Implement CHIP-8 Opcodes

Warning: There are currently no tests and I'm pretty sure none of them
work well /shrug

Cargo.lock

@@ -1,5 +1,84 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+[[package]]
+name = "cfg-if"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
 [[package]]
 name = "chip8"
 version = "0.1.0"
+dependencies = [
+ "rand",
+]
+
+[[package]]
+name = "getrandom"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7abc8dd8451921606d809ba32e95b6111925cd2906060d2dcc29c070220503eb"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.71"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9457b06509d27052635f90d6466700c65095fdf75409b3fbdd903e988b886f49"
+
+[[package]]
+name = "ppv-lite86"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "237a5ed80e274dbc66f86bd59c1e25edc039660be53194b5fe0a482e0f2612ea"
+
+[[package]]
+name = "rand"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a6b1679d49b24bbfe0c803429aa1874472f50d9b363131f0e89fc356b544d03"
+dependencies = [
+ "getrandom",
+ "libc",
+ "rand_chacha",
+ "rand_core",
+ "rand_hc",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f4c8ed856279c9737206bf725bf36935d8666ead7aa69b52be55af369d193402"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "90bde5296fc891b0cef12a6d03ddccc162ce7b2aff54160af9338f8d40df6d19"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "rand_hc"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ca3129af7b92a17112d59ad498c6f81eaf463253766b90396d39ea7a39d6613c"
+dependencies = [
+ "rand_core",
+]
+
+[[package]]
+name = "wasi"
+version = "0.9.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"

Cargo.toml

@@ -7,3 +7,4 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+rand = "0.7.3"

src/main.rs

@@ -1,11 +1,19 @@
+// I used: http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#00E0
+// and https://en.wikipedia.org/wiki/CHIP-8#Opcode_table
+// for information about how to implement a CHIP-8 Emulator
+use std::fs::File;
+use std::io::{self, Read};
+use std::path::Path;
+use std::time::Duration;
 
 const SCREEN_SIZE: usize = 64 * 32;
 
+#[derive(Copy, Clone)]
 struct Chip8 {
     opcode: u16,
     i: u16,
     pc: u16,
-    sp: u16,
+    sp: u8,
     key: Option<u8>,
     v: [u8; 16],
     stack: [u16; 16],
@@ -15,13 +23,12 @@ struct Chip8 {
     display: Display,
 }
 
-
 impl Default for Chip8 {
     fn default() -> Self {
         Chip8 {
             opcode: 0,
             i: 0,
-            pc: 0,
+            pc: 0x200, // Progrm counter starts at 0x200
             sp: 0,
             key: None,
             v: [0; 16],
@@ -34,18 +41,31 @@ impl Default for Chip8 {
     }
 }
 
-
 impl Chip8 {
-    fn new() -> Self {
+    pub fn execute_cycle(&mut self) {
-        Default::default()
+        self.opcode = self.get_opcode();
+        println!("{:#x}", self.opcode);
+        self.handle_opcode();
+
+        self.delay.tick();
+        self.sound.tick();
     }
 
-    pub fn execute_cycle(&self) {
+    pub fn load_rom<P: AsRef<Path>>(&mut self, path: P) -> Result<(), io::Error> {
+        let mut file = File::open(path.as_ref())?;
+        let mut rom_buf: Vec<u8> = vec![];
+        file.read_to_end(&mut rom_buf)?;
 
+        for (i, byte) in rom_buf.iter().enumerate() {
+            self.memory[i + 0x200] = *byte;
+        }
+
+        Ok(())
     }
 
     fn get_opcode(&self) -> u16 {
         let pc = self.pc as usize;
+
         ((self.memory[pc] as u16) << 8) | self.memory[pc + 1] as u16
     }
 
