CVelodyneScanner.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

#include "hwdrivers-precomp.h"  // Precompiled headers

#include <mrpt/hwdrivers/CVelodyneScanner.h>
#include <mrpt/utils/CStream.h>
#include <mrpt/comms/net_utils.h>
#include <mrpt/hwdrivers/CGPSInterface.h>
#include <mrpt/system/filesystem.h>
#include <mrpt/utils/bits.h>  // for reverseBytesInPlace()

#include <thread>

// socket's hdrs:
#ifdef MRPT_OS_WINDOWS
#define _WINSOCK_DEPRECATED_NO_WARNINGS
#if defined(_WIN32_WINNT) && (_WIN32_WINNT < 0x600)
#undef _WIN32_WINNT
#define _WIN32_WINNT 0x600  // Minimum: Windows Vista (required to pollfd)
#endif

#include <winsock2.h>
typedef int socklen_t;

#if defined(__BORLANDC__) || defined(_MSC_VER)
#pragma comment(lib, "WS2_32.LIB")
#endif

#else
#define INVALID_SOCKET (-1)
#include <sys/time.h>  // gettimeofday()
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <poll.h>
#endif

#if MRPT_HAS_LIBPCAP
#include <pcap.h>
#if !defined(PCAP_NETMASK_UNKNOWN)  // for older pcap versions
#define PCAP_NETMASK_UNKNOWN 0xffffffff
#endif
#endif

using namespace mrpt;
using namespace mrpt::hwdrivers;
using namespace mrpt::obs;
using namespace std;

IMPLEMENTS_GENERIC_SENSOR(CVelodyneScanner, mrpt::hwdrivers)

short int CVelodyneScanner::VELODYNE_DATA_UDP_PORT = 2368;
short int CVelodyneScanner::VELODYNE_POSITION_UDP_PORT = 8308;

const CVelodyneScanner::model_properties_list_t&
        CVelodyneScanner::TModelPropertiesFactory::get()
{
        static CVelodyneScanner::model_properties_list_t modelProperties;
        static bool init = false;
        if (!init)
        {
                init = true;
                modelProperties[CVelodyneScanner::VLP16].maxRange = 120.0;
                modelProperties[CVelodyneScanner::HDL32].maxRange = 70.0;
                modelProperties[CVelodyneScanner::HDL64].maxRange = 120.0;
        }
        return modelProperties;
}
std::string CVelodyneScanner::TModelPropertiesFactory::getListKnownModels()
{
        const CVelodyneScanner::model_properties_list_t& lst =
                CVelodyneScanner::TModelPropertiesFactory::get();
        std::string s;
        for (CVelodyneScanner::model_properties_list_t::const_iterator it =
                         lst.begin();
                 it != lst.end(); ++it)
                s += mrpt::format(
                        "`%s`,",
                        mrpt::utils::TEnumType<CVelodyneScanner::model_t>::value2name(
                                it->first)
                                .c_str());
        return s;
}

CVelodyneScanner::CVelodyneScanner()
        : m_model(CVelodyneScanner::VLP16),
          m_pos_packets_min_period(0.5),
          m_pos_packets_timing_timeout(30.0),
          m_device_ip(""),
          m_pcap_verbose(true),
          m_last_pos_packet_timestamp(INVALID_TIMESTAMP),
          m_pcap(nullptr),
          m_pcap_out(nullptr),
          m_pcap_dumper(nullptr),
          m_pcap_bpf_program(nullptr),
          m_pcap_file_empty(true),
          m_pcap_read_once(false),
          m_pcap_read_fast(false),
          m_pcap_read_full_scan_delay_ms(100),
          m_pcap_repeat_delay(0.0),
          m_hDataSock(INVALID_SOCKET),
          m_hPositionSock(INVALID_SOCKET),
          m_last_gps_rmc_age(INVALID_TIMESTAMP),
          m_lidar_rpm(0),
          m_lidar_return(UNCHANGED)
{
        m_sensorLabel = "Velodyne";

#if MRPT_HAS_LIBPCAP
        m_pcap_bpf_program = new bpf_program[1];
#endif

#ifdef MRPT_OS_WINDOWS
        // Init the WinSock Library:
        WORD wVersionRequested = MAKEWORD(2, 0);
        WSADATA wsaData;
        if (WSAStartup(wVersionRequested, &wsaData))
                THROW_EXCEPTION("Error calling WSAStartup");
#endif
}

CVelodyneScanner::~CVelodyneScanner()
{
        this->close();
#ifdef MRPT_OS_WINDOWS
        WSACleanup();
#endif

