AthToolSupport/AsgDataHandles/AsgDataHandles/WriteHandle.icc

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/*
  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
*/
 
/**
 * @file AsgDataHandles/WriteHandle.icc
 * @author Nils Krumnack <Nils.Erik.Krumnack@cern.h>
 * @author S. Binet, P. Calafiura, scott snyder <snyder@bnl.gov> (for original version)
 * @brief Handle class for recording to StoreGate.
 */
 
#include "xAODRootAccess/TActiveStore.h"
#include "xAODRootAccess/TStore.h"
#include <stdexcept>
 
 
namespace SG {
 
 
//************************************************************************
// Constructors, etc.
//
 
 
// /**
//  * @brief Default constructor.
//  *
//  * The handle will not be usable until a non-blank key is assigned.
//  */
// template <class T>
// inline
// WriteHandle<T>::WriteHandle()
//   : VarHandleBase(ClassID_traits<T>::ID(), Gaudi::DataHandle::Writer)
// {
// }
 
 
/**
 * @brief Constructor with full arguments.
 * @param sgkey StoreGate key of the referenced object.
 */
template <class T>
inline
WriteHandle<T>::WriteHandle (const std::string& sgkey)
  : VarHandleBase (sgkey)
{
}
 
 
/**
 * @brief Constructor from a WriteHandleKey.
 * @param key The key object holding the clid/key/store.
 *
 * This will raise an exception if the StoreGate key is blank,
 * or if the event store cannot be found.
 */
template <class T>
inline
WriteHandle<T>::WriteHandle (const WriteHandleKey<T>& key)
  : VarHandleBase (key, nullptr)
{
}
 
 
/**
 * @brief Constructor from a WriteHandleKey and an explicit event context.
 * @param key The key object holding the clid/key.
 * @param ctx The event context.
 *
 * This will raise an exception if the StoreGate key is blank,
 * or if the event store cannot be found.
 *
 * If the default event store has been requested, then the thread-specific
 * store from the event context will be used.
 */
template <class T>
inline
WriteHandle<T>::WriteHandle (const WriteHandleKey<T>& key,
                             const EventContext& ctx)
  : VarHandleBase (key, &ctx)
{
}
 
 
/**
 * @brief Copy constructor.
 */
template <class T>
inline
WriteHandle<T>::WriteHandle(const WriteHandle& h)
  : VarHandleBase(h)
{
}
 
 
/**
 * @brief Move constructor.
 */
template <class T> 
WriteHandle<T>::WriteHandle(WriteHandle&& h)
  : VarHandleBase(std::move(h))
{
  // m_lockAuxPending = h.m_lockAuxPending;
  // h.m_lockAuxPending = nullptr;
}
 
 
/**
 * @brief Assignment operator.
 */
template <class T>
inline
WriteHandle<T>& 
WriteHandle<T>::operator= (const WriteHandle& h)
{
  if (this != &h)
    this->VarHandleBase::operator=(h);
  return *this;
}
 
 
/**
 * @brief Move operator.
 */
template <class T>
inline
WriteHandle<T>& 
WriteHandle<T>::operator= (WriteHandle&& h)
{
  if (this != &h) {
    this->VarHandleBase::operator=(std::move(h));
    // m_lockAuxPending = h.m_lockAuxPending;
    // h.m_lockAuxPending = nullptr;
  }
  return *this;
}
 
 
/**
 * @brief Destructor.
 *
 * Lock an aux object if m_lockAuxPending is true.
 */
template <class T>
WriteHandle<T>::~WriteHandle()
{
  // if (m_lockAuxPending) {
  //   m_lockAuxPending->setConst();
  // }
}
 
 
//************************************************************************
// Deference.  These all return only the cached pointer.
//
 
 
// /**
//  * @brief Dereference the pointer.
//  * Returns the cached pointer.  Throws ExcNullWriteHandle if null.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::pointer_type
// WriteHandle<T>::operator->()
// {
//   return WriteHandle<T>::checkedCachedPtr();
// }
 
 
/**
 * @brief Dereference the pointer.
 * Returns the cached pointer.  Throws ExcNullWriteHandle if null.
 */
template <class T>
inline
typename WriteHandle<T>::reference_type
WriteHandle<T>::operator*()
{
  if (m_ptr == nullptr)
    throw std::runtime_error ("dereferenced handle is null: " + key());
  return *m_ptr;
}
 
