magic_enum_fuse.hpp

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//  __  __             _        ______                          _____
// |  \/  |           (_)      |  ____|                        / ____|_     _
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//                __/ | https://github.com/Neargye/magic_enum
//               |___/  version 0.9.7
//
// Licensed under the MIT License <http://opensource.org/licenses/MIT>.
// SPDX-License-Identifier: MIT
// Copyright (c) 2019 - 2024 Daniil Goncharov <neargye@gmail.com>.
//
// Permission is hereby  granted, free of charge, to any  person obtaining a copy
// of this software and associated  documentation files (the "Software"), to deal
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#ifndef NEARGYE_MAGIC_ENUM_FUSE_HPP
#define NEARGYE_MAGIC_ENUM_FUSE_HPP
 
#include "magic_enum.hpp"
 
namespace magic_enum {
 
namespace detail {
 
template <typename E>
constexpr optional<std::uintmax_t> fuse_one_enum(optional<std::uintmax_t> hash, E value) noexcept {
  if (hash) {
    if (const auto index = enum_index(value)) {
      return (*hash << log2((enum_count<E>() << 1) - 1)) | *index;
    }
  }
  return {};
}
 
template <typename E>
constexpr optional<std::uintmax_t> fuse_enum(E value) noexcept {
  return fuse_one_enum(0, value);
}
 
template <typename E, typename... Es>
constexpr optional<std::uintmax_t> fuse_enum(E head, Es... tail) noexcept {
  return fuse_one_enum(fuse_enum(tail...), head);
}
 
template <typename... Es>
constexpr auto typesafe_fuse_enum(Es... values) noexcept {
  enum class enum_fuse_t : std::uintmax_t;
  const auto fuse = fuse_enum(values...);
  if (fuse) {
    return optional<enum_fuse_t>{static_cast<enum_fuse_t>(*fuse)};
  }
  return optional<enum_fuse_t>{};
}
 
} // namespace magic_enum::detail
 
// Returns a bijective mix of several enum values. This can be used to emulate 2D switch/case statements.
template <typename... Es>
[[nodiscard]] constexpr auto enum_fuse(Es... values) noexcept {
  static_assert((std::is_enum_v<std::decay_t<Es>> && ...), "magic_enum::enum_fuse requires enum type.");
  static_assert(sizeof...(Es) >= 2, "magic_enum::enum_fuse requires at least 2 values.");
  static_assert((detail::log2(enum_count<std::decay_t<Es>>() + 1) + ...) <= (sizeof(std::uintmax_t) * 8), "magic_enum::enum_fuse does not work for large enums");
#if defined(MAGIC_ENUM_NO_TYPESAFE_ENUM_FUSE)
  const auto fuse = detail::fuse_enum<std::decay_t<Es>...>(values...);
#else
  const auto fuse = detail::typesafe_fuse_enum<std::decay_t<Es>...>(values...);
#endif
  return MAGIC_ENUM_ASSERT(fuse), fuse;
}
 
} // namespace magic_enum
 
#endif // NEARGYE_MAGIC_ENUM_FUSE_HPP