Count total & average in the first sample period after SW creation

README.md

@@ -17,23 +17,24 @@ import (
 
 func main() {
     // Create a SlidingWindow that has a window of 15 minutes, with a
-    // granulity of 1 minute.
-    sw := average.MustNew(15 * time.Minute, time.Minute)
+    // granularity of 1 minute.
+    sw := average.MustNew(15*time.Second, time.Second)
     defer sw.Stop()
 
-    // Do some work.
     sw.Add(15)
     // Do some more work.
+    time.Sleep(time.Second)
     sw.Add(22)
     // Do even more work.
+    time.Sleep(2 * time.Second)
     sw.Add(22)
 
-    fmt.Printf("Average of last  1m: %f\n", sw.Average(time.Minute)
-    fmt.Printf("Average of last  5m: %f\n", sw.Average(5 * time.Minute)
-    fmt.Printf("Average of last 15m: %f\n\n", sw.Average(15 * time.Minute)
+    fmt.Printf("Average of last 1s: %f\n", sw.Average(time.Second))
+    fmt.Printf("Average of last 2s: %f\n", sw.Average(2*time.Second))
+    fmt.Printf("Average of last 15s: %f\n\n", sw.Average(15*time.Second))
 
-    total, numSamples := sw.Total(15 * time.Minute)
-    fmt.Printf("Counter has a total of %d over %d samples", total, numSamples)
+    total, numSamples := sw.Total(15 * time.Second)
+    fmt.Printf("Counter has a total of %d over %d samples\n", total, numSamples)
 }
 ```
 

slidingwindow.go

@@ -48,6 +48,7 @@ func New(window, granularity time.Duration) (*SlidingWindow, error) {
 		granularity: granularity,
 		samples:     make([]int64, int(window/granularity)),
 		stopC:       make(chan struct{}),
+		size:        1,
 	}
 
 	go sw.shifter()
@@ -132,7 +133,7 @@ func (sw *SlidingWindow) Total(window time.Duration) (int64, int) {
 	for i := 1; i <= sampleCount; i++ {
 		pos := sw.pos - i
 		if pos < 0 {
-			pos += len(sw.samples)
+			pos += sw.size
 		}
 
 		total += sw.samples[pos]

slidingwindow_test.go

@@ -131,3 +131,12 @@ func TestTotal(t *testing.T) {
 		t.Errorf("expected the total over the last 10 seconds to be 12, not %d", v)
 	}
 }
+
+func TestTotalFromNew(t *testing.T) {
+	sw, _ := New(time.Minute, 15*time.Second)
+
+	sw.Add(15)
+	if v, _ := sw.Total(time.Minute); v != 15 {
+		t.Errorf("expected total to be 15, but got %d", v)
+	}
+}