AthToolSupport/AsgDataHandles/AsgDataHandles/WriteHandle.h

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// This file's extension implies that it's C, but it's really -*- C++ -*-.
 
/*
  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef ASG_DATA_HANDLES_WRITE_HANDLE_H
#define ASG_DATA_HANDLES_WRITE_HANDLE_H
 
#ifndef XAOD_STANDALONE
#include <StoreGate/WriteHandle.h>
#else
 
#include "AsgDataHandles/VarHandleBase.h"
#include "AsgDataHandles/WriteHandleKey.h"
#include <string>
#include <memory> /*unique_ptr*/
 
 
namespace SG {
 
 
template <class T>
class WriteHandle
  : public SG::VarHandleBase
{ 
public: 
  typedef T*               pointer_type; // FIXME: better handling of
  typedef const T*   const_pointer_type; //        qualified T type ?
  typedef T&             reference_type;
  typedef const T& const_reference_type;
 
 
  //************************************************************************
  // Constructors, etc.
  //
 
 
  // /**
  //  * @brief Default constructor.
  //  *
  //  * The handle will not be usable until a non-blank key is assigned.
  //  */
  // WriteHandle();
 
 
  explicit WriteHandle(const std::string& sgkey);
 
 
  explicit WriteHandle (const WriteHandleKey<T>& key);
 
 
  explicit WriteHandle (const WriteHandleKey<T>& key, const EventContext& ctx);
 
  
  WriteHandle( const WriteHandle& rhs );
 
 
  WriteHandle( WriteHandle&& rhs );
 
 
  WriteHandle& operator=( const WriteHandle& rhs ); 
 
 
  WriteHandle& operator=( WriteHandle&& rhs );
 
 
  ~WriteHandle();
 
 
  //************************************************************************
  // Deference.  These all return only the cached pointer.
  //
 
 
  // /**
  //  * @brief Dereference the pointer.
  //  * Returns the cached pointer.  Throws ExcNullWriteHandle if null.
  //  */
  // pointer_type operator->();
 
 
  reference_type operator*();
 
 
  // /**
  //  * @brief Dereference the pointer.
  //  * Returns the cached pointer.
  //  */
  // const_pointer_type cptr() const;
 
 
  // /**
  //  * @brief Dereference the pointer.
  //  * Returns the cached pointer.
  //  */
  // pointer_type ptr();
 
 
  // /**
  //  * @brief Return the cached pointer directly; no lookup.
  //  */
  // pointer_type cachedPtr();
 
 
  bool isValid();
 
 
  //************************************************************************
  // Record.
  //
 
 
  StatusCode record (std::unique_ptr<T> data);
 
 
  // /**
  //  * @brief Record a non-const object to the store.
  //  * @param data The object to record.
  //  */
  // StatusCode recordNonConst (std::unique_ptr<T> data);
 
  
  template <class AUXSTORE>
  StatusCode record (std::unique_ptr<T> data,
                     std::unique_ptr<AUXSTORE> store);
 
 
  // /**
  //  * @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 AUXSTORE>
  // StatusCode recordNonConst (std::unique_ptr<T> data,
  //                            std::unique_ptr<AUXSTORE> store);
 
 
  // /**
  //  * @brief Record a const shared DataObject to the store.
  //  * @param data The object to record.
  //  *
  //  * The event store takes shared ownership of the object.
  //  */
  // StatusCode record (SG::DataObjectSharedPtr<T> data);
 
 
  // /**
  //  * @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.
  //  */
  // StatusCode recordNonConst (SG::DataObjectSharedPtr<T> data);
 
 
  const_pointer_type put (std::unique_ptr<T> data/*,
                          bool returnExisting = false*/) const;
 
 
  // /**
  //  * @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.
  //  */
  // const_pointer_type put (std::unique_ptr<const T> data,
  //                         bool returnExisting = false) const;
 
 
  // /**
  //  * @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.
  //  */
  // const_pointer_type put (std::unique_ptr<const ConstDataVector<T> > data,
  //                         bool returnExisting = false) const;
 
 
  // /**
  //  * @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.
  //  */
  // const_pointer_type put (const EventContext& ctx,
  //                         std::unique_ptr<const ConstDataVector<T> > data,
  //                         bool returnExisting = false) const;
 
 
  // /**
  //  * @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.
  //  */
  // const_pointer_type put (const EventContext& ctx,
  //                         std::unique_ptr<T> data,
  //                         bool returnExisting = false) const;
 
