util: fix a bug with not copying slice of len=1 in ArrayReverse

ArrayReverse copies it's argument only if it's len is > 1.
It needs to be consistent in all cases.

pkg/util/array.go

@@ -2,10 +2,6 @@ package util
 
 // ArrayReverse returns a reversed version of the given byte slice.
 func ArrayReverse(b []byte) []byte {
-	// Protect from big.Ints that have 1 len bytes.
-	if len(b) < 2 {
-		return b
-	}
 	dest := make([]byte, len(b))
 	for i, j := 0, len(b)-1; i <= j; i, j = i+1, j-1 {
 		dest[i], dest[j] = b[j], b[i]

pkg/util/array_test.go

@@ -30,7 +30,16 @@ var testCases = []struct {
 
 func TestArrayReverse(t *testing.T) {
 	for _, tc := range testCases {
-		have := ArrayReverse(tc.arr)
+		arg := make([]byte, len(tc.arr))
+		copy(arg, tc.arr)
+
+		have := ArrayReverse(arg)
 		require.Equal(t, tc.rev, have)
+
+		// test that argument was copied
+		for i := range have {
+			have[i] = ^have[i]
+		}
+		require.Equal(t, tc.arr, arg)
 	}
 }