Hello Chen,
as we've seen already, the timezone detection is a very heuristic problem.
It makes it extremely complicated and unreliable,
if a system is not providing correct, incomplete
or even wrong information. If you only get the
names, you need an internal table to get the
start and end time of DST anyway.
Unfortunately not all Linux/Unix systems provide
much more than tzset(), so this is also not a
general solution using a daylight variable.
We could think about a compile switch for linux
systems which can provide more information. Our
MacOSX/iPhoneOS implementations are basing also
on other functions than tzset() for time zone
detection.
Regards,
Beat
Hello,
On linux (platform_adapters/linux/platform_timezones.cpp),
the implementation of getSystemTimeZoneContext seems have
problems: it use tzset() and later check tzname[0], tzname[1]
to match against a built-in known timezone table (sysync/tz_table.h).
I found the tzname fields set by tzset() is incorrect or at least ambiguous
on ubuntu karmic, fedora 11.
In my case, my system timezone is Asia/Shanghai
(UTC+8), but synthesis engine will
detect is as UTC-6.
My conclusion is we cannot use tzname fields to
detect the timezone, maybe we can
try use timezone and daylight variable instead?
------------------------------
See below tests:
The samle code is as below:
tzset()
printf ("tzname[0] %s\n", tzname[0]);
printf ("tzname[1] %s\n", tzname[1]);
---
Here are the output on Ubuntu karmic:
TZ=':Asia/Shanghai' ./test
tzname 0 CST
tzname 1 CDT
TZ=':America/Chicago' ./test
tzname 0 CST
tzname 1 CDT
TZ=':Asia/Tokyo' ./test
tzname 0 JST
tzname 1 JDT
Best Regards,
Congwu
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--
-----------------------------------------------
Beat FORSTER
Dipl. El. Ing. ETH
Dipl. NDS ETHZ in Betriebswissenschaften
Managing Partner
[email protected]
Synthesis AG SyncML Server & Client Solutions
Badenerstrasse 18, CH-8004 Zürich, Switzerland
Tel (direct): +41 44 440 66 02
Fax: +41 44 440 66 04
email: [email protected]
web: http://www.synthesis.ch
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