264 lines
6.8 KiB
Rust
264 lines
6.8 KiB
Rust
use sdl2::keyboard::Keycode;
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const MEMORY_SIZE: usize = 4096;
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const WIDTH: u32 = 64;
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const HEIGHT: u32 = 32;
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const DATA_REGISTERS: usize = 16;
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const STACK_DEPTH: usize = 16;
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const KEYS: usize = 16;
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pub const SCALE_FACTOR: u32 = 10;
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pub const WINDOW_WIDTH: u32 = WIDTH * SCALE_FACTOR;
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pub const WINDOW_HEIGHT: u32 = HEIGHT * SCALE_FACTOR;
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type Memory = [u8; MEMORY_SIZE];
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pub enum Register {
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V0,
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V1,
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V2,
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V3,
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V4,
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V5,
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V6,
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V7,
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V8,
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V9,
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VA,
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VB,
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VC,
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VD,
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VE,
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VF,
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I,
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DT,
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ST,
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PC,
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SP,
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}
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struct Registers {
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data: [u8; DATA_REGISTERS],
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i: u16,
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delay_timer: u8,
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sound_timer: u8,
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pc: u16,
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sp: u8,
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}
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type Stack = [u16; STACK_DEPTH];
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type Keyboard = [bool; KEYS];
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pub struct Chip8 {
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memory: Memory,
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registers: Registers,
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stack: Stack,
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keyboard: Keyboard,
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}
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fn data_register_to_index(register: Register) -> usize {
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match register {
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Register::V0 => 0,
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Register::V1 => 1,
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Register::V2 => 2,
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Register::V3 => 3,
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Register::V4 => 4,
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Register::V5 => 5,
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Register::V6 => 6,
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Register::V7 => 7,
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Register::V8 => 8,
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Register::V9 => 9,
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Register::VA => 10,
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Register::VB => 11,
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Register::VC => 12,
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Register::VD => 13,
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Register::VE => 14,
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Register::VF => 15,
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_ => panic!("invalid data register"),
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}
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}
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impl Chip8 {
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pub fn new() -> Chip8 {
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Chip8 {
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memory: [0; MEMORY_SIZE],
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registers: Registers {
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data: [0; DATA_REGISTERS],
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i: 0,
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delay_timer: 0,
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sound_timer: 0,
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pc: 0,
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sp: 0,
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},
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stack: [0; STACK_DEPTH],
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keyboard: [false; KEYS],
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}
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}
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pub fn memory_set(&mut self, index: usize, value: u8) -> () {
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self.memory[index] = value;
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}
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pub fn memory_get(&self, index: usize) -> u8 {
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self.memory[index]
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}
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pub fn register_set(&mut self, register: Register, value: u16) -> () {
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match register {
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Register::I => self.registers.i = value,
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Register::DT => self.registers.delay_timer = value as u8,
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Register::ST => self.registers.sound_timer = value as u8,
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Register::PC => self.registers.pc = value,
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Register::SP => self.registers.sp = value as u8,
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_ => self.registers.data[data_register_to_index(register)] = value as u8,
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}
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}
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pub fn register_get(&self, register: Register) -> u16 {
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match register {
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Register::I => self.registers.i,
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Register::DT => self.registers.delay_timer as u16,
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Register::ST => self.registers.sound_timer as u16,
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Register::PC => self.registers.pc,
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Register::SP => self.registers.sp as u16,
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_ => self.registers.data[data_register_to_index(register)] as u16,
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}
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}
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pub fn stack_push(&mut self, value: u16) -> () {
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assert!((self.registers.sp as usize) < STACK_DEPTH, "stack overflow");
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self.stack[self.registers.sp as usize] = value;
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self.registers.sp += 1;
