Re: [Boost-users] [serialization] serializing dynamic arrays

From: Robert Ramey (ramey_at_[hidden])
Date: 2005-07-09 23:42:05

I believe your example should work as written. Where does it fail?

Robert Ramey

Ivan Rachev wrote:
> Does anyone have an idea how to serialize dynamic arrays of objects?
>
> An example follows at the end. Its weakness shows up when an outside
> pointer points to an element in the array. The problem is that the
> type being serialized is T but not T*.
>
> Thanks,
> Ivan
>
>
>
>
> #include <fstream>
>
> #include <boost/archive/text_iarchive.hpp>
> #include <boost/serialization/access.hpp>
> #include <boost/serialization/split_member.hpp>
>
> class A
> { friend class boost::serialization::access;
>    template<class Archive>
>    void serialize(Archive & ar, const unsigned int version) {}
> };
>
> //IVAN Element always points to the beginning of an array of
> //     'Size' elements. The array is NOT null-terminated. If
> //     size == 0, Elements may hold an undefined value. User
> //     is responsible for initializing, new-ing and delete-ing.
> //     Assumption: if there is an outside pointer to an object
> //                 inside this array, after loading the array
> //                 that pointer will hold a different object.
> template <typename T>
> struct DynamicArray
> {
>    int Size;
>    T* Element;
>
>    friend class boost::serialization::access;
>    template<class Archive>
>    void save(Archive & ar, const unsigned int version) const
>    {
>      ar & Size;
>      for (int i = 0; i < Size; ++i)
>        ar & Element[i];
>    }
>    template<class Archive>
>    void load(Archive & ar, const unsigned int version)
>    {
>      ar & Size;
>      //TODO: assert(Size >=0);
>      if (Size > 0)
>        {
>        Element = new T[Size];
>        for (int i = 0; i < Size; ++i)
>          ar & Element[i];
>        }
>    }
>    BOOST_SERIALIZATION_SPLIT_MEMBER()
> };
>
> int main()
> {
>    DynamicArray<A> ArrayOfAs;
>    A* secondElement;
>
>    std::ifstream ifs("test.txt");
>    boost::archive::text_iarchive ia(ifs);
>    ia & ArrayOfAs;
>    ia & secondElement; // this guy will point to a copy of the
>                        // 2nd element but NOT the 2nd element itself
>
>    delete [] ArrayOfAs.Element;
> }