Peter Dimov wrote:
David Abrahams wrote:
We want to be able to capitalize on the existence of those APIs, and to do that we need a "hook" that will be used whenever a contiguous sequence is going to be (de)serialized. No such hook exists in Boost.Serialization.
[snip]
Looking at collections_save_imp.hpp:
template<class Archive, class Container> inline void save_collection(Archive & ar, const Container &s)
[...]
all that needs to be done is:
template<class Archive, class It> inline void save_sequence(Archive & ar, It it, unsigned count) { while(count-- > 0){ //if(0 == (ar.get_flags() & boost::archive::no_object_creation)) // note borland emits a no-op without the explicit namespace boost::serialization::save_construct_data_adl(ar, &(*it), 0U); ar << boost::serialization::make_nvp("item", *it++); } }
template<class Archive, class Container> inline void save_collection(Archive & ar, const Container &s) { // record number of elements unsigned int count = s.size(); ar << make_nvp("count", const_cast<const unsigned int &>(count)); save_sequence( ar, s.begin(), count ); }
unless I'm missing something fundamental.
So what's all the fuss about?
That isn't quite all that needs to be done. (1) minor nit: an interface that uses (iterator, size) would be better than a container-based algorithm because that would make it easier to do optimizations based on the iterator type (eg, memcpy, or MPI operations in the case of a pointer, or maybe some kind of distributed iterator in combination with a parallel IO library?). Also, the collection isn't necessarily in the form of a container (although a proxy container would probably suffice for that case, and come to think of it, to handle resizing the container on load it might actually be preferable). (2) another minor nit: it is probably more convenient to handle the details of save_sequence() inside the archive (similarly to other primitive types), rather than as a free function. (3) : save_collection() [or some functional equivalent] isn't part of the public interface of the serialization library. For whatever reason this seems to be the sticking point. Making it an optional add-on is OK, but you really want people to use it _by default_, otherwise you need to go and rewrite all their serialization functions to make use of whatever additional functionality the archive provides. Cheers, Ian