core: Start working on a scheduler

A more robust cycle aware event scheduling, to easily implement serial-io, dmg audio channels and improve accuracy.
This brings a slight performance hit :/

I also ran dos2unix on some of the files :D


Former-commit-id: 62f4ba33e3a083b7976d6512ba6f5720ec493aa0
Former-commit-id: a4b3a92cd1eb156bbe9fd0ef77fbb0e7a45660cb

core/src/gba.rs

@@ -11,13 +11,14 @@ use super::dma::DmaController;
 use super::gpu::*;
 use super::interrupt::*;
 use super::iodev::*;
+use super::sched::{EventHandler, EventType, Scheduler, SharedScheduler};
 use super::sound::SoundController;
 use super::sysbus::SysBus;
 use super::timer::Timers;
 
-use super::{AudioInterface, InputInterface};
 #[cfg(not(feature = "no_video_interface"))]
 use super::VideoInterface;
+use super::{AudioInterface, InputInterface};
 
 pub struct GameBoyAdvance {
     pub sysbus: Box<SysBus>,
@@ -30,6 +31,8 @@ pub struct GameBoyAdvance {
 
     pub cycles_to_next_event: usize,
 
+    scheduler: SharedScheduler,
+
     overshoot_cycles: usize,
     interrupt_flags: SharedInterruptFlags,
 }
@@ -37,6 +40,7 @@ pub struct GameBoyAdvance {
 #[derive(Serialize, Deserialize)]
 struct SaveState {
     sysbus: Box<SysBus>,
+    scheduler: Scheduler,
     interrupt_flags: u16,
     cpu: arm7tdmi::Core,
 }
@@ -58,8 +62,7 @@ impl GameBoyAdvance {
     pub fn new(
         bios_rom: Box<[u8]>,
         gamepak: Cartridge,
-        #[cfg(not(feature = "no_video_interface"))]
+        #[cfg(not(feature = "no_video_interface"))] video_device: Rc<RefCell<dyn VideoInterface>>,
-        video_device: Rc<RefCell<dyn VideoInterface>>,
         audio_device: Rc<RefCell<dyn AudioInterface>>,
         input_device: Rc<RefCell<dyn InputInterface>>,
     ) -> GameBoyAdvance {
@@ -70,12 +73,14 @@ impl GameBoyAdvance {
         };
 
         let interrupt_flags = Rc::new(Cell::new(IrqBitmask(0)));
+        let scheduler = Scheduler::new_shared();
 
         let intc = InterruptController::new(interrupt_flags.clone());
-        let gpu = Box::new(Gpu::new(interrupt_flags.clone()));
+        let gpu = Box::new(Gpu::new(scheduler.clone(), interrupt_flags.clone()));
         let dmac = DmaController::new(interrupt_flags.clone());
         let timers = Timers::new(interrupt_flags.clone());
         let sound_controller = Box::new(SoundController::new(
+            scheduler.clone(),
             audio_device.borrow().get_sample_rate() as f32,
         ));
         let io = IoDevices::new(intc, gpu, dmac, timers, sound_controller);
@@ -92,6 +97,8 @@ impl GameBoyAdvance {
             audio_device: audio_device,
             input_device: input_device,
 
+            scheduler: scheduler,
+
             cycles_to_next_event: 1,
             overshoot_cycles: 0,
             interrupt_flags: interrupt_flags,
@@ -104,8 +111,7 @@ impl GameBoyAdvance {
 
     pub fn from_saved_state(
         savestate: &[u8],
-        #[cfg(not(feature = "no_video_interface"))]
+        #[cfg(not(feature = "no_video_interface"))] video_device: Rc<RefCell<dyn VideoInterface>>,
-        video_device: Rc<RefCell<dyn VideoInterface>>,
         audio_device: Rc<RefCell<dyn AudioInterface>>,
         input_device: Rc<RefCell<dyn InputInterface>>,
     ) -> bincode::Result<GameBoyAdvance> {
@@ -114,7 +120,10 @@ impl GameBoyAdvance {
         let arm7tdmi = decoded.cpu;
         let mut sysbus = decoded.sysbus;
         let interrupts = Rc::new(Cell::new(IrqBitmask(decoded.interrupt_flags)));
+        let scheduler = decoded.scheduler.make_shared();
 
