chore: satisfy clippy

Implemented for MBC1, MBC2, MBC3 and MBC5

Cargo.lock

@@ -592,6 +592,27 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "directories-next"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "339ee130d97a610ea5a5872d2bbb130fdf68884ff09d3028b81bec8a1ac23bbc"
+dependencies = [
+ "cfg-if 1.0.0",
+ "dirs-sys-next",
+]
+
+[[package]]
+name = "dirs-sys-next"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ebda144c4fe02d1f7ea1a7d9641b6fc6b580adcfa024ae48797ecdeb6825b4d"
+dependencies = [
+ "libc",
+ "redox_users",
+ "winapi",
+]
+
 [[package]]
 name = "discard"
 version = "1.0.4"
@@ -671,6 +692,7 @@ dependencies = [
  "anyhow",
  "bitfield",
  "clap",
+ "directories-next",
  "gilrs",
  "pixels",
  "rodio",
@@ -679,6 +701,17 @@ dependencies = [
  "winit_input_helper",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fcd999463524c52659517fe2cea98493cfe485d10565e7b0fb07dbba7ad2753"
+dependencies = [
+ "cfg-if 1.0.0",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "gilrs"
 version = "0.8.1"
@@ -1493,6 +1526,16 @@ dependencies = [
  "bitflags",
 ]
 
+[[package]]
+name = "redox_users"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "528532f3d801c87aec9def2add9ca802fe569e44a544afe633765267840abe64"
+dependencies = [
+ "getrandom",
+ "redox_syscall",
+]
+
 [[package]]
 name = "regex"
 version = "1.5.4"
@@ -1916,6 +1959,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.10.2+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6"
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.77"

Cargo.toml

@@ -17,6 +17,7 @@ winit = "^0.25"
 winit_input_helper = "^0.10"
 rodio = "^0.14"
 rtrb = "^0.1.4"
+directories-next = "2.0.0"
 
 [profile.release]
 debug = true

src/bus.rs

@@ -7,14 +7,13 @@ use crate::ppu::{Ppu, PpuMode};
 use crate::serial::Serial;
 use crate::timer::Timer;
 use crate::work_ram::{VariableWorkRam, WorkRam};
-use std::{fs::File, io::Read};
 
-const BOOT_ROM_SIZE: usize = 0x100;
+pub(crate) const BOOT_SIZE: usize = 0x100;
 
 #[derive(Debug)]
 pub struct Bus {
-    boot: Option<[u8; BOOT_ROM_SIZE]>, // Boot ROM is 256b long
-    cartridge: Option<Cartridge>,
+    boot: Option<[u8; BOOT_SIZE]>, // Boot ROM is 256b long
+    cart: Option<Cartridge>,
     pub(crate) ppu: Ppu,
     work_ram: WorkRam,
     var_ram: VariableWorkRam,
@@ -30,7 +29,7 @@ impl Default for Bus {
     fn default() -> Self {
         Self {
             boot: None,
-            cartridge: None,
+            cart: None,
             ppu: Default::default(),
             work_ram: Default::default(),
             var_ram: Default::default(),
@@ -45,25 +44,19 @@ impl Default for Bus {
 }
 
 impl Bus {
-    pub(crate) fn with_boot(path: &str) -> anyhow::Result<Self> {
-        let mut file = File::open(path)?;
-        let mut boot_rom = [0u8; 256];
-
-        file.read_exact(&mut boot_rom)?;
-
-        Ok(Self {
-            boot: Some(boot_rom),
+    pub(crate) fn with_boot(rom: [u8; 256]) -> Self {
+        Self {
+            boot: Some(rom),
             ..Default::default()
-        })
+        }
     }
 
-    pub(crate) fn load_cartridge(&mut self, path: &str) -> std::io::Result<()> {
-        self.cartridge = Some(Cartridge::new(path)?);
-        Ok(())
+    pub(crate) fn load_cart(&mut self, rom: Vec<u8>) {
+        self.cart = Some(Cartridge::new(rom));
     }
 
-    pub(crate) fn rom_title(&self) -> Option<&str> {
-        self.cartridge.as_ref()?.title()
+    pub(crate) fn cart_title(&self) -> Option<&str> {
+        self.cart.as_ref()?.title()
     }
 
