.. _program_listing_file_include_rclcpp_loaned_message.hpp:

Program Listing for File loaned_message.hpp
===========================================

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

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

.. code-block:: cpp

   // Copyright 2019 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__LOANED_MESSAGE_HPP_
   #define RCLCPP__LOANED_MESSAGE_HPP_
   
   #include <memory>
   #include <utility>
   
   #include "rclcpp/allocator/allocator_common.hpp"
   #include "rclcpp/logging.hpp"
   #include "rclcpp/publisher_base.hpp"
   
   #include "rcl/allocator.h"
   #include "rcl/publisher.h"
   
   namespace rclcpp
   {
   
   template<typename MessageT, typename AllocatorT = std::allocator<void>>
   class LoanedMessage
   {
     using MessageAllocatorTraits = rclcpp::allocator::AllocRebind<MessageT, AllocatorT>;
     using MessageAllocator = typename MessageAllocatorTraits::allocator_type;
   
   public:
   
     LoanedMessage(
       const rclcpp::PublisherBase & pub,
       std::allocator<MessageT> allocator)
     : pub_(pub),
       message_(nullptr),
       message_allocator_(std::move(allocator))
     {
       if (pub_.can_loan_messages()) {
         void * message_ptr = nullptr;
         auto ret = rcl_borrow_loaned_message(
           pub_.get_publisher_handle().get(),
           rosidl_typesupport_cpp::get_message_type_support_handle<MessageT>(),
           &message_ptr);
         if (RCL_RET_OK != ret) {
           rclcpp::exceptions::throw_from_rcl_error(ret);
         }
         message_ = static_cast<MessageT *>(message_ptr);
       } else {
         RCLCPP_INFO_ONCE(
           rclcpp::get_logger("rclcpp"),
           "Currently used middleware can't loan messages. Local allocator will be used.");
         message_ = message_allocator_.allocate(1);
         new (message_) MessageT();
       }
     }
   
   
     [[
       deprecated("used the LoanedMessage constructor that does not use a shared_ptr to the allocator")
     ]]
     LoanedMessage(
       const rclcpp::PublisherBase * pub,
       std::shared_ptr<std::allocator<MessageT>> allocator)
     : LoanedMessage(*pub, *allocator)
     {}
   
     LoanedMessage(LoanedMessage<MessageT> && other)
     : pub_(std::move(other.pub_)),
       message_(std::move(other.message_)),
       message_allocator_(std::move(other.message_allocator_))
     {
       other.message_ = nullptr;
     }
   
   
     virtual ~LoanedMessage()
     {
       auto error_logger = rclcpp::get_logger("LoanedMessage");
   
       if (message_ == nullptr) {
         return;
       }
   
       if (pub_.can_loan_messages()) {
         // return allocated memory to the middleware
         auto ret =
           rcl_return_loaned_message_from_publisher(pub_.get_publisher_handle().get(), message_);
         if (ret != RCL_RET_OK) {
           RCLCPP_ERROR(
             error_logger, "rcl_deallocate_loaned_message failed: %s", rcl_get_error_string().str);
           rcl_reset_error();
         }
       } else {
         // call destructor before deallocating
         message_->~MessageT();
         message_allocator_.deallocate(message_, 1);
       }
       message_ = nullptr;
     }
   
   
     bool is_valid() const
     {
       return message_ != nullptr;
     }
   
   
     MessageT & get() const
     {
       return *message_;
     }
   
   
     std::unique_ptr<MessageT, std::function<void(MessageT *)>>
     release()
     {
       auto msg = message_;
       message_ = nullptr;
   
       if (pub_.can_loan_messages()) {
         return std::unique_ptr<MessageT, std::function<void(MessageT *)>>(msg, [](MessageT *) {});
       }
   
       return std::unique_ptr<MessageT, std::function<void(MessageT *)>>(
         msg,
         [allocator = message_allocator_](MessageT * msg_ptr) mutable {
           // call destructor before deallocating
           msg_ptr->~MessageT();
           allocator.deallocate(msg_ptr, 1);
         });
     }
   
   protected:
     const rclcpp::PublisherBase & pub_;
   
     MessageT * message_;
   
     MessageAllocator message_allocator_;
   
     LoanedMessage(const LoanedMessage<MessageT> & other) = delete;
   };
   
   }  // namespace rclcpp
   
   #endif  // RCLCPP__LOANED_MESSAGE_HPP_