Current File : //usr/lib/python3/dist-packages/dns/ttl.py
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
# Copyright (C) 2003-2017 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 TTL conversion."""
from typing import Union
import dns.exception
# Technically TTLs are supposed to be between 0 and 2**31 - 1, with values
# greater than that interpreted as 0, but we do not impose this policy here
# as values > 2**31 - 1 occur in real world data.
#
# We leave it to applications to impose tighter bounds if desired.
MAX_TTL = 2**32 - 1
class BadTTL(dns.exception.SyntaxError):
"""DNS TTL value is not well-formed."""
def from_text(text: str) -> int:
"""Convert the text form of a TTL to an integer.
The BIND 8 units syntax for TTLs (e.g. '1w6d4h3m10s') is supported.
*text*, a ``str``, the textual TTL.
Raises ``dns.ttl.BadTTL`` if the TTL is not well-formed.
Returns an ``int``.
"""
if text.isdigit():
total = int(text)
elif len(text) == 0:
raise BadTTL
else:
total = 0
current = 0
need_digit = True
for c in text:
if c.isdigit():
current *= 10
current += int(c)
need_digit = False
else:
if need_digit:
raise BadTTL
c = c.lower()
if c == "w":
total += current * 604800
elif c == "d":
total += current * 86400
elif c == "h":
total += current * 3600
elif c == "m":
total += current * 60
elif c == "s":
total += current
else:
raise BadTTL("unknown unit '%s'" % c)
current = 0
need_digit = True
if not current == 0:
raise BadTTL("trailing integer")
if total < 0 or total > MAX_TTL:
raise BadTTL("TTL should be between 0 and 2**32 - 1 (inclusive)")
return total
def make(value: Union[int, str]) -> int:
if isinstance(value, int):
return value
elif isinstance(value, str):
return dns.ttl.from_text(value)
else:
raise ValueError("cannot convert value to TTL")
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