#if MRPT_HAS_LIBPCAP
        delete[] reinterpret_cast<bpf_program*>(m_pcap_bpf_program);
        m_pcap_bpf_program = nullptr;
#endif
}

bool CVelodyneScanner::loadCalibrationFile(
        const std::string& velodyne_xml_calib_file_path)
{
        return m_velodyne_calib.loadFromXMLFile(velodyne_xml_calib_file_path);
}

void CVelodyneScanner::loadConfig_sensorSpecific(
        const mrpt::utils::CConfigFileBase& cfg, const std::string& sect)
{
        MRPT_START

        cfg.read_enum<CVelodyneScanner::model_t>(sect, "model", m_model);
        MRPT_LOAD_HERE_CONFIG_VAR(device_ip, string, m_device_ip, cfg, sect);
        MRPT_LOAD_HERE_CONFIG_VAR(pcap_input, string, m_pcap_input_file, cfg, sect);
        MRPT_LOAD_HERE_CONFIG_VAR(
                pcap_output, string, m_pcap_output_file, cfg, sect);
        MRPT_LOAD_HERE_CONFIG_VAR(
                pcap_read_once, bool, m_pcap_read_once, cfg, sect);
        MRPT_LOAD_HERE_CONFIG_VAR(
                pcap_read_fast, bool, m_pcap_read_fast, cfg, sect);
        MRPT_LOAD_HERE_CONFIG_VAR(
                pcap_read_full_scan_delay_ms, double, m_pcap_read_full_scan_delay_ms,
                cfg, sect);
        MRPT_LOAD_HERE_CONFIG_VAR(
                pcap_repeat_delay, double, m_pcap_repeat_delay, cfg, sect);
        MRPT_LOAD_HERE_CONFIG_VAR(
                pos_packets_timing_timeout, double, m_pos_packets_timing_timeout, cfg,
                sect);
        MRPT_LOAD_HERE_CONFIG_VAR(
                pos_packets_min_period, double, m_pos_packets_min_period, cfg, sect);

        using mrpt::utils::DEG2RAD;
        m_sensorPose = mrpt::poses::CPose3D(
                cfg.read_float(sect, "pose_x", 0), cfg.read_float(sect, "pose_y", 0),
                cfg.read_float(sect, "pose_z", 0),
                DEG2RAD(cfg.read_float(sect, "pose_yaw", 0)),
                DEG2RAD(cfg.read_float(sect, "pose_pitch", 0)),
                DEG2RAD(cfg.read_float(sect, "pose_roll", 0)));

        std::string calibration_file;
        MRPT_LOAD_CONFIG_VAR(calibration_file, string, cfg, sect);
        if (!calibration_file.empty()) this->loadCalibrationFile(calibration_file);

        // Check validity:
        const model_properties_list_t& lstModels = TModelPropertiesFactory::get();
        if (lstModels.find(m_model) == lstModels.end())
        {
                THROW_EXCEPTION(
                        mrpt::format(
                                "Unrecognized `model` parameter: `%u` . Known values are: %s",
                                static_cast<unsigned int>(m_model),
                                TModelPropertiesFactory::getListKnownModels().c_str()))
        }

        // Optional HTTP-based settings:
        MRPT_LOAD_HERE_CONFIG_VAR(rpm, int, m_lidar_rpm, cfg, sect);
        m_lidar_return =
                cfg.read_enum<return_type_t>(sect, "return_type", m_lidar_return);

        MRPT_END
}

bool CVelodyneScanner::getNextObservation(
        mrpt::obs::CObservationVelodyneScan::Ptr& outScan,
        mrpt::obs::CObservationGPS::Ptr& outGPS)
{
        try
        {
                ASSERTMSG_(m_initialized, "initialize() has not been called yet!");

                // Init with empty smart pointers:
                outScan = mrpt::obs::CObservationVelodyneScan::Ptr();
                outGPS = mrpt::obs::CObservationGPS::Ptr();

                // Try to get data & pos packets:
                mrpt::obs::CObservationVelodyneScan::TVelodyneRawPacket rx_pkt;
                mrpt::obs::CObservationVelodyneScan::TVelodynePositionPacket rx_pos_pkt;
                mrpt::system::TTimeStamp data_pkt_timestamp, pos_pkt_timestamp;
                bool rx_all_ok = this->receivePackets(
                        data_pkt_timestamp, rx_pkt, pos_pkt_timestamp, rx_pos_pkt);

                if (!rx_all_ok)
                {
                        // PCAP EOF:
                        return false;
                }

                if (pos_pkt_timestamp != INVALID_TIMESTAMP)
                {
                        mrpt::obs::CObservationGPS::Ptr gps_obs =
                                mrpt::make_aligned_shared<mrpt::obs::CObservationGPS>();
                        gps_obs->sensorLabel = this->m_sensorLabel + std::string("_GPS");
                        gps_obs->sensorPose = m_sensorPose;

