add dns.name.Name.parent()

3 files changed, 42 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 226fa76..e68b8f6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2005-10-06  Bob Halley  <halley@dnspython.org>
+
+	* dns/name.py: Added the parent() method, which returns the
+	  parent of a name.
+
 2005-10-01  Bob Halley  <halley@dnspython.org>
 
 	* dns/resolver.py: Added zone_for_name() helper, which returns
diff --git a/dns/name.py b/dns/name.py
index 3bf5b6e..c5e4b9a 100644
--- a/dns/name.py
+++ b/dns/name.py
@@ -69,6 +69,11 @@ class AbsoluteConcatenation(dns.exception.DNSException):
     empty name to an absolute name."""
     pass
 
+class NoParent(dns.exception.DNSException):
+    """Raised if an attempt is made to get the parent of the root name
+    or the empty name."""
+    pass
+
 _escaped = {
     '"' : True,
     '(' : True,
@@ -490,6 +495,16 @@ class Name(object):
                 return self.derelativize(origin)
         else:
             return self
+
+    def parent(self):
+        """Return the parent of the name.
+        @rtype: dns.name.Name object
+        @raises NoParent: the name is either the root name or the empty name,
+        and thus has no parent.
+        """
+        if self == root or self == empty:
+            raise NoParent
+        return Name(self.labels[1:])
         
 root = Name([''])
 empty = Name([])
diff --git a/tests/name.py b/tests/name.py
index 24abfcd..cc7ced5 100644
--- a/tests/name.py
+++ b/tests/name.py
@@ -589,5 +589,27 @@ class NameTestCase(unittest.TestCase):
             (n, cused) = dns.name.from_wire(w, 0)
         self.failUnlessRaises(dns.name.BadLabelType, bad)
 
+    def testParent1(self):
+        n = dns.name.from_text('foo.bar.')
+        self.failUnless(n.parent() == dns.name.from_text('bar.'))
+        self.failUnless(n.parent().parent() == dns.name.root)
+
+    def testParent2(self):
+        n = dns.name.from_text('foo.bar', None)
+        self.failUnless(n.parent() == dns.name.from_text('bar', None))
+        self.failUnless(n.parent().parent() == dns.name.empty)
+
+    def testParent3(self):
+        def bad():
+            n = dns.name.root
+            n.parent()
+        self.failUnlessRaises(dns.name.NoParent, bad)
+
+    def testParent4(self):
+        def bad():
+            n = dns.name.empty
+            n.parent()
+        self.failUnlessRaises(dns.name.NoParent, bad)
+
 if __name__ == '__main__':
     unittest.main()