1package main
  2
  3import (
  4	"flag"
  5	"fmt"
  6)
  7
  8type chip8 struct {
  9	opcode uint16
 10	memory [4096]byte
 11
 12	// register
 13	v [16]byte
 14
 15	index uint16
 16	pc    uint16
 17
 18	gfx [64 * 32]byte
 19
 20	delayTimer byte
 21	soundTimer byte
 22
 23	stack [16]uint16
 24	sp    int
 25
 26	key [16]byte
 27
 28	drawFlag bool
 29}
 30
 31// Initialize registers and memory once
 32func (c *chip8) initialize() {
 33	c.pc = 0x200
 34	c.opcode = 0
 35	c.index = 0
 36	c.sp = 0
 37}
 38
 39func (c *chip8) emulateCycle() {
 40	// Fetch Opcode
 41	c.opcode = uint16(c.memory[c.pc])<<8 | uint16(c.memory[c.pc+1])
 42
 43	// Decode Opcode
 44	// https://en.wikipedia.org/wiki/CHIP-8#Opcode_table
 45	// http://www.multigesture.net/wp-content/uploads/mirror/goldroad/chip8_instruction_set.shtml
 46	switch c.opcode & 0xF000 {
 47	case 0x0000:
 48		switch c.opcode & 0x000F {
 49		case 0x0000: // 0x00E0
 50			// clear screen
 51			// TODO
 52			c.pc += 2
 53			break
 54		case 0x000E: // 0x00EE
 55			// TODO
 56			break
 57		default:
 58			fmt.Printf("Unknown opcode [0x0000]: 0x%X\n", c.opcode)
 59		}
 60	case 0x2000:
 61		c.stack[c.sp] = c.pc
 62		c.sp++
 63		c.pc = c.opcode & 0x0FFF
 64		break
 65	case 0x6000:
 66		pos := (c.opcode & 0x0F00) >> 8
 67		c.v[pos] = byte(c.opcode)
 68		c.pc += 2
 69		break
 70	default:
 71		fmt.Printf("Unknown opcode: 0x%X\n", c.opcode)
 72	}
 73
 74	// Update timers
 75	if c.delayTimer > 0 {
 76		c.delayTimer--
 77	}
 78	if c.soundTimer > 0 {
 79		if c.soundTimer == 1 {
 80			fmt.Printf("Beep!\n")
 81		}
 82		c.soundTimer--
 83	}
 84}
 85
 86func (c *chip8) loadGame(filepath string) error {
 87	return nil
 88}
 89
 90func (c *chip8) drawGraphics() {
 91
 92}
 93
 94func (c *chip8) setKeys() {
 95
 96}
 97
 98func main() {
 99	filepath := flag.String("file", "file-path", "file path of the input file")
100
101	flag.Parse()
102
103	// setupGraphics()
104	// setupInput()
105
106	var c chip8
107	c.initialize()
108	err := c.loadGame(*filepath)
109	if err != nil {
110		panic(err)
111	}
112
113	for {
114		c.emulateCycle()
115		if c.drawFlag {
116			c.drawGraphics()
117			c.setKeys()
118		}
119	}
120}