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
12namespace v8 {
13namespace 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.
24template <typename T, typename S = int>
25class 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