ColumnarDef.h

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef COLUMNAR_CORE_COLUMNAR_DEF_H
#define COLUMNAR_CORE_COLUMNAR_DEF_H
 
#include <cstdint>
#include <stdexcept>
 
namespace columnar
{
  // This checks that COLUMNAR_DEFAULT_ACCESS_MODE is indeed defined, plus makes it
  // available for use with `if constexpr`.
  constexpr unsigned columnarAccessMode = COLUMNAR_DEFAULT_ACCESS_MODE;
 
  struct ColumnarModeXAOD
  {
    static constexpr bool isXAOD = true;

    static constexpr bool inPlaceReplace = true;
  };
 
 
 
  struct ColumnarModeArray
  {
    static constexpr bool isXAOD = false;

    static constexpr bool inPlaceReplace = false;
 


    using LinkIndexType = std::size_t;

    static constexpr LinkIndexType invalidLinkValue = static_cast<LinkIndexType>(-1);

    static constexpr unsigned linkKeyBits = 8;

    using LinkKeyType = std::uint8_t;

    static_assert (linkKeyBits <= 8 * sizeof(LinkKeyType), "Link key bits exceed key type size");
    static_assert (linkKeyBits < 8 * sizeof(LinkIndexType), "Link key bits exceed link type size");
    static constexpr unsigned linkIndexBits = 8 * sizeof(LinkIndexType) - linkKeyBits;
    static constexpr LinkIndexType linkIndexMask = (static_cast<LinkIndexType>(1) << linkIndexBits) - 1;

    static inline LinkKeyType getLinkKey (LinkIndexType link) {
      return link >> linkIndexBits;
    }

    static inline LinkIndexType getLinkIndex (LinkIndexType link) {
      return link & linkIndexMask;
    }

    static inline LinkIndexType mergeLinkKeyIndex (LinkIndexType key, LinkIndexType index) {
      if (key >= (static_cast<LinkIndexType>(1) << linkKeyBits))
        throw std::runtime_error ("link key too large to fit in link: " + std::to_string(key));
      if (index & ~linkIndexMask)
        throw std::runtime_error ("index too large to fit in link: " + std::to_string(index));
      return index | (key << linkIndexBits);
    }
  };
 
 
 
#if COLUMNAR_DEFAULT_ACCESS_MODE == 0
  using ColumnarModeDefault = ColumnarModeXAOD;
#elif COLUMNAR_DEFAULT_ACCESS_MODE == 2
  using ColumnarModeDefault = ColumnarModeArray;
#else
  #error "COLUMNAR_DEFAULT_ACCESS_MODE must be 0 or 2"
#endif
}
 
#endif