OutputHandle.h

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#ifndef art_Framework_Principal_OutputHandle_h
#define art_Framework_Principal_OutputHandle_h
// vim: set sw=2 expandtab :

// Handle: Non-owning "smart pointer" for reference to EDProducts and
// their Provenances.
//
// This is a very preliminary version, and lacks safety features and
// elegance.
//
// If the pointed-to object or provenance destroyed, use of the
// Handle becomes undefined. There is no way to query the Handle to
// discover if this has happened.
//
// Handles can have:
//   -- Product and Provenance pointers both null;
//   -- Both pointers valid
//
// To check validity, one can use the isValid() function.
//
// If failedToGet() returns true then the requested data is not available
// If failedToGet() returns false but isValid() is also false then no attempt
//   to get data has occurred

#include "canvas/Persistency/Provenance/ProductProvenance.h"
#include "canvas/Persistency/Provenance/RangeSet.h"
#include "canvas/Persistency/Provenance/fwd.h"
#include "cetlib/exempt_ptr.h"

namespace art {

  class EDProduct;

  class OutputHandle {
  public:
    ~OutputHandle();

    OutputHandle(EDProduct const*,
                 BranchDescription const*,
                 cet::exempt_ptr<ProductProvenance const>,
                 RangeSet const&);

    static OutputHandle
    invalid()
    {
      return OutputHandle{RangeSet::invalid()};
    }

    OutputHandle(RangeSet const&);

    OutputHandle(OutputHandle const&) = delete;
    OutputHandle(OutputHandle&&) = default;

    OutputHandle& operator=(OutputHandle const&) = delete;
    OutputHandle& operator=(OutputHandle&&) = delete;

    bool isValid() const;
    BranchDescription const* desc() const;
    ProductProvenance const* productProvenance() const;
    EDProduct const* wrapper() const;
    RangeSet const& rangeOfValidity() const;

    void swap(OutputHandle&);

  private:
    BranchDescription const* desc_{nullptr};
    cet::exempt_ptr<ProductProvenance const> productProvenance_{nullptr};
    EDProduct const* wrap_{nullptr};
    RangeSet const& rangeOfValidity_;
  };

  void swap(OutputHandle&, OutputHandle&);

} // namespace art

#endif /* art_Framework_Principal_OutputHandle_h */

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