Add basic from_parser() support to rdata including scaffolding for not-yet-refactored classes.

2 files changed, 48 insertions, 6 deletions

diff --git a/dns/rdata.py b/dns/rdata.py
index 2de1763..b681d34 100644
--- a/dns/rdata.py
+++ b/dns/rdata.py
@@ -474,6 +474,46 @@ def from_text(rdclass, rdtype, tok, origin=None, relativize=True,
                          relativize_to)
 
 
+def from_parser(rdclass, rdtype, parser, rdlen, origin=None):
+    """Build an rdata object from wire format
+
+    This function attempts to dynamically load a class which
+    implements the specified rdata class and type.  If there is no
+    class-and-type-specific implementation, the GenericRdata class
+    is used.
+
+    Once a class is chosen, its from_wire() class method is called
+    with the parameters to this function.
+
+    *rdclass*, an ``int``, the rdataclass.
+
+    *rdtype*, an ``int``, the rdatatype.
+
+    *parser*, a ``dns.binary.Parser``, the parser.
+
+    *rdlen*, an ``int``, the length of the wire-format rdata
+
+    *origin*, a ``dns.name.Name`` (or ``None``).  If not ``None``,
+    then names will be relativized to this origin.
+
+    Returns an instance of the chosen Rdata subclass.
+    """
+
+    rdclass = dns.rdataclass.RdataClass.make(rdclass)
+    rdtype = dns.rdatatype.RdataType.make(rdtype)
+    cls = get_rdata_class(rdclass, rdtype)
+    try:
+        with parser.restrict_to(rdlen):
+            return cls.from_parser(rdclass, rdtype, parser, origin)
+    except AttributeError:
+        # XXXRTH This is a temporary porting hack
+        wire = dns.wiredata.maybe_wrap(parser.wire)
+        rdata = cls.from_wire(rdclass, rdtype, wire, parser.current,
+                              rdlen, origin)
+        parser.get_bytes(rdlen)
+        return rdata
+
+
 def from_wire(rdclass, rdtype, wire, current, rdlen, origin=None):
     """Build an rdata object from wire format
 
@@ -501,12 +541,8 @@ def from_wire(rdclass, rdtype, wire, current, rdlen, origin=None):
 
     Returns an instance of the chosen Rdata subclass.
     """
-
-    wire = dns.wiredata.maybe_wrap(wire)
-    rdclass = dns.rdataclass.RdataClass.make(rdclass)
-    rdtype = dns.rdatatype.RdataType.make(rdtype)
-    cls = get_rdata_class(rdclass, rdtype)
-    return cls.from_wire(rdclass, rdtype, wire, current, rdlen, origin)
+    parser = dns._binary.Parser(wire, current)
+    return from_parser(rdclass, rdtype, parser, rdlen, origin)
 
 
 class RdatatypeExists(dns.exception.DNSException):
diff --git a/tests/test_rdata.py b/tests/test_rdata.py
index 0ed38b7..9b1fdf8 100644
--- a/tests/test_rdata.py
+++ b/tests/test_rdata.py
@@ -409,5 +409,11 @@ class RdataTestCase(unittest.TestCase):
                                 binascii.unhexlify('f00100030000'), 0, 6)
         self.assertRaises(dns.exception.FormError, bad2)
 
+    def test_from_parser(self):
+        wire = bytes.fromhex('01020304')
+        rdata = dns.rdata.from_wire('in', 'a', wire, 0, 4)
+        print(rdata)
+        self.assertEqual(rdata, dns.rdata.from_text('in', 'a', '1.2.3.4'))
+
 if __name__ == '__main__':
     unittest.main()