crossbeam-queue-0.2.1/CHANGELOG.md010064400017500001750000000005031360045670000146430ustar0000000000000000# 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-0.2.1/Cargo.toml.orig010064400017500001750000000015651360045664300157400ustar0000000000000000[package] name = "crossbeam-queue" # When publishing a new version: # - Update CHANGELOG.md # - Update README.md # - Create "crossbeam-queue-X.Y.Z" git tag version = "0.2.1" authors = ["The Crossbeam Project Developers"] license = "MIT/Apache-2.0 AND BSD-2-Clause" readme = "README.md" repository = "https://github.com/crossbeam-rs/crossbeam" homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-utils" documentation = "https://docs.rs/crossbeam-queue" description = "Concurrent queues" keywords = ["queue", "mpmc", "lock-free", "producer", "consumer"] categories = ["concurrency", "data-structures"] [features] default = ["std"] std = ["crossbeam-utils/std"] alloc = ["crossbeam-utils/alloc"] [dependencies] cfg-if = "0.1.2" [dependencies.crossbeam-utils] version = "0.7" path = "../crossbeam-utils" default-features = false [dev-dependencies] rand = "0.6" crossbeam-queue-0.2.1/Cargo.toml0000644000000023731360045727200122430ustar00# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO # # When uploading crates to the registry Cargo will automatically # "normalize" Cargo.toml files for maximal compatibility # with all versions of Cargo and also rewrite `path` dependencies # to registry (e.g., crates.io) dependencies # # If you believe there's an error in this file please file an # issue against the rust-lang/cargo repository. 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See the License for the specific language governing permissions and limitations under the License. crossbeam-queue-0.2.1/LICENSE-MIT010066400017500001750000000021131353377241300144760ustar0000000000000000The 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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Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. The views and conclusions contained in the software and documentation are those of the authors and should not be interpreted as representing official policies, either expressed or implied, of Dmitry Vyukov. crossbeam-queue-0.2.1/README.md010064400017500001750000000045701356065477100143360ustar0000000000000000# Crossbeam Queue [![Build Status](https://travis-ci.org/crossbeam-rs/crossbeam.svg?branch=master)]( https://travis-ci.org/crossbeam-rs/crossbeam) [![License](https://img.shields.io/badge/license-MIT%2FApache--2.0-blue.svg)]( https://github.com/crossbeam-rs/crossbeam-queue/tree/master/src) [![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 1.28+](https://img.shields.io/badge/rust-1.28+-lightgray.svg)]( https://www.rust-lang.org) [![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.gg/BBYwKq) 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. [`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 = "0.2" ``` Next, add this to your crate: ```rust extern crate crossbeam_queue; ``` ## Compatibility The minimum supported Rust version is 1.28. Any change to this is considered a breaking change. ## 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. #### Third party software This product includes copies and modifications of software developed by third parties: * [src/array_queue.rs](src/array_queue.rs) is based on [Bounded MPMC queue](http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue) by Dmitry Vyukov, licensed under the Simplified BSD License and the Apache License, Version 2.0. See the source code files for more details. Copies of third party licenses can be found in [LICENSE-THIRD-PARTY](LICENSE-THIRD-PARTY). crossbeam-queue-0.2.1/src/array_queue.rs010064400017500001750000000327021360045663000165210ustar0000000000000000//! The implementation is based on Dmitry Vyukov's bounded MPMC queue. //! //! Source: //! - http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue //! //! Copyright & License: //! - Copyright (c) 2010-2011 Dmitry Vyukov //! - Simplified BSD License and Apache License, Version 2.0 //! - http://www.1024cores.net/home/code-license use alloc::vec::Vec; use core::cell::UnsafeCell; use core::fmt; use core::marker::PhantomData; use core::mem; use core::ptr; use core::sync::atomic::{self, AtomicUsize, Ordering}; use crossbeam_utils::{Backoff, CachePadded}; use err::{PopError, PushError}; /// 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. Having a buffer allocated upfront makes this queue a bit /// faster than [`SegQueue`]. /// /// [`SegQueue`]: struct.SegQueue.html /// /// # Examples /// /// ``` /// use crossbeam_queue::{ArrayQueue, PushError}; /// /// let q = ArrayQueue::new(2); /// /// assert_eq!