mapnik/include/mapnik/quad_tree.hpp

/*****************************************************************************
 * 
 * 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
// mapnik
#include <mapnik/box2d.hpp>
// boost
#include <boost/ptr_container/ptr_vector.hpp>
#include <boost/noncopyable.hpp>
// stl
#include <vector>
#include <cstring>

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;
        box2d<double> extent_;
        cont_t cont_;
        node * children_[4];

        explicit node(box2d<double> const& ext)
            : extent_(ext)
        {
            std::memset(children_,0,4*sizeof(node*));
        }
   
        box2d<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 unsigned int max_depth_;
    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(box2d<double> const& ext, 
                       unsigned int max_depth = 8, 
                       double ratio = 0.55) 
        : max_depth_(max_depth),
          ratio_(ratio)
    {
        nodes_.push_back(new node(ext));
        root_ = &nodes_[0];
    }
                
    void insert(T data, box2d<double> const& box)
    {
        unsigned int depth=0;
        do_insert_data(data,box,root_,depth);
    }
         
    query_iterator query_in_box(box2d<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 () 
    {
        box2d<double> ext = root_->extent_;
        nodes_.clear();
        nodes_.push_back(new node(ext));
        root_ = &nodes_[0];
    }

private:
    void query_node(box2d<double> const& box, result_t & result, node * node_) const
    {
        if (node_)
        {
            box2d<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, box2d<double> const& box, node * n, unsigned int& depth)
    {
        if (++depth >= max_depth_)
        {
            n->cont_.push_back(data);
        }
        else 
        {
            box2d<double> const& node_extent = n->extent();
            box2d<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],depth);
                    return;
                }
            }
            n->cont_.push_back(data);
        }
    }
        
    void split_box(box2d<double> const& node_extent,box2d<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]=box2d<double>(lox,loy,lox + width * ratio_,loy + height * ratio_);
        ext[1]=box2d<double>(hix - width * ratio_,loy,hix,loy + height * ratio_);
        ext[2]=box2d<double>(lox,hiy - height*ratio_,lox + width * ratio_,hiy);
        ext[3]=box2d<double>(hix - width * ratio_,hiy - height*ratio_,hix,hiy);
    }
};    
} 

#endif