nes-emu/controller/PrimaryControllerPort.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _ControllerPort = _interopRequireDefault(require("./ControllerPort"));
var _helpers = require("../helpers");
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
const STROBE_BIT = 0;

/**
 * Primary Controller Port Register (<> read/write)
 *
 * Writing a value here affects the "strobe" flag (bit 0).
 * Games usually write 1, then 0, and then perform 8 consecutive reads to get the state of all buttons.
 */
class PrimaryControllerPort extends _ControllerPort.default {
  constructor() {
    super();
    this._strobe = false;
    this._secondary = null;
  }

  /** Returns the strobe flag. */
  get strobe() {
    return this._strobe;
  }

  /** Sets a `secondary` controller port, that will be affected by the strobe flag. */
  setSecondary(secondary) {
    this._secondary = secondary;
  }

  /** Writes the strobe flag, potentially resetting the cursor. */
  writeAt(__, byte) {
    this._strobe = !!_helpers.Byte.getBit(byte, STROBE_BIT);
    if (this._strobe) {
      this.cursor = 0;
      if (this._secondary) this._secondary.cursor = 0;
    }
  }
}
exports.default = PrimaryControllerPort;