Flags.hpp

// Copyright (C) 2017 Jérôme Leclercq
// This file is part of the "Nazara Engine - Core module"
// For conditions of distribution and use, see copyright notice in Config.hpp

#pragma once

#ifndef NAZARA_FLAGS_HPP
#define NAZARA_FLAGS_HPP

#include <Nazara/Prerequesites.hpp>
#include <type_traits>

namespace Nz
{
    // From: https://www.justsoftwaresolutions.co.uk/cplusplus/using-enum-classes-as-bitfields.html
    template<typename E>
    struct EnumAsFlags
    {
        static constexpr bool value = false;
        static constexpr int  max   = 0;
    };

    template<typename E>
    class Flags
    {
        static_assert(std::is_enum<E>::value, "Type must be an enumeration");
        static_assert(EnumAsFlags<E>::value, "Enum has not been enabled as flags by an EnumAsFlags specialization");

        public:
            using BitField = typename std::conditional<(EnumAsFlags<E>::max > 32), UInt64, UInt32>::type;

            constexpr Flags(BitField value = 0);
            constexpr Flags(E enumVal);

            explicit constexpr operator bool() const;
            explicit constexpr operator BitField() const;

            constexpr Flags operator~() const;
            constexpr Flags operator&(const Flags& rhs) const;
            constexpr Flags operator|(const Flags& rhs) const;
            constexpr Flags operator^(const Flags& rhs) const;

            constexpr bool operator==(const Flags& rhs) const;
            constexpr bool operator!=(const Flags& rhs) const;

            /*constexpr*/ Flags& operator|=(const Flags& rhs);
            /*constexpr*/ Flags& operator&=(const Flags& rhs);
            /*constexpr*/ Flags& operator^=(const Flags& rhs);

            static constexpr BitField GetFlagValue(E enumValue);

            static constexpr BitField ValueMask = ((BitField(1) << (EnumAsFlags<E>::max + 1)) - 1);

        private:
            BitField m_value;
    };

    // Little hack to have them in both Nz and global scope
    namespace FlagsOperators
    {
        template<typename E> constexpr std::enable_if_t<EnumAsFlags<E>::value, Flags<E>> operator~(E lhs);
        template<typename E> constexpr std::enable_if_t<EnumAsFlags<E>::value, Flags<E>> operator|(E lhs, E rhs);
        template<typename E> constexpr std::enable_if_t<EnumAsFlags<E>::value, Flags<E>> operator&(E lhs, E rhs);
        template<typename E> constexpr std::enable_if_t<EnumAsFlags<E>::value, Flags<E>> operator^(E lhs, E rhs);
    }

    using namespace FlagsOperators;
}

using namespace Nz::FlagsOperators;

#include <Nazara/Core/Flags.inl>

#endif // NAZARA_FLAGS_HPP