RNTupleAttrWriting.cxx

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/// \file RNTupleAttrWriting.cxx
/// \author Giacomo Parolini <giacomo.parolini@cern.ch>
/// \date 2026-01-27
/// \warning This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback
/// is welcome!
 
#include <ROOT/RNTupleAttrWriting.hxx>
#include <ROOT/RNTupleAttrUtils.hxx>
#include <ROOT/RNTupleModel.hxx>
#include <ROOT/RNTupleFillContext.hxx>
#include <ROOT/RPageStorageFile.hxx>
#include <ROOT/StringUtils.hxx>
 
using namespace ROOT::Experimental::Internal::RNTupleAttributes;
 
static ROOT::RResult<void> ValidateAttributeModel(const ROOT::RNTupleModel &model)
{
   const auto &projFields = ROOT::Internal::GetProjectedFieldsOfModel(model);
   if (!projFields.IsEmpty())
      return R__FAIL("The Model used to create an AttributeSet cannot contain projected fields.");
 
   for (const auto &field : model.GetConstFieldZero()) {
      if (field.GetStructure() == ROOT::ENTupleStructure::kStreamer)
         return R__FAIL(std::string("The Model used to create an AttributeSet cannot contain Streamer field '") +
                        field.GetQualifiedFieldName() + "'");
   }
   return ROOT::RResult<void>::Success();
}
 
//
//  RNTupleAttrEntry
//
std::size_t ROOT::Experimental::Internal::RNTupleAttrEntry::Append()
{
   std::size_t bytesWritten = 0;
   // Write the meta entry values
   bytesWritten += fMetaEntry.fValues[kMetaFieldIndex_RangeStart].Append();
   bytesWritten += fMetaEntry.fValues[kMetaFieldIndex_RangeLen].Append();
 
   // Bind the user model's memory to the meta model's subfields
   const auto &userFields = ROOT::Internal::GetFieldZeroOfModel(fMetaModel)
                               .GetMutableSubfields()[kMetaFieldIndex_UserData]
                               ->GetMutableSubfields();
   assert(userFields.size() == fScopedEntry.fValues.size());
   for (std::size_t i = 0; i < fScopedEntry.fValues.size(); ++i) {
      std::shared_ptr<void> userPtr = fScopedEntry.fValues[i].GetPtr<void>();
      auto value = userFields[i]->BindValue(userPtr);
      bytesWritten += value.Append();
   }
   return bytesWritten;
}
 
//
//  RNTupleAttrSetWriter
//
std::unique_ptr<ROOT::Experimental::RNTupleAttrSetWriter>
ROOT::Experimental::RNTupleAttrSetWriter::Create(const RNTupleFillContext &mainFillContext,
                                                 std::unique_ptr<ROOT::Internal::RPageSink> sink,
                                                 std::unique_ptr<RNTupleModel> userModel)
 
{
   ValidateAttributeModel(*userModel).ThrowOnError();
 
   // We create a "meta model" that's what we'll use to write data to storage. This meta model has 3 fields:
   // the "meta fields" _rangeStart / _rangeLen and an untyped Record field which contains all the top-level fields
   // from the user model as its children. This is done to "namespace" all user-defined attribute fields so that we
   // are free to use whichever name we want for our meta fields.
   // Note that the user model is preserved as-is to allow the user to create entries from it or use its default
   // entry. When we actually write data to storage, we do some pointer trickery to correctly read the values from
   // the user model and store them under the meta model's fields (see RNTupleAttrEntry::Append())
   auto metaModel = RNTupleModel::Create();
   metaModel->SetDescription(userModel->GetDescription());
   auto rangeStartPtr = metaModel->MakeField<ROOT::NTupleSize_t>(kMetaFieldNames[kMetaFieldIndex_RangeStart]);
   auto rangeLenPtr = metaModel->MakeField<ROOT::NTupleSize_t>(kMetaFieldNames[kMetaFieldIndex_RangeLen]);
   std::vector<std::unique_ptr<RFieldBase>> fields;
   const auto subfields = userModel->GetConstFieldZero().GetConstSubfields();
   fields.reserve(subfields.size());
   for (const auto *field : subfields) {
      fields.push_back(field->Clone(field->GetFieldName()));
   }
   auto userRootField =
      std::make_unique<ROOT::RRecordField>(kMetaFieldNames[kMetaFieldIndex_UserData], std::move(fields));
   metaModel->AddField(std::move(userRootField));
 