     #[allow(dead_code)]
@@ -71,10 +64,12 @@ impl Bus {
         self.boot.is_some()
     }
 
+    #[inline]
     pub(crate) fn clock(&mut self) {
         self.tick(4);
     }
 
+    #[inline]
     fn tick(&mut self, limit: u8) {
         for _ in 0..limit {
             self.timer.tick();
@@ -90,6 +85,21 @@ impl Bus {
             self.oam_write_byte(dest_addr, byte);
         }
     }
+
+    #[inline]
+    pub(crate) fn joyp_mut(&mut self) -> &mut Joypad {
+        &mut self.joypad
+    }
+
+    #[inline]
+    pub(crate) fn cart(&self) -> Option<&Cartridge> {
+        self.cart.as_ref()
+    }
+
+    #[inline]
+    pub(crate) fn cart_mut(&mut self) -> Option<&mut Cartridge> {
+        self.cart.as_mut()
+    }
 }
 
 impl Bus {
@@ -104,13 +114,13 @@ impl Bus {
                     }
                 }
 
-                match self.cartridge.as_ref() {
+                match self.cart.as_ref() {
                     Some(cart) => cart.read_byte(addr),
                     None => panic!("Tried to read from a non-existent cartridge"),
                 }
             }
             0x8000..=0x9FFF => self.ppu.read_byte(addr), // 8KB Video RAM
-            0xA000..=0xBFFF => match self.cartridge.as_ref() {
+            0xA000..=0xBFFF => match self.cart.as_ref() {
                 // 8KB External RAM
                 Some(cart) => cart.read_byte(addr),
                 None => panic!("Tried to read from a non-existent cartridge"),
@@ -157,7 +167,7 @@ impl BusIo for Bus {
                     }
                 }
 
-                match self.cartridge.as_ref() {
+                match self.cart.as_ref() {
                     Some(cart) => cart.read_byte(addr),
                     None => panic!("Tried to read from a non-existent cartridge"),
                 }
@@ -169,7 +179,7 @@ impl BusIo for Bus {
                     _ => self.ppu.read_byte(addr),
                 }
             }
-            0xA000..=0xBFFF => match self.cartridge.as_ref() {
+            0xA000..=0xBFFF => match self.cart.as_ref() {
                 // 8KB External RAM
                 Some(cart) => cart.read_byte(addr),
                 None => panic!("Tried to read from a non-existent cartridge"),
@@ -262,7 +272,7 @@ impl BusIo for Bus {
             0x0000..=0x7FFF => {
                 // 16KB ROM bank 00 (ends at 0x3FFF)
                 // and 16KB ROM Bank 01 -> NN (switchable via MB)
-                match self.cartridge.as_mut() {
+                match self.cart.as_mut() {
                     Some(cart) => cart.write_byte(addr, byte),
                     None => panic!("Tried to write into non-existent cartridge"),
                 }
@@ -276,7 +286,7 @@ impl BusIo for Bus {
             }
             0xA000..=0xBFFF => {
                 // 8KB External RAM
-                match self.cartridge.as_mut() {
+                match self.cart.as_mut() {
                     Some(cart) => cart.write_byte(addr, byte),
                     None => panic!("Tried to write into non-existent cartridge"),
                 }

src/cartridge.rs

@@ -1,7 +1,3 @@
-use std::fs::File;
-use std::io::{self, Read};
-use std::path::Path;
-
 use crate::bus::BusIo;
 
 const RAM_SIZE_ADDRESS: usize = 0x0149;
@@ -17,19 +13,23 @@ pub(crate) struct Cartridge {
 }
 
 impl Cartridge {
-    pub(crate) fn new<P: AsRef<Path> + ?Sized>(path: &P) -> io::Result<Self> {
-        let mut memory = vec![];
-        let mut rom = File::open(path)?;
-        rom.read_to_end(&mut memory)?;
-
+    pub(crate) fn new(memory: Vec<u8>) -> Self {
         let title = Self::find_title(&memory);
         eprintln!("Cartridge Title: {:?}", title);
 
