CustomLoaderHelpers.hxx

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// Author: Vincenzo Eduardo Padulano CERN 10/2026
// Author: Silia Taider CERN 10/2026
 
#ifndef ROOT_RDF_CUSTOMLOADERHELPERS
#define ROOT_RDF_CUSTOMLOADERHELPERS
 
#include <ROOT/RDF/RActionImpl.hxx>
#include <ROOT/RVec.hxx>
 
#include <cstddef>
#include <memory>
#include <typeinfo>
#include <vector>
 
class TTreeReader;
 
namespace ROOT::Internal::RDF {
 
class R__CLING_PTRCHECK(off) CustomLoaderHelper : public ROOT::Detail::RDF::RActionImpl<CustomLoaderHelper> {
public:
   /// Converts one type-erased column value to float and appends it to the destination vector,
   /// vector columns are truncated or padded to their maximum size
   using ColHandler_t = void (*)(ROOT::RVecF &, void *, std::size_t maxSize, float padding);
 
private:
   std::shared_ptr<ROOT::RVecF> fLocation;
   /// One handler per input column, resolved once from the column types
   std::vector<ColHandler_t> fColHandlers;
   /// Maximum size of each input column, resolved once from the vector sizes, only used for vector columns
   std::vector<std::size_t> fMaxSizes;
   /// Value used to pad vector columns shorter than their maximum size
   float fVecPadding;
 
public:
   CustomLoaderHelper(const std::shared_ptr<ROOT::RVecF> &location,
                      const std::vector<const std::type_info *> &colTypeIDs, const std::vector<std::size_t> &vecSizes,
                      float vecPadding);
 
   CustomLoaderHelper(CustomLoaderHelper &&) = default;
   CustomLoaderHelper &operator=(CustomLoaderHelper &&) = default;
   CustomLoaderHelper(const CustomLoaderHelper &) = delete;
   CustomLoaderHelper &operator=(const CustomLoaderHelper &) = delete;
   ~CustomLoaderHelper() override = default;
 
   void InitTask(TTreeReader *, unsigned int) {}
   // TODO(staider) Support multiple slots to also work in IMT mode
   void Exec([[maybe_unused]] unsigned int slot, const std::vector<void *> &values);
   void Initialize() { /* noop */ }
   void Finalize() {}
 
   std::string GetActionName() { return "CustomLoaderHelper"; }
};
} // namespace ROOT::Internal::RDF
 
#endif // ROOT_RDF_CUSTOMLOADERHELPERS