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

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/*****************************************************************************
 * 
 * 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: pool.hpp 39 2005-04-10 20:39:53Z pavlenko $

#ifndef POOL_HPP
#define POOL_HPP

// stl
#include <iostream>
#include <map>
#include <deque>
#include <ctime>
// boost
#include <boost/shared_ptr.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/utility.hpp>
// mapnik
#include <mapnik/utils.hpp>

namespace mapnik
{
    template <typename T, typename PoolT>
    class PoolGuard
    {
    private:
        const T& obj_;
        PoolT& pool_; 
    public:
        explicit PoolGuard(const T& ptr,PoolT& pool)
            : obj_(ptr),
              pool_(pool) {}

        ~PoolGuard() 
        {
            pool_->returnObject(obj_);
        }

    private:
        PoolGuard();
        PoolGuard(const PoolGuard&);
        PoolGuard& operator=(const PoolGuard&);
    };

    template <typename T,template <typename> class Creator>
    class Pool : private boost::noncopyable
    {
        typedef boost::shared_ptr<T> HolderType;
        typedef std::deque<HolderType> ContType;        
        
        Creator<T> creator_;
        const unsigned initialSize_; 
        const unsigned maxSize_;
        ContType usedPool_;
        ContType unusedPool_;
        boost::mutex mutex_;
    public:

        Pool(const Creator<T>& creator,unsigned initialSize=1, unsigned maxSize=10)
            :creator_(creator),
             initialSize_(initialSize),
             maxSize_(maxSize)
        {
            for (unsigned i=0; i < initialSize_; ++i) 
            {
                HolderType conn(creator_());
                if (conn->isOK())
                    unusedPool_.push_back(conn);
            }
        }

        HolderType borrowObject()
        {           
            mutex::scoped_lock lock(mutex_);
            typename ContType::iterator itr=unusedPool_.begin();
            if (itr!=unusedPool_.end())
            { 
#ifdef MAPNIK_DEBUG
                std::clog<<"borrow "<<(*itr).get()<<"\n";
#endif
                usedPool_.push_back(*itr);
                itr=unusedPool_.erase(itr);
                return usedPool_[usedPool_.size()-1];
            }
            else if (unusedPool_.size() < maxSize_)
            {
                HolderType conn(creator_());
                if (conn->isOK())
                {
                    usedPool_.push_back(conn);
#ifdef MAPNIK_DEBUG
                std::clog << "create << " << conn.get() << "\n";
#endif
                return conn;
                }
            }
            return HolderType();
        } 

        void returnObject(HolderType obj)
        {
            mutex::scoped_lock lock(mutex_);
            typename ContType::iterator itr=usedPool_.begin();
            while (itr != usedPool_.end())
            {
                if (obj.get()==(*itr).get()) 
                {
#ifdef MAPNIK_DEBUG
                    std::clog<<"return "<<(*itr).get()<<"\n";
#endif
                    unusedPool_.push_back(*itr);
                    usedPool_.erase(itr);
                    return;
                }
                ++itr;
            }
        }
    };
}
#endif //POOL_HPP

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