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List:       kde-core-devel
Subject:    Caching local time zone
From:       David Jarvie <lists () astrojar ! org ! uk>
Date:       2006-09-21 9:04:57
Message-ID: 6d3c5f22e9af11f11b8fe6bb331aade0 () webmail ! plus ! net
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Using KDateTime for date/times in the local time zone can potentially result in very \
frequent calls to KSystemTimeZones::local() which fetches  and returns the current \
local system time zone. Depending on the system, that function may open and read \
files, and compare their contents.  Even if the files are still cached (as would \
usually be the case on a UNIX system when the function calls are made in quick \
succession), the  overhead in file system function calls makes me feel uneasy when \
the function could be called many times a second if arrays of date/time values  are \
being converted to or from the local time zone.

Plainly, the system time zone is not going to change frequently, so I think that it \
would be better to cache it and only reread it periodically. I  propose to set a \
timer to refresh it once a minute. Any comments/objections?

Note that this caching applies to the time *zone* (e.g. "Europe/Paris"). It has no \
impact on the handling of daylight saving time shifts which will  still be handled \
without any time lag.

--
David Jarvie.
KAlarm author & maintainer.
http://www.astrojar.org.uk/linux/kalarm.html


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