ydb/contrib/restricted/magic_enum

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|_|  |_|\__,_|\__, |_|\___| |______|_| |_|\__,_|_| |_| |_|  \_____|
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Magic Enum C++

Header-only C++17 library provides static reflection for enums, work with any enum type without any macro or boilerplate code.

• enum_cast obtains enum value from string or integer.
• enum_value returns enum value at specified index.
• enum_values obtains enum value sequence.
• enum_count returns number of enum values.
• enum_integer obtains integer value from enum value.
• enum_name returns name from enum value.
• enum_names obtains string enum name sequence.
• enum_entries obtains pair (value enum, string enum name) sequence.
• enum_index obtains index in enum value sequence from enum value.
• enum_contains checks whether enum contains enumerator with such value.
• enum_type_name returns name of enum type.
• is_unscoped_enum checks whether type is an Unscoped enumeration.
• is_scoped_enum checks whether type is an Scoped enumeration.
• underlying_type improved UB-free "SFINAE-friendly" underlying_type.
• ostream_operators ostream operators for enums.
• bitwise_operators bitwise operators for enums.

Documentation

• Reference
• Limitations
• Integration

Features

• C++17
• Header-only
• Dependency-free
• Compile-time
• Enum to string
• String to enum
• Iterating over enum

Examples

// For example color enum.
enum class Color { RED = 2, BLUE = 4, GREEN = 8 };

• Enum value to string

  Color color = Color::RED;
  auto color_name = magic_enum::enum_name(color);
  // color_name -> "RED"
  

• String to enum value

  std::string color_name{"GREEN"};
  auto color = magic_enum::enum_cast<Color>(color_name);
  if (color.has_value()) {
  // color.value() -> Color::GREEN
  }
  

• Integer to enum value

  int color_integer = 2;
  auto color = magic_enum::enum_cast<Color>(color_integer);
  if (color.has_value()) {
  // color.value() -> Color::RED
  }
  

• Indexed access to enum value

  std::size_t i = 1;
  Color color = magic_enum::enum_value<Color>(i);
  // color -> Color::BLUE
  

• Enum value sequence

  constexpr auto& colors = magic_enum::enum_values<Color>();
  // colors -> {Color::RED, Color::BLUE, Color::GREEN}
  // colors[0] -> Color::RED
  

• Number of enum elements

  constexpr std::size_t color_count = magic_enum::enum_count<Color>();
  // color_count -> 3
  

• Enum value to integer

  Color color = Color::RED;
  auto color_integer = magic_enum::enum_integer(color);
  // color -> 2
  

• Enum names sequence

  constexpr auto& color_names = magic_enum::enum_names<Color>();
  // color_names -> {"RED", "BLUE", "GREEN"}
  // color_names[0] -> "RED"
  

• Enum entries sequence

  constexpr auto& color_entries = magic_enum::enum_entries<Color>();
  // color_entries -> {{Color::RED, "RED"}, {Color::BLUE, "BLUE"}, {Color::GREEN, "GREEN"}}
  // color_entries[0].first -> Color::RED
  // color_entries[0].second -> "RED"
  

• Ostream operator for enum

  using namespace magic_enum::ostream_operators; // out-of-the-box ostream operators for enums.
  Color color = Color::BLUE;
  std::cout << color << std::endl; // "BLUE"
  

• Bitwise operator for enum

  enum class Flags { A = 1 << 0, B = 1 << 1, C = 1 << 2, D = 1 << 3 };
  using namespace magic_enum::bitwise_operators; // out-of-the-box bitwise operators for enums.
  // Support operators: ~, |, &, ^, |=, &=, ^=.
  Flags flags = Flags::A | Flags::B & ~Flags::C;
  

• Checks whether type is an Unscoped enumeration.

  enum color { red, green, blue };
  enum class direction { left, right };
  
  magic_enum::is_unscoped_enum<color>::value -> true
  magic_enum::is_unscoped_enum<direction>::value -> false
  magic_enum::is_unscoped_enum<int>::value -> false
  
  // Helper variable template.
  magic_enum::is_unscoped_enum_v<color> -> true
  

• Checks whether type is an Scoped enumeration.

  enum color { red, green, blue };
  enum class direction { left, right };
  
  magic_enum::is_scoped_enum<color>::value -> false
  magic_enum::is_scoped_enum<direction>::value -> true
  magic_enum::is_scoped_enum<int>::value -> false
  
  // Helper variable template.
  magic_enum::is_scoped_enum_v<direction> -> true
  

• Static storage enum variable to string This version is much lighter on the compile times and is not restricted to the enum_range limitation.

  constexpr Color color = Color::BLUE;
  constexpr auto color_name = magic_enum::enum_name<color>();
  // color_name -> "BLUE"
  

Remarks

• magic_enum does not pretend to be a silver bullet for reflection for enums, it was originally designed for small enum.

• Before use, read the limitations of functionality.

• For the small enum use the API from the namespace magic_enum, and for enum-flags use the API from the namespace magic_enum::flags.

Integration

• You should add the required file magic_enum.hpp.

• If you are using vcpkg on your project for external dependencies, then you can use the magic-enum package.

• If you are using Conan to manage your dependencies, merely add magic_enum/x.y.z to your conan's requires, where x.y.z is the release version you want to use.

• If you are using Build2 to build and manage your dependencies, add depends: magic_enum ^x.y.z to the manifest file where x.y.z is the release version you want to use. You can then import the target using magic_enum%lib{magic_enum}.

• Alternatively, you can use something like CPM which is based on CMake's Fetch_Content module.

  CPMAddPackage(
    NAME magic_enum
    GITHUB_REPOSITORY Neargye/magic_enum
    GIT_TAG x.y.z # Where `x.y.z` is the release version you want to use.
  )
  

• Bazel is also supported, simply add to your WORKSPACE file:

  http_archive(
    name = "magic_enum",
    strip_prefix = "magic_enum-<commit>",
    urls = ["https://github.com/Neargye/magic_enum/archive/<commit>.zip"],
  )
  

To use bazel inside the repository it's possible to do:

  bazel build //...
  bazel test //...
  bazel run //:example

(Note that you must use a supported compiler or specify it with export CC= <compiler>.)

Compiler compatibility

• Clang/LLVM >= 5
• MSVC++ >= 14.11 / Visual Studio >= 2017
• Xcode >= 10
• GCC >= 9
• MinGW >= 9

Licensed under the MIT License