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}
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pub fn stack_pop(&mut self) -> u16 {
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assert!(self.registers.sp > 0, "stack underflow");
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self.registers.sp -= 1;
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assert!((self.registers.sp as usize) < STACK_DEPTH, "stack overflow");
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self.stack[self.registers.sp as usize]
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}
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pub fn keyboard_map(&self, key: Keycode) -> Option<usize> {
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match key {
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Keycode::Num1 => Some(1),
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Keycode::Num2 => Some(2),
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Keycode::Num3 => Some(3),
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Keycode::Num4 => Some(12),
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Keycode::Q => Some(4),
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Keycode::W => Some(5),
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Keycode::E => Some(6),
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Keycode::R => Some(13),
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Keycode::A => Some(7),
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Keycode::S => Some(8),
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Keycode::D => Some(9),
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Keycode::F => Some(14),
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Keycode::Z => Some(10),
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Keycode::X => Some(0),
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Keycode::C => Some(11),
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Keycode::V => Some(15),
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_ => None,
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}
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}
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pub fn key_down(&mut self, key: usize) -> () {
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self.keyboard[key] = true
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}
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pub fn key_up(&mut self, key: usize) -> () {
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self.keyboard[key] = false
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}
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pub fn is_key_down(&self, key: usize) -> bool {
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self.keyboard[key]
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn it_has_the_correct_memory_size() {
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assert_eq!(Chip8::new().memory.len(), MEMORY_SIZE);
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}
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#[test]
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fn it_can_write_the_memory() {
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let mut chip8 = Chip8::new();
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chip8.memory_set(2, 42);
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assert_eq!(chip8.memory[0..3], [0, 0, 42]);
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}
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#[test]
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fn it_can_read_the_memory() {
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let mut chip8 = Chip8::new();
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chip8.memory_set(2, 42);
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assert_eq!(chip8.memory_get(2), 42);
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}
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#[test]
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fn it_has_the_correct_number_of_data_registers() {
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assert_eq!(Chip8::new().registers.data.len(), DATA_REGISTERS);
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}
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#[test]
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fn it_can_write_data_registers() {
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let mut chip8 = Chip8::new();
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chip8.register_set(Register::VA, 42);
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assert_eq!(chip8.registers.data[10], 42);
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}
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#[test]
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fn it_can_read_data_registers() {
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let mut chip8 = Chip8::new();
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chip8.register_set(Register::VA, 42);
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assert_eq!(chip8.register_get(Register::VA), 42);
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}
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#[test]
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fn it_can_write_special_registers() {
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let mut chip8 = Chip8::new();
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chip8.register_set(Register::PC, 42);
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assert_eq!(chip8.registers.pc, 42);
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}
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#[test]
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fn it_can_read_special_registers() {
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let mut chip8 = Chip8::new();
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chip8.register_set(Register::PC, 42);
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assert_eq!(chip8.register_get(Register::PC), 42);
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}
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#[test]
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fn it_can_push_to_and_pop_from_the_stack() {
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let mut chip8 = Chip8::new();
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assert_eq!(chip8.register_get(Register::SP), 0);
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chip8.stack_push(0xff);
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assert_eq!(chip8.register_get(Register::SP), 1);
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chip8.stack_push(0xaa);
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assert_eq!(chip8.register_get(Register::SP), 2);
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assert_eq!(chip8.stack_pop(), 170);
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assert_eq!(chip8.register_get(Register::SP), 1);
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assert_eq!(chip8.stack_pop(), 255);
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assert_eq!(chip8.register_get(Register::SP), 0);
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}
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#[test]
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fn it_maps_physical_keys_to_virtual_ones() {
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let mut chip8 = Chip8::new();
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assert_eq!(chip8.keyboard_map(Keycode::A), Some(7));
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assert_eq!(chip8.keyboard_map(Keycode::X), Some(0));
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assert_eq!(chip8.keyboard_map(Keycode::M), None);
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}
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#[test]
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fn it_can_press_and_release_keys() {
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let mut chip8 = Chip8::new();
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chip8.key_down(1);
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assert!(chip8.is_key_down(1));
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chip8.key_up(1);
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assert!(!chip8.is_key_down(1));
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}
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}
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