = [ "queue", "mpmc", "lock-free", "producer", "consumer", ] categories = [ "concurrency", "data-structures", "no-std", ] license = "MIT OR Apache-2.0" repository = "https://github.com/crossbeam-rs/crossbeam" [dependencies.crossbeam-utils] version = "0.8.18" default-features = false [dev-dependencies.rand] version = "0.8" [features] alloc = [] default = ["std"] nightly = ["crossbeam-utils/nightly"] std = [ "alloc", "crossbeam-utils/std", ] crossbeam-queue-0.3.11/Cargo.toml.orig000064400000000000000000000026171046102023000157030ustar 00000000000000[package] name = "crossbeam-queue" # When publishing a new version: # - Update CHANGELOG.md # - Update README.md # - Create "crossbeam-queue-X.Y.Z" git tag version = "0.3.11" edition = "2021" rust-version = "1.60" license = "MIT OR Apache-2.0" repository = "https://github.com/crossbeam-rs/crossbeam" homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/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] crossbeam-utils = { version = "0.8.18", path = "../crossbeam-utils", default-features = false } [dev-dependencies] rand = "0.8" crossbeam-queue-0.3.11/LICENSE-APACHE000064400000000000000000000251371046102023000147420ustar 00000000000000 Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. 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See the License for the specific language governing permissions and limitations under the License. crossbeam-queue-0.3.11/LICENSE-MIT000064400000000000000000000021131046102023000144370ustar 00000000000000The 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. 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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. crossbeam-queue-0.3.11/README.md000064400000000000000000000041011046102023000142610ustar 00000000000000# Crossbeam Queue [![Build Status](https://github.com/crossbeam-rs/crossbeam/workflows/CI/badge.svg)]( https://github.com/crossbeam-rs/crossbeam/actions) [![License](https://img.shields.io/badge/license-MIT_OR_Apache--2.0-blue.svg)]( https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-queue#license) [![Cargo](https://img.shields.io/crates/v/crossbeam-queue.svg)]( https://crates.io/crates/crossbeam-queue) [![Documentation](https://docs.rs/crossbeam-queue/badge.svg)]( https://docs.rs/crossbeam-queue) [![Rust 1.60+](https://img.shields.io/badge/rust-1.60+-lightgray.svg)]( https://www.rust-lang.org) [![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ) This crate provides concurrent queues that can be shared among threads: * [`ArrayQueue`], a bounded MPMC queue that allocates a fixed-capacity buffer on construction. * [`SegQueue`], an unbounded MPMC queue that allocates small buffers, segments, on demand. Everything in this crate can be used in `no_std` environments, provided that `alloc` feature is enabled. [`ArrayQueue`]: https://docs.rs/crossbeam-queue/*/crossbeam_queue/struct.ArrayQueue.html [`SegQueue`]: https://docs.rs/crossbeam-queue/*/crossbeam_queue/struct.SegQueue.html ## Usage Add this to your `Cargo.toml`: ```toml [dependencies] crossbeam-queue = "0.3" ``` ## Compatibility Crossbeam Queue supports stable Rust releases going back at least six months, and every time the minimum supported Rust version is increased, a new minor version is released. Currently, the minimum supported Rust version is 1.60. ## 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. crossbeam-queue-0.3.11/src/array_queue.rs000064400000000000000000000415731046102023000164770ustar 00000000000000//! The implementation is based on Dmitry Vyukov's bounded MPMC queue. //! //! Source: //! - use alloc::boxed::Box; use core::cell::UnsafeCell; use core::fmt; use core::mem::{self, MaybeUninit}; use core::panic::{RefUnwindSafe, UnwindSafe}; use core::sync::atomic::{self, AtomicUsize, Ordering}; use crossbeam_utils::{Backoff, CachePadded}; /// A slot in a queue. struct