The dc_parser_set_data() function allows to re-use a parser object for
multiple dives. The advantages of this feature are actually very limited
in practice. The reduction in memory consumption is almost negligible,
because the amount of internal state in the parser is typically very
small. But the implementation requires some additional complexity
because each backend needs code to reset its internal state. Therefore,
the function is removed and the data and size needs to be passed
directly to the dc_parser_new() and dc_parser_new2() functions instead.
Because keeping a reference to the data has also caused issues in the
past, especially for applications implemented in a garbage collected
language, the data will now also get copied internally.
Because the sample struct is passed by value, the size of the structure
can't be changed without also changing the function signature and
breaking backwards compatibility. This prevents adding new fields in the
future, to support some new features.
When passing the sample struct by reference using a pointer, the size of
the pointer does always remains the same.
For gas consumption calculations it's very convenient to know whether a
tank is used for example in a sidemount configuration, or as
oxygen/diluent tank on a rebreather.
For rebreather dives, it's convenient to know whether a gas mix is used
as a closed-circuit mix (oxygen/diluent) or as an open circuit mix
(bailout).
Some dive computers, especially freediving computers, supports multiple
samples per second. Since our smallest unit of time is one second, we
can't represent this, and the extra samples are dropped. Therefore, the
units are changed to milliseconds to prepare supporting this extra
resolution.
The maximum depth value is stored in the dive header. There is no need
to parse the profile data to obtain it. This also avoids returning a
zero depth when the profile data is no longer available.
A few other fields (e.g. average depth, atmospheric pressure and
temperature) are also present in the dive header.
For dive computers where the reference time (epoch) of the device is
unknown, libdivecomputer uses the current time of the device (devtime)
and the host system (systime) to synchronize both clocks.
Currently, both timestamps are passed directly to the constructor of the
parser. With the new public function, the application can adjust the
timestamps afterwards.
Some dive computers store the depth as an absolute pressure value (in
bar). To convert to a depth value (in meters), the atmospheric pressure
and water density are required. For dive computers that do not have
those values available, libdivecomputer uses a default value. With the
new public api functions, applications can adjust those default values.
Some dive computers already provided a backend specific calibration
function. Those functions are now deprecated. They are kept around to
maintain backwards compatibility for now, but they will be removed in
the next version.
The gauge and freedives have a slightly different data format compared
to scuba dives. The main difference is the size of the header and two
new sample types.
The logbook header has 5 bytes extra, which are not present in the dive
header. Those 5 extra bytes contain the dive mode, which is required for
parsing the dive data. Therefore, insert all 5 bytes again and update
the parser.
The remaining 4 bytes appear to be some 32 bit address. They are not
used for anything right now, but are preserved as well in case they are
needed in the future.
The depth value is encoded with only 11 bits instead of 12 bits. The
extra bit contains the gas mix index. This resulted in wrong depths,
with values larger than 204.8m.
