Roto

Roto is an embedded scripting language that is fast, safe and easy to use.

Primarily used by Rotonda, the composable, programmable routing BGP engine. It is made to integrate especially well with Rotonda, so that writing filters is as simple as possible.

Read more about it in the documentation.

Example

# A function that returns true if an IP address is equal to 0.0.0.0
function is_zero(x: IpAddr) -> bool {
    x == 0.0.0.0
}

# A filtermap that only accepts IP addresses of 0.0.0.0
filtermap main(x: IpAddr) {
    if is_zero(x) {
        accept
    } else {
        reject
    }
}

More examples can be found in the examples folder in this repository. They can be run with

cargo run --example <example name>

Features

• Roto can be embedded into any Rust application. Rust types and functions can be registered for use in Roto.
• Roto is strongly and statically-typed, ensuring that type errors are caught at compile-time. This does not mean that the user has to specify types everywhere, most types can be inferred by the Roto compiler. When the compiler detects a mistake in your script, it will emit a friendly message.
• Scripts are compiled to machine code before they are executed. This means that they run quickly and introduce minimal latency into your system.
• Roto scripts are hot-reloadable. The host application can recompile scripts at any time.

Limitations

• All registered Rust types must implement Clone or Copy. Rust types that don't implement these traits should be wrapped in an Rc or Arc. The reason for this limitation is that Roto does not have references.
• The parameter and return types of functions exported to the host application are static.
• Roto currently does not feature any looping constructs. If you need loops, you can use recursion instead as a workaround.
• All values are currently immutable. If a type should be mutable and shared between multiple variables, it can be wrapped in a type that provides interior mutability such as Rc<RefCell<T>> and Arc<Mutex<T>>.

Learn more

• Documentation of the Roto language is included in the documentation for Rotonda.
• The API docs for the latest version are available on docs.rs
• Some examples are available in the examples folder of the Roto repository.

Contributing

If you have comments, proposed changes, or would like to contribute, please open an issue in the GitHub repository. In particular, if you would like to use the crate but it is missing functionality for your use case, we would love to hear from you!

License

The roto crate is distributed under the terms of the BSD-3-clause license. See LICENSE for details.