/home/andreas/src/svn/mapnik/include/mapnik/quad_tree.hpp

Go to the documentation of this file.

/*****************************************************************************
 * 
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2006 Artem Pavlenko
 *
 * 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/
//$Id$

#ifndef QUAD_TREE_HPP
#define QUAD_TREE_HPP
// stl
#include <vector>
// boost
#include <boost/ptr_container/ptr_vector.hpp>
#include <boost/noncopyable.hpp>
// mapnik
#include <mapnik/envelope.hpp>

namespace mapnik
{
   template <typename T>
   class quad_tree : boost::noncopyable
   {
         struct node
         {
               typedef T value_t;
               typedef std::vector<T> cont_t;
               typedef typename cont_t::iterator iterator;
               typedef typename cont_t::const_iterator const_iterator;
               Envelope<double> extent_;
               cont_t cont_;
               node * children_[4];

               explicit node(Envelope<double> const& ext)
                  : extent_(ext)
               {
                  std::memset(children_,0,4*sizeof(node*));
               }
   
               Envelope<double> const& extent() const
               {
                  return extent_;
               }
            
               iterator begin() 
               {
                  return cont_.begin();
               }
            
               const_iterator begin() const 
               {
                  return cont_.begin();
               }
            
               iterator end() 
               {
                  return cont_.end();
               }
            
               const_iterator end() const 
               {
                  return cont_.end();
               }
               ~node () {}
         };
        
         typedef boost::ptr_vector<node> nodes_t;       
         typedef typename node::cont_t cont_t;
         typedef typename cont_t::iterator node_data_iterator;
        
         nodes_t nodes_;
         node * root_;  
         const double ratio_; 
        
      public:
         typedef typename nodes_t::iterator iterator;
         typedef typename nodes_t::const_iterator const_iterator;
         typedef typename boost::ptr_vector<T,boost::view_clone_allocator> result_t;    
         typedef typename result_t::iterator query_iterator;
   
         result_t query_result_;
        
         explicit quad_tree(Envelope<double> const& ext,double ratio=0.55) 
            : ratio_(ratio)
         {
            nodes_.push_back(new node(ext));
            root_ = &nodes_[0];
         }
                
         void insert(T data, Envelope<double> const& box)
         {
            do_insert_data(data,box,root_);
         }
        
         query_iterator query_in_box(Envelope<double> const& box)
         {
            query_result_.clear();
            query_node(box,query_result_,root_);
            return query_result_.begin();
         }
        
         query_iterator query_end()
         {
            return query_result_.end();
         }

         iterator begin()
         {
            return nodes_.begin();
         }
        
         const_iterator begin() const
         {
            return nodes_.begin();
         }

         iterator end()
         {
            return  nodes_.end();
         }
        
         const_iterator end() const
         {
            return  nodes_.end();
         }
          
         void clear () 
         {
            Envelope<double> ext = root_->extent_;
            nodes_.clear();
            nodes_.push_back(new node(ext));
            root_ = &nodes_[0];
         }

      private:
         void query_node(Envelope<double> const& box, result_t & result, node * node_) const
         {
            if (node_)
            {
               Envelope<double> const& node_extent = node_->extent();
               if (box.intersects(node_extent))
               {
                  node_data_iterator i=node_->begin();
                  node_data_iterator end=node_->end();
                  while ( i!=end)
                  {
                     result.push_back(&(*i));
                     ++i;
                  }
                  for (int k = 0; k < 4; ++k)
                  {
                     query_node(box,result,node_->children_[k]);
                  }
               }
            }
         }
        
         void do_insert_data(T data, Envelope<double> const& box, node * n)
         {
            if (n)
            {
               Envelope<double> const& node_extent = n->extent();
               Envelope<double> ext[4];
               split_box(node_extent,ext);              
               for (int i=0;i<4;++i)
               {
                  if (ext[i].contains(box))
                  {
                     if (!n->children_[i])
                     {
                        nodes_.push_back(new node(ext[i]));
                        n->children_[i]=&nodes_.back();
                     }
                     do_insert_data(data,box,n->children_[i]);
                     return;
                  }
               }
               n->cont_.push_back(data);
            }
         }
        
         void split_box(Envelope<double> const& node_extent,Envelope<double> * ext)
         {
            coord2d c=node_extent.center();

            double width=node_extent.width();
            double height=node_extent.height();
            
            double lox=node_extent.minx();
            double loy=node_extent.miny();
            double hix=node_extent.maxx();
            double hiy=node_extent.maxy();
            
            ext[0]=Envelope<double>(lox,loy,lox + width * ratio_,loy + height * ratio_);
            ext[1]=Envelope<double>(hix - width * ratio_,loy,hix,loy + height * ratio_);
            ext[2]=Envelope<double>(lox,hiy - height*ratio_,lox + width * ratio_,hiy);
            ext[3]=Envelope<double>(hix - width * ratio_,hiy - height*ratio_,hix,hiy);
         }
   };    
} 

#endif

---