//-----------------------------------------------------------------------------
// Copyright(c), HL Rally: Source, 2004, All rights reserved.
// The contents of this file may only be used / distributed in accordance
// with the conditions listed in the supplied license, or with written
// permission of the respective authors listed.
//-----------------------------------------------------------------------------

#ifndef SINGLETON_H
#define SINGLETON_H


/**
 * Template class to create singleton classes
 *
 * Singleton has been implemented by only allowing one static instance of
 * the class at any one time.
 *
 * By making the implementing class constructor and destructor private, and 
 * giving friend access only to CSingletonABC, the class's usage may be 
 * restricted to only the one static instance.
 *
 * ========================================================================
 * Example / Usage:
 *
 * class CMyClass : public CSingletonABC <CMyClass>
 * {
 * 	public:
 * 		void RandomMethod();
 * 		...
 *
 * 	private:
 *
 * 		// Enforce singleton by making accessable only by CSingleton
 * 		CMyClass();
 * 		virtual ~CMyClass();
 *
 * 		friend class CSingletonABC;
 * 		
 * 		...
 * }
 *
 */
template <typename T> class CSingletonABC
{
public:

	/**
	 * Constructor
	 */
	CSingletonABC()
	{
	}

	/**
	 * Destructor
	 */
	virtual ~CSingletonABC()
	{
	}

	/**
	 * Creates the static singleton instance of T
	 */
	static T* CreateInstance()
	{
		if(!ms_pSingleton)
			ms_pSingleton = new T();

		return ms_pSingleton;
	}

	/**
	 * Returns a pointer to the static instance
	 */
	static T* GetInstance()
	{
		assert(ms_pInstance);
		return ms_pInstance;
	}

	/**
	 * Frees the static singleton instance of T
	 */
	static void FreeInstance()
	{
		if(ms_pInstance)
		{
			delete (T *)ms_pInstance;
			ms_pInstance = NULL;
		}
	}

protected:

	// Static singleton instance of T
	static T* ms_pInstance;
};

#endif