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192 lines
4.5 KiB
C++
192 lines
4.5 KiB
C++
// NeL - MMORPG Framework <http://dev.ryzom.com/projects/nel/>
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// Copyright (C) 2010 Winch Gate Property Limited
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as
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// published by the Free Software Foundation, either version 3 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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#ifndef NL_SINGLETON_H
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#define NL_SINGLETON_H
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#include "nel/misc/common.h"
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#include "nel/misc/debug.h"
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#include "nel/misc/thread.h"
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#include "nel/misc/app_context.h"
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namespace NLMISC
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{
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/**
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* Example:
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* \code
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struct CFooSingleton : public CSingleton<CFooSingleton>
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{
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void foo() { nlinfo("foo!"); }
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};
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// call the foo function:
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CFooSingleton::getInstance().foo();
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* \endcode
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* \author Vianney Lecroart
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* \author Nevrax France
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* \date 2004
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*/
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template<class T>
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class CSingleton
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{
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public:
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virtual ~CSingleton() {}
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/// returns a reference and not a pointer to be sure that the user
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/// doesn't have to test the return value and can directly access the class
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static T &getInstance()
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{
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if(!Instance)
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{
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Instance = new T;
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nlassert(Instance);
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}
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return *Instance;
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}
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/// shorter version of getInstance()
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static T &instance() { return getInstance(); }
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static void releaseInstance()
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{
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if(Instance)
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{
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delete Instance;
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Instance = NULL;
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}
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}
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protected:
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/// no public ctor to be sure that the user can't create an instance
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CSingleton()
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{
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}
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static T *Instance;
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};
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template <class T>
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T* CSingleton<T>::Instance = 0;
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/** A variant of the singleton, not fully compliant with the standard design pattern
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* It is more appropriate for object built from a factory but that must
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* be instanciate only once.
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* The singleton paradigm allow easy access to the unique instance but
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* I removed the automatic instanciation of getInstance().
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*
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* Consequently, the getInstance return a pointer that can be NULL
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* if the singleton has not been build yet.
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*
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* Example:
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* \code
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struct CFooSingleton : public CManualSingleton<CFooSingleton>
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{
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void foo() { nlinfo("foo!"); }
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};
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// create an instance by any mean
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CFooSingleton mySingleton
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// call the foo function:
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CFooSingleton::getInstance()->foo();
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// create another instance is forbiden
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CFooSingleton otherInstance; // ASSERT !
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* \endcode
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* \author Boris 'sonix' Boucher
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* \author Nevrax France
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* \date 2005
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*/
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template <class T>
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class CManualSingleton
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{
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static T *&_instance()
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{
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static T *instance = NULL;
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return instance;
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}
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protected:
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CManualSingleton()
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{
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nlassert(_instance() == NULL);
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_instance() = static_cast<T*>(this);
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}
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~CManualSingleton()
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{
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nlassert(_instance() == this);
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_instance() = NULL;
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}
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public:
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static bool isInitialized()
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{
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return _instance() != NULL;
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}
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static T* getInstance()
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{
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nlassert(_instance() != NULL);
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return _instance();
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}
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};
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/** A macro for safe global variable value.
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* Concept : global initialized variable value are inherently unsafe because the order of
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* initialisation if undefined. If some init code use static value, you
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* may encounter hazardous error, depending on you compiler will, when you
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* read the value of a global, you may read it before it is initialized.
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* This little class is a workaround that allow a safe global value.
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* A drawback is that the value is enclosed inside a function and thus not
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* accessible in the debugger.
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* use getGlobal_<name>() to retrieve a reference to the value.
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*/
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#define NL_MISC_SAFE_GLOBAL(type, name, value) \
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type &getGlobal_##name() \
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{ \
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static type theVar = (value); \
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return theVar; \
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} \
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#define NL_MISC_SAFE_CLASS_GLOBAL(type, name, value) \
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static type &getGlobal_##name() \
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{ \
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static type theVar = (value); \
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return theVar; \
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} \
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} // NLMISC
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#endif // NL_SINGLETON_H
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/* End of singleton.h */
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