tmp: removed audio resampler

README.md

@@ -77,7 +77,7 @@ arm7wrestler GBA Fixed | [destoer](https://github.com/destoer)
 
 ## Compiling
 
-Most recently built on Zig [v0.11.0-dev.144+892fb0fc8](https://github.com/ziglang/zig/tree/892fb0fc8)
+Most recently built on Zig [0.11.0-dev.368+1829b6eab](https://github.com/ziglang/zig/tree/1829b6eab)
 
 ### Dependencies
 

build.zig

@@ -1,7 +1,15 @@
 const std = @import("std");
+const builtin = @import("builtin");
 const Sdk = @import("lib/SDL.zig/Sdk.zig");
 
 pub fn build(b: *std.build.Builder) void {
+    // Minimum Zig Version
+    const min_ver = std.SemanticVersion.parse("0.11.0-dev.323+30eb2a175") catch return; // https://github.com/ziglang/zig/commit/30eb2a175
+    if (builtin.zig_version.order(min_ver).compare(.lt)) {
+        std.log.err("{s}", .{b.fmt("Zig v{} does not meet the minimum version requirement. (Zig v{})", .{ builtin.zig_version, min_ver })});
+        std.os.exit(1);
+    }
+
     // Standard target options allows the person running `zig build` to choose
     // what target to build for. Here we do not override the defaults, which
     // means any target is allowed, and the default is native. Other options

src/core/apu.zig

@@ -15,12 +15,10 @@ const SoundFifo = std.fifo.LinearFifo(u8, .{ .Static = 0x20 });
 const getHalf = util.getHalf;
 const setHalf = util.setHalf;
 const intToBytes = util.intToBytes;
+const RingBuffer = util.RingBuffer;
 
 const log = std.log.scoped(.APU);
 
-pub const host_rate = @import("../platform.zig").sample_rate;
-pub const host_format = @import("../platform.zig").sample_format;
-
 pub fn read(comptime T: type, apu: *const Apu, addr: u32) ?T {
     const byte_addr = @truncate(u8, addr);
 
@@ -246,17 +244,20 @@ pub const Apu = struct {
 
     sampling_cycle: u2,
 
-    stream: *SDL.SDL_AudioStream,
+    sample_queue: RingBuffer(u16),
     sched: *Scheduler,
 
     fs: FrameSequencer,
     capacitor: f32,
 
-    is_buffer_full: bool,
-
     pub const Tick = enum { Length, Envelope, Sweep };
 
     pub fn init(sched: *Scheduler) Self {
+        const NUM_CHANNELS: usize = 2;
+
+        const allocator = std.heap.c_allocator;
+        const sample_buf = allocator.alloc(u16, 0x800 * NUM_CHANNELS) catch @panic("failed to allocate sample buffer");
+
         const apu: Self = .{
             .ch1 = ToneSweep.init(sched),
             .ch2 = Tone.init(sched),
@@ -271,12 +272,11 @@ pub const Apu = struct {
             .bias = .{ .raw = 0x0200 },
 
             .sampling_cycle = 0b00,
-            .stream = SDL.SDL_NewAudioStream(SDL.AUDIO_U16, 2, 1 << 15, host_format, 2, host_rate).?,
+            .sample_queue = RingBuffer(u16).init(sample_buf),
             .sched = sched,
 
             .capacitor = 0,
             .fs = FrameSequencer.init(),
-            .is_buffer_full = false,
         };
 
         sched.push(.SampleAudio, apu.interval());
@@ -370,11 +370,6 @@ pub const Apu = struct {
     pub fn sampleAudio(self: *Self, late: u64) void {
         self.sched.push(.SampleAudio, self.interval() -| late);
 
-        // Whether the APU is busy or not is determined  by the main loop in emu.zig
-        // This should only ever be true (because this side of the emu is single threaded)
-        // When audio sync is disaabled
-        if (self.is_buffer_full) return;
-
         var left: i16 = 0;
         var right: i16 = 0;
 
@@ -430,23 +425,7 @@ pub const Apu = struct {
         const ext_left = (clamped_left << 5) | (clamped_left >> 6);
         const ext_right = (clamped_right << 5) | (clamped_right >> 6);
 
