x.sa.int64[i], x.sa.int64[j] = x.sa.int64[j], x.sa.int64[i]
	}
}

func (x *index) at(i int) []byte {
	return x.data[x.sa.get(i):]
}

func testConstruction(t *testing.T, tc *testCase, x *Index) {
	if !sort.IsSorted((*index)(x)) {
		t.Errorf("failed testConstruction %s", tc.name)
	}
}

func equal(x, y *Index) bool {
	if !bytes.Equal(x.data, y.data) {
		return false
	}
	if x.sa.len() != y.sa.len() {