rate.cc

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 * Author: Eitan Marder-Eppstein
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/******************************************************************************
 * Copyright 2018 The Apollo Authors. All Rights Reserved.
 *
 * 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.
 *****************************************************************************/
 
#include "cyber/time/rate.h"
 
#include "cyber/common/log.h"
 
namespace apollo {
namespace cyber {
 
Rate::Rate(double frequency)
    : start_(Time::Now()),
      expected_cycle_time_(1.0 / frequency),
      actual_cycle_time_(0.0) {}
 
Rate::Rate(uint64_t nanoseconds)
    : start_(Time::Now()),
      expected_cycle_time_(static_cast<int64_t>(nanoseconds)),
      actual_cycle_time_(0.0) {}
 
Rate::Rate(const Duration& d)
    : start_(Time::Now()), expected_cycle_time_(d), actual_cycle_time_(0.0) {}
 
void Rate::Sleep() {
  Time expected_end = start_ + expected_cycle_time_;
 
  Time actual_end = Time::Now();
 
  // detect backward jumps in time
  if (actual_end < start_) {
    AWARN << "Detect backward jumps in time";
    expected_end = actual_end + expected_cycle_time_;
  }
 
  // calculate the time we'll sleep for
  Duration sleep_time = expected_end - actual_end;
 
  // set the actual amount of time the loop took in case the user wants to kNow
  actual_cycle_time_ = actual_end - start_;
 
  // make sure to reset our start time
  start_ = expected_end;
 
  // if we've taken too much time we won't sleep
  if (sleep_time < Duration(0.0)) {
    AWARN << "Detect forward jumps in time";
    // if we've jumped forward in time, or the loop has taken more than a full
    // extra cycle, reset our cycle
    if (actual_end > expected_end + expected_cycle_time_) {
      start_ = actual_end;
    }
    // return false to show that the desired rate was not met
    return;
  }
 
  Time::SleepUntil(expected_end);
}
 
void Rate::Reset() { start_ = Time::Now(); }
 
Duration Rate::CycleTime() const { return actual_cycle_time_; }
 
}  // namespace cyber
}  // namespace apollo