Rust WASM Example

Example on compiling a Rust library into WebAssembly

Instructions

Install wasm-pack:

curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh

Clone this repo:

git clone https://github.com/miguelmota/rust-wasm-example

cd rust-wasm-example/

The example library exposes a fib function which calculates the Fibonacci number of the given number:

#[no_mangle]
pub extern "C" fn fib(n: i32) -> i32 {
    if n == 1 || n == 2 {
        1
    } else {
        fib(n - 1) + fib(n - 2)
    }
}

Build WASM:

wasm-pack build

Output location:

./target/wasm32-unknown-unknown/release/rust_wasm_example.wasm

You can now use the compiled wasm in your program. In this example, well load it as a Node.js module:

const fs = require('fs')
const path = require('path')

const buf = fs.readFileSync(path.resolve(__dirname, '../target/wasm32-unknown-unknown/release/rust_wasm_example.wasm'))

const lib = (await WebAssembly.instantiate(new Uint8Array(buf))).instance.exports

console.log(lib.fib(10)) // 55

Tested using rustc 1.30.1, cargo 1.30.0, node 10.13.0

Resources

• wasm-pack
• rust wasm hello world
• wasm-pack-template

License

MIT