Program Listing for File get_message_type_support_handle.hpp

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// Copyright 2021 Open Source Robotics Foundation, Inc.
//
// 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.

#ifndef RCLCPP__GET_MESSAGE_TYPE_SUPPORT_HANDLE_HPP_
#define RCLCPP__GET_MESSAGE_TYPE_SUPPORT_HANDLE_HPP_

#include <type_traits>

#include "rosidl_runtime_cpp/traits.hpp"
#include "rosidl_runtime_cpp/message_type_support_decl.hpp"
#include "rosidl_typesupport_cpp/message_type_support.hpp"

#include "rclcpp/type_adapter.hpp"


namespace rclcpp
{

#ifdef DOXYGEN_ONLY


template<typename MessageT>
constexpr const rosidl_message_type_support_t & get_message_type_support_handle();

#else

template<typename MessageT>
constexpr
typename std::enable_if_t<
  rosidl_generator_traits::is_message<MessageT>::value,
  const rosidl_message_type_support_t &
>
get_message_type_support_handle()
{
  auto handle = rosidl_typesupport_cpp::get_message_type_support_handle<MessageT>();
  if (!handle) {
    throw std::runtime_error("Type support handle unexpectedly nullptr");
  }
  return *handle;
}

template<typename AdaptedType>
constexpr
typename std::enable_if_t<
  !rosidl_generator_traits::is_message<AdaptedType>::value &&
  rclcpp::TypeAdapter<AdaptedType>::is_specialized::value,
  const rosidl_message_type_support_t &
>
get_message_type_support_handle()
{
  auto handle = rosidl_typesupport_cpp::get_message_type_support_handle<
    typename TypeAdapter<AdaptedType>::ros_message_type
    >();
  if (!handle) {
    throw std::runtime_error("Type support handle unexpectedly nullptr");
  }
  return *handle;
}

// This specialization is a pass through runtime check, which allows a better
// static_assert to catch this issue further down the line.
// This should never get to be called in practice, and is purely defensive.
template<
  typename AdaptedType
>
constexpr
typename std::enable_if_t<
  !rosidl_generator_traits::is_message<AdaptedType>::value &&
  !TypeAdapter<AdaptedType>::is_specialized::value,
  const rosidl_message_type_support_t &
>
get_message_type_support_handle()
{
  throw std::runtime_error(
          "this specialization of rclcpp::get_message_type_support_handle() "
          "should never be called");
}

#endif

}  // namespace rclcpp

#endif  // RCLCPP__GET_MESSAGE_TYPE_SUPPORT_HANDLE_HPP_