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# Copyright (C) 2001-2017 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
"""DNS Rdata Classes."""
import re
import dns.exception
RESERVED0 = 0
IN = 1
CH = 3
HS = 4
NONE = 254
ANY = 255
_by_text = {
'RESERVED0': RESERVED0,
'IN': IN,
'CH': CH,
'HS': HS,
'NONE': NONE,
'ANY': ANY
}
# We construct the inverse mapping programmatically to ensure that we
# cannot make any mistakes (e.g. omissions, cut-and-paste errors) that
# would cause the mapping not to be true inverse.
_by_value = {y: x for x, y in _by_text.items()}
# Now that we've built the inverse map, we can add class aliases to
# the _by_text mapping.
_by_text.update({
'INTERNET': IN,
'CHAOS': CH,
'HESIOD': HS
})
_metaclasses = {
NONE: True,
ANY: True
}
_unknown_class_pattern = re.compile('CLASS([0-9]+)$', re.I)
class UnknownRdataclass(dns.exception.DNSException):
"""A DNS class is unknown."""
def from_text(text):
"""Convert text into a DNS rdata class value.
The input text can be a defined DNS RR class mnemonic or
instance of the DNS generic class syntax.
For example, "IN" and "CLASS1" will both result in a value of 1.
Raises ``dns.rdatatype.UnknownRdataclass`` if the class is unknown.
Raises ``ValueError`` if the rdata class value is not >= 0 and <= 65535.
Returns an ``int``.
"""
value = _by_text.get(text.upper())
if value is None:
match = _unknown_class_pattern.match(text)
if match is None:
raise UnknownRdataclass
value = int(match.group(1))
if value < 0 or value > 65535:
raise ValueError("class must be between >= 0 and <= 65535")
return value
def to_text(value):
"""Convert a DNS rdata type value to text.
If the value has a known mnemonic, it will be used, otherwise the
DNS generic class syntax will be used.
Raises ``ValueError`` if the rdata class value is not >= 0 and <= 65535.
Returns a ``str``.
"""
if value < 0 or value > 65535:
raise ValueError("class must be between >= 0 and <= 65535")
text = _by_value.get(value)
if text is None:
text = 'CLASS' + repr(value)
return text
def is_metaclass(rdclass):
"""True if the specified class is a metaclass.
The currently defined metaclasses are ANY and NONE.
*rdclass* is an ``int``.
"""
if rdclass in _metaclasses:
return True
return False
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