@@ -60,25 +80,405 @@ impl Chip8 {
 
         match (nib_1, nib_2, nib_3, nib_4) {
             // CLS
-            (0x0, 0x0, 0xE, 0x0) => self.clear_display(),
+            (0x0, 0x0, 0xE, 0x0) => self.cls(),
             // 00EE
-            (0x0, 0x0, 0xE, 0xE) => {}
+            (0x0, 0x0, 0xE, 0xE) => self.ret(),
             // 1NNN
-            (0x1, _, _, _) => {}
+            (0x1, _, _, _) => self.jmp_addr(nib_2, nib_3, nib_4),
             // 2NNN
-            (0x2, _, _, _) => {}
+            (0x2, _, _, _) => self.call_addr(nib_2, nib_3, nib_4),
             // 3XKK
-            (0x3, _, _, _) => {}
+            (0x3, _, _, _) => self.se_vx_byte(nib_2, nib_3, nib_4),
-            _ => unimplemented!("UNIMPLEMENTED OPCODE: {:#x}", self.opcode)
+            // 4xkk
+            (0x4, _, _, _) => self.sne_vx_byte(nib_2, nib_3, nib_4),
+            // 5xy0
+            (0x5, _, _, 0x0) => self.se_vx_vy(nib_2, nib_3),
+            // 6xkk
+            (0x6, _, _, _) => self.ld_vx_byte(nib_2, nib_3, nib_4),
+            // 7xkk
+            (0x7, _, _, _) => self.add_vx_byte(nib_2, nib_3, nib_4),
+            // 8xy0
+            (0x8, _, _, 0x0) => self.ld_vx_vy(nib_2, nib_3),
+            // 8xy1
+            (0x8, _, _, 0x1) => self.or_vx_vy(nib_2, nib_3),
+            // 8xy2
+            (0x8, _, _, 0x2) => self.and_vx_vy(nib_2, nib_3),
+            // 8xy3
+            (0x8, _, _, 0x3) => self.xor_vx_vy(nib_2, nib_3),
+            // 8xy4
+            (0x8, _, _, 0x4) => self.add_vx_vy(nib_2, nib_3),
+            // 8xy5
+            (0x8, _, _, 0x5) => self.sub_vx_vy(nib_2, nib_3),
+            // 8xy6
+            (0x8, _, _, 0x6) => self.shr_vx(nib_2),
+            // 8xy7
+            (0x8, _, _, 0x7) => self.subn_vx_vy(nib_2, nib_3),
+            // 8xyE
+            (0x8, _, _, 0xE) => self.shl_vx(nib_2),
+            // 9xy0
+            (0x9, _, _, 0x0) => self.sne_vx_vy(nib_2, nib_3),
+            // Annn
+            (0xA, _, _, _) => self.ld_i_addr(nib_2, nib_3, nib_4),
+            // Bnnn
+            (0xB, _, _, _) => self.jmp_v0_addr(nib_2, nib_3, nib_4),
+            // Cxkk
+            (0xC, _, _, _) => self.rnd_vx_byte(nib_2, nib_3, nib_4),
+            //Dxyn
+            (0xD, _, _, _) => self.drw_vx_vy_nib(nib_2, nib_3, nib_4),
+            // Ex9E
+            (0xE, _, 0x9, 0xE) => self.skp_vx(nib_2),
+            // ExA1
+            (0xE, _, 0xA, 0x1) => self.sknp_vx(nib_2),
+            // Fx07
+            (0xF, _, 0x0, 0x7) => self.ld_vx_dt(nib_2),
+            // Fx0A
+            (0xF, _, 0x0, 0xA) => self.ld_vx_k(nib_2),
+            // Fx15
+            (0xF, _, 0x1, 0x15) => self.ld_dt_vx(nib_2),
+            // Fx18
+            (0xF, _, 0x1, 0x8) => self.ld_st_vx(nib_2),
+            // Fx1E
+            (0xF, _, 0x1, 0xE) => self.add_i_vx(nib_2),
+            // Fx29
+            (0xF, _, 0x2, 0x9) => self.ld_f_vx(nib_2),
+            // Fx33
+            (0xF, _, 0x3, 0x3) => self.ld_b_vx(nib_2),
+            // Fx55
+            (0xF, _, 0x5, 0x5) => self.ld_i_vx(nib_2),
+            // Fx65
+            (0xF, _, 0x6, 0x5) => self.ld_vx_i(nib_2),
+            // General Case
+            _ => println!("UNIMPLEMENTED OPCODE: {:#x}", self.opcode),
         }
     }
 
-    fn clear_display(&mut self) {
+    fn cls(&mut self) {
+        // Clear the display
         self.display.clear();
+        self.pc += 1;
     }
 
+    fn jmp_addr(&mut self, n_1: u16, n_2: u16, n_3: u16) {
+        // sets the program counter to addr (nnn)
+        self.pc = Self::convert_to_addr(n_1, n_2, n_3);
+        self.pc += 1;
     }
 
