[Bugfix]: Out of range percentile calculations

It was possible for a user of percentile-calculation functions to
request a percentile that caused the underlying array of values to be
accessed out of bounds. This patch fixes that error.

Signed-off-by: Will Hawkins <[email protected]>

3 files changed, 44 insertions, 5 deletions

diff --git a/series/series.go b/series/series.go
index 43d9809..6b9af1f 100644
--- a/series/series.go
+++ b/series/series.go
@@ -127,6 +127,9 @@ func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) previousIndex(currentIndex
 func (wsi *windowSeriesWindowOnlyImpl[Data, Bucket]) toArray() []utilities.Optional[Data] {
 	result := make([]utilities.Optional[Data], wsi.windowSize)
 
+	if wsi.empty {
+		return result
+	}
 	iterator := wsi.latestIndex
 	parallelIterator := 0
 	for {
diff --git a/series/series_test.go b/series/series_test.go
index 5d2ab57..3ed752d 100644
--- a/series/series_test.go
+++ b/series/series_test.go
@@ -95,6 +95,25 @@ func Test_ForeverValues(test *testing.T) {
 	}
 }
 
+func Test_WindowOnly_no_values_getvalues(test *testing.T) {
+	expectedLen := 5
+	series := newWindowSeriesWindowOnlyImpl[float64, int](5)
+	result := series.GetValues()
+	allZeros := true
+	for _, v := range result {
+		if utilities.IsSome(v) {
+			allZeros = false
+			break
+		}
+	}
+	if len(result) != expectedLen {
+		test.Fatalf("GetValues of empty window-only series returned list with incorrect size.")
+	}
+	if !allZeros {
+		test.Fatalf("GetValues of empty window-only series returned list with some values.")
+	}
+}
+
 func Test_WindowOnlySequentialIncreasesAlwaysLessThan(test *testing.T) {
 	series := newWindowSeriesWindowOnlyImpl[float64, int](10)
 	previous := float64(1.0)
@@ -154,11 +173,18 @@ func Test_Forever_degenerate_percentile_too_high(test *testing.T) {
 
 func Test_Forever_degenerate_percentile_too_low(test *testing.T) {
 	series := newWindowSeriesForeverImpl[int, int]()
-	if complete, result := Percentile[int, int](series, -1); !complete || result != 0.0 {
+	if complete, result := Percentile[int, int](series, 0); !complete || result != 0.0 {
 		test.Fatalf("(infinite) Series percentile of -1 failed.")
 	}
 }
 
+func Test_Forever_degenerate_percentile_no_values(test *testing.T) {
+	series := newWindowSeriesForeverImpl[int, int]()
+	if complete, p := Percentile[int, int](series, 50); !complete || p != 0 {
+		test.Fatalf("empty series percentile of 50 failed.")
+	}
+}
+
 ///////////
 
 func Test_Forever90_percentile(test *testing.T) {
@@ -557,11 +583,18 @@ func Test_WindowOnly_degenerate_percentile_too_high(test *testing.T) {
 
 func Test_WindowOnly_degenerate_percentile_too_low(test *testing.T) {
 	series := newWindowSeriesWindowOnlyImpl[int, int](21)
-	if complete, p := Percentile[int, int](series, -1); complete != false || p != 0 {
+	if complete, p := Percentile[int, int](series, 0); complete != false || p != 0 {
 		test.Fatalf("Series percentile of -1 failed.")
 	}
 }
 
+func Test_WindowOnly_degenerate_percentile_no_values(test *testing.T) {
+	series := newWindowSeriesWindowOnlyImpl[int, int](0)
+	if complete, p := Percentile[int, int](series, 50); !complete || p != 0 {
+		test.Fatalf("empty series percentile of 50 failed.")
+	}
+}
+
 func Test_WindowOnly90_percentile(test *testing.T) {
 	var expected int = 10
 	series := newWindowSeriesWindowOnlyImpl[int, int](10)
diff --git a/utilities/math.go b/utilities/math.go
index 1ecca61..96b9f10 100644
--- a/utilities/math.go
+++ b/utilities/math.go
@@ -36,15 +36,18 @@ func CalculateAverage[T Number](elements []T) float64 {
 
 func CalculatePercentile[T Number](
 	elements []T,
-	p int,
+	p uint,
 ) (result T) {
 	result = T(0)
-	if p < 0 || p > 100 {
+	if p < 1 || p > 100 {
 		return
 	}
 
 	sort.Slice(elements, func(l int, r int) bool { return elements[l] < elements[r] })
-	pindex := int64((float64(p) / float64(100)) * float64(len(elements)))
+	pindex := int((float64(p) / float64(100)) * float64(len(elements)))
+	if pindex >= len(elements) {
+		return
+	}
 	result = elements[pindex]
 	return
 }