in progress refactor

Needs profiling

Cargo.toml

@@ -3,6 +3,7 @@ name = "gb"
 version = "0.1.0"
 authors = ["Rekai Musuka <rekai@musuka.dev>"]
 edition = "2018"
+resolver = "2"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
@@ -11,7 +12,7 @@ anyhow = "^1.0"
 bitfield = "^0.13"
 clap = "^2.33"
 gilrs = "^0.8"
-pixels = "^0.5"
+pixels = "^0.6"
 winit = "^0.25"
 winit_input_helper = "^0.10"
 rodio = "^0.14"

src/apu.rs

@@ -468,22 +468,8 @@ impl Channel1 {
 
         // If this bit is set, a trigger event occurs
         if self.freq_hi.initial() {
-            // Envelope Behaviour during trigger event
-            self.period_timer = self.envelope.period();
-            self.current_volume = self.envelope.init_vol();
-
-            // Sweep behaviour during trigger event
-            let sweep_period = self.sweep.period();
-            let sweep_shift = self.sweep.shift_count();
-            self.shadow_freq = self.frequency();
-            self.sweep_timer = if sweep_period == 0 { 8 } else { sweep_period };
-
-            if sweep_period != 0 || sweep_shift != 0 {
-                self.sweep_enabled = true;
-            }
-
-            if sweep_shift != 0 {
-                let _ = self.calc_sweep_freq();
+            if self.is_dac_enabled() {
+                self.enabled = true;
             }
 
             // Length behaviour during trigger event
@@ -491,8 +477,21 @@ impl Channel1 {
                 self.length_timer = 64;
             }
 
-            if self.is_dac_enabled() {
-                self.enabled = true;
+            // Envelope Behaviour during trigger event
+            self.period_timer = self.envelope.period();
+            self.current_volume = self.envelope.init_vol();
+
+            // Sweep behaviour during trigger event
+            let sweep_period = self.sweep.period();
+            let sweep_shift = self.sweep.shift_count();
+
+            self.shadow_freq = self.frequency();
+            self.sweep_timer = if sweep_period == 0 { 8 } else { sweep_period };
+
+            self.sweep_enabled = sweep_period != 0 || sweep_shift != 0;
+
+            if sweep_shift != 0 {
+                let _ = self.calc_sweep_freq();
             }
         }
     }

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)]
@@ -104,13 +97,13 @@ 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 +150,7 @@ 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 +162,7 @@ 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 +255,7 @@ 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 +269,7 @@ 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 +13,15 @@ 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,
-        })
+        }
     }
 
     fn detect_mbc(memory: &[u8]) -> Box<dyn MBCIo> {
@@ -47,6 +39,8 @@ impl Cartridge {
             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::MBC2 => Box::new(MBC2::new(rom_cap)),
+            MBCKind::MBC2WithBattery => Box::new(MBC2::new(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::MBC5 => Box::new(MBC5::new(ram_cap, rom_cap)),
@@ -80,14 +74,18 @@ impl Cartridge {
     }
 
     fn find_mbc(memory: &[u8]) -> MBCKind {
+        use MBCKind::*;
+
         match memory[MBC_TYPE_ADDRESS] {
-            0x00 => MBCKind::None,
-            0x01 | 0x02 => MBCKind::MBC1,
-            0x03 => MBCKind::MBC1WithBattery,
-            0x19 | 0x1A => MBCKind::MBC5,
-            0x1B => MBCKind::MBC5WithBattery,
-            0x13 => MBCKind::MBC3WithBattery,
-            0x11 | 0x12 => MBCKind::MBC3,
+            0x00 => None,
+            0x01 | 0x02 => MBC1,
+            0x03 => MBC1WithBattery,
+            0x05 => MBC2,
+            0x06 => MBC2WithBattery,
+            0x19 | 0x1A => MBC5,
+            0x1B => MBC5WithBattery,
+            0x13 => MBC3WithBattery,
+            0x11 | 0x12 => MBC3,
             id => unimplemented!("id {:#04X} is an unsupported MBC", id),
         }
     }
@@ -182,16 +180,16 @@ impl MBC1 {
         }
     }
 
