singleton.inl

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/** @file
 *  @author Bram de Greve (bram@cocamware.com)
 *  @author Tom De Muer (tom@cocamware.com)
 *
 *  *** BEGIN LICENSE INFORMATION ***
 *  
 *  The contents of this file are subject to the Common Public Attribution License 
 *  Version 1.0 (the "License"); you may not use this file except in compliance with 
 *  the License. You may obtain a copy of the License at 
 *  http://lass.sourceforge.net/cpal-license. The License is based on the 
 *  Mozilla Public License Version 1.1 but Sections 14 and 15 have been added to cover 
 *  use of software over a computer network and provide for limited attribution for 
 *  the Original Developer. In addition, Exhibit A has been modified to be consistent 
 *  with Exhibit B.
 *  
 *  Software distributed under the License is distributed on an "AS IS" basis, WITHOUT 
 *  WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 *  language governing rights and limitations under the License.
 *  
 *  The Original Code is LASS - Library of Assembled Shared Sources.
 *  
 *  The Initial Developer of the Original Code is Bram de Greve and Tom De Muer.
 *  The Original Developer is the Initial Developer.
 *  
 *  All portions of the code written by the Initial Developer are:
 *  Copyright (C) 2004-2024 the Initial Developer.
 *  All Rights Reserved.
 *  
 *  Contributor(s):
 *
 *  Alternatively, the contents of this file may be used under the terms of the 
 *  GNU General Public License Version 2 or later (the GPL), in which case the 
 *  provisions of GPL are applicable instead of those above.  If you wish to allow use
 *  of your version of this file only under the terms of the GPL and not to allow 
 *  others to use your version of this file under the CPAL, indicate your decision by 
 *  deleting the provisions above and replace them with the notice and other 
 *  provisions required by the GPL License. If you do not delete the provisions above,
 *  a recipient may use your version of this file under either the CPAL or the GPL.
 *  
 *  *** END LICENSE INFORMATION ***
 */
 
 
 
#ifndef LASS_GUARDIAN_OF_INCLUSION_UTIL_SINGLETON_INL
#define LASS_GUARDIAN_OF_INCLUSION_UTIL_SINGLETON_INL
 
 
#include "singleton.h"
#include "thread.h"
#include <atomic>
 
namespace lass
{
namespace util
{
 
 
template <class T, int DP>
Singleton<T, DP>::Singleton():
    impl::SingletonBase(),
    instance_(new TInstance)
{
}
 
 
 
template <class T, int DP>
Singleton<T, DP>::~Singleton()
{
    deadReference(true);
}
 
 
 
/** Return pointer to singleton instance.
 *  An instance is created on first call.
 *  Return NULL if instance is dead already (after first destruction of singletons).
 *  @note this should be thread safe over all singletons.
 */
template <class T, int DP>
typename Singleton<T, DP>::TInstance* Singleton<T, DP>::instance()
{
    static std::atomic<TSelf*> neo{ nullptr };
    static std::atomic<int> semaphore{ 1 };
 
    if (deadReference(false))
    {
        std::cerr << "[LASS RUN MSG] Dead reference detected at '" << neo.load(std::memory_order_relaxed) 
            << "' of singleton '" << typeid(TInstance).name() << "' with destruction priority '"
            << destructionPriority << "'" << std::endl;
        return nullptr;
    }
 
    TSelf* one = neo.load(std::memory_order_acquire);
    if (!one)
    {
        LASS_LOCK_INTEGRAL(semaphore)
        {
            one = neo.load(std::memory_order_relaxed);
            if (!one)
            {
                one = new TSelf;
                one->subscribeInstance(destructionPriority);
                neo.store(one, std::memory_order_release);
            }
        }
    }
    LASS_ASSERT(one);
#if LASS_COMPILER_TYPE == LASS_COMPILER_TYPE_MSVC
#   pragma warning(suppress: 6011) // Dereferencing NULL pointer 'one'
#endif
    return one->instance_.get();
}
 
 
 
/** return true if singleton is destructed.
 *  @param iSetReferenceToDead - call this method with true on destruction of singleton
 *                              - call this method with false to check it.
 */
template <class T, int DP>
bool Singleton<T, DP>::deadReference(bool setReferenceToDead)
{
    static std::atomic<int> dead{ false };
    if (setReferenceToDead)
    {
        dead.store(true, std::memory_order_release);
        return true;
    }
    else
    {
        return dead.load(std::memory_order_acquire);
    }
}
 
 
}
}
 
#endif