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Re: New public API
On Mon, 2006-02-20 at 11:00 -0800, Ilya A. Volynets-Evenbakh wrote:
> One thing I was thinking about (and even started using in some cases)
> is to change methods returing collections. The way it is now:
> virtual std::vector<std::string> getAttributeNames()
> This means that whole vector, as well as every string inside will be copied
> (possibly twice - inside function when creating retval, and then to the
> actual
> return value). Now, instead we could change signiture as follows:
> virtual void getAttributeNames(std::vector<std::string> &out)
> This will avoid unnessesary copying.
>
> Java does not have to worry about it, since it returns references, and thus
> only one copy of object is created.
It is possible for a STL implementation to user reference counting in
vector's copy constructor, thought the SGI's STL does simple copying.
It is as well possible for the compiler to use return value optimization
[1], thought it is not always possible to write the getters in a way
which allows RVO.
Another option would be to use std::auto_ptr [2] or boost::shared_ptr
[3].
I would like to keep the API as close to the Java version as it is
possible. So I'd rather stick with option 1 (ignore the problem) or 2
user some sort of reference counting.
[1] http://cpptips.hyperformix.com/cpptips/ret_val_opt
[2] http://gcc.gnu.org/onlinedocs/libstdc
++/latest-doxygen/classstd_1_1auto__ptr.html
[3] http://www.boost.org/libs/smart_ptr/shared_ptr.htm