OptimalHelixPlaneCrossing.h

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#ifndef OptimalHelixPlaneCrossing_H
#define OptimalHelixPlaneCrossing_H


#include "TrackingTools/GeomPropagators/interface/HelixBarrelPlaneCrossingByCircle.h"
#include "TrackingTools/GeomPropagators/interface/HelixForwardPlaneCrossing.h"
#include "TrackingTools/GeomPropagators/interface/HelixArbitraryPlaneCrossing.h"

#include<memory>


class OptimalHelixPlaneCrossing {
public:
  using Base = HelixPlaneCrossing;


  template<typename ... Args>
  OptimalHelixPlaneCrossing(Plane const & plane, Args&&... args) {

    GlobalVector u = plane.normalVector();
    constexpr float small = 1.e-6; // for orientation of planes


    if (std::abs(u.z()) < small) {
      // barrel plane:
      // instantiate HelixBarrelPlaneCrossing,
      new(get()) HelixBarrelPlaneCrossingByCircle(args...);
    }
    else if ( (std::abs(u.x()) < small) & (std::abs(u.y()) < small) ) {
      // forward plane:
      // instantiate HelixForwardPlaneCrossing
      new(get()) HelixForwardPlaneCrossing(args...);
    } else {
      // arbitrary plane:
       // instantiate HelixArbitraryPlaneCrossing
        new(get()) HelixArbitraryPlaneCrossing(args...);
     }
    
  }


  ~OptimalHelixPlaneCrossing() { get()->~Base(); }

  Base & operator*() { return *get(); }
  Base const & operator*() const { return *get();}



  private:


  Base * get() { return (Base*)&mem;}
  Base const * get() const { return (Base const *)&mem;}

  union Tmp { HelixBarrelPlaneCrossingByCircle a; HelixForwardPlaneCrossing b;  HelixArbitraryPlaneCrossing c;};
  using aligned_union_t = typename std::aligned_storage<sizeof(Tmp),alignof(Tmp)>::type;
  aligned_union_t mem;

};



#endif