-        Ok(Self {
+        Self {
             mbc: Self::detect_mbc(&memory),
             title,
             memory,
-        })
+        }
+    }
+
+    pub(crate) fn ext_ram(&self) -> Option<&[u8]> {
+        self.mbc.ext_ram()
+    }
+
+    pub(crate) fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        self.mbc.write_ext_ram(memory)
     }
 
     fn detect_mbc(memory: &[u8]) -> Box<dyn MBCIo> {
@@ -46,13 +46,13 @@ impl Cartridge {
         match mbc_kind {
             MBCKind::None => Box::new(NoMBC),
             MBCKind::MBC1 => Box::new(MBC1::new(ram_size, rom_size)),
-            MBCKind::MBC1WithBattery => Box::new(MBC1::new(ram_size, rom_size)), // TODO: Implement Saving
+            MBCKind::MBC1WithBattery => Box::new(MBC1::with_battery(ram_size, rom_size)), // TODO: Implement Saving
             MBCKind::MBC2 => Box::new(MBC2::new(rom_cap)),
-            MBCKind::MBC2WithBattery => Box::new(MBC2::new(rom_cap)), // TODO: Implement Saving
+            MBCKind::MBC2WithBattery => Box::new(MBC2::with_battery(rom_cap)), // TODO: Implement Saving
             MBCKind::MBC3 => Box::new(MBC3::new(ram_cap)),
-            MBCKind::MBC3WithBattery => Box::new(MBC3::new(ram_cap)), // TODO: Implement Saving
+            MBCKind::MBC3WithBattery => Box::new(MBC3::with_battery(ram_cap)), // TODO: Implement Saving
             MBCKind::MBC5 => Box::new(MBC5::new(ram_cap, rom_cap)),
-            MBCKind::MBC5WithBattery => Box::new(MBC5::new(ram_cap, rom_cap)), // TDO: Implement Saving
+            MBCKind::MBC5WithBattery => Box::new(MBC5::with_battery(ram_cap, rom_cap)), // TDO: Implement Saving
         }
     }
 
@@ -125,6 +125,8 @@ struct MBC1 {
     memory: Vec<u8>,
     rom_size: RomSize,
     mem_enabled: bool,
+
+    has_battery: bool,
 }
 
 impl MBC1 {
@@ -137,6 +139,20 @@ impl MBC1 {
             ram_bank: Default::default(),
             mode: Default::default(),
             mem_enabled: Default::default(),
+            has_battery: Default::default(),
+        }
+    }
+
+    fn with_battery(ram_size: RamSize, rom_size: RomSize) -> Self {
+        Self {
+            rom_bank: 0x01,
+            memory: vec![0; ram_size.capacity() as usize],
+            ram_size,
+            rom_size,
+            ram_bank: Default::default(),
+            mode: Default::default(),
+            mem_enabled: Default::default(),
+            has_battery: true,
         }
     }
 
@@ -205,6 +221,21 @@ impl MBC1 {
     }
 }
 
+impl Savable for MBC1 {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        match self.has_battery {
+            true => Some(&self.memory),
+            false => None,
+        }
+    }
+
+    fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        if self.has_battery {
+            self.memory.copy_from_slice(&memory);
+        }
+    }
+}
+
 impl MBCIo for MBC1 {
     fn handle_read(&self, addr: u16) -> MBCResult {
         use MBCResult::*;
@@ -264,6 +295,8 @@ struct MBC3 {
 
     // RTC Data Latch Previous Write
     prev_latch_write: Option<u8>,
+
+    has_battery: bool,
 }
 
 impl MBC3 {
@@ -275,6 +308,34 @@ impl MBC3 {
             devs_enabled: Default::default(),
             mapped: Default::default(),
             prev_latch_write: Default::default(),
+            has_battery: Default::default(),
+        }
+    }
+
+    fn with_battery(ram_cap: usize) -> Self {
+        Self {
+            memory: vec![0; ram_cap],
+            rom_bank: Default::default(),
+            ram_bank: Default::default(),
+            devs_enabled: Default::default(),
+            mapped: Default::default(),
+            prev_latch_write: Default::default(),
+            has_battery: true,
+        }
+    }
+}
+
+impl Savable for MBC3 {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        match self.has_battery {
+            true => Some(&self.memory),
+            false => None,
+        }
+    }
+
+    fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        if self.has_battery {
+            self.memory.copy_from_slice(&memory);
         }
     }
 }
@@ -350,9 +411,10 @@ struct MBC5 {
     ram_bank: u8,
 