 
// /**
//  * @brief Dereference the pointer.
//  * Returns the cached pointer.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::cptr() const
// {
//   return reinterpret_cast<pointer_type>(this->m_ptr);
// }
 
 
// /**
//  * @brief Dereference the pointer.
//  * Returns the cached pointer.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::pointer_type
// WriteHandle<T>::ptr()
// {
//   return cachedPtr();
// }
 
 
// /**
//  * @brief Return the cached pointer directly; no lookup.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::pointer_type
// WriteHandle<T>::cachedPtr()
// {
//   return reinterpret_cast<pointer_type>(this->m_ptr);
// }
 
 
/**
 * @brief Can the handle be successfully dereferenced?
 */
template <class T>
inline
bool WriteHandle<T>::isValid()
{
  return this->m_ptr != nullptr;
}
 
 
//************************************************************************
// Record.
 
 
/**
 * @brief Record a const object to the store.
 * @param data The object to record.
 */
template <class T>
inline
StatusCode
WriteHandle<T>::WriteHandle::record (std::unique_ptr<T> data)
{
  m_ptr = data.get();
  if (xAOD::TActiveStore::store()->record (std::move (data), key()).isFailure())
    return StatusCode::FAILURE;
  return StatusCode::SUCCESS;
}
 
 
// /**
//  * @brief Record a non-const object to the store.
//  * @param data The object to record.
//  * @param isConst If true, record the object as const.
//  */
// template <class T>
// inline
// StatusCode
// WriteHandle<T>::WriteHandle::recordNonConst (std::unique_ptr<T> data)
// {
//   return this->doRecord (std::move(data), false, false);
// }
 
 
/**
 * @brief Record a const object and its auxiliary store to the store.
 * @param data The object to record.
 * @param auxstore Auxiliary store object.
 */
template <class T>
template <class AUXSTORE>
inline
StatusCode
WriteHandle<T>::WriteHandle::record (std::unique_ptr<T> data,
                                     std::unique_ptr<AUXSTORE> auxstore)
{
  // If there's no store association, do it now.
  if (data->getStore() == nullptr)
    data->setStore (auxstore.get());
 
  m_ptr = data.get();
  if (xAOD::TActiveStore::store()->record (std::move (auxstore), key() + "Aux.").isFailure())
    return StatusCode::FAILURE;
  if (xAOD::TActiveStore::store()->record (std::move (data), key()).isFailure())
    return StatusCode::FAILURE;
  return StatusCode::SUCCESS;
}
 
 
// /**
//  * @brief Record a non-const object and its auxiliary store to the store.
//  * @param data The object to record.
//  * @param auxstore Auxiliary store object.
//  */
// template <class T>
// template <class AUXSTORE>
// inline
// StatusCode
// WriteHandle<T>::WriteHandle::recordNonConst (std::unique_ptr<T> data,
//                                              std::unique_ptr<AUXSTORE> auxstore)
// {
//   return record (std::move(data), std::move(auxstore), false);
// }
 
 
// /**
//  * @brief Record a const shared DataObject to the store.
//  * @param data The object to record.
//  *
//  * The event store takes shared ownership of the object.
//  */
// template <class T>
// inline
// StatusCode
// WriteHandle<T>::record (SG::DataObjectSharedPtr<T> data)
// {
//   return this->doRecord (std::move(data), true, false);
// }
 
 
// /**
//  * @brief Record a non-const shared DataObject to the store.
//  * @param data The object to record.
//  *
//  * The event store takes shared ownership of the object.
//  */
// template <class T>
// inline
// StatusCode
// WriteHandle<T>::recordNonConst (SG::DataObjectSharedPtr<T> data)
// {
//   return this->doRecord (std::move(data), false, false);
// }
 
