nes-emu/memory/MemoryChunk.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _WithLittleEndian = _interopRequireDefault(require("./WithLittleEndian"));
var _lodash = _interopRequireDefault(require("lodash"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
/** A memory chunk that can store `bytes` (it can be a number or a Buffer). */
class MemoryChunk {
  constructor(bytes) {
    _WithLittleEndian.default.apply(this);
    if (_lodash.default.isFinite(bytes)) bytes = new Uint8Array(bytes);
    this.bytes = bytes;
    this.readOnly = false;
    this.memorySize = bytes.length;
  }

  /** Reads a byte from `address`. */
  readAt(address) {
    this._assertValidAddress(address);
    return this.bytes[address];
  }

  /** Writes a `byte` to `address`. */
  writeAt(address, byte) {
    this._assertValidAddress(address);
    if (this.readOnly) return;
    this.bytes[address] = byte;
  }

  /** Sets the chunk's `readOnly` state. */
  asReadOnly() {
    let readOnly = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : true;
    this.readOnly = readOnly;
    return this;
  }
  _assertValidAddress(address) {
    if (address < 0 || address > this.memorySize) this._throwInvalidAddressError(address);
  }
  _throwInvalidAddressError(address) {
    throw new Error("Invalid memory access at 0x".concat(address.toString(16), "."));
  }
}
exports.default = MemoryChunk;