Hello Rust

Minimal Examples of Using Rust Code in R

Rust is a modern alternative to C and compiled rust code is ABI compatible with C. Many Rust libraries include C API headers so that the compiled rust code can be called from R/C/C++ as if it were C code. This package shows how to do this. The r-rust organization contains several more simple R packages interfacing with cargo crates.

To learn more about using Rust code in R packages, also have a look at the r-rust FAQ and the slides about this project presented at eRum2018!

Package Structure

Bundle your rust code in a the embedded cargo package (see the Cargo.toml file) and then the src/Makevars file is written such that R will automatically build the rust modules when the R package is installed.

hellorust
├─ configure            ← checks if 'cargo' is installed
├─ src
│  ├─ myrustlib            ← bundled cargo package with your code
│  |  ├─ Cargo.toml          ← cargo dependencies and metadata
│  |  ├─ src                 ← rust source code
│  |  └─ api.h               ← C headers for exported rust API
|  |
│  ├─ Makevars          ← Ties everything together
│  └─ wrapper.c         ← C code for R package
├─ DESCRIPTION
└─ R                    ← Standard R+C stuff

Vendoring

As per the new 2023 cran guidelines we now vendor the cargo crates in the R source packages in order to support offline installation. This is done in a two step process:

1. (by package author) The vendor-update.sh script creates the vendor.tar.xz bundle that contains all the cargo sources. In addition, the vendor-authors.R script generates an inst/AUTHORS file that lists the authors of the dependencies, as required by CRAN. Both of these scripts are called in the package cleanup file and therefore run automatically during R CMD build when the source package is created.
2. (by the user) At install time, the Makevars extracts the vendor.tar.xz bundle (when available) and generates a .cargo/config.toml file to instruct cargo build to use the vendored (offline) sources.

If you run R CMD INSTALL directly from a checkout (without building a source package), then no vendor.tar.xz is created and cargo falls back to downloading crates on-the-fly.

You can test or force the use of vendored sources by passing --offline to cargo build.

Installing this package

If Rust is available, clone this repository and run the regular R CMD INSTALL command:

R CMD INSTALL hellorust

Alternatively, to download and install from within R itself:

# install.packages("remotes")
remotes::install_github("r-rust/hellorust")

What is Cargo

The standard rust toolchain includes a great package manager cargo with a corresponding registry crates.io. Cargo makes it very easy to build a rust package including all dependencies into a static library that can easily be linked into an R package.

This is perfect for R because we can compile and link all rust code at build-time without any system dependencies. Rust itself has no substantial runtime so the resulting R package is entirely self contained. Indeed, rust has been designed specifically to serve well as an embedded language.

Installing Rust on Linux / MacOS

Note that cargo is only needed at build-time. Rust has no runtime dependencies. The easiest way to install the latest version of Rust (including cargo) is from: https://www.rust-lang.org/tools/install

Alternatively, you may install cargo from your OS package manager:

• Debian/Ubuntu: sudo apt-get install cargo
• Fedora/CentOS*: sudo yum install cargo
• MacOS: brew install rustc

*Note that on CentOS you first need to enable EPEL via sudo yum install epel-release.

Installing Rust for R on Windows

In order for rust to work with R you need to install the toolchain using rustup and then add the x86_64-pc-windows-gnu target. First download rustup-init.exe and then install the default toolchain:

rustup-init.exe -y --default-host x86_64-pc-windows-gnu

Or if rust is already installed (for example on GitHub actions), you can simply add the target:

rustup target add x86_64-pc-windows-gnu

To compile 32bit packages also add the i686-pc-windows-gnu target, but 32-bit is no longer supported as of R 4.2.

GitHub Actions

Update 2023: This step is no longer needed because GitHub action runners now have the required Rust targets preinstalled by default.

To use GitHub actions, you can use the standard r workflow script in combination with this extra step:

- name: Add Rtools targets to Rust
  if: runner.os == 'Windows'
  run: |
    rustup target add i686-pc-windows-gnu
    rustup target add x86_64-pc-windows-gnu

In the real world

The gifski package has been on CRAN since 2018, and uses this same structure.

More Resources

• r-rust FAQ
• Erum2018 slides about this project presented by Jeroen
• Rust Inside Other Languages chapter from official rust documentation
• extendr: a more advanced R extension interface using Rust
• Duncan's proof of concept: RCallRust