+        sysbus.io.gpu.set_scheduler(scheduler.clone());
+        sysbus.io.sound.set_scheduler(scheduler.clone());
         sysbus.io.connect_irq(interrupts.clone());
 
         Ok(GameBoyAdvance {
@@ -131,6 +140,8 @@ impl GameBoyAdvance {
             cycles_to_next_event: 1,
 
             overshoot_cycles: 0,
+
+            scheduler: scheduler,
         })
     }
 
@@ -139,6 +150,7 @@ impl GameBoyAdvance {
             cpu: self.cpu.clone(),
             sysbus: self.sysbus.clone(),
             interrupt_flags: self.interrupt_flags.get().value(),
+            scheduler: (*self.scheduler).clone(),
         };
 
         bincode::serialize(&s)
@@ -149,10 +161,13 @@ impl GameBoyAdvance {
 
         self.cpu = decoded.cpu;
         self.sysbus = decoded.sysbus;
+        self.scheduler = Scheduler::make_shared(decoded.scheduler);
         self.interrupt_flags = Rc::new(Cell::new(IrqBitmask(decoded.interrupt_flags)));
 
-        // Redistribute shared pointer for interrupts
+        // Redistribute shared pointers
         self.sysbus.io.connect_irq(self.interrupt_flags.clone());
+        self.sysbus.io.gpu.set_scheduler(self.scheduler.clone());
+        self.sysbus.io.sound.set_scheduler(self.scheduler.clone());
 
         self.cycles_to_next_event = 1;
 
@@ -177,10 +192,12 @@ impl GameBoyAdvance {
     pub fn frame(&mut self) {
         self.key_poll();
 
+        let mut scheduler = self.scheduler.clone();
+
         let mut remaining_cycles = CYCLES_FULL_REFRESH - self.overshoot_cycles;
 
         while remaining_cycles > 0 {
-            let cycles = self.step();
+            let cycles = self.step(&mut scheduler);
             if remaining_cycles >= cycles {
                 remaining_cycles -= cycles;
             } else {
@@ -228,15 +245,15 @@ impl GameBoyAdvance {
         self.cpu.cycles - previous_cycles
     }
 
-    pub fn step(&mut self) -> usize {
+    pub fn step(&mut self, scheduler: &mut Scheduler) -> usize {
         // I hate myself for doing this, but rust left me no choice.
         let io = unsafe {
             let ptr = &mut *self.sysbus as *mut SysBus;
             &mut (*ptr).io as &mut IoDevices
         };
 
-        let mut cycles_left = self.cycles_to_next_event;
+        let available_cycles = self.scheduler.get_cycles_to_next_event();
-        let mut cycles_to_next_event = std::usize::MAX;
+        let mut cycles_left = available_cycles;
         let mut cycles = 0;
 
         while cycles_left > 0 {
@@ -259,18 +276,9 @@ impl GameBoyAdvance {
             cycles_left -= _cycles;
         }
 
-        // update gpu & sound
         io.timers.update(cycles, &mut self.sysbus);
-        io.gpu.update(
+
-            cycles,
+        scheduler.run(cycles, self);
-            &mut cycles_to_next_event,
-            self.sysbus.as_mut(),
-            #[cfg(not(feature = "no_video_interface"))]
-            &self.video_device,
-        );
-        io.sound
-            .update(cycles, &mut cycles_to_next_event, &self.audio_device);
-        self.cycles_to_next_event = cycles_to_next_event;
 
         cycles
     }
@@ -293,17 +301,11 @@ impl GameBoyAdvance {
         let cycles = self.step_cpu(io);
         let breakpoint = self.check_breakpoint();
 
