Allthough most dive computers always use local time and don't support
timezones at all, there are a few exceptions. There are two different
sources of timezone information:
- Some of the newer Uwatec/Scubapro devices use UTC internally and also
support a timezone setting. This UTC offset is currently taken into
account to obtain the dive date/time, but the UTC offset itself is
lost.
- Uwatec/Scubapro and Reefnet devices rely on the clock of the host
system to synchronize the internal device clock and calculate the
dive date/time. The consequence is that the resulting date/time is
always in the timezone of the host system.
In order to preserve this timezone information, the dc_datetime_t
structure is extended with a new "timezone" field, containing the UTC
offset in seconds. Devices without timezone support will set the field
to the special value DC_TIMEZONE_NONE.
The dc_datetime_localtime() and dc_datetime_gmtime() functions will
automatically populate the new field with respectively the local
timezone offset and zero. The dc_datetime_mktime() function will take
into account the new timezone field for the conversion to UTC. The
special value DC_TIMEZONE_NONE is interpreted as zero.
Unlike the corresponding mktime C library function, the libdivecomputer
function will never modify its argument. By marking the parameter as
const this is made more explicit.
The public header files are moved to a new subdirectory, to separate
the definition of the public interface from the actual implementation.
Using an identical directory layout as the final installation has the
advantage that the example code can be build outside the project tree
without any modifications to the #include statements.