Slot { /// 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>, } /// A bounded multi-producer multi-consumer queue. /// /// This queue allocates a fixed-capacity buffer on construction, which is used to store pushed /// elements. The queue cannot hold more elements than the buffer allows. Attempting to push an /// element into a full queue will fail. Alternatively, [`force_push`] makes it possible for /// this queue to be used as a ring-buffer. Having a buffer allocated upfront makes this queue /// a bit faster than [`SegQueue`]. /// /// [`force_push`]: ArrayQueue::force_push /// [`SegQueue`]: super::SegQueue /// /// # Examples /// /// ``` /// use crossbeam_queue::ArrayQueue; /// /// let q = ArrayQueue::new(2); /// /// assert_eq!(q.push('a'), Ok(())); /// assert_eq!(q.push('b'), Ok(())); /// assert_eq!(q.push('c'), Err('c')); /// assert_eq!(q.pop(), Some('a')); /// ``` pub struct ArrayQueue { /// 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, /// 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, /// The buffer holding slots. buffer: Box<[Slot]>, /// The queue capacity. cap: usize, /// A stamp with the value of `{ lap: 1, index: 0 }`. one_lap: usize, } unsafe impl Sync for ArrayQueue {} unsafe impl Send for ArrayQueue {} impl UnwindSafe for ArrayQueue {} impl RefUnwindSafe for ArrayQueue {} impl ArrayQueue { /// Creates a new bounded queue with the given capacity. /// /// # Panics /// /// Panics if the capacity is zero. /// /// # Examples /// /// ``` /// use crossbeam_queue::ArrayQueue; /// /// let q = ArrayQueue::::new(100); /// ``` pub fn new(cap: usize) -> ArrayQueue { assert!(cap > 0, "capacity must be non-zero"); // Head is initialized to `{ lap: 0, index: 0 }`. // Tail is initialized to `{ lap: 0, index: 0 }`. let head = 0; let tail = 0; // Allocate a buffer of `cap` slots initialized // with stamps. let buffer: Box<[Slot]> = (0..cap) .map(|i| { // Set the stamp to `{ lap: 0, index: i }`. Slot { stamp: AtomicUsize::new(i), value: UnsafeCell::new(MaybeUninit::uninit()), } }) .collect(); // One lap is the smallest power of two greater than `cap`. let one_lap = (cap + 1).next_power_of_two(); ArrayQueue { buffer, cap, one_lap, head: CachePadded::new(AtomicUsize::new(head)), tail: CachePadded::new(AtomicUsize::new(tail)), } } fn push_or_else(&self, mut value: T, f: F) -> Result<(), T> where F: Fn(T, usize, usize, &Slot) -> Result, { let backoff = Backoff::new(); let mut tail = self.tail.load(Ordering::Relaxed); loop { // Deconstruct the tail. let index = tail & (self.one_lap - 1); let lap = tail & !(self.one_lap - 1); let new_tail = if index + 1 < self.cap { // Same lap, incremented index. // Set to `{ lap: lap, index: index + 1 }`. tail + 1 } else { // One lap forward, index wraps around to zero. // Set to `{ lap: lap.wrapping_add(1), index: 0 }`. lap.wrapping_add(self.one_lap) }; // Inspect the corresponding slot. debug_assert!(index < self.buffer.len()); let slot = unsafe { self.buffer.get_unchecked(index) }; let stamp = slot.stamp.load(Ordering::Acquire); // If the tail and the stamp match, we may attempt to push. if tail == stamp { // Try moving the tail. match self.tail.compare_exchange_weak( tail, new_tail, Ordering::SeqCst, Ordering::Relaxed, ) { Ok(_) => { // Write the value into the slot and update the stamp. unsafe { slot.value.get().write(MaybeUninit::new(value)); } slot.stamp.store(tail + 1, Ordering::Release); return Ok(()); } Err(t) => { tail = t; backoff.spin(); } } } else if stamp.wrapping_add(self.one_lap) == tail + 1 { atomic::fence(Ordering::SeqCst); value = f(value, tail, new_tail, slot)?; backoff.spin(); tail = self.tail.load(Ordering::Relaxed); } else { // Snooze because we need to wait for the stamp to get updated. backoff.snooze(); tail = self.tail.load(Ordering::Relaxed); } } } /// Attempts to push an element into the queue. /// /// If the queue is full, the element is returned back as an error. /// /// # Examples /// /// ``` /// use crossbeam_queue::ArrayQueue; /// /// let q = ArrayQueue::new(1); /// /// assert_eq!