-    fn ram_addr(&self, addr: u16) -> u16 {
+    fn ram_addr(&self, addr: u16) -> usize {
         use RamSize::*;
 
         match self.ram_size {
-            Unused | One => (addr - 0xA000) % self.ram_size.capacity() as u16,
+            Unused | One => (addr as usize - 0xA000) % self.ram_size.capacity(),
             Four => {
                 if self.mode {
-                    0x2000 * self.ram_bank as u16 + (addr - 0xA000)
+                    0x2000 * self.ram_bank as usize + (addr as usize - 0xA000)
                 } else {
-                    addr - 0xA000
+                    addr as usize - 0xA000
                 }
             }
             _ => unreachable!("RAM size can not be greater than 32KB on MBC1"),
@@ -204,23 +202,17 @@ impl MBCIo for MBC1 {
         use MBCResult::*;
 
         match addr {
-            0x0000..=0x3FFF => {
-                if self.mode {
-                    Address(0x4000 * self.zero_bank() as usize + addr as usize)
-                } else {
-                    Address(addr as usize)
-                }
+            0x0000..=0x3FFF if self.mode => {
+                Address(0x4000 * self.zero_bank() as usize + addr as usize)
             }
+            0x0000..=0x3FFF => Address(addr as usize),
             0x4000..=0x7FFF => {
                 Address(0x4000 * self.high_bank() as usize + (addr as usize - 0x4000))
             }
-            0xA000..=0xBFFF => {
-                if self.mem_enabled {
-                    Value(self.memory[self.ram_addr(addr) as usize])
-                } else {
-                    Value(0xFF)
-                }
+            0xA000..=0xBFFF if self.mem_enabled && self.ram_size != RamSize::None => {
+                Value(self.memory[self.ram_addr(addr)])
             }
+            0xA000..=0xBFFF => Value(0xFF),
             _ => unreachable!("A read from {:#06X} should not be handled by MBC1", addr),
         }
     }
@@ -229,18 +221,14 @@ impl MBCIo for MBC1 {
         match addr {
             0x0000..=0x1FFF => self.mem_enabled = (byte & 0x0F) == 0x0A,
             0x2000..=0x3FFF => {
-                self.rom_bank = if byte == 0x00 {
-                    0x01
-                } else {
-                    byte & self.rom_size_mask()
-                };
-
-                self.rom_bank &= 0x1F;
+                let value = byte & 0x1F;
+                let masked_value = byte & self.rom_size_mask();
+                self.rom_bank = if value == 0 { 0x01 } else { masked_value };
             }
             0x4000..=0x5FFF => self.ram_bank = byte & 0x03,
             0x6000..=0x7FFF => self.mode = (byte & 0x01) == 0x01,
-            0xA000..=0xBFFF if self.mem_enabled => {
-                let ram_addr = self.ram_addr(addr) as usize;
+            0xA000..=0xBFFF if self.mem_enabled && self.ram_size != RamSize::None => {
+                let ram_addr = self.ram_addr(addr);
                 self.memory[ram_addr] = byte;
             }
             0xA000..=0xBFFF => {} // Ram isn't enabled, ignored write
@@ -405,6 +393,67 @@ impl MBCIo for MBC5 {
     }
 }
 
+#[derive(Debug)]
+struct MBC2 {
+    /// 4-bit number
+    rom_bank: u8,
+    memory: Box<[u8; Self::RAM_SIZE]>,
+    mem_enabled: bool,
+
+    rom_cap: usize,
+}
+
+impl MBC2 {
+    const RAM_SIZE: usize = 0x0200;
+
+    fn new(rom_cap: usize) -> Self {
+        Self {
+            rom_bank: 0x01,
+            memory: Box::new([0; Self::RAM_SIZE]),
+            mem_enabled: Default::default(),
+            rom_cap,
+        }
+    }
+
+    fn rom_addr(&self, addr: u16) -> usize {
+        (0x4000 * self.rom_bank as usize + (addr as usize - 0x4000)) % self.rom_cap
+    }
+}
+
+impl MBCIo for MBC2 {
+    fn handle_read(&self, addr: u16) -> MBCResult {
+        use MBCResult::*;
+
+        match addr {
+            0x0000..=0x3FFF => Address(addr as usize),
+            0x4000..=0x7FFF => Address(self.rom_addr(addr)),
+            0xA000..=0xBFFF if self.mem_enabled => {
+                let mbc2_addr = addr as usize & (Self::RAM_SIZE - 1);
+                Value(self.memory[mbc2_addr] | 0xF0)
+            }
+            0xA000..=0xBFFF => Value(0xFF),
+            _ => unreachable!("A read from {:#06X} should not be handled by MBC2", addr),
+        }
+    }
+
+    fn handle_write(&mut self, addr: u16, byte: u8) {
+        let nybble = byte & 0x0F;
+
+        match addr {
+            0x0000..=0x3FFF if addr >> 8 & 0x01 == 0x01 => {
+                self.rom_bank = if nybble == 0x00 { 0x01 } else { nybble };
+            }
+            0x0000..=0x3FFF => self.mem_enabled = nybble == 0x0A,
+            0xA000..=0xBFFF if self.mem_enabled => {
+                let mbc2_addr = addr as usize & (Self::RAM_SIZE - 1);
+                self.memory[mbc2_addr] = nybble;
+            }
+            0x4000..=0x7FFF | 0xA000..=0xBFFF => {}
+            _ => unreachable!("A write to {:#06X} should not be handled by MBC2", addr),
+        }
+    }
+}
+
 #[derive(Debug)]
 struct NoMBC;
 