-        if (self.sampling_cycle != self.bias.sampling_cycle.read()) self.replaceSDLResampler();
-
-        _ = SDL.SDL_AudioStreamPut(self.stream, &[2]u16{ ext_left, ext_right }, 2 * @sizeOf(u16));
-    }
-
-    fn replaceSDLResampler(self: *Self) void {
-        @setCold(true);
-        const sample_rate = Self.sampleRate(self.bias.sampling_cycle.read());
-        log.info("Sample Rate changed from {}Hz to {}Hz", .{ Self.sampleRate(self.sampling_cycle), sample_rate });
-
-        // Sampling Cycle (Sample Rate) changed, Craete a new SDL Audio Resampler
-        // FIXME: Replace SDL's Audio Resampler with either a custom or more reliable one
-        const old_stream = self.stream;
-        defer SDL.SDL_FreeAudioStream(old_stream);
-
-        self.sampling_cycle = self.bias.sampling_cycle.read();
-        self.stream = SDL.SDL_NewAudioStream(SDL.AUDIO_U16, 2, @intCast(c_int, sample_rate), host_format, 2, host_rate).?;
+        self.sample_queue.push(ext_left, ext_right) catch {};
     }
 
     fn interval(self: *const Self) u64 {

src/core/bus/dma.zig

@@ -5,7 +5,7 @@ const DmaControl = @import("io.zig").DmaControl;
 const Bus = @import("../Bus.zig");
 const Arm7tdmi = @import("../cpu.zig").Arm7tdmi;
 
-pub const DmaTuple = std.meta.Tuple(&[_]type{ DmaController(0), DmaController(1), DmaController(2), DmaController(3) });
+pub const DmaTuple = struct { DmaController(0), DmaController(1), DmaController(2), DmaController(3) };
 const log = std.log.scoped(.DmaTransfer);
 
 const getHalf = util.getHalf;

src/core/bus/io.zig

@@ -24,14 +24,14 @@ pub const Io = struct {
     postflg: PostFlag,
     waitcnt: WaitControl,
     haltcnt: HaltControl,
-    keyinput: KeyInput,
+    keyinput: AtomicKeyInput,
 
     pub fn init() Self {
         return .{
             .ime = false,
             .ie = .{ .raw = 0x0000 },
             .irq = .{ .raw = 0x0000 },
-            .keyinput = .{ .raw = 0x03FF },
+            .keyinput = AtomicKeyInput.init(.{ .raw = 0x03FF }),
             .waitcnt = .{ .raw = 0x0000_0000 }, // Bit 15 == 0 for GBA
             .postflg = .FirstBoot,
             .haltcnt = .Execute,
@@ -92,7 +92,7 @@ pub fn read(bus: *const Bus, comptime T: type, address: u32) ?T {
             0x0400_0128 => util.io.read.todo(log, "Read {} from SIOCNT", .{T}),
 
             // Keypad Input
-            0x0400_0130 => bus.io.keyinput.raw,
+            0x0400_0130 => bus.io.keyinput.load(.Monotonic).raw,
 
             // Serial Communication 2
             0x0400_0134 => util.io.read.todo(log, "Read {} from RCNT", .{T}),
@@ -376,6 +376,31 @@ const KeyInput = extern union {
     raw: u16,
 };
 
+const AtomicKeyInput = struct {
+    const Self = @This();
+    const Ordering = std.atomic.Ordering;
+
+    inner: KeyInput,
+
+    pub fn init(value: KeyInput) Self {
+        return .{ .inner = value };
+    }
+
+    pub inline fn load(self: *const Self, comptime ordering: Ordering) KeyInput {
+        return .{ .raw = switch (ordering) {
+            .AcqRel, .Release => @compileError("not supported for atomic loads"),
+            else => @atomicLoad(u16, &self.inner.raw, ordering),
+        } };
+    }
+
+    pub inline fn store(self: *Self, value: u16, comptime ordering: Ordering) void {
+        switch (ordering) {
+            .AcqRel, .Acquire => @compileError("not supported for atomic stores"),
+            else => @atomicStore(u16, &self.inner.raw, value, ordering),
+        }
+    }
+};
+
 // Read / Write
 pub const BackgroundControl = extern union {
     priority: Bitfield(u16, 0, 2),

src/core/bus/timer.zig

@@ -5,7 +5,7 @@ const TimerControl = @import("io.zig").TimerControl;
 const Scheduler = @import("../scheduler.zig").Scheduler;
 const Arm7tdmi = @import("../cpu.zig").Arm7tdmi;
 
