QxOrm - C++ ORM (Object Relational Mapping) Library

/****************************************************************************
**
** http://www.qxorm.com/
** http://sourceforge.net/projects/qxorm/
** Original file by Lionel Marty
**
** This file is part of the QxOrm library
**
** This software is provided 'as-is', without any express or implied
** warranty. In no event will the authors be held liable for any
** damages arising from the use of this software.
**
** GNU Lesser General Public License Usage
** This file must be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file 'license.lgpl.txt' included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** If you have questions regarding the use of this file, please contact :
** contact@qxorm.com
**
****************************************************************************/

#ifndef _QX_CACHE_H_
#define _QX_CACHE_H_

#ifdef _MSC_VER
#pragma once
#endif

/*!
 * \file QxCache.h
 * \author Lionel Marty
 * \ingroup QxCache
 * \brief qx::cache : based on singleton pattern, provide basic thread-safe cache feature to backup and restore any kind of objects (for example, object fetched from database)
 */

#include <boost/any.hpp>

#include <QxCommon/QxBool.h>

#include <QxCollection/QxCollection.h>

#include <QxSingleton/QxSingleton.h>

namespace qx {
namespace cache {
namespace detail {

class QX_DLL_EXPORT QxCache : public qx::QxSingleton<QxCache>
{

   friend class qx::QxSingleton<QxCache>;

protected:

   typedef std::pair<long, boost::any> type_qx_cache;
   typedef qx::QxCollection<QString, type_qx_cache> type_qx_lst_cache;

   type_qx_lst_cache m_cache;    //!< List of objects in cache under boost::any format
   QMutex m_oMutexCache;         //!< Mutex => 'QxCache' is thread-safe
   long m_lMaxCost;              //!< Max cost before deleting object in cache
   long m_lCurrCost;             //!< Current cost in cache

public:

   QxCache() : qx::QxSingleton<QxCache>("qx::cache::detail::QxCache"), m_lMaxCost(999999999), m_lCurrCost(0) { ; }
   virtual ~QxCache() { ; }

   inline long getCurrCost() const  { return m_lCurrCost; }
   inline long getMaxCost() const   { return m_lMaxCost; }
   inline void setMaxCost(long l)   { QMutexLocker locker(& m_oMutexCache); m_lMaxCost = ((l < 0) ? 0 : l); updateCost(); }

   inline long count() const                          { return m_cache.count(); }
   inline long size() const                           { return this->count(); }
   inline bool isEmpty() const                        { return (this->count() == 0); }
   inline bool exist(const QString & sKey) const      { return m_cache.exist(sKey); }
   inline bool contains(const QString & sKey) const   { return this->exist(sKey); }
   inline boost::any at(const QString & sKey)         { QMutexLocker locker(& m_oMutexCache); return (this->exist(sKey) ? m_cache.getByKey(sKey).second : boost::any()); }
   inline void clear()                                { QMutexLocker locker(& m_oMutexCache); m_cache.clear(); m_lCurrCost = 0; }

   bool insert(const QString & sKey, const boost::any & pObj, long lCost = 1);
   bool remove(const QString & sKey);

private:

   void updateCost();

};

} // namespace detail

/*!
 * \ingroup QxCache
 * \brief Set the maximum allowed total cost of the cache to l. If the current total cost is greater than l, some objects are deleted immediately
 */
inline void max_cost(long l) { qx::cache::detail::QxCache::getSingleton()->setMaxCost(l); }

/*!
 * \ingroup QxCache
 * \brief Return the maximum allowed total cost of the cache
 */
inline long max_cost() { return qx::cache::detail::QxCache::getSingleton()->getMaxCost(); }

/*!
 * \ingroup QxCache
 * \brief Return the current cost used by the cache
 */
inline long current_cost() { return qx::cache::detail::QxCache::getSingleton()->getCurrCost(); }

/*!
 * \ingroup QxCache
 * \brief Return the number of objects in the cache
 */
inline long count() { return qx::cache::detail::QxCache::getSingleton()->count(); }

/*!
 * \ingroup QxCache
 * \brief Return true if the cache contains no object; otherwise return false
 */
inline bool is_empty() { return qx::cache::detail::QxCache::getSingleton()->isEmpty(); }

/*!
 * \ingroup QxCache
 * \brief Delete all the objects in the cache
 */
inline void clear() { qx::cache::detail::QxCache::getSingleton()->clear(); }

/*!
 * \ingroup QxCache
 * \brief Return true if the cache contains an object associated with key sKey; otherwise return false
 */
inline bool exist(const QString & sKey) { return qx::cache::detail::QxCache::getSingleton()->exist(sKey); }

/*!
 * \ingroup QxCache
 * \brief Delete the object associated with key sKey. Return true if the object was found in the cache; otherwise return false
 */
inline bool remove(const QString & sKey) { return qx::cache::detail::QxCache::getSingleton()->remove(sKey); }

/*!
 * \ingroup QxCache
 * \brief Insert object t into the cache with key sKey and associated cost lCost. Any object with the same key already in the cache will be removed
 */
template <typename T>
inline bool set(const QString & sKey, const T & t, long lCost = 1)
{ boost::any obj(t); return qx::cache::detail::QxCache::getSingleton()->insert(sKey, obj, lCost); }

/*!
 * \ingroup QxCache
 * \brief Return the object of type T associated with key sKey, or return default instance of T() if the key does not exist in the cache
 */
template <typename T>
inline T get(const QString & sKey)
{
   boost::any obj = qx::cache::detail::QxCache::getSingleton()->at(sKey);
   if (obj.empty()) { return T(); }
   try { return boost::any_cast<T>(obj); }
   catch (const boost::bad_any_cast & err) { Q_UNUSED(err); return T(); }
}

/*!
 * \ingroup QxCache
 * \brief Return true if object t can be fetched with associated key sKey; otherwise return false with an error description
 */
template <typename T>
inline qx_bool get(const QString & sKey, T & t)
{
   if (! qx::cache::exist(sKey)) { return qx_bool(false, 0, "[QxOrm] Key doesn't exist in cache"); }
   boost::any obj = qx::cache::detail::QxCache::getSingleton()->at(sKey);
   try { t = boost::any_cast<T>(obj); return qx_bool(true); }
   catch (const boost::bad_any_cast & err) { Q_UNUSED(err); return qx_bool(false, 0, "[QxOrm] Bad any cast exception"); }
}

} // namespace cache
} // namespace qx

#endif // _QX_CACHE_H_