@@ -434,6 +483,8 @@ enum MBCKind {
     None,
     MBC1,
     MBC1WithBattery,
+    MBC2,
+    MBC2WithBattery,
     MBC3,
     MBC3WithBattery,
     MBC5,
@@ -446,7 +497,7 @@ impl Default for MBCKind {
     }
 }
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 enum RamSize {
     None = 0x00,
     Unused = 0x01,

src/cpu.rs

@@ -1,10 +1,7 @@
-use crate::apu::Apu;
-use crate::bus::{Bus, BusIo};
-use crate::instruction::cycle::Cycle;
+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 {
@@ -72,14 +69,6 @@ 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 {
@@ -133,7 +122,7 @@ impl Cpu {
             self.bus.clock();
 
             let elapsed = match kind {
-                ImeEnabled | NonePending => Cycle::new(4),
+                ImeEnabled | NonePending => 4,
                 SomePending => todo!("Implement HALT bug"),
             };
 
@@ -146,11 +135,11 @@ impl Cpu {
         self.handle_ei();
 
         // For use in Blargg's Test ROMs
-        // if self.read_byte(0xFF02) == 0x81 {
-        //     let c = self.read_byte(0xFF01) as char;
-        //     self.write_byte(0xFF02, 0x00);
-        //     eprint!("{}", c);
-        // }
+        if self.read_byte(0xFF02) == 0x81 {
+            let c = self.read_byte(0xFF01) as char;
+            self.write_byte(0xFF02, 0x00);
+            eprint!("{}", c);
+        }
 
         elapsed
     }
@@ -167,16 +156,12 @@ impl BusIo for Cpu {
 }
 
 impl Cpu {
-    pub fn ppu(&mut self) -> &Ppu {
-        &self.bus.ppu
+    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
+    pub(crate) fn bus_mut(&mut self) -> &mut Bus {
+        &mut self.bus
     }
 
     fn handle_ei(&mut self) {

src/emu.rs

@@ -1,73 +1,121 @@
-use crate::cpu::Cpu as SM83;
-use crate::instruction::cycle::Cycle;
-use crate::joypad;
-use crate::ppu::Ppu;
-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 gilrs::Gilrs;
 use std::time::Duration;
 use winit_input_helper::WinitInputHelper;
 
 pub const SM83_CYCLE_TIME: Duration = Duration::from_nanos(1_000_000_000 / SM83_CLOCK_SPEED);
-pub const CYCLES_IN_FRAME: Cycle = Cycle::new(456 * 154); // 456 Cycles times 154 scanlines
+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";
-const GAMEPAD_ENABLED: bool = true;
 
-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(),
-    };
+pub fn run_frame(emu: &mut Emulator, gamepad: &mut Gilrs, key: &WinitInputHelper) -> Cycle {
+    let mut elapsed = 0;
 
-    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 {
-    let mut elapsed = Cycle::new(0);
-
-    if GAMEPAD_ENABLED {
-        if let Some(event) = gamepad.next_event() {
-            joypad::handle_gamepad_input(game_boy.joypad_mut(), event);
-        }
+    if let Some(event) = gamepad.next_event() {
+        joypad::handle_gamepad_input(emu.joyp_mut(), event);
     }
 
