run.js

#!/usr/bin/env node

if (process.argv.length != 3 || process.argv[2].slice(-4) != ".ch8") {
  console.error("Supply the path to a CHIP-8 ROM (*.ch8) as an argument");
  process.exit(1);
}

import fs from "fs";
const program = new Uint8Array(fs.readFileSync(process.argv[2]));

import types from "./docs/js/shared/types.js";
import Input from "./input.js";

const input = new Input();

import "./docs/js/lib/wasm_exec.js";
let cpu;
const go = new Go();
const mod = new WebAssembly.Module(fs.readFileSync("./docs/silicon8.wasm"));
Object.assign(go.importObject.env, {
  randomByte: () => Math.floor(Math.random() * Math.floor(256)),
  playSound: () => process.stdout.write("\x07"),
  stopSound: () => {},
  render: (width, height, dataPtr) => {
    const data = new Uint8Array(cpu.memory.buffer, dataPtr, width * height * 3);
    render(data, width, height);
  },
});
const instance = new WebAssembly.Instance(mod, go.importObject);
cpu = instance.exports;
go.run(instance);
setInterval(() => cpu.clockTick(), 1000 / 60);
cpu.reset(types.AUTO);

// Load program into RAM
const ram = new Uint8Array(cpu.memory.buffer, cpu.ramPtr(), cpu.ramSize());
for (let i = 0x200; i < 0x200 + program.length; i++)
  ram[i] = program[i - 0x200];

const keys = {
  up: 5,
  left: 7,
  down: 8,
  right: 9,
};
input.addKeyListener((key) => {
  if (Object.keys(keys).includes(key)) {
    cpu.pressKey(keys[key]);
    setTimeout(() => cpu.releaseKey(keys[key]), 100);
  }
});

function render(data, width, height) {
  for (let y = 0; y < height; y++) {
    let line = "";
    for (let x = 0; x < width; x++) {
      // Take the average colour, reducing the image to monochrome
      const index = (y * width + x) * 3;
      const byte = (data[index + 0] + data[index + 1] + data[index + 2]) / 3;
      let character = "  ";
      if (byte > 0x00) character = "··";
      if (byte > 0x55) character = "⠿⠿";
      if (byte > 0xaa) character = "██";
      line += character;
    }
    console.log(line);
  }
}