crossbeam 0.8.4

Tools for concurrent programming
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158

# Crossbeam

[![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#license)
[![Cargo](https://img.shields.io/crates/v/crossbeam.svg)](
https://crates.io/crates/crossbeam)
[![Documentation](https://docs.rs/crossbeam/badge.svg)](
https://docs.rs/crossbeam)
[![Rust 1.61+](https://img.shields.io/badge/rust-1.61+-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 a set of tools for concurrent programming:

#### Atomics

* [`AtomicCell`], a thread-safe mutable memory location.<sup>(no_std)</sup>
* [`AtomicConsume`], for reading from primitive atomic types with "consume" ordering.<sup>(no_std)</sup>

#### Data structures

* [`deque`], work-stealing deques for building task schedulers.
* [`ArrayQueue`], a bounded MPMC queue that allocates a fixed-capacity buffer on construction.<sup>(alloc)</sup>
* [`SegQueue`], an unbounded MPMC queue that allocates small buffers, segments, on demand.<sup>(alloc)</sup>

#### Memory management

* [`epoch`], an epoch-based garbage collector.<sup>(alloc)</sup>

#### Thread synchronization

* [`channel`], multi-producer multi-consumer channels for message passing.
* [`Parker`], a thread parking primitive.
* [`ShardedLock`], a sharded reader-writer lock with fast concurrent reads.
* [`WaitGroup`], for synchronizing the beginning or end of some computation.

#### Utilities

* [`Backoff`], for exponential backoff in spin loops.<sup>(no_std)</sup>
* [`CachePadded`], for padding and aligning a value to the length of a cache line.<sup>(no_std)</sup>
* [`scope`], for spawning threads that borrow local variables from the stack.

*Features marked with <sup>(no_std)</sup> can be used in `no_std` environments.*<br/>
*Features marked with <sup>(alloc)</sup> can be used in `no_std` environments, but only if `alloc`
feature is enabled.*

[`AtomicCell`]: https://docs.rs/crossbeam/*/crossbeam/atomic/struct.AtomicCell.html
[`AtomicConsume`]: https://docs.rs/crossbeam/*/crossbeam/atomic/trait.AtomicConsume.html
[`deque`]: https://docs.rs/crossbeam/*/crossbeam/deque/index.html
[`ArrayQueue`]: https://docs.rs/crossbeam/*/crossbeam/queue/struct.ArrayQueue.html
[`SegQueue`]: https://docs.rs/crossbeam/*/crossbeam/queue/struct.SegQueue.html
[`channel`]: https://docs.rs/crossbeam/*/crossbeam/channel/index.html
[`Parker`]: https://docs.rs/crossbeam/*/crossbeam/sync/struct.Parker.html
[`ShardedLock`]: https://docs.rs/crossbeam/*/crossbeam/sync/struct.ShardedLock.html
[`WaitGroup`]: https://docs.rs/crossbeam/*/crossbeam/sync/struct.WaitGroup.html
[`epoch`]: https://docs.rs/crossbeam/*/crossbeam/epoch/index.html
[`Backoff`]: https://docs.rs/crossbeam/*/crossbeam/utils/struct.Backoff.html
[`CachePadded`]: https://docs.rs/crossbeam/*/crossbeam/utils/struct.CachePadded.html
[`scope`]: https://docs.rs/crossbeam/*/crossbeam/fn.scope.html

## Crates

The main `crossbeam` crate just [re-exports](src/lib.rs) tools from
smaller subcrates:

* [`crossbeam-channel`](crossbeam-channel)
  provides multi-producer multi-consumer channels for message passing.
* [`crossbeam-deque`](crossbeam-deque)
  provides work-stealing deques, which are primarily intended for building task schedulers.
* [`crossbeam-epoch`](crossbeam-epoch)
  provides epoch-based garbage collection for building concurrent data structures.
* [`crossbeam-queue`](crossbeam-queue)
  provides concurrent queues that can be shared among threads.
* [`crossbeam-utils`](crossbeam-utils)
  provides atomics, synchronization primitives, scoped threads, and other utilities.

There is one more experimental subcrate that is not yet included in `crossbeam`:

* [`crossbeam-skiplist`](crossbeam-skiplist)
  provides concurrent maps and sets based on lock-free skip lists.

## Usage

Add this to your `Cargo.toml`:

```toml
[dependencies]
crossbeam = "0.8"
```

## Compatibility

Crossbeam 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 1.61.

## Contributing

Crossbeam welcomes contribution from everyone in the form of suggestions, bug reports,
pull requests, and feedback. 💛

If you need ideas for contribution, there are several ways to get started:

* Found a bug or have a feature request?
  [Submit an issue](https://github.com/crossbeam-rs/crossbeam/issues/new)!
* Issues and PRs labeled with
  [feedback wanted](https://github.com/crossbeam-rs/crossbeam/issues?utf8=%E2%9C%93&q=is%3Aopen+sort%3Aupdated-desc+label%3A%22feedback+wanted%22+)
  need feedback from users and contributors.
* Issues labeled with
  [good first issue](https://github.com/crossbeam-rs/crossbeam/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc+label%3A%22good+first+issue%22)
  are relatively easy starter issues.

#### RFCs

We also have the [RFCs](https://github.com/crossbeam-rs/rfcs) repository for more
high-level discussion, which is the place where we brainstorm ideas and propose
substantial changes to Crossbeam.

You are welcome to participate in any open
[issues](https://github.com/crossbeam-rs/rfcs/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc)
or
[pull requests](https://github.com/crossbeam-rs/rfcs/pulls?q=is%3Apr+is%3Aopen+sort%3Aupdated-desc).

#### Learning resources

If you'd like to learn more about concurrency and non-blocking data structures, there's a
list of learning resources in our [wiki](https://github.com/crossbeam-rs/rfcs/wiki),
which includes relevant blog posts, papers, videos, and other similar projects.

Another good place to visit is [merged RFCs](https://github.com/crossbeam-rs/rfcs/tree/master/text).
They contain elaborate descriptions and rationale for features we've introduced to
Crossbeam, but keep in mind that some of the written information is now out of date.

#### Conduct

The Crossbeam project adheres to the
[Rust Code of Conduct](https://www.rust-lang.org/policies/code-of-conduct).
This describes the minimum behavior expected from all contributors.

## 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.

Some Crossbeam subcrates have additional licensing notices.
Take a look at other readme files in this repository for more information.

#### 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.