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FlagsShim.h (2870B)

      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_UTIL_FLAGS_H_
      6 #define V8_UTIL_FLAGS_H_
      7 
      8 // Origin:
      9 // https://github.com/v8/v8/blob/1bafcc6b999b23ea1d394f5d267a08183e3c4e19/src/base/flags.h#L15-L90
     10 
     11 namespace v8 {
     12 namespace base {
     13 
     14 // The Flags class provides a type-safe way of storing OR-combinations of enum
     15 // values. The Flags<T, S> class is a template class, where T is an enum type,
     16 // and S is the underlying storage type (usually int).
     17 //
     18 // The traditional C++ approach for storing OR-combinations of enum values is to
     19 // use an int or unsigned int variable. The inconvenience with this approach is
     20 // that there's no type checking at all; any enum value can be OR'd with any
     21 // other enum value and passed on to a function that takes an int or unsigned
     22 // int.
     23 template <typename T, typename S = int>
     24 class Flags final {
     25 public:
     26  using flag_type = T;
     27  using mask_type = S;
     28 
     29  constexpr Flags() : mask_(0) {}
     30  constexpr Flags(flag_type flag) : mask_(static_cast<S>(flag)) {}
     31  constexpr explicit Flags(mask_type mask) : mask_(static_cast<S>(mask)) {}
     32 
     33  constexpr bool operator==(flag_type flag) const {
     34    return mask_ == static_cast<S>(flag);
     35  }
     36  constexpr bool operator!=(flag_type flag) const {
     37    return mask_ != static_cast<S>(flag);
     38  }
     39 
     40  Flags& operator&=(const Flags& flags) {
     41    mask_ &= flags.mask_;
     42    return *this;
     43  }
     44  Flags& operator|=(const Flags& flags) {
     45    mask_ |= flags.mask_;
     46    return *this;
     47  }
     48  Flags& operator^=(const Flags& flags) {
     49    mask_ ^= flags.mask_;
     50    return *this;
     51  }
     52 
     53  constexpr Flags operator&(const Flags& flags) const {
     54    return Flags(mask_ & flags.mask_);
     55  }
     56  constexpr Flags operator|(const Flags& flags) const {
     57    return Flags(mask_ | flags.mask_);
     58  }
     59  constexpr Flags operator^(const Flags& flags) const {
     60    return Flags(mask_ ^ flags.mask_);
     61  }
     62 
     63  Flags& operator&=(flag_type flag) { return operator&=(Flags(flag)); }
     64  Flags& operator|=(flag_type flag) { return operator|=(Flags(flag)); }
     65  Flags& operator^=(flag_type flag) { return operator^=(Flags(flag)); }
     66 
     67  constexpr Flags operator&(flag_type flag) const {
     68    return operator&(Flags(flag));
     69  }
     70  constexpr Flags operator|(flag_type flag) const {
     71    return operator|(Flags(flag));
     72  }
     73  constexpr Flags operator^(flag_type flag) const {
     74    return operator^(Flags(flag));
     75  }
     76 
     77  constexpr Flags operator~() const { return Flags(~mask_); }
     78 
     79  constexpr operator mask_type() const { return mask_; }
     80  constexpr bool operator!() const { return !mask_; }
     81 
     82  Flags without(flag_type flag) { return *this & (~Flags(flag)); }
     83 
     84  friend size_t hash_value(const Flags& flags) { return flags.mask_; }
     85 
     86 private:
     87  mask_type mask_;
     88 };
     89 
     90 }  // namespace base
     91 }  // namespace v8
     92 
     93 #endif  // V8_UTIL_FLAG_H_