nes-emu/apu/synthesis/PulseOscillator.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _config = _interopRequireDefault(require("../../config"));
var _constants = _interopRequireDefault(require("../../constants"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
const APU_SAMPLE_RATE = 44100;

/** A pulse wave generator. */
class PulseOscillator {
  constructor() {
    this.volume = _constants.default.APU_MAX_VOLUME;
    this.dutyCycle = 0; // (0~1)

    this.frequency = 0;
    this._phase = 0; // (0~1)
  }

  /** Generates a new sample. */
  sample(isNewSample) {
    if (isNewSample) this._phase = (this._phase + this.frequency / APU_SAMPLE_RATE) % 1;
    return (this._phase < this.dutyCycle ? this.volume : 0) * _config.default.PULSE_CHANNEL_VOLUME;
  }

  /** Returns a snapshot of the current state. */
  getSaveState() {
    return {
      volume: this.volume,
      dutyCycle: this.dutyCycle,
      frequency: this.frequency,
      phase: this._phase
    };
  }

  /** Restores state from a snapshot. */
  setSaveState(saveState) {
    this.volume = saveState.volume;
    this.dutyCycle = saveState.dutyCycle;
    this.frequency = saveState.frequency;
    this._phase = saveState.phase;
  }
}
exports.default = PulseOscillator;