(q.push('a'), Ok(())); /// assert_eq!(q.push('b'), Ok(())); /// assert_eq!(q.push('c'), Err(PushError('c'))); /// assert_eq!(q.pop(), Ok('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: *mut Slot, /// The queue capacity. cap: usize, /// A stamp with the value of `{ lap: 1, index: 0 }`. one_lap: usize, /// Indicates that dropping an `ArrayQueue` may drop elements of type `T`. _marker: PhantomData, } unsafe impl Sync for ArrayQueue {} unsafe impl Send 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. let buffer = { let mut v = Vec::>::with_capacity(cap); let ptr = v.as_mut_ptr(); mem::forget(v); ptr }; // Initialize stamps in the slots. for i in 0..cap { unsafe { // Set the stamp to `{ lap: 0, index: i }`. let slot = buffer.add(i); ptr::write(&mut (*slot).stamp, AtomicUsize::new(i)); } } // One lap is the smallest power of two greater than `cap`. let one_lap = (cap + 1).next_power_of_two(); ArrayQueue { buffer, cap, one_lap, head: CachePadded::new(AtomicUsize::new(head)), tail: CachePadded::new(AtomicUsize::new(tail)), _marker: PhantomData, } } /// Attempts to push an element into the queue. /// /// If the queue is full, the element is returned back as an error. /// /// # Examples /// /// ``` /// use crossbeam_queue::{ArrayQueue, PushError}; /// /// let q = ArrayQueue::new(1); /// /// assert_eq!(q.push(10), Ok(())); /// assert_eq!(q.push(20), Err(PushError(20))); /// ``` pub fn push(&self, value: T) -> Result<(), PushError> { let backoff = Backoff::new(); let mut tail = self.tail.load(Ordering::Relaxed); loop { // Deconstruct the tail. let index = tail & (self.one_lap - 1); let lap = tail & !(self.one_lap - 1); // Inspect the corresponding slot. let slot = unsafe { &*self.buffer.add(index) }; let stamp = slot.stamp.load(Ordering::Acquire); // If the tail and the stamp match, we may attempt to push. if tail == stamp { let new_tail = if index + 1 < self.cap { // Same lap, incremented index. // Set to `{ lap: lap, index: index + 1 }`. tail + 1 } else { // One lap forward, index wraps around to zero. // Set to `{ lap: lap.wrapping_add(1), index: 0 }`. lap.wrapping_add(self.one_lap) }; // Try moving the tail. match self.tail.compare_exchange_weak( tail, new_tail, Ordering::SeqCst, Ordering::Relaxed, ) { Ok(_) => { // Write the value into the slot and update the stamp. unsafe { slot.value.get().write(value); } slot.stamp.store(tail + 1, Ordering::Release); return Ok(()); } Err(t) => { tail = t; backoff.spin(); } } } else if stamp.wrapping_add(self.one_lap) == tail + 1 { atomic::fence(Ordering::SeqCst); let head = self.head.load(Ordering::Relaxed); // If the head lags one lap behind the tail as well... if head.wrapping_add(self.one_lap) == tail { // ...then the queue is full. return Err(PushError(value)); } backoff.spin(); tail = self.tail.load(Ordering::Relaxed); } else { // Snooze because we need to wait for the stamp to get updated. backoff.snooze(); tail = self.tail.load(Ordering::Relaxed); } } } /// Attempts to pop an element from the queue. /// /// If the queue is empty, an error is returned. /// /// # Examples /// /// ``` /// use crossbeam_queue::{ArrayQueue, PopError}; /// /// let q = ArrayQueue::new(1); /// assert_eq!(q.push(10), Ok(())); /// /// assert_eq!(q.pop(), Ok(10)); /// assert_eq!(q.pop(), Err(PopError)); /// ``` pub fn pop(&self) -> Result { let backoff = Backoff::new(); let mut head = self.head.load(Ordering::Relaxed); loop { // Deconstruct the head. let index = head & (self.one_lap - 1); let lap = head & !