(q.push(10), Ok(())); /// assert_eq!(q.push(20), Err(20)); /// ``` pub fn push(&self, value: T) -> Result<(), T> { self.push_or_else(value, |v, tail, _, _| { let head = self.head.load(Ordering::Relaxed); // If the head lags one lap behind the tail as well... if head.wrapping_add(self.one_lap) == tail { // ...then the queue is full. Err(v) } else { Ok(v) } }) } /// Pushes an element into the queue, replacing the oldest element if necessary. /// /// If the queue is full, the oldest element is replaced and returned, /// otherwise `None` is returned. /// /// # Examples /// /// ``` /// use crossbeam_queue::ArrayQueue; /// /// let q = ArrayQueue::new(2); /// /// assert_eq!(q.force_push(10), None); /// assert_eq!(q.force_push(20), None); /// assert_eq!(q.force_push(30), Some(10)); /// assert_eq!(q.pop(), Some(20)); /// ``` pub fn force_push(&self, value: T) -> Option { self.push_or_else(value, |v, tail, new_tail, slot| { let head = tail.wrapping_sub(self.one_lap); let new_head = new_tail.wrapping_sub(self.one_lap); // Try moving the head. if self .head .compare_exchange_weak(head, new_head, Ordering::SeqCst, Ordering::Relaxed) .is_ok() { // Move the tail. self.tail.store(new_tail, Ordering::SeqCst); // Swap the previous value. let old = unsafe { slot.value.get().replace(MaybeUninit::new(v)).assume_init() }; // Update the stamp. slot.stamp.store(tail + 1, Ordering::Release); Err(old) } else { Ok(v) } }) .err() } /// Attempts to pop an element from the queue. /// /// If the queue is empty, `None` is returned. /// /// # Examples /// /// ``` /// use crossbeam_queue::ArrayQueue; /// /// let q = ArrayQueue::new(1); /// assert_eq!(q.push(10), Ok(())); /// /// assert_eq!(q.pop(), Some(10)); /// assert!(q.pop().is_none()); /// ``` pub fn pop(&self) -> Option { let backoff = Backoff::new(); let mut head = self.head.load(Ordering::Relaxed); loop { // Deconstruct the head. let index = head & (self.one_lap - 1); let lap = head & !(self.one_lap - 1); // Inspect the corresponding slot. debug_assert!(index < self.buffer.len()); let slot = unsafe { self.buffer.get_unchecked(index) }; let stamp = slot.stamp.load(Ordering::Acquire); // If the the stamp is ahead of the head by 1, we may attempt to pop. if head + 1 == stamp { let new = if index + 1 < self.cap { // Same lap, incremented index. // Set to `{ lap: lap, index: index + 1 }`. head + 1 } else { // One lap forward, index wraps around to zero. // Set to `{ lap: lap.wrapping_add(1), index: 0 }`. lap.wrapping_add(self.one_lap) }; // Try moving the head. match self.head.compare_exchange_weak( head, new, Ordering::SeqCst, Ordering::Relaxed, ) { Ok(_) => { // Read the value from the slot and update the stamp. let msg = unsafe { slot.value.get().read().assume_init() }; slot.stamp .store(head.wrapping_add(self.one_lap), Ordering::Release); return Some(msg); } Err(h) => { head = h; backoff.spin(); } } } else if stamp == head { atomic::fence(Ordering::SeqCst); let tail = self.tail.load(Ordering::Relaxed); // If the tail equals the head, that means the channel is empty. if tail == head { return None; } backoff.spin(); head = self.head.load(Ordering::Relaxed); } else { // Snooze because we need to wait for the stamp to get updated. backoff.snooze(); head = self.head.load(Ordering::Relaxed); } } } /// Returns the capacity of the queue. /// /// # Examples /// /// ``` /// use crossbeam_queue::ArrayQueue; /// /// let q = ArrayQueue::::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 Drop for ArrayQueue { fn drop(&mut self) { if mem::needs_drop::() { // Get the index of the head. let head = *self.head.get_mut(); let tail = *self.tail.get_mut(); let hix = head & (self.one_lap - 1); let tix = tail & (self.one_lap - 1); let len = if hix < tix { tix - hix } else if hix > tix { self.cap - hix + tix } else if tail == head { 0 } else { self.cap }; // Loop over all slots that hold a message and drop them. for i in 0..len { // Compute the index of the next slot holding a message. let index = if hix + i < self.cap { hix + i } else { hix + i - self.cap }; unsafe { debug_assert!