If a DateTime gets modified to cross the DST state from its previous
state then we want to update the DateTime to compensate for the new
offset.
In other words, if we have a DateTime defined as:
DateTime({ y: 2009, m: 8, d: 15, hh: 3, mm: 0, tz: 'Europe/London' });
and we add six months to it, the hour must be changed to 60 minutes
behind, as the DST comes into effect.
https://bugzilla.gnome.org/show_bug.cgi?id=50076
Otherwise we'll have to do:
dt = g_date_time_new_full (Y, M, D, h, m, s, tz);
tmp = g_date_time_add_usec (dt, usec);
g_date_time_unref (dt);
dt = tmp;
With its additional allocations.
https://bugzilla.gnome.org/show_bug.cgi?id=50076
Timezone handling is complicated. Really complicated.
In order to simplify it a little bit, we need to expose the GTimeZone
structure.
First of all, we allow creating time zone information directly from the
offset and the DST state, and then pass it to the g_date_time_new_full()
constructor. We also need to clean up the mess that is UTC-vs.-localtime
for the other constructors.
We also allow creating a GTimeZone from the Olson zoneinfo database
names; a time zone created like this will be "floating": it will just
reference the zoneinfo file - which are mmap()'ed, kept in a cache and
refcounted. Once the GTimeZone has been associated with a GDateTime, it
will be "anchored" to it: the offset will be resolved, as well as the
DST state.
https://bugzilla.gnome.org/show_bug.cgi?id=50076
The current implementation of g_date_time_add_full() creates multiple
GDateTime temporary objects and unrefs them immediately; even with the
slice allocator this could result in a performance bottleneck,
especially if the atomic integer operations fall back to slow paths.
We can isolate the components of the add_full() operation and create
internal modifiers that operate on an existing GDateTime; this brings
down the number of GDateTime copies created from six to one.
While at it, the test suite for add_full() should have more checks for
roll-over of months and days.
Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>
