doc/master/rfile002__rntuple_8C.html

void write_rntuple_to_rfile(const char *fileName)

{

   // Create a new ROOT file for writing

   auto file = ROOT::Experimental::RFile::Recreate(fileName);


   // Define the RNTuple schema

   auto model = ROOT::RNTupleModel::Create();

   auto pInt = model->MakeField<int>("intField");


   // Create an RNTupleWriter to append to the RFile

   auto writer = ROOT::Experimental::RNTupleWriter_Append(std::move(model), "ntuple", *file);


   // Fill the RNTuple with data

   for (int i = 0; i < 10; ++i) {

      *pInt = i;

      writer->Fill();

   }


   // `writer` will write the data to file upon destruction. Then `file` will write itself to disk in turn.

}


void read_rntuple_from_rfile(const char *fileName)

{

   // Open an existing ROOT file for reading (will throw an exception if `fileName` cannot be read).

   auto file = ROOT::Experimental::RFile::Open(fileName);


   // Get back the RNTuple anchor from the file

   auto rntuple = file->Get<ROOT::RNTuple>("ntuple");

   R__ASSERT(rntuple); // we just wrote the RNTuple to the file so we expect to find it


   // Create an RNTupleReader from the anchor

   auto reader = ROOT::RNTupleReader::Open(*rntuple);

   auto pInt = reader->GetModel().GetDefaultEntry().GetPtr<int>("intField");


   for (auto i : reader->GetEntryRange()) {

      reader->LoadEntry(i);

      std::cout << "value[" << i << "] = " << *pInt << "\n";

   }

}


void rfile002_rntuple()

{

   const char *const fileName = "rfile_rntuple.root";


   write_rntuple_to_rfile(fileName);

   read_rntuple_from_rfile(fileName);


   gSystem->Unlink(fileName);

}

R__ASSERT
#define R__ASSERT(e)
Checks condition e and reports a fatal error if it's false.
Definition TError.h:139

gSystem
R__EXTERN TSystem * gSystem
Definition TSystem.h:582

ROOT::Experimental::RFile::Open
static std::unique_ptr< RFile > Open(std::string_view path, const ROpenOptions &opts=ROpenOptions())
Opens the file for reading.
Definition RFile.cxx:204

ROOT::Experimental::RFile::Recreate
static std::unique_ptr< RFile > Recreate(std::string_view path, const RRecreateOptions &opts=RRecreateOptions())
Opens the file for reading/writing, overwriting it if it already exists.
Definition RFile.cxx:226

ROOT::RNTupleModel::Create
static std::unique_ptr< RNTupleModel > Create()
Definition RNTupleModel.cxx:339

ROOT::RNTupleReader::Open
static std::unique_ptr< RNTupleReader > Open(std::string_view ntupleName, std::string_view storage, const ROOT::RNTupleReadOptions &options=ROOT::RNTupleReadOptions())
Open an RNTuple for reading.
Definition RNTupleReader.cxx:189

ROOT::RNTuple
Representation of an RNTuple data set in a ROOT file.
Definition RNTuple.hxx:67

TSystem::Unlink
virtual int Unlink(const char *name)
Unlink, i.e.
Definition TSystem.cxx:1403

ROOT::Experimental::RNTupleWriter_Append
std::unique_ptr< RNTupleWriter > RNTupleWriter_Append(std::unique_ptr< ROOT::RNTupleModel > model, std::string_view ntuplePath, ROOT::Experimental::RFile &file, const ROOT::RNTupleWriteOptions &options=ROOT::RNTupleWriteOptions())
Creates an RNTupleWriter that writes into the given file, appending to it.
Definition RNTupleWriter.cxx:167

rfile002_rntuple
Definition rfile002_rntuple.py:1

writer
Definition writer.py:1