-        let mut _ignored = 0;
-        // update gpu & sound
         io.timers.update(cycles, &mut self.sysbus);
-        io.gpu.update(
+
-            cycles,
+        // update gpu & sound
-            &mut _ignored,
+        let mut scheduler = self.scheduler.clone();
-            self.sysbus.as_mut(),
+        scheduler.run(cycles, self);
-            #[cfg(not(feature = "no_video_interface"))]
-            &self.video_device,
-        );
-        io.sound.update(cycles, &mut _ignored, &self.audio_device);
 
         breakpoint
     }
@@ -320,6 +322,25 @@ impl GameBoyAdvance {
     }
 }
 
+impl EventHandler for GameBoyAdvance {
+    fn handle_event(&mut self, event: EventType, extra_cycles: usize) {
+        let io = unsafe {
+            let ptr = &mut *self.sysbus as *mut SysBus;
+            &mut (*ptr).io as &mut IoDevices
+        };
+        match event {
+            EventType::Gpu(event) => io.gpu.on_event(
+                event,
+                extra_cycles,
+                self.sysbus.as_mut(),
+                #[cfg(not(feature = "no_video_interface"))]
+                &self.video_device,
+            ),
+            EventType::Apu(event) => io.sound.on_event(event, extra_cycles, &self.audio_device),
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -337,6 +358,7 @@ mod tests {
         }
     }
 
+    #[cfg(not(feature = "no_video_interface"))]
     impl VideoInterface for DummyInterface {}
     impl AudioInterface for DummyInterface {}
     impl InputInterface for DummyInterface {}
@@ -350,8 +372,14 @@ mod tests {
             .build()
             .unwrap();
         let dummy = Rc::new(RefCell::new(DummyInterface::new()));
-        let mut gba =
+        let mut gba = GameBoyAdvance::new(
-            GameBoyAdvance::new(bios, cartridge, dummy.clone(), dummy.clone(), dummy.clone());
+            bios,
+            cartridge,
+            #[cfg(not(feature = "no_video_interface"))]
+            dummy.clone(),
+            dummy.clone(),
+            dummy.clone(),
+        );
         gba.skip_bios();
 
         gba

core/src/gpu/mod.rs

@@ -9,6 +9,7 @@ use serde::{Deserialize, Serialize};
 use super::bus::*;
 use super::dma::{DmaNotifer, TIMING_HBLANK, TIMING_VBLANK};
 use super::interrupt::{self, Interrupt, InterruptConnect, SharedInterruptFlags};
+use super::sched::*;
 pub use super::sysbus::consts::*;
 use super::util::BoxedMemory;
 #[cfg(not(feature = "no_video_interface"))]
@@ -183,6 +184,11 @@ pub struct Gpu {
     pub state: GpuState,
     interrupt_flags: SharedInterruptFlags,
 
+    /// When deserializing this struct using serde, make sure to call Gpu:::set_scheduler
+    #[serde(skip)]
+    #[serde(default = "Scheduler::new_shared")]
+    scheduler: SharedScheduler,
+
     /// how many cycles left until next gpu state ?
     cycles_left_for_current_state: usize,
 
@@ -224,9 +230,11 @@ impl InterruptConnect for Gpu {
 }
 
 impl Gpu {
-    pub fn new(interrupt_flags: SharedInterruptFlags) -> Gpu {
+    pub fn new(mut scheduler: SharedScheduler, interrupt_flags: SharedInterruptFlags) -> Gpu {
+        scheduler.add_gpu_event(GpuEvent::HDraw, CYCLES_HDRAW);
         Gpu {
             interrupt_flags,
+            scheduler,
             dispcnt: DisplayControl(0x80),
             dispstat: DisplayStatus(0),
             backgrounds: [
@@ -261,6 +269,10 @@ impl Gpu {
         }
     }
 
+    pub fn set_scheduler(&mut self, scheduler: SharedScheduler) {
+        self.scheduler = scheduler;
+    }
+
     pub fn write_dispcnt(&mut self, value: u16) {
         let new_dispcnt = DisplayControl(value);
         let old_mode = self.dispcnt.mode();
@@ -414,6 +426,93 @@ impl Gpu {
         &self.frame_buffer
     }
 