 
/**
 * @brief Record an object to the store.
 * @param data The object to record.
 * @param returnExisting Allow an existing object?
 *
 * Unlike record(), this does not change the handle object.
 * That means that one will not be able to get the object back
 * by dereferencing the handle.
 * Returns the object placed in the store, or nullptr if there
 * was an error.
 * If there was already an object in the store with the given key,
 * then return null, unless @c returnExisting is true, in which case
 * return success.  In either case, @c data is destroyed.
 */
template <class T>
inline
typename WriteHandle<T>::const_pointer_type
WriteHandle<T>::put (std::unique_ptr<T> data/*,
                     bool returnExisting / *= false*/) const
{
  const_pointer_type result = data.get();
  if (xAOD::TActiveStore::store()->record (std::move (data), key()).isFailure())
    throw std::runtime_error ("failed to record object: " + key());
  return result;
}
 
 
// /**
//  * @brief Record an object to the store.
//  * @param data The object to record.
//  * @param returnExisting Allow an existing object?
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, unless @c returnExisting is true, in which case
//  * return success.  In either case, @c data is destroyed.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (std::unique_ptr<const T> data,
//                      bool returnExisting /*= false*/) const
// {
//   IProxyDict* store = nullptr;
//   return doPut (nullptr, std::move(data), returnExisting, store);
// }
 
 
// /**
//  * @brief Record an object to the store.
//  * @param data The object to record.
//  * @param returnExisting Allow an existing object?
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, unless @c returnExisting is true, in which case
//  * return success.  In either case, @c data is destroyed.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (std::unique_ptr<const ConstDataVector<T> > data,
//                      bool returnExisting /*= false*/) const
// {
//   IProxyDict* store = nullptr;
//   std::unique_ptr<const T> coll (data.release()->asDataVector());
//   return doPut (nullptr, std::move(coll), returnExisting, store);
// }
 
 
// /**
//  * @brief Record an object to the store.
//  * @param ctx The event context to use.
//  * @param data The object to record.
//  * @param returnExisting Allow an existing object?
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, unless @c returnExisting is true, in which case
//  * return success.  In either case, @c data is destroyed.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (const EventContext& ctx,
//                      std::unique_ptr<const ConstDataVector<T> > data,
//                      bool returnExisting /*= false*/) const
// {
//   IProxyDict* store = nullptr;
//   std::unique_ptr<const T> coll (data.release()->asDataVector());
//   return doPut (&ctx, std::move(coll), returnExisting, store);
// }
 
 
// /**
//  * @brief Record an object to the store.
//  * @param ctx The event context to use.
//  * @param data The object to record.
//  * @param returnExisting Allow an existing object?
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, unless @c returnExisting is true, in which case
//  * return success.  In either case, @c data is destroyed.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (const EventContext& ctx,
//                      std::unique_ptr<T> data,
//                      bool returnExisting /*= false*/) const
// {
//   IProxyDict* store = nullptr;
//   return doPut (&ctx, std::move(data), returnExisting, store);
// }
 
 
// /**
//  * @brief Record an object to the store.
//  * @param ctx The event context to use.
//  * @param data The object to record.
//  * @param returnExisting Allow an existing object?
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, unless @c returnExisting is true, in which case
//  * return success.  In either case, @c data is destroyed.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (const EventContext& ctx,
//                      std::unique_ptr<const T> data,
//                      bool returnExisting /*= false*/) const
// {
//   IProxyDict* store = nullptr;
//   return doPut (&ctx, std::move(data), returnExisting, store);
// }
 
 
// /**
//  * @brief Record an object to the store.
//  * @param data The object to record.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  *
//  * The event store takes shared ownership of the object.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (SG::DataObjectSharedPtr<T> data) const
// {
//   IProxyDict* store = nullptr;
//   return doPut (nullptr, std::move(data), false, store);
// }
 
 
// /**
//  * @brief Record an object to the store.
//  * @param ctx The event context to use.
//  * @param data The object to record.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  *
//  * The event store takes shared ownership of the object.
//  */
// template <class T>
// inline
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (const EventContext& ctx,
//                      SG::DataObjectSharedPtr<T> data) const
// {
//   IProxyDict* store = nullptr;
//   return doPut (&ctx, std::move(data), false, store);
// }
 
 
// /**
//  * @brief Record an object and its auxiliary store to the store.
//  * @param data The object to record.
//  * @param auxstore Auxiliary store object.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, and the objects passed in are destroyed.
//  */
// template <class T>
// template <class AUXSTORE>
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (std::unique_ptr<T> data,
//                      std::unique_ptr<AUXSTORE> auxstore) const
// {
//   return doPut (nullptr, std::move(data), std::move(auxstore));
// }
 
