//
//  Filename         : HashGrid.h
//  Author(s)        : Stephane Grabli
//  Purpose          : Class to define a cell grid surrounding the
//                     bounding box of the scene
//  Date of creation : 30/07/2002
//
///////////////////////////////////////////////////////////////////////////////


//
//  Copyright (C) : Please refer to the COPYRIGHT file distributed 
//   with this source distribution. 
//
//  This program is free software; you can redistribute it and/or
//  modify it under the terms of the GNU General Public License
//  as published by the Free Software Foundation; either version 2
//  of the License, or (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef  HASHGRID_H
# define HASHGRID_H

//# if defined(__GNUC__) && (__GNUC__ >= 3)
// hash_map is not part of the C++ standard anymore;
// hash_map.h has been kept though for backward compatibility
//#  include <hash_map.h>
//# else
//#  include <hash_map>
//# endif

# include "Grid.h"
# include <map>
/*! Defines a hash table used for searching the Cells */
struct GridHasher{
#define _MUL 950706376UL
#define _MOD 2147483647UL
  inline size_t operator() (const Vec3u& p) const 
  {
    size_t res = ((unsigned long) (p[0] * _MUL)) % _MOD;
    res = ((res + (unsigned long) (p[1]) * _MUL)) % _MOD;
    return ((res +(unsigned long) (p[2]) * _MUL)) % _MOD;
  }
};

/*! Class to define a regular grid used for ray
  casting computations */

class LIB_GEOMETRY_EXPORT HashGrid : public Grid
{
 public:

  typedef map<Vec3u, Cell*> GridHashTable;
  
  HashGrid() : Grid() {}

  virtual ~HashGrid() {
    clear();
  }

  /*! clears the grid
   *  Deletes all the cells, clears the hashtable,
   *  resets size, size of cell, number of cells.
   */
  virtual void clear();

  /*! Sets the different parameters of the grid
   *    orig
   *      The grid origin
   *    size
   *      The grid's dimensions
   *    nb
   *      The number of cells of the grid
   */
  virtual void configure(const Vec3r& orig, const Vec3r& size, unsigned nb);
  
  /*! returns the cell whose coordinates
   *  are pased as argument
   */
  virtual Cell* getCell(const Vec3u& p) {
    Cell* found_cell = NULL;
    
    GridHashTable::const_iterator found = _cells.find(p);
    if (found != _cells.end())
      found_cell = (*found).second;
    return found_cell;
  }
  
  /*! Fills the case p with the cell iCell */
  virtual void fillCell(const Vec3u& p, Cell& cell) {
    _cells[p] = &cell;
  }

protected:

  GridHashTable _cells;
};

#endif // HASHGRID_H