(index < self.buffer.len()); let slot = self.buffer.get_unchecked_mut(index); (*slot.value.get()).assume_init_drop(); } } } } } impl fmt::Debug for ArrayQueue { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad("ArrayQueue { .. }") } } impl IntoIterator for ArrayQueue { type Item = T; type IntoIter = IntoIter; fn into_iter(self) -> Self::IntoIter { IntoIter { value: self } } } #[derive(Debug)] pub struct IntoIter { value: ArrayQueue, } impl Iterator for IntoIter { type Item = T; fn next(&mut self) -> Option { let value = &mut self.value; let head = *value.head.get_mut(); if value.head.get_mut() != value.tail.get_mut() { let index = head & (value.one_lap - 1); let lap = head & !(value.one_lap - 1); // SAFETY: We have mutable access to this, so we can read without // worrying about concurrency. Furthermore, we know this is // initialized because it is the value pointed at by `value.head` // and this is a non-empty queue. let val = unsafe { debug_assert!(index < value.buffer.len()); let slot = value.buffer.get_unchecked_mut(index); slot.value.get().read().assume_init() }; let new = if index + 1 < value.cap { // Same lap, incremented index. // Set to `{ lap: lap, index: index + 1 }`. head + 1 } else { // One lap forward, index wraps around to zero. // Set to `{ lap: lap.wrapping_add(1), index: 0 }`. lap.wrapping_add(value.one_lap) }; *value.head.get_mut() = new; Option::Some(val) } else { Option::None } } } crossbeam-queue-0.3.11/src/lib.rs000064400000000000000000000017011046102023000147100ustar 00000000000000//! 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(all(feature = "alloc", target_has_atomic = "ptr"))] extern crate alloc; #[cfg(all(feature = "alloc", target_has_atomic = "ptr"))] mod array_queue; #[cfg(all(feature = "alloc", target_has_atomic = "ptr"))] mod seg_queue; #[cfg(all(feature = "alloc", target_has_atomic = "ptr"))] pub use crate::{array_queue::ArrayQueue, seg_queue::SegQueue}; crossbeam-queue-0.3.11/src/seg_queue.rs000064400000000000000000000433521046102023000161340ustar 00000000000000use alloc::boxed::Box; use core::cell::UnsafeCell; use core::fmt; use core::marker::PhantomData; use core::mem::MaybeUninit; use core::panic::{RefUnwindSafe, UnwindSafe}; 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 { /// The value. value: UnsafeCell>, /// The state of the slot. state: AtomicUsize, } impl Slot { const UNINIT: Self = Self { value: UnsafeCell::new(MaybeUninit::uninit()), state: AtomicUsize::new(0), }; /// Waits until a value is written into the slot. fn wait_write(&self) { let backoff = Backoff::new(); while self.state.load(Ordering::Acquire) & WRITE == 0 { backoff.snooze(); } } } /// A block in a linked list. /// /// Each block in the list can hold up to `BLOCK_CAP` values. struct Block { /// The next block in the linked list. next: AtomicPtr>, /// Slots for values. slots: [Slot; BLOCK_CAP], } impl Block { /// Creates an empty block that starts at `start_index`. fn new() -> Block { Self { next: AtomicPtr::new(ptr::null_mut()), slots: [Slot::UNINIT; BLOCK_CAP], } } /// Waits until the next pointer is set. fn wait_next(&self) -> *mut Block { 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, 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 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 { /// The head of the queue. head: CachePadded>, /// The tail of the queue. tail: CachePadded>, /// Indicates that dropping a `SegQueue` may drop values of type `T`. _marker: PhantomData, } unsafe impl Send for SegQueue {} unsafe impl Sync for SegQueue {} impl UnwindSafe for SegQueue {} impl RefUnwindSafe for SegQueue {} impl SegQueue { /// Creates a new unbounded queue. /// /// # Examples /// /// ``` /// use crossbeam_queue::SegQueue; /// /// let q = SegQueue::::new(); /// ``` pub const fn new() -> SegQueue { 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::::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::::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 { 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 Drop for SegQueue { fn drop(&mut self) { let mut head = *self.head.index.get_mut(); let mut tail = *self.tail.index.get_mut(); let mut block = *self.head.block.get_mut(); // Erase the lower bits. head &= !((1 << SHIFT) - 1); tail &= !((1 << SHIFT) - 1); unsafe { // Drop all values between `head` and `tail` and deallocate the heap-allocated blocks. while head != tail { let offset = (head >> SHIFT) % LAP; if offset < BLOCK_CAP { // Drop the value in the slot. let slot = (*block).slots.get_unchecked(offset); (*slot.value.get()).assume_init_drop(); } else { // Deallocate the block and move to the next one. let next = *(*block).next.get_mut(); drop(Box::from_raw(block)); block = next; } head = head.wrapping_add(1 << SHIFT); } // Deallocate the last remaining block. if !block.is_null() { drop(Box::from_raw(block)); } } } } impl fmt::Debug for SegQueue { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad("SegQueue { .. }") } } impl Default for SegQueue { fn default() -> SegQueue { SegQueue::new() } } impl IntoIterator for SegQueue { type Item = T; type IntoIter = IntoIter; fn into_iter(self) -> Self::IntoIter { IntoIter { value: self } } } #[derive(Debug)] pub struct IntoIter { value: SegQueue, } impl Iterator for IntoIter { type Item = T; fn next(&mut self) -> Option { let value = &mut self.value; let head = *value.head.index.get_mut(); let tail = *value.tail.index.get_mut(); if head >> SHIFT == tail >> SHIFT { None } else { let block = *value.head.block.get_mut(); let offset = (head >> SHIFT) % LAP; // SAFETY: We have mutable access to this, so we can read without // worrying about concurrency. Furthermore, we know this is // initialized because it is the value pointed at by `value.head` // and this is a non-empty queue. let item = unsafe { let slot = (*block).slots.get_unchecked(offset); slot.value.get().read().assume_init() }; if offset + 1 == BLOCK_CAP { // Deallocate the block and move to the next one. // SAFETY: The block is initialized because we've been reading // from it this entire time. We can drop it b/c everything has // been read out of it, so nothing is pointing to it anymore. unsafe { let next = *(*block).next.get_mut(); drop(Box::from_raw(block)); *value.head.block.get_mut() = next; } // The last value in a block is empty, so skip it *value.head.index.get_mut() = head.wrapping_add(2 << SHIFT); // Double-check that we're pointing to the first item in a block. debug_assert_eq!((*value.head.index.get_mut() >> SHIFT) % LAP, 0); } else { *value.head.index.get_mut() = head.wrapping_add(1 << SHIFT); } Some(item) } } } crossbeam-queue-0.3.11/tests/array_queue.rs000064400000000000000000000204211046102023000170370ustar 00000000000000use 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::::new(i); assert_eq!(q.capacity(), i); } } #[test] #[should_panic(expected = "capacity must be non-zero")] fn zero_capacity() { let _ = ArrayQueue::::new(0); } #[test] fn len_empty_full() { let q = ArrayQueue::new(2); assert_eq!(q.len(), 0); assert!(q.is_empty()); assert!(!q.is_full()); q.push(()).unwrap(); assert_eq!(q.len(), 1); assert!(!q.is_empty()); assert!(!q.is_full()); q.push(()).unwrap(); assert_eq!(q.len(), 2); assert!(!q.is_empty()); assert!(q.is_full()); q.pop().unwrap(); assert_eq!(q.len(), 1); assert!(!q.is_empty()); assert!