ProductMetaData.h

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#ifndef art_Persistency_Provenance_ProductMetaData_h
#define art_Persistency_Provenance_ProductMetaData_h
// vim: set sw=2:

//==========================================================
//  ProductMetaData
//
//  Singleton facade providing read-only access to the
//  MasterProductRegistry.
//==========================================================

#include "art/Persistency/Provenance/MasterProductRegistry.h"
#include "canvas/Persistency/Provenance/BranchType.h"
#include "canvas/Persistency/Provenance/ProductID.h"
#include "canvas/Persistency/Provenance/ProductList.h"
#include "canvas/Persistency/Provenance/type_aliases.h"
#include "canvas/Utilities/InputTag.h"
#include "cetlib/exempt_ptr.h"

#include <ostream>
#include <vector>

// Used for testing
class MPRGlobalTestFixture;

namespace art {

  class EventProcessor;

  class ProductMetaData {

    friend class EventProcessor;

    // Used for testing.
    friend class ::MPRGlobalTestFixture;

  public:
    // Give access to the only instance; throws if it is not yet made.
    static ProductMetaData const&
    instance()
    {
      if (!me) {
        throw Exception(errors::LogicError) << "ProductMetaData::instance "
                                               "called before the sole "
                                               "instance was created.";
      }
      return *me;
    }

  private:
    // Only friends are permitted to create the instance.
    ProductMetaData(MasterProductRegistry const& mpr) : mpr_{&mpr} {}

    // Only the create_instance() member will create an instance.
    static void
    create_instance(MasterProductRegistry const& mpr)
    {
      if (me) {
        throw Exception(errors::LogicError)
          << "ProductMetaData::create_instance called more than once.";
      }
      me = new ProductMetaData(mpr);
    }

  private:
    // Singleton pattern instance pointer.
    static ProductMetaData const* me;

  public:
    ProductMetaData(ProductMetaData const&) = delete;
    ProductMetaData& operator=(ProductMetaData const&) = delete;

    // Accessors: this is the facade presented by ProductMetaData for
    // the MasterProductRegistry.

    ProductList const&
    productList() const
    {
      return mpr_->productList();
    }

    // Print all the BranchDescriptions we contain.
    void
    printBranchDescriptions(std::ostream& os) const
    {
      mpr_->print(os);
    }

    // Return true if any product is produced in this process for the
    // given branch type.
    bool
    productProduced(BranchType const which) const
    {
      return mpr_->productProduced(which);
    }

    InputTag
    inputTag(art::ProductID const pid) const
    {
      for (auto const& pr : mpr_->productList()) {
        auto const& pd = pr.second;
        if (pd.productID() == pid) {
          return pd.inputTag();
        }
      }
      return art::InputTag{};
    }

  private:
    cet::exempt_ptr<MasterProductRegistry const> mpr_;
  };

  inline std::ostream&
  operator<<(std::ostream& os, ProductMetaData const& pmd)
  {
    pmd.printBranchDescriptions(os);
    return os;
  }

} // namespace art

// Local Variables:
// mode: c++
// End:
#endif /* art_Persistency_Provenance_ProductMetaData_h */