From d38fea7f7a7d67519f6d954ed4e6e6b850e74ef3 Mon Sep 17 00:00:00 2001
From: Gwilym Inzani <email@gwilym.dev>
Date: Fri, 14 Jul 2023 22:50:11 +0100
Subject: [PATCH] Pass the buffer size rather than using the global variable
 for it

---
 agb/src/sound/mixer/mixer.s     | 20 ++++++--------------
 agb/src/sound/mixer/sw_mixer.rs | 20 ++++++++------------
 2 files changed, 14 insertions(+), 26 deletions(-)

diff --git a/agb/src/sound/mixer/mixer.s b/agb/src/sound/mixer/mixer.s
index 1f9db61b..9605e800 100644
--- a/agb/src/sound/mixer/mixer.s
+++ b/agb/src/sound/mixer/mixer.s
@@ -1,9 +1,3 @@
-.section .iwram.buffer_size
-    .global agb_rs__buffer_size
-    .balign 4
-agb_rs__buffer_size:
-    .word 0
-
 .macro mixer_add fn_name:req is_first:req
 agb_arm_func \fn_name
     @ Arguments
@@ -12,8 +6,9 @@ agb_arm_func \fn_name
     @ r2 - playback speed (usize fixnum with 8 bits)
     @ r3 - amount to modify the left channel by (u16 fixnum with 4 bits)
     @ stack position 1 - amount to modify the right channel by (u16 fixnum with 4 bits)
+    @ stack position 2 - the buffer_size (usize)
     @
-    @ The sound buffer must be SOUND_BUFFER_SIZE * 2 in size = 176 * 2
+    @ The sound buffer must be buffer_size * 2 in size
     push {{r4-r8}}
 
     ldr r7, [sp, #20]        @ load the right channel modification amount into r7
@@ -25,9 +20,7 @@ agb_arm_func \fn_name
     orr r7, r7, r3, lsl #16   @ r7 now is the left channel followed by the right channel modifications.
 
     mov r5, #0                   @ current index we're reading from
-    ldr r8, =agb_rs__buffer_size @ the number of steps left
-    ldr r8, [r8]
-
+    ldr r8, [sp, #24]
 
 1:
 .rept 4
@@ -69,8 +62,7 @@ agb_arm_func \fn_name
     sub r3, r3, #1
 
     mov r5, #0                   @ current index we're reading from
-    ldr r8, =agb_rs__buffer_size @ the number of steps left
-    ldr r8, [r8]
+    ldr r8, [sp, #24]           @ the number of steps we have left
 
 1:
 .rept 4
@@ -110,14 +102,14 @@ agb_arm_func \fn_name
     @ r0 - pointer to the data to be copied (u8 array)
     @ r1 - pointer to the sound buffer (i16 array which will alternate left and right channels, 32-bit aligned)
     @ r2 - volume to play the sound at
+    @ r3 - the buffer size
     @
     @ The sound buffer must be SOUND_BUFFER_SIZE * 2 in size = 176 * 2
     push {{r4-r11}}
 
     ldr r5, =0x00000FFF
 
-    ldr r8, =agb_rs__buffer_size
-    ldr r8, [r8]
+    mov r8, r3
 
 .macro add_stereo_sample sample_reg:req
     ldrsh r6, [r0], #2        @ load the current sound sample to r6
diff --git a/agb/src/sound/mixer/sw_mixer.rs b/agb/src/sound/mixer/sw_mixer.rs
index 9ae8e3bc..cc9b2f15 100644
--- a/agb/src/sound/mixer/sw_mixer.rs
+++ b/agb/src/sound/mixer/sw_mixer.rs
@@ -27,6 +27,7 @@ extern "C" {
         playback_speed: Num<u32, 8>,
         left_amount: Num<i16, 4>,
         right_amount: Num<i16, 4>,
+        buffer_size: usize,
     );
 
     fn agb_rs__mixer_add_first(
@@ -35,18 +36,21 @@ extern "C" {
         playback_speed: Num<u32, 8>,
         left_amount: Num<i16, 4>,
         right_amount: Num<i16, 4>,
+        buffer_size: usize,
     );
 
     fn agb_rs__mixer_add_stereo(
         sound_data: *const u8,
         sound_buffer: *mut Num<i16, 4>,
         volume: Num<i16, 4>,
+        buffer_size: usize,
     );
 
     fn agb_rs__mixer_add_stereo_first(
         sound_data: *const u8,
         sound_buffer: *mut Num<i16, 4>,
         volume: Num<i16, 4>,
+        buffer_size: usize,
     );
 
     fn agb_rs__mixer_collapse(
@@ -164,8 +168,6 @@ impl Mixer<'_> {
             })
         };
 
-        set_asm_buffer_size(frequency);
-
         let mut working_buffer =
             Vec::with_capacity_in(frequency.buffer_size() * 2, InternalAllocator);
         working_buffer.resize(frequency.buffer_size() * 2, 0.into());
@@ -322,16 +324,6 @@ impl Mixer<'_> {
     }
 }
 
-fn set_asm_buffer_size(frequency: Frequency) {
-    extern "C" {
-        static mut agb_rs__buffer_size: usize;
-    }
-
-    unsafe {
-        agb_rs__buffer_size = frequency.buffer_size();
-    }
-}
-
 struct SoundBuffer(Box<[i8], InternalAllocator>);
 
 impl SoundBuffer {
@@ -452,6 +444,7 @@ impl MixerBuffer {
                             channel.data.as_ptr().add(channel.pos.floor() as usize),
                             working_buffer.as_mut_ptr(),
                             channel.volume,
+                            self.frequency.buffer_size(),
                         );
                     }
                 } else {
@@ -465,6 +458,7 @@ impl MixerBuffer {
                             playback_speed,
                             left_amount,
                             right_amount,
+                            self.frequency.buffer_size(),
                         );
                     }
                 }
@@ -485,6 +479,7 @@ impl MixerBuffer {
                             channel.data.as_ptr().add(channel.pos.floor() as usize),
                             working_buffer.as_mut_ptr(),
                             channel.volume,
+                            self.frequency.buffer_size(),
                         );
                     }
                 } else {
@@ -498,6 +493,7 @@ impl MixerBuffer {
                             playback_speed,
                             left_amount,
                             right_amount,
+                            self.frequency.buffer_size(),
                         );
                     }
                 }