(!q.is_full()); } #[test] fn len() { #[cfg(miri)] const COUNT: usize = 30; #[cfg(not(miri))] const COUNT: usize = 25_000; #[cfg(miri)] const CAP: usize = 40; #[cfg(not(miri))] const CAP: usize = 1000; const ITERS: usize = CAP / 20; let q = ArrayQueue::new(CAP); assert_eq!(q.len(), 0); for _ in 0..CAP / 10 { for i in 0..ITERS { q.push(i).unwrap(); assert_eq!(q.len(), i + 1); } for i in 0..ITERS { q.pop().unwrap(); assert_eq!(q.len(), ITERS - i - 1); } } assert_eq!(q.len(), 0); for i in 0..CAP { q.push(i).unwrap(); assert_eq!(q.len(), i + 1); } for _ in 0..CAP { q.pop().unwrap(); } assert_eq!(q.len(), 0); scope(|scope| { scope.spawn(|_| { for i in 0..COUNT { loop { if let Some(x) = q.pop() { assert_eq!(x, i); break; } } let len = q.len(); assert!(len <= CAP); } }); scope.spawn(|_| { for i in 0..COUNT { while q.push(i).is_err() {} let len = q.len(); assert!(len <= CAP); } }); }) .unwrap(); assert_eq!(q.len(), 0); } #[test] fn spsc() { #[cfg(miri)] const COUNT: usize = 50; #[cfg(not(miri))] const COUNT: usize = 100_000; let q = ArrayQueue::new(3); scope(|scope| { scope.spawn(|_| { for i in 0..COUNT { loop { if let Some(x) = q.pop() { assert_eq!(x, i); break; } } } assert!(q.pop().is_none()); }); scope.spawn(|_| { for i in 0..COUNT { while q.push(i).is_err() {} } }); }) .unwrap(); } #[test] fn spsc_ring_buffer() { #[cfg(miri)] const COUNT: usize = 50; #[cfg(not(miri))] const COUNT: usize = 100_000; let t = AtomicUsize::new(1); let q = ArrayQueue::::new(3); let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::>(); scope(|scope| { scope.spawn(|_| loop { match t.load(Ordering::SeqCst) { 0 if q.is_empty() => break, _ => { while let Some(n) = q.pop() { v[n].fetch_add(1, Ordering::SeqCst); } } } }); scope.spawn(|_| { for i in 0..COUNT { if let Some(n) = q.force_push(i) { v[n].fetch_add(1, Ordering::SeqCst); } } t.fetch_sub(1, Ordering::SeqCst); }); }) .unwrap(); for c in v { assert_eq!(c.load(Ordering::SeqCst), 1); } } #[test] fn mpmc() { #[cfg(miri)] const COUNT: usize = 50; #[cfg(not(miri))] const COUNT: usize = 25_000; const THREADS: usize = 4; let q = ArrayQueue::::new(3); let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::>(); scope(|scope| { for _ in 0..THREADS { scope.spawn(|_| { for _ in 0..COUNT { let n = loop { if let Some(x) = q.pop() { break x; } }; v[n].fetch_add(1, Ordering::SeqCst); } }); } for _ in 0..THREADS { scope.spawn(|_| { for i in 0..COUNT { while q.push(i).is_err() {} } }); } }) .unwrap(); for c in v { assert_eq!(c.load(Ordering::SeqCst), THREADS); } } #[test] fn mpmc_ring_buffer() { #[cfg(miri)] const COUNT: usize = 50; #[cfg(not(miri))] const COUNT: usize = 25_000; const THREADS: usize = 4; let t = AtomicUsize::new(THREADS); let q = ArrayQueue::::new(3); let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::>(); scope(|scope| { for _ in 0..THREADS { scope.spawn(|_| loop { match t.load(Ordering::SeqCst) { 0 if q.is_empty() => break, _ => { while let Some(n) = q.pop() { v[n].fetch_add(1, Ordering::SeqCst); } } } }); } for _ in 0..THREADS { scope.spawn(|_| { for i in 0..COUNT { if let Some(n) = q.force_push(i) { v[n].fetch_add(1, Ordering::SeqCst); } } t.fetch_sub(1, Ordering::SeqCst); }); } }) .unwrap(); for c in v { assert_eq!(c.load(Ordering::SeqCst), THREADS); } } #[test] fn drops() { let runs: usize = if cfg!(miri) { 3 } else { 100 }; let steps: usize = if cfg!(miri) { 50 } else { 10_000 }; let additional: usize = if cfg!(miri) { 10 } else { 50 }; static DROPS: AtomicUsize = AtomicUsize::new(0); #[derive(Debug, PartialEq)] struct DropCounter; impl Drop for DropCounter { fn drop(&mut self) { DROPS.fetch_add(1, Ordering::SeqCst); } } let mut rng = thread_rng(); for _ in 0..runs { let steps = rng.gen_range(0..steps); let additional = rng.gen_range(0..additional); DROPS.store(0, Ordering::SeqCst); let q = ArrayQueue::new(50); scope(|scope| { scope.spawn(|_| { for _ in 0..steps { while q.pop().is_none() {} } }); scope.spawn(|_| { for _ in 0..steps { while q.push(DropCounter).is_err() { DROPS.fetch_sub(1, Ordering::SeqCst); } } }); }) .unwrap(); for _ in 0..additional { q.push(DropCounter).unwrap(); } assert_eq!