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 typedef T flag_type; 28 typedef S mask_type; 29 30 constexpr Flags() : mask_(0) {} 31 constexpr Flags(flag_type flag) // NOLINT(runtime/explicit) 32 : mask_(static_cast<S>(flag)) {} 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(*this) &= flags; 57 } 58 constexpr Flags operator|(const Flags& flags) const { 59 return Flags(*this) |= flags; 60 } 61 constexpr Flags operator^(const Flags& flags) const { 62 return Flags(*this) ^= flags; 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 81 constexpr operator mask_type() const { return mask_; } 82 constexpr bool operator!() const { return !mask_; } 83 84 friend size_t hash_value(const Flags& flags) { return flags.mask_; } 85 86 private: 87 mask_type mask_; 88 }; 89 90 #define DEFINE_OPERATORS_FOR_FLAGS(Type) \ 91 inline Type operator&( \ 92 Type::flag_type lhs, \ 93 Type::flag_type rhs)ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT; \ 94 inline Type operator&(Type::flag_type lhs, Type::flag_type rhs) { \ 95 return Type(lhs) & rhs; \ 96 } \ 97 inline Type operator&( \ 98 Type::flag_type lhs, \ 99 const Type& rhs)ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT; \ 100 inline Type operator&(Type::flag_type lhs, const Type& rhs) { \ 101 return rhs & lhs; \ 102 } \ 103 inline void operator&(Type::flag_type lhs, \ 104 Type::mask_type rhs)ALLOW_UNUSED_TYPE; \ 105 inline void operator&(Type::flag_type lhs, Type::mask_type rhs) {} \ 106 inline Type operator|(Type::flag_type lhs, Type::flag_type rhs) \ 107 ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT; \ 108 inline Type operator|(Type::flag_type lhs, Type::flag_type rhs) { \ 109 return Type(lhs) | rhs; \ 110 } \ 111 inline Type operator|(Type::flag_type lhs, const Type& rhs) \ 112 ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT; \ 113 inline Type operator|(Type::flag_type lhs, const Type& rhs) { \ 114 return rhs | lhs; \ 115 } \ 116 inline void operator|(Type::flag_type lhs, Type::mask_type rhs) \ 117 ALLOW_UNUSED_TYPE; \ 118 inline void operator|(Type::flag_type lhs, Type::mask_type rhs) {} \ 119 inline Type operator^(Type::flag_type lhs, Type::flag_type rhs) \ 120 ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT; \ 121 inline Type operator^(Type::flag_type lhs, Type::flag_type rhs) { \ 122 return Type(lhs) ^ rhs; \ 123 } \ 124 inline Type operator^(Type::flag_type lhs, const Type& rhs) \ 125 ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT; \ 126 inline Type operator^(Type::flag_type lhs, const Type& rhs) { \ 127 return rhs ^ lhs; \ 128 } \ 129 inline void operator^(Type::flag_type lhs, Type::mask_type rhs) \ 130 ALLOW_UNUSED_TYPE; \ 131 inline void operator^(Type::flag_type lhs, Type::mask_type rhs) {} \ 132 inline Type operator~(Type::flag_type val)ALLOW_UNUSED_TYPE; \ 133 inline Type operator~(Type::flag_type val) { return ~Type(val); } 134 135 } // namespace base 136 } // namespace v8 137 138 #endif // V8_BASE_FLAGS_H_ 139
