optional_serialization.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */
#pragma once

#include <mrpt/serialization/CArchive.h>
#include <mrpt/typemeta/TTypeName_stl.h>  // TTypeName<> for STL templates, needed for serialization of STL templates
#include <optional>

namespace mrpt::serialization
{
/** \addtogroup stlext_grp
 * @{ */

/** Template to serialize a std::optional<T> */
template <class T>
CArchive& operator<<(CArchive& out, const std::optional<T>& obj)
{
    out << std::string("std::optional") << mrpt::typemeta::TTypeName<T>::get();
    out << obj.has_value();
    if (obj.has_value()) out << *obj;
    return out;
}

/** Template to deserialize a std::optional<T> */
template <class T>
CArchive& operator>>(CArchive& in, std::optional<T>& obj)
{
    std::string pref, stored_T;
    in >> pref;
    if (pref != "std::optional")
        THROW_EXCEPTION(format(
            "Error: serialized std::optional<%s>'s preamble is wrong: '%s'",
            mrpt::typemeta::TTypeName<T>::get().c_str(), pref.c_str()));
    in >> stored_T;
    if (stored_T != std::string(mrpt::typemeta::TTypeName<T>::get().c_str()))
        THROW_EXCEPTION(format(
            "Error: serialized std::optional type %s != %s", stored_T.c_str(),
            mrpt::typemeta::TTypeName<T>::get().c_str()));

    bool has_value;
    in >> has_value;
    if (has_value)
    {
        T val;
        in >> val;
        obj = std::move(val);
    }
    else
    {
        obj.reset();
    }
    return in;
}

/** @} */  // end of grouping
}  // namespace mrpt::serialization