1 // Copyright 2014 the V8 project authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef V8_BASE_FLAGS_H_ 6 #define V8_BASE_FLAGS_H_ 7 8 #include <cstddef> 9 10 #include "src/base/compiler-specific.h" 11 12 namespace v8 { 13 namespace base { 14 15 // The Flags class provides a type-safe way of storing OR-combinations of enum 16 // values. The Flags<T, S> class is a template class, where T is an enum type, 17 // and S is the underlying storage type (usually int). 18 // 19 // The traditional C++ approach for storing OR-combinations of enum values is to 20 // use an int or unsigned int variable. The inconvenience with this approach is 21 // that there's no type checking at all; any enum value can be OR'd with any 22 // other enum value and passed on to a function that takes an int or unsigned 23 // int. 24 template <typename T, typename S = int> 25 class Flags final { 26 public: 27 using flag_type = T; 28 using mask_type = S; 29 Flags()30 constexpr Flags() : mask_(0) {} Flags(flag_type flag)31 constexpr Flags(flag_type flag) // NOLINT(runtime/explicit) 32 : mask_(static_cast<S>(flag)) {} Flags(mask_type mask)33 constexpr explicit Flags(mask_type mask) : mask_(static_cast<S>(mask)) {} 34 35 constexpr bool operator==(flag_type flag) const { 36 return mask_ == static_cast<S>(flag); 37 } 38 constexpr bool operator!=(flag_type flag) const { 39 return mask_ != static_cast<S>(flag); 40 } 41 42 Flags& operator&=(const Flags& flags) { 43 mask_ &= flags.mask_; 44 return *this; 45 } 46 Flags& operator|=(const Flags& flags) { 47 mask_ |= flags.mask_; 48 return *this; 49 } 50 Flags& operator^=(const Flags& flags) { 51 mask_ ^= flags.mask_; 52 return *this; 53 } 54 55 constexpr Flags operator&(const Flags& flags) const { 56 return Flags(mask_ & flags.mask_); 57 } 58 constexpr Flags operator|(const Flags& flags) const { 59 return Flags(mask_ | flags.mask_); 60 } 61 constexpr Flags operator^(const Flags& flags) const { 62 return Flags(mask_ ^ flags.mask_); 63 } 64 65 Flags& operator&=(flag_type flag) { return operator&=(Flags(flag)); } 66 Flags& operator|=(flag_type flag) { return operator|=(Flags(flag)); } 67 Flags& operator^=(flag_type flag) { return operator^=(Flags(flag)); } 68 69 constexpr Flags operator&(flag_type flag) const { 70 return operator&(Flags(flag)); 71 } 72 constexpr Flags operator|(flag_type flag) const { 73 return operator|(Flags(flag)); 74 } 75 constexpr Flags operator^(flag_type flag) const { 76 return operator^(Flags(flag)); 77 } 78 79 constexpr Flags operator~() const { return Flags(~mask_); } 80 mask_type()81 constexpr operator mask_type() const { return mask_; } 82 constexpr bool operator!() const { return !mask_; } 83 without(flag_type flag)84 Flags without(flag_type flag) const { return *this & (~Flags(flag)); } 85 hash_value(const Flags & flags)86 friend size_t hash_value(const Flags& flags) { return flags.mask_; } 87 88 private: 89 mask_type mask_; 90 }; 91 92 #define DEFINE_OPERATORS_FOR_FLAGS(Type) \ 93 V8_ALLOW_UNUSED V8_WARN_UNUSED_RESULT inline constexpr Type operator&( \ 94 Type::flag_type lhs, Type::flag_type rhs) { \ 95 return Type(lhs) & rhs; \ 96 } \ 97 V8_ALLOW_UNUSED V8_WARN_UNUSED_RESULT inline constexpr Type operator&( \ 98 Type::flag_type lhs, const Type& rhs) { \ 99 return rhs & lhs; \ 100 } \ 101 V8_ALLOW_UNUSED inline void operator&(Type::flag_type lhs, \ 102 Type::mask_type rhs) {} \ 103 V8_ALLOW_UNUSED V8_WARN_UNUSED_RESULT inline constexpr Type operator|( \ 104 Type::flag_type lhs, Type::flag_type rhs) { \ 105 return Type(lhs) | rhs; \ 106 } \ 107 V8_ALLOW_UNUSED V8_WARN_UNUSED_RESULT inline constexpr Type operator|( \ 108 Type::flag_type lhs, const Type& rhs) { \ 109 return rhs | lhs; \ 110 } \ 111 V8_ALLOW_UNUSED inline void operator|(Type::flag_type lhs, \ 112 Type::mask_type rhs) {} \ 113 V8_ALLOW_UNUSED V8_WARN_UNUSED_RESULT inline constexpr Type operator^( \ 114 Type::flag_type lhs, Type::flag_type rhs) { \ 115 return Type(lhs) ^ rhs; \ 116 } \ 117 V8_ALLOW_UNUSED V8_WARN_UNUSED_RESULT inline constexpr Type operator^( \ 118 Type::flag_type lhs, const Type& rhs) { \ 119 return rhs ^ lhs; \ 120 } \ 121 V8_ALLOW_UNUSED inline void operator^(Type::flag_type lhs, \ 122 Type::mask_type rhs) {} \ 123 V8_ALLOW_UNUSED inline constexpr Type operator~(Type::flag_type val) { \ 124 return ~Type(val); \ 125 } 126 127 } // namespace base 128 } // namespace v8 129 130 #endif // V8_BASE_FLAGS_H_ 131