-    joypad::handle_keyboard_input(game_boy.joypad_mut(), input);
-    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 = Cycle::new(0);
-
-    if GAMEPAD_ENABLED {
-        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);
+    joypad::handle_keyboard_input(emu.joyp_mut(), key);
     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 {
+        self.cpu.step()
+    }
+
+    fn load_cart(&mut self, rom: Vec<u8>) {
+        self.cpu.bus_mut().load_cart(rom)
+    }
+
+    fn joyp_mut(&mut self) -> &mut Joypad {
+        &mut self.cpu.bus_mut().joypad
+    }
+
+    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 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/lib.rs

@@ -1,5 +1,5 @@
 pub use apu::gen::AudioSPSC;
-pub use instruction::cycle::Cycle;
+pub type Cycle = u64;
 
 pub const GB_WIDTH: usize = 160;
 pub const GB_HEIGHT: usize = 144;

src/main.rs

@@ -1,18 +1,20 @@
+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};
 use rodio::{OutputStream, Sink};
-use std::time::{Duration, Instant};
-use winit::dpi::LogicalSize;
+use winit::dpi::{LogicalSize, PhysicalSize};
 use winit::event::{Event, VirtualKeyCode};
 use winit::event_loop::{ControlFlow, EventLoop};
 use winit::window::{Window, WindowBuilder};
 use winit_input_helper::WinitInputHelper;
 
-const WINDOW_SCALE: f64 = 2.0;
-const AUDIO_ENABLED: bool = true;
+const WINDOW_SCALE: usize = 3;
+const AUDIO_ENABLED: bool = false;
 
 fn main() -> Result<()> {
     let app = App::new(crate_name!())
@@ -39,13 +41,15 @@ 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();
+    let rom_title = emu.title();
 
     let mut gamepad = Gilrs::new().expect("Initialize Controller Support");
 
@@ -69,17 +73,20 @@ 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);
-        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();
         });
     }
 
-    let mut start = Instant::now();
-    let frame_time = Duration::from_secs_f64(1.0 / 59.73); // 59.73 Hz on Host
     let mut cycle_count: Cycle = Default::default();
 
     event_loop.run(move |event, _, control_flow| {
@@ -104,57 +111,34 @@ fn main() -> Result<()> {
                 pixels.resize_surface(size.width, size.height);
             }
 
-            let mut diff = Instant::now() - start;
-            while diff.subsec_nanos() < frame_time.subsec_nanos() {
-                if cycle_count < gb::emu::CYCLES_IN_FRAME {
-                    cycle_count += gb::emu::run_frame(&mut game_boy, &mut gamepad, &input);
-                }
-
-                diff = Instant::now() - start;
-            }
-            start = Instant::now();
+            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();
             }
         }
     });
 }
 
-#[cfg(not(windows))]
 fn create_window(event_loop: &EventLoop<()>, title: &str) -> Result<Window> {
-    let size = LogicalSize::new(
-        (GB_WIDTH as f64) * WINDOW_SCALE,
-        (GB_HEIGHT as f64) * WINDOW_SCALE,
+    let logical = LogicalSize::new(GB_WIDTH as f64, GB_HEIGHT as f64);
+    let physical = PhysicalSize::new(
+        (GB_WIDTH * WINDOW_SCALE) as f32,
+        (GB_HEIGHT * WINDOW_SCALE) as f32,
     );
+
     Ok(WindowBuilder::new()
         .with_title(title)
-        .with_inner_size(size)
-        .with_min_inner_size(size)
+        .with_min_inner_size(logical)
+        .with_inner_size(physical)
         .with_resizable(true)
-        .with_decorations(true)
-        .with_transparent(false)
-        .build(event_loop)?)
-}
-
-#[cfg(windows)]
-fn create_window(event_loop: &EventLoop<()>, title: &str) -> Result<Window> {
-    use winit::platform::windows::WindowBuilderExtWindows;
-
-    let size = LogicalSize::new(
-        (GB_WIDTH as f64) * WINDOW_SCALE,
-        (GB_HEIGHT as f64) * WINDOW_SCALE,
-    );
-    Ok(WindowBuilder::new()
-        .with_title(title)
-        .with_inner_size(size)
-        .with_min_inner_size(size)
-        .with_resizable(true)
-        .with_decorations(true)
-        .with_transparent(false)
-        .with_drag_and_drop(false)
         .build(event_loop)?)
 }

src/ppu.rs

@@ -1,5 +1,5 @@
 use crate::bus::BusIo;
-use crate::instruction::cycle::Cycle;
+use crate::Cycle;
 use crate::GB_HEIGHT;
 use crate::GB_WIDTH;
 use dma::DirectMemoryAccess;
@@ -79,7 +79,7 @@ impl Ppu {
 
         match self.stat.mode() {
             PpuMode::OamScan => {
-                if self.cycle >= 80.into() {
+                if self.cycle >= 80 {
                     self.stat.set_mode(PpuMode::Drawing);
                 }
 
