BranchWrapper.h

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/***********************************************************************************\
* (c) Copyright 2024-2026 CERN for the benefit of the LHCb and ATLAS collaborations *
*                                                                                   *
* This software is distributed under the terms of the Apache version 2 licence,     *
* copied verbatim in the file "LICENSE".                                            *
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* In applying this licence, CERN does not waive the privileges and immunities       *
* granted to it by virtue of its status as an Intergovernmental Organization        *
* or submit itself to any jurisdiction.                                             *
\***********************************************************************************/
#pragma once
 
#include <Gaudi/Algorithm.h>
#include <GaudiKernel/DataObjectHandle.h>
#include <TTree.h>
#include <gsl/pointers>
#include <string>
 
namespace Gaudi {
  namespace details {
    struct BranchWrapper {
 
    private:
      void const* m_dataBuffer = nullptr; // Data buffer for branch creation
      TBranch*    m_branch     = nullptr; // TBranch object
      bool        m_ownsBuffer = false;   // Whether we own the auto-allocated object in m_dataBuffer
      std::string m_className;            // Class name of the data
      std::string m_location;             // Location of the data in the data store
      void ( *setBranchAddress )( gsl::not_null<TBranch*>,
                                  const void** ); // Function pointer for the method used to set the address of the data
                                                  // buffer
 
    public:
      BranchWrapper( const gsl::not_null<TTree*> tree, const std::string& className, const std::string& branchName,
                     const std::string& location, const std::string& algName, unsigned int bufferSize = 32000,
                     unsigned int splitLevel = 99 );
      ~BranchWrapper();
      BranchWrapper( BranchWrapper&& other ) noexcept;
      BranchWrapper& operator=( BranchWrapper&& other ) noexcept;
      BranchWrapper( const BranchWrapper& )            = delete;
      BranchWrapper& operator=( const BranchWrapper& ) = delete;
 
      void               setDataPtr( void const* dataPtr );
      void               setBranchData( const gsl::not_null<DataObject*> pObj );
      const std::string& getLocation() const { return m_location; }
      const std::string& getClassName() const { return m_className; }
      void               setBufferSize( unsigned int size ) { m_branch->SetBasketSize( size ); }

      unsigned int computeOptimalBufferSize( unsigned int minBufferSize, unsigned int maxBufferSize,
                                             unsigned int approxEventsPerBasket, unsigned int splitLevel );
      void padEntries();
    };
 
  } // namespace details
} // namespace Gaudi