+    fn ret(&mut self) {
+        // sets the program counter to the addres at the top of the stack,
+        // then subtracts one (1) from the stack pointer
+        self.pc = self.stack[self.sp as usize];
+        self.sp -= 1;
+        self.pc += 1;
+    }
+
+    fn call_addr(&mut self, n_1: u16, n_2: u16, n_3: u16) {
+        // increments the stack pointer, then puts current pc on top of stack
+        // pc is then set to addr
+        self.sp += 1;
+        self.stack[self.sp as usize] = self.pc;
+        self.pc = Self::convert_to_addr(n_1, n_2, n_3);
+        self.pc += 1;
+    }
+
+    fn se_vx_byte(&mut self, x: u16, k_1: u16, k_2: u16) {
+        // compares Vx to kk. If they are equal, pc is incremented by 2
+        if self.v[x as usize] == Self::convert_to_byte(k_1, k_2) {
+            self.pc += 2;
+        } else {
+            self.pc += 1;
+        }
+    }
+
+    fn sne_vx_byte(&mut self, x: u16, k_1: u16, k_2: u16) {
+        // compares Vx to kk. If they are **not** equal, pc is incremented by 2
+        if self.v[x as usize] != Self::convert_to_byte(k_1, k_2) {
+            self.pc += 2;
+        } else {
+            self.pc += 1;
+        }
+    }
+
+    fn se_vx_vy(&mut self, x: u16, y: u16) {
+        // compares Vx to Vy. If they are equal, pc is incremented by 2
+        if self.v[x as usize] == self.v[y as usize] {
+            self.pc += 2;
+        } else {
+            self.pc += 1;
+        }
+    }
+
+    fn ld_vx_byte(&mut self, x: u16, k_1: u16, k_2: u16) {
+        // put value kk into Vx
+        self.v[x as usize] = Self::convert_to_byte(k_1, k_2);
+        self.pc += 1;
+    }
+
+    fn add_vx_byte(&mut self, x: u16, k_1: u16, k_2: u16) {
+        // calculate Vx + kk, then store it in Vx
+        let x = x as usize;
+        self.v[x] = self.v[x] + Self::convert_to_byte(k_1, k_2);
+        self.pc += 1;
+    }
+
+    fn ld_vx_vy(&mut self, x: u16, y: u16) {
+        // store Vy in Vx
+        self.v[x as usize] = self.v[y as usize];
+        self.pc += 1;
+    }
+
+    fn or_vx_vy(&mut self, x: u16, y: u16) {
+        // calc bitwise OR on Vx and Vy, then store in Vx
+        let x = x as usize;
+        self.v[x] = self.v[x] | self.v[y as usize];
+        self.pc += 1;
+    }
+
+    fn and_vx_vy(&mut self, x: u16, y: u16) {
+        // calc bitwise AND on Vx and Vy, then store in Vx
+        let x = x as usize;
+        self.v[x] = self.v[x] & self.v[y as usize];
+        self.pc += 1;
+    }
+
+    fn xor_vx_vy(&mut self, x: u16, y: u16) {
+        // calc bitwise XOR on Vx and Vy, then store in Vx
+        let x = x as usize;
+        self.v[x] = self.v[x] ^ self.v[y as usize];
+        self.pc += 1;
+    }
+
+    fn add_vx_vy(&mut self, x: u16, y: u16) {
+        // add Vx and Vy, if result is greater than 8 bits
+        // set VF to 1, otherwise 0
+        // only the lowest 8 bits of result are stored in Vx
+        let x = x as usize;
+
+        let (res, did_overflow) = self.v[x].overflowing_add(self.v[y as usize]);
+        self.v[0xF as usize] = if did_overflow { 1 } else { 0 };
+        self.v[x] = res;
+        self.pc += 1;
+    }
+
+    fn sub_vx_vy(&mut self, x: u16, y: u16) {
+        // subtract Vx and Vy, if Vx > Vy VF is set to 1, otherwise 0
+        // then set Vx to Vx - Vy
+        let vx = self.v[x as usize];
+        let vy = self.v[y as usize];
+
+        self.v[0xF as usize] = if vx > vy { 1 } else { 0 };
+        self.v[x as usize] = vx - vy;
+        self.pc += 1;
+    }
+
+    fn shr_vx(&mut self, x: u16) {
+        // if LSB is set to 1, set VF to 1, otherwise set VF to 0
+        // then shift Vx one to the right
+        let x = x as usize;
+
+        self.v[0xF as usize] = if (self.v[x] & 1) == 1 { 1 } else { 0 };
+        self.v[x] = self.v[x] >> 1;
+        self.pc += 1;
+    }
+
+    fn subn_vx_vy(&mut self, x: u16, y: u16) {
+        // subtract Vy and Vx, if Vy > Vx VF is set to 1, otherwise 0
+        // then set Vx = Vy - Vx
+        let vx = self.v[x as usize];
+        let vy = self.v[y as usize];
+
+        self.v[0xF as usize] = if vy > vx { 1 } else { 0 };
+        self.v[x as usize] = vy - vx;
+        self.pc += 1;
+    }
+
+    fn shl_vx(&mut self, x: u16) {
+        // if MSB is set to 1, set VF to 1, otherwise set VF to 0
+        // then shift Vx one to the left;
+        let x = x as usize;
+
+        self.v[0xF as usize] = if (self.v[x] & 0x80) == 1 { 1 } else { 0 };
+        self.v[x] = self.v[x] << 1;
+        self.pc += 1;
+    }
+
+    fn sne_vx_vy(&mut self, x: u16, y: u16) {
+        // if Vx != vy program counter is increased by 2
+        if self.v[x as usize] != self.v[y as usize] {
+            self.pc += 2;
+        } else {
+            self.pc += 1;
+        }
+    }
+
+    fn ld_i_addr(&mut self, n_1: u16, n_2: u16, n_3: u16) {
+        // set i to addr
+        self.i = Self::convert_to_addr(n_1, n_2, n_3);
