nes-emu/helpers/Byte.spec.js

A NES emulator

"use strict";

var _Byte = _interopRequireDefault(require("./Byte"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
const should = require("chai").Should();
describe("helpers", () => {
  describe("byte", () => {
    it("can create a number from a signed byte", () => {
      _Byte.default.toNumber(0b11111011).should.equal(-5);
      _Byte.default.toNumber(0b00000101).should.equal(5);
      _Byte.default.toNumber(127).should.equal(127);
      _Byte.default.toNumber(128).should.equal(-128);
    });
    it("can create a signed byte from a number", () => {
      _Byte.default.toSignedByte(-5).should.equal(0b11111011);
      _Byte.default.toSignedByte(5).should.equal(0b00000101);
      _Byte.default.toSignedByte(127).should.equal(127);
      _Byte.default.toSignedByte(-128).should.equal(128);
    });
    it("can determine if a value has overflow", () => {
      _Byte.default.hasOverflow(258).should.equal(true);
      _Byte.default.hasOverflow(255).should.equal(false);
      _Byte.default.hasOverflow(25).should.equal(false);
      _Byte.default.hasOverflow(300).should.equal(true);
    });
    it("can determine if a value is positive or negative", () => {
      _Byte.default.isPositive(0xfe).should.equal(false);
      _Byte.default.isNegative(0xfe).should.equal(true);
      _Byte.default.isPositive(0x10).should.equal(true);
      _Byte.default.isNegative(0x10).should.equal(false);
    });
    it("can negate numbers using two's complement", () => {
      const negative112 = _Byte.default.toSignedByte(-112);
      _Byte.default.negate(112).should.equal(negative112);
      _Byte.default.negate(negative112).should.equal(112);
    });
    it("can force numbers to 8-bit", () => {
      _Byte.default.force8Bit(0b110000000).should.equal(0b10000000);
      _Byte.default.force8Bit(-2).should.equal(254);
    });
    it("can force numbers to 16-bit", () => {
      _Byte.default.force16Bit(65537).should.equal(1);
      _Byte.default.force16Bit(-2).should.equal(65534);
    });
    it("can return a bit from a number", () => {
      _Byte.default.getBit(2, 1).should.equal(1);
      _Byte.default.getBit(2, 0).should.equal(0);
      _Byte.default.getBit(0b100101, 0).should.equal(1);
      _Byte.default.getBit(0b100101, 1).should.equal(0);
      _Byte.default.getBit(0b100101, 2).should.equal(1);
      _Byte.default.getBit(0b100101, 3).should.equal(0);
      _Byte.default.getBit(0b100101, 4).should.equal(0);
      _Byte.default.getBit(0b100101, 5).should.equal(1);
      _Byte.default.getBit(0b100101, 6).should.equal(0);
    });
    it("can return a sub-number from a number", () => {
      _Byte.default.getBits(0b00001110, 1, 3).should.equal(0b111);
      _Byte.default.getBits(0b00001110, 0, 3).should.equal(0b110);
      _Byte.default.getBits(0b00001110, 0, 2).should.equal(0b10);
      _Byte.default.getBits(0b00001110, 2, 2).should.equal(0b011);
      _Byte.default.getBits(0b00001110, 3, 2).should.equal(0b01);
    });
    it("can insert a sub-number inside a byte", () => {
      _Byte.default.setBits(0b00001110, 2, 2, 0b10).should.equal(0b00001010);
      _Byte.default.setBits(0b00001110, 2, 2, 0b01).should.equal(0b00000110);
      _Byte.default.setBits(0b00001110, 2, 5, 0b10101).should.equal(0b01010110);
    });
    it("can split 16-bit numbers", () => {
      _Byte.default.highPartOf(0xfe20).should.equal(0xfe);
      _Byte.default.lowPartOf(0xfe20).should.equal(0x20);
    });
    it("can create 16-bit numbers from two bytes", () => {
      _Byte.default.to16Bit(0xfe, 0x12).should.equal(0xfe12);
    });
  });
});