ViewVectorBase.icc

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
/**
 * @file ViewVectorBase.icc
 * @author scott snyder <snyder@bnl.gov>
 * @date Sep, 2016
 * @brief Hold the persistent representation for a ViewVector.
 */
 
 
#include "AthContainers/AuxElement.h"
#include "AthContainers/CurrentContext.h"
#include "CxxUtils/checker_macros.h"
#include <type_traits>
 
 
namespace {
 
 
template <class T>
inline
SG::AuxVectorData* getContainer1 (T* p, const std::true_type&)
{
  return p->container();
}
template <class T>
inline
SG::AuxVectorData* getContainer1 (T*, const std::false_type&)
{
  return nullptr;
}
 
 
/**
 * @brief Return the container for an element.
 *
 * Returns null if the element does not derive from AuxElement.
 */
template <class T>
inline
SG::AuxVectorData* getContainer (T* p)
{
  return getContainer1 (p, typename std::is_base_of<SG::AuxElement, T>::type());
}
 
 
} // anonymous namespace
 
 
namespace SG {
 
 
/**
 * @brief Clear the persistent data.
 */
inline
void ViewVectorBase::clearPersistent()
{
  m_persKey.clear();
  m_persIndex.clear();
}
 
 
/**
 * @brief Set a flag to declare that the vector should be cleared
 *        on the next call to toPersistent().
 *
 *        This would be used in the case where we make a copy of the
 *        object being written.
 */
inline
void ViewVectorBase::setClearOnPersistent()
{
  m_clearOnPersistent = true;
}
 
 
/**
 * @brief Convert to persistent form.
 * @param v The vector to convert.
 *
 * Called for classes that have a CLID.
 */
template <class DV>
void
ViewVectorBase::doToPersistent1 (DV& v, const std::true_type&)
{
  std::vector<ElementLink<DV> > elv = SG::dataVectorAsELV (v, Gaudi::Hive::currentContext());
  m_persKey.clear();
  m_persIndex.clear();
  m_persKey.reserve (elv.size());
  m_persIndex.reserve (elv.size());
  for (ElementLinkBase& el : elv) {
#ifdef XAOD_STANDALONE
    m_persKey.push_back (el.persKey());
    m_persIndex.push_back (el.persIndex());
#else
    el.thin();
    m_persKey.push_back (el.key());
    m_persIndex.push_back (el.index());
#endif
  }
  if (m_clearOnPersistent) {
    v.clear();
    m_clearOnPersistent = false;
  }
}
 
 
/**
 * @brief Convert to persistent form.
 * @param v The vector to convert.
 *
 * Called for classes that do not have a CLID.
 * This will simply abort.
 */
template <class DV>
inline
void ViewVectorBase::doToPersistent1 (DV&, const std::false_type&)
{
  std::abort();
}
 
 
/**
 * @brief Convert to persistent form.
 * @param v The vector to convert.
 *
 * This will abort if called for a class with no CLID.
 */
template <class DV>
inline
void ViewVectorBase::doToPersistent (DV& v)
{
  // Dispatch depending on whether or not DV has a CLID.
  doToPersistent1 (v,
#ifdef XAOD_STANDALONE
                   std::true_type()
#else
                   typename ClassID_traits<DV>::has_classID_tag()
#endif
                   );
}
 
 
/**
 * @brief Convert to transient form.
 * @param v The vector to fill in.
 *
 * Called for classes that have a CLID if DV is not a ConstDataVector.
 */
template <class DV>
void ViewVectorBase::doToTransient2 (DV& v, const std::true_type&)
{
  // The custom DataVector collection proxy will have created elements here,
  // so we need to delete them to avoid a memory leak.
  // FIXME: It should be possible to avoid creating the elements
  // in the first place, at least for the usual case xAOD where the elements
  // themselves have no persistent data.
  if (v.ownPolicy() == SG::VIEW_ELEMENTS) {
    for (typename DV::value_type p : v) {
      // Try to protect against deleting an unowned object in the case
      // where this gets called multiple times on the same object.
      // The dummy elements will have null container pointers, while
      // those that we've retrieved through EL resolution below should
      // have the container pointer set.  Can only do this check, though,
      // for types with aux data.
      if (getContainer(p) == nullptr)
        delete p;
    }
  }
  v.clear (SG::VIEW_ELEMENTS);
  const EventContext& ctx = Gaudi::Hive::currentContext();
 
  assert (m_persKey.size() == m_persIndex.size());
  for (size_t i = 0; i < m_persKey.size(); i++) {
    ElementLink<DV> el (m_persKey[i], m_persIndex[i], ctx);
    // FIXME: const_cast
    typename DV::value_type p ATLAS_THREAD_SAFE = const_cast<typename DV::value_type> (*el);
    v.push_back (p);
  }
}
 
 
} // namespace SG