.. _program_listing_file_include_rclcpp_wait_result.hpp:

Program Listing for File wait_result.hpp
========================================

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

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

.. code-block:: cpp

   // Copyright 2020 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__WAIT_RESULT_HPP_
   #define RCLCPP__WAIT_RESULT_HPP_
   
   #include <cassert>
   #include <functional>
   #include <stdexcept>
   
   #include "rcl/wait.h"
   
   #include "rclcpp/macros.hpp"
   #include "rclcpp/wait_result_kind.hpp"
   
   namespace rclcpp
   {
   
   // TODO(wjwwood): the union-like design of this class could be replaced with
   //   std::variant, when we have access to that...
   
   template<class WaitSetT>
   class WaitResult final
   {
   public:
   
     static
     WaitResult
     from_ready_wait_result_kind(WaitSetT & wait_set)
     {
       return WaitResult(WaitResultKind::Ready, wait_set);
     }
   
     static
     WaitResult
     from_timeout_wait_result_kind()
     {
       return WaitResult(WaitResultKind::Timeout);
     }
   
     static
     WaitResult
     from_empty_wait_result_kind()
     {
       return WaitResult(WaitResultKind::Empty);
     }
   
     WaitResultKind
     kind() const
     {
       return wait_result_kind_;
     }
   
   
     const WaitSetT &
     get_wait_set() const
     {
       if (this->kind() != WaitResultKind::Ready) {
         throw std::runtime_error("cannot access wait set when the result was not ready");
       }
       // This should never happen, defensive (and debug mode) check only.
       assert(wait_set_pointer_);
       return *wait_set_pointer_;
     }
   
   
     WaitSetT &
     get_wait_set()
     {
       if (this->kind() != WaitResultKind::Ready) {
         throw std::runtime_error("cannot access wait set when the result was not ready");
       }
       // This should never happen, defensive (and debug mode) check only.
       assert(wait_set_pointer_);
       return *wait_set_pointer_;
     }
   
     WaitResult(WaitResult && other) noexcept
     : wait_result_kind_(other.wait_result_kind_),
       wait_set_pointer_(std::exchange(other.wait_set_pointer_, nullptr))
     {}
   
     ~WaitResult()
     {
       if (wait_set_pointer_) {
         wait_set_pointer_->wait_result_release();
       }
     }
   
   private:
     RCLCPP_DISABLE_COPY(WaitResult)
   
     explicit WaitResult(WaitResultKind wait_result_kind)
     : wait_result_kind_(wait_result_kind)
     {
       // Should be enforced by the static factory methods on this class.
       assert(WaitResultKind::Ready != wait_result_kind);
     }
   
     WaitResult(WaitResultKind wait_result_kind, WaitSetT & wait_set)
     : wait_result_kind_(wait_result_kind),
       wait_set_pointer_(&wait_set)
     {
       // Should be enforced by the static factory methods on this class.
       assert(WaitResultKind::Ready == wait_result_kind);
       // Secure thread-safety (if provided) and shared ownership (if needed).
       wait_set_pointer_->wait_result_acquire();
     }
   
     const WaitResultKind wait_result_kind_;
   
     WaitSetT * wait_set_pointer_ = nullptr;
   };
   
   }  // namespace rclcpp
   
   #endif  // RCLCPP__WAIT_RESULT_HPP_