nes-emu/cpu/instructions/branching.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
const instructions = () => [
/**
 * Branch if Carry Clear
 *
 * If the C flag is clear, jumps to `address`.
 */
{
  id: "BCC",
  execute: B__("c", false)
},
/**
 * Branch if Carry Set
 *
 * If the C flag is set, jumps to `address`.
 */
{
  id: "BCS",
  execute: B__("c", true)
},
/**
 * Branch if Equal
 *
 * If the Z flag is set, jumps to `address`.
 */
{
  id: "BEQ",
  execute: B__("z", true)
},
/**
 * Branch if Minus
 *
 * If the N flag is set, jumps to `address`.
 */
{
  id: "BMI",
  execute: B__("n", true)
},
/**
 * Branch if Not Equal
 *
 * If the Z flag is clear, jumps to `address`.
 */
{
  id: "BNE",
  execute: B__("z", false)
},
/**
 * Branch if Positive
 *
 * If the N flag is clear, jumps to `address`.
 */
{
  id: "BPL",
  execute: B__("n", false)
},
/**
 * Branch if Overflow Clear
 *
 * If the V flag is clear, jumps to `address`.
 */
{
  id: "BVC",
  execute: B__("v", false)
},
/**
 * Branch if Overflow Set
 *
 * If the V flag is set, jumps to `address`.
 */
{
  id: "BVS",
  execute: B__("v", true)
},
/**
 * Jump
 *
 * Jumps to `address`.
 */
{
  id: "JMP",
  execute: (_ref, address) => {
    let {
      cpu
    } = _ref;
    cpu.pc.value = address;
  }
},
/**
 * Jump to Subroutine
 *
 * Pushes the current program counter (minus one) on to the stack and jumps to `address`.
 */
{
  id: "JSR",
  execute: (_ref2, address) => {
    let {
      cpu
    } = _ref2;
    cpu.stack.push2Bytes(cpu.pc.value - 1);
    cpu.pc.value = address;
  }
},
/**
 * Return from Interrupt
 *
 * Pulls the flags from the stack followed by the program counter.
 */
{
  id: "RTI",
  execute: _ref3 => {
    let {
      cpu
    } = _ref3;
    cpu.flags.load(cpu.stack.pop());
    cpu.pc.value = cpu.stack.pop2Bytes();
  }
},
/**
 * Return from Subroutine
 *
 * Pulls the program counter (plus one) from the stack.
 */
{
  id: "RTS",
  execute: _ref4 => {
    let {
      cpu
    } = _ref4;
    cpu.pc.value = cpu.stack.pop2Bytes() + 1;
  }
}];
const B__ = (flag, value) => {
  return (_ref5, address) => {
    let {
      cpu
    } = _ref5;
    if (cpu.flags[flag] === value) {
      cpu.pc.value = address;
      cpu.extraCycles++;
    } else {
      cpu.extraCycles = 0;
    }
  };
};
var _default = exports.default = instructions();