+    #[inline]
+    fn update_vcount(&mut self, value: usize) {
+        self.vcount = value;
+        let vcount_setting = self.dispstat.vcount_setting();
+        self.dispstat
+            .set_vcount_flag(vcount_setting == self.vcount as u16);
+
+        if self.dispstat.vcount_irq_enable() && self.dispstat.get_vcount_flag() {
+            interrupt::signal_irq(&self.interrupt_flags, Interrupt::LCD_VCounterMatch);
+        }
+    }
+
+    #[inline]
+    fn handle_hdraw<D: DmaNotifer>(&mut self, dma_notifier: &mut D) -> (GpuEvent, usize) {
+        self.dispstat.set_hblank_flag(true);
+        if self.dispstat.hblank_irq_enable() {
+            interrupt::signal_irq(&self.interrupt_flags, Interrupt::LCD_HBlank);
+        };
+        dma_notifier.notify(TIMING_HBLANK);
+
+        // Next event
+        (GpuEvent::HBlank, CYCLES_HBLANK)
+    }
+
+    fn handle_hblank<D: DmaNotifer>(
+        &mut self,
+        dma_notifier: &mut D,
+        #[cfg(not(feature = "no_video_interface"))] video_device: &VideoDeviceRcRefCell,
+    ) -> (GpuEvent, usize) {
+        self.update_vcount(self.vcount + 1);
+
+        if self.vcount < DISPLAY_HEIGHT {
+            self.dispstat.set_hblank_flag(false);
+            self.render_scanline();
+            // update BG2/3 reference points on the end of a scanline
+            for i in 0..2 {
+                self.bg_aff[i].internal_x += self.bg_aff[i].pb as i16 as i32;
+                self.bg_aff[i].internal_y += self.bg_aff[i].pd as i16 as i32;
+            }
+
+            (GpuEvent::HDraw, CYCLES_HDRAW)
+        } else {
+            // latch BG2/3 reference points on vblank
+            for i in 0..2 {
+                self.bg_aff[i].internal_x = self.bg_aff[i].x;
+                self.bg_aff[i].internal_y = self.bg_aff[i].y;
+            }
+
+            self.dispstat.set_vblank_flag(true);
+            self.dispstat.set_hblank_flag(false);
+            if self.dispstat.vblank_irq_enable() {
+                interrupt::signal_irq(&self.interrupt_flags, Interrupt::LCD_VBlank);
+            };
+
+            dma_notifier.notify(TIMING_VBLANK);
+
+            #[cfg(not(feature = "no_video_interface"))]
+            video_device.borrow_mut().render(&self.frame_buffer);
+
+            self.obj_buffer_reset();
+
+            (GpuEvent::VBlankHDraw, CYCLES_HDRAW)
+        }
+    }
+
+    fn handle_vblank_hdraw(&mut self) -> (GpuEvent, usize) {
+        self.dispstat.set_hblank_flag(true);
+        if self.dispstat.hblank_irq_enable() {
+            interrupt::signal_irq(&self.interrupt_flags, Interrupt::LCD_HBlank);
+        };
+        (GpuEvent::VBlankHBlank, CYCLES_HBLANK)
+    }
+
+    fn handle_vblank_hblank(&mut self) -> (GpuEvent, usize) {
+        if self.vcount < DISPLAY_HEIGHT + VBLANK_LINES - 1 {
+            self.update_vcount(self.vcount + 1);
+            self.dispstat.set_hblank_flag(false);
+            (GpuEvent::VBlankHDraw, CYCLES_HDRAW)
+        } else {
+            self.update_vcount(0);
+            self.dispstat.set_vblank_flag(false);
+            self.dispstat.set_hblank_flag(false);
+            self.render_scanline();
+            (GpuEvent::HDraw, CYCLES_HDRAW)
+        }
+    }
+
     pub fn on_state_completed<D>(
         &mut self,
         completed: GpuState,
@@ -440,12 +539,8 @@ impl Gpu {
                 // Transition to HBlank
                 self.state = HBlank;
                 self.cycles_left_for_current_state = CYCLES_HBLANK;
-                self.dispstat.set_hblank_flag(true);
 
