G4ReduciblePolygon.hh

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//
// G4ReduciblePolygon
//
// Class description:
//
//   Utility class used to specify, test, reduce, and/or otherwise
//   manipulate a 2D polygon.
//
//   For this class, a polygon consists of n > 2 points in 2D
//   space (a,b). The polygon is always closed by connecting the
//   last point to the first. A G4ReduciblePolygon is guaranteed
//   to fulfill this definition in all instances. 
//
//   Illegal manipulations (such that a valid polygon would be
//   produced) result in an error return if possible and 
//   otherwise a G4Exception.
//
//   The set of manipulations is limited currently to what
//   is needed for G4Polycone and G4Polyhedra.

// Author: David C. Williams (davidw@scipp.ucsc.edu)
// --------------------------------------------------------------------
#ifndef G4REDUCIBLEPOLYGON_HH
#define G4REDUCIBLEPOLYGON_HH

#include "G4Types.hh"

class G4ReduciblePolygon
{
  friend class G4ReduciblePolygonIterator;

  public:
    //
    // Creator: via simple a/b arrays
    //
    G4ReduciblePolygon( const G4double a[], const G4double b[], G4int n );
  
    //
    // Creator: a special version for G4Polygon and G4Polycone
    // that takes two a points at planes of b
    // (where a==r and b==z for the GEANT3 classic PCON and PGON)
    //
    G4ReduciblePolygon( const G4double rmin[], const G4double rmax[],
                        const G4double z[], G4int n );
  
    virtual ~G4ReduciblePolygon();
  
    //
    // Queries
    //
    inline G4int NumVertices() const { return numVertices; }
  
    inline G4double Amin() const { return aMin; }
    inline G4double Amax() const { return aMax; }
    inline G4double Bmin() const { return bMin; }
    inline G4double Bmax() const { return bMax; }
  
    void CopyVertices( G4double a[], G4double b[] ) const;

    //
    // Manipulations
    //
    void ScaleA( G4double scale );
    void ScaleB( G4double scale );
  
    G4bool RemoveDuplicateVertices( G4double tolerance );
    G4bool RemoveRedundantVertices( G4double tolerance );
  
    void ReverseOrder();
    void StartWithZMin();

    //
    // Tests
    //
    G4double Area();
    G4bool CrossesItself( G4double tolerance );
    G4bool BisectedBy( G4double a1, G4double b1,
           G4double a2, G4double b2, G4double tolerance );
   
    void Print();  // Debugging only
  
  public:  // without description

    G4ReduciblePolygon(__void__&);
      // Fake default constructor for usage restricted to direct object
      // persistency for clients requiring preallocation of memory for
      // persistifiable objects.

  protected:
  
    void Create( const G4double a[], const G4double b[], G4int n );
  
    void CalculateMaxMin();
  
    //
    // Below are member values that are *always* kept up to date (please!)
    //
    G4double aMin, aMax, bMin, bMax;
    G4int numVertices = 0;
  
    //
    // A subclass which holds the vertices in a single-linked list
    //
    // Yeah, call me an old-fashioned c hacker, but I cannot make
    // myself use the rogue tools for this trivial list.
    //
    struct ABVertex;              // Secret recipe for allowing
    friend struct ABVertex;       // protected nested structures
    struct ABVertex
    {
      ABVertex() : a(0.), b(0.), next(0) {}
      G4double a, b;
      ABVertex *next;
    };
  
    ABVertex* vertexHead = nullptr;

    private:

      G4ReduciblePolygon(const G4ReduciblePolygon&);
      G4ReduciblePolygon& operator=(const G4ReduciblePolygon&);
      // Private copy constructor and assignment operator.
};

// A companion class for iterating over the vertices of our polygon.
// It is simple enough that all routines are declared inline here.
//
class G4ReduciblePolygonIterator
{
  public:

    G4ReduciblePolygonIterator( const G4ReduciblePolygon* theSubject )
     { subject = theSubject; current = nullptr; }
  
    void  Begin() { current = subject->vertexHead; }  
    G4bool  Next()
    {
      if (current != nullptr) current=current->next;
      return Valid();
    }
  
    G4bool  Valid() const { return current != nullptr; }  
  
    G4double GetA() const { return current->a; }
    G4double GetB() const { return current->b; }
  
  protected:

    const G4ReduciblePolygon* subject = nullptr;  // Who are we iterating over
    G4ReduciblePolygon::ABVertex* current = nullptr;  // Current vertex
};

#endif