One more helper function for compression

label_test.go

@@ -28,3 +28,14 @@ func TestCompareLabels(t *testing.T) {
                 t.Fail()
         }
 }
+
+func TestOffLabelFromRight(t *testing.T) {
+        s1 := "www.miek.nl" // fqdn??
+
+        t.Log(offsetLabelFromRight(s1, 4))
+        t.Log(offsetLabelFromRight(s1, 3))
+        t.Log(offsetLabelFromRight(s1, 2))
+        t.Log(offsetLabelFromRight(s1, 1))
+        t.Log(offsetLabelFromRight(s1, 0))
+        t.Fail()
+}

labels.go

@@ -48,3 +48,19 @@ func CompareLabels(s1, s2 string) (n int) {
 	}
 	return
 }
+
+// This function is needed for easy handling of compression 
+// pointers
+// www.miek.nl, 2, gives that start of miek.nl (which is
+// 2 labels from the right)
+// labeloffset of zero is fishy as is a labeloffset larger
+// than the number of labels... TODO: make it an error?
+func offsetLabelFromRight(s string, labeloffset int) int {
+	l := SplitLabels(s)
+	fromleft := len(l) - labeloffset
+	off := 0
+	for i := 0; i < fromleft; i++ {
+		off += len(l[i]) + 1
+	}
+	return off
+}