[C++-sig] optimizing away calls to the python runtime -- was [detecting if a function is written in python or C++]

[Mathieu Lacage]

On Wed, 2006-01-18 at 15:09 -0500, François Duranleau wrote:

> You can do something similar with methods by adding a member 'self' in the 
> wrapper (pointer to the object), a constructor with the object to bind to 
> the method as an argument, and calling the method with ->. in operator(). 
> Actually, I think you could even have a single wrapper for both functions 
> and method using boost::function and boost::bind.


I ended up doing this:
template<typename TAG, typename R, typename T, typename T1>
struct CallbackGenerator {
        typedef R (T::*member_type) (T1);
        static std::auto_ptr<Callback<R (T1)> >
        make_callback (T *self){
                return std::auto_ptr<Callback<R (T1)> > (yans::make_callback (CallbackGenerator::m_member, self));
        }
        static member_type m_member;
};
template<typename TAG,typename R,typename T,typename T1>
R (T::* CallbackGenerator<TAG,R,T,T1>::m_member ) (T1);

template <typename TAG, typename R, typename T, typename T1>
void
export_method_as_callback (R (T::*member) (T1), char const *name)
{
        CallbackGenerator<TAG, R, T, T1>::m_member = member;
        def (name, &CallbackGenerator<TAG,R,T,T1>::make_callback);
        class_<Callback<R (T1)>, std::auto_ptr<Callback<R (T1)> >, boost::noncopyable> ("Callback", no_init);
}


with this:

        export_method_as_callback<struct foo> (&TrafficAnalyser::receive,
                                               "make_TrafficAnalyser_receive_callback");


and that:

void set_send_callback_cpp (PeriodicGenerator *self, std::auto_ptr<Callback<void (Packet *)> > *callback)
{
        self->set_send_callback (callback->get ());
        callback->release ();
}

and this results in this:
without the call to export_method_as_callback:
[mlacage at chronos yans-current]$ time -p ./bin/python/test-periodic-generator.py >/dev/null
real 12.96
user 12.81
sys 0.02

with the call:
[mlacage at chronos yans-current]$ time -p ./bin/python/test-periodic-generator.py >/dev/null
real 3.10
user 2.99
sys 0.01

which I think is very nice.

thanks again for your help,
Mathieu
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