BesHepMCInterface.cpp

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#include "G4Svc/BesHepMCInterface.h"
#include "HepMC/GenEvent.h"
 
#include "GaudiKernel/ISvcLocator.h"
#include "GaudiKernel/Bootstrap.h"
#include "GaudiKernel/MsgStream.h"
#include "GaudiKernel/IMessageSvc.h"
 
#include "GeneratorObject/McGenEvent.h"
#include "GaudiKernel/SmartDataPtr.h"
 
BesHepMCInterface::BesHepMCInterface()
{
  p_evtSvc = 0;
}
BesHepMCInterface::~BesHepMCInterface()
{
    //std::cout<< "\b the BesHepMCInterface is being destroyed "<<std::endl;
}
 
HepMC::GenEvent* BesHepMCInterface::GenerateHepMCEvent()
{
  
  if (p_evtSvc == 0) {     
    //std::cout<<" standard interface to EvtDataSvc for retrieving HepMC events"<<std::endl;
    ISvcLocator* svcLocator = Gaudi::svcLocator(); // from Bootstrap
    StatusCode sc=svcLocator->service("EventDataSvc", p_evtSvc);
    if (sc.isFailure()) 
    {
        //std::cout<<"BesHepMCInterface could not access EventDataSvc!!"<<std::endl;
    }
  }
    int n = 0;
  //std::cout <<" BesHepMCInterface::GenerateAnEvent "<<std::endl;
 
    SmartDataPtr<McGenEventCol> mcCollptr( p_evtSvc, "/Event/Gen");
 
    if ( mcCollptr != 0 ) {
      //std::cout <<" could retrieve the collection "<<std::endl;
 
      n = mcCollptr->size();
      
      //std::cout <<" nr of events "<<n<<std::endl;
 
      McGenEventCol::const_iterator it = mcCollptr->begin();
 
      McGenEvent* mcEvent = (McGenEvent* ) (*it);   
      // getting only the first event here.     
      // std::cout <<"iterator"<<std::endl;
        
      HepMC::GenEvent *p_evt;
        
      //std::cout <<"hepmc event"<<std::endl;
      p_evt = mcEvent->getGenEvt();
      //std::cout << "eventNumber = " << p_evt-> event_number()  << std::endl;
 
      //std::cout << " BesHepMCInterface:: --> " <<std::endl;
      //std::cout << " particles_size = " << p_evt->particles_size() 
        //    << " vertices_size = " << p_evt->vertices_size()
        //    << std::endl;
 
      //std::cout <<"got it"<<std::endl;
          
      return p_evt;
    }
 
    else {
      std::cout << "no McGenEventCollection found."  << std::endl;
    }     
      return 0;
}