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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 
8 #include "src/base/compiler-specific.h"
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 
Flags()28   Flags() : mask_(0) {}
Flags(flag_type flag)29   Flags(flag_type flag) : mask_(flag) {}  // NOLINT(runtime/explicit)
Flags(mask_type mask)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 
mask_type()59   operator mask_type() const { return mask_; }
60   bool operator!() const { return !mask_; }
61 
62  private:
63   mask_type mask_;
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_
109