V8 Project
flags.h
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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 
9 
10 namespace v8 {
11 namespace base {
12 
13 // The Flags class provides a type-safe way of storing OR-combinations of enum
14 // values. The Flags<T, S> class is a template class, where T is an enum type,
15 // and S is the underlying storage type (usually int).
16 //
17 // The traditional C++ approach for storing OR-combinations of enum values is to
18 // use an int or unsigned int variable. The inconvenience with this approach is
19 // that there's no type checking at all; any enum value can be OR'd with any
20 // other enum value and passed on to a function that takes an int or unsigned
21 // int.
22 template <typename T, typename S = int>
23 class Flags FINAL {
24  public:
25  typedef T flag_type;
26  typedef S mask_type;
27 
28  Flags() : mask_(0) {}
29  Flags(flag_type flag) : mask_(flag) {} // NOLINT(runtime/explicit)
30  explicit Flags(mask_type mask) : mask_(mask) {}
31 
32  Flags& operator&=(const Flags& flags) {
33  mask_ &= flags.mask_;
34  return *this;
35  }
36  Flags& operator|=(const Flags& flags) {
37  mask_ |= flags.mask_;
38  return *this;
39  }
40  Flags& operator^=(const Flags& flags) {
41  mask_ ^= flags.mask_;
42  return *this;
43  }
44 
45  Flags operator&(const Flags& flags) const { return Flags(*this) &= flags; }
46  Flags operator|(const Flags& flags) const { return Flags(*this) |= flags; }
47  Flags operator^(const Flags& flags) const { return Flags(*this) ^= flags; }
48 
49  Flags& operator&=(flag_type flag) { return operator&=(Flags(flag)); }
50  Flags& operator|=(flag_type flag) { return operator|=(Flags(flag)); }
51  Flags& operator^=(flag_type flag) { return operator^=(Flags(flag)); }
52 
53  Flags operator&(flag_type flag) const { return operator&(Flags(flag)); }
54  Flags operator|(flag_type flag) const { return operator|(Flags(flag)); }
55  Flags operator^(flag_type flag) const { return operator^(Flags(flag)); }
56 
57  Flags operator~() const { return Flags(~mask_); }
58 
59  operator mask_type() const { return mask_; }
60  bool operator!() const { return !mask_; }
61 
62  private:
64 };
65 
66 
67 #define DEFINE_OPERATORS_FOR_FLAGS(Type) \
68  inline Type operator&(Type::flag_type lhs, \
69  Type::flag_type rhs)ALLOW_UNUSED WARN_UNUSED_RESULT; \
70  inline Type operator&(Type::flag_type lhs, Type::flag_type rhs) { \
71  return Type(lhs) & rhs; \
72  } \
73  inline Type operator&(Type::flag_type lhs, \
74  const Type& rhs)ALLOW_UNUSED WARN_UNUSED_RESULT; \
75  inline Type operator&(Type::flag_type lhs, const Type& rhs) { \
76  return rhs & lhs; \
77  } \
78  inline void operator&(Type::flag_type lhs, Type::mask_type rhs)ALLOW_UNUSED; \
79  inline void operator&(Type::flag_type lhs, Type::mask_type rhs) {} \
80  inline Type operator|(Type::flag_type lhs, Type::flag_type rhs) \
81  ALLOW_UNUSED WARN_UNUSED_RESULT; \
82  inline Type operator|(Type::flag_type lhs, Type::flag_type rhs) { \
83  return Type(lhs) | rhs; \
84  } \
85  inline Type operator|(Type::flag_type lhs, const Type& rhs) \
86  ALLOW_UNUSED WARN_UNUSED_RESULT; \
87  inline Type operator|(Type::flag_type lhs, const Type& rhs) { \
88  return rhs | lhs; \
89  } \
90  inline void operator|(Type::flag_type lhs, Type::mask_type rhs) \
91  ALLOW_UNUSED; \
92  inline void operator|(Type::flag_type lhs, Type::mask_type rhs) {} \
93  inline Type operator^(Type::flag_type lhs, Type::flag_type rhs) \
94  ALLOW_UNUSED WARN_UNUSED_RESULT; \
95  inline Type operator^(Type::flag_type lhs, Type::flag_type rhs) { \
96  return Type(lhs) ^ rhs; \
97  } inline Type operator^(Type::flag_type lhs, const Type& rhs) \
98  ALLOW_UNUSED WARN_UNUSED_RESULT; \
99  inline Type operator^(Type::flag_type lhs, const Type& rhs) { \
100  return rhs ^ lhs; \
101  } inline void operator^(Type::flag_type lhs, Type::mask_type rhs) \
102  ALLOW_UNUSED; \
103  inline void operator^(Type::flag_type lhs, Type::mask_type rhs) {}
104 
105 } // namespace base
106 } // namespace v8
107 
108 #endif // V8_BASE_FLAGS_H_
Flags operator&(const Flags &flags) const
Definition: flags.h:45
Flags & operator&=(flag_type flag)
Definition: flags.h:49
Flags operator|(flag_type flag) const
Definition: flags.h:54
Flags operator^(flag_type flag) const
Definition: flags.h:55
Flags operator&(flag_type flag) const
Definition: flags.h:53
mask_type mask_
Definition: flags.h:63
bool operator!() const
Definition: flags.h:60
Flags & operator^=(const Flags &flags)
Definition: flags.h:40
Flags operator^(const Flags &flags) const
Definition: flags.h:47
Flags(mask_type mask)
Definition: flags.h:30
Flags & operator^=(flag_type flag)
Definition: flags.h:51
Flags & operator&=(const Flags &flags)
Definition: flags.h:32
Flags(flag_type flag)
Definition: flags.h:29
Flags operator|(const Flags &flags) const
Definition: flags.h:46
Flags operator~() const
Definition: flags.h:57
Flags & operator|=(flag_type flag)
Definition: flags.h:50
Flags & operator|=(const Flags &flags)
Definition: flags.h:36
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