RowView.h

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#ifndef FWCore_SOA_RowView_h
#define FWCore_SOA_RowView_h
// -*- C++ -*-
//
// Package:     FWCore/SOA
// Class  :     RowView
//
//
// Original Author:  Chris Jones
//         Created:  Thu, 24 Aug 2017 16:49:17 GMT
//

// system include files
#include <tuple>
#include <array>

// user include files
#include "FWCore/SOA/interface/tablehelpers.h"
#include "FWCore/SOA/interface/ColumnFillers.h"

// forward declarations

namespace edm {
  namespace soa {

    template <typename... Args>
    class RowView {
      using Layout = std::tuple<Args...>;
      std::array<void const*, sizeof...(Args)> m_values;

    public:
      explicit RowView(std::array<void const*, sizeof...(Args)> const& iValues) : m_values{iValues} {}

      template <typename U>
      typename U::type const& get() const {
        return *(static_cast<typename U::type const*>(columnAddress<U>()));
      }

      template <typename U>
      void const* columnAddress() const {
        return m_values[impl::GetIndex<0, U, Layout>::index];
      }
    };

    template <typename... Args>
    class MutableRowView {
      using Layout = std::tuple<Args...>;
      std::array<void*, sizeof...(Args)> m_values;

    public:
      explicit MutableRowView(std::array<void*, sizeof...(Args)>& iValues) : m_values{iValues} {}

      template <typename U>
      typename U::type& get() {
        return *(static_cast<typename U::type*>(columnAddress<U>()));
      }
      template <typename U>
      typename U::type const& get() const {
        return *(static_cast<typename U::type const*>(columnAddress<U>()));
      }

      template <typename U>
      MutableRowView<Args...>& set(typename U::type const& iValue) {
        get<U>() = iValue;
        return *this;
      }

      template <typename U>
      void* columnAddress() {
        return m_values[impl::GetIndex<0, U, Layout>::index];
      }
      template <typename U>
      void const* columnAddress() const {
        return m_values[impl::GetIndex<0, U, Layout>::index];
      }

      template <typename O>
      void copyValuesFrom(O const& iObj) {
        copyValueFromImpl<0>(iObj);
      }
      template <typename O, typename... CArgs>
      void copyValuesFrom(O const& iObj, ColumnFillers<CArgs...> iFiller) {
        copyValuesUsingFiller<0>(iFiller, iObj, m_values);
      }

    private:
      template <int I, typename O>
      void copyValueFromImpl(O const& iObj) {
        if constexpr (I < sizeof...(Args)) {
          using ColumnType = typename std::tuple_element<I, Layout>::type;
          using Type = typename ColumnType::type;
          auto ptr = static_cast<Type*>(m_values[I]);
          *ptr = value_for_column(iObj, static_cast<ColumnType*>(nullptr));
          copyValueFromImpl<I + 1>(iObj);
        }
      }

      template <int I, typename E, typename F>
      static void copyValuesUsingFiller(F& iFiller, E const& iItem, std::array<void*, sizeof...(Args)>& oValues) {
        if constexpr (I < sizeof...(Args)) {
          using Layout = std::tuple<Args...>;
          using ColumnType = typename std::tuple_element<I, Layout>::type;
          using Type = typename ColumnType::type;
          Type* pElement = static_cast<Type*>(oValues[I]);
          *pElement = iFiller.value(iItem, static_cast<ColumnType*>(nullptr));
          copyValuesUsingFiller<I + 1>(iFiller, iItem, oValues);
        }
      }
    };

  }  // namespace soa
}  // namespace edm

#endif