     rom_cap: usize,
-
     memory: Vec<u8>,
     mem_enabled: bool,
+
+    has_battery: bool,
 }
 
 impl MBC5 {
@@ -363,6 +425,18 @@ impl MBC5 {
             rom_cap,
             ram_bank: Default::default(),
             mem_enabled: Default::default(),
+            has_battery: Default::default(),
+        }
+    }
+
+    fn with_battery(ram_cap: usize, rom_cap: usize) -> Self {
+        Self {
+            rom_bank: 0x01,
+            memory: vec![0; ram_cap],
+            rom_cap,
+            ram_bank: Default::default(),
+            mem_enabled: Default::default(),
+            has_battery: true,
         }
     }
 
@@ -371,6 +445,21 @@ impl MBC5 {
     }
 }
 
+impl Savable for MBC5 {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        match self.has_battery {
+            true => Some(&self.memory),
+            false => None,
+        }
+    }
+
+    fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        if self.has_battery {
+            self.memory.copy_from_slice(&memory);
+        }
+    }
+}
+
 impl MBCIo for MBC5 {
     fn handle_read(&self, addr: u16) -> MBCResult {
         use MBCResult::*;
@@ -409,6 +498,7 @@ struct MBC2 {
     mem_enabled: bool,
 
     rom_cap: usize,
+    has_battery: bool,
 }
 
 impl MBC2 {
@@ -418,8 +508,19 @@ impl MBC2 {
         Self {
             rom_bank: 0x01,
             memory: Box::new([0; Self::RAM_SIZE]),
-            mem_enabled: Default::default(),
             rom_cap,
+            mem_enabled: Default::default(),
+            has_battery: Default::default(),
+        }
+    }
+
+    fn with_battery(rom_cap: usize) -> Self {
+        Self {
+            rom_bank: 0x01,
+            memory: Box::new([0; Self::RAM_SIZE]),
+            rom_cap,
+            mem_enabled: Default::default(),
+            has_battery: true,
         }
     }
 
@@ -428,6 +529,21 @@ impl MBC2 {
     }
 }
 
+impl Savable for MBC2 {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        match self.has_battery {
+            true => Some(self.memory.as_ref()),
+            false => None,
+        }
+    }
+
+    fn write_ext_ram(&mut self, memory: Vec<u8>) {
+        if self.has_battery {
+            self.memory.copy_from_slice(&memory);
+        }
+    }
+}
+
 impl MBCIo for MBC2 {
     fn handle_read(&self, addr: u16) -> MBCResult {
         use MBCResult::*;
@@ -465,6 +581,16 @@ impl MBCIo for MBC2 {
 #[derive(Debug)]
 struct NoMBC;
 
+impl Savable for NoMBC {
+    fn ext_ram(&self) -> Option<&[u8]> {
+        None
+    }
+
+    fn write_ext_ram(&mut self, _memory: Vec<u8>) {
+        // Nothing Happens Here
+    }
+}
+
 impl MBCIo for NoMBC {
     fn handle_read(&self, addr: u16) -> MBCResult {
         MBCResult::Address(addr as usize)
@@ -475,7 +601,7 @@ impl MBCIo for NoMBC {
     }
 }
 
-trait MBCIo {
+trait MBCIo: Savable {
     fn handle_read(&self, addr: u16) -> MBCResult;
     fn handle_write(&mut self, addr: u16, byte: u8);
 }
@@ -615,3 +741,8 @@ impl Default for Box<dyn MBCIo> {
         Box::new(NoMBC)
     }
 }
+
+trait Savable {
+    fn ext_ram(&self) -> Option<&[u8]>;
+    fn write_ext_ram(&mut self, memory: Vec<u8>);
+}

src/cpu.rs

@@ -1,9 +1,6 @@
-use crate::apu::Apu;
-use crate::bus::{Bus, BusIo};
+use crate::bus::{Bus, BusIo, BOOT_SIZE};
 use crate::instruction::Instruction;
 use crate::interrupt::{InterruptEnable, InterruptFlag};
-use crate::joypad::Joypad;
-use crate::ppu::Ppu;
 use crate::Cycle;
 use bitfield::bitfield;
 use std::fmt::{Display, Formatter, Result as FmtResult};
@@ -18,7 +15,7 @@ pub struct Cpu {
 }
 
 impl Cpu {
-    pub fn new() -> Self {
+    pub(crate) fn without_boot() -> Self {
         Self {
             reg: Registers {
                 a: 0x01,
@@ -36,11 +33,11 @@ impl Cpu {
         }
     }
 
