audio: make Take propagate errors

audio/compositors.go

@@ -7,22 +7,36 @@ import (
 
 // Take returns a Streamer which streams s for at most d duration.
 //
-// TODO: should Take propagate an error?
+// The returned Streamer propagates s's errors throught Err.
 func Take(d time.Duration, s Streamer) Streamer {
-	currSample := 0
-	numSamples := int(math.Ceil(d.Seconds() * SampleRate))
-	return StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
-		if currSample >= numSamples {
+	return &take{
+		s:          s,
+		currSample: 0,
+		numSamples: int(math.Ceil(d.Seconds() * SampleRate)),
+	}
+}
+
+type take struct {
+	s          Streamer
+	currSample int
+	numSamples int
+}
+
+func (t *take) Stream(samples [][2]float64) (n int, ok bool) {
+	if t.currSample >= t.numSamples {
 		return 0, false
 	}
-		toStream := numSamples - currSample
+	toStream := t.numSamples - t.currSample
 	if len(samples) < toStream {
 		toStream = len(samples)
 	}
-		sn, sok := s.Stream(samples[:toStream])
-		currSample += sn
+	sn, sok := t.s.Stream(samples[:toStream])
+	t.currSample += sn
 	return sn, sok
-	})
+}
+
+func (t *take) Err() error {
+	return t.s.Err()
 }
 
 // Seq takes zero or more Streamers and returns a Streamer which streams them one by one without pauses.