(DROPS.load(Ordering::SeqCst), steps); drop(q); assert_eq!(DROPS.load(Ordering::SeqCst), steps + additional); } } #[test] fn linearizable() { #[cfg(miri)] const COUNT: usize = 100; #[cfg(not(miri))] const COUNT: usize = 25_000; const THREADS: usize = 4; let q = ArrayQueue::new(THREADS); scope(|scope| { for _ in 0..THREADS / 2 { scope.spawn(|_| { for _ in 0..COUNT { while q.push(0).is_err() {} q.pop().unwrap(); } }); scope.spawn(|_| { for _ in 0..COUNT { if q.force_push(0).is_none() { q.pop().unwrap(); } } }); } }) .unwrap(); } #[test] fn into_iter() { let q = ArrayQueue::new(100); for i in 0..100 { q.push(i).unwrap(); } for (i, j) in q.into_iter().enumerate() { assert_eq!(i, j); } } crossbeam-queue-0.3.11/tests/seg_queue.rs000064400000000000000000000077351046102023000165140ustar 00000000000000use std::sync::atomic::{AtomicUsize, Ordering}; use crossbeam_queue::SegQueue; use crossbeam_utils::thread::scope; use rand::{thread_rng, Rng}; #[test] fn smoke() { let q = SegQueue::new(); q.push(7); assert_eq!(q.pop(), Some(7)); q.push(8); assert_eq!(q.pop(), Some(8)); assert!(q.pop().is_none()); } #[test] fn len_empty_full() { let q = SegQueue::new(); assert_eq!(q.len(), 0); assert!(q.is_empty()); q.push(()); assert_eq!(q.len(), 1); assert!(!q.is_empty()); q.pop().unwrap(); assert_eq!(q.len(), 0); assert!(q.is_empty()); } #[test] fn len() { let q = SegQueue::new(); assert_eq!(q.len(), 0); for i in 0..50 { q.push(i); assert_eq!(q.len(), i + 1); } for i in 0..50 { q.pop().unwrap(); assert_eq!(q.len(), 50 - i - 1); } assert_eq!(q.len(), 0); } #[test] fn spsc() { #[cfg(miri)] const COUNT: usize = 100; #[cfg(not(miri))] const COUNT: usize = 100_000; let q = SegQueue::new(); scope(|scope| { scope.spawn(|_| { for i in 0..COUNT { loop { if let Some(x) = q.pop() { assert_eq!(x, i); break; } } } assert!(q.pop().is_none()); }); scope.spawn(|_| { for i in 0..COUNT { q.push(i); } }); }) .unwrap(); } #[test] fn mpmc() { #[cfg(miri)] const COUNT: usize = 50; #[cfg(not(miri))] const COUNT: usize = 25_000; const THREADS: usize = 4; let q = SegQueue::::new(); let v = (0..COUNT).map(|_| AtomicUsize::new(0)).collect::>(); scope(|scope| { for _ in 0..THREADS { scope.spawn(|_| { for _ in 0..COUNT { let n = loop { if let Some(x) = q.pop() { break x; } }; v[n].fetch_add(1, Ordering::SeqCst); } }); } for _ in 0..THREADS { scope.spawn(|_| { for i in 0..COUNT { q.push(i); } }); } }) .unwrap(); for c in v { assert_eq!(c.load(Ordering::SeqCst), THREADS); } } #[test] fn drops() { let runs: usize = if cfg!(miri) { 5 } else { 100 }; let steps: usize = if cfg!(miri) { 50 } else { 10_000 }; let additional: usize = if cfg!(miri) { 100 } else { 1_000 }; static DROPS: AtomicUsize = AtomicUsize::new(0); #[derive(Debug, PartialEq)] struct DropCounter; impl Drop for DropCounter { fn drop(&mut self) { DROPS.fetch_add(1, Ordering::SeqCst); } } let mut rng = thread_rng(); for _ in 0..runs { let steps = rng.gen_range(0..steps); let additional = rng.gen_range(0..additional); DROPS.store(0, Ordering::SeqCst); let q = SegQueue::new(); scope(|scope| { scope.spawn(|_| { for _ in 0..steps { while q.pop().is_none() {} } }); scope.spawn(|_| { for _ in 0..steps { q.push(DropCounter); } }); }) .unwrap(); for _ in 0..additional { q.push(DropCounter); } assert_eq!(DROPS.load(Ordering::SeqCst), steps); drop(q); assert_eq!(DROPS.load(Ordering::SeqCst), steps + additional); } } #[test] fn into_iter() { let q = SegQueue::new(); for i in 0..100 { q.push(i); } for (i, j) in q.into_iter().enumerate() { assert_eq!(i, j); } } #[test] fn into_iter_drop() { let q = SegQueue::new(); for i in 0..100 { q.push(i); } for (i, j) in q.into_iter().enumerate().take(50) { assert_eq!(i, j); } }