Flags.hpp

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#ifndef Flags_INCLUDE_ONCE
#define Flags_INCLUDE_ONCE

namespace vl
{
  template <typename T_FlagEnum>
  class Flags
  {
    // friends:
    template <typename T> friend Flags<T> operator|(T flag1, T flag2);
    template <typename T> friend Flags<T> operator&(T flag1, T flag2);

  public:
    typedef T_FlagEnum flag_type;
    typedef unsigned int flag_storage;

  public:
    Flags(): mFlags(0)  { }

    flag_storage flags() const { return mFlags; }

    void reset() { mFlags = 0; }

    // --- using Flags ---

    Flags operator|(const Flags& flag) const
    {
      Flags other = *this;
      other.mFlags |= flag.mFlags;
      return other;
    }

    Flags operator&(const Flags& flag) const
    {
      Flags other = *this;
      other.mFlags &= flag.mFlags;
      return other;
    }

    Flags operator^(const Flags& flag) const
    {
      Flags other = *this;
      other.mFlags ^= flag.mFlags;
      return other;
    }

    Flags operator-(const Flags& flag) const
    {
      Flags other = *this;
      other.mFlags &= ~flag.mFlags;
      return other;
    }

    // --- using T_FlagEnum ---

    Flags& set(T_FlagEnum flag)
    {
      mFlags |= (flag_storage)flag;
      return *this;
    }

    Flags& unset(T_FlagEnum flag)
    {
      mFlags &= ~(flag_storage)flag;
      return *this;
    }

    Flags& operator=(T_FlagEnum flag)
    {
      mFlags = flag;
      return this;
    }

    Flags operator|(T_FlagEnum flag) const
    {
      Flags other = *this;
      other.mFlags |= (flag_storage)flag;
      return other;
    }

    Flags operator&(T_FlagEnum flag) const
    {
      Flags other = *this;
      other.mFlags &= (flag_storage)flag;
      return other;
    }

    Flags operator^(T_FlagEnum flag) const
    {
      Flags other = *this;
      other.mFlags ^= (flag_storage)flag;
      return other;
    }

    Flags operator-(T_FlagEnum flag) const
    {
      Flags other = *this;
      other.unset(flag);
      return other;
    }

    operator bool() const
    {
      return mFlags != 0;
    }

  private:
    flag_storage mFlags;
  };

  template <typename T>
  Flags<T> operator|(T flag1, T flag2)
  {
    Flags<T> flags;
    flags.mFlags = (typename Flags<T>::flag_storage)flag1 | (typename Flags<T>::flag_storage)flag2;
    return flags;
  }

  template <typename T>
  Flags<T> operator&(T flag1, T flag2)
  {
    Flags<T> flags;
    flags.mFlags = (typename Flags<T>::flag_storage)flag1 & (typename Flags<T>::flag_storage)flag2;
    return flags;
  }
}

#define VL_DECLARE_FLAGS(EnumType, FlagTypeName)                                \
  template<EnumType> Flags<EnumType> operator|(EnumType flag1, EnumType flag2); \
  template<EnumType> Flags<EnumType> operator&(EnumType flag1, EnumType flag2); \
  typedef Flags<EnumType> FlagTypeName;

/***

usage:

enum MyFlagEnum
{
  Flag1 = 0x1,
  Flag2 = 0x2,
  Flag3 = 0x4,
};

VL_DECLARE_FLAGS(MyFlagEnum, MyFlags)

...

MyFlags f = Flag3 | Flag1;

***/

#endif