-                if self.dispstat.hblank_irq_enable() {
+                self.handle_hdraw(dma_notifier);
-                    interrupt::signal_irq(&self.interrupt_flags, Interrupt::LCD_HBlank);
-                };
-                dma_notifier.notify(TIMING_HBLANK);
             }
             HBlank => {
                 update_vcount!(self.vcount + 1);
@@ -538,6 +633,29 @@ impl Gpu {
             *cycles_to_next_event = self.cycles_left_for_current_state;
         }
     }
+
+    pub fn on_event<D>(
+        &mut self,
+        event: GpuEvent,
+        extra_cycles: usize,
+        dma_notifier: &mut D,
+        #[cfg(not(feature = "no_video_interface"))] video_device: &VideoDeviceRcRefCell,
+    ) where
+        D: DmaNotifer,
+    {
+        let (next_event, cycles) = match event {
+            GpuEvent::HDraw => self.handle_hdraw(dma_notifier),
+            GpuEvent::HBlank => self.handle_hblank(
+                dma_notifier,
+                #[cfg(not(feature = "no_video_interface"))]
+                video_device,
+            ),
+            GpuEvent::VBlankHDraw => self.handle_vblank_hdraw(),
+            GpuEvent::VBlankHBlank => self.handle_vblank_hblank(),
+        };
+        self.scheduler
+            .schedule(EventType::Gpu(next_event), cycles - extra_cycles);
+    }
 }
 
 impl Bus for Gpu {
@@ -625,6 +743,7 @@ mod tests {
         frame_counter: usize,
     }
 
+    #[cfg(not(feature = "no_video_interface"))]
     impl VideoInterface for TestVideoInterface {
         fn render(&mut self, _buffer: &[u32]) {
             self.frame_counter += 1;
@@ -633,8 +752,13 @@ mod tests {
 
     #[test]
     fn test_gpu_state_machine() {
-        let mut gpu = Gpu::new(Rc::new(Cell::new(Default::default())));
+        let mut gpu = Gpu::new(
+            Scheduler::new_shared(),
+            Rc::new(Cell::new(Default::default())),
+        );
+        #[cfg(not(feature = "no_video_interface"))]
         let video = Rc::new(RefCell::new(TestVideoInterface::default()));
+        #[cfg(not(feature = "no_video_interface"))]
         let video_clone: VideoDeviceRcRefCell = video.clone();
         let mut dma_notifier = NopDmaNotifer;
         let mut cycles_to_next_event = CYCLES_FULL_REFRESH;
@@ -659,6 +783,7 @@ mod tests {
 
         for line in 0..160 {
             println!("line = {}", line);
+            #[cfg(not(feature = "no_video_interface"))]
             assert_eq!(video.borrow().frame_counter, 0);
             assert_eq!(gpu.vcount, line);
             assert_eq!(gpu.state, GpuState::HDraw);
@@ -676,6 +801,7 @@ mod tests {
             assert_eq!(gpu.interrupt_flags.get().LCD_VCounterMatch(), false);
         }
 
+        #[cfg(not(feature = "no_video_interface"))]
         assert_eq!(video.borrow().frame_counter, 1);
 
         for line in 0..68 {
@@ -694,6 +820,7 @@ mod tests {
             update!(CYCLES_HBLANK);
         }
 
+        #[cfg(not(feature = "no_video_interface"))]
         assert_eq!(video.borrow().frame_counter, 1);
         assert_eq!(total_cycles, CYCLES_FULL_REFRESH);
 

core/src/lib.rs

@@ -40,6 +40,7 @@ pub mod arm7tdmi;
 pub mod cartridge;
 pub mod disass;
 pub mod gpu;
+mod sched;
 pub mod sound;
 pub mod sysbus;
 pub use sysbus::SysBus;

