realtime_clock.cpp
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1 /*
2  * Copyright (c) 2013 hiDOF, Inc.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions are met:
7  *
8  * * Redistributions of source code must retain the above copyright
9  * notice, this list of conditions and the following disclaimer.
10  * * Redistributions in binary form must reproduce the above copyright
11  * notice, this list of conditions and the following disclaimer in the
12  * documentation and/or other materials provided with the distribution.
13  * * Neither the name of the Willow Garage, Inc. nor the names of its
14  * contributors may be used to endorse or promote products derived from
15  * this software without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
18  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
21  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27  * POSSIBILITY OF SUCH DAMAGE.
28  */
29 
30 /*
31  * Publishing ROS messages is difficult, as the publish function is
32  * not realtime safe. This class provides the proper locking so that
33  * you can call publish in realtime and a separate (non-realtime)
34  * thread will ensure that the message gets published over ROS.
35  *
36  * Author: Wim Meeussen
37  */
38 
40 
41 namespace realtime_tools
42 {
43 
44 
46  :lock_misses_(0),
47  system_time_(ros::Time()),
48  last_realtime_time_(ros::Time()),
49  running_(true),
50  initialized_(false)
51  {
52  // thread for time loop
53  thread_ = boost::thread(boost::bind(&RealtimeClock::loop, this));
54  }
55 
56 
58  {
59  running_ = false;
60  thread_.join();
61  }
62 
63 
64 
66  {
67  if (mutex_.try_lock())
68  {
69  // update time offset when we have a new system time measurement in the last cycle
70  if (lock_misses_ == 0 && system_time_ != ros::Time())
71  {
72  // get additional offset caused by period of realtime loop
73  ros::Duration period_offset;
75  period_offset = ros::Duration((realtime_time - last_realtime_time_).toSec()/2.0);
76 
77  if (!initialized_)
78  {
79  clock_offset_ = system_time_ + period_offset - realtime_time;
80  initialized_ = true;
81  }
82  else
83  clock_offset_ = clock_offset_*0.9999 + (system_time_ + period_offset - realtime_time)*0.0001;
84  }
86  lock_misses_ = 0;
87  mutex_.unlock();
88  }
89 
90  else
91  lock_misses_++;
92 
93  last_realtime_time_ = realtime_time;
94 
95  // return time
96  return realtime_time + clock_offset_;
97  }
98 
99 
100 
102  {
103  ros::Rate r(750);
104  while (running_)
105  {
106  // get lock
107  lock();
108 
109  // store system time
111 
112  // warning, using non-locked 'lock_misses_', but it's just for debugging
113  if (lock_misses_ > 100)
114  ROS_WARN_THROTTLE(1.0, "Time estimator has trouble transferring data between non-RT and RT");
115 
116  // release lock
117  mutex_.unlock();
118  r.sleep();
119  }
120  }
121 
122 
124  {
125 #ifdef NON_POLLING
126  mutex_.lock();
127 #else
128  while (!mutex_.try_lock())
129  usleep(500);
130 #endif
131  }
132 
133 }// namespace
134 
#define ROS_WARN_THROTTLE(rate,...)
ros::Time getSystemTime(const ros::Time &realtime_time)
bool sleep()
static Time now()


realtime_tools
Author(s): Stuart Glaser
autogenerated on Mon Mar 22 2021 02:20:09