BesHepMCInterface.cpp

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#include "BesHepMCInterface.h"
#include "HepMC/GenEvent.h"
 
#include "GaudiKernel/Bootstrap.h"
#include "GaudiKernel/IMessageSvc.h"
#include "GaudiKernel/ISvcLocator.h"
#include "GaudiKernel/MsgStream.h"
 
#include "GaudiKernel/SmartDataPtr.h"
#include "GeneratorObject/McGenEvent.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;
}