-    pub fn boot_new(path: &str) -> anyhow::Result<Self> {
-        Ok(Self {
-            bus: Bus::with_boot(path)?,
+    pub(crate) fn with_boot(rom: [u8; BOOT_SIZE]) -> Self {
+        Self {
+            bus: Bus::with_boot(rom),
             ..Default::default()
-        })
+        }
     }
 
     pub(crate) fn ime(&self) -> ImeState {
@@ -60,10 +57,7 @@ impl Cpu {
     }
 
     pub(crate) fn is_halted(&self) -> bool {
-        match self.state {
-            State::Halt(_) => true,
-            _ => false,
-        }
+        matches!(self.state, State::Halt(_))
     }
 
     pub(crate) fn halt_kind(&self) -> Option<HaltKind> {
@@ -72,14 +66,6 @@ impl Cpu {
             _ => None,
         }
     }
-
-    pub fn load_cartridge(&mut self, path: &str) -> std::io::Result<()> {
-        self.bus.load_cartridge(path)
-    }
-
-    pub fn rom_title(&self) -> Option<&str> {
-        self.bus.rom_title()
-    }
 }
 
 impl Cpu {
@@ -167,16 +153,14 @@ impl BusIo for Cpu {
 }
 
 impl Cpu {
-    pub fn ppu(&mut self) -> &Ppu {
-        &self.bus.ppu
+    #[inline]
+    pub(crate) fn bus(&self) -> &Bus {
+        &self.bus
     }
 
-    pub fn apu_mut(&mut self) -> &mut Apu {
-        &mut self.bus.apu
-    }
-
-    pub(crate) fn joypad_mut(&mut self) -> &mut Joypad {
-        &mut self.bus.joypad
+    #[inline]
+    pub(crate) fn bus_mut(&mut self) -> &mut Bus {
+        &mut self.bus
     }
 
     fn handle_ei(&mut self) {

src/emu.rs

@@ -1,9 +1,12 @@
-use crate::cpu::Cpu as SM83;
-use crate::joypad;
-use crate::ppu::Ppu;
-use crate::Cycle;
-use anyhow::Result;
+use crate::apu::gen::SampleProducer;
+use crate::cpu::Cpu;
+use crate::joypad::{self, Joypad};
+use crate::{Cycle, GB_HEIGHT, GB_WIDTH};
+use clap::crate_name;
 use gilrs::Gilrs;
+use std::fs::File;
+use std::io::{Read, Write};
+use std::path::PathBuf;
 use std::time::Duration;
 use winit_input_helper::WinitInputHelper;
 
@@ -12,56 +15,159 @@ pub const CYCLES_IN_FRAME: Cycle = 456 * 154; // 456 Cycles times 154 scanlines
 pub(crate) const SM83_CLOCK_SPEED: u64 = 0x40_0000; // Hz which is 4.194304Mhz
 const DEFAULT_TITLE: &str = "DMG-01 Emulator";
 
-pub fn init(boot_path: Option<&str>, rom_path: &str) -> Result<SM83> {
-    let mut cpu = match boot_path {
-        Some(path) => SM83::boot_new(path)?,
-        None => SM83::new(),
-    };
-
-    eprintln!("Initialized GB Emulator");
-
-    cpu.load_cartridge(rom_path)?;
-    Ok(cpu)
-}
-
-pub fn rom_title(game_boy: &SM83) -> &str {
-    game_boy.rom_title().unwrap_or(DEFAULT_TITLE)
-}
-
-pub fn run(
-    game_boy: &mut SM83,
-    gamepad: &mut Gilrs,
-    input: &WinitInputHelper,
-    target: Cycle,
-) -> Cycle {
+pub fn run_frame(emu: &mut Emulator, gamepad: &mut Gilrs, key: &WinitInputHelper) -> Cycle {
     let mut elapsed = 0;
 
     if let Some(event) = gamepad.next_event() {
-        joypad::handle_gamepad_input(game_boy.joypad_mut(), event);
+        joypad::handle_gamepad_input(emu.joyp_mut(), event);
     }
-    joypad::handle_keyboard_input(game_boy.joypad_mut(), input);
+    joypad::handle_keyboard_input(emu.joyp_mut(), key);
 
