ServiceRegistry.h

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#ifndef art_Framework_Services_Registry_ServiceRegistry_h
#define art_Framework_Services_Registry_ServiceRegistry_h

// ======================================================================
//
// ServiceRegistry - Manages the 'thread specific' instance of Services
//
// ======================================================================

#include "art/Framework/Services/Registry/ServiceScope.h"
#include "art/Framework/Services/Registry/ServiceToken.h"
#include "art/Framework/Services/Registry/ServicesManager.h"
#include "art/Framework/Services/Registry/detail/ServiceHelper.h"
#include "art/Utilities/PluginSuffixes.h"
#include "art/Utilities/ScheduleID.h"
#include "cetlib/LibraryManager.h"
#include "fhiclcpp/ParameterSet.h"

#include <memory>

// ----------------------------------------------------------------------

namespace art {
  class ActivityRegistry;

  class ServiceRegistry {
    // non-copyable:
    ServiceRegistry(ServiceRegistry const&) = delete;
    ServiceRegistry& operator=(ServiceRegistry const&) = delete;

  public:
    class Operate {
      // non-copyable:
      Operate(Operate const&) = delete;
      Operate& operator=(Operate const&) = delete;
      // override operator new to stop use on heap?

    public:
      Operate(ServiceToken const& iToken)
        : oldToken_{ServiceRegistry::instance().setContext(iToken)}
      {}

      ~Operate() { ServiceRegistry::instance().unsetContext(oldToken_); }

    private:
      ServiceToken oldToken_;
    }; // Operate

    friend class Operate;
    template <typename T, art::ServiceScope>
    friend class ServiceHandle;

    template <typename T>
    static bool
    isAvailable()
    {
      if (auto& mgr = instance().manager_) {
        return mgr->isAvailable<T>();
      }

      throw art::Exception(art::errors::ServiceNotFound, "Service")
        << " no ServiceRegistry has been set for this thread";
    }

    using ParameterSets = std::vector<fhicl::ParameterSet>;
    static ServiceToken createSet(ParameterSets const&, ActivityRegistry&);

  private:
    // The token can be passed to another thread in order to have the
    // same services available in the other thread.
    ServiceToken presentToken() const;

    static ServiceRegistry& instance();

    // returns old token
    ServiceToken setContext(ServiceToken const& iNewToken);
    void unsetContext(ServiceToken const& iOldToken);

    template <typename T,
              typename = std::enable_if_t<detail::ServiceHelper<T>::scope_val !=
                                          ServiceScope::PER_SCHEDULE>>
    T&
    get() const
    {
      if (!manager_) {
        throw art::Exception(art::errors::ServiceNotFound, "Service")
          << " no ServiceRegistry has been set for this thread";
      }
      return manager_->get<T>();
    }

    template <typename T,
              typename = std::enable_if_t<detail::ServiceHelper<T>::scope_val ==
                                          ServiceScope::PER_SCHEDULE>>
    T&
    get(ScheduleID sID) const
    {
      if (!manager_) {
        throw art::Exception(art::errors::ServiceNotFound, "Service")
          << " no ServiceRegistry has been set for this thread";
      }
      return manager_->get<T>(sID);
    }

    ServiceRegistry() = default;

    // ---------- member data --------------------------------
    cet::LibraryManager lm_{Suffixes::service()};
    std::shared_ptr<ServicesManager> manager_{nullptr};

  }; // ServiceRegistry

} // art

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

#endif /* art_Framework_Services_Registry_ServiceRegistry_h */

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// mode: c++
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