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WebAssembly with Rust

note
  • WebAssembly support for Rust is excellent.
  • Rust is the most popular and desirable language to work with WebAssembly.
  • Both Enarx and wasmtime (Enarx's runtime) are written in Rust.
  • The Enarx team has contributed upstream to WASI sockets, threads, and crypto.

Install Rust​

To install Rust, go to rust-lang.org and follow the instructions using rustup.

Install WebAssembly Rust toolchain​

 rustup target install wasm32-wasi

Rust code​

The code below caculates a Fibonacci sequence. Let's create a new project using the command:

cargo new fibonacci

You can use any IDE of your choice and open up this project folder. Replace the main.rs file under the src folder with:

use std::env::args;
use std::io::stdin;

fn fib(n: u32) -> u32 {
    match n {
        0 => 0,
        1 => 1,
        n => fib(n - 1) + fib(n - 2),
    }
}

fn main() {
    println!("Rust - Fibonacci sequence example");

    let mut args: Vec<_> = args().skip(1).collect();

    if args.is_empty() {
        println!("Enter a non-negative number:");
        let mut idx = String::new();
        stdin().read_line(&mut idx).expect("Failed to read line");
        args.push(idx);
    }

    for arg in args {
        let idx = arg.trim().parse().expect("Failed to parse number");
        println!("Fibonacci sequence number at index {} is {}", idx, fib(idx));
    }
}
tip

Access the Rust codex repository for code samples, including the fibonacci example.

Compile Rust​

Compile using cargo:

cargo build
cargo run

Compile to Wasm​

cargo build --release --target=wasm32-wasi

Run with Enarx​

Run the fibonacci example using Enarx:

enarx run target/wasm32-wasi/release/fibonacci.wasm