Are enums the canonical way to implement bit flags?

Question

Currently I'm using enums to represent a state in a little game experiment. I declare them like so:

namespace State {
  enum Value {
    MoveUp = 1 << 0, // 00001 == 1
    MoveDown = 1 << 1, // 00010 == 2
    MoveLeft = 1 << 2, // 00100 == 4
    MoveRight = 1 << 3, // 01000 == 8
    Still = 1 << 4, // 10000 == 16
    Jump = 1 << 5
  };
}

So that I can use them this way:

State::Value state = State::Value(0);
state = State::Value(state | State::MoveUp);
if (mState & State::MoveUp)
  movement.y -= mPlayerSpeed;

But I'm wondering if this is the right way to implement bit flags. Isn't there a special container for bit flags? I heard about std::bitset, is it what I should use? Do you know something more efficient?
Am I doing it right?

---

I forgot to point out I was overloading the basic operators of my enum:

inline State::Value operator|(State::Value a, State::Value b)
{ return static_cast<State::Value>(static_cast<int>(a) | static_cast<int>(b)); }

inline State::Value operator&(State::Value a, State::Value b)
{ return static_cast<State::Value>(static_cast<int>(a) & static_cast<int>(b)); }


inline State::Value& operator|=(State::Value& a, State::Value b)
{ return (State::Value&)((int&)a |= (int)b); }

I had to use a C-style cast for the |=, it didn't work with a static_cast - any idea why?

Answer 1

I believe that your approach is right (except several things):
1. You can explicitly specify underlying type to save memory;
2. You can not use unspecified enum values.

namespace State {
  enum Value : char {
    None      = 0,
    MoveUp    = 1 << 0, // 00001 == 1
    MoveDown  = 1 << 1, // 00010 == 2
    MoveLeft  = 1 << 2, // 00100 == 4
    MoveRight = 1 << 3, // 01000 == 8
    Still     = 1 << 4, // 10000 == 16
    Jump      = 1 << 5
  };
}

and:

State::Value state = State::Value::None;
state = State::Value(state | State::MoveUp);
if (mState & State::MoveUp) {
  movement.y -= mPlayerSpeed;
}

about overloading:

inline State::Value& operator|=(State::Value& a, State::Value b) {
    return a = static_cast<State::Value> (a | b);
}

and since you use C++11, you should use constexpr every were is possible:

inline constexpr State::Value operator|(State::Value a, State::Value b) {
    return a = static_cast<State::Value> (a | b);
}

inline constexpr State::Value operator&(State::Value a, State::Value b) {
    return a = static_cast<State::Value> (a & b);
}