V8 API Reference, 7.2.502.16 (for Deno 0.2.4)
flags.h
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_
Definition: libplatform.h:13