Rustler

Documentation | Getting Started | Example

Rustler is a library for writing Erlang NIFs in safe Rust code. That means there should be no ways to crash the BEAM (Erlang VM). The library provides facilities for generating the boilerplate for interacting with the BEAM, handles encoding and decoding of Erlang terms, and catches rust panics before they unwind into C.

The library provides functionality for both Erlang and Elixir, however Elixir is favored as of now.

Features:

• Safety - The code you write in a Rust NIF should never be able to crash the BEAM.
• Interop - Decoding and encoding rust values into Erlang terms is as easy as a function call.
• Type composition - Making a Rust struct encodable and decodable to Erlang or Elixir can be done with a single attribute.
• Resource objects - Enables you to safely pass a reference to a Rust struct into Erlang code. The struct will be automatically dropped when it's no longer referenced.

Getting started

The easiest way of getting started is the rustler elixir library.

• Add the rustler elixir library as a dependency of your project.
• Run mix rustler.new to generate a new NIF in your project. Follow the instructions.
• If you're already using serde, consider using serde_rustler to easily encode and decode your data types into and from Elixir terms.

NOTE: If you have previously used Rustler, you need to run mix archive.uninstall rustler_installer.ez to remove it before generating the NIF.

What it looks like

This is the code for a minimal NIF that adds two numbers and returns the result.

#[rustler::nif]
fn add(a: i64, b: i64) -> i64 {
    a + b
}

rustler::init!("Elixir.Math", [add]);

Minimal Supported Rust Version (MSRV)

Rustler currently has a minimal supported Rust version (MSRV) of 1.56.1. This is the configured version in .clippy.toml.

Supported OTP and Elixir Versions

Rustler aims to support the newest three major OTP versions as well as newest three minor Elixir versions.

Supported NIF version

The minimal supported NIF version for a library should be defined via Cargo features. The default is currently 2.14 (Erlang/OTP 21). To use features from NIF version 2.16 (Erlang/OTP 24), the respective feature flag has to be enabled on the dependency:

[dependencies]
rustler = { version = "...", features = ["nif_version_2_16"] }

Community

You can find us in the #rustler:matrix.org channel on Matrix or in the #rustler channel in the Elixir lang Slack.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (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.