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/*
-----------------------------------------------------------------------
Copyright: 2010-2021, imec Vision Lab, University of Antwerp
2014-2021, CWI, Amsterdam
Contact: astra@astra-toolbox.com
Website: http://www.astra-toolbox.com/
This file is part of the ASTRA Toolbox.
The ASTRA Toolbox is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
The ASTRA Toolbox 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
-----------------------------------------------------------------------
*/
#ifndef _INC_ASTRA_SINGLETON
#define _INC_ASTRA_SINGLETON
#include <cassert>
#ifndef _MSC_VER
#include <stdint.h>
#endif
namespace astra {
/**
* This singleton interface class ensures that any of its children can be instatiated only once. This is used by the ObjectFactories.
**/
template<typename T>
class Singleton {
public:
// constructor
Singleton() { }
// destructor
virtual ~Singleton() {
assert(m_singleton);
m_singleton = 0;
}
static void construct();
// get singleton
static T& getSingleton() {
if (!m_singleton)
construct();
return *m_singleton;
}
static T* getSingletonPtr() {
if (!m_singleton)
construct();
return m_singleton;
}
private:
// the singleton
static T* m_singleton;
};
// We specifically avoid defining construct() in the header.
// That way, the call to new is always executed by code inside libastra.
// This avoids the situation where a singleton gets created by a copy
// of the constructor linked into an object file outside of libastra, such
// as a .mex file, which would then also cause the vtable to be outside of
// libastra. This situation would cause issues when .mex files are unloaded.
#define DEFINE_SINGLETON(T) \
template<> T* Singleton<T >::m_singleton = 0; \
template<> void Singleton<T >::construct() { assert(!m_singleton); m_singleton = new T(); }
// This is a hack to support statements like
// DEFINE_SINGLETON2(CTemplatedClass<C1, C2>);
#define DEFINE_SINGLETON2(A,B) \
template<> A,B* Singleton<A,B >::m_singleton = 0; \
template<> void Singleton<A,B >::construct() { assert(!m_singleton); m_singleton = new A,B(); }
} // end namespace
#endif
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