broken-neees/lib/InMemoryRegister.js

A really broken NEEES emulator that introduces glitches and random bugs on purpose!

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _byte = _interopRequireDefault(require("./byte"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
/** An 8-bit register with multiple status flags and values mapped to memory. */
class InMemoryRegister {
  constructor() {
    this.value = 0;
    this._readOnlyFields = [];
    this.onLoad();
  }

  /** Called when instantiating the register. */
  onLoad() {}

  /** Called when the CPU reads the memory address. */
  onRead() {
    return 0;
  }

  /** Called when the CPU writes the memory address. */
  onWrite(value) {}

  /** Sets the value manually (updating internal accessors). */
  setValue(value) {
    this.value = _byte.default.toU8(value);
    this._writeReadOnlyFields();
  }

  /** Adds a read-only field of `size` bits named `name`, starting at `startPosition`. */
  addField(name, startPosition) {
    let size = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : 1;
    this._readOnlyFields.push({
      name,
      startPosition,
      size
    });
    this[name] = 0;
    return this;
  }

  /** Adds a writable field of `size` bits named `name`, starting at `startPosition`. */
  addWritableField(name, startPosition) {
    let size = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : 1;
    Object.defineProperty(this, name, {
      get() {
        return _byte.default.getBits(this.value, startPosition, size);
      },
      set(value) {
        this.value = _byte.default.toU8(_byte.default.setBits(this.value, startPosition, size, value));
      }
    });
    return this;
  }
  _writeReadOnlyFields() {
    for (let {
      name,
      startPosition,
      size
    } of this._readOnlyFields) this[name] = _byte.default.getBits(this.value, startPosition, size);
  }
  static get PPU() {
    return class PPUInMemoryRegister extends InMemoryRegister {
      constructor(ppu) {
        super();
        this.ppu = ppu;
      }
    };
  }
  static get APU() {
    return class APUInMemoryRegister extends InMemoryRegister {
      constructor(apu, id) {
        super();
        this.apu = apu;
        this.id = id;
      }
    };
  }
}
exports.default = InMemoryRegister;