TPCnvList.h

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// This file's extension implies that it's C, but it's really -*- C++ -*-.
 
/*
  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
*/
 
// $Id$
#ifndef ATHENAPOOLCNVSVC_TPCNVLIST_H
#define ATHENAPOOLCNVSVC_TPCNVLIST_H
 
 
#include "AthenaPoolCnvSvc/TPCnvElt.h"
#include "boost/mpl/vector.hpp"
#include "boost/mpl/transform.hpp"
#include <boost/fusion/mpl.hpp>
#include "boost/fusion/container/vector.hpp"
#include "boost/fusion/container/vector/convert.hpp"
#include "boost/fusion/algorithm/iteration/accumulate.hpp"
 
 
namespace AthenaPoolCnvSvc {
 
 
template <class CNV, class TRANS, class ... TPCNVS>
class TPCnvList
{
  template <class TPCNV>
  struct wrap_tpcnv
  {
    typedef TPCnvElt<CNV, TPCNV> type;
  };
 
 
  struct do_create_transient
  {
    do_create_transient (CNV& parent, const std::string& key, MsgStream& msg);
 
    // FIXME: It would be better to pass a unique_ptr through here.
    // But that requires the resolution of DR2055, which g++ only implements
    // with c++20.
    template <class ELT>
    typename ELT::Trans_t* operator() (typename ELT::Trans_t* p, ELT& elt);
 
    CNV& m_parent;
    const std::string& m_key;
    MsgStream& m_msg;
  };
 
 
  struct do_pers_to_trans
  {
    do_pers_to_trans (CNV& parent, TRANS* trans, const std::string& key, MsgStream& msg);
    
    template <class ELT>
    bool operator() (bool found, ELT& elt);
 
    CNV& m_parent;
    TRANS* m_trans;
    const std::string& m_key;
    MsgStream& m_msg;
  };
 
 
public:
  // Coverity fails to compile this correctly.
#ifndef __COVERITY__
  // Convert the list of TP converters <T1, T2, ...> to a boost fusion vector
  // of converters wrapped by TPCnvElt:
  //   boost::fusion::vector<TPCnvElt<T1>, TPCnvElt<T2>, ...>
  // We can create in instance of this vector to get an object that holds
  // all the TP converter instances.
  typedef boost::mpl::vector<TPCNVS...> vec_t;
  typedef typename boost::mpl::transform<vec_t, wrap_tpcnv<boost::mpl::_1> >::type list_mpl_t;
  typedef typename boost::fusion::result_of::as_vector<list_mpl_t>::type list_t;
#endif
 
 
  std::unique_ptr<TRANS>
  createTransient (CNV& parent, const std::string& key, MsgStream& msg);
 
  
  bool persToTrans (CNV& parent, TRANS* trans, const std::string& key, MsgStream& msg);
  
 
private:
#ifndef __COVERITY__
  list_t m_list;
#endif
};
 
 
} // namespace AthenaPoolCnvSvc
 
 
#include "AthenaPoolCnvSvc/TPCnvList.icc"
 
 
#endif // not ATHENAPOOLCNVSVC_TPCNVLIST_H