library/cpp/yt/misc/optional.h - main - githubmirror/nbs

library/cpp/yt/misc/optional.h
106 строк2 KB
Anton Myagkov
Update ydb version to 24.4 (#4579)
07 фев 2026, 11:59
07 фев 2026, 11:592c21cae
#pragma once

#include <util/string/cast.h>

#include <optional>

namespace NYT {

////////////////////////////////////////////////////////////////////////////////

template <class T>
struct TOptionalTraits
{
    using TOptional = std::optional<T>;
    using TValue = T;

    static constexpr bool HasValue(const TOptional& opt)
    {
        return opt.has_value();
    }

    static constexpr TOptional Empty()
    {
        return std::nullopt;
    }
};

template <class T>
struct TOptionalTraits<std::optional<T>>
{
    using TOptional = std::optional<T>;
    using TValue = T;

    static constexpr bool HasValue(const TOptional& opt)
    {
        return opt.has_value();
    }

    static constexpr TOptional Empty()
    {
        return std::nullopt;
    }
};

template <class T>
struct TOptionalTraits<T*>
{
    using TOptional = T*;
    using TValue = T*;

    static constexpr bool HasValue(const TOptional& opt)
    {
        return opt != nullptr;
    }

    static constexpr TOptional Empty()
    {
        return nullptr;
    }
};

template <class T>
struct TOptionalTraits<TIntrusivePtr<T>>
{
    using TOptional = TIntrusivePtr<T>;
    using TValue = TIntrusivePtr<T>;

    static bool HasValue(const TOptional& opt)
    {
        return opt.Get() != nullptr;
    }

    static constexpr TOptional Empty()
    {
        return TIntrusivePtr<T>{};
    }
};

////////////////////////////////////////////////////////////////////////////////

template <class T>
struct TStdOptionalTraits
{
    static constexpr bool IsStdOptional = false;
    using TValueType = T;
};

template <class T>
struct TStdOptionalTraits<std::optional<T>>
{
    static constexpr bool IsStdOptional = true;
    using TValueType = T;
};

////////////////////////////////////////////////////////////////////////////////

} // namespace NYT

template <class T>
struct THash<std::optional<T>>
{
    size_t operator()(const std::optional<T>& nullable) const
    {
        return nullable ? THash<T>()(*nullable) : 0;
    }
};