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 Flags() : mask_(0) {} 31 Flags(flag_type flag) // NOLINT(runtime/explicit) 32 : mask_(static_cast<S>(flag)) {} 33 explicit Flags(mask_type mask) : mask_(static_cast<S>(mask)) {} 34 35 bool operator==(flag_type flag) const { 36 return mask_ == static_cast<S>(flag); 37 } 38 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 Flags operator&(const Flags& flags) const { return Flags(*this) &= flags; } 56 Flags operator|(const Flags& flags) const { return Flags(*this) |= flags; } 57 Flags operator^(const Flags& flags) const { return Flags(*this) ^= flags; } 58 59 Flags& operator&=(flag_type flag) { return operator&=(Flags(flag)); } 60 Flags& operator|=(flag_type flag) { return operator|=(Flags(flag)); } 61 Flags& operator^=(flag_type flag) { return operator^=(Flags(flag)); } 62 63 Flags operator&(flag_type flag) const { return operator&(Flags(flag)); } 64 Flags operator|(flag_type flag) const { return operator|(Flags(flag)); } 65 Flags operator^(flag_type flag) const { return operator^(Flags(flag)); } 66 67 Flags operator~() const { return Flags(~mask_); } 68 69 operator mask_type() const { return mask_; } 70 bool operator!() const { return !mask_; } 71 72 friend size_t hash_value(const Flags& flags) { return flags.mask_; } 73 74 private: 75 mask_type mask_; 76 }; 77 78 79 #define DEFINE_OPERATORS_FOR_FLAGS(Type) \ 80 inline Type operator&( \ 81 Type::flag_type lhs, \ 82 Type::flag_type rhs)ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT; \ 83 inline Type operator&(Type::flag_type lhs, Type::flag_type rhs) { \ 84 return Type(lhs) & rhs; \ 85 } \ 86 inline Type operator&(Type::flag_type lhs, \ 87 const Type& rhs)ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT; \ 88 inline Type operator&(Type::flag_type lhs, const Type& rhs) { \ 89 return rhs & lhs; \ 90 } \ 91 inline void operator&(Type::flag_type lhs, \ 92 Type::mask_type rhs)ALLOW_UNUSED_TYPE; \ 93 inline void operator&(Type::flag_type lhs, Type::mask_type rhs) {} \ 94 inline Type operator|(Type::flag_type lhs, Type::flag_type rhs) \ 95 ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT; \ 96 inline Type operator|(Type::flag_type lhs, Type::flag_type rhs) { \ 97 return Type(lhs) | rhs; \ 98 } \ 99 inline Type operator|(Type::flag_type lhs, const Type& rhs) \ 100 ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT; \ 101 inline Type operator|(Type::flag_type lhs, const Type& rhs) { \ 102 return rhs | lhs; \ 103 } \ 104 inline void operator|(Type::flag_type lhs, Type::mask_type rhs) \ 105 ALLOW_UNUSED_TYPE; \ 106 inline void operator|(Type::flag_type lhs, Type::mask_type rhs) {} \ 107 inline Type operator^(Type::flag_type lhs, Type::flag_type rhs) \ 108 ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT; \ 109 inline Type operator^(Type::flag_type lhs, Type::flag_type rhs) { \ 110 return Type(lhs) ^ rhs; \ 111 } inline Type \ 112 operator^(Type::flag_type lhs, const Type& rhs) \ 113 ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT; \ 114 inline Type operator^(Type::flag_type lhs, const Type& rhs) { \ 115 return rhs ^ lhs; \ 116 } inline void \ 117 operator^(Type::flag_type lhs, Type::mask_type rhs) ALLOW_UNUSED_TYPE; \ 118 inline void operator^(Type::flag_type lhs, Type::mask_type rhs) { \ 119 } inline Type \ 120 operator~(Type::flag_type val)ALLOW_UNUSED_TYPE; \ 121 inline Type operator~(Type::flag_type val) { return ~Type(val); } 122 123 } // namespace base 124 } // namespace v8 125 126 #endif // V8_BASE_FLAGS_H_ 127
