Add a couple more rust + sdl2-audio samples

src/bin/play-wav.rs

@@ -0,0 +1,31 @@
+use std::env;
+
+use sdl2::audio::{AudioSpecDesired, AudioSpecWAV};
+use std::time::Duration;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() < 2 {
+        println!("Usage:");
+        println!("  {} foo.wav...", args[0]);
+        return;
+    }
+    let sdl = sdl2::init().unwrap();
+    let sounds: Vec<_> = args[1..].iter().map(|f|
+        AudioSpecWAV::load_wav(f).unwrap()
+    ).collect();
+    for sound in sounds {
+        let audio_len = sound.buffer().len(); // bytes 
+        dbg!(&audio_len);
+        let desired = AudioSpecDesired{
+            freq: Some(sound.freq),
+            channels: Some(sound.channels),
+            samples: Some(sound.format as u16)
+        };
+        let audio = sdl.audio().unwrap();
+        let sound_queue = audio.open_queue(None, &desired).unwrap();
+        sound_queue.queue_audio(sound.buffer()).unwrap();
+        sound_queue.resume();
+        std::thread::sleep(Duration::from_millis(audio_len as u64 * 1000 / sound.freq as u64 / sound.channels as u64));
+    }
+}

src/bin/square-wave.rs

@@ -0,0 +1,52 @@
+use sdl2::audio::{AudioCallback, AudioSpecDesired};
+use std::time::Duration;
+
+struct SquareWave {
+    phase_inc: f32,
+    phase: f32,
+    volume: f32,
+}
+
+impl AudioCallback for SquareWave {
+    type Channel = f32;
+
+    fn callback(&mut self, out: &mut [f32]) {
+        // Generate a square wave
+        for x in out.iter_mut() {
+            *x = if self.phase <= 0.5 {
+                self.volume
+            } else {
+                -self.volume
+            };
+            self.phase = (self.phase + self.phase_inc) % 1.0;
+        }
+    }
+}
+
+fn main() {
+    let sdl_context = sdl2::init().unwrap();
+    let audio_subsystem = sdl_context.audio().unwrap();
+
+    let desired_spec = AudioSpecDesired {
+        freq: Some(44100),
+        channels: Some(1), // mono
+        samples: None,     // default sample size
+    };
+
+    let device = audio_subsystem
+        .open_playback(None, &desired_spec, |spec| {
+            // initialize the audio callback
+            SquareWave {
+                phase_inc: 440.0 / spec.freq as f32,
+                phase: 0.0,
+                volume: 0.25,
+            }
+        })
+        .unwrap();
+
+    // Start playback
+    device.resume();
+
+    // Play for 2 seconds
+    std::thread::sleep(Duration::from_millis(2000));
+}