Real-Time Ring Buffer
=====================
A wait-free single-producer single-consumer (SPSC) ring buffer for Rust.
* Crate: https://crates.io/crates/rtrb
* Documentation: https://docs.rs/rtrb
This crate can be used without the standard library (`#![no_std]`)
by disabling the `std` feature (which is enabled by default),
but the [alloc](https://doc.rust-lang.org/alloc/) crate is needed nevertheless.
Usage
-----
Add this to your `Cargo.toml`:
```toml
[dependencies]
rtrb = "0.3"
```
Breaking Changes
----------------
For a list of breaking changes
and for instructions how to upgrade between released versions,
have a look at the [changelog](https://github.com/mgeier/rtrb/releases).
Performance
-----------
Measuring the performance of a data structure for inter-thread communication
can be quite brittle and the results depend on many factors.
A few performance comparisons between competing crates are shown in
[issue #39](https://github.com/mgeier/rtrb/issues/39),
but like all benchmarks, they are deeply flawed and to be taken with a grain of salt.
You should make your own measurements that are relevant to your usage patterns.
Feel free to share your own results by commenting on that issue.
Development
-----------
Creating the HTML docs (which will be available in `target/doc/rtrb/index.html`):
cargo doc
Running the tests:
cargo test
Testing the benchmarks (without actually benchmarking):
cargo test --benches
Running the benchmarks (using the [criterion](https://docs.rs/criterion/) crate;
results will be available in `target/criterion/report/index.html`):
cargo bench
Creating [flame graphs](https://github.com/flamegraph-rs/flamegraph) for the benchmarks;
first a few preparations:
cargo install flamegraph
echo -1 | sudo tee /proc/sys/kernel/perf_event_paranoid
export CARGO_PROFILE_BENCH_DEBUG=true
Then, creating the flame graph (which will be saved to `flamegraph.svg`),
providing a benchmark (e.g. `two_threads`), a desired runtime and optionally
a benchmark function (e.g. `large`):
cargo flamegraph --bench two_threads -- --bench --profile-time 10 large
To measure code coverage, nightly Rust is required, as well as a few additional dependencies:
rustup toolchain install nightly
rustup component add llvm-tools-preview
cargo install grcov
Test coverage data can be obtained and analyzed with these commands:
cargo clean
RUSTFLAGS="-Z instrument-coverage" RUSTDOCFLAGS="-Z instrument-coverage -Z unstable-options --persist-doctests target/debug/doctestbins" LLVM_PROFILE_FILE="coverage/%p-%m.profraw" cargo +nightly test
grcov coverage --source-dir . --binary-path target/debug --output-type html --output-path coverage
The last command creates an HTML report in `coverage/index.html`.
Testing with Miri also needs nightly Rust:
cargo +nightly miri test
This Miri flag should also be tried:
MIRIFLAGS="-Zmiri-preemption-rate=0" cargo +nightly miri test
Running the tests with ThreadSanitizer requires nightly Rust as well:
RUSTFLAGS="-Z sanitizer=thread" cargo +nightly test --tests -Z build-std --target x86_64-unknown-linux-gnu
You might have to adapt the `--target` option to your system (see e.g. `rustup show`).
Minimum Supported `rustc` Version
---------------------------------
This crate's minimum supported `rustc` version (MSRV) is `1.38.0`.
The MSRV is not expected to be updated frequently, but if it is,
there will be (at least) a *minor* version bump.
Origin Story
------------
The initial code has been ripped off of https://github.com/crossbeam-rs/crossbeam/pull/338,
with permission of the PR author.
It has been isolated from the rest of `crossbeam` with [git-filter-repo]:
git-filter-repo --subdirectory-filter crossbeam-queue --path src/spsc.rs --path tests/spsc.rs --refs refs/heads/spsc
[git-filter-repo]: https://github.com/newren/git-filter-repo
Alternatives
------------
If you don't like this crate, no problem, there are several alternatives for you to choose from.
There are many varieties of ring buffers available, here we limit the selection
to wait-free SPSC implementations:
* [ach-spsc](https://crates.io/crates/ach-spsc) (using const generics)
* [heapless](https://crates.io/crates/heapless) (for embedded systems, see `heapless::spsc`)
* [jack](https://crates.io/crates/jack) (FFI bindings for JACK, see `jack::Ringbuffer`)
* [magnetic](https://crates.io/crates/magnetic) (see `magnetic::spsc` module)
* [npnc](https://crates.io/crates/npnc) (see `npnc::bounded::spsc` module)
* [ringbuf](https://crates.io/crates/ringbuf) (supports const generics and heap allocation)
* [ringbuffer-spsc](https://crates.io/crates/ringbuffer-spsc) (using const generics)
* [shmem-ipc](https://crates.io/crates/shmem-ipc) (see `shmem_ipc::sharedring` and `shmem_ipc::ringbuf` modules)
There are also implementations in other languages:
* [boost::lockfree::spsc_queue](https://www.boost.org/doc/libs/master/doc/html/boost/lockfree/spsc_queue.html) (C++)
* [folly::ProducerConsumerQueue](https://github.com/facebook/folly/blob/main/folly/docs/ProducerConsumerQueue.md) (C++)
* [JACK ring buffer](https://jackaudio.org/api/ringbuffer_8h.html) (C)
* [PortAudio ring buffer](http://portaudio.com/docs/v19-doxydocs-dev/pa__ringbuffer_8h.html) (C)
* [readerwriterqueue](https://github.com/cameron314/readerwriterqueue) (C++)
* [ringbuf.js](https://github.com/padenot/ringbuf.js) (JavaScript, using `SharedArrayBuffer`)
* [SPSCQueue](https://github.com/rigtorp/SPSCQueue) (C++)
If you know more alternatives for this list,
please [open an issue](https://github.com/mgeier/rtrb/issues).
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.
Note that this crate contains a copy of the file `cache_padded.rs` from
https://github.com/crossbeam-rs/crossbeam.
#### 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.