Replace the implementation of Mix with Mixer

compositors.go

@@ -98,44 +98,10 @@ func Seq(s ...Streamer) Streamer {
 //
 // Mix does not propagate errors from the Streamers.
 func Mix(s ...Streamer) Streamer {
-	return StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
-		var tmp [512][2]float64
-
-		for len(samples) > 0 {
-			toStream := len(tmp)
-			if toStream > len(samples) {
-				toStream = len(samples)
-			}
-
-			// clear the samples
-			for i := range samples[:toStream] {
-				samples[i] = [2]float64{}
-			}
-
-			snMax := 0 // max number of streamed samples in this iteration
-			for _, st := range s {
-				// mix the stream
-				sn, sok := st.Stream(tmp[:toStream])
-				if sn > snMax {
-					snMax = sn
-				}
-				ok = ok || sok
-
-				for i := range tmp[:sn] {
-					samples[i][0] += tmp[i][0]
-					samples[i][1] += tmp[i][1]
-				}
-			}
-
-			n += snMax
-			if snMax < len(tmp) {
-				break
-			}
-			samples = samples[snMax:]
-		}
-
-		return n, ok
-	})
+	return &Mixer{
+		streamers:     s,
+		stopWhenEmpty: true,
+	}
 }
 
 // Dup returns two Streamers which both stream the same data as the original s. The two Streamers

compositors_test.go

@@ -91,9 +91,7 @@ func TestMix(t *testing.T) {
 
 	got := testtools.Collect(beep.Mix(s...))
 
-	if !reflect.DeepEqual(want, got) {
-		t.Error("Mix not working correctly")
-	}
+	testtools.AssertSamplesEqual(t, want, got)
 }
 
 func TestDup(t *testing.T) {

internal/testtools/asserts.go

@@ -57,3 +57,25 @@ func AssertStreamerHasCorrectReturnBehaviour(t *testing.T, s beep.Streamer, expe
 	assert.Equal(t, 0, n)
 	assert.NoError(t, s.Err())
 }
+
+func AssertSamplesEqual(t *testing.T, expected, actual [][2]float64) {
+	t.Helper()
+
+	if len(expected) != len(actual) {
+		t.Errorf("expected sample data length to be %d, got %d", len(expected), len(actual))
+		return
+	}
+
+	const epsilon = 1e-9
+	equals := true
+	for i := range expected {
+		if actual[i][0] < expected[i][0]-epsilon || actual[i][0] > expected[i][0]+epsilon ||
+			actual[i][1] < expected[i][1]-epsilon || actual[i][1] > expected[i][1]+epsilon {
+			equals = false
+			break
+		}
+	}
+	if !equals {
+		t.Errorf("the sample data isn't equal to the expected data")
+	}
+}