                        gps_obs->originalReceivedTimestamp = pos_pkt_timestamp;

                        bool parsed_ok = CGPSInterface::parse_NMEA(
                                std::string(rx_pos_pkt.NMEA_GPRMC), *gps_obs);
                        const mrpt::obs::gnss::Message_NMEA_RMC* msg_rmc =
                                gps_obs->getMsgByClassPtr<mrpt::obs::gnss::Message_NMEA_RMC>();
                        if (!parsed_ok || !msg_rmc || msg_rmc->fields.validity_char != 'A')
                        {
                                gps_obs->has_satellite_timestamp = false;
                                gps_obs->timestamp = pos_pkt_timestamp;
                        }
                        else
                        {
                                // We have live GPS signal and a recent RMC frame:
                                m_last_gps_rmc_age = pos_pkt_timestamp;
                                m_last_gps_rmc = *msg_rmc;
                        }
                        outGPS = gps_obs;  // save in output object
                }

                if (data_pkt_timestamp != INVALID_TIMESTAMP)
                {
                        m_state = ssWorking;

                        // Break into a new observation object when the azimuth passes
                        // 360->0 deg:
                        const uint16_t rx_pkt_start_angle = rx_pkt.blocks[0].rotation;
                        // const uint16_t rx_pkt_end_angle   =
                        // rx_pkt.blocks[CObservationVelodyneScan::BLOCKS_PER_PACKET-1].rotation;

                        // Return the observation as done when a complete 360 deg scan is
                        // ready:
                        if (m_rx_scan && !m_rx_scan->scan_packets.empty())
                        {
                                if (rx_pkt_start_angle <
                                        m_rx_scan->scan_packets.rbegin()->blocks[0].rotation)
                                {
                                        outScan = m_rx_scan;
                                        m_rx_scan.reset();

                                        if (m_pcap)
                                        {
                                                // Keep the reader from blowing through the file.
                                                if (!m_pcap_read_fast)
                                                        std::this_thread::sleep_for(
                                                                std::chrono::duration<double, std::milli>(
                                                                        m_pcap_read_full_scan_delay_ms));
                                        }
                                }
                        }

                        // Create smart ptr to new in-progress observation:
                        if (!m_rx_scan)
                        {
                                m_rx_scan = mrpt::make_aligned_shared<
                                        mrpt::obs::CObservationVelodyneScan>();
                                m_rx_scan->sensorLabel =
                                        this->m_sensorLabel + std::string("_SCAN");
                                m_rx_scan->sensorPose = m_sensorPose;
                                m_rx_scan->calibration =
                                        m_velodyne_calib;  // Embed a copy of the calibration info

                                {
                                        const model_properties_list_t& lstModels =
                                                TModelPropertiesFactory::get();
                                        model_properties_list_t::const_iterator it =
                                                lstModels.find(this->m_model);
                                        if (it != lstModels.end())
                                        {  // Model params:
                                                m_rx_scan->maxRange = it->second.maxRange;
                                        }
                                        else  // default params:
                                        {
                                                m_rx_scan->maxRange = 120.0;
                                        }
                                }
                        }

                        // For the first packet, set timestamp:
                        if (m_rx_scan->scan_packets.empty())
                        {
                                m_rx_scan->originalReceivedTimestamp = data_pkt_timestamp;
                                // Using GPS, if available:
                                if (m_last_gps_rmc.fields.validity_char == 'A' &&
                                        mrpt::system::timeDifference(
                                                m_last_gps_rmc_age, data_pkt_timestamp) <
                                                m_pos_packets_timing_timeout)
                                {
                                        // Each Velodyne data packet has a timestamp field,
                                        // with the number of us since the top of the current HOUR:
                                        // take the date and time from the GPS, then modify minutes
                                        // and seconds from data pkt:
                                        const mrpt::system::TTimeStamp gps_tim =
                                                m_last_gps_rmc.fields.UTCTime.getAsTimestamp(
                                                        m_last_gps_rmc.getDateAsTimestamp());