-pub const TimerTuple = std.meta.Tuple(&[_]type{ Timer(0), Timer(1), Timer(2), Timer(3) });
+pub const TimerTuple = struct { Timer(0), Timer(1), Timer(2), Timer(3) };
 const log = std.log.scoped(.Timer);
 
 const getHalf = util.getHalf;

src/core/emu.zig

@@ -5,6 +5,7 @@ const config = @import("../config.zig");
 const Scheduler = @import("scheduler.zig").Scheduler;
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 const FpsTracker = @import("../util.zig").FpsTracker;
+const RingBuffer = @import("../util.zig").RingBuffer;
 
 const Timer = std.time.Timer;
 const Atomic = std.atomic.Atomic;
@@ -56,9 +57,9 @@ fn inner(comptime kind: RunKind, audio_sync: bool, quit: *Atomic(bool), schedule
         .Unlimited, .UnlimitedFPS => {
             log.info("Emulation w/out video sync", .{});
 
-            while (!quit.load(.SeqCst)) {
+            while (!quit.load(.Monotonic)) {
                 runFrame(scheduler, cpu);
-                audioSync(audio_sync, cpu.bus.apu.stream, &cpu.bus.apu.is_buffer_full);
+                audioSync(audio_sync, &cpu.bus.apu.sample_queue);
 
                 if (kind == .UnlimitedFPS) tracker.?.tick();
             }
@@ -68,7 +69,7 @@ fn inner(comptime kind: RunKind, audio_sync: bool, quit: *Atomic(bool), schedule
             var timer = Timer.start() catch @panic("failed to initalize std.timer.Timer");
             var wake_time: u64 = frame_period;
 
-            while (!quit.load(.SeqCst)) {
+            while (!quit.load(.Monotonic)) {
                 runFrame(scheduler, cpu);
                 const new_wake_time = videoSync(&timer, wake_time);
 
@@ -77,7 +78,7 @@ fn inner(comptime kind: RunKind, audio_sync: bool, quit: *Atomic(bool), schedule
                 // the amount of time needed for audio to catch up rather than
                 // our expected wake-up time
 
-                audioSync(audio_sync, cpu.bus.apu.stream, &cpu.bus.apu.is_buffer_full);
+                audioSync(audio_sync, &cpu.bus.apu.sample_queue);
                 if (!audio_sync) spinLoop(&timer, wake_time);
                 wake_time = new_wake_time;
 
@@ -104,22 +105,13 @@ pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi) void {
     }
 }
 
-fn audioSync(audio_sync: bool, stream: *SDL.SDL_AudioStream, is_buffer_full: *bool) void {
+fn audioSync(audio_sync: bool, sample_queue: *RingBuffer(u16)) void {
     comptime std.debug.assert(@import("../platform.zig").sample_format == SDL.AUDIO_U16);
-    const sample_size = 2 * @sizeOf(u16);
-    const max_buf_size: c_int = 0x400;
+    // const sample_size = 2 * @sizeOf(u16);
+    // const max_buf_size: c_int = 0x400;
 
-    // Determine whether the APU is busy right at this moment
-    var still_full: bool = SDL.SDL_AudioStreamAvailable(stream) > sample_size * if (is_buffer_full.*) max_buf_size >> 1 else max_buf_size;
-    defer is_buffer_full.* = still_full; // Update APU Busy status right before exiting scope
-
-    // If Busy is false, there's no need to sync here
-    if (!still_full) return;
-
-    while (true) {
-        still_full = SDL.SDL_AudioStreamAvailable(stream) > sample_size * max_buf_size >> 1;
-        if (!audio_sync or !still_full) break;
-    }
+    _ = audio_sync;
+    _ = sample_queue;
 }
 
 fn videoSync(timer: *Timer, wake_time: u64) u64 {

src/core/ppu.zig

@@ -1464,7 +1464,7 @@ const FrameBuffer = struct {
 
     layers: [2][]u8,
     buf: []u8,
-    current: u1,
+    current: std.atomic.Atomic(u8),
 
     allocator: Allocator,
 
@@ -1483,7 +1483,7 @@ const FrameBuffer = struct {
             // Front and Back Framebuffers
             .layers = [_][]u8{ buf[0..][0..framebuf_len], buf[framebuf_len..][0..framebuf_len] },
             .buf = buf,
-            .current = 0,
+            .current = std.atomic.Atomic(u8).init(0),
 