 
 
// /**
//  * @brief Record an object and its auxiliary store to the store.
//  * @param data The object to record.
//  * @param auxstore Auxiliary store object.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, and the objects passed in are destroyed.
//  *
//  * Unlike the version taking unique_ptr<T>, this does not alter the
//  * store pointer of @c data.
//  */
// template <class T>
// template <class AUXSTORE>
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (std::unique_ptr<const T> data,
//                      std::unique_ptr<const AUXSTORE> auxstore) const
// {
//   return doPut (nullptr, std::move(data), std::move(auxstore));
// }
 
 
// /**
//  * @brief Record an object and its auxiliary store to the store.
//  * @param ctx The event context to use.
//  * @param data The object to record.
//  * @param auxstore Auxiliary store object.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, and the objects passed in are destroyed.
//  */
// template <class T>
// template <class AUXSTORE>
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (const EventContext& ctx,
//                      std::unique_ptr<T> data,
//                      std::unique_ptr<AUXSTORE> auxstore) const
// {
//   return doPut (&ctx, std::move(data), std::move(auxstore));
// }
 
 
// /**
//  * @brief Record an object and its auxiliary store to the store.
//  * @param ctx The event context to use.
//  * @param data The object to record.
//  * @param auxstore Auxiliary store object.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that one will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, and the objects passed in are destroyed.
//  *
//  * Unlike the version taking unique_ptr<T>, this does not alter the
//  * store pointer of @c data.
//  */
// template <class T>
// template <class AUXSTORE>
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::put (const EventContext& ctx,
//                      std::unique_ptr<const T> data,
//                      std::unique_ptr<const AUXSTORE> auxstore) const
// {
//   return doPut (&ctx, std::move(data), std::move(auxstore));
// }
 
 
/**
 * @brief Alternate notation for record.  Records a non-const object.
 * @param data Object to record.
 *
 * Throws an exception on failure.
 */
template <class T>
WriteHandle<T>& 
WriteHandle<T>::operator= (std::unique_ptr<T> data)
{
  if (recordNonConst (std::move(data)).isFailure()) {
    throw std::runtime_error ("WriteHandle<T>::operator=(unique_ptr) Record failed.");
  }
  return *this;
}
 
 
// /**
//  * @brief Make an alias.
//  * @param key Alternate key by which the referenced object should be known.
//  *
//  * The current handle should be valid and referencing an object
//  * (i.e., @c record should have been called on it).
//  *
//  * The object will also be known by the name given in @c key.
//  */
// template <class T>
// StatusCode WriteHandle<T>::alias (const WriteHandleKey<T>& key)
// {
//   return symLink_impl (this->clid(), key.key());
// }
 
 
// /**
//  * @brief Make an explicit link.
//  * @param key Alternate clid by which the referenced object
//  *            should be known.  The SG key must match the key of the
//  *            current handle.
//  *
//  * You should generally not be using this!
//  *
//  * The current handle should be valid and referencing an object
//  * (i.e., @c record should have been called on it).
//  *
//  * This makes a symlink: the object will be retrievable
//  * as a different type.
//  * 
//  * Note that if @c T and @c @U are related via @c SG_BASE and/or
//  * @c DATAVECTOR_BASE, then you shouldn't need to explicitly make a symlink;
//  * that should happen automatically.
//  *
//  * If a @c U* is not convertable to a @c T* via C++ rules, then you likely
//  * will be, at best, relying on undefined behavior.  You will probably
//  * get warnings from the undefined behavior sanitizer when if you try
//  * to dereference the @c U*.
//  *
//  * This usage is here mainly to assist in migrating some existing
//  * patterns to MT.  You should think several times before using
//  * in new code.
//  */
// template <class T>
// template <class U>
// StatusCode WriteHandle<T>::symLink (const WriteHandleKey<U>& other)
// {
//   if (this->key() != other.key()) {
//     REPORT_ERROR (StatusCode::FAILURE)
//       << "symLink: SG keys do not match: " << other.key() << " vs "
//       << this->key();
//     return StatusCode::FAILURE;
//   }
//   return symLink_impl (other.clid(), other.key());
// }
 
