js/src/util/EnumFlags.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef util_EnumFlags_h
   8 #define util_EnumFlags_h
   9
  10 #include "mozilla/Attributes.h"
  11
  12 #include <initializer_list>
  13 #include <type_traits>
  14
  15 namespace js {
  16
  17 // Wrapper type for flags fields based on an enum type.
  18 //
  19 // EnumFlags does not (implicitly) convert to/from the underlying integer type.
  20 // That can be supported for specific flags fields by deriving from this class
  21 // and implementing an extra constructor and/or |operator FieldType|.
  22 //
  23 // Note: this type is similar to mfbt/EnumSet.h, but has the same size in debug
  24 // and release builds so is more appropriate for core data structures where we
  25 // don't want this size difference.
  26 template <typename EnumType>
  27 class EnumFlags {
  28  protected:
  29   // Use the enum's underlying type for the flags field. This makes JIT accesses
  30   // more predictable and simplifies the implementation of this class.
  31   static_assert(std::is_enum_v<EnumType>);
  32   using FieldType = std::underlying_type_t<EnumType>;
  33   static_assert(std::is_unsigned_v<FieldType>);
  34
  35   FieldType flags_ = 0;
  36
  37   explicit constexpr EnumFlags(FieldType rawFlags) : flags_(rawFlags) {}
  38
  39  public:
  40   constexpr EnumFlags() = default;
  41
  42   constexpr MOZ_IMPLICIT EnumFlags(std::initializer_list<EnumType> list) {
  43     for (EnumType flag : list) {
  44       setFlag(flag);
  45     }
  46   }
  47
  48   constexpr bool hasFlag(EnumType flag) const {
  49     return flags_ & static_cast<FieldType>(flag);
  50   }
  51   constexpr void setFlag(EnumType flag) {
  52     flags_ |= static_cast<FieldType>(flag);
  53   }
  54   constexpr void clearFlag(EnumType flag) {
  55     flags_ &= ~static_cast<FieldType>(flag);
  56   }
  57   constexpr void setFlag(EnumType flag, bool b) {
  58     if (b) {
  59       setFlag(flag);
  60     } else {
  61       clearFlag(flag);
  62     }
  63   }
  64
  65   constexpr bool hasAnyFlag(const EnumFlags& other) const {
  66     return (flags_ & other.flags_) != 0;
  67   }
  68
  69   constexpr bool isEmpty() const { return flags_ == 0; }
  70
  71   constexpr FieldType toRaw() const { return flags_; }
  72   void setRaw(FieldType flag) { flags_ = flag; }
  73
  74   constexpr bool operator==(const EnumFlags& other) const {
  75     return flags_ == other.flags_;
  76   }
  77   constexpr bool operator!=(const EnumFlags& other) const {
  78     return flags_ != other.flags_;
  79   }
  80 };
  81
  82 }  // namespace js
  83
  84 #endif  // util_EnumFlags_h