chore: remove Cycle struct and begin scheduler design

src/cpu.rs

@@ -1,10 +1,10 @@
 use crate::apu::Apu;
 use crate::bus::{Bus, BusIo};
-use crate::instruction::cycle::Cycle;
 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};
 
@@ -133,7 +133,7 @@ impl Cpu {
             self.bus.clock();
 
             let elapsed = match kind {
-                ImeEnabled | NonePending => Cycle::new(4),
+                ImeEnabled | NonePending => 4,
                 SomePending => todo!("Implement HALT bug"),
             };
 
@@ -146,11 +146,11 @@ impl Cpu {
         self.handle_ei();
 
         // For use in Blargg's Test ROMs
-        // if self.read_byte(0xFF02) == 0x81 {
+        if self.read_byte(0xFF02) == 0x81 {
-        //     let c = self.read_byte(0xFF01) as char;
+            let c = self.read_byte(0xFF01) as char;
-        //     self.write_byte(0xFF02, 0x00);
+            self.write_byte(0xFF02, 0x00);
-        //     eprint!("{}", c);
+            eprint!("{}", c);
-        // }
+        }
 
         elapsed
     }

src/emu.rs

@@ -1,14 +1,14 @@
 use crate::cpu::Cpu as SM83;
-use crate::instruction::cycle::Cycle;
 use crate::joypad;
 use crate::ppu::Ppu;
+use crate::Cycle;
 use anyhow::Result;
 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";
 
@@ -34,7 +34,7 @@ pub fn run(
     input: &WinitInputHelper,
     target: Cycle,
 ) -> Cycle {
-    let mut elapsed = Cycle::new(0);
+    let mut elapsed = 0;
 
     if let Some(event) = gamepad.next_event() {
         joypad::handle_gamepad_input(game_boy.joypad_mut(), event);
@@ -49,7 +49,7 @@ pub fn run(
 }
 
 pub fn run_frame(game_boy: &mut SM83, gamepad: &mut Gilrs, input: &WinitInputHelper) -> Cycle {
-    let mut elapsed = Cycle::new(0);
+    let mut elapsed = 0;
 
     if let Some(event) = gamepad.next_event() {
         joypad::handle_gamepad_input(game_boy.joypad_mut(), event);

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

@@ -11,7 +11,7 @@ use winit::window::{Window, WindowBuilder};
 use winit_input_helper::WinitInputHelper;
 
 const WINDOW_SCALE: usize = 3;
-const AUDIO_ENABLED: bool = true;
+const AUDIO_ENABLED: bool = false;
 
 fn main() -> Result<()> {
     let app = App::new(crate_name!())

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();
@@ -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,
+}