rs-wasm-loader/index.js

A webpack loader for Rust

const path = require('path')
const toml = require('toml')
const fs = require('fs')
const childProcess = require('child_process')


module.exports = function (source) {
    const callback = this.async()
    const rootPath = this.rootContext

    const target = 'wasm32-unknown-unknown'

    fs.readFile(`${rootPath}/Cargo.toml`, 'utf-8', (e, file) => {
        if (e) return callback(e)

        const cargoToml = toml.parse(file)

        const packageName = cargoToml.package.name.replace(/\-/g, "_")
        const libPath = cargoToml.lib.path || 'src'
        const outPath = path.join(rootPath, "target", target, "release", `${packageName}.wasm`)

        const cmd = `cargo build --target=${target} --release`

        childProcess.exec(cmd, { cwd: rootPath }, (e, stdout, stderr) => {
            if (e) return callback(e)

            fs.readFile(outPath, 'base64', (e, base64) => {
                if (e) return callback(e)

                const glueCode = `
                function _atob(base64) {
                    if(typeof atob === 'function') {
                        return atob(base64)
                    }
                    else {
                        return Buffer.from(base64, 'base64').toString('binary')
                    }   
                }
        
                function decode(encoded) {
                    let binaryString =  _atob(encoded)
                    let bytes = new Uint8Array(binaryString.length)
                    for (let i = 0; i < binaryString.length; i++) {
                        bytes[i] = binaryString.charCodeAt(i)
                    }
                    return bytes.buffer
                }
        
                module.exports = WebAssembly.instantiate(decode("${base64}"), {})
                `

                callback(null, glueCode)
            })
        })
    })
}