 
// /**
//  * @brief Return the cached pointer directly.
//  *
//  * If it is null, throw ExcNullWriteHandle.
//  */
// template <class T>
// typename WriteHandle<T>::pointer_type
// WriteHandle<T>::checkedCachedPtr()
// {
//   if (!m_ptr)
//     throwExcNullWriteHandle (clid(), key(), store());
//   return cachedPtr();
// }
 
 
// /**
//  * @brief Helper for record.
//  * @param data The object to record.
//  * @param isConst If true, record the object as const.
//  * @param returnExisting Allow an existing object.
//  */
// template <class T>
// template <class U>
// StatusCode WriteHandle<T>::doRecord (U data,
//                                      bool isConst,
//                                      bool returnExisting)
// {
//   typedef typename U::element_type elt_t;
  
//   // make sure the BaseInfo(Base) structure is initialized
//   SG::BaseInfo<elt_t>::baseinfo();
 
//   // If s_isConst is set for this type, then we want to automatically
//   // make it const when recorded.
//   bool allowMods = !isConst;
//   if (ClassID_traits<elt_t>::s_isConst)
//     allowMods = false;
 
//   void* dataPtr(data.get());
//   std::unique_ptr<DataObject> dobj (SG::asStorable (std::move (data)));
//   return this->record_impl (std::move(dobj), dataPtr, allowMods, returnExisting);
// }
 
 
// /**
//  * @brief Helper for put.
//  * @param ctx The event context, or nullptr to use the current context.
//  * @param data The object to record.
//  * @param returnExisting Allow an existing object.
//  * @param[out] store The store being used.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, unless @c returnExisting is true, in which case
//  * return success.  In either case, @c data is destroyed.
//  */
// template <class T>
// template <class U>
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::doPut (const EventContext* ctx,
//                        U data,
//                        bool returnExisting,
//                        IProxyDict* & store) const
// {
//   //typedef typename U::element_type elt_t;
//   typedef T elt_t;
  
//   // make sure the BaseInfo(Base) structure is initialized
//   SG::BaseInfo<elt_t>::baseinfo();
 
//   const void* dataPtr = data.get();
//   std::unique_ptr<DataObject> dobj (SG::asStorable (std::move (data)));
//   return reinterpret_cast<const T*>
//     (this->put_impl (ctx, std::move(dobj), dataPtr, false, returnExisting, store));
// }
 
 
// /**
//  * @brief Helper for recording an object and its auxiliary store to the store.
//  * @param ctx The event context, or nullptr to use the current context.
//  * @param data The object to record.
//  * @param auxstore Auxiliary store object.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, and the objects passed in are destroyed.
//  */
// template <class T>
// template <class AUXSTORE>
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::doPut (const EventContext* ctx,
//                        std::unique_ptr<T> data,
//                        std::unique_ptr<AUXSTORE> auxstore) const
// {
//   T& dref = *data;
 
//   // If there's no store association, do it now.
//   if (data->getStore() == nullptr)
//     data->setStore (auxstore.get());
 
//   IProxyDict* store = nullptr;
//   const T* ptr = this->doPut (ctx, std::move(data), false, store);
//   if (!ptr) return nullptr;
 
//   SG::DataObjectSharedPtr<DataObject> dobj
//     (SG::asStorable (std::move (auxstore)));
//   SG::DataProxy* proxy = store->recordObject (std::move(dobj),
//                                               this->name() + "Aux.",
//                                               false,
//                                               false);
//   if (!proxy) {
//     REPORT_ERROR (StatusCode::FAILURE)
//       << "recordObject of aux store failed";
 
//     // If we've failed here, then the aux store object has been deleted,
//     // but not the primary object.  Null out the store pointer to prevent
//     // having a dangling pointer to a deleted object.
//     dref.setStore (static_cast<SG::IConstAuxStore*>(nullptr));
//     return nullptr;
//   }
 
