Add Wasm implementation

[nlordell]

This PR adds a hand-written Wasm FizzBuzz implementation. It uses WASI fd_write for writing to standard out, so it should work for any WASI-compliant runtimes (such as Wasmtime or Wasmer). I tried hard to add descriptive comments explaining what is going on.

Alternatively, you can run this with JavaScript. Here is a sample host implementation that runs with Node.js. Note that using with the JavaScript WebAssembly interface requires byte-encoded Wasm, so something like wat2wasm fizzbuzz.wat needs to be done first in order to generate a Wasm binary module.

host.js

const assert = require("assert");
const fs = require("fs").promises;
const path = require("path");

const le = true;
const decoder = new TextDecoder("utf-8");

async function main() {
  const filename = path.join(__dirname, "fizzbuzz.wasm");
  const wasm = await fs.readFile(filename);
  const { instance } = await WebAssembly.instantiate(wasm, {
    wasi_snapshot_preview1: {
      fd_write: (fd, iovs, iovs_len, nwritten) => {
        assert(fd === 1, "only stdout supported");

        const buffer = instance.exports.memory.buffer;
        const view = new DataView(buffer);

        let out = "";
        let n = 0;
        for (let i = 0; i < iovs_len; i++) {
          const iov = iovs + 8*i;
          const base = view.getUint32(iov, le);
          const len = view.getUint32(iov + 4, le);

          out += decoder.decode(new Uint8Array(buffer, base, len));
          n += len;
        }

        console.log(out.trim());
        view.setUint32(nwritten, n, le);

        return 0;
      },
    },
  });

  instance.exports._start();
}

main().catch((err) => console.error(err));

[NullDev]

Awesome! Thank you :D
I'm reevaluating the Top 5 solutions in the readme.
May I feature your solution?

[nlordell]

May I feature your solution?

That would be awesome! 😄

Also, on a side note, I noticed how many PR submissions you get and how you take the time to answer them all. I tip my hat to you, sir.

[NullDev]

That would be awesome! smile

Perfect! Added it :)

Also, on a side note, I noticed how many PR submissions you get and how you take the time to answer them all. I tip my hat to you, sir.

Well, I didn't expect so many PR's to be honest :')
Thank you :'D