# Copyright (C) 2003-2007, 2009, 2010 Nominum, Inc.
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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"""MX-like base classes."""
from __future__ import absolute_import
import cStringIO
import struct
from .. import exception as dns_exception
from .. import rdata as dns_rdata
from .. import name as dns_name
[docs]class MXBase(dns_rdata.Rdata):
"""Base class for rdata that is like an MX record.
@ivar preference: the preference value
@type preference: int
@ivar exchange: the exchange name
@type exchange: dns_name.Name object"""
__slots__ = ['preference', 'exchange']
def __init__(self, rdclass, rdtype, preference, exchange):
super(MXBase, self).__init__(rdclass, rdtype)
self.preference = preference
self.exchange = exchange
[docs] def to_text(self, origin=None, relativize=True, **kw):
exchange = self.exchange.choose_relativity(origin, relativize)
return '%d %s' % (self.preference, exchange)
[docs] def from_text(cls, rdclass, rdtype, tok, origin = None, relativize = True):
preference = tok.get_uint16()
exchange = tok.get_name()
exchange = exchange.choose_relativity(origin, relativize)
tok.get_eol()
return cls(rdclass, rdtype, preference, exchange)
from_text = classmethod(from_text)
[docs] def to_wire(self, file, compress = None, origin = None):
pref = struct.pack("!H", self.preference)
file.write(pref)
self.exchange.to_wire(file, compress, origin)
[docs] def to_digestable(self, origin = None):
return struct.pack("!H", self.preference) + \
self.exchange.to_digestable(origin)
[docs] def from_wire(cls, rdclass, rdtype, wire, current, rdlen, origin = None):
(preference, ) = struct.unpack('!H', wire[current : current + 2])
current += 2
rdlen -= 2
(exchange, cused) = dns_name.from_wire(wire[: current + rdlen],
current)
if cused != rdlen:
raise dns_exception.FormError
if not origin is None:
exchange = exchange.relativize(origin)
return cls(rdclass, rdtype, preference, exchange)
from_wire = classmethod(from_wire)
[docs] def choose_relativity(self, origin = None, relativize = True):
self.exchange = self.exchange.choose_relativity(origin, relativize)
def _cmp(self, other):
sp = struct.pack("!H", self.preference)
op = struct.pack("!H", other.preference)
v = cmp(sp, op)
if v == 0:
v = cmp(self.exchange, other.exchange)
return v
[docs]class UncompressedMX(MXBase):
"""Base class for rdata that is like an MX record, but whose name
is not compressed when converted to DNS wire format, and whose
digestable form is not downcased."""
[docs] def to_wire(self, file, compress = None, origin = None):
super(UncompressedMX, self).to_wire(file, None, origin)
[docs] def to_digestable(self, origin = None):
f = cStringIO.StringIO()
self.to_wire(f, None, origin)
return f.getvalue()
[docs]class UncompressedDowncasingMX(MXBase):
"""Base class for rdata that is like an MX record, but whose name
is not compressed when convert to DNS wire format."""
[docs] def to_wire(self, file, compress = None, origin = None):
super(UncompressedDowncasingMX, self).to_wire(file, None, origin)