@@ -88,7 +88,7 @@ impl Ppu {
             PpuMode::Drawing => {
                 if self.ctrl.lcd_enabled() {
                     // Only Draw when the LCD Is Enabled
-                    self.draw(self.cycle.into());
+                    self.draw(self.cycle);
                 } else {
                     self.reset();
                 }
@@ -125,7 +125,7 @@ impl Ppu {
             PpuMode::HBlank => {
                 // This mode will always end at 456 cycles
 
-                if self.cycle >= 456.into() {
+                if self.cycle >= 456 {
                     self.cycle %= 456;
                     self.pos.line_y += 1;
 
@@ -167,7 +167,7 @@ impl Ppu {
                 }
             }
             PpuMode::VBlank => {
-                if self.cycle > 456.into() {
+                if self.cycle > 456 {
                     self.cycle %= 456;
                     self.pos.line_y += 1;
 
@@ -228,7 +228,7 @@ impl Ppu {
         self.scan_state.next();
     }
 
-    fn draw(&mut self, _cycle: u32) {
+    fn draw(&mut self, _cycle: Cycle) {
         use FetcherState::*;
 
         let mut iter = self.obj_buffer.iter_mut();
@@ -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> {
@@ -470,7 +470,7 @@ impl Default for Ppu {
     fn default() -> Self {
         Self {
             vram: Box::new([0u8; VRAM_SIZE]),
-            cycle: Cycle::new(0),
+            cycle: Default::default(),
             frame_buf: Box::new([0; GB_WIDTH * GB_HEIGHT * 4]),
             int: Default::default(),
             ctrl: Default::default(),

src/ppu/dma.rs

@@ -1,4 +1,4 @@
-use crate::instruction::cycle::Cycle;
+use crate::Cycle;
 
 #[derive(Debug, Default)]
 pub(crate) struct DirectMemoryAccess {
@@ -56,7 +56,7 @@ impl DirectMemoryAccess {
     }
 
     fn reset(&mut self) {
-        self.cycle = Cycle::new(0);
+        self.cycle = 0;
         self.state = DmaState::Disabled;
         self.start.0 = None;
     }

src/scheduler.rs

@@ -0,0 +1,79 @@
+use crate::Cycle;
+use std::collections::BinaryHeap;
+
+#[derive(Debug)]
+pub(crate) struct Scheduler {
+    timestamp: Cycle,
+    queue: BinaryHeap<Event>,
+}
+
+impl Scheduler {
+    pub(crate) fn init() -> Self {
+        let mut scheduler = Self {
+            timestamp: Default::default(),
+            queue: Default::default(),
+        };
+
+        scheduler.push(Event {
+            kind: EventKind::TimestampOverflow,
+            timestamp: Cycle::MAX,
+            cb: |_delay| panic!("Reached Cycle::MAX"),
+        });
+
+        scheduler
+    }
+
+    pub(crate) fn push(&mut self, event: Event) {
+        self.queue.push(event);
+    }
+
+    pub(crate) fn step(&mut self, cycles: Cycle) {
+        self.timestamp += cycles;
+
+        loop {
+            let should_pop = match self.queue.peek() {
+                Some(event) => self.timestamp >= event.timestamp,
+                None => false,
+            };
+
+            if !should_pop {
+                break;
+            }
+
+            let event = self.queue.pop().expect("Pop Event from Scheduler Queue");
+
+            (event.cb)(self.timestamp - event.timestamp);
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct Event {
+    kind: EventKind,
+    cb: fn(Cycle),
+    pub(crate) timestamp: Cycle,
+}
+
+impl Eq for Event {}
+impl PartialEq for Event {
+    fn eq(&self, other: &Self) -> bool {
+        self.kind == other.kind && self.timestamp == other.timestamp
+    }
+}
+
+impl PartialOrd for Event {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for Event {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.timestamp.cmp(&other.timestamp)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum EventKind {
+    TimestampOverflow,
+}