chromium/base/containers/enum_set.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_CONTAINERS_ENUM_SET_H_
#define BASE_CONTAINERS_ENUM_SET_H_

#include <bitset>
#include <cstddef>
#include <initializer_list>
#include <optional>
#include <string>
#include <type_traits>
#include <utility>

#include "base/check.h"
#include "base/check_op.h"
#include "base/memory/raw_ptr.h"
#include "build/build_config.h"

namespace base {

// Forward declarations needed for friend declarations.
template <typename E, E MinEnumValue, E MaxEnumValue>
class EnumSet;

template <typename E, E Min, E Max>
constexpr EnumSet<E, Min, Max> Union(EnumSet<E, Min, Max> set1,
                                     EnumSet<E, Min, Max> set2);

template <typename E, E Min, E Max>
constexpr EnumSet<E, Min, Max> Intersection(EnumSet<E, Min, Max> set1,
                                            EnumSet<E, Min, Max> set2);

template <typename E, E Min, E Max>
constexpr EnumSet<E, Min, Max> Difference(EnumSet<E, Min, Max> set1,
                                          EnumSet<E, Min, Max> set2);

// An EnumSet is a set that can hold enum values between a min and a
// max value (inclusive of both).  It's essentially a wrapper around
// std::bitset<> with stronger type enforcement, more descriptive
// member function names, and an iterator interface.
//
// If you're working with enums with a small number of possible values
// (say, fewer than 64), you can efficiently pass around an EnumSet
// for that enum around by value.

template <typename E, E MinEnumValue, E MaxEnumValue>
class EnumSet { … };

template <typename E, E MinEnumValue, E MaxEnumValue>
const E EnumSet<E, MinEnumValue, MaxEnumValue>::kMinValue;

template <typename E, E MinEnumValue, E MaxEnumValue>
const E EnumSet<E, MinEnumValue, MaxEnumValue>::kMaxValue;

template <typename E, E MinEnumValue, E MaxEnumValue>
const size_t EnumSet<E, MinEnumValue, MaxEnumValue>::kValueCount;

// The usual set operations.

template <typename E, E Min, E Max>
constexpr EnumSet<E, Min, Max> Union(EnumSet<E, Min, Max> set1,
                                     EnumSet<E, Min, Max> set2) { … }

template <typename E, E Min, E Max>
constexpr EnumSet<E, Min, Max> Intersection(EnumSet<E, Min, Max> set1,
                                            EnumSet<E, Min, Max> set2) { … }

template <typename E, E Min, E Max>
constexpr EnumSet<E, Min, Max> Difference(EnumSet<E, Min, Max> set1,
                                          EnumSet<E, Min, Max> set2) { … }

}  // namespace base

#endif  // BASE_CONTAINERS_ENUM_SET_H_