(self.one_lap - 1); // Inspect the corresponding slot. let slot = unsafe { &*self.buffer.add(index) }; let stamp = slot.stamp.load(Ordering::Acquire); // If the the stamp is ahead of the head by 1, we may attempt to pop. if head + 1 == stamp { let new = if index + 1 < self.cap { // Same lap, incremented index. // Set to `{ lap: lap, index: index + 1 }`. head + 1 } else { // One lap forward, index wraps around to zero. // Set to `{ lap: lap.wrapping_add(1), index: 0 }`. lap.wrapping_add(self.one_lap) }; // Try moving the head. match self.head.compare_exchange_weak( head, new, Ordering::SeqCst, Ordering::Relaxed, ) { Ok(_) => { // Read the value from the slot and update the stamp. let msg = unsafe { slot.value.get().read() }; slot.stamp .store(head.wrapping_add(self.one_lap), Ordering::Release); return Ok(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 Err(PopError); } 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, PopError}; /// /// 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, PopError}; /// /// 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, PopError}; /// /// 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, PopError}; /// /// 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) { // Get the index of the head. let hix = self.head.load(Ordering::Relaxed) & (self.one_lap - 1); // Loop over all slots that hold a message and drop them. for i in 0..self.len() { // Compute the index of the next slot holding a message. let index = if hix + i < self.cap { hix + i } else { hix + i - self.cap }; unsafe { self.buffer.add(index).drop_in_place(); } } // Finally, deallocate the buffer, but don't run any destructors. unsafe { Vec::from_raw_parts(self.buffer, 0, self.cap); } } } impl fmt::Debug for ArrayQueue { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.pad("ArrayQueue { .. }") } } crossbeam-queue-0.2.1/src/err.rs010064400017500001750000000021401360045663000147600ustar0000000000000000use core::fmt; /// Error which occurs when popping from an empty queue. #[derive(Clone, Copy, Eq, PartialEq)] pub struct PopError; impl fmt::Debug for PopError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { "PopError".fmt(f) } } impl fmt::Display for PopError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { "popping from an empty queue".fmt(f) } } #[cfg(features = "std")] impl std::error::Error for PopError { fn description(&self) -> &str { "popping from an empty queue" } } /// Error which occurs when pushing into a full queue. #[derive(Clone, Copy, Eq, PartialEq)] pub struct PushError(pub T); impl fmt::Debug for PushError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { "PushError(..)".fmt(f) } } impl fmt::Display for PushError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { "pushing into a full queue".fmt(f) } } #[cfg(features = "std")] impl std::error::Error for PushError { fn description(&self) -> &str { "pushing into a full queue" } } crossbeam-queue-0.2.1/src/lib.rs010064400017500001750000000020221360045663000147350ustar0000000000000000//! 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. //! //! [`ArrayQueue`]: struct.ArrayQueue.html //! [`SegQueue`]: struct.SegQueue.html #![warn(missing_docs)] #![warn(missing_debug_implementations)] #![cfg_attr(not(feature = "std"), no_std)] #[macro_use] extern crate cfg_if; #[cfg(feature = "std")] extern crate core; cfg_if! { if #[cfg(feature = "alloc")] { extern crate alloc; } else if #[cfg(feature = "std")] { extern crate std as alloc; } } extern crate crossbeam_utils; cfg_if! { if #[cfg(any(feature = "alloc", feature = "std"))] { mod array_queue; mod err; mod seg_queue; pub use self::array_queue::ArrayQueue; pub use self::err::{PopError, PushError}; pub use self::seg_queue::SegQueue; } } crossbeam-queue-0.2.1/src/seg_queue.rs010064400017500001750000000366771360045663000162000ustar0000000000000000use alloc::boxed::Box; use core::cell::UnsafeCell; use core::fmt; use core::marker::PhantomData; use core::mem::{self, ManuallyDrop}; use core::ptr; use core::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering}; use crossbeam_utils::{Backoff, CachePadded}; use err::PopError; // 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 { /// 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 { unsafe { mem::zeroed() } } /// 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`]: struct.ArrayQueue.html /// /// # Examples /// /// ``` /// use crossbeam_queue::{PopError, SegQueue}; /// /// let q = SegQueue::new(); /// /// q.push('a'); /// q.push('b'); /// /// assert_eq!