weex_core/Source/include/wtf/EnumTraits.h

/*
 * Copyright (C) 2016 Apple Inc. All rights reserved.
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 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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 */

#pragma once

#include <type_traits>

namespace WTF {

template<typename> struct EnumTraits;

template<typename E, E...> struct EnumValues;

template<typename T, typename E> struct EnumValueChecker;

template<typename T, typename E, E e, E... es>
struct EnumValueChecker<T, EnumValues<E, e, es...>> {
    static constexpr bool isValidEnum(T t)
    {
        return (static_cast<T>(e) == t) ? true : EnumValueChecker<T, EnumValues<E, es...>>::isValidEnum(t);
    }
};

template<typename T, typename E>
struct EnumValueChecker<T, EnumValues<E>> {
    static constexpr bool isValidEnum(T)
    {
        return false;
    }
};

template<typename E, typename T>
constexpr auto isValidEnum(T t) -> std::enable_if_t<std::is_enum<E>::value, bool>
{
    static_assert(sizeof(T) >= std::underlying_type_t<E>(), "Integral type must be at least the size of the underlying enum type");

    return EnumValueChecker<T, typename EnumTraits<E>::values>::isValidEnum(t);
}

}

using WTF::isValidEnum;