ATLIDTRKCP-532: In det measurement pool converter for ACTS space points

This is to address ATLIDTRKCP-532

Idea is to attach decorators to the space points when writing/reading from files.

• while writing, we take the vector of bare pointes (in the measurement dynamic variable) and we create Element links
• while reading, we take the vector of element link and we attach bare pointers

Event/xAOD/xAODInDetMeasurementAthenaPool/src/xAODSpacePointAuxContainerCnv.cxx

+/*
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
+*/
+
+// Local include(s):
+#include "xAODSpacePointAuxContainerCnv.h"
+
+// EDM include(s):
+#include "xAODInDetMeasurement/SpacePointContainer.h"
+#include "xAODMeasurementBase/UncalibratedMeasurementContainer.h"
+
+// Other includes
+#include "AthLinks/ElementLink.h"
+
+xAODSpacePointAuxContainerCnv::xAODSpacePointAuxContainerCnv( ISvcLocator* svcLoc )
+  : xAODSpacePointAuxContainerCnvBase( svcLoc )
+{}
+
+StatusCode xAODSpacePointAuxContainerCnv::initialize()
+{
+  ATH_MSG_DEBUG("Initializing xAODSpacePointAuxContainerCnv ...");
+  return xAODSpacePointAuxContainerCnvBase::initialize();
+}
+
+xAOD::SpacePointAuxContainer* xAODSpacePointAuxContainerCnv::createPersistentWithKey( xAOD::SpacePointAuxContainer* trans,
+										      const std::string& key )
+{
+  ATH_MSG_DEBUG("Calling xAODSpacePointAuxContainerCnv::createPersistentWithKey for our xAOD space points");
+  
+  // Load the necessary ROOT class(es):
+  static char const* const NAME =
+    "std::vector<std::vector<ElementLink<xAOD::UncalibratedMeasurementContainer> > >";
+  static TClass const* const cls = TClass::GetClass( NAME );
+  if( ! cls ) {
+    ATH_MSG_ERROR( "Couldn't load dictionary for type: " << NAME );
+  }
+  
+  // This makes a copy of the container, with any thinning applied.
+  std::unique_ptr< xAOD::SpacePointAuxContainer > result 
+    ( xAODSpacePointAuxContainerCnvBase::createPersistentWithKey (trans, key) );
+  
+  // see if we can get the variable from trans
+  using measurement_collection_t = std::vector< const xAOD::UncalibratedMeasurement* >;
+  auto measurementAuxId = SG::AuxTypeRegistry::instance().getAuxID< measurement_collection_t >("measurements");
+
+  // Create a helper object for the Element Links
+  xAOD::SpacePointContainer helper;
+  for (std::size_t i(0); i<result->size(); ++i) {
+    helper.push_back( std::make_unique< xAOD::SpacePoint >() );
+  }
+  helper.setStore( result.get() );
+
+  // Convert the bare pointer(s) to Element Link(s)
+  static const SG::AuxElement::Accessor< std::vector<ElementLink<xAOD::UncalibratedMeasurementContainer>> > accesor("measurementLink"); 
+
+  for (xAOD::SpacePoint *sp : helper) {
+    std::vector< ElementLink<xAOD::UncalibratedMeasurementContainer> > els;
+    accesor(*sp) = els;
+
+    // get values from the trans aux container directly
+    const void* ptrToSomething = trans->getData (measurementAuxId);
+    const measurement_collection_t& measurements = static_cast<const measurement_collection_t*>(ptrToSomething)[sp->index()];
+    accesor(*sp).reserve( measurements.size() );
+    for (std::size_t idx(0); idx<measurements.size(); ++idx) {
+      accesor(*sp).push_back( ElementLink< xAOD::UncalibratedMeasurementContainer >(*dynamic_cast<const xAOD::UncalibratedMeasurementContainer*>(measurements[idx]->container()), measurements[idx]->index()) );
+    }    
+  }
+  
+  return result.release();
+}