             .allocator = allocator,
         };
@@ -1495,10 +1495,12 @@ const FrameBuffer = struct {
     }
 
     pub fn swap(self: *Self) void {
-        self.current = ~self.current;
+        _ = self.current.fetchXor(1, .Release); // fetchNot(.Release)
     }
 
     pub fn get(self: *Self, comptime dev: Device) []u8 {
-        return self.layers[if (dev == .Emulator) self.current else ~self.current];
+        const current = @intCast(u1, self.current.load(.Acquire));
+
+        return self.layers[if (dev == .Emulator) current else ~current];
     }
 };

src/main.zig

@@ -87,7 +87,7 @@ pub fn main() void {
         cpu.fastBoot();
     }
 
-    var gui = Gui.init(&bus.pak.title, &bus.apu, width, height);
+    var gui = Gui.init(&bus.pak.title, &bus.apu, width, height) catch |e| exitln("failed to init gui: {}", .{e});
     defer gui.deinit();
 
     gui.run(&cpu, &scheduler) catch |e| exitln("failed to run gui thread: {}", .{e});

src/platform.zig

@@ -12,10 +12,10 @@ const FpsTracker = @import("util.zig").FpsTracker;
 const gba_width = @import("core/ppu.zig").width;
 const gba_height = @import("core/ppu.zig").height;
 
-pub const sample_rate = 1 << 15;
+pub const sample_rate = 1 << 16;
 pub const sample_format = SDL.AUDIO_U16;
 
-const default_title: []const u8 = "ZBA";
+const default_title = "ZBA";
 
 pub const Gui = struct {
     const Self = @This();
@@ -44,7 +44,7 @@ pub const Gui = struct {
 
     program_id: gl.GLuint,
 
-    pub fn init(title: *const [12]u8, apu: *Apu, width: i32, height: i32) Self {
+    pub fn init(title: *const [12]u8, apu: *Apu, width: i32, height: i32) !Self {
         if (SDL.SDL_Init(SDL.SDL_INIT_VIDEO | SDL.SDL_INIT_EVENTS | SDL.SDL_INIT_AUDIO) < 0) panic();
         if (SDL.SDL_GL_SetAttribute(SDL.SDL_GL_CONTEXT_PROFILE_MASK, SDL.SDL_GL_CONTEXT_PROFILE_CORE) < 0) panic();
         if (SDL.SDL_GL_SetAttribute(SDL.SDL_GL_CONTEXT_MAJOR_VERSION, 3) < 0) panic();
@@ -53,7 +53,7 @@ pub const Gui = struct {
         const win_scale = @intCast(c_int, config.config().host.win_scale);
 
         const window = SDL.SDL_CreateWindow(
-            default_title.ptr,
+            default_title,
             SDL.SDL_WINDOWPOS_CENTERED,
             SDL.SDL_WINDOWPOS_CENTERED,
             @as(c_int, width * win_scale),
@@ -64,10 +64,10 @@ pub const Gui = struct {
         const ctx = SDL.SDL_GL_CreateContext(window) orelse panic();
         if (SDL.SDL_GL_MakeCurrent(window, ctx) < 0) panic();
 
-        gl.load(ctx, Self.glGetProcAddress) catch @panic("gl.load failed");
+        try gl.load(ctx, Self.glGetProcAddress);
         if (SDL.SDL_GL_SetSwapInterval(@boolToInt(config.config().host.vsync)) < 0) panic();
 
-        const program_id = compileShaders();
+        const program_id = try compileShaders();
 
         return Self{
             .window = window,
@@ -78,7 +78,7 @@ pub const Gui = struct {
         };
     }
 
-    fn compileShaders() gl.GLuint {
+    fn compileShaders() !gl.GLuint {
         // TODO: Panic on Shader Compiler Failure + Error Message
         const vert_shader = @embedFile("shader/pixelbuf.vert");
         const frag_shader = @embedFile("shader/pixelbuf.frag");
@@ -89,12 +89,16 @@ pub const Gui = struct {
         gl.shaderSource(vs, 1, &[_][*c]const u8{vert_shader}, 0);
         gl.compileShader(vs);
 
