Attempt to refactor per-opcode validation.message

Instead of validating rrsets and sections after parsing them, check the
class/type for each record before parsing it.  This is more generic,
because it moves all of the update logic out of the common code.  It's
also more flexible, as it allows the update logic to specify that
meta-records are empty.

1 files changed, 16 insertions, 9 deletions

diff --git a/dns/update.py b/dns/update.py
index 9615a73..e21a283 100644
--- a/dns/update.py
+++ b/dns/update.py
@@ -300,17 +300,24 @@ class UpdateMessage(dns.message.Message):
         # Updates are always one_rr_per_rrset
         return True
 
-    def _validate_rrset(self, section, rrset):
+    def _parse_rr_header(self, reader, section, rdclass, rdtype):
+        deleting = None
+        empty = False
         if section == UpdateSection.ZONE:
-            if rrset.rdtype != dns.rdatatype.SOA:
+            if dns.rdataclass.is_metaclass(rdclass) or \
+               rdtype != dns.rdatatype.SOA or \
+               getattr(reader, 'zone_rdclass', None):
                 raise dns.exception.FormError
-
-    def _finish_section(self, section):
-        if section == UpdateSection.ZONE and len(self.zone) != 1:
-            raise dns.exception.FormError
-        self.zone_rdclass = self.zone[0].rdclass
-        # We do NOT want to set origin here, as that would cause
-        # from_wire() relativization.
+            reader.zone_rdclass = rdclass
+        else:
+            if not getattr(reader, 'zone_rdclass', None):
+                raise dns.exception.FormError
+            if rdclass in (dns.rdataclass.ANY, dns.rdataclass.NONE):
+                deleting = rdclass
+                rdclass = reader.zone_rdclass
+                empty = (deleting == dns.rdataclass.ANY or
+                         section == UpdateSection.PREREQ)
+        return (rdclass, rdtype, deleting, empty)
 
 # backwards compatibility
 Update = UpdateMessage