1# Copyright (C) 2003-2007, 2009, 2010 Nominum, Inc.
2#
3# Permission to use, copy, modify, and distribute this software and its
4# documentation for any purpose with or without fee is hereby granted,
5# provided that the above copyright notice and this permission notice
6# appear in all copies.
7#
8# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
9# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
11# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
14# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15
16"""DNS TTL conversion."""
17
18import dns.exception
19
20class BadTTL(dns.exception.SyntaxError):
21    pass
22
23def from_text(text):
24    """Convert the text form of a TTL to an integer.
25
26    The BIND 8 units syntax for TTLs (e.g. '1w6d4h3m10s') is supported.
27
28    @param text: the textual TTL
29    @type text: string
30    @raises dns.ttl.BadTTL: the TTL is not well-formed
31    @rtype: int
32    """
33
34    if text.isdigit():
35        total = long(text)
36    else:
37        if not text[0].isdigit():
38            raise BadTTL
39        total = 0L
40        current = 0L
41        for c in text:
42            if c.isdigit():
43                current *= 10
44                current += long(c)
45            else:
46                c = c.lower()
47                if c == 'w':
48                    total += current * 604800L
49                elif c == 'd':
50                    total += current * 86400L
51                elif c == 'h':
52                    total += current * 3600L
53                elif c == 'm':
54                    total += current * 60L
55                elif c == 's':
56                    total += current
57                else:
58                    raise BadTTL("unknown unit '%s'" % c)
59                current = 0
60        if not current == 0:
61            raise BadTTL("trailing integer")
62    if total < 0L or total > 2147483647L:
63        raise BadTTL("TTL should be between 0 and 2^31 - 1 (inclusive)")
64    return total
65