time_conversion.hpp

Go to the documentation of this file.

// Copyright (C) 2019 Matthew Pitropov, Joshua Whitley
// All rights reserved.
//
// Software License Agreement (BSD License 2.0)
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
//  * Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//  * Redistributions in binary form must reproduce the above
//    copyright notice, this list of conditions and the following
//    disclaimer in the documentation and/or other materials provided
//    with the distribution.
//  * Neither the name of {copyright_holder} nor the names of its
//    contributors may be used to endorse or promote products derived
//    from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
 
#ifndef VELODYNE_DRIVER_TIME_CONVERSION_HPP
#define VELODYNE_DRIVER_TIME_CONVERSION_HPP
 
#include <pcap.h>
 
#include <ros/ros.h>
#include <ros/time.h>
 
ros::Time resolveHourAmbiguity(const ros::Time &stamp, const ros::Time &nominal_stamp) {
    const int HALFHOUR_TO_SEC = 1800;
    ros::Time retval = stamp;
    if (nominal_stamp.sec > stamp.sec) {
        if (nominal_stamp.sec - stamp.sec > HALFHOUR_TO_SEC) {
            retval.sec = retval.sec + 2*HALFHOUR_TO_SEC;
        }
    } else if (stamp.sec - nominal_stamp.sec > HALFHOUR_TO_SEC) {
        retval.sec = retval.sec - 2*HALFHOUR_TO_SEC;
    }
    return retval;
}
 
ros::Time rosTimeFromGpsTimestamp(const uint8_t * const data, const struct pcap_pkthdr *header = NULL) {
    const int HOUR_TO_SEC = 3600;
    // time for each packet is a 4 byte uint
    // It is the number of microseconds from the top of the hour
    uint32_t usecs = (uint32_t) ( ((uint32_t) data[3]) << 24 |
                                  ((uint32_t) data[2] ) << 16 |
                                  ((uint32_t) data[1] ) << 8 |
                                  ((uint32_t) data[0] ));
    ros::Time time_nom = ros::Time();
    // if header is NULL, assume real time operation
    if (!header) {
        time_nom = ros::Time::now(); // use this to recover the hour
    } else {
        time_nom = ros::Time(header->ts.tv_sec, header->ts.tv_usec * 1000);
    }
    uint32_t cur_hour = time_nom.sec / HOUR_TO_SEC;
    ros::Time stamp = ros::Time((cur_hour * HOUR_TO_SEC) + (usecs / 1000000),
                                (usecs % 1000000) * 1000);
    stamp = resolveHourAmbiguity(stamp, time_nom);
    return stamp;
}
 
#endif //VELODYNE_DRIVER_TIME_CONVERSION_HPP