127 lines
2.6 KiB
C++
127 lines
2.6 KiB
C++
//This file is part of Photon (http://photon.sourceforge.net)
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//Copyright (C) 2004-2005 James Turk
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//
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// Author:
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// James Turk (jpt2433@rit.edu)
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//
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// Version:
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// $Id: Singleton.hpp,v 1.5 2005/03/03 09:25:20 cozman Exp $
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#ifndef PHOTON_UTIL_SINGLETON_HPP
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#define PHOTON_UTIL_SINGLETON_HPP
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#include <memory>
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#include <boost/utility.hpp>
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#include "exceptions.hpp"
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namespace photon
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{
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namespace util
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{
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// Class: Singleton
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// Template class for singleton pattern. Is non-copyable to enforce
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// correct behavior.
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//
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// Defining a Singleton:
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// (code)
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// YourClass : public Singleton<Class>
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// {
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// // class specific data
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//
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// // Singleton-required code
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// private:
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// // Singleton-required code
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// YourClass();
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// ~YourClass();
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//
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// friend class util::Singleton<YourClass>;
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// friend class std::auto_ptr<YourClass>;
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// };
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// (end)
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//
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// Using The Singleton:
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// (code)
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// YourClass::initialize();
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// YourClass& yc(YourClass::getInstance());
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//
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// // use yc
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//
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// YourClass::destroy(); //optional
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// (end)
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template<class T>
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class Singleton : public boost::noncopyable
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{
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public:
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// Function: initialize
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// Initialize the instance of the singleton, must be done explicitly.
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static void initialize();
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// Function: destroy
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// Destroy the instance of the singleton, can be done explicitly if order
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// of destruction matters. Will be done automatically if not done.
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static void destroy();
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// Function: getInstance
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// Get a reference to the instance of the derived class.
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static T& getInstance();
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protected:
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virtual ~Singleton()=0; // allow inheritance
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private:
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static std::auto_ptr<T> instance_;
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};
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// template implementation
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template<class T>
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Singleton<T>::~Singleton()
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{
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}
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template<class T>
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void Singleton<T>::initialize()
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{
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if(instance_.get() != 0)
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{
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throw PreconditionException("Attempt to double-initialize singleton.");
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}
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instance_ = std::auto_ptr<T>(new T);
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}
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template<class T>
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void Singleton<T>::destroy()
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{
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if(instance_.get() == 0)
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{
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throw PreconditionException("Attempt to destroy null singleton.");
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}
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instance_.reset();
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}
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template<class T>
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T& Singleton<T>::getInstance()
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{
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if(instance_.get() == 0)
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{
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throw PreconditionException("Attempt to get instance of uninitialized "
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"singleton.");
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}
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return *instance_; //return dereferenced version
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}
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template<class T>
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std::auto_ptr<T> Singleton<T>::instance_(0);
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}
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}
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#endif //PHOTON_UTIL_SINGLETON_HPP
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