 
  // /**
  //  * @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.
  //  */
  // const_pointer_type put (const EventContext& ctx,
  //                         std::unique_ptr<const T> data,
  //                         bool returnExisting = false) const;
 
 
  // /**
  //  * @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.
  //  */
  // const_pointer_type put (SG::DataObjectSharedPtr<T> data) const;
 
 
  // /**
  //  * @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.
  //  */
  // const_pointer_type put (const EventContext& ctx,
  //                         SG::DataObjectSharedPtr<T> data) const;
 
 
  // /**
  //  * @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 AUXSTORE>
  // const_pointer_type
  // put (std::unique_ptr<T> data,
  //      std::unique_ptr<AUXSTORE> auxstore) const;
 
 
  // /**
  //  * @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 AUXSTORE>
  // const_pointer_type
  // put (std::unique_ptr<const T> data,
  //      std::unique_ptr<const AUXSTORE> auxstore) const;
 
 
  // /**
  //  * @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 AUXSTORE>
  // const_pointer_type
  // put (const EventContext& ctx,
  //      std::unique_ptr<T> data,
  //      std::unique_ptr<AUXSTORE> auxstore) const;
 
 
  // /**
  //  * @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 AUXSTORE>
  // const_pointer_type
  // put (const EventContext& ctx,
  //      std::unique_ptr<const T> data,
  //      std::unique_ptr<const AUXSTORE> auxstore) const;
 
 
  WriteHandle& operator=( std::unique_ptr<T> data );
 
 
  // /**
  //  * @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.
  //  */
  // StatusCode alias (const WriteHandleKey<T>& 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 U>
  // StatusCode symLink (const WriteHandleKey<U>& key);
 
  
private:
  // /**
  //  * @brief Return the cached pointer directly.
  //  *
  //  * If it is null, throw ExcNullWriteHandle.
  //  */
  // pointer_type checkedCachedPtr();
 
 
  // /**
  //  * @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 U>
  // StatusCode doRecord (U data,
  //                      bool isConst,
  //                      bool 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 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 U>
  // const_pointer_type doPut (const EventContext* ctx,
  //                           U data,
  //                           bool returnExisting,
  //                           IProxyDict* & store) const;
  
 
  // /**
  //  * @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 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 AUXSTORE>
  // typename WriteHandle<T>::const_pointer_type
  // doPut (const EventContext* ctx,
  //        std::unique_ptr<T> data,
  //        std::unique_ptr<AUXSTORE> auxstore) const;
 
 
  // /**
  //  * @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 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 AUXSTORE>
  // typename WriteHandle<T>::const_pointer_type
  // doPut (const EventContext* ctx,
  //        std::unique_ptr<const T> data,
  //        std::unique_ptr<const AUXSTORE> auxstore) const;
 
 
  // /**
  //  * @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 AUXSTORE>
  // StatusCode
  // record (std::unique_ptr<T> data,
  //         std::unique_ptr<AUXSTORE> auxstore,
  //         bool isConst);
 
 
private:
  // /// If non-null, then we need to lock the associated aux store object
  // /// when we're deleted.
  // ///
  // /// This is set when we record an object along with the associated aux const
  // /// with the const flag set (the default).  Recall that for a const record,
  // /// we want to support the semantics that you can get a non-const pointer
  // /// back from the handle as long as it exists, to finish initialization
  // /// of the object.  For an aux store, though, just getting back a non-const
  // /// pointer is not sufficient, since the store will have been locked
  // /// at the time of the record, preventing changes to the store.
  // ///
  // /// So if we're meant to record a const aux store object, we don't actually
  // /// set it const on the record, but instead set this and do the
  // /// setConst in the destructor.
  // SG::DataProxy* m_lockAuxPending = nullptr;
 
  T *m_ptr {nullptr};
}; 
 
 
template <class T>
WriteHandle<T> makeHandle (const WriteHandleKey<T>& key);
 
 
template <class T>
WriteHandle<T> makeHandle (const WriteHandleKey<T>& key,
                           const EventContext& ctx);
 
 
} /* namespace SG */
 
 
#include "AsgDataHandles/WriteHandle.icc"
 
 
// #ifndef NO_LEGACY_HANDLES
// namespace SG {
//   template <class T>
//   using WVar = WriteHandle<T>;
// } 
// #endif
 
#endif
 
#endif