+        self.pc += 1;
+    }
+
+    fn jmp_v0_addr(&mut self, n_1: u16, n_2: u16, n_3: u16) {
+        // set program counter to addr + V0
+        self.pc = Self::convert_to_addr(n_1, n_2, n_3) + self.v[0 as usize] as u16;
+        self.pc += 1;
+    }
+
+    fn rnd_vx_byte(&mut self, x: u16, k_1: u16, k_2: u16) {
+        // generate a random number from 0 to 255
+        // AND with the value of kk, then store in Vx
+
+        self.v[x as usize] = rand::random::<u8>() & Self::convert_to_byte(k_1, k_2);
+        self.pc += 1;
+    }
+
+    fn drw_vx_vy_nib(&mut self, x: u16, y: u16, nib: u16) {
+        // read n bytes from memory starting from self.i
+        // then display them starting at (vx, vy)
+        let i = self.i as usize;
+        let _disp_x = self.v[x as usize];
+        let _disp_y = self.v[y as usize];
+
+        // There's Probably an off-by-one error here.
+        let _sprite_buf = &self.memory[i..=(i + nib as usize)];
+        let _display_buf = self.display.buf;
+
+        todo!("Finish implementing DRW");
+    }
+
+    fn skp_vx(&mut self, x: u16) {
+        // if current key is the same as the on in Vx
+        // program counter is increased by 2
+        if let Some(key) = self.key {
+            if self.v[x as usize] == key {
+                self.pc += 2;
+            } else {
+                self.pc += 1;
+            }
+        } else {
+            self.pc += 1;
+        }
+    }
+
+    fn sknp_vx(&mut self, x: u16) {
+        // if current key is not the sameas the one in Vx
+        // increment the program counter by 2
+        match self.key {
+            Some(key) => {
+                if key != self.v[x as usize] {
+                    self.pc += 2;
+                } else {
+                    self.pc += 1;
+                }
+            }
+            None => self.pc += 2,
+        }
+    }
+
+    fn ld_vx_dt(&mut self, x: u16) {
+        // set Vx to be the value of the delay timer
+        self.v[x as usize] = self.delay.get();
+        self.pc += 1;
+    }
+
+    fn ld_vx_k(&mut self, x: u16) {
+        // wait (blocking) until a key is pressed
+        // once pressed, store in Vx
+        loop {
+            if let Some(key) = self.key {
+                self.v[x as usize] = key;
+                break;
+            }
+        }
+        self.pc += 1;
+    }
+
+    fn ld_dt_vx(&mut self, x: u16) {
+        // set delay timer to be value of Vx
+        self.delay.set(self.v[x as usize]);
+        self.pc += 1;
+    }
+
+    fn ld_st_vx(&mut self, x: u16) {
+        // set sound timer to be value of Vx
+        self.delay.set(self.v[x as usize]);
+        self.pc += 1;
+    }
+
+    fn add_i_vx(&mut self, x: u16) {
+        // set I to be I + Vx
+        self.i = self.i + self.v[x as usize] as u16;
+        self.pc += 1;
+    }
+
+    fn ld_f_vx(&mut self, _x: u16) {
+        todo!("Implement 0xF_29");
+    }
+
+    fn ld_b_vx(&mut self, x: u16) {
+        // take hundreds digit and place it at I
+        // take tens digit and place it at I + 1
+        // take ones digit and place it at I + 2
+        let i = self.i as usize;
+        let mut iter = Self::digits(self.v[x as usize]);
+
+        let ones = iter.next().unwrap(); // Ther has to at least be a ones lol
+        let tens = iter.next().unwrap_or(0);
+        let hundreds = iter.next().unwrap_or(0);
+
+        self.memory[i] = hundreds;
+        self.memory[i + 1] = tens;
+        self.memory[i + 2] = ones;
+        self.pc += 1;
+    }
+
+    fn ld_i_vx(&mut self, x: u16) {
+        // copy values v0 -> Vx to memory starting at i
+
+        for n in 0..=(x as usize) {
+            self.memory[self.i as usize + n] = self.v[n];
+        }
+        self.pc += 1;
+    }
+
+    fn ld_vx_i(&mut self, x: u16) {
+        // read what will be values of v0 -> vx from memory starting at i
+        let x = x as usize;
+
+        for n in 0..=x {
+            self.v[n] = self.memory[self.i as usize + n];
+        }
+        self.pc += 1;
+    }
+
+    fn convert_to_byte(k_1: u16, k_2: u16) -> u8 {
+        ((k_1 as u8) << 4) | (k_2 as u8)
+    }
+
+    fn convert_to_addr(n_1: u16, n_2: u16, n_3: u16) -> u16 {
+        (n_1 << 8) | (n_2 << 4) | n_3
+    }
+
+    // https://stackoverflow.com/questions/41536479/how-do-i-split-an-integer-into-individual-digits
+    fn digits(mut num: u8) -> impl Iterator<Item = u8> {
+        let mut divisor = 1;
+        while num >= divisor * 10 {
+            divisor *= 10;
+        }
+
+        std::iter::from_fn(move || {
+            if divisor == 0 {
+                None
+            } else {
+                let v = num / divisor;
+                num %= divisor;
+                divisor /= 10;
+                Some(v)
+            }
+        })
+    }
+}
+
+#[derive(Copy, Clone)]
 struct Display {
     buf: [u8; SCREEN_SIZE],
 }
@@ -97,18 +497,87 @@ impl Default for Display {
     }
 }
 