   metaModel->Freeze();
   userModel->Freeze();
 
   return std::unique_ptr<RNTupleAttrSetWriter>(
      new RNTupleAttrSetWriter(mainFillContext, std::move(sink), std::move(metaModel), std::move(userModel),
                               std::move(rangeStartPtr), std::move(rangeLenPtr)));
}
 
ROOT::Experimental::RNTupleAttrSetWriter::RNTupleAttrSetWriter(const RNTupleFillContext &mainFillContext,
                                                               std::unique_ptr<ROOT::Internal::RPageSink> sink,
                                                               std::unique_ptr<RNTupleModel> metaModel,
                                                               std::unique_ptr<RNTupleModel> userModel,
                                                               std::shared_ptr<ROOT::NTupleSize_t> rangeStartPtr,
                                                               std::shared_ptr<ROOT::NTupleSize_t> rangeLenPtr)
   : fFillContext(std::move(metaModel), std::move(sink)),
     fMainFillContext(&mainFillContext),
     fUserModel(std::move(userModel)),
     fRangeStartPtr(std::move(rangeStartPtr)),
     fRangeLenPtr(std::move(rangeLenPtr))
{
}
 
ROOT::Experimental::RNTupleAttrPendingRange ROOT::Experimental::RNTupleAttrSetWriter::BeginRange()
{
   const auto start = fMainFillContext->GetNEntries();
   return RNTupleAttrPendingRange{start, fFillContext.GetModel().GetModelId()};
}
 
void ROOT::Experimental::RNTupleAttrSetWriter::CommitRange(ROOT::Experimental::RNTupleAttrPendingRange pendingRange,
                                                           REntry &entry)
{
   // NOTE: this has to happen before potentially throwing the exception, otherwise the pending range will log its
   // "was not committed" warning in addition to it.
   // Once the user passed the pending range to this function they already relinquished its ownership, thus we can
   // very well consider it "committed" for error reporting purposes, even if it never ends up actually committed
   // due to exception.
   pendingRange.fWasCommitted = true;
 
   if (pendingRange.GetModelId() != fFillContext.GetModel().GetModelId())
      throw ROOT::RException(R__FAIL("Range passed to CommitRange() of AttributeSet '" + GetDescriptor().GetName() +
                                     "' was not created by it or was already committed."));
 
   // Get current entry number from the writer and use it as end of entry range
   const auto end = fMainFillContext->GetNEntries();
   auto &metaEntry = fFillContext.fModel->GetDefaultEntry();
   R__ASSERT(end >= pendingRange.GetStart());
   *fRangeStartPtr = pendingRange.GetStart();
   *fRangeLenPtr = end - pendingRange.GetStart();
   Internal::RNTupleAttrEntry pair{metaEntry, entry, *fFillContext.fModel};
   fFillContext.FillImpl(pair);
}
 
void ROOT::Experimental::RNTupleAttrSetWriter::CommitRange(ROOT::Experimental::RNTupleAttrPendingRange pendingRange)
{
   CommitRange(std::move(pendingRange), fUserModel->GetDefaultEntry());
}
 
ROOT::Internal::RNTupleLink ROOT::Experimental::RNTupleAttrSetWriter::Commit()
{
   fFillContext.FlushCluster();
   fFillContext.fSink->CommitClusterGroup();
   return fFillContext.fSink->CommitDataset();
}