core/src/sched.rs

@@ -0,0 +1,305 @@
+use std::cell::UnsafeCell;
+use std::rc::Rc;
+
+use serde::{Deserialize, Serialize};
+
+const NUM_EVENTS: usize = 32;
+
+#[repr(u32)]
+#[derive(Serialize, Deserialize, Debug, PartialEq, Copy, Clone)]
+pub enum GpuEvent {
+    HDraw,
+    HBlank,
+    VBlankHDraw,
+    VBlankHBlank,
+}
+
+#[repr(u32)]
+#[derive(Serialize, Deserialize, Debug, PartialEq, Copy, Clone)]
+pub enum ApuEvent {
+    Psg1Generate,
+    Psg2Generate,
+    Psg3Generate,
+    Psg4Generate,
+    Sample,
+}
+
+#[repr(u32)]
+#[derive(Serialize, Deserialize, Debug, PartialEq, Copy, Clone)]
+pub enum EventType {
+    Gpu(GpuEvent),
+    Apu(ApuEvent),
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone)]
+struct Event {
+    typ: EventType,
+    /// Timestamp in cycles
+    time: usize,
+}
+
+impl Event {
+    fn new(typ: EventType, time: usize) -> Event {
+        Event { typ, time }
+    }
+
+    fn get_type(&self) -> EventType {
+        self.typ
+    }
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone)]
+pub struct Scheduler {
+    timestamp: usize,
+    events: Vec<Event>,
+}
+
+// Opt-out of runtime borrow checking by using unsafe cell
+// SAFETY: We need to make sure that the scheduler event queue is not modified while iterating it.
+#[repr(transparent)]
+#[derive(Debug)]
+pub struct SharedScheduler(Rc<UnsafeCell<Scheduler>>);
+
+impl std::ops::Deref for SharedScheduler {
+    type Target = Scheduler;
+
+    fn deref(&self) -> &Self::Target {
+        unsafe { &(*self.0.get()) }
+    }
+}
+
+impl std::ops::DerefMut for SharedScheduler {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { &mut (*self.0.get()) }
+    }
+}
+
+impl Clone for SharedScheduler {
+    fn clone(&self) -> SharedScheduler {
+        SharedScheduler(self.0.clone())
+    }
+}
+
+pub trait EventHandler {
+    /// Handle the scheduler event
+    fn handle_event(&mut self, e: EventType, extra_cycles: usize);
+}
+
+impl Scheduler {
+    pub fn new_shared() -> SharedScheduler {
+        let sched = Scheduler {
+            timestamp: 0,
+            events: Vec::with_capacity(NUM_EVENTS),
+        };
+        SharedScheduler(Rc::new(UnsafeCell::new(sched)))
+    }
+
+    pub fn make_shared(self) -> SharedScheduler {
+        SharedScheduler(Rc::new(UnsafeCell::new(self)))
+    }
+
+    pub fn schedule(&mut self, typ: EventType, cycles: usize) {
+        let event = Event::new(typ, self.timestamp + cycles);
+        let idx = self
+            .events
+            .binary_search_by(|e| e.time.cmp(&event.time))
+            .unwrap_or_else(|x| x);
+        self.events.insert(idx, event);
+    }
+
+    pub fn add_gpu_event(&mut self, e: GpuEvent, cycles: usize) {
+        self.schedule(EventType::Gpu(e), cycles);
+    }
+
+    pub fn add_apu_event(&mut self, e: ApuEvent, cycles: usize) {
+        self.schedule(EventType::Apu(e), cycles);
+    }
+
+    pub fn run<H: EventHandler>(&mut self, cycles: usize, handler: &mut H) {
+        let run_to = self.timestamp + cycles;
+        self.timestamp = run_to;
+
+        while self.events.len() > 0 {
+            if run_to >= self.events[0].time {
+                let event = self.events.remove(0);
+                handler.handle_event(event.get_type(), run_to - event.time);
+            } else {
+                return;
+            }
+        }
+    }
+
+    pub fn get_cycles_to_next_event(&self) -> usize {
+        assert_ne!(self.events.len(), 0);
+        self.events[0].time - self.timestamp
+    }
+
+    #[allow(unused)]
+    fn is_empty(&self) -> bool {
+        self.events.is_empty()
+    }
+}
+
+#[cfg(test)]
+mod test {
+
+    use super::*;
+
+    /// Some usecase example where a struct holds the scheduler
+    struct Holder {
+        sched: SharedScheduler,
+        event_bitmask: u32,
+    }
+
+    const BIT_GPU_VBLANKHDRAW: u32 = 1 << 0;
+    const BIT_APU_PSG1GENERATE: u32 = 1 << 1;
+    const BIT_APU_PSG2GENERATE: u32 = 1 << 2;
+    const BIT_APU_PSG3GENERATE: u32 = 1 << 3;
+    const BIT_APU_PSG4GENERATE: u32 = 1 << 4;
+    const BIT_APU_SAMPLE: u32 = 1 << 5;
+
+    #[inline]
+    fn get_event_bit(e: EventType) -> u32 {
+        match e {
+            EventType::Gpu(GpuEvent::VBlankHDraw) => BIT_GPU_VBLANKHDRAW,
+            EventType::Apu(ApuEvent::Psg1Generate) => BIT_APU_PSG1GENERATE,
+            EventType::Apu(ApuEvent::Psg2Generate) => BIT_APU_PSG2GENERATE,
