text: // Copyright 2014 the V8 project authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef V8_BASE_FLAGS_H_
  #define V8_BASE_FLAGS_H_
  
  #include "src/base/compiler-specific.h"
  
  namespace v8 {
  namespace base {
  
  // The Flags class provides a type-safe way of storing OR-combinations of enum
  // values. The Flags<T, S> class is a template class, where T is an enum type,
  // and S is the underlying storage type (usually int).
  //
  // The traditional C++ approach for storing OR-combinations of enum values is to
  // use an int or unsigned int variable. The inconvenience with this approach is
  // that there's no type checking at all; any enum value can be OR'd with any
  // other enum value and passed on to a function that takes an int or unsigned
  // int.
  template <typename T, typename S = int>
  class Flags FINAL {
   public:
    typedef T flag_type;
    typedef S mask_type;
  
    Flags() : mask_(0) {}
    Flags(flag_type flag)  // NOLINT(runtime/explicit)
        : mask_(static_cast<S>(flag)) {}
    explicit Flags(mask_type mask) : mask_(static_cast<S>(mask)) {}
  
    Flags& operator&=(const Flags& flags) {
      mask_ &= flags.mask_;
      return *this;
    }
    Flags& operator|=(const Flags& flags) {
      mask_ |= flags.mask_;
      return *this;
    }
    Flags& operator^=(const Flags& flags) {
      mask_ ^= flags.mask_;
      return *this;
    }
  
    Flags operator&(const Flags& flags) const { return Flags(*this) &= flags; }
    Flags operator|(const Flags& flags) const { return Flags(*this) |= flags; }
    Flags operator^(const Flags& flags) const { return Flags(*this) ^= flags; }
  
    Flags& operator&=(flag_type flag) { return operator&=(Flags(flag)); }
    Flags& operator|=(flag_type flag) { return operator|=(Flags(flag)); }
    Flags& operator^=(flag_type flag) { return operator^=(Flags(flag)); }
  
    Flags operator&(flag_type flag) const { return operator&(Flags(flag)); }
    Flags operator|(flag_type flag) const { return operator|(Flags(flag)); }
    Flags operator^(flag_type flag) const { return operator^(Flags(flag)); }
  
    Flags operator~() const { return Flags(~mask_); }
  
    operator mask_type() const { return mask_; }
    bool operator!() const { return !mask_; }
  
   private:
    mask_type mask_;
  };
  
  
  #define DEFINE_OPERATORS_FOR_FLAGS(Type)                                      \
    inline Type operator&(                                                      \
        Type::flag_type lhs,                                                    \
        Type::flag_type rhs)ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT;               \
    inline Type operator&(Type::flag_type lhs, Type::flag_type rhs) {           \
      return Type(lhs) & rhs;                                                   \
    }                                                                           \
    inline Type operator&(Type::flag_type lhs,                                  \
                          const Type& rhs)ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT; \
    inline Type operator&(Type::flag_type lhs, const Type& rhs) {               \
      return rhs & lhs;                                                         \
    }                                                                           \
    inline void operator&(Type::flag_type lhs,                                  \
                          Type::mask_type rhs)ALLOW_UNUSED_TYPE;                \
    inline void operator&(Type::flag_type lhs, Type::mask_type rhs) {}          \
    inline Type operator|(Type::flag_type lhs, Type::flag_type rhs)             \
        ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT;                                   \
    inline Type operator|(Type::flag_type lhs, Type::flag_type rhs) {           \
      return Type(lhs) | rhs;                                                   \
    }                                                                           \
    inline Type operator|(Type::flag_type lhs, const Type& rhs)                 \
        ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT;                                   \
    inline Type operator|(Type::flag_type lhs, const Type& rhs) {               \
      return rhs | lhs;                                                         \
    }                                                                           \
    inline void operator|(Type::flag_type lhs, Type::mask_type rhs)             \
        ALLOW_UNUSED_TYPE;                                                      \
    inline void operator|(Type::flag_type lhs, Type::mask_type rhs) {}          \
    inline Type operator^(Type::flag_type lhs, Type::flag_type rhs)             \
        ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT;                                   \
    inline Type operator^(Type::flag_type lhs, Type::flag_type rhs) {           \
      return Type(lhs) ^ rhs;                                                   \
    } inline Type operator^(Type::flag_type lhs, const Type& rhs)               \
        ALLOW_UNUSED_TYPE WARN_UNUSED_RESULT;                                   \
    inline Type operator^(Type::flag_type lhs, const Type& rhs) {               \
      return rhs ^ lhs;                                                         \
    } inline void operator^(Type::flag_type lhs, Type::mask_type rhs)           \
        ALLOW_UNUSED_TYPE;                                                      \
    inline void operator^(Type::flag_type lhs, Type::mask_type rhs) {}
  
  }  // namespace base
  }  // namespace v8
  
  #endif  // V8_BASE_FLAGS_H_
  