Robert Ramey ha escrito:
"JOAQUIN LOPEZ MU?Z" wrote:
Hello Robert,
----- Mensaje original ----- De: Robert Ramey <ramey@rrsd.com> Fecha: Domingo, Febrero 3, 2008 8:01 pm Asunto: [boost] question about flyweight Para: boost@lists.boost.org
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b) I'm curious about the serialization implementation. Why didn't you choose just to serialize the factory? This seems to me the most obvious implementation and I wonder why you didn't feel it was a good choice. [...] In short, I don't see why a "helper" is required.
Details aside, it all boils down to this:
ar << f.h;
This only works off the shelf if f.h is a pointer, which is not the case in general (the type of this handle is provided by the particular factory used, and need not be a pointer, for instance in set_factroy is a std::set::iterator). Briefly put, the serialization helper used by flyweight mimics for handle_type the tracking facilities Boost.Serialization provides natively for pointers.
The default is to track if and only if its serialized through a pointer.
If the tracking level serialization trait for flyweight<T> is set to track_always it should work with all objects.
I would think that you could get the effect you intend by just setting this serialization trait.for these types.
I can do something of sorts, but it's not as efficient as with the aid of a helper: Suppose T is tracked, then your proposed approach would be something like this: template< class Archive, typename T,typename Arg1,typename Arg2,typename Arg3
void save( Archive& ar,const ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3>& f, const unsigned int version) { typedef ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3> flyweight; ar << &f.get(); } template< class Archive, typename T,typename Arg1,typename Arg2,typename Arg3
void load( Archive& ar,const ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3>& f, const unsigned int version) { typedef ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3> flyweight; T* p; ar >> p; f=*p; // HERE if(&f.get()!=p){ ar.reset_object_address(&f.get(),p); delete p; } } The problem is with the line marked //HERE : we are incurring a lookup operation for each duplicate flyweight, while this is avoided when a helper is used. As a matter of fact, I measured this approach against the helper implementation and the performance of the latter is easily 2x or 3x better (I don't remember the exact figures, I can retest if you're interested.) Joaquín M López Muñoz Telefónica, Investigación y Desarrollo