+            EventType::Apu(ApuEvent::Psg3Generate) => BIT_APU_PSG3GENERATE,
+            EventType::Apu(ApuEvent::Psg4Generate) => BIT_APU_PSG4GENERATE,
+            EventType::Apu(ApuEvent::Sample) => BIT_APU_SAMPLE,
+            _ => unimplemented!("unsupported event for this test"),
+        }
+    }
+
+    impl Holder {
+        fn new() -> Holder {
+            Holder {
+                sched: Scheduler::new_shared(),
+                event_bitmask: 0,
+            }
+        }
+
+        fn is_event_done(&self, e: EventType) -> bool {
+            (self.event_bitmask & get_event_bit(e)) != 0
+        }
+    }
+
+    impl EventHandler for Holder {
+        fn handle_event(&mut self, e: EventType, extra_cycles: usize) {
+            println!("[holder] got event {:?} extra_cycles {}", e, extra_cycles);
+            self.event_bitmask |= get_event_bit(e);
+        }
+    }
+
+    #[test]
+    fn test_scheduler() {
+        let mut holder = Holder::new();
+
+        // clone the sched so we get a reference that is not owned by the holder
+        // SAFETY: since the SharedScheduler is built upon an UnsafeCell instead of RefCell, we are sacrificing runtime safety checks for performance.
+        //  It is safe since the events iteration allows the EventHandler to modify the queue.
+
+        let mut sched = holder.sched.clone();
+        holder
+            .sched
+            .schedule(EventType::Gpu(GpuEvent::VBlankHDraw), 240);
+        holder
+            .sched
+            .schedule(EventType::Apu(ApuEvent::Psg1Generate), 60);
+        holder.sched.schedule(EventType::Apu(ApuEvent::Sample), 512);
+        holder
+            .sched
+            .schedule(EventType::Apu(ApuEvent::Psg2Generate), 13);
+        holder
+            .sched
+            .schedule(EventType::Apu(ApuEvent::Psg4Generate), 72);
+
+        println!("all events");
+        for e in sched.events.iter() {
+            let typ = e.get_type();
+            println!("{:?}", typ);
+        }
+
+        macro_rules! run_for {
+            ($cycles:expr) => {
+                println!("running the scheduler for {} cycles", $cycles);
+                sched.run($cycles, &mut holder);
+                if (!sched.is_empty()) {
+                    println!(
+                        "cycles for next event: {}",
+                        sched.get_cycles_to_next_event()
+                    );
+                }
+            };
+        }
+
+        run_for!(100);
+
+        assert_eq!(
+            holder.is_event_done(EventType::Apu(ApuEvent::Psg1Generate)),
+            true
+        );
+        assert_eq!(
+            holder.is_event_done(EventType::Apu(ApuEvent::Psg2Generate)),
+            true
+        );
+        assert_eq!(
+            holder.is_event_done(EventType::Apu(ApuEvent::Psg4Generate)),
+            true
+        );
+        assert_eq!(
+            holder.is_event_done(EventType::Apu(ApuEvent::Sample)),
+            false
+        );
+        assert_eq!(
+            holder.is_event_done(EventType::Gpu(GpuEvent::VBlankHDraw)),
+            false
+        );
+
+        run_for!(100);
+
+        assert_eq!(
+            holder.is_event_done(EventType::Gpu(GpuEvent::VBlankHDraw)),
+            false
+        );
+        assert_eq!(
+            holder.is_event_done(EventType::Apu(ApuEvent::Sample)),
+            false
+        );
+
+        run_for!(100);
+
+        assert_eq!(
+            holder.is_event_done(EventType::Gpu(GpuEvent::VBlankHDraw)),
+            true
+        );
+        assert_eq!(
+            holder.is_event_done(EventType::Apu(ApuEvent::Sample)),
+            false
+        );
+
+        run_for!(211);
+
+        assert_eq!(
+            holder.is_event_done(EventType::Apu(ApuEvent::Sample)),
+            false
+        );
+
+        run_for!(1);
+
+        assert_eq!(holder.is_event_done(EventType::Apu(ApuEvent::Sample)), true);
+
+        println!("all events (holder)");
+        for e in holder.sched.events.iter() {
+            let typ = e.get_type();
+            println!("{:?}", typ);
+        }
+
+        println!("all events (cloned again)");
+        let sched_cloned = holder.sched.clone();
+        for e in sched_cloned.events.iter() {
+            let typ = e.get_type();
+            println!("{:?}", typ);
+        }
+    }
+}