+        if (!shader.didCompile(vs)) return error.VertexCompileError;
+
         const fs = gl.createShader(gl.FRAGMENT_SHADER);
         defer gl.deleteShader(fs);
 
         gl.shaderSource(fs, 1, &[_][*c]const u8{frag_shader}, 0);
         gl.compileShader(fs);
 
+        if (!shader.didCompile(fs)) return error.FragmentCompileError;
+
         const program = gl.createProgram();
         gl.attachShader(program, vs);
         gl.attachShader(program, fs);
@@ -104,7 +108,7 @@ pub const Gui = struct {
     }
 
     // Returns the VAO ID since it's used in run()
-    fn generateBuffers() [3]c_uint {
+    fn generateBuffers() struct { c_uint, c_uint, c_uint } {
         var vao_id: c_uint = undefined;
         var vbo_id: c_uint = undefined;
         var ebo_id: c_uint = undefined;
@@ -154,13 +158,21 @@ pub const Gui = struct {
         var quit = std.atomic.Atomic(bool).init(false);
         var tracker = FpsTracker.init();
 
+        var buffer_ids = Self.generateBuffers();
+        defer {
+            gl.deleteBuffers(1, &buffer_ids[2]); // EBO
+            gl.deleteBuffers(1, &buffer_ids[1]); // VBO
+            gl.deleteVertexArrays(1, &buffer_ids[0]); // VAO
+        }
+        const vao_id = buffer_ids[0];
+
+        const tex_id = Self.generateTexture(cpu.bus.ppu.framebuf.get(.Renderer));
+        defer gl.deleteTextures(1, &tex_id);
+
         const thread = try std.Thread.spawn(.{}, emu.run, .{ &quit, scheduler, cpu, &tracker });
         defer thread.join();
 
-        var title_buf: [0x100]u8 = [_]u8{0} ** 0x100;
-
-        const vao_id = Self.generateBuffers()[0];
-        _ = Self.generateTexture(cpu.bus.ppu.framebuf.get(.Renderer));
+        var title_buf: [0x100]u8 = undefined;
 
         emu_loop: while (true) {
             var event: SDL.SDL_Event = undefined;
@@ -168,54 +180,50 @@ pub const Gui = struct {
                 switch (event.type) {
                     SDL.SDL_QUIT => break :emu_loop,
                     SDL.SDL_KEYDOWN => {
-                        const io = &cpu.bus.io;
                         const key_code = event.key.keysym.sym;
+                        var keyinput = cpu.bus.io.keyinput.load(.Monotonic);
 
                         switch (key_code) {
-                            SDL.SDLK_UP => io.keyinput.up.unset(),
-                            SDL.SDLK_DOWN => io.keyinput.down.unset(),
-                            SDL.SDLK_LEFT => io.keyinput.left.unset(),
-                            SDL.SDLK_RIGHT => io.keyinput.right.unset(),
-                            SDL.SDLK_x => io.keyinput.a.unset(),
-                            SDL.SDLK_z => io.keyinput.b.unset(),
-                            SDL.SDLK_a => io.keyinput.shoulder_l.unset(),
-                            SDL.SDLK_s => io.keyinput.shoulder_r.unset(),
-                            SDL.SDLK_RETURN => io.keyinput.start.unset(),
-                            SDL.SDLK_RSHIFT => io.keyinput.select.unset(),
+                            SDL.SDLK_UP => keyinput.up.unset(),
+                            SDL.SDLK_DOWN => keyinput.down.unset(),
+                            SDL.SDLK_LEFT => keyinput.left.unset(),
+                            SDL.SDLK_RIGHT => keyinput.right.unset(),
+                            SDL.SDLK_x => keyinput.a.unset(),
+                            SDL.SDLK_z => keyinput.b.unset(),
+                            SDL.SDLK_a => keyinput.shoulder_l.unset(),
+                            SDL.SDLK_s => keyinput.shoulder_r.unset(),
+                            SDL.SDLK_RETURN => keyinput.start.unset(),
+                            SDL.SDLK_RSHIFT => keyinput.select.unset(),
                             else => {},
                         }
+
+                        cpu.bus.io.keyinput.store(keyinput.raw, .Monotonic);
                     },
                     SDL.SDL_KEYUP => {
-                        const io = &cpu.bus.io;
                         const key_code = event.key.keysym.sym;
+                        var keyinput = cpu.bus.io.keyinput.load(.Monotonic);
 
