RNTupleExporter.hxx

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/// \file ROOT/RNTupleExporter.hxx
/// \ingroup NTuple ROOT7
/// \author Giacomo Parolini <giacomo.parolini@cern.ch>
/// \date 2024-12-10
/// \warning This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback
/// is welcome!
 
/*************************************************************************
 * Copyright (C) 1995-2024, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#ifndef ROOT7_RNTupleExporter
#define ROOT7_RNTupleExporter
 
#include <ROOT/RNTupleTypes.hxx>
 
#include <cstdint>
#include <string>
#include <vector>
#include <unordered_set>
 
namespace ROOT::Internal {
class RPageSource;
}
 
namespace ROOT::Experimental::Internal {
 
class RNTupleExporter {
public:
   enum class EFilterType {
      /// Don't export items contained in the filter's set
      kBlacklist,
      /// Export only items contained in the filter's set
      kWhitelist
   };
 
   template <typename T>
   struct RFilter {
      std::unordered_set<T> fSet;
      EFilterType fType = EFilterType::kBlacklist;
   };
 
   struct RPagesOptions {
      enum RExportPageFlags {
         kNone = 0x0,
         kIncludeChecksums = 0x1,
         /// If enabled, the exporter will report the current progress on the stderr
         kShowProgressBar = 0x2,
         /// If enabled, uncompress (but don't unpack) the page (mutually exclusive with kIncludeChecksums)
         kDecompress = 0x04,
 
         kDefaults = kShowProgressBar
      };
 
      std::string fOutputPath;
      std::uint64_t fFlags;
 
      /// Optional filter that determines which columns are included or excluded from being exported.
      /// By default, export all columns. If you only want to include certain column types, add them
      /// to `fColumnTypeFilter.fSet` and change `fColumnTypeFilter.fType` to kWhitelist.
      RFilter<ENTupleColumnType> fColumnTypeFilter;
 
      RPagesOptions() : fOutputPath("."), fFlags(kDefaults) {}
   };
 
   struct RPagesResult {
      std::vector<std::string> fExportedFileNames;
   };
 
   /// Given a page source, writes all its pages to individual files (1 per page).
   /// If the source is not already attached, it will be attached by this process.
   static RPagesResult ExportPages(ROOT::Internal::RPageSource &source, const RPagesOptions &options = {});
};
 
} // namespace ROOT::Experimental::Internal
 
#endif