webpack/tooling/generate-wasm-code.js

const path = require("path");
const fs = require("fs");
const asc = require("assemblyscript/cli/asc");

// When --write is set, files will be written in place
// Otherwise it only prints outdated files
const doWrite = process.argv.includes("--write");

const files = ["lib/util/hash/xxhash64.js", "lib/util/hash/md4.js"];

(async () => {
	await asc.ready;
	for (const file of files) {
		const filePath = path.resolve(__dirname, "..", file);
		const content = fs.readFileSync(filePath, "utf-8");

		const regexp =
			/\n\/\/#region wasm code: (.+) \((.+)\)(.*)\n[\s\S]+?\/\/#endregion\n/g;

		const replaces = new Map();

		let match = regexp.exec(content);
		while (match) {
			const [fullMatch, identifier, name, flags] = match;

			const sourcePath = path.resolve(filePath, "..", name);
			const sourcePathBase = path.join(
				path.dirname(sourcePath),
				path.basename(sourcePath)
			);

			await new Promise((resolve, reject) => {
				asc.main(
					[
						sourcePath,
						// cspell:word Ospeed
						"-Ospeed",
						"--noAssert",
						"--converge",
						"--textFile",
						sourcePathBase + ".wat",
						"--binaryFile",
						sourcePathBase + ".wasm",
						...flags.split(" ").filter(Boolean)
					],
					{
						stdout: process.stdout,
						stderr: process.stderr
					},
					err => {
						if (err) return reject(err), 0;
						resolve();
						return 0;
					}
				);
			});

			const wasm = fs.readFileSync(sourcePathBase + ".wasm");

			replaces.set(
				fullMatch,
				`
//#region wasm code: ${identifier} (${name})${flags}
const ${identifier} = new WebAssembly.Module(
	Buffer.from(
		// ${wasm.length} bytes
		${JSON.stringify(wasm.toString("base64"))},
		"base64"
	)
);
//#endregion
`
			);
			match = regexp.exec(content);
		}

		const newContent = content.replace(regexp, match => replaces.get(match));

		if (newContent !== content) {
			if (doWrite) {
				fs.writeFileSync(filePath, newContent, "utf-8");
				console.error(`${file} updated`);
			} else {
				console.error(`${file} need to be updated`);
				process.exitCode = 1;
			}
		}
	}
})();