                         switch (key_code) {
-                            SDL.SDLK_UP => io.keyinput.up.set(),
-                            SDL.SDLK_DOWN => io.keyinput.down.set(),
-                            SDL.SDLK_LEFT => io.keyinput.left.set(),
-                            SDL.SDLK_RIGHT => io.keyinput.right.set(),
-                            SDL.SDLK_x => io.keyinput.a.set(),
-                            SDL.SDLK_z => io.keyinput.b.set(),
-                            SDL.SDLK_a => io.keyinput.shoulder_l.set(),
-                            SDL.SDLK_s => io.keyinput.shoulder_r.set(),
-                            SDL.SDLK_RETURN => io.keyinput.start.set(),
-                            SDL.SDLK_RSHIFT => io.keyinput.select.set(),
+                            SDL.SDLK_UP => keyinput.up.set(),
+                            SDL.SDLK_DOWN => keyinput.down.set(),
+                            SDL.SDLK_LEFT => keyinput.left.set(),
+                            SDL.SDLK_RIGHT => keyinput.right.set(),
+                            SDL.SDLK_x => keyinput.a.set(),
+                            SDL.SDLK_z => keyinput.b.set(),
+                            SDL.SDLK_a => keyinput.shoulder_l.set(),
+                            SDL.SDLK_s => keyinput.shoulder_r.set(),
+                            SDL.SDLK_RETURN => keyinput.start.set(),
+                            SDL.SDLK_RSHIFT => keyinput.select.set(),
                             SDL.SDLK_i => {
                                 comptime std.debug.assert(sample_format == SDL.AUDIO_U16);
-                                log.err("Sample Count: {}", .{@intCast(u32, SDL.SDL_AudioStreamAvailable(cpu.bus.apu.stream)) / (2 * @sizeOf(u16))});
-                            },
-                            SDL.SDLK_j => log.err("Scheduler Capacity: {} | Scheduler Event Count: {}", .{ scheduler.queue.capacity(), scheduler.queue.count() }),
-                            SDL.SDLK_k => {
-                                // Dump IWRAM to file
-                                log.info("PC: 0x{X:0>8}", .{cpu.r[15]});
-                                log.info("LR: 0x{X:0>8}", .{cpu.r[14]});
-                                // const iwram_file = try std.fs.cwd().createFile("iwram.bin", .{});
-                                // defer iwram_file.close();
-
-                                // try iwram_file.writeAll(cpu.bus.iwram.buf);
+                                log.err("Sample Count: {}", .{cpu.bus.apu.sample_queue.len() / 2});
                             },
+                            // SDL.SDLK_j => log.err("Scheduler Capacity: {} | Scheduler Event Count: {}", .{ scheduler.queue.capacity(), scheduler.queue.count() }),
+                            SDL.SDLK_k => {},
                             else => {},
                         }
+
+                        cpu.bus.io.keyinput.store(keyinput.raw, .Monotonic);
                     },
                     else => {},
                 }
@@ -230,16 +238,15 @@ pub const Gui = struct {
             gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_INT, null);
             SDL.SDL_GL_SwapWindow(self.window);
 
-            const dyn_title = std.fmt.bufPrint(&title_buf, "ZBA | {s} [Emu: {}fps] ", .{ self.title, tracker.value() }) catch unreachable;
+            const dyn_title = std.fmt.bufPrintZ(&title_buf, "ZBA | {s} [Emu: {}fps] ", .{ self.title, tracker.value() }) catch unreachable;
             SDL.SDL_SetWindowTitle(self.window, dyn_title.ptr);
         }
 
-        quit.store(true, .SeqCst); // Terminate Emulator Thread
+        quit.store(true, .Monotonic); // Terminate Emulator Thread
     }
 
     pub fn deinit(self: *Self) void {
         self.audio.deinit();
-        // TODO: Buffer deletions
         gl.deleteProgram(self.program_id);
         SDL.SDL_GL_DeleteContext(self.ctx);
         SDL.SDL_DestroyWindow(self.window);
@@ -292,7 +299,37 @@ const Audio = struct {
         const T = *Apu;
         const apu = @ptrCast(T, @alignCast(@alignOf(T), userdata));
 