-    while elapsed < target {
-        elapsed += game_boy.step();
-    }
-
-    elapsed
-}
-
-pub fn run_frame(game_boy: &mut SM83, gamepad: &mut Gilrs, input: &WinitInputHelper) -> Cycle {
-    let mut elapsed = 0;
-
-    if let Some(event) = gamepad.next_event() {
-        joypad::handle_gamepad_input(game_boy.joypad_mut(), event);
-    }
-    joypad::handle_keyboard_input(game_boy.joypad_mut(), input);
     while elapsed < CYCLES_IN_FRAME {
-        elapsed += game_boy.step();
+        elapsed += emu.step();
     }
 
     elapsed
 }
 
-pub fn draw(ppu: &Ppu, frame: &mut [u8]) {
-    ppu.copy_to_gui(frame);
+pub fn draw_frame(emu: &Emulator, buf: &mut [u8; GB_HEIGHT * GB_WIDTH * 4]) {
+    buf.copy_from_slice(emu.cpu.bus().ppu.frame_buf());
+}
+
+pub struct Emulator {
+    cpu: Cpu,
+    timestamp: Cycle,
+}
+
+impl Emulator {
+    fn new(cpu: Cpu) -> Self {
+        Self {
+            cpu,
+            timestamp: Default::default(),
+        }
+    }
+
+    fn step(&mut self) -> Cycle {
+        let cycles = self.cpu.step();
+        self.timestamp += cycles;
+        cycles
+    }
+
+    fn load_cart(&mut self, rom: Vec<u8>) {
+        self.cpu.bus_mut().load_cart(rom);
+    }
+
+    #[inline]
+    fn joyp_mut(&mut self) -> &mut Joypad {
+        self.cpu.bus_mut().joyp_mut()
+    }
+
+    pub fn set_prod(&mut self, prod: SampleProducer<f32>) {
+        self.cpu.bus_mut().apu.attach_producer(prod)
+    }
+
+    pub fn title(&self) -> &str {
+        self.cpu.bus().cart_title().unwrap_or(DEFAULT_TITLE)
+    }
+
+    pub fn try_write_sav(&self) -> std::io::Result<()> {
+        if let Some(ext_ram) = self.cpu.bus().cart().map(|c| c.ext_ram()).flatten() {
+            if let Some(title) = self.cpu.bus().cart_title() {
+                let mut save_path = Self::data_path().unwrap_or_else(|| PathBuf::from("."));
+                save_path.push(title);
+                save_path.set_extension("sav");
+
+                let mut file = File::create(save_path)?;
+                file.write_all(ext_ram)?;
+            }
+        }
+
+        Ok(())
+    }
+
+    pub fn try_load_sav(&mut self) -> std::io::Result<()> {
+        if let Some(cart) = self.cpu.bus_mut().cart_mut() {
+            if let Some(title) = cart.title() {
+                let mut save_path = Self::data_path().unwrap_or_else(|| PathBuf::from("."));
+                save_path.push(title);
+                save_path.set_extension("sav");
+
+                if let Ok(mut file) = File::open(save_path) {
+                    let mut memory = Vec::new();
+                    file.read_to_end(&mut memory)?;
+
+                    cart.write_ext_ram(memory);
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    fn data_path() -> Option<PathBuf> {
+        match directories_next::ProjectDirs::from("dev", "musuka", crate_name!()) {
+            Some(dirs) => {
+                let data_local = dirs.data_local_dir();
+                std::fs::create_dir_all(data_local).ok()?;
+                Some(data_local.to_path_buf())
+            }
+            None => None,
+        }
+    }
+}
+
+pub mod build {
+    use std::fs::File;
+    use std::io::{Read, Result};
+    use std::path::Path;
+
+    use crate::bus::BOOT_SIZE;
+    use crate::cpu::Cpu;
+
+    use super::Emulator;
+
+    #[derive(Debug, Default)]
+    pub struct EmulatorBuilder {
+        boot: Option<[u8; BOOT_SIZE]>,
+        cart: Option<Vec<u8>>,
+    }
+
+    impl EmulatorBuilder {
+        pub fn new() -> Self {
+            Default::default()
+        }
+
+        pub fn with_boot<P: AsRef<Path>>(mut self, path: P) -> Result<Self> {
+            let mut file = File::open(path.as_ref())?;
+
+            let mut buf = [0x00; BOOT_SIZE];
+            file.read_exact(&mut buf)?;
+
+            self.boot = Some(buf);
+            Ok(self)
+        }
+
+        pub fn with_cart<P: AsRef<Path>>(mut self, path: P) -> Result<Self> {
+            let mut file = File::open(path.as_ref())?;
+
+            let mut buf = Vec::new();
+            file.read_to_end(&mut buf)?;
+
+            self.cart = Some(buf);
+            Ok(self)
+        }
+
+        pub fn finish(mut self) -> Emulator {
+            let mut emu = Emulator::new(match self.boot {
+                Some(rom) => Cpu::with_boot(rom),
+                None => Cpu::without_boot(),
+            });
+
+            if let Some(rom) = self.cart.take() {
+                emu.load_cart(rom)
+            }
+
+            emu
+        }
+    }
 }

