nes-emu/cpu/Stack.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _constants = _interopRequireDefault(require("../constants"));
var _helpers = require("../helpers");
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
/** An in-memory stack, controlled by the CPU. */
class Stack {
  constructor() {
    _helpers.WithContext.apply(this);
  }

  /** Pushes a `value` into the stack. */
  push(value) {
    this.context.memoryBus.cpu.writeAt(this.currentAddress, value);
    this.context.cpu.sp.decrement();
  }

  /** Pulls a value from the stack. */
  pop() {
    this.context.cpu.sp.increment();
    return this.context.cpu.memory.readAt(this.currentAddress);
  }

  /** Pushes a 16-bit `value` into the stack. */
  push2Bytes(value) {
    const low = _helpers.Byte.lowPartOf(value);
    const high = _helpers.Byte.highPartOf(value);
    this.push(high);
    this.push(low);
  }

  /** Pulls a 16-bit `value` from the stack. */
  pop2Bytes() {
    const low = this.pop();
    const high = this.pop();
    return _helpers.Byte.to16Bit(high, low);
  }

  /** Returns the current address of the stack. */
  get currentAddress() {
    return _constants.default.CPU_STACK_START_ADDRESS + this.context.cpu.sp.value;
  }
}
exports.default = Stack;