Question

I’m trying to serialize my data structures in order to write them to a tcp socket.

So far I found that my problem is the serialization. I even tried to use

BOOST_SERIALIZATION_ASSUME_ABSTRACT(T)

but I can’t find any working example similar to my program and how to implement it correctly.

Here are some of the links that I have visited:

• http://programmers-blog.com/category/c-c
• http://www.boost.org/doc/libs/1_48_0/libs/serialization/doc/tutorial.html#simplecase
• http://en.highscore.de/cpp/boost/serialization.html#serialization_class_hierarchies

My data structures are a little more complicated then this one but let’s assume that I have the following structure

Coordinate.h

#include <boost\archive\text_iarchive.hpp>
#include <boost\archive\text_oarchive.hpp>

class Coordinate {
public:
    Coordinate() {}
    Coordinate(int c) : c(c) {}
    int get(void) { return c; }
    std::string toString(void);
private:
    int c;
    friend class boost::serialization::access;
    template<typename Archive>
    void serialize(Archive &ar, const unsigned int version) {
        ar & this->c;
    }
};

Move.h

class Coordinate;

#include "Coordinate.h"

#include <boost\archive\text_iarchive.hpp>
#include <boost\archive\text_oarchive.hpp>

class Move {
public:
    Move() {}
    ~Move() {}
    Coordinate* getCoordinate(void) {return this->destination; }
    virtual bool isJump(void) = 0;
protected:
    Coordinate *destination;
private:
    friend class boost::serialization::access;
    template<typename Archive>
    void serialize(Archive &ar, const unsigned int version) {
        ar & this->destination;
    }
};

MoveNormal.h

class Coordinate;

#include "Move.h"
#include "Coordinate.h"

#include <boost\archive\text_iarchive.hpp>
#include <boost\archive\text_oarchive.hpp>

class MoveNormal : public Move {
public:
    MoveNormal() {}
    MoveNormal(Coordinate *destination) { this->destination = destination; }
    ~MoveNormal() {}
    virtual bool isJump(void);
private:
    friend class boost::serialization::access;
    template<typename Archive>
    void serialize(Archive &ar, const unsigned int version) {
        ar & boost::serialization::base_object<Move>(*this);
    }
};

The virtual methods are defined in here.

MoveNormal.cpp

#include "MoveNormal.h"

bool MoveNormal::isJump(void) {
    return false;
}

My main.cpp looks like this:

#include "Coordinate.h"
#include "Move.h"
#include "MoveNormal.h"

#include <fstream>

#include <boost\archive\text_iarchive.hpp>
#include <boost\archive\text_oarchive.hpp>

int main(int argc, char *argv[]) {
    Coordinate *c = new Coordinate(10);
    // This runs OK
    /*
    {
        std::ofstream ofs("f.txt");
        boost::archive::text_oarchive oa(ofs);
        oa << c;
    }
    Coordinate *d;
    {
        std::ifstream ifs("f.txt");
        boost::archive::text_iarchive ia(ifs);
        ia >> d;
    }
    std::cout << "c.get(): " << c->get() << std::endl;
    std::cout << "d.get(): " << d->get() << std::endl;
    */

    // This is where I get my error
    Move *m  = new MoveNormal(c);
    {
        std::ofstream ofs("f.txt");
        boost::archive::text_oarchive oa(ofs);
        oa << m;    // Line where the error occurs
    }
    return 0;
}

But when I run the program I get the following error:

Unhandled exception at 0x76dbb9bc in Test.exe: Microsoft C++ exception: boost::archive::archive_exception at memory location 0x001df078..

I’m using VS2010, and Boost 1.48.0.

Answer 1

This is a little bit weird but I’m going to answer my own question. I just figured out how to make my example above work.

Here it goes the solution. Everytime we need to serialize a class that inherits attributes from another class we need to use the macro:

BOOST_CLASS_EXPORT(T)

According to the boost serialization doc

BOOST_CLASS_EXPORT in the same source module that includes any of the archive class headers will instantiate code required to serialize polymorphic pointers of the indicated type to the all those archive classes. If no archive class headers are included, then no code will be instantiated.

Note that the implemenation of this functionality requires that the BOOST_CLASS_EXPORT macro appear after and the inclusion of any archive class headers for which code is to be instantiated.

So in my case my main.cpp file is now:

#include <fstream>

#include <boost\archive\text_iarchive.hpp>
#include <boost\archive\text_oarchive.hpp>
#include <boost\serialization\export.hpp>

#include "Coordinate.h"
#include "Move.h"
#include "MoveNormal.h"
BOOST_CLASS_EXPORT(MoveNormal)

int main(int argc, char *argv[]) {
    Coordinate *c = new Coordinate(150);
    Move *m = new MoveNormal(c);
    std::cout << "m.getDestination().get(): " << m->getDestination()->get() << std::endl;
    {
        std::ofstream ofs("f.txt");
        boost::archive::text_oarchive oa(ofs);
        oa << m;
    }

    Move *n;
    {
        std::ifstream ifs("f.txt");
        boost::archive::text_iarchive ia(ifs);
        ia >> n;
    }
    std::cout << "n.getDestination().get(): " << n->getDestination()->get() << std::endl;
    return 0;
}

Just make sure that you include all the boost archives you need before you use the export MACRO.

To finish my project besides the serialization I need to write them to a tcp socket using boost::asio.

So let’s assume that I have a connection header like this one and that now I have another class called MoveJump defined in my MoveJump.h

#include <boost\archive\text_iarchive.hpp>
#include <boost\archive\text_oarchive.hpp>

#include "Coordinate.h"
#include "Move.h"

class MoveJump : public Move {
public:
    MoveJump() {}
    MoveJump(Coordinate *c) { this->destinatio = c; }
    ~MoveJump() {}
    virtual bool isJump(void);
private:
    friend class boost::serialization::access;
    template<typename Archive>
    void serializize(Archive &ar, const unsigned int version) {
        ar & boost::serialization::base_object<Move>(*this);
    }
};

Now to serialize these structures my main look like this

#include <boost\archive\text_iarchive.hpp>
#include <boost\archive\text_oarchive.hpp>
#include <boost\serialization\export.hpp>

#include <fstream>

#include "Coordinate.h"
#include "Move.h"
// And now we register all the possible Moves
#include "MoveNormal.h"
BOOST_CLASS_EXPORT(MoveNormal)
#include "MoveJump.h"
BOOST_CLASS_EXPORT(MoveJump)

int main(int argc, char *argv[]) {
    Coordinate *c = new Coordinate(10);
    Move *m = new MoveNormal(c);
    Coordinate *d = new Coordinate(15);
    Move *j = new MoveJump(d);
    {
        std::ofstream ofs("m.txt");
        boost::archive::text_oarchive oa(ofs);
        oa << m;
    }
    {
        std::ofstream ofs("j.txt");
        boost::archive::text_oarchive oa(ofs);
        oa << j;
    }
}

The trick is to register the classes that will be serialized when we have the pointer to the base class.

If inside my Move.h I have more pointers to other base classes, which I do in my project, we need to include in the main all the headers and register all the possible classes that expand the base class.

I hope this helps someone who might have similar problems in the future.

Feel free to present new possible solutions.

Thanks