core/src/sound/mod.rs

@@ -6,6 +6,7 @@ use serde::{Deserialize, Serialize};
 
 use super::dma::DmaController;
 use super::iodev::consts::*;
+use super::sched::*;
 
 use crate::{AudioInterface, StereoSample};
 
@@ -62,6 +63,10 @@ type AudioDeviceRcRefCell = Rc<RefCell<dyn AudioInterface>>;
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct SoundController {
+    #[serde(skip)]
+    #[serde(default = "Scheduler::new_shared")]
+    scheduler: SharedScheduler,
+
     cycles: usize, // cycles count when we last provided a new sample.
 
     mse: bool,
@@ -101,9 +106,13 @@ pub struct SoundController {
 }
 
 impl SoundController {
-    pub fn new(audio_device_sample_rate: f32) -> SoundController {
+    pub fn new(mut scheduler: SharedScheduler, audio_device_sample_rate: f32) -> SoundController {
         let resampler = CosineResampler::new(32768_f32, audio_device_sample_rate);
+        let cycles_per_sample = 512;
+        scheduler.schedule(EventType::Apu(ApuEvent::Sample), cycles_per_sample);
         SoundController {
+            scheduler,
+            cycles_per_sample,
             cycles: 0,
             mse: false,
             left_volume: 0,
@@ -127,7 +136,6 @@ impl SoundController {
             sqr1_cur_vol: 0,
             sound_bias: 0x200,
             sample_rate: 32_768f32,
-            cycles_per_sample: 512,
             dma_sound: [Default::default(), Default::default()],
 
             resampler: resampler,
@@ -135,6 +143,10 @@ impl SoundController {
         }
     }
 
+    pub fn set_scheduler(&mut self, scheduler: SharedScheduler) {
+        self.scheduler = scheduler;
+    }
+
     pub fn handle_read(&self, io_addr: u32) -> u16 {
         let value = match io_addr {
             REG_SOUNDCNT_X => cbit(7, self.mse),
@@ -277,6 +289,11 @@ impl SoundController {
                     self.resampler.in_freq = self.sample_rate;
                 }
                 self.cycles_per_sample = 512 >> resolution;
+                info!(
+                    "bias - setting sample frequency to {}hz",
+                    self.cycles_per_sample
+                );
+                // TODO this will not affect the currently scheduled sample event
             }
 
             _ => {
@@ -317,18 +334,8 @@ impl SoundController {
         }
     }
 
-    pub fn update(
+    #[inline]
-        &mut self,
+    fn on_sample(&mut self, extra_cycles: usize, audio_device: &AudioDeviceRcRefCell) {
-        cycles: usize,
-        cycles_to_next_event: &mut usize,
-        audio_device: &AudioDeviceRcRefCell,
-    ) {
-        self.cycles += cycles;
-        while self.cycles >= self.cycles_per_sample {
-            self.cycles -= self.cycles_per_sample;
-
-            // time to push a new sample!
-
         let mut sample = [0f32; 2];
 
         for channel in 0..=1 {
@@ -354,9 +361,20 @@ impl SoundController {
                 (right.round() as i16) * (std::i16::MAX / 512),
             ]);
         });
+
+        self.scheduler
+            .add_apu_event(ApuEvent::Sample, self.cycles_per_sample - extra_cycles);
     }
-        if self.cycles_per_sample < *cycles_to_next_event {
+
-            *cycles_to_next_event = self.cycles_per_sample;
+    pub fn on_event(
+        &mut self,
+        event: ApuEvent,
+        extra_cycles: usize,
+        audio_device: &AudioDeviceRcRefCell,
+    ) {
+        match event {
+            ApuEvent::Sample => self.on_sample(extra_cycles, audio_device),
+            _ => debug!("got {:?} event", event),
         }
     }
 }