.. _program_listing_file_include_rclcpp_rate.hpp:

Program Listing for File rate.hpp
=================================

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

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

.. code-block:: cpp

   // Copyright 2014 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__RATE_HPP_
   #define RCLCPP__RATE_HPP_
   
   #include <chrono>
   #include <memory>
   #include <thread>
   
   #include "rclcpp/macros.hpp"
   #include "rclcpp/utilities.hpp"
   #include "rclcpp/visibility_control.hpp"
   
   namespace rclcpp
   {
   
   class RateBase
   {
   public:
     RCLCPP_SMART_PTR_DEFINITIONS_NOT_COPYABLE(RateBase)
   
     virtual ~RateBase() {}
     virtual bool sleep() = 0;
     virtual bool is_steady() const = 0;
     virtual void reset() = 0;
   };
   
   using std::chrono::duration;
   using std::chrono::duration_cast;
   using std::chrono::nanoseconds;
   
   template<class Clock = std::chrono::high_resolution_clock>
   class GenericRate : public RateBase
   {
   public:
     RCLCPP_SMART_PTR_DEFINITIONS(GenericRate)
   
     explicit GenericRate(double rate)
     : GenericRate<Clock>(
         duration_cast<nanoseconds>(duration<double>(1.0 / rate)))
     {}
     explicit GenericRate(std::chrono::nanoseconds period)
     : period_(period), last_interval_(Clock::now())
     {}
   
     virtual bool
     sleep()
     {
       // Time coming into sleep
       auto now = Clock::now();
       // Time of next interval
       auto next_interval = last_interval_ + period_;
       // Detect backwards time flow
       if (now < last_interval_) {
         // Best thing to do is to set the next_interval to now + period
         next_interval = now + period_;
       }
       // Calculate the time to sleep
       auto time_to_sleep = next_interval - now;
       // Update the interval
       last_interval_ += period_;
       // If the time_to_sleep is negative or zero, don't sleep
       if (time_to_sleep <= std::chrono::seconds(0)) {
         // If an entire cycle was missed then reset next interval.
         // This might happen if the loop took more than a cycle.
         // Or if time jumps forward.
         if (now > next_interval + period_) {
           last_interval_ = now + period_;
         }
         // Either way do not sleep and return false
         return false;
       }
       // Sleep (will get interrupted by ctrl-c, may not sleep full time)
       rclcpp::sleep_for(time_to_sleep);
       return true;
     }
   
     virtual bool
     is_steady() const
     {
       return Clock::is_steady;
     }
   
     virtual void
     reset()
     {
       last_interval_ = Clock::now();
     }
   
     std::chrono::nanoseconds period() const
     {
       return period_;
     }
   
   private:
     RCLCPP_DISABLE_COPY(GenericRate)
   
     std::chrono::nanoseconds period_;
     using ClockDurationNano = std::chrono::duration<typename Clock::rep, std::nano>;
     std::chrono::time_point<Clock, ClockDurationNano> last_interval_;
   };
   
   using Rate = GenericRate<std::chrono::system_clock>;
   using WallRate = GenericRate<std::chrono::steady_clock>;
   
   }  // namespace rclcpp
   
   #endif  // RCLCPP__RATE_HPP_