RNTupleAttrUtils.hxx

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/// \file ROOT/RNTupleAttrUtils.hxx
/// \ingroup NTuple
/// \author Giacomo Parolini <giacomo.parolini@cern.ch>
/// \date 2026-03-10
/// \warning This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback
/// is welcome!
 
#ifndef ROOT7_RNTuple_Attr_Utils
#define ROOT7_RNTuple_Attr_Utils
 
#include <cstddef>
#include <cstdint>
 
namespace ROOT::Experimental::Internal::RNTupleAttributes {
 
/*
Attribute RNTuples have a fixed Model schema that looks like this:
 
                +-----------+
                | MetaModel |
                +-----+-----+
                      |
       +--------------+---------------+
       |              |               |
+------+------+ +-----+------+ +------+------+
| _rangeStart | | _rangeLen  | |  _userData  |
+-------------+ +------------+ +------+------+
                                      |
                                +-----+-----+
                                | UserModel |
                                +-----------+
 
Where "_userData" is an untyped record field containing all the user-defined Model's fields
as its children.
 
The order and name of the meta Model's fields is defined by the schema version.
*/
 
inline const std::uint16_t kSchemaVersionMajor = 1;
inline const std::uint16_t kSchemaVersionMinor = 0;
 
enum : std::size_t {
   kMetaFieldIndex_RangeStart,
   kMetaFieldIndex_RangeLen,
   kMetaFieldIndex_UserData,
 
   kMetaFieldIndex_Count
};
inline constexpr const char *kMetaFieldNames[] = {"_rangeStart", "_rangeLen", "_userData"};
static_assert(kMetaFieldIndex_Count == sizeof(kMetaFieldNames) / sizeof(kMetaFieldNames[0]));
 
} // namespace ROOT::Experimental::Internal::RNTupleAttributes
 
#endif