//   return ptr;
// }
 
 
// /**
//  * @brief Helper for recording an object and its auxiliary store to the store.
//  * @param ctx The event context, or nullptr to use the current context.
//  * @param data The object to record.
//  * @param auxstore Auxiliary store object.
//  *
//  * Unlike record(), this does not change the handle object.
//  * That means that will not be able to get the object back
//  * by dereferencing the handle.
//  * Returns the object placed in the store, or nullptr if there
//  * was an error.
//  * If there was already an object in the store with the given key,
//  * then return null, and the objects passed in are destroyed.
//  */
// template <class T>
// template <class AUXSTORE>
// typename WriteHandle<T>::const_pointer_type
// WriteHandle<T>::doPut (const EventContext* ctx,
//                        std::unique_ptr<const T> data,
//                        std::unique_ptr<const AUXSTORE> auxstore) const
// {
//   IProxyDict* store = nullptr;
//   const T* ptr = this->doPut (ctx, std::move(data), false, store);
//   if (!ptr) return nullptr;
 
//   SG::DataObjectSharedPtr<DataObject> dobj
//     (SG::asStorable (std::move (auxstore)));
//   SG::DataProxy* proxy = store->recordObject (std::move(dobj),
//                                               this->name() + "Aux.",
//                                               false,
//                                               false);
//   if (!proxy) {
//     REPORT_ERROR (StatusCode::FAILURE)
//       << "recordObject of aux store failed";
//     return nullptr;
//   }
 
//   return ptr;
// }
 
 
// /**
//  * @brief Record an object and its auxiliary store to the store.
//  * @param data The object to record.
//  * @param auxstore Auxiliary store object.
//  * @param isConst If true, record the objects as const.
//  */
// template <class T>
// template <class AUXSTORE>
// StatusCode
// WriteHandle<T>::record (std::unique_ptr<T> data,
//                         std::unique_ptr<AUXSTORE> auxstore,
//                         bool isConst)
// {
//   T& dref = *data;
 
//   // If there's no store association, do it now.
//   if (data->getStore() == nullptr)
//     data->setStore (auxstore.get());
 
//   if (isConst) {
//     // Temporarily clear the store association, in order to prevent
//     // the aux store from being locked at this point.
//     IAuxStore* store = dref.getStore();
//     if (store)
//       dref.setStore (static_cast<SG::IAuxStore*>(nullptr));
//     CHECK (this->record(std::move(data)));
//     // Deliberately not using RAII here.  If there is an error,
//     // then the object referenced by data will be deleted.
//     dref.setStore (store);
//   }
//   else
//     CHECK (this->recordNonConst(std::move(data)));
 
//   // Store and proxy must be valid if we get to this point.
  
//   SG::DataObjectSharedPtr<DataObject> dobj
//     (SG::asStorable (std::move (auxstore)));
//   SG::DataProxy* proxy = m_store->recordObject (std::move(dobj),
//                                                 this->name() + "Aux.",
//                                                 true,
//                                                 false);
//   if (!proxy) {
//     REPORT_ERROR (StatusCode::FAILURE)
//       << "recordObject of aux store failed";
 
//     // If we've failed here, then the aux store object has been deleted,
//     // but not the primary object.  Null out the store pointer to prevent
//     // having a dangling pointer to a deleted object.
//     dref.setStore (static_cast<SG::IConstAuxStore*>(nullptr));
//     return StatusCode::FAILURE;
//   }
 
//   if (m_proxy->isConst())
//     m_lockAuxPending = proxy;
 
//   return StatusCode::SUCCESS;
// }
 
 
/**
 * @brief Return a @c WriteHandle referencing @c key.
 * @param key The key object holding the clid/key/store.
 *
 * This will raise an exception if the StoreGate key is blank,
 * or if the event store cannot be found.
 */
template <class T>
WriteHandle<T> makeHandle (const WriteHandleKey<T>& key)
{
  return WriteHandle<T> (key);
}
 
 
/**
 * @brief Return a @c WriteHandle referencing @c key for an explicit context.
 * @param key The key object holding the clid/key/store.
 * @param ctx The event context.
 *
 * This will raise an exception if the StoreGate key is blank,
 * or if the event store cannot be found.
 *
 * If the default event store has been requested, then the thread-specific
 * store from the event context will be used.
 */
template <class T>
WriteHandle<T> makeHandle (const WriteHandleKey<T>& key,
                           const EventContext& ctx)
{
  return WriteHandle<T> (key, ctx);
}
 
 
} /* namespace SG */