-        _ = SDL.SDL_AudioStreamGet(apu.stream, stream, len);
+        comptime std.debug.assert(sample_format == SDL.AUDIO_U16);
+        const sample_buf = @ptrCast([*]u16, @alignCast(@alignOf(u16), stream))[0 .. @intCast(u32, len) / @sizeOf(u16)];
+
+        var previous: u16 = 0x8000;
+        for (sample_buf) |*sample| {
+            if (apu.sample_queue.pop()) |value| previous = value;
+
+            sample.* = previous;
+        }
+    }
+};
+
+const shader = struct {
+    const Kind = enum { vertex, fragment };
+    const log = std.log.scoped(.Shader);
+
+    fn didCompile(id: gl.GLuint) bool {
+        var success: gl.GLint = undefined;
+        gl.getShaderiv(id, gl.COMPILE_STATUS, &success);
+
+        if (success == 0) err(id);
+
+        return success == 1;
+    }
+
+    fn err(id: gl.GLuint) void {
+        const buf_len = 512;
+        var error_msg: [buf_len]u8 = undefined;
+
+        gl.getShaderInfoLog(id, buf_len, 0, &error_msg);
+        log.err("{s}", .{std.mem.sliceTo(&error_msg, 0)});
     }
 };
 

src/util.zig

@@ -47,7 +47,7 @@ pub const FpsTracker = struct {
 
     pub fn value(self: *Self) u32 {
         if (self.timer.read() >= std.time.ns_per_s) {
-            self.fps = self.count.swap(0, .SeqCst);
+            self.fps = self.count.swap(0, .Monotonic);
             self.timer.reset();
         }
 
@@ -181,7 +181,7 @@ pub const Logger = struct {
     }
 };
 
-const FmtArgTuple = std.meta.Tuple(&.{ u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32 });
+const FmtArgTuple = struct { u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32, u32 };
 
 pub const audio = struct {
     const _io = @import("core/bus/io.zig");
@@ -275,3 +275,73 @@ fn HalfInt(comptime T: type) type {
 
     return std.meta.Int(type_info.Int.signedness, type_info.Int.bits >> 1);
 }
+
+const Mutex = std.Thread.Mutex;
+
+pub fn RingBuffer(comptime T: type) type {
+    return struct {
+        const Self = @This();
+        const Index = usize;
+        const max_capacity = (std.math.powi(Index, 2, @typeInfo(Index).Int.bits - 1) catch @compileError("uhhhhh")) - 1;
+
+        read: Index,
+        write: Index,
+
+        buf: []T,
+
+        mutex: Mutex,
+
+        const Error = error{buffer_full};
+
+        pub fn init(buf: []T) Self {
+            std.debug.assert(std.math.isPowerOfTwo(buf.len)); // capacity must be a power of two
+            std.debug.assert(buf.len <= max_capacity); // Capacity must be half the range of the index data types
+
+            return .{ .read = 0, .write = 0, .buf = buf, .mutex = .{} };
+        }
+
+        pub fn push(self: *Self, left: T, right: T) Error!void {
+            self.mutex.lock();
+            defer self.mutex.unlock();
+
+            try self._push(left);
+            self._push(right) catch |e| {
+                self.write -= 1; // undo the previous write;
+                return e;
+            };
+        }
+
+        pub fn pop(self: *Self) ?T {
+            self.mutex.lock();
+            defer self.mutex.unlock();
+
+            if (self.isEmpty()) return null;
+            defer self.read += 1;
+
+            return self.buf[self.mask(self.read)];
+        }
+
+        pub fn len(self: *const Self) Index {
+            return self.write - self.read;
+        }
+
+        fn _push(self: *Self, value: T) Error!void {
+            if (self.isFull()) return error.buffer_full;
+            defer self.write += 1;
+
+            self.buf[self.mask(self.write)] = value;
+        }
+
+        fn isFull(self: *const Self) bool {
+            return self.len() == self.buf.len;
+        }
+
+        fn isEmpty(self: *const Self) bool {
+            return self.read == self.write;
+        }
+
+        fn mask(self: *const Self, idx: Index) Index {
+            return idx & (self.buf.len - 1);
+        }
+    };
+}