(q.pop(), Ok('a')); /// assert_eq!(q.pop(), Ok('b')); /// assert_eq!(q.pop(), Err(PopError)); /// ``` 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 SegQueue { /// Creates a new unbounded queue. /// /// # Examples /// /// ``` /// use crossbeam_queue::SegQueue; /// /// let q = SegQueue::::new(); /// ``` pub 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_and_swap(block, new, Ordering::Release) == block { 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(ManuallyDrop::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, an error is returned. /// /// # Examples /// /// ``` /// use crossbeam_queue::{PopError, SegQueue}; /// /// let q = SegQueue::new(); /// /// q.push(10); /// assert_eq!(q.pop(), Ok(10)); /// assert_eq!(q.pop(), Err(PopError)); /// ``` pub fn pop(&self) -> Result { 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 Err(PopError); } // 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 m = slot.value.get().read(); let value = ManuallyDrop::into_inner(m); // 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); 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, PopError}; /// /// 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); // 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; // Fix up indices if they fall onto block ends. if head == BLOCK_CAP { head = 0; tail -= LAP; } if tail == BLOCK_CAP { tail += 1; } // 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.load(Ordering::Relaxed); let mut tail = self.tail.index.load(Ordering::Relaxed); let mut block = self.head.block.load(Ordering::Relaxed); // Erase the lower bits. head &= !((1 << SHIFT) - 1); tail &= !((1 << SHIFT) - 1); unsafe { // Drop all values between `head` and `tail` and deallocate the heap-allocated blocks. while head != tail { let offset = (head >> SHIFT) % LAP; if offset < BLOCK_CAP { // Drop the value in the slot. let slot = (*block).slots.get_unchecked(offset); ManuallyDrop::drop(&mut *(*slot).value.get()); } else { // Deallocate the block and move to the next one. let next = (*block).next.load(Ordering::Relaxed); drop(Box::from_raw(block)); block = next; } head = head.wrapping_add(1 << SHIFT); } // Deallocate the last remaining block. if !block.is_null() { drop(Box::from_raw(block)); } } } } impl 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() } } crossbeam-queue-0.2.1/tests/array_queue.rs010066400017500001750000000125671353377241300171120ustar0000000000000000extern crate crossbeam_queue; extern crate crossbeam_utils; extern crate rand; use std::sync::atomic::{AtomicUsize, Ordering}; use crossbeam_queue::ArrayQueue; use crossbeam_utils::thread::scope; use rand::{thread_rng, Rng}; #[test] fn smoke() { let q = ArrayQueue::new(1); q.push(7).unwrap(); assert_eq!(q.pop(), 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 = 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_eq!(q.is_empty(), true); assert_eq!(q.is_full(), false); q.push(()).unwrap(); assert_eq!(q.len(), 1); assert_eq!(q.is_empty(), false); assert_eq!(q.is_full(), false); q.push(()).unwrap(); assert_eq!(q.len(), 2); assert_eq!(q.is_empty(), false); assert_eq!(q.is_full(), true); q.pop().unwrap(); assert_eq!(q.len(), 1); assert_eq!(q.is_empty(), false); assert_eq!(q.is_full(), false); } #[test] fn len() { const COUNT: usize = 25_000; const CAP: usize = 1000; let q = ArrayQueue::new(CAP); assert_eq!(q.len(), 0); for _ in 0..CAP / 10 { for i in 0..50 { q.push(i).unwrap(); assert_eq!(q.len(), i + 1); } for i in 0..50 { q.pop().unwrap(); assert_eq!(q.len(), 50 - i - 1); } } assert_eq!(q.len(), 0); for i in 0..CAP { q.push(i).unwrap(); assert_eq!(q.len(), i + 1); } for _ in 0..CAP { q.pop().unwrap(); } assert_eq!(q.len(), 0); scope(|scope| { scope.spawn(|_| { for i in 0..COUNT { loop { if let Ok(x) = q.pop() { assert_eq!(x, i); break; } } let len = q.len(); assert!(len <= CAP); } }); scope.spawn(|_| { for i in 0..COUNT { while q.push(i).is_err() {} let len = q.len(); assert!