                                        mrpt::system::TTimeParts tim_parts;
                                        mrpt::system::timestampToParts(gps_tim, tim_parts);
                                        tim_parts.minute =
                                                rx_pkt.gps_timestamp /*us from top of hour*/ /
                                                60000000ul;
                                        tim_parts.second =
                                                (rx_pkt.gps_timestamp /*us from top of hour*/ %
                                                 60000000ul) *
                                                1e-6;

                                        const mrpt::system::TTimeStamp data_pkt_tim =
                                                mrpt::system::buildTimestampFromParts(tim_parts);

                                        m_rx_scan->timestamp = data_pkt_tim;
                                        m_rx_scan->has_satellite_timestamp = true;
                                }
                                else
                                {
                                        m_rx_scan->has_satellite_timestamp = false;
                                        m_rx_scan->timestamp = data_pkt_timestamp;
                                }
                        }

                        // Accumulate pkts in the observation object:
                        m_rx_scan->scan_packets.push_back(rx_pkt);
                }

                return true;
        }
        catch (exception& e)
        {
                cerr << "[CVelodyneScanner::getObservation] Returning false due to "
                                "exception: "
                         << endl;
                cerr << e.what() << endl;
                return false;
        }
}

void CVelodyneScanner::doProcess()
{
        CObservationVelodyneScan::Ptr obs;
        CObservationGPS::Ptr obs_gps;

        if (getNextObservation(obs, obs_gps))
        {
                m_state = ssWorking;
                if (obs) appendObservation(obs);
                if (obs_gps) appendObservation(obs_gps);
        }
        else
        {
                m_state = ssError;
                cerr << "ERROR receiving data from Velodyne devic!" << endl;
        }
}

/** Tries to initialize the sensor, after setting all the parameters with a call
* to loadConfig.
*  \exception This method must throw an exception with a descriptive message if
* some critical error is found. */
void CVelodyneScanner::initialize()
{
        this->close();

        // (0) Preparation:
        // --------------------------------
        // Make sure we have calibration data:
        if (m_velodyne_calib.empty())
        {
                // Try to load default data:
                m_velodyne_calib = VelodyneCalibration::LoadDefaultCalibration(
                        mrpt::utils::TEnumType<CVelodyneScanner::model_t>::value2name(
                                m_model));
                if (m_velodyne_calib.empty())
                        THROW_EXCEPTION(
                                "Could not find default calibration data for the given LIDAR "
                                "`model` name. Please, specify a valid `model` or load a valid "
                                "XML configuration file first.");
        }

        // online vs off line operation??
        // -------------------------------
        if (m_pcap_input_file.empty())
        {  // Online

                if (m_lidar_rpm > 0)
                {
                        if (!setLidarRPM(m_lidar_rpm))
                                THROW_EXCEPTION("Error in setLidarRPM()!");
                }
                if (m_lidar_return != UNCHANGED)
                {
                        if (!setLidarReturnType(m_lidar_return))
                                THROW_EXCEPTION("Error in setLidarReturnType()!");
                }

                // (1) Create LIDAR DATA socket
                // --------------------------------
                if (INVALID_SOCKET == (m_hDataSock = socket(PF_INET, SOCK_DGRAM, 0)))
                        THROW_EXCEPTION(
                                format(
                                        "Error creating UDP socket:\n%s",
                                        mrpt::comms::net::getLastSocketErrorStr().c_str()));

                struct sockaddr_in bindAddr;
                memset(&bindAddr, 0, sizeof(bindAddr));
                bindAddr.sin_family = AF_INET;
                bindAddr.sin_port = htons(VELODYNE_DATA_UDP_PORT);
                bindAddr.sin_addr.s_addr = INADDR_ANY;

                if (int(INVALID_SOCKET) ==
                        ::bind(
                                m_hDataSock, (struct sockaddr*)(&bindAddr), sizeof(sockaddr)))
                        THROW_EXCEPTION(mrpt::comms::net::getLastSocketErrorStr());

#ifdef MRPT_OS_WINDOWS
                unsigned long non_block_mode = 1;
                if (ioctlsocket(m_hDataSock, FIONBIO, &non_block_mode))
                        THROW_EXCEPTION(
                                "Error entering non-blocking mode with ioctlsocket().");
#else
                int oldflags = fcntl(m_hDataSock, F_GETFL, 0);
                if (oldflags == -1)
                        THROW_EXCEPTION("Error retrieving fcntl() of socket.");
                oldflags |= O_NONBLOCK | FASYNC;
                if (-1 == fcntl(m_hDataSock, F_SETFL, oldflags))
                        THROW_EXCEPTION("Error entering non-blocking mode with fcntl().");
#endif

