implements.h

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#ifndef GAUDIKERNEL_IMPLEMENTS_H
#define GAUDIKERNEL_IMPLEMENTS_H

#include "GaudiKernel/IInterface.h"
#include <atomic>

template <typename... Interfaces>
struct GAUDI_API implements : virtual public extend_interfaces<Interfaces...> {
  using base_class = implements<Interfaces...>;
  using extend_interfaces_base = extend_interfaces<Interfaces...>;
  using iids                   = typename extend_interfaces_base::ext_iids;

public:
  void* i_cast( const InterfaceID& tid ) const override { return Gaudi::iid_cast( tid, iids{}, this ); }
  StatusCode queryInterface( const InterfaceID& ti, void** pp ) override
  {
    if ( !pp ) return StatusCode::FAILURE;
    *pp = Gaudi::iid_cast( ti, iids{}, this );
    if ( !*pp ) return StatusCode::FAILURE; /* cast failed */
    this->addRef();
    return StatusCode::SUCCESS;
  }
  std::vector<std::string> getInterfaceNames() const override { return Gaudi::getInterfaceNames( iids{} ); }
  implements() = default;
  implements( const implements& /*other*/ ) : m_refCount{0} {}
  implements& operator=( const implements& /*other*/ ) { return *this; }

public:
  unsigned long addRef() override { return ++m_refCount; }
  unsigned long release() override
  {
    /* Avoid to decrement 0 */
    auto count = ( m_refCount ? --m_refCount : m_refCount.load() );
    if ( count == 0 ) delete this;
    return count;
  }
  unsigned long refCount() const override { return m_refCount.load(); }

protected:
  std::atomic_ulong m_refCount = {0};
};

template <typename I1>
using implements1 = implements<I1>;
template <typename I1, typename I2>
using implements2 = implements<I1, I2>;
template <typename I1, typename I2, typename I3>
using implements3 = implements<I1, I2, I3>;
template <typename I1, typename I2, typename I3, typename I4>
using implements4 = implements<I1, I2, I3, I4>;

#endif /* GAUDIKERNEL_IMPLEMENTS_H_ */