Duckstation/src/common/dimensional_array.h

// Sourced from https://github.com/BreadFish64/ScaleFish/blob/master/common/dimensional_array.hpp
// Copyright (c) 2020 BreadFish64
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#pragma once

#include <array>
#include <cstdint>
#include <type_traits>

namespace detail {
template<typename T, std::size_t rank, std::size_t... sizes>
struct DimensionalArrayExplicitRank;

// Workaround for VC2017
#if defined(_MSC_VER) && _MSC_VER < 1920

template<std::size_t rank, std::size_t... sizes>
struct GetRankSize
{
  static constexpr std::size_t size_array[] = {sizes...};
  static constexpr std::size_t value = size_array[rank - 1];
};

template<typename T, std::size_t rank, std::size_t... sizes>
using GetArrayImplType =
  std::array<std::conditional_t<rank == 1, T, DimensionalArrayExplicitRank<T, rank - 1, sizes...>>,
             GetRankSize<rank, sizes...>::value>;

#else

template<std::size_t rank, std::size_t... sizes>
constexpr std::size_t GetRankSize()
{
  constexpr std::size_t size_array[] = {sizes...};
  return size_array[rank - 1];
}

template<typename T, std::size_t rank, std::size_t... sizes>
using GetArrayImplType =
  std::array<std::conditional_t<rank == 1, T, DimensionalArrayExplicitRank<T, rank - 1, sizes...>>,
             GetRankSize<rank, sizes...>()>;

#endif

template<typename T, std::size_t rank_param, std::size_t... sizes>
struct DimensionalArrayExplicitRank : public GetArrayImplType<T, rank_param, sizes...>
{
  static constexpr std::size_t rank = rank_param;
  static_assert(rank > 0, "Attempted to create dimensional array with rank less than 1");
  using ArrayImplType = GetArrayImplType<T, rank, sizes...>;
  using ArrayImplType::ArrayImplType;

  template<typename Callable>
  void enumerate(const Callable& f)
  {
    for (auto& it : *this)
    {
      if constexpr (rank == 1)
        f(it);
      else
        it.enumerate(f);
    }
  }

  template<typename Callable>
  void enumerate(const Callable& f) const
  {
    for (const auto& it : *this)
    {
      if constexpr (rank == 1)
        f(it);
      else
        it.enumerate(f);
    }
  }
};
} // namespace detail

template<typename T, std::size_t... sizes>
using DimensionalArray = detail::DimensionalArrayExplicitRank<T, sizeof...(sizes), sizes...>;