boost_optional.hpp

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/*
 * Copyright 2020 Robert Bosch GmbH
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 */
#pragma once
 
#include <boost/optional.hpp>  // for optional<>
#include <nlohmann/json.hpp>   // for adl_serializer<>, json
 
/*
 * In order to provide serialization for third-party types, we need to either
 * use their namespace or provide a specialization in that of nlohmann. It is
 * illegal to define anything in the std namespace, so we are left no choice in
 * this regard.
 *
 * See: https://github.com/nlohmann/json
 */
namespace nlohmann {
 
template <typename T>
struct adl_serializer<boost::optional<T>> {
  static void to_json(json& j, const boost::optional<T>& opt) {
    if (opt) {
      j = *opt;
    } else {
      j = nullptr;
    }
  }
 
  static void from_json(const json& j, boost::optional<T>& opt) {
    if (j.type() == json::value_t::null) {
      opt.reset();
    } else {
      *opt = j.get<T>();
    }
  }
};
 
}  // namespace nlohmann