audio: add soundio-sine-wave example

audio/build.zig

@@ -8,10 +8,16 @@ pub const pkg = std.build.Pkg{
     .source = .{ .path = thisDir() ++ "/main.zig" },
 };
 
+const soundio_pkg = std.build.Pkg{
+    .name = "soundio",
+    .source = .{ .path = thisDir() ++ "/soundio/main.zig" },
+};
+
 pub const Options = struct {};
 
 pub fn build(b: *Builder) void {
     const mode = b.standardReleaseOptions();
+    const target = b.standardTargetOptions(.{});
 
     const soundio_tests = b.addTest("soundio/main.zig");
     soundio_tests.setBuildMode(mode);
@@ -20,6 +26,29 @@ pub fn build(b: *Builder) void {
 
     const test_step = b.step("test", "Run library tests");
     test_step.dependOn(&soundio_tests.step);
+
+    inline for ([_][]const u8{
+        "soundio-sine-wave",
+    }) |example| {
+        const example_exe = b.addExecutable("example-" ++ example, "examples/" ++ example ++ ".zig");
+        example_exe.setBuildMode(mode);
+        example_exe.setTarget(target);
+        example_exe.addPackage(soundio_pkg);
+        link(b, example_exe, .{});
+        example_exe.install();
+
+        const example_compile_step = b.step("example-" ++ example, "Compile '" ++ example ++ "' example");
+        example_compile_step.dependOn(b.getInstallStep());
+
+        const example_run_cmd = example_exe.run();
+        example_run_cmd.step.dependOn(b.getInstallStep());
+        if (b.args) |args| {
+            example_run_cmd.addArgs(args);
+        }
+
+        const example_run_step = b.step("run-example-" ++ example, "Run '" ++ example ++ "' example");
+        example_run_step.dependOn(&example_run_cmd.step);
+    }
 }
 
 pub fn link(b: *Builder, step: *std.build.LibExeObjStep, options: Options) void {

audio/examples/soundio-sine-wave.zig

@@ -0,0 +1,77 @@
+const std = @import("std");
+const soundio = @import("soundio");
+const c = soundio.c;
+const SoundIo = soundio.SoundIo;
+const OutStream = soundio.OutStream;
+
+var seconds_offset: f32 = 0;
+
+fn write_callback(
+    maybe_outstream: ?[*]c.SoundIoOutStream,
+    frame_count_min: c_int,
+    frame_count_max: c_int,
+) callconv(.C) void {
+    _ = frame_count_min;
+    const outstream = OutStream{ .handle = @ptrCast(*c.SoundIoOutStream, maybe_outstream) };
+    const layout = outstream.layout();
+    const float_sample_rate = outstream.sampleRate();
+    const seconds_per_frame = 1.0 / @intToFloat(f32, float_sample_rate);
+    var frames_left = frame_count_max;
+
+    while (frames_left > 0) {
+        var frame_count = frames_left;
+
+        var areas: [*]c.SoundIoChannelArea = undefined;
+        outstream.beginWrite(
+            @ptrCast([*]?[*]c.SoundIoChannelArea, &areas),
+            &frame_count,
+        ) catch |err| std.debug.panic("write failed: {s}", .{@errorName(err)});
+
+        if (frame_count == 0) break;
+
+        const pitch = 440.0;
+        const radians_per_second = pitch * 2.0 * std.math.pi;
+        var frame: c_int = 0;
+        while (frame < frame_count) : (frame += 1) {
+            const sample = std.math.sin((seconds_offset + @intToFloat(f32, frame) *
+                seconds_per_frame) * radians_per_second);
+            {
+                var channel: usize = 0;
+                while (channel < @intCast(usize, layout.channelCount())) : (channel += 1) {
+                    const channel_ptr = areas[channel].ptr;
+                    const sample_ptr = &channel_ptr[@intCast(usize, areas[channel].step * frame)];
+                    @ptrCast(*f32, @alignCast(@alignOf(f32), sample_ptr)).* = sample;
+                }
+            }
+        }
+        seconds_offset += seconds_per_frame * @intToFloat(f32, frame_count);
+        outstream.endWrite() catch |err| std.debug.panic("end write failed: {s}", .{@errorName(err)});
+        frames_left -= frame_count;
+    }
+}
+
+pub fn main() !void {
+    const sio = try SoundIo.init();
+    defer sio.deinit();
+    try sio.connect();
+    sio.flushEvents();
+
+    const default_output_index = sio.defaultOutputDeviceIndex().?;
+    if (default_output_index < 0) return error.NoOutputDeviceFound;
+
+    const device = sio.getOutputDevice(default_output_index) orelse return error.OutOfMemory;
+    defer device.unref();
+
+    std.debug.print("Output device: {s}\n", .{device.name()});
+
+    const outstream = try device.createOutStream();
+    defer outstream.deinit();
+
+    outstream.setFormat(.float32LE);
+    outstream.setWriteCallback(write_callback);
+
+    try outstream.open();
+    try outstream.start();
+
+    while (true) sio.waitEvents();
+}