TransformCache.h

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
#ifndef ActsGeoUtils_TransformCache_H
#define ActsGeoUtils_TransformCache_H
 
#include <shared_mutex>
#include <type_traits>
#include <ActsGeoUtils/Defs.h>
#include <ActsGeometryInterfaces/IDetectorElement.h>
#include <Identifier/IdentifierHash.h>
#include <CxxUtils/CachedUniquePtr.h>
 
namespace ActsTrk {
  /*** @brief: The TransformCache holds the local -> global transformations associated with a tracking surface 
   *           from the Readout geometry. The cache establishes the connection with the GeometryContext or more
   *           precisely with its DetectorAlignStore to provide the transformations of an aligned surface. 
   *           As soon as the alignment store is accessed, the nominal surface is released from memory.
   *           In order to be used for each detector technology, the virtual <fetchTransform> needs to
   *           be defined further downstream. The method is called everytime when a new cache is invoked. */
  class TransformCacheBase {
      public:
          TransformCacheBase(const IdentifierHash& cacheHash,
                             const DetectorType type);
          TransformCacheBase(const TransformCacheBase& other) noexcept = delete;
          TransformCacheBase& operator=(const TransformCacheBase& other) noexcept = delete;
          TransformCacheBase(TransformCacheBase&& other) noexcept = delete;
          TransformCacheBase& operator=(TransformCacheBase& other) noexcept = delete;
          virtual ~TransformCacheBase();
          IdentifierHash hash() const;
          const Amg::Transform3D& getTransform(const DetectorAlignStore* store) const;
          bool storeTransform(DetectorAlignStore& store) const;
#ifndef SIMULATIONBASE
          const Amg::Transform3D& getTransform(const Acts::GeometryContext& gctx) const;
#endif
          virtual void releaseNominalCache() const;
          DetectorType detectorType() const;
      protected:
          virtual Amg::Transform3D fetchTransform(const DetectorAlignStore* store) const = 0;
      private:
          const IdentifierHash m_hash{0};
          const DetectorType m_type{DetectorType::UnDefined};
          using TicketCounter = detail::TrfStoreTicketCounter;
          const unsigned int m_clientNo{TicketCounter::drawTicket(m_type)};
          mutable CxxUtils::CachedUniquePtrT<Amg::Transform3D> m_nomCache ATLAS_THREAD_SAFE{};
  };
 

  class TransformCache : public TransformCacheBase {
    public:
      using TransformCacheBase::TransformCacheBase;
      virtual Identifier identify() const = 0;
      virtual const IDetectorElement* parent() const = 0;
      virtual void releaseNominalCache() const final;
  };
 
  template<typename CachingDetectorEle> 
  class TransformCacheDetEle: public TransformCache {
    public:
      TransformCacheDetEle(const IdentifierHash& hash, 
                           const CachingDetectorEle* parentEle);
      
      const IDetectorElement* parent() const override final;
      Identifier identify() const override final;
    private:
       Amg::Transform3D fetchTransform(const DetectorAlignStore* store) const override final;
       const CachingDetectorEle* m_parent{nullptr};
  };
 
}
#include <ActsGeoUtils/TransformCache.icc>
#endif