Add test for util.NextPowerOfTwo() (open-telemetry#130)

util/util.go

@@ -7,6 +7,7 @@
 package util
 
 import (
+	"math/bits"
 	"strconv"
 	"sync/atomic"
 	"unicode"
@@ -60,17 +61,13 @@ func IsValidString(s string) bool {
 	return true
 }
 
-// NextPowerOfTwo returns the next highest power of 2 for a given value v or v,
-// if v is a power of 2.
+// NextPowerOfTwo returns input value if it's a power of two,
+// otherwise it returns the next power of two.
 func NextPowerOfTwo(v uint32) uint32 {
-	v--
-	v |= v >> 1
-	v |= v >> 2
-	v |= v >> 4
-	v |= v >> 8
-	v |= v >> 16
-	v++
-	return v
+	if v == 0 {
+		return 1
+	}
+	return 1 << bits.Len32(v-1)
 }
 
 // AtomicUpdateMaxUint32 updates the value in store using atomic memory primitives. newValue will

util/util_test.go

@@ -0,0 +1,30 @@
+package util
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNextPowerOfTwo(t *testing.T) {
+	tests := []struct {
+		name  string
+		input uint32
+		want  uint32
+	}{
+		{name: "zero", input: 0, want: 1},
+		{name: "one", input: 1, want: 1},
+		{name: "two", input: 2, want: 2},
+		{name: "three", input: 3, want: 4},
+		{name: "four", input: 4, want: 4},
+		{name: "five", input: 5, want: 8},
+		{name: "six", input: 6, want: 8},
+		{name: "0x370", input: 0x370, want: 0x400},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			require.Equalf(t, tt.want, NextPowerOfTwo(tt.input),
+				"NextPowerOfTwo() = %v, want %v", tt.want, tt.want)
+		})
+	}
+}