+#[derive(Debug, Copy, Clone)]
 struct Timer {
-    value: u8,
+    remaining: u8,
+    enabled: bool,
 }
 
 impl Default for Timer {
     fn default() -> Self {
         Timer {
-            value: 0,
+            remaining: 0,
+            enabled: false,
+        }
+    }
+}
+
+impl Timer {
+    pub fn set(&mut self, secs: u8) {
+        self.remaining = secs;
+        self.enabled = true;
+    }
+
+    pub fn get(&self) -> u8 {
+        self.remaining
+    }
+
+    pub fn tick(&mut self) {
+        if self.enabled {
+            self.remaining -= 1;
+
+            if self.remaining == 0 {
+                println!("Beep!");
+                self.enabled = false;
+            }
+        }
+    }
+}
+
+/// Remember that the digits are yielded in the oposite order
+#[derive(Debug, Copy, Clone)]
+pub struct Digits {
+    num: u8,
+    flag: bool,
+}
+
+impl From<u8> for Digits {
+    fn from(num: u8) -> Self {
+        Digits { num, flag: true }
+    }
+}
+
+impl Iterator for Digits {
+    type Item = u8;
+
+    fn next(&mut self) -> Option<u8> {
+        if self.num >= 10 {
+            // There is something next
+            let tmp = self.num;
+            self.num = self.num / 10;
+
+            Some(tmp % 10)
+        } else {
+            if self.flag {
+                self.flag = false;
+                Some(self.num % 10)
+            } else {
+                None
+            }
         }
     }
 }
 
 fn main() {
-    println!("Chip8 Emulator");
+    let mut chip8: Chip8 = Default::default();
+
+    chip8
+        .load_rom(Path::new("C:\\Users\\paoda\\Documents\\chip8_roms\\TICTAC"))
+        .expect("Unable to load ROM");
+
+    loop {
+        chip8.execute_cycle();
+
+        std::thread::sleep(Duration::from_millis(1000));
+    }
 }