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; }
  ~implements() override = default;

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_ */