mapnik/include/filter.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 FILTER_HPP
#define FILTER_HPP

#include "feature.hpp"

namespace mapnik
{
    template <typename FeatureT> class filter_visitor;
    template <typename FeatureT>
    class MAPNIK_DECL filter
    {
	public:
		virtual bool pass(const FeatureT& feature) const=0; 
		virtual filter<FeatureT>* clone() const=0;
		virtual void accept(filter_visitor<FeatureT>& v) = 0;
        virtual std::string to_string() const=0;
		virtual ~filter() {}
    };
    
    typedef boost::shared_ptr<filter<Feature> > filter_ptr;
    
    template <typename FeatureT>
    class all_filter : public filter<FeatureT>
    {
	public:
		bool pass (const FeatureT&) const
		{
			return true;
		}
	
		filter<FeatureT>* clone() const
		{
			return new all_filter<FeatureT>;
		}
		std::string to_string() const
		{
			return "true";
		}  
        void accept(filter_visitor<FeatureT>&) {}
		virtual ~all_filter() {}
    };
      
    template <typename FeatureT>
    class none_filter : public filter<FeatureT>
    {
	public:
		bool pass (const FeatureT&) const
		{
			return false;
		}
	
		filter<FeatureT>* clone() const
		{
			return new none_filter<FeatureT>;
		}
		std::string to_string() const
		{
			return "false";
		}  
	    void accept(filter_visitor<FeatureT>&) {}
		virtual ~none_filter() {}
	};
}

#endif //FILTER_HPP