Event/GeneratorObject/include/GeneratorObject/HepMcParticleLink.h

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#ifndef GENERATOROBJECTS_HEPMCPARTICLELINK_H
#define GENERATOROBJECTS_HEPMCPARTICLELINK_H
/** @class HepMcParticleLink
 * @brief a link optimized in size for a GenParticle in a McEventCollection
 *
 * @see McEventCollection, GenEvent, ElementLink
 * @author Paolo Calafiura
 * $Id: HepMcParticleLink.h,v 1.1.1.1 2004/09/28 06:40:36 liwd Exp $
 **/
#include <cassert>
 
namespace HepMC {
  class GenParticle;
  class GenEvent;
} // namespace HepMC
 
class HepMcParticleLink {
public:
  typedef unsigned int index_type;
 
  /// \name structors
  //@{
  HepMcParticleLink() : m_particle( 0 ), m_extBarcode() {}
  HepMcParticleLink( index_type barCode, index_type eventIndex = 0 )
      : m_particle( 0 ), m_extBarcode( barCode, eventIndex ) {}
  HepMcParticleLink( const HepMC::GenParticle* p, index_type eventIndex = 0 );
  HepMcParticleLink( const HepMcParticleLink& rhs )
      : m_particle( rhs.m_particle ), m_extBarcode( rhs.m_extBarcode ) {}
  HepMcParticleLink( const HepMC::GenParticle* part,
                     const HepMC::GenEvent*    pevt ); // FIXME NOT YET
  //@}
 
  /// \name pointer interface
  //@{
  /// @throws std::runtime_error when the element is not found
  const HepMC::GenParticle& operator*() const { return *cptr(); } // FIXME
  const HepMC::GenParticle* operator->() const { return cptr(); }
  operator const HepMC::GenParticle*() const { return cptr(); }
  bool operator!() const { return !isValid(); }
  //@}
 
  /// \name indexing accessors (e.g. for writing)
  //@{
  int        barcode() const { return m_extBarcode.barcode(); }
  index_type eventIndex() const { return m_extBarcode.eventIndex(); }
  //@}
 
  bool                      isValid() const { return ( 0 != cptr() ); }
  const HepMC::GenParticle* cptr() const;
 
private:
  class ExtendedBarCode {
  public:
    ExtendedBarCode() : m_extBC( 0 ) {}
    ExtendedBarCode( index_type barcode, index_type eventIndex ) {
      assert( barcode < 0x1FFFFF ); // this is (1 << 21) - 1
      assert( eventIndex < 0x7FF ); // this is (1 << 11) - 1
      m_extBC = barcode + ( eventIndex << 21 );
    }
    ExtendedBarCode( const ExtendedBarCode& rhs ) : m_extBC( rhs.m_extBC ) {}
 
    int        barcode() const { return m_extBC & 0x1FFFFF; }
    index_type eventIndex() const { return m_extBC >> 21; }
 
  private:
    //    mutable int m_barcode : 21;   //FIXME HepMC
    //    unsigned int m_eventIndex: 11;
    unsigned int m_extBC;
  };
  mutable HepMC::GenParticle* m_particle; /* transient */
  ExtendedBarCode             m_extBarcode;
};
 
#endif