UnityLayerMaskContains.cs

    // Unity LayerMask is castable to a 32bit int bit field.
    // Add some extension methods to make it easier and more readable to
    // determine if a given layer or object is within the bits of a mask.

    public static bool Contains(this LayerMask mask, int layer)
    {
        return (0 != (mask & (1 << layer)));
    }

    public static bool Contains(this LayerMask mask, GameObject gob)
    {
        if (gob == null)
            return false;
        return (0 != (mask & (1 << gob.layer)));
    }

    public static bool Contains(this LayerMask mask, Component component)
    {
        if (component == null)
            return false;
        return (0 != (mask & (1 << component.gameObject.layer)));
    }