(len <= CAP); } }); }) .unwrap(); assert_eq!(q.len(), 0); } #[test] fn spsc() { const COUNT: usize = 100_000; let q = ArrayQueue::new(3); scope(|scope| { scope.spawn(|_| { for i in 0..COUNT { loop { if let Ok(x) = q.pop() { assert_eq!(x, i); break; } } } assert!(q.pop().is_err()); }); scope.spawn(|_| { for i in 0..COUNT { while q.push(i).is_err() {} } }); }) .unwrap(); } #[test] fn mpmc() { const COUNT: usize = 25_000; const THREADS: usize = 4; let q = ArrayQueue::::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 Ok(x) = q.pop() { break x; } }; v[n].fetch_add(1, Ordering::SeqCst); } }); } for _ in 0..THREADS { scope.spawn(|_| { for i in 0..COUNT { while q.push(i).is_err() {} } }); } }) .unwrap(); for c in v { assert_eq!(c.load(Ordering::SeqCst), THREADS); } } #[test] fn drops() { const RUNS: usize = 100; static DROPS: AtomicUsize = AtomicUsize::new(0); #[derive(Debug, PartialEq)] struct DropCounter; impl Drop for DropCounter { fn drop(&mut self) { DROPS.fetch_add(1, Ordering::SeqCst); } } let mut rng = thread_rng(); for _ in 0..RUNS { let steps = rng.gen_range(0, 10_000); let additional = rng.gen_range(0, 50); DROPS.store(0, Ordering::SeqCst); let q = ArrayQueue::new(50); scope(|scope| { scope.spawn(|_| { for _ in 0..steps { while q.pop().is_err() {} } }); scope.spawn(|_| { for _ in 0..steps { while q.push(DropCounter).is_err() { DROPS.fetch_sub(1, Ordering::SeqCst); } } }); }) .unwrap(); for _ in 0..additional { q.push(DropCounter).unwrap(); } assert_eq!(DROPS.load(Ordering::SeqCst), steps); drop(q); assert_eq!(DROPS.load(Ordering::SeqCst), steps + additional); } } #[test] fn linearizable() { const COUNT: usize = 25_000; const THREADS: usize = 4; let q = ArrayQueue::new(THREADS); scope(|scope| { for _ in 0..THREADS { scope.spawn(|_| { for _ in 0..COUNT { while q.push(0).is_err() {} q.pop().unwrap(); } }); } }) .unwrap(); } crossbeam-queue-0.2.1/tests/seg_queue.rs010066400017500001750000000065741353377241300165530ustar0000000000000000extern crate crossbeam_queue; extern crate crossbeam_utils; extern crate rand; use std::sync::atomic::{AtomicUsize, Ordering}; use crossbeam_queue::SegQueue; use crossbeam_utils::thread::scope; use rand::{thread_rng, Rng}; #[test] fn smoke() { let q = SegQueue::new(); q.push(7); assert_eq!(q.pop(), Ok(7)); q.push(8); assert_eq!(q.pop(), Ok(8)); assert!(q.pop().is_err()); } #[test] fn len_empty_full() { let q = SegQueue::new(); assert_eq!(q.len(), 0); assert_eq!(q.is_empty(), true); q.push(()); assert_eq!(q.len(), 1); assert_eq!(q.is_empty(), false); q.pop().unwrap(); assert_eq!(q.len(), 0); assert_eq!(q.is_empty(), true); } #[test] fn len() { let q = SegQueue::new(); assert_eq!(q.len(), 0); for i in 0..50 { q.push(i); assert_eq!(q.len(), i + 1); } for i in 0..50 { q.pop().unwrap(); assert_eq!(q.len(), 50 - i - 1); } assert_eq!(q.len(), 0); } #[test] fn spsc() { const COUNT: usize = 100_000; let q = SegQueue::new(); scope(|scope| { scope.spawn(|_| { for i in 0..COUNT { loop { if let Ok(x) = q.pop() { assert_eq!(x, i); break; } } } assert!(q.pop().is_err()); }); scope.spawn(|_| { for i in 0..COUNT { q.push(i); } }); }) .unwrap(); } #[test] fn mpmc() { const COUNT: usize = 25_000; const THREADS: usize = 4; let q = SegQueue::::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 Ok(x) = q.pop() { break x; } }; v[n].fetch_add(1, Ordering::SeqCst); } }); } for _ in 0..THREADS { scope.spawn(|_| { for i in 0..COUNT { q.push(i); } }); } }) .unwrap(); for c in v { assert_eq!(c.load(Ordering::SeqCst), THREADS); } } #[test] fn drops() { static DROPS: AtomicUsize = AtomicUsize::new(0); #[derive(Debug, PartialEq)] struct DropCounter; impl Drop for DropCounter { fn drop(&mut self) { DROPS.fetch_add(1, Ordering::SeqCst); } } let mut rng = thread_rng(); for _ in 0..100 { let steps = rng.gen_range(0, 10_000); let additional = rng.gen_range(0, 1000); DROPS.store(0, Ordering::SeqCst); let q = SegQueue::new(); scope(|scope| { scope.spawn(|_| { for _ in 0..steps { while q.pop().is_err() {} } }); 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); } } crossbeam-queue-0.2.1/.cargo_vcs_info.json0000644000000001121360045727200142320ustar00{ "git": { "sha1": "752fe5225ecceaa674649b210cd5febb2a085f2c" } }