Add factory method for CSV DS

tree/treeplayer/inc/ROOT/TCsvDS.hxx

 #ifndef ROOT_TCSVTDS
 #define ROOT_TCSVTDS
 
+#include "ROOT/TDataFrame.hxx"
 #include "ROOT/TDataSource.hxx"
 
 #include <map>
@@ -47,6 +48,8 @@ public:
    void SetNSlots(unsigned int nSlots);
 };
 
+TDataFrame MakeCsvDataFrame(std::string_view fileName, bool readHeaders = true, char delimiter = ',');
+
 } // ns TDF
 } // ns Experimental
 } // ns ROOT

tree/treeplayer/src/TCsvDS.cxx

+#include <ROOT/RMakeUnique.hxx>
 #include <ROOT/TCsvDS.hxx>
 #include <ROOT/TDFUtils.hxx>
 #include <ROOT/TSeq.hxx>
@@ -252,6 +253,12 @@ void TCsvDS::SetNSlots(unsigned int nSlots)
    fEntryRanges.back().second += remainder;
 }
 
+TDataFrame MakeCsvDataFrame(std::string_view fileName, bool readHeaders, char delimiter)
+{
+   ROOT::Experimental::TDataFrame tdf(std::make_unique<TCsvDS>(fileName, readHeaders, delimiter));
+   return tdf;
+}
+
 } // ns TDF
 } // ns Experimental
 } // ns ROOT