                // (2) Create LIDAR POSITION socket
                // --------------------------------
                if (INVALID_SOCKET ==
                        (m_hPositionSock = socket(PF_INET, SOCK_DGRAM, 0)))
                        THROW_EXCEPTION(
                                format(
                                        "Error creating UDP socket:\n%s",
                                        mrpt::comms::net::getLastSocketErrorStr().c_str()));

                bindAddr.sin_port = htons(VELODYNE_POSITION_UDP_PORT);

                if (int(INVALID_SOCKET) == ::bind(
                                                                           m_hPositionSock,
                                                                           (struct sockaddr*)(&bindAddr),
                                                                           sizeof(sockaddr)))
                        THROW_EXCEPTION(mrpt::comms::net::getLastSocketErrorStr());

#ifdef MRPT_OS_WINDOWS
                if (ioctlsocket(m_hPositionSock, FIONBIO, &non_block_mode))
                        THROW_EXCEPTION(
                                "Error entering non-blocking mode with ioctlsocket().");
#else
                oldflags = fcntl(m_hPositionSock, F_GETFL, 0);
                if (oldflags == -1)
                        THROW_EXCEPTION("Error retrieving fcntl() of socket.");
                oldflags |= O_NONBLOCK | FASYNC;
                if (-1 == fcntl(m_hPositionSock, F_SETFL, oldflags))
                        THROW_EXCEPTION("Error entering non-blocking mode with fcntl().");
#endif
        }
        else
        {  // Offline:
#if MRPT_HAS_LIBPCAP
                char errbuf[PCAP_ERRBUF_SIZE];

                if (m_pcap_verbose)
                        printf(
                                "\n[CVelodyneScanner] Opening PCAP file \"%s\"\n",
                                m_pcap_input_file.c_str());
                if ((m_pcap = pcap_open_offline(m_pcap_input_file.c_str(), errbuf)) ==
                        nullptr)
                {
                        THROW_EXCEPTION_FMT("Error opening PCAP file: '%s'", errbuf);
                }

                // Build PCAP filter:
                {
                        std::string filter_str = mrpt::format(
                                "(udp dst port %d || udp dst port %d)",
                                static_cast<int>(CVelodyneScanner::VELODYNE_DATA_UDP_PORT),
                                static_cast<int>(CVelodyneScanner::VELODYNE_POSITION_UDP_PORT));
                        if (!m_device_ip.empty())
                                filter_str += "&& src host " + m_device_ip;

                        static std::string sMsgError =
                                "[CVelodyneScanner] Error calling pcap_compile: ";  // This is
                        // to avoid
                        // the
                        // ill-formed
                        // signature
                        // of
                        // pcap_error()
                        // accepting
                        // "char*",
                        // not
                        // "const
                        // char*"...
                        // sigh
                        if (pcap_compile(
                                        reinterpret_cast<pcap_t*>(m_pcap),
                                        reinterpret_cast<bpf_program*>(m_pcap_bpf_program),
                                        filter_str.c_str(), 1, PCAP_NETMASK_UNKNOWN) < 0)
                                pcap_perror(reinterpret_cast<pcap_t*>(m_pcap), &sMsgError[0]);
                }

                m_pcap_file_empty = true;
                m_pcap_read_count = 0;

#else
                THROW_EXCEPTION(
                        "Velodyne: Reading from PCAP requires building MRPT with libpcap "
                        "support!");
#endif
        }

        m_last_pos_packet_timestamp = INVALID_TIMESTAMP;
        m_last_gps_rmc_age = INVALID_TIMESTAMP;
        m_state = ssInitializing;

        m_initialized = true;
}

void CVelodyneScanner::close()
{
        if (m_hDataSock != INVALID_SOCKET)
        {
                shutdown(m_hDataSock, 2);  // SD_BOTH  );
#ifdef MRPT_OS_WINDOWS
                closesocket(m_hDataSock);
#else
                ::close(m_hDataSock);
#endif
                m_hDataSock = INVALID_SOCKET;
        }

        if (m_hPositionSock != INVALID_SOCKET)
        {
                shutdown(m_hPositionSock, 2);  // SD_BOTH  );
#ifdef MRPT_OS_WINDOWS
                closesocket(m_hPositionSock);
#else
                ::close(m_hPositionSock);
#endif
                m_hPositionSock = INVALID_SOCKET;
        }
#if MRPT_HAS_LIBPCAP
        if (m_pcap)
        {
                pcap_close(reinterpret_cast<pcap_t*>(m_pcap));
                m_pcap = nullptr;
        }
        if (m_pcap_dumper)
        {
                pcap_dump_close(reinterpret_cast<pcap_dumper_t*>(m_pcap_dumper));
                m_pcap_dumper = nullptr;
        }
        if (m_pcap_out)
        {
                pcap_close(reinterpret_cast<pcap_t*>(m_pcap_out));
                m_pcap_out = nullptr;
        }
#endif
        m_initialized = false;
}

