EnumFlags.h

// Copyright (c) Facebook, Inc. and its affiliates.
//
// This source code is licensed under the MIT license found in the
// LICENSE file in the root directory of this source tree.

#pragma once

#include "impl/EnumFlagsDetails.h"

/* MY_ENUMFLAGS_DEF(NAME, UINT_TYPE, ARGS)

  Enum flags type definition. Can be in global, and namespace scope only. See
  MY_ENUMFLAGS below for details. */
#define MY_ENUMFLAGS_DEF(NAME, UINT_TYPE, ...) \
  MY_ENUMFLAGS_DEF_IMPL(NAME, UINT_TYPE, __VA_ARGS__)

/* MY_ENUMFLAGS_ALIAS(NAME)

  Enum type alias. Can be in any scope. See MY_ENUMFLAGS for details. */
#define MY_ENUMFLAGS_ALIAS(NAME) using NAME = enum_wrapper_::NAME##Impl

/* MY_ENUMFLAGS(NAME, UINT_TYPE, ARGS)

  Enum flag type. Can be in global, and namespace scope only.

      NAME:      Name of the enum flag class.
      UINT_TYPE: unsigned integral type.
      ARGS:      Tuple of enums, such as (foo, bar, da).

  For example ``MY_ENUMFLAGS(MyFlags, uint32_t, (foo, bar, daz));`` defines an
  enum class

    enum class MyFlags : uint32_t {
      none = 0,
      foo = 1,
      bar = 2,
      daz = 4
    };

  with the following free functions:

    // Bitwise or
    MyFlags operator|(MyFlags left, MyFlags right);

    // Bitwise and
    MyFlags operator&(MyFlags left, MyFlags right);

    // Sets corresponding bit to 1, if string is single flag (i.e. "foo", "bar"
    // or "daz"). Returns false otherwise.
    bool trySetFlagFromString(MyFlags& value, const std::string& str);

    // Return true if ``value`` contains all flags in ``mask``.
    bool hasMask(MyFlags value, MyFlags mask);

    // Enables bits in mask.
    void setMask(MyFlags& value, MyFlags mask);

    // Clear bits in mask.
    void clearMask(MyFlags& value, MyFlags mask);

    // Toggle bits.
    void toggleMask(MyFlags& value, MyFlags mask);

    // Returns true if value is a single flag (i.e. Foo::foo, Foo::bar or
    // Foo::daz)
    bool isSingleFlag(MyFlags value);

    // Returns string representation of enabled flags
    // (e.g. {"foo", "bar"} for `MyFlags::foo | MyFlags::bar')
    std::vector<std::string> toStrings(MyFlags value);

    // Return pretty string representation
    // (e.g. "{bar (=2), daz (=4)}" for `MyFlags::bar | MyFlags::daz').
    std::string toPretty(MyFlags value);

    // Returns number of flags (i.e. 3).
    constexpr size_t getCount(MyFlags) {
      return 3u;
    }

    // Returns array of names:
    std::array<string_view, 3> getNames(MyFlags) {
      return {"foo", "bar", "daz"};
    }

    // Return string of names:
    constexpr string_view getStringOfNames(MyFlags) {
      return "{foo, bar, daz}";
    }

    // Returns array of values:
    constexpr std::array<uint32_t, 3u> getValues(MyFlags) {
      return {1, 2, 4};
    }

    string_view getTypeName(MyFlags) {
      return "MyFlags";
    }

   // Note: When adding new flags to an exisiting enum, we want to add such flag
   // at the end.

    MY_ENUMFLAGS(MyFlags, uint32_t, (foo, bar));

      generates

    enum class MyFlags : uint32_t {
      none = 0,
      foo = 1,
      bar = 2
    };


    Now adding "daz" to the end, we get


    MY_ENUMFLAGS(MyFlags, uint32_t, (foo, bar, daz));

      which generates

    enum class MyFlags : uint32_t {
      none = 0,
      foo = 1,
      bar = 2,
      daz = 4
    };

    And hence the order of exiting flags (foo, bar) is respected and their
    values do not change.
*/
#define MY_ENUMFLAGS(NAME, UINT_TYPE, ...)       \
  MY_ENUMFLAGS_DEF(NAME, UINT_TYPE, __VA_ARGS__) \
  MY_ENUMFLAGS_ALIAS(NAME)