[ntuple] Add GetClusterBoundaries as a friend to RNTupleDS

Author: siliataider

tree/dataframe/inc/ROOT/RNTupleDS.hxx

@@ -63,8 +63,16 @@ class RFieldBase;
 class RDataFrame;
 class RNTuple;
 } // namespace ROOT
+namespace ROOT::Detail::RDF {
+class RNodeBase;
+}
+namespace ROOT::RDF {
+template <typename T>
+class RInterface;
+}
 namespace ROOT::Internal::RDF {
 class RNTupleColumnReader;
+std::vector<std::pair<ULong64_t, ULong64_t>> GetClusterBoundaries(const ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase> &node);
 }
 namespace ROOT::Internal {
 class RPageSource;
@@ -206,6 +214,8 @@ class RNTupleDS final : public ROOT::RDF::RDataSource {
                                                             const std::vector<std::string> &fileNames,
                                                             const std::pair<ULong64_t, ULong64_t> &range);
 
+   friend std::vector<std::pair<ULong64_t, ULong64_t>> ROOT::Internal::RDF::GetClusterBoundaries(const ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase> &node);
+
    explicit RNTupleDS(std::string_view ntupleName, const std::vector<std::string> &fileNames,
                       const std::pair<ULong64_t, ULong64_t> &range);