HepMcParticleLinkCnv_p1.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
// Framework includes
#include "GaudiKernel/MsgStream.h"
#include "AthenaKernel/proxyDictFromEventContext.h"
#include "TruthUtils/MagicNumbers.h"
 
// GeneratorObjectsAthenaPool includes
#include "GeneratorObjectsTPCnv/HepMcParticleLinkCnv_p1.h"
#include "GeneratorObjects/McEventCollection.h"

 
 
// In the 21.0 branch an eventIndex of zero means that the transient
// HepMcParticleLink looks at the first event in the
// McEventCollection, otherwise the eventIndex represents the
// GenEvent::event_number of a GenEvent in the McEventCollection and
// this is used to find the appropriate GenEvent.
// NB There is a weakness here that if more than one GenEvent has
// the same event number all links will point to the first GenEvent
// which matches.
 
void HepMcParticleLinkCnv_p1::persToTrans( const HepMcParticleLink_p1* persObj,
                                           HepMcParticleLink* transObj,
                                           MsgStream &/*msg*/ ) const
{
  HepMcParticleLink::PositionFlag flag = HepMcParticleLink::IS_EVENTNUM;
 
  if (persObj->m_mcEvtIndex == 0) {
    flag = HepMcParticleLink::IS_POSITION;
  }
 
  transObj->setExtendedBarCode
    ( HepMcParticleLink::ExtendedBarCode( persObj->m_barcode,
                                          persObj->m_mcEvtIndex,
                                          flag, HepMcParticleLink::IS_BARCODE) ); // FIXME barcode-based
 
  if ( HepMC::BarcodeBased::is_truth_suppressed_pileup(static_cast<int>(persObj->m_barcode)) ) {
    transObj->setTruthSuppressionType(EBC_PU_SUPPRESSED);
  }
}
 
void HepMcParticleLinkCnv_p1::transToPers( const HepMcParticleLink* transObj,
                                           HepMcParticleLink_p1* persObj,
                                           MsgStream &msg ) const
{
  // NB This method assumes that there all GenEvents are stored in a
  // single McEventCollection, as running with split
  // McEventCollections is not supported in 21.0.
  IProxyDict* proxy = Atlas::proxyDictFromEventContext();
  unsigned short index{0};
  const HepMcParticleLink::index_type position =
    HepMcParticleLink::getEventPositionInCollection(transObj->eventIndex(),
                                                    proxy).at(0);
  if (position!=0) {
    index = transObj->eventIndex();
    if(transObj->eventIndex()!=static_cast<HepMcParticleLink::index_type>(index)) {
      msg << MSG::WARNING << "Attempting to persistify an eventIndex larger than max unsigned short!" << endmsg;
    }
  }
  persObj->m_mcEvtIndex = index;
  if (transObj->getTruthSuppressionType() == EBC_PU_SUPPRESSED) {
    persObj->m_barcode = HepMC::SUPPRESSED_PILEUP_BARCODE;
  }
  else {
    persObj->m_barcode = transObj->barcode(); // FIXME in the future the barcode will need to be generated here
  }
}