// Fixed Ethernet headers for PCAP capture --------
#if MRPT_HAS_LIBPCAP
const uint16_t LidarPacketHeader[21] = {0xffff, 0xffff, 0xffff, 0x7660, 0x0088,
                                                                                0x0000, 0x0008, 0x0045, 0xd204, 0x0000,
                                                                                0x0040, 0x11ff, 0xaab4, 0xa8c0, 0xc801,
                                                                                0xffff,  // checksum 0xa9b4 //source ip
                                                                                // 0xa8c0, 0xc801 is
                                                                                // 192.168.1.200
                                                                                0xffff, 0x4009, 0x4009, 0xbe04, 0x0000};
const uint16_t PositionPacketHeader[21] = {
        0xffff, 0xffff, 0xffff, 0x7660, 0x0088, 0x0000, 0x0008, 0x0045, 0xd204,
        0x0000, 0x0040, 0x11ff, 0xaab4, 0xa8c0, 0xc801, 0xffff,  // checksum 0xa9b4
        // //source ip
        // 0xa8c0, 0xc801
        // is 192.168.1.200
        0xffff, 0x7420, 0x7420, 0x0802, 0x0000};
#endif

#if defined(MRPT_OS_WINDOWS) && MRPT_HAS_LIBPCAP
int gettimeofday(struct timeval* tp, void*)
{
        FILETIME ft;
        ::GetSystemTimeAsFileTime(&ft);
        long long t =
                (static_cast<long long>(ft.dwHighDateTime) << 32) | ft.dwLowDateTime;
        t -= 116444736000000000LL;
        t /= 10;  // microseconds
        tp->tv_sec = static_cast<long>(t / 1000000UL);
        tp->tv_usec = static_cast<long>(t % 1000000UL);
        return 0;
}
#endif

bool CVelodyneScanner::receivePackets(
        mrpt::system::TTimeStamp& data_pkt_timestamp,
        mrpt::obs::CObservationVelodyneScan::TVelodyneRawPacket& out_data_pkt,
        mrpt::system::TTimeStamp& pos_pkt_timestamp,
        mrpt::obs::CObservationVelodyneScan::TVelodynePositionPacket& out_pos_pkt)
{
        MRPT_COMPILE_TIME_ASSERT(
                sizeof(mrpt::obs::CObservationVelodyneScan::TVelodynePositionPacket) ==
                CObservationVelodyneScan::POS_PACKET_SIZE);
        MRPT_COMPILE_TIME_ASSERT(
                sizeof(mrpt::obs::CObservationVelodyneScan::TVelodyneRawPacket) ==
                CObservationVelodyneScan::PACKET_SIZE);

        bool ret = true;  // all ok
        if (m_pcap)
        {
                ret = internal_read_PCAP_packet(
                        data_pkt_timestamp, (uint8_t*)&out_data_pkt, pos_pkt_timestamp,
                        (uint8_t*)&out_pos_pkt);
        }
        else
        {
                data_pkt_timestamp = internal_receive_UDP_packet(
                        m_hDataSock, (uint8_t*)&out_data_pkt,
                        CObservationVelodyneScan::PACKET_SIZE, m_device_ip);
                pos_pkt_timestamp = internal_receive_UDP_packet(
                        m_hPositionSock, (uint8_t*)&out_pos_pkt,
                        CObservationVelodyneScan::POS_PACKET_SIZE, m_device_ip);
        }

// Optional PCAP dump:
#if MRPT_HAS_LIBPCAP
        // Save to PCAP file?
        if (!m_pcap_output_file.empty() &&
                !m_pcap_out)  // 1st time: create output file
        {
#if MRPT_HAS_LIBPCAP
                char errbuf[PCAP_ERRBUF_SIZE];

                mrpt::system::TTimeParts parts;
                mrpt::system::timestampToParts(mrpt::system::now(), parts, true);
                string sFilePostfix = "_";
                sFilePostfix += format(
                        "%04u-%02u-%02u_%02uh%02um%02us", (unsigned int)parts.year,
                        (unsigned int)parts.month, (unsigned int)parts.day,
                        (unsigned int)parts.hour, (unsigned int)parts.minute,
                        (unsigned int)parts.second);
                const string sFileName =
                        m_pcap_output_file +
                        mrpt::system::fileNameStripInvalidChars(sFilePostfix) +
                        string(".pcap");

