singleton template 싱글턴 템플릿

/* Copyright (C) Scott Bilas, 2000.
* All rights reserved worldwide.
*
* This software is provided "as is" without express or implied
* warranties. You may freely copy and compile this source into
* applications you distribute provided that the copyright text
* below is included in the resulting source code, for example:
* "Portions Copyright (C) Scott Bilas, 2000"
*/

#include <cassert>
template <typename T> class Singleton
{
static T* ms_Singleton;
public:
Singleton( void )
{
assert( !ms_Singleton );
int offset = (int)(T*)1 - (int)(Singleton <T>*)(T*)1;
ms_Singleton = (T*)((int)this + offset);
}
~Singleton( void )
{
 assert( ms_Singleton ); ms_Singleton = 0; }
static T& GetSingleton( void )
{ assert( ms_Singleton ); return ( *ms_Singleton ); }
static T* GetSingletonPtr( void )
{ return ( ms_Singleton ); }
};
template <typename T> T* Singleton <T>::ms_Singleton = 0; 

// Sample usage:
//
class TextureMgr : public Singleton <TextureMgr>
public:
Texture* GetTexture( const char* name );
// ...
};

#define g_TextureMgr TextureMgr::GetSingleton()

void SomeFunction( void )
{
Texture* stone1 = TextureMgr::GetSingleton().GetTexture( "stone1" );
Texture* wood6 = g_TextureMgr.GetTexture( "wood6" );
// ...
}

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