.. _program_listing_file_include_rclcpp_get_message_type_support_handle.hpp:

Program Listing for File get_message_type_support_handle.hpp
============================================================

|exhale_lsh| :ref:`Return to documentation for file <file_include_rclcpp_get_message_type_support_handle.hpp>` (``include/rclcpp/get_message_type_support_handle.hpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   // 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_