                m_pcap_out = pcap_open_dead(DLT_EN10MB, 65535);
                ASSERTMSG_(
                        m_pcap_out != nullptr, "Error creating PCAP live capture handle");

                printf(
                        "\n[CVelodyneScanner] Writing to PCAP file \"%s\"\n",
                        sFileName.c_str());
                if ((m_pcap_dumper = pcap_dump_open(
                                 reinterpret_cast<pcap_t*>(m_pcap_out), sFileName.c_str())) ==
                        nullptr)
                {
                        THROW_EXCEPTION_FMT(
                                "Error creating PCAP live dumper: '%s'", errbuf);
                }
#else
                THROW_EXCEPTION(
                        "Velodyne: Writing PCAP files requires building MRPT with libpcap "
                        "support!");
#endif
        }

        if (m_pcap_out && m_pcap_dumper &&
                (data_pkt_timestamp != INVALID_TIMESTAMP ||
                 pos_pkt_timestamp != INVALID_TIMESTAMP))
        {
                struct pcap_pkthdr header;
                struct timeval currentTime;
                gettimeofday(&currentTime, nullptr);
                std::vector<unsigned char> packetBuffer;

                // Data pkt:
                if (data_pkt_timestamp != INVALID_TIMESTAMP)
                {
                        header.caplen = header.len =
                                CObservationVelodyneScan::PACKET_SIZE + 42;
                        packetBuffer.resize(header.caplen);
                        header.ts = currentTime;

                        memcpy(&(packetBuffer[0]), LidarPacketHeader, 42);
                        memcpy(
                                &(packetBuffer[0]) + 42, (uint8_t*)&out_data_pkt,
                                CObservationVelodyneScan::PACKET_SIZE);
                        pcap_dump(
                                (u_char*)this->m_pcap_dumper, &header, &(packetBuffer[0]));
                }
                // Pos pkt:
                if (pos_pkt_timestamp != INVALID_TIMESTAMP)
                {
                        header.caplen = header.len =
                                CObservationVelodyneScan::POS_PACKET_SIZE + 42;
                        packetBuffer.resize(header.caplen);
                        header.ts = currentTime;

                        memcpy(&(packetBuffer[0]), PositionPacketHeader, 42);
                        memcpy(
                                &(packetBuffer[0]) + 42, (uint8_t*)&out_pos_pkt,
                                CObservationVelodyneScan::POS_PACKET_SIZE);
                        pcap_dump(
                                (u_char*)this->m_pcap_dumper, &header, &(packetBuffer[0]));
                }
        }
#endif

// Convert from Velodyne's standard little-endian ordering to host byte
// ordering:
// (done AFTER saving the pckg as is to pcap above)
#if MRPT_IS_BIG_ENDIAN
        if (data_pkt_timestamp != INVALID_TIMESTAMP)
        {
                mrpt::utils::reverseBytesInPlace(out_data_pkt.gps_timestamp);
                for (int i = 0; i < CObservationVelodyneScan::BLOCKS_PER_PACKET; i++)
                {
                        mrpt::utils::reverseBytesInPlace(out_data_pkt.blocks[i].header);
                        mrpt::utils::reverseBytesInPlace(out_data_pkt.blocks[i].rotation);
                        for (int k = 0; k < CObservationVelodyneScan::SCANS_PER_BLOCK; k++)
                        {
                                mrpt::utils::reverseBytesInPlace(
                                        out_data_pkt.blocks[i].laser_returns[k].distance);
                        }
                }
        }
        if (pos_pkt_timestamp != INVALID_TIMESTAMP)
        {
                mrpt::utils::reverseBytesInPlace(out_pos_pkt.gps_timestamp);
                mrpt::utils::reverseBytesInPlace(out_pos_pkt.unused2);
        }
#endif

