Registering user-supplied derived types with Boost Serialization

Question

I am writing a library that will handle storing and serializing custom types. Custom types must be serializable.

However, the library uses templates to create user type containers. I don't know how to export container types to speed up :: serialization through templates. The only way to do this is to force the library user BOOST_CLASS_EXPORT_GUID () of each container type.

I tried to unzip the macro by looking at boost / serialization / export.hpp, but it's a bit complicated ... Is there a way to export the class as part of a template instance? Or another way to write a library to easily serialize custom type containers?

#include <iostream>
#include <vector>

#include <boost/foreach.hpp>
#include <boost/serialization/access.hpp>
#include <boost/serialization/vector.hpp>
#include <boost/serialization/base_object.hpp>
#include <boost/serialization/export.hpp>

#include <boost/archive/text_oarchive.hpp>

//////////////////////////////////////////////////////////////////////////////
// Example code that would reside in the library
//////////////////////////////////////////////////////////////////////////////

struct type_container_base {
private:
    virtual void make_abstract() const {}
    friend class ::boost::serialization::access;
    template <typename ARCHIVE>
    void serialize(ARCHIVE &, const unsigned int) {}    
};

BOOST_SERIALIZATION_ASSUME_ABSTRACT(type_container_base)

template <typename USER_TYPE>
struct type_container : type_container_base {
    void add(const USER_TYPE& d) { _vector.push_back(d); }
private:
    std::vector<USER_TYPE> _vector;
    friend class ::boost::serialization::access;
    template <typename ARCHIVE>
    void serialize(ARCHIVE & ar, const unsigned int) {
        ar & ::boost::serialization::base_object<type_container_base>(*this);
        ar & _vector;
    }
};

//////////////////////////////////////////////////////////////////////////////
// Example user code that would use the library
//////////////////////////////////////////////////////////////////////////////

struct user_type {
    user_type(int i) : _val(i) {}
private:
    int _val;
    friend class ::boost::serialization::access;
    template <typename ARCHIVE>
    void serialize(ARCHIVE & ar, const unsigned int) {
        ar & _val;
    }
};

// *** Is there a better way than forcing the user to do this for every
// *** user_type they want to use with the library?
BOOST_CLASS_EXPORT_GUID(type_container<user_type>, "type_container<user_type>")

int main() {
    std::vector<type_container_base*> containers;
    type_container<user_type>* tc = new type_container<user_type>();
    tc->add(user_type(7));
    tc->add(user_type(42));
    tc->add(user_type(1776));
    containers.push_back(tc);
    {
        boost::archive::text_oarchive ar(std::cout);
        const std::size_t size = containers.size();
        ar << size;
        BOOST_FOREACH(type_container_base* p, containers)
            ar << p;
    }
    return 0;
}

Answer 1

, - :

#define BOOST_CLASS_TEMPLATE_EXPORT_IMPLEMENT(T)             \
    namespace boost {                                        \
    namespace archive {                                      \
    namespace detail {                                       \
    namespace {                                              \
    template<typename U>                                     \
    struct init_guid< T<U> > {                               \
        static guid_initializer< T<U> > const & g;           \
    };                                                       \
    template<typename U>                                     \
    guid_initializer< T<U> > const & init_guid< T<U> >::g =  \
        ::boost::serialization::singleton<                   \
            guid_initializer< T<U> >                         \
        >::get_mutable_instance().export_guid();             \
    }}}}                                                     \
/**/

#define BOOST_CLASS_TEMPLATE_EXPORT_KEY2(T, K) \
namespace boost {                              \
namespace serialization {                      \
template<typename U>                           \
struct guid_defined< T<U> > : boost::mpl::true_ {}; \
template<typename U>                           \
inline const char * guid< T<U> >(){            \
    return K + "<" + guid<U>() + ">"; //this doesn't work, I know! \
}                                              \
} /* serialization */                          \
} /* boost */                                  \
/**/

#define BOOST_CLASS_TEMPLATE_EXPORT_KEY(T)                             \
    BOOST_CLASS_TEMPLATE_EXPORT_KEY2(T, BOOST_PP_STRINGIZE(T))                                                         \
/**/

#define BOOST_CLASS_TEMPLATE_EXPORT_GUID(T, K)                         \
BOOST_CLASS_TEMPLATE_EXPORT_KEY2(T, K)                                 \
BOOST_CLASS_TEMPLATE_EXPORT_IMPLEMENT(T)                               \
/**/

. , , , user_type . , , , , - , ( X ).

, , // , Boost.Serialization(, ).