CPCSentry.h

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#ifndef art_Framework_Core_CPCSentry_h
#define art_Framework_Core_CPCSentry_h

#include "cetlib/exempt_ptr.h"

// ======================================================================
//
// class CPCSentry uses RAII to make sure that the
// CurrentProcessingContext pointer it is guarding is set to the right
// value, and cleared at the right time.
//
// ======================================================================

namespace art {

  class CurrentProcessingContext;

  namespace detail {

    class CPCSentry {
    public:
      CPCSentry(cet::exempt_ptr<CurrentProcessingContext const>& c,
                cet::exempt_ptr<CurrentProcessingContext const> value)
        : referenced_{&c}
      {
        c = value;
      }

      ~CPCSentry() noexcept { *referenced_ = nullptr; }

    private:
      cet::exempt_ptr<CurrentProcessingContext const>* referenced_;
    }; // CPCSentry

  } // detail
} // art

  // ======================================================================

#endif /* art_Framework_Core_CPCSentry_h */

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