fix(apu): don't spin if ringbuf is full

src/apu.rs

@@ -131,10 +131,11 @@ impl Apu {
 
         self.div_prev = Some(bit_5);
 
-        if let Some(ref mut prod) = self.prod {
         if self.sample_counter >= SM83_CLOCK_SPEED {
             self.sample_counter %= SM83_CLOCK_SPEED;
 
+            if let Some(ref mut prod) = self.prod {
+                if prod.two_available() {
                     // Sample the APU
                     let ch1_amplitude = self.ch1.amplitude();
                     let ch1_left = self.ctrl.output.ch1_left() as u8 as f32 * ch1_amplitude;
@@ -161,6 +162,7 @@ impl Apu {
                 }
             }
         }
+    }
 
     pub fn set_producer(&mut self, prod: SampleProducer<f32>) {
         self.prod = Some(prod);

src/apu/gen.rs

@@ -47,6 +47,11 @@ impl<T> SampleProducer<T> {
     pub(crate) fn is_full(&self) -> bool {
         self.inner.is_full()
     }
+
+    #[inline]
+    pub(crate) fn two_available(&self) -> bool {
+        self.inner.slots() > 2
+    }
 }
 
 impl<T> std::fmt::Debug for SampleProducer<T> {

src/cpu.rs

@@ -117,16 +117,9 @@ impl Cpu {
             }
         };
 
-        // TODO: With how we currently handle audio
-        // this --while being correct-- incurs a performance penalty
-        // as our emu is audio-bound.
-        let mut elapsed = 0x00;
         let pending: u32 = cycles.into();
-        while elapsed < pending {
-            if !self.bus.apu().is_full() {
+        for _ in 0..pending {
             self.bus.clock();
-                elapsed += 1;
-            }
         }
 
         self.handle_interrupts();

src/main.rs

@@ -112,7 +112,7 @@ fn main() -> Result<()> {
 
             if cycle_count >= gb::emu::CYCLES_IN_FRAME {
                 // Draw Frame
-                cycle_count = Cycle::new(0);
+                cycle_count %= gb::emu::CYCLES_IN_FRAME;
 
                 gb::emu::draw(game_boy.ppu(), pixels.get_frame());
                 window.request_redraw();