fix: audio thread now uses a separate stack from the main threadaudio

1 files changed, 23 insertions, 0 deletions

diff --git a/src/wasm.zig b/src/wasm.zig
index 92d8c36..98b1fff 100644
--- a/src/wasm.zig
+++ b/src/wasm.zig
@@ -76,12 +76,18 @@ fn dummyAudioCallback(_: *const AudioInfo) void {}
 const AudioCallbackFn = fn (*const AudioInfo) void;
 const audioCallback: AudioCallbackFn = if (@hasDecl(root, "audioCallback")) root.audioCallback else dummyAudioCallback;
 
+const stack_size = 16 * 1024 * 1024;
+const stack_offset = std.mem.alignForward(usize, std.wasm.page_size, 16);
+
 const max_channels = 8;
 const max_samples_per_call = 256;
 var samples: [max_samples_per_call]f32 = [1]f32{0} ** max_samples_per_call;
 var info: AudioInfo = undefined;
 var write_slices: [max_channels][]f32 = undefined;
 export fn getAudioSamples(sample_rate: u32, channels: u32, samples_per_channel: u32) *const [*]f32 {
+    const og_pointer = getStackPointer();
+    const fwd = og_pointer + stack_offset;
+    setStackPointer(fwd);
     engine.assert(channels <= max_channels);
     engine.assert(channels * samples_per_channel <= max_samples_per_call);
 
@@ -98,3 +104,20 @@ export fn getAudioSamples(sample_rate: u32, channels: u32, samples_per_channel:
 
     return @ptrCast(&samples);
 }
+
+inline fn getStackPointer() [*]u8 {
+    return asm (
+        \\ global.get __stack_pointer
+        \\local.set %[stack_ptr]
+        : [stack_ptr] "=r" (-> [*]u8),
+    );
+}
+
+inline fn setStackPointer(addr: [*]u8) void {
+    asm volatile (
+        \\ local.get %[ptr]
+        \\ global.set __stack_pointer
+        :
+        : [ptr] "r" (addr),
+    );
+}