On Sat, 16 Aug 2008, Linus Torvalds wrote:
>
> The rules are:
>
> - valid days of month/mday are always single or double digits.
>
> - valid years are either two or four digits
>
> No, we don't support the year 600 _anyway_, since our encoding is based
> on the UNIX epoch, and the day we worry about the year 10,000 is far
> away and we can raise the limit to five digits when we get closer.
>
> - Other numbers (eg "600 days ago") can have any number of digits, but
> they cannot start with a zero. Again, the only exception is for
> two-digit numbers, since that is fairly common for dates ("Dec 01" is
> not unheard of)
>
> So that means that any milli- or micro-second would be thrown out just
> because the number of digits shows that it cannot be an interesting date.
I should explain that nonsensical statement a bit.
A milli- or micro-second can obviously be a perfectly fine number
according to the rules above, as long as it doesn't start with a '0'. So
if we have
12:34:56.123
then that '123' gets parsed as a number, and we remember it. But because
it's bigger than 31, we'll never use it as such _unless_ there is
something after it to trigger that use.
So you can say "12:34:56.123.days.ago", and because of the "days", that
123 will actually be meaninful now.
But the problem with "12.34.56.001" was that we used to remember the "001"
as a number, and because we could see no other use for it we then assumed
that it meant the day of the month.
Of course, we *should* do that only if we have seen a month-name too, but
we don't currently track that, so.. Adding that as a further sanity test
would be good, but it would require us to have some extra "flags" field.
Maybe we should have a
#define SEEN_MONTH 1
#define SEEN_YEAR 2
#define SEEN_DAY 4
#define SEEN_TIME 8
...
struct extended_tm {
unsigned long seen;
unsigned long number;
struct tm tm;
}
and pass *that* around instead of passing "struct tm *" and "unsigned long
*num" around. That would be good. Then we could do
if (tm->number && tm->number < 32 &&
(tm->seen & SEEN_MONTH) && !(tm->seen & SEEN_DAY))
tm->tm.tm_mday = tm->number;
there instead, which would protect us from other numbers just being seen
as days instead.
Anybody? I'm not going to bother.
Linus
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