peano_curve.hpp

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/******************************************************************************
** Copyright © 2002 by J.M.McGuiness, coder@hussar.me.uk
**
** This library is free software; you can redistribute it and/or
** modify it under the terms of the GNU Lesser General Public
** License as published by the Free Software Foundation; either
** version 2.1 of the License, or (at your option) any later version.
**
** This library 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
** Lesser General Public License for more details.
**
** You should have received a copy of the GNU Lesser General Public
** License along with this library; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
 
#pragma once
 
#include "ttypes.hpp"
 
#include <cassert>
#include <list>
 
namespace jmmcg { namespace LIBJMMCG_VER_NAMESPACE {
 
   class PeanoCurve {
   private:
      enum elements {
         green_right_curve=0,
         red_right_curve,
         green_left_curve,
         red_left_curve,
         green_straight,
         red_straight
      };
 
   public:
      enum directions {
         north=0,
         east,
         south,
         west
      };
 
      struct curve_element {
         elements elem;
         directions dir;
 
         curve_element(const elements e,const directions d) noexcept(true)
         : elem(e),dir(d) {
         }
      };
 
      typedef std::list<curve_element> curve;
 
      PeanoCurve(void) {
         ZeroCurve();
      }
      explicit PeanoCurve(const curve &c,const unsigned long d=0)
      : peano(c),depth(d) {
      }
      ~PeanoCurve(void) {
      }
 
      void Create(const unsigned long d) {
         if (depth>d) {
            ZeroCurve();
         }
         if (depth<d) {
            for (unsigned long i=depth;i<d;++i) {
               curve::iterator element(peano.end());
               do {
                  ReplaceElement(--element);
               } while (element!=peano.begin());
            }
            depth=d;
         }
         assert(!peano.empty());
      }
 
      unsigned long Depth(void) const noexcept(true) {
         return depth;
      }
 
      const curve &Curve(void) const noexcept(true) {
         return peano;
      }
 
   private:
      typedef curve_element replace_element[4];
      typedef replace_element dir_replacements[6];
 
      static const dir_replacements replacements[];
      curve peano;
      unsigned long depth;
 
      void ZeroCurve(void) {
         peano.clear();
         peano.push_back(curve_element(red_right_curve,east));
         peano.push_back(curve_element(green_right_curve,south));
         peano.push_back(curve_element(red_right_curve,west));
         peano.push_back(curve_element(green_right_curve,north));
         depth=0;
      }
 
      void ReplaceElement(curve::iterator &element) {
         const dir_replacements &replacement_curves=replacements[element->dir];
         const replace_element &replacement_curve=replacement_curves[element->elem];
         *element=replacement_curve[3];
         element=peano.insert(element,replacement_curve[2]);
         element=peano.insert(element,replacement_curve[1]);
         element=peano.insert(element,replacement_curve[0]);
      }
 
   };
 
} }