src/joypad.rs

@@ -110,6 +110,7 @@ impl ButtonEvent {
     }
 }
 
+#[inline]
 pub fn handle_keyboard_input(pad: &mut Joypad, input: &WinitInputHelper) {
     use winit::event::VirtualKeyCode;
 
@@ -146,17 +147,17 @@ pub fn handle_keyboard_input(pad: &mut Joypad, input: &WinitInputHelper) {
         state.dpad_right.update(false, irq);
     }
 
-    if input.key_pressed(VirtualKeyCode::T) {
+    if input.key_pressed(VirtualKeyCode::Return) {
         state.start.update(true, irq);
     }
-    if input.key_released(VirtualKeyCode::T) {
+    if input.key_released(VirtualKeyCode::Return) {
         state.start.update(false, irq);
     }
 
-    if input.key_pressed(VirtualKeyCode::Y) {
+    if input.key_pressed(VirtualKeyCode::RShift) {
         state.select.update(true, irq);
     }
-    if input.key_released(VirtualKeyCode::Y) {
+    if input.key_released(VirtualKeyCode::RShift) {
         state.select.update(false, irq);
     }
 
@@ -175,6 +176,7 @@ pub fn handle_keyboard_input(pad: &mut Joypad, input: &WinitInputHelper) {
     }
 }
 
+#[inline]
 pub fn handle_gamepad_input(pad: &mut Joypad, event: GamepadEvent) {
     use Button::*;
     use GamepadEventType::*;

src/main.rs

@@ -1,5 +1,8 @@
+use std::convert::TryInto;
+
 use anyhow::{anyhow, Result};
 use clap::{crate_authors, crate_description, crate_name, crate_version, App, Arg};
+use gb::emu::build::EmulatorBuilder;
 use gb::{AudioSPSC, Cycle, GB_HEIGHT, GB_WIDTH};
 use gilrs::Gilrs;
 use pixels::{PixelsBuilder, SurfaceTexture};
@@ -11,7 +14,7 @@ use winit::window::{Window, WindowBuilder};
 use winit_input_helper::WinitInputHelper;
 
 const WINDOW_SCALE: usize = 3;
-const AUDIO_ENABLED: bool = false;
+const AUDIO_ENABLED: bool = true;
 
 fn main() -> Result<()> {
     let app = App::new(crate_name!())
@@ -38,13 +41,18 @@ fn main() -> Result<()> {
         )
         .get_matches();
 
-    let rom_path = m
-        .value_of("rom")
-        .expect("Required value 'rom' was provided");
+    let mut emu_build =
+        EmulatorBuilder::new().with_cart(m.value_of("rom").expect("ROM path provided"))?;
 
-    let mut game_boy =
-        gb::emu::init(m.value_of("boot"), rom_path).expect("Initialize DMG-01 Emulator");
-    let rom_title = gb::emu::rom_title(&game_boy);
+    if let Some(path) = m.value_of("boot") {
+        emu_build = emu_build.with_boot(path)?;
+    }
+
+    let mut emu = emu_build.finish();
+
+    // Load Save file if it exists
+    emu.try_load_sav().expect("Load save if exists");
+    let rom_title = emu.title();
 
     let mut gamepad = Gilrs::new().expect("Initialize Controller Support");
 
