EnumFlag.h

// (C) Copyright 2015 Just Software Solutions Ltd
//
// Distributed under the Boost Software License, Version 1.0.
//
// Boost Software License - Version 1.0 - August 17th, 2003
//
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// http://stackoverflow.com/q/42481154/2880699
// https://www.justsoftwaresolutions.co.uk/cplusplus/using-enum-classes-as-bitfields.html

#pragma once

#include <type_traits>

template<typename E> // as suggested by Jay Miller
constexpr bool enable_bitmask_operators(E) {
    return false;
}

#define ENABLE_BIT_OPERATORS(E) constexpr bool enable_bitmask_operators(E) { return true; }

template<typename E>
typename std::enable_if<enable_bitmask_operators(E()), E>::type
operator|(E lhs, E rhs) {
    using underlying = typename std::underlying_type<E>::type;
    return static_cast<E>(
        static_cast<underlying>(lhs) | static_cast<underlying>(rhs));
}

template<typename E>
typename std::enable_if<enable_bitmask_operators(E()), E>::type
operator&(E lhs, E rhs) {
    using underlying = typename std::underlying_type<E>::type;
    return static_cast<E>(
        static_cast<underlying>(lhs) & static_cast<underlying>(rhs));
}

template<typename E>
typename std::enable_if<enable_bitmask_operators(E()), E>::type
operator^(E lhs, E rhs) {
    using underlying = typename std::underlying_type<E>::type;
    return static_cast<E>(
        static_cast<underlying>(lhs) ^ static_cast<underlying>(rhs));
}

template<typename E>
typename std::enable_if<enable_bitmask_operators(E()), E>::type
operator~(E lhs) {
    using underlying = typename std::underlying_type<E>::type;
    return static_cast<E>(
        ~static_cast<underlying>(lhs));
}

template<typename E>
typename std::enable_if<enable_bitmask_operators(E()), E&>::type
operator|=(E& lhs, E rhs) {
    using underlying = typename std::underlying_type<E>::type;
    lhs = static_cast<E>(
        static_cast<underlying>(lhs) | static_cast<underlying>(rhs));
    return lhs;
}

template<typename E>
typename std::enable_if<enable_bitmask_operators(E()), E&>::type
operator&=(E& lhs, E rhs) {
    using underlying = typename std::underlying_type<E>::type;
    lhs = static_cast<E>(
        static_cast<underlying>(lhs) & static_cast<underlying>(rhs));
    return lhs;
}

template<typename E>
typename std::enable_if<enable_bitmask_operators(E()), E&>::type
operator^=(E& lhs, E rhs) {
    using underlying = typename std::underlying_type<E>::type;
    lhs = static_cast<E>(
        static_cast<underlying>(lhs) ^ static_cast<underlying>(rhs));
    return lhs;
}

/// <summary>
/// Performs bitwise AND between two bitmasks and returns true if the result is not zero.
/// Typically used to check a bitmask for having a particular bit set.
/// </summary>
template<typename E>
bool operator%(E lhs, E rhs) {
    typedef typename std::underlying_type<E>::type underlying;
    return (static_cast<underlying>(lhs) & static_cast<underlying>(rhs)) != 0;
}