Add callback and playback timestamp implementation for webaudio stream

src/host/emscripten/mod.rs

@@ -248,11 +248,7 @@ where
             let now_secs: f64 = js!(@{audio_ctxt}.getOutputTimestamp().currentTime)
                 .try_into()
                 .expect("failed to retrieve Value as f64");
-            let callback = {
-                let secs = now_secs as i64;
-                let nanos = ((now_secs * 1_000_000_000.0) - secs as f64 * 1_000_000_000.0) as u32;
-                crate::StreamInstant::new(secs, nanos)
-            };
+            let callback = crate::StreamInstant::from_secs_f64(now_secs);
             // TODO: Use proper latency instead. Currently unsupported on most browsers though so
             // we estimate based on buffer size instead. Probably should use this, but it's only
             // supported by firefox (2020-04-28).

src/host/webaudio/mod.rs

@@ -242,6 +242,7 @@ impl DeviceTrait for Device {
                 .write()
                 .unwrap()
                 .replace(Closure::wrap(Box::new(move || {
+                    let now = ctx_handle.current_time();
                     let time_at_start_of_buffer = {
                         let time_at_start_of_buffer = time_handle
                             .read()
@@ -251,7 +252,7 @@ impl DeviceTrait for Device {
                             *time_at_start_of_buffer
                         } else {
                             // 25ms of time to fetch the first sample data, increase to avoid initial underruns.
-                            ctx_handle.current_time() + 0.025
+                            now + 0.025
                         }
                     };
 
@@ -262,8 +263,8 @@ impl DeviceTrait for Device {
                         let sample_format = SampleFormat::F32;
                         let mut data = unsafe { Data::from_parts(data, len, sample_format) };
                         let mut data_callback = data_callback_handle.lock().unwrap();
-                        let callback = unimplemented!();
-                        let playback = unimplemented!();
+                        let callback = crate::StreamInstant::from_secs_f64(now);
+                        let playback = crate::StreamInstant::from_secs_f64(time_at_start_of_buffer);
                         let timestamp = crate::OutputStreamTimestamp { callback, playback };
                         let info = OutputCallbackInfo { timestamp };
                         (data_callback.deref_mut())(&mut data, &info);

src/lib.rs

@@ -341,12 +341,14 @@ impl StreamInstant {
         (self.secs as i128 * 1_000_000_000) + self.nanos as i128
     }
 
+    #[allow(dead_code)]
     fn from_nanos(nanos: i64) -> Self {
         let secs = nanos / 1_000_000_000;
         let subsec_nanos = nanos - secs * 1_000_000_000;
         Self::new(secs as i64, subsec_nanos as u32)
     }
 
+    #[allow(dead_code)]
     fn from_nanos_i128(nanos: i128) -> Option<Self> {
         let secs = nanos / 1_000_000_000;
         if secs > std::i64::MAX as i128 || secs < std::i64::MIN as i128 {
@@ -358,6 +360,13 @@ impl StreamInstant {
         }
     }
 
+    #[allow(dead_code)]
+    fn from_secs_f64(secs: f64) -> crate::StreamInstant {
+        let s = secs.floor() as i64;
+        let ns = ((secs - s as f64) * 1_000_000_000.0) as u32;
+        Self::new(s, ns)
+    }
+
     fn new(secs: i64, nanos: u32) -> Self {
         StreamInstant { secs, nanos }
     }