@@ -68,10 +76,14 @@ fn main() -> Result<()> {
     if AUDIO_ENABLED {
         let spsc: AudioSPSC<f32> = Default::default();
         let (prod, cons) = spsc.init();
-        let sink = Sink::try_new(&stream_handle)?;
-        sink.append(cons);
-        sink.set_volume(0.1); // TODO: Is this the right way to go about this?
-        game_boy.apu_mut().attach_producer(prod);
+        let sink = {
+            let s = Sink::try_new(&stream_handle)?;
+            s.append(cons);
+            s.set_volume(0.1);
+            s
+        };
+
+        emu.set_prod(prod);
 
         std::thread::spawn(move || {
             sink.sleep_until_end();
@@ -87,6 +99,8 @@ fn main() -> Result<()> {
                 .map_err(|e| anyhow!("pixels.render() failed: {}", e))
                 .is_err()
             {
+                emu.try_write_sav().expect("Write game save if need be");
+
                 *control_flow = ControlFlow::Exit;
                 return;
             }
@@ -94,6 +108,8 @@ fn main() -> Result<()> {
 
         if input.update(&event) {
             if input.key_pressed(VirtualKeyCode::Escape) || input.quit() {
+                emu.try_write_sav().expect("Write game save if need be");
+
                 *control_flow = ControlFlow::Exit;
                 return;
             }
@@ -102,12 +118,17 @@ fn main() -> Result<()> {
                 pixels.resize_surface(size.width, size.height);
             }
 
-            cycle_count += gb::emu::run_frame(&mut game_boy, &mut gamepad, &input);
+            cycle_count += gb::emu::run_frame(&mut emu, &mut gamepad, &input);
 
             if cycle_count >= gb::emu::CYCLES_IN_FRAME {
                 cycle_count %= gb::emu::CYCLES_IN_FRAME;
 
-                gb::emu::draw(game_boy.ppu(), pixels.get_frame());
+                let buf: &mut [u8; GB_WIDTH * GB_HEIGHT * 4] = pixels
+                    .get_frame()
+                    .try_into()
+                    .expect("Size of Pixel Buffer is GB_WIDTH * GB_HEIGHT * 4");
+
+                gb::emu::draw_frame(&emu, buf);
                 window.request_redraw();
             }
         }

src/ppu.rs

@@ -261,7 +261,7 @@ impl Ppu {
                 TileLow => {
                     let obj_size = self.ctrl.obj_size();
 
-                    let addr = PixelFetcher::get_obj_addr(&attr, &self.pos, obj_size);
+                    let addr = PixelFetcher::get_obj_addr(attr, &self.pos, obj_size);
 
                     let byte = self.read_byte(addr);
                     self.fetch.obj.tile.with_low_byte(byte);
@@ -272,7 +272,7 @@ impl Ppu {
                 TileHigh => {
                     let obj_size = self.ctrl.obj_size();
 
-                    let addr = PixelFetcher::get_obj_addr(&attr, &self.pos, obj_size);
+                    let addr = PixelFetcher::get_obj_addr(attr, &self.pos, obj_size);
 
                     let byte = self.read_byte(addr + 1);
                     self.fetch.obj.tile.with_high_byte(byte);
@@ -418,8 +418,8 @@ impl Ppu {
         self.frame_buf.swap_with_slice(&mut blank);
     }
 
-    pub fn copy_to_gui(&self, frame: &mut [u8]) {
-        frame.copy_from_slice(self.frame_buf.as_ref());
+    pub(crate) fn frame_buf(&self) -> &[u8; GB_HEIGHT * GB_WIDTH * 4] {
+        &self.frame_buf
     }
 
     fn clock_fifo(&mut self) -> Option<GrayShade> {
@@ -629,6 +629,7 @@ impl ObjectBuffer {
         self.len += 1;
     }
 
+    #[inline]
     fn iter_mut(&mut self) -> std::slice::IterMut<'_, Option<ObjectAttribute>> {
         self.inner.iter_mut()
     }