[1514] appended some comments for DDNS_SOA and simplify __write_soa_internal

function

src/lib/python/isc/ddns/session.py

@@ -112,39 +112,50 @@ def convert_rrset_class(rrset, rrclass):
         new_rrset.add_rdata(isc.dns.Rdata(rrset.get_type(), rrclass, wire))
     return new_rrset
 
-class DDNSSOA:
+class DDNS_SOA:
     '''Class to handle the SOA in the DNS update '''
 
     def __get_serial_internal(self, origin_soa):
-        '''get serial number from soa'''
+        '''Get serial number from soa'''
         return Serial(int(origin_soa.get_rdata()[0].to_text().split()[2]))
 
     def __write_soa_internal(self, origin_soa, soa_num):
-        '''write serial number to soa'''
+        '''Write back serial number to soa'''
         new_soa = RRset(origin_soa.get_name(), origin_soa.get_class(),
                         RRType.SOA(), origin_soa.get_ttl())
-        new_content = ""
-        index = 0
-        for i in origin_soa.get_rdata()[0].to_text().split():
-            if(index == 2):
-                # the second item is serial number
-                new_content = "%s %d"%(new_content, soa_num.get_value())
-            else:
-                new_content = "%s %s"%(new_content, i)
-            index += 1
+        soa_rdata_parts = origin_soa.get_rdata()[0].to_text().split()
+        soa_rdata_parts[2] = str(soa_num.get_value())
         new_soa.add_rdata(Rdata(origin_soa.get_type(), origin_soa.get_class(),
-                                new_content))
+                                " ".join(soa_rdata_parts)))
         return new_soa
 
     def soa_update_check(self, origin_soa, new_soa):
+        '''Check whether the new soa is valid. If the serial number is bigger
+        than the old one, it is valid, then return True, otherwise, return
+        False.
+        Parameters:
+            origin_soa, old SOA resource record.
+            new_soa, new SOA resource record.
+        Output:
+            if the serial number of new soa is bigger than the old one, return
+            True, otherwise return False.
+        '''
         old_serial = self.__get_serial_internal(origin_soa)
         new_serial = self.__get_serial_internal(new_soa)
-        if(new_serial >= old_serial):
+        if(new_serial > old_serial):
             return True
         else:
             return False
 
     def update_soa(self, origin_soa, inc_number = 1):
+        ''' Update the soa number incrementally as RFC 2136.
+        Parameters:
+            origin_soa, the soa resource record which will be updated.
+            inc_number, the number which will be added into the serial number of
+            origin_soa, the default value is one.
+        Output:
+            the new origin soa whoes serial number has been updated.
+        '''
         soa_num = self.__get_serial_internal(origin_soa)
         soa_num = soa_num + inc_number
         if soa_num.get_value() == 0:
@@ -716,7 +727,7 @@ class UpdateSession:
         result, old_soa, _ = self.__finder.find(self.__zname, RRType.SOA(),
                                                 ZoneFinder.NO_WILDCARD |
                                                 ZoneFinder.FIND_GLUE_OK)
-        serial_operation = DDNSSOA()
+        serial_operation = DDNS_SOA()
         if self.__added_soa is not None:
             # serial check goes here
             if serial_operation.soa_update_check(old_soa, self.__added_soa):

src/lib/python/isc/ddns/tests/session_tests.py

@@ -90,10 +90,10 @@ def add_rdata(rrset, rdata):
                                   rdata))
 
 class TestDDNSSOA(unittest.TestCase):
-    '''unittest for the DDNSSOA'''
+    '''unittest for the DDNS_SOA'''
     def test_update_soa(self):
         '''unittest for update_soa function'''
-        soa_update = DDNSSOA()
+        soa_update = DDNS_SOA()
         soa_rr = create_rrset("example.org", TEST_RRCLASS,
                               RRType.SOA(), 3600, ["ns1.example.org. " +
                               "admin.example.org. " +
@@ -126,7 +126,7 @@ class TestDDNSSOA(unittest.TestCase):
                                     3600, ["ns1.example.org. " +
                                     "admin.example.org. " +
                                     "1234 3600 1800 2419200 7200"])
-        soa_update = DDNSSOA()
+        soa_update = DDNS_SOA()
         # The case of (i1 < i2 and i2 - i1 < 2^(SERIAL_BITS - 1)) in rfc 1982
         self.assertTrue(soa_update.soa_update_check(small_soa_rr,
                                                     large_soa_rr))