Pool.h

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/*
 * Copyright (C) 2006-2010 Jacek Sieka, arnetheduck on gmail point com
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#ifndef ADCHPP_POOL_H
#define ADCHPP_POOL_H

#include "Mutex.h"

namespace adchpp {

template<class T>
struct PoolDummy {
    void operator()(T&) { }
};

template<typename T, class Clear = PoolDummy<T> >
class SimplePool {
public:
    SimplePool() : busy(0) { }
    ~SimplePool() { dcdebug("Busy pool objects: %d\n", (int)busy); }

    T* get() {
        busy++;
        if(!free.empty()) {
            T* tmp = free.back();
            free.pop_back();
            return tmp;
        } else {
            return new T;
        }
    }
    void put(T* item) {
        dcassert(busy > 0);
        busy--;
        Clear()(*item);
        // Remove some objects every now and then...
        if(free.size() > (2*busy) && free.size() > 32) {
            dcdebug("Clearing pool\n");
            while(free.size() > busy / 2) {
                delete free.back();
                free.pop_back();
            }
        }
        free.push_back(item);
    }

private:
    size_t busy;
    std::vector<T*> free;
};


template<class T, class Clear = PoolDummy<T> >
class Pool {
public:
    Pool() { }
    ~Pool() { }

    T* get() {
        FastMutex::Lock l(mtx);
        return pool.get();
    }
    void put(T* obj) {
        FastMutex::Lock l(mtx);
        pool.put(obj);
    }

private:
    Pool(const Pool&);
    Pool& operator=(const Pool&);
    FastMutex mtx;

    SimplePool<T, Clear> pool;
};

}

#endif //POOL_H_