All files / src/components/music/helpers emulator.ts

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import { Binjgb, BinjgbModule } from "./WasmModuleWrapper";
 
type StepType = "single" | "frame" | "run";
 
type Emu = number | undefined;
 
type Emulator = {
  HEAP8: Uint8Array;
  _free: (value: number) => void;
  _malloc: (value: number) => number;
  _emulator_new_simple: (
    romPtr: number,
    romSize: number,
    sampleRate: number,
    audioBufferSize: number
  ) => Emu;
  _emulator_delete: (emu: Emu) => void;
  _emulator_get_ticks_f64: (emu: Emu) => number;
  _emulator_run_until_f64: (emu: Emu, ticks: number) => number;
  _emulator_read_mem: (emu: Emu, addr: number) => number;
  _emulator_write_mem: (emu: Emu, addr: number, value: number) => void;
  _set_audio_channel_mute: (
    emu: Emu,
    channel: number,
    muted: boolean
  ) => boolean;
  _get_audio_buffer_ptr: (emu: Emu) => number;
  _get_audio_buffer_capacity: (emu: Emu) => number;
};
 
let emu: Emu;
let romPtr: number;
let romSize = 0;
let audioCtx: AudioContext;
let audioTime: number;
 
const audioBufferSize = 2048;
 
/* see: 
  https://gist.github.com/surma/b2705b6cca29357ebea1c9e6e15684cc
  https://github.com/webpack/webpack/issues/7352
*/
const locateFile = (module: unknown) => (path: string) => {
  Iif (path.endsWith(".wasm")) {
    return module;
  }
  return path;
};
 
let Module: Emulator;
Binjgb({
  locateFile: locateFile(BinjgbModule),
}).then((module: Emulator) => {
  Module = module;
});
 
const init = (romData: Uint8Array) => {
  console.log("INIT EMULATOR");
  Iif (isAvailable()) destroy();
 
  Iif (typeof audioCtx == "undefined") audioCtx = new AudioContext();
 
  let requiredSize = ((romData.length - 1) | 0x3fff) + 1;
  Iif (requiredSize < 0x8000) requiredSize = 0x8000;
  Iif (romSize < requiredSize) {
    Iif (typeof romPtr != "undefined") Module._free(romPtr);
    romPtr = Module._malloc(requiredSize);
    romSize = requiredSize;
  }
  for (let n = 0; n < romSize; n++) Module.HEAP8[romPtr + n] = 0;
  for (let n = 0; n < romData.length; n++)
    Module.HEAP8[romPtr + n] = romData[n];
 
  emu = Module._emulator_new_simple(
    romPtr,
    romSize,
    audioCtx.sampleRate,
    audioBufferSize
  );
  audioCtx.resume();
  audioTime = audioCtx.currentTime;
};
 
const updateRom = (romData: Uint8Array) => {
  Iif (!isAvailable()) {
    console.log("UPDATE ROM: NOT AVAILABLE");
    return false;
  }
 
  let requiredSize = ((romData.length - 1) | 0x3fff) + 1;
  Iif (requiredSize < 0x8000) requiredSize = 0x8000;
  Iif (romSize < requiredSize) return false;
  for (let n = 0; n < romSize; n++) Module.HEAP8[romPtr + n] = 0;
  for (let n = 0; n < romData.length; n++)
    Module.HEAP8[romPtr + n] = romData[n];
  return true;
};
 
const destroy = () => {
  Iif (!isAvailable()) return;
  Module._emulator_delete(emu);
  emu = undefined;
};
 
const isAvailable = () => typeof emu != "undefined";
 
const step = (stepType: StepType) => {
  Iif (!isAvailable()) return;
  let ticks = Module._emulator_get_ticks_f64(emu);
  if (stepType === "single") ticks += 1;
  else Iif (stepType === "frame") ticks += 70224;
  while (true) {
    const result = Module._emulator_run_until_f64(emu, ticks);
    Iif (result & 2) processAudioBuffer();
    Iif (result & 8)
      // Breakpoint hit
      return true;
    Iif (result & 16)
      // Illegal instruction
      return true;
    Iif (result !== 2 && stepType !== "run") return false;
    Iif (stepType === "run") {
      Iif (result & 4) {
        // Sync to the audio buffer, make sure we have 100ms of audio data buffered.
        if (audioTime < audioCtx.currentTime + 0.1) ticks += 70224;
        else return false;
      }
    }
  }
};
 
const readMem = (addr: number) => {
  Iif (!isAvailable()) return 0xff;
  return Module._emulator_read_mem(emu, addr);
};
 
const writeMem = (addr: number, data: number) => {
  Iif (!isAvailable()) {
    console.log("WRITE MEM NOT AVAILABLE");
    return;
  }
  console.log("WRITE MEM", addr, data);
  return Module._emulator_write_mem(emu, addr, data);
};
 
const setChannel = (channel: number, muted: boolean) => {
  Iif (!isAvailable()) return muted;
  return Module._set_audio_channel_mute(emu, channel, muted);
};
 
function processAudioBuffer() {
  Iif (audioTime < audioCtx.currentTime) audioTime = audioCtx.currentTime;
 
  const inputBuffer = new Uint8Array(
    Module.HEAP8.buffer,
    Module._get_audio_buffer_ptr(emu),
    Module._get_audio_buffer_capacity(emu)
  );
  const volume = 0.5;
  const buffer = audioCtx.createBuffer(2, audioBufferSize, audioCtx.sampleRate);
  const channel0 = buffer.getChannelData(0);
  const channel1 = buffer.getChannelData(1);
 
  for (let i = 0; i < audioBufferSize; i++) {
    channel0[i] = (inputBuffer[2 * i] * volume) / 255;
    channel1[i] = (inputBuffer[2 * i + 1] * volume) / 255;
  }
  const bufferSource = audioCtx.createBufferSource();
  bufferSource.buffer = buffer;
  bufferSource.connect(audioCtx.destination);
  bufferSource.start(audioTime);
  const bufferSec = audioBufferSize / audioCtx.sampleRate;
  audioTime += bufferSec;
}
 
const emulator = {
  init,
  writeMem,
  readMem,
  step,
  updateRom,
  setChannel,
};
 
export default emulator;