TableExaminer.h

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#ifndef FWCore_SOA_TableExaminer_h
#define FWCore_SOA_TableExaminer_h
// -*- C++ -*-
//
// Package:     FWCore/SOA
// Class  :     TableExaminer
//
//
// Original Author:  Chris Jones
//         Created:  Mon, 28 Aug 2017 14:22:29 GMT
//

// system include files

// user include files
#include "FWCore/SOA/interface/TableExaminerBase.h"

// forward declarations
namespace edm {
  namespace soa {

    template <typename T>
    class TableExaminer : public TableExaminerBase {
    public:
      explicit TableExaminer(T const* iTable) : m_table(iTable) {}

      TableExaminer(const TableExaminer<T>&) = default;

      TableExaminer<T>& operator=(const TableExaminer<T>&) = default;

      ~TableExaminer() override {}

      // ---------- const member functions ---------------------

      size_t size() const override final { return m_table->size(); }

      void const* columnAddress(unsigned int iColumnIndex) const override final {
        return m_table->columnAddressByIndex(iColumnIndex);
      }

      std::vector<std::type_index> columnTypes() const override final {
        std::vector<std::type_index> returnValue;
        returnValue.reserve(T::kNColumns);
        columnTypesImpl<0, T::kNColumns>(returnValue);
        return returnValue;
      }

      std::vector<std::pair<char const*, std::type_index>> columnDescriptions() const override final {
        std::vector<std::pair<char const*, std::type_index>> returnValue;
        returnValue.reserve(T::kNColumns);
        columnDescImpl<0, T::kNColumns>(returnValue);
        return returnValue;
      }

      const std::type_info* typeID() const override final { return &typeid(T); }

    private:
      template <int I, int S>
      void columnTypesImpl(std::vector<std::type_index>& iV) const {
        if constexpr (I != S) {
          using Layout = typename T::Layout;
          iV.emplace_back(typeid(typename std::tuple_element<I, Layout>::type));
          columnTypesImpl<I + 1, S>(iV);
        }
      }

      template <int I, int S>
      void columnDescImpl(std::vector<std::pair<char const*, std::type_index>>& iV) const {
        if constexpr (I != S) {
          using Layout = typename T::Layout;
          using ColumnType = typename std::tuple_element<I, Layout>::type;
          iV.emplace_back(ColumnType::label(), typeid(typename ColumnType::type));
          columnDescImpl<I + 1, S>(iV);
        }
      }

      // ---------- member data --------------------------------
      T const* m_table;
    };

  }  // namespace soa
}  // namespace edm

#endif