Minimal Example of Calling Rust from R using Cargo

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.

The r-rust organization contains several example R packages interfacing with Rust. Also have a look at the slides about this project presented at eRum2018!

We simply bundle the rust code into a 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

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")

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.

Note that cargo is only needed at build-time. Rust has no runtime dependencies. To install on MacOS use homebrew:

brew install rust

And on Debian/Ubuntu:

sudo apt-get install cargo

And on Fedora / CentOS:

sudo yum install cargo

And on Arch:

sudo pacman -Sy cargo

On CentOS you first need to enable EPEL via sudo yum install epel-release.

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 and i686-pc-windows-gnu targets. First download rustup-init.exe and then install the default toolchain:

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

To compile 32bit packages also add the i686 target:

rustup target add i686-pc-windows-gnu

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

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

However, do note that for the CRAN release we used a hack in src/Makevars.win to download a precompiled version of the gifski crate on Windows, because the CRAN winbuilder did not have a Rust compiler installed.

• 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