For a dive in gauge mode, the gas mixes defined in the header should be
ignored, and no gas change event should be emitted. This is done by
hardcoding the number of gas mixes to zero.
The code to find the offset to the footer and parse the gas mix data is
duplicated in multiple places. Move this code to a single place, and
cache the data in the parser instead.
When using all 16 bits for the temperature, the resulting values are
clearly wrong in some cases. Most likely the upper 4 bits are used to
store something else. Even with only 12 bits, the resulting temperature
range (0-409.5°C) should still be more than sufficient.
If the gas model flag is set to air, the individual gas mix definitions
are ignored, and a single mix with air is returned instead. For non-air
dives, only the gas mixes marked as active are returned.
Currently, each backend has it's own function to verify whether the
object vtable pointer is the expected one. All these functions can be
removed in favor of a single isintance function in the base class,
which takes the expected vtable pointer as a parameter.
Functions which are called through the vtable, don't need to verify the
vtable pointer, and those checks are removed.
The term "backend" can be confusing because it can refer to both the
virtual function table and the device/parser backends. The use of the
term "vtable" avoids this.
I forgot to update the device and parser initialization functions to
store the context pointer into the objects. As a result, the internal
context pointers were always NULL.
The public api is changed to require a context object for all
operations. Because other library objects store the context pointer
internally, only the constructor functions need an explicit context
object as a parameter.
Adding the "dc_" namespace prefix (which is of course an abbreviation
for libdivecomputer) should avoid conflicts with other libraries. For
the time being, only the high-level device and parser layers are
changed.
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.
Correctly skip the 4 byte length in front of the sample data. The
previous code happened to work by accident, because the header after the
sample data was assumed to be 4 bytes larger, and thus those two errors
cancelled each other out.
