ObjectPool.hpp

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/* 
 * ObjectPool.hpp 
 *
 * This file is part of the Chemical Data Processing Toolkit
 *
 * Copyright (C) 2003 Thomas Seidel <thomas.seidel@univie.ac.at>
 *
 * 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 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; see the file COPYING. If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
 
#ifndef CDPL_UTIL_OBJECTPOOL_HPP
#define CDPL_UTIL_OBJECTPOOL_HPP
 
#include <vector>
#include <cstddef>
#include <algorithm>
#include <new>
#include <memory>
#include <functional>
 
 
namespace CDPL
{
 
    namespace Util
    {
 
        template <typename T>
        class ObjectPool
        {
 
          public:
            typedef T ObjectType;
 
            typedef std::shared_ptr<ObjectType> SharedObjectPointer;
 
            typedef std::function<ObjectType*()>     ConstructorFunction;
            typedef std::function<void(ObjectType*)> DestructorFunction;
            typedef std::function<void(ObjectType&)> ObjectFunction;
 
            struct DefaultConstructor
            {
 
                T* operator()() const
                {
                    return new T();
                }
            };
 
            struct DefaultDestructor
            {
 
                void operator()(T* obj) const
                {
                    delete obj;
                }
            };
 
            ObjectPool(const ObjectPool& pool):
                maxSize(pool.maxSize), ctorFunc(pool.ctorFunc), dtorFunc(pool.dtorFunc),
                initFunc(pool.initFunc), cleanFunc(pool.cleanFunc) {}
 
            ObjectPool(std::size_t max_size = 0):
                maxSize(max_size), ctorFunc(DefaultConstructor()), dtorFunc(DefaultDestructor()) {}
 
            template <typename C, typename D>
            ObjectPool(const C& ctor_func, const D& dtor_func, std::size_t max_size = 0):
                maxSize(max_size), ctorFunc(ctor_func), dtorFunc(dtor_func)
            {}
 
            ~ObjectPool()
            {
                std::for_each(pool.begin(), pool.end(), dtorFunc);
            }
 
            SharedObjectPointer get()
            {
                ObjectType* obj;
 
                if (!pool.empty()) {
                    obj = pool.back();
                    pool.pop_back();
 
                } else {
                    obj = ctorFunc();
 
                    if (!obj)
                        throw std::bad_alloc();
                }
 
                SharedObjectPointer obj_ptr(obj, PutObject(*this));
 
                if (initFunc)
                    initFunc(*obj);
 
                return obj_ptr;
            }
 
            std::size_t getSize() const
            {
                return pool.size();
            }
 
            std::size_t getMaxSize() const
            {
                return maxSize;
            }
 
            void setMaxSize(std::size_t max_size)
            {
                maxSize = max_size;
 
                shrinkToMaxSize();
            }
 
            void freeMemory()
            {
                std::for_each(pool.begin(), pool.end(), dtorFunc);
 
                pool.clear();
            }
 
            void setInitFunction(const ObjectFunction& func)
            {
                initFunc = func;
            }
 
            void setCleanupFunction(const ObjectFunction& func)
            {
                cleanFunc = func;
            }
 
            ObjectPool& operator=(const ObjectPool& pool)
            {
                if (this == &pool)
                    return *this;
 
                maxSize  = pool.maxSize;
                ctorFunc = pool.ctorFunc;
                dtorFunc = pool.dtorFunc;
                initFunc = pool.initFunc;
 
                shrinkToMaxSize();
 
                return *this;
            }
 
          private:
            void shrinkToMaxSize()
            {
                if (maxSize == 0)
                    return;
 
                while (pool.size() > maxSize) {
                    dtorFunc(pool.back());
                    pool.pop_back();
                }
            }
 
            struct PutObject
            {
 
                PutObject(ObjectPool& pool):
                    pool(pool) {}
 
                void operator()(ObjectType* obj) const
                {
                    pool.put(obj);
                }
 
                ObjectPool& pool;
            };
 
            void put(ObjectType* obj)
            {
                if (maxSize > 0 && pool.size() >= maxSize) {
                    dtorFunc(obj);
                    return;
                }
 
                try {
                    if (cleanFunc)
                        cleanFunc(*obj);
 
                    pool.push_back(obj);
 
                } catch (...) {
                    dtorFunc(obj);
                }
            }
 
            typedef std::vector<ObjectType*> PooledObjectList;
 
            std::size_t         maxSize;
            PooledObjectList    pool;
            ConstructorFunction ctorFunc;
            DestructorFunction  dtorFunc;
            ObjectFunction      initFunc;
            ObjectFunction      cleanFunc;
        };
    } // namespace Util
} // namespace CDPL
 
#endif // CDPL_UTIL_OBJECTPOOL_HPP