From a41bb0b89be052f2eb6164aa41a5c40e4228ba13 Mon Sep 17 00:00:00 2001
From: Gwilym Kuiper <gw@ilym.me>
Date: Thu, 10 Jun 2021 22:42:04 +0100
Subject: [PATCH] Have 2 buffers for left or right control

---
 agb/src/sound/mixer/hw.rs    | 17 +++++++++++++++--
 agb/src/sound/mixer/mixer.rs | 25 +++++++++++++++++--------
 2 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/agb/src/sound/mixer/hw.rs b/agb/src/sound/mixer/hw.rs
index 313e9a06..2c10275a 100644
--- a/agb/src/sound/mixer/hw.rs
+++ b/agb/src/sound/mixer/hw.rs
@@ -31,14 +31,27 @@ const DMA_CONTROL_SETTING_FOR_SOUND: u16 = {
     dest_fixed | repeat | transfer_type | dma_start_timing | enable
 };
 
-pub(super) fn enable_dma1_for_sound(sound_memory: &[i8]) {
+#[derive(Copy, Clone)]
+pub(super) enum LeftOrRight {
+    Left,
+    Right,
+}
+
+pub(super) fn enable_dma_for_sound(sound_memory: &[i8], lr: LeftOrRight) {
+    match lr {
+        LeftOrRight::Left => enable_dma1_for_sound(sound_memory),
+        LeftOrRight::Right => enable_dma2_for_sound(sound_memory),
+    }
+}
+
+fn enable_dma1_for_sound(sound_memory: &[i8]) {
     DMA1_CONTROL.set(0);
     DMA1_SOURCE_ADDR.set(sound_memory.as_ptr() as u32);
     DMA1_DEST_ADDR.set(FIFOA_DEST_ADDR);
     DMA1_CONTROL.set(DMA_CONTROL_SETTING_FOR_SOUND);
 }
 
-pub(super) fn enable_dma2_for_sound(sound_memory: &[i8]) {
+fn enable_dma2_for_sound(sound_memory: &[i8]) {
     DMA2_CONTROL.set(0);
     DMA2_SOURCE_ADDR.set(sound_memory.as_ptr() as u32);
     DMA2_DEST_ADDR.set(FIFOB_DEST_ADDR);
diff --git a/agb/src/sound/mixer/mixer.rs b/agb/src/sound/mixer/mixer.rs
index 323f7d6f..a88d0355 100644
--- a/agb/src/sound/mixer/mixer.rs
+++ b/agb/src/sound/mixer/mixer.rs
@@ -1,15 +1,18 @@
 use super::hw;
+use super::hw::LeftOrRight;
 use super::SoundChannel;
 
 pub struct Mixer {
-    buffer: MixerBuffer,
+    buffer_l: MixerBuffer,
+    buffer_r: MixerBuffer,
     channels: [Option<SoundChannel>; 16],
 }
 
 impl Mixer {
     pub(super) fn new() -> Self {
         Mixer {
-            buffer: MixerBuffer::new(),
+            buffer_l: MixerBuffer::new(LeftOrRight::Left),
+            buffer_r: MixerBuffer::new(LeftOrRight::Right),
             channels: Default::default(),
         }
     }
@@ -20,14 +23,17 @@ impl Mixer {
     }
 
     pub fn vblank(&mut self) {
-        self.buffer.swap();
-        self.buffer.clear();
+        self.buffer_l.swap();
+        self.buffer_r.swap();
+        self.buffer_l.clear();
+        self.buffer_r.clear();
 
         for channel in self.channels.iter_mut() {
             let mut has_finished = false;
 
             if let Some(some_channel) = channel {
-                self.buffer.write_channel(some_channel);
+                self.buffer_l.write_channel(some_channel);
+                self.buffer_r.write_channel(some_channel);
                 some_channel.pos += SOUND_BUFFER_SIZE;
 
                 if some_channel.pos >= some_channel.data.len() {
@@ -69,15 +75,18 @@ struct MixerBuffer {
     buffer2: [i8; SOUND_BUFFER_SIZE],
 
     buffer_1_active: bool,
+
+    lr: LeftOrRight,
 }
 
 impl MixerBuffer {
-    fn new() -> Self {
+    fn new(lr: LeftOrRight) -> Self {
         MixerBuffer {
             buffer1: [0; SOUND_BUFFER_SIZE],
             buffer2: [0; SOUND_BUFFER_SIZE],
 
             buffer_1_active: true,
+            lr,
         }
     }
 
@@ -85,9 +94,9 @@ impl MixerBuffer {
         self.buffer_1_active = !self.buffer_1_active;
 
         if self.buffer_1_active {
-            hw::enable_dma1_for_sound(&self.buffer1);
+            hw::enable_dma_for_sound(&self.buffer1, self.lr);
         } else {
-            hw::enable_dma1_for_sound(&self.buffer2);
+            hw::enable_dma_for_sound(&self.buffer2, self.lr);
         }
     }