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use std::io::Read;
use std::io::Write;
const WIDTH: u16 = 64;
const HEIGHT: u16 = 32;
const PIXELS: usize = (WIDTH * HEIGHT) as usize;
fn unknown_opcode(opcode: u16) {
eprintln!("Unknwown opcode {:#06x}", opcode);
std::process::exit(1);
}
pub struct Chip8 {
v: [u8; 4096],
i: u16,
pc: u16,
stack: [u16; 16],
sp: u16,
memory: [u8; 4096],
screen: [u8; PIXELS],
delay_timer: u8,
sound_timer: u8,
key: [u8; 16],
draw: bool,
}
impl Chip8 {
pub fn new() -> Self {
Self {
v: [0; 4096],
i: 0,
pc: 0x200,
stack: [0; 16],
sp: 0,
memory: [0; 4096],
screen: [0; PIXELS],
delay_timer: 0,
sound_timer: 0,
key: [0; 16],
draw: false,
}
}
pub fn load_rom<R: Read>(&mut self, mut reader: R) -> std::io::Result<()> {
reader.read(&mut self.memory[0x200..])?;
Ok(())
}
pub fn cycle(&mut self) {
let pc = self.pc as usize;
let opcode = ((self.memory[pc] as u16) << 8) | self.memory[pc + 1] as u16;
let x = ((opcode & 0x0F00) >> 8) as usize;
let y = ((opcode & 0x00F0) >> 4) as usize;
let n = opcode & 0x000F;
let nn = (opcode & 0x00FF) as u8;
let nnn = opcode & 0x0FFF;
self.pc += 2;
match opcode & 0xF000 {
0x0000 => match opcode & 0x000F {
0x0000 => {
eprintln!("CLS");
self.screen = [0; PIXELS];
self.draw = true;
}
0x000E => {
eprintln!("RET");
}
_ => unknown_opcode(opcode),
},
0x1000 => {
eprintln!("JP {}", nnn);
self.pc = nnn;
}
0x3000 => {
eprintln!("SE V{}, {}", x, nn);
if self.v[x] == nn {
self.pc += 2;
}
}
0x4000 => {
eprintln!("SNE V{}, {}", x, nn);
if self.v[x] != nn {
self.pc += 2;
}
}
0x5000 => {
eprintln!("SE V{}, V{}", x, y);
if self.v[x] == self.v[y] {
self.pc += 2;
}
}
0x6000 => {
eprintln!("LD V{}, {}", x, nn);
self.v[x] = nn;
}
0x7000 => {
eprintln!("ADD V{}, {}", x, nn);
self.v[x] = self.v[x].wrapping_add(nn);
}
0x9000 => {
eprintln!("SNE V{}, V{}", x, y);
if self.v[x] != self.v[y] {
self.pc += 2;
}
}
0xA000 => {
eprintln!("LD I, {}", nnn);
self.i = nnn;
}
0xD000 => {
eprintln!("DRW V{}, V{}, {}", x, y, n);
let vx = self.v[x] as u16;
let vy = self.v[y] as u16;
self.v[0xF] = 0;
for yy in 0..n {
let pixel = self.memory[(self.i + yy) as usize];
for xx in 0..8 {
if (pixel & (0x80 >> xx)) != 0 {
let si = vx + xx + ((vy + yy) * WIDTH);
if self.screen[si as usize] == 1 {
self.v[0xF] = 1;
}
self.screen[si as usize] ^= 1;
}
}
}
self.draw = true;
}
_ => unknown_opcode(opcode),
};
if self.delay_timer > 0 {
self.delay_timer -= 1;
}
if self.sound_timer > 0 {
if self.sound_timer == 1 {
eprintln!("BEEP");
}
self.sound_timer -= 1;
}
}
pub fn display(&mut self) -> std::io::Result<()> {
if self.draw {
self.draw = false;
self.draw()
} else {
Ok(())
}
}
fn draw(&self) -> std::io::Result<()> {
let stdout = std::io::stdout();
let mut handle = stdout.lock();
handle.write_all(b"\x1B[2J\n")?;
for y in 0..HEIGHT {
for x in 0..WIDTH {
let si = x + y * WIDTH;
let buf = if self.screen[si as usize] == 0 {
"░".as_bytes()
} else {
"█".as_bytes()
};
handle.write_all(buf)?;
}
handle.write_all(b"\n")?;
}
handle.flush()
}
}
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