/usr/include/cxxtools/singleton.h is in libcxxtools-dev 2.2.1-2.
This file is owned by root:root, with mode 0o644.
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* Copyright (C) 2005-2006 by Marc Boris Duerner
* Copyright (C) 2006 by Aloysius Indrayanto
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* As a special exception, you may use this file as part of a free
* software library without restriction. Specifically, if other files
* instantiate templates or use macros or inline functions from this
* file, or you compile this file and link it with other files to
* produce an executable, this file does not by itself cause the
* resulting executable to be covered by the GNU General Public
* License. This exception does not however invalidate any other
* reasons why the executable file might be covered by the GNU Library
* General Public License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef cxxtools_Singleton_h
#define cxxtools_Singleton_h
#include <cxxtools/noncopyable.h>
#include <memory>
#include <cstdlib>
namespace cxxtools {
/** @brief Singleton class template
@ingroup cxxtools
@param T Type of the singleton
@param A Allocator for type T
The Singleton class template can be used to easily implement the Singleton
design pattern. It can either be used directly or as a base class. An
allocator can be used to control how the singleton instance will be
allocated.
The follwing example shows how to use the singleton as a base class:
@code
class MySingleton : public Singleton<MySingleton>
{
friend class Singleton<MySingleton>;
// ...
};
@endcode
*/
template <typename T, typename A = std::allocator<T> >
class Singleton : private NonCopyable
{
public:
typedef A Allocator;
public:
/** @brief Returns the instance of the singleton type
When called for the first time, the singleton instance will be
created with the specified alloctaor. All subsequent calls wikk
return a reference to the previously created instance.
@return The singleton instance
*/
static T& instance()
{
if(!_instance)
{
try
{
_instance = (T*)_allocator.allocate(1);
new (_instance) T();
std::atexit(&atExit);
}
catch( const std::bad_alloc& e )
{
throw e;
}
catch(...)
{
_allocator.deallocate(_instance, 1);
_instance = 0;
throw;
}
}
return *_instance;
}
protected:
/** @brief Constructor
*/
Singleton()
{ }
/** @brief Destructor
*/
~Singleton()
{ }
private:
/** @brief Exit handler
This function is set as the program exit handler and will destroy
the singleton instance at the end of the program using the
specified allocator.
*/
static void atExit()
{
_instance->~T();
_allocator.deallocate(_instance, 1);
_instance = 0;
}
private:
static A _allocator;
static T* _instance;
};
template <typename T, typename A>
A Singleton<T, A>::_allocator;
template <typename T, typename A>
T* Singleton<T, A>::_instance = 0;
} // namespace cxxtools
#endif
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