[Boost-users] [Serialization, XML] - how to avoid another encoding level

From: Frank Bergemann (FBergemann_at_[hidden])
Date: 2007-03-22 03:39:05

Hi,

i am working with MICO and use boost::serialization (XML) for import/export of CORBA functions IN/OUT parameters, because i have an XML formatted configuration for the data to use for CORBA service invocations.

One of the problems was, that some of the MICO are template'd.
E.g. a data type holding a number of digits (e.g. telephone #no) is encoded in MICO as:

template <class T, int TID, int max>
class BoundedSequenceTmpl {
    ...
}

... using basic <class T> = CORBA::Short for digits (e.g.).

1st i used ToString(...)/fromString(...) functions to be able to save&load such to/from boost archives. And this worked - though it had the little drawback, that i needed to use additional variables in load() & save() to handle it this way.

But then next it came up, that some other CORBA data types use the BoundedSequenceTempl<> as well, but for _more complex_ <class T> - e.g. BoundedSequenceTempl<> of BoundedSequenceTempl<>.

For that i created a version of serialize(), save() & load() like this:

template<class Archive, class T, int TID, int max>
void serialize(Archive & ar,
                BoundedSequenceTmpl<T, TID, max> &p,
                const unsigned int version)
{
   split_free(ar, p, version);
}
           
template<class Archive,class T, int TID, int max>
void save(Archive & ar,
          const BoundedSequenceTmpl<T, TID, max> &p,
          const unsigned int version)
{
   unsigned long length = p.length();
   ar & make_nvp("length", length);
   for (unsigned long i = 0; i < length; ++i) {
      std::ostringstream name;
      name << "item_" << i;
      ar & make_nvp(name.str(), p[i]);
   }                   
}
           
template<class Archive, class T, int TID, int max>
void load(Archive & ar,
          BoundedSequenceTmpl<T, TID, max> &p,
          const unsigned int version)
{
   unsigned long length;
   ar & make_nvp("length", length);
   p.length(length);
   for (unsigned long i = 0; i < length; ++i)    {
    std::ostringstream name;
    name << "item_" << i;
    ar & make_nvp(name.str(), p[i]);
   }
}

then i thought i can get rid of the formerly used ToString(...)/FromString(...) helpers and replace them by overloaded versions of the new (more generic) load() & save() variants dedicated for this BoundedSequenceTempl<...>.

Like this:
#if 0
// This was intended to make obsolete MicoVector_to_string(...) &
// MicoVector_from_string(...)
// kind of "template specialization" for the ones above
// for BoundedSequenceTmpl<...> of types, which we don't want
// to be spread out any further
//
// But i couldn't make this work.
// Means: it compiles. But it implies another XML encoding level
// - which is not what i want
       
template<class Archive, int TID, int max>
void serialize(Archive & ar,
               BoundedSequenceTmpl<CORBA::Short, TID, max> &p,
               const unsigned int version)
{
   split_free(ar, p, version);
}

template<class Archive, int TID, int max>
void save (Archive & ar,
           const BoundedSequenceTmpl<CORBA::Short, TID, max> &p,
           const unsigned int version)
{
           
  std::ostringstream ostream;
           
  for (unsigned long i=0; i<p.length(); ++i) {
     ostream << p[i];
  }
           
  // tried this, but it didn't work (compilation failed):
  ar & str;

  // so i tested this option
  std::string str(ostream.str());
  ar & make_nvp("hallo", str);  // CREATES ANOTHER ENCODING LEVEL :-(

}                                                       

template<class Archive, int TID, int max>
void load (Archive & ar,
           BoundedSequenceTmpl<CORBA::Short, TID, max> &p,
           const unsigned int version)
{
   ...
}                                                               
#endif        

But that created me another level of encoding - which i don't want.

E.g. having a superior encoder:

template<class Archive>
void save(Archive & ar,
          const DeleteHlrSubscriber_s &pInstance,
          const unsigned int version)
{
  std::string simsi;
  std::string smsisdn;
           
  MicoVector_to_string(pInstance.imsi, simsi);
  MicoVector_to_string(pInstance.msisdn, smsisdn);
           
  // ar & make_nvp("imsi", simsi); // replace by the next...

  // this worked, but see above (the by "#if 0" disabled stuff)
  ar & make_nvp("imsi", pInstance.imsi);

  ar & make_nvp("msisdn", smsisdn);
  ar & make_nvp( "attach_imsi", pInstance.attach_imsi);

}

using pInstance.imsi directly (which is a BoundedSequenceTmpl<CORBA::Short>()) resulted in:

<imsi> // dropped boost::serializations internal XML attributes here
  <hallo>SomeString</hallo>
</imsi>

But I would like to have this one

<imsi>SomeString</imsi>

How can i do that?

Thanks!

Best regards!

Frank

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