//
// SingletonHolder.h
//
// $Id: //poco/svn/Foundation/include/Poco/SingletonHolder.h#2 $
//
// Library: Foundation
// Package: Core
// Module:  SingletonHolder
//
// Definition of the SingletonHolder template.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_SingletonHolder_INCLUDED
#define Foundation_SingletonHolder_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Mutex.h"


namespace Poco {


template <class S>
class SingletonHolder
	/// This is a helper template class for managing
	/// singleton objects allocated on the heap.
	/// The class ensures proper deletion (including
	/// calling of the destructor) of singleton objects
	/// when the application that created them terminates.
{
public:
	SingletonHolder():
		_pS(0)
		/// Creates the SingletonHolder.
	{
	}
	
	~SingletonHolder()
		/// Destroys the SingletonHolder and the singleton
		/// object that it holds.
	{
		delete _pS;
	}
	
	S* get()
		/// Returns a pointer to the singleton object
		/// hold by the SingletonHolder. The first call
		/// to get will create the singleton.
	{
		FastMutex::ScopedLock lock(_m);
		if (!_pS) _pS = new S;
		return _pS;
	}
	
private:
	S* _pS;
	FastMutex _m;
};


} // namespace Poco


#endif // Foundation_SingletonHolder_INCLUDED