        // Position packet decimation:
        if (pos_pkt_timestamp != INVALID_TIMESTAMP)
        {
                if (m_last_pos_packet_timestamp != INVALID_TIMESTAMP &&
                        mrpt::system::timeDifference(
                                m_last_pos_packet_timestamp, pos_pkt_timestamp) <
                                m_pos_packets_min_period)
                {
                        // Ignore this packet
                        pos_pkt_timestamp = INVALID_TIMESTAMP;
                }
                else
                {
                        // Reset time watch:
                        m_last_pos_packet_timestamp = pos_pkt_timestamp;
                }
        }

        return ret;
}

// static method:
mrpt::system::TTimeStamp CVelodyneScanner::internal_receive_UDP_packet(
        platform_socket_t hSocket, uint8_t* out_buffer,
        const size_t expected_packet_size, const std::string& filter_only_from_IP)
{
        if (hSocket == INVALID_SOCKET)
                THROW_EXCEPTION(
                        "Error: UDP socket is not open yet! Have you called initialize() "
                        "first?");

        unsigned long devip_addr = 0;
        if (!filter_only_from_IP.empty())
                devip_addr = inet_addr(filter_only_from_IP.c_str());

        const mrpt::system::TTimeStamp time1 = mrpt::system::now();

        struct pollfd fds[1];
        fds[0].fd = hSocket;
        fds[0].events = POLLIN;
        static const int POLL_TIMEOUT = 1;  // (ms)

        sockaddr_in sender_address;
        socklen_t sender_address_len = sizeof(sender_address);

        while (true)
        {
                // Unfortunately, the Linux kernel recvfrom() implementation
                // uses a non-interruptible std::this_thread::sleep_for(ms) when waiting
                // for data,
                // which would cause this method to hang if the device is not
                // providing data.  We poll() the device first to make sure
                // the recvfrom() will not block.
                //
                // Note, however, that there is a known Linux kernel bug:
                //
                //   Under Linux, select() may report a socket file descriptor
                //   as "ready for reading", while nevertheless a subsequent
                //   read blocks.  This could for example happen when data has
                //   arrived but upon examination has wrong checksum and is
                //   discarded.  There may be other circumstances in which a
                //   file descriptor is spuriously reported as ready.  Thus it
                //   may be safer to use O_NONBLOCK on sockets that should not
                //   block.

                // poll() until input available
                do
                {
                        int retval =
#if !defined(MRPT_OS_WINDOWS)
                                poll
#else
                                WSAPoll
#endif
                                (fds, 1, POLL_TIMEOUT);
                        if (retval < 0)  // poll() error?
                        {
                                if (errno != EINTR)
                                        THROW_EXCEPTION(
                                                format(
                                                        "Error in UDP poll():\n%s",
                                                        mrpt::comms::net::getLastSocketErrorStr().c_str()));
                        }
                        if (retval == 0)  // poll() timeout?
                        {
                                return INVALID_TIMESTAMP;
                        }
                        if ((fds[0].revents & POLLERR) || (fds[0].revents & POLLHUP) ||
                                (fds[0].revents & POLLNVAL))  // device error?
                        {
                                THROW_EXCEPTION(
                                        "Error in UDP poll() (seems Velodyne device error?)");
                        }
                } while ((fds[0].revents & POLLIN) == 0);

                // Receive packets that should now be available from the
                // socket using a blocking read.
                int nbytes = recvfrom(
                        hSocket, (char*)&out_buffer[0], expected_packet_size, 0,
                        (sockaddr*)&sender_address, &sender_address_len);

                if (nbytes < 0)
                {
                        if (errno != EWOULDBLOCK) THROW_EXCEPTION("recvfrom() failed!?!")
                }
                else if ((size_t)nbytes == expected_packet_size)
                {
                        // read successful,
                        // if packet is not from the lidar scanner we selected by IP,
                        // continue otherwise we are done
                        if (!filter_only_from_IP.empty() &&
                                sender_address.sin_addr.s_addr != devip_addr)
                                continue;
                        else
                                break;  // done
                }

                std::cerr
                        << "[CVelodyneScanner] Warning: incomplete Velodyne packet read: "
                        << nbytes << " bytes\n";
        }

        // Average the times at which we begin and end reading.  Use that to
        // estimate when the scan occurred.
        const mrpt::system::TTimeStamp time2 = mrpt::system::now();

        return (time1 / 2 + time2 / 2);
}

bool CVelodyneScanner::internal_read_PCAP_packet(
        mrpt::system::TTimeStamp& data_pkt_time, uint8_t* out_data_buffer,
        mrpt::system::TTimeStamp& pos_pkt_time, uint8_t* out_pos_buffer)
{
#if MRPT_HAS_LIBPCAP
        ASSERT_(m_pcap);

        data_pkt_time = INVALID_TIMESTAMP;
        pos_pkt_time = INVALID_TIMESTAMP;

        char errbuf[PCAP_ERRBUF_SIZE];
        struct pcap_pkthdr* header;
        const u_char* pkt_data;

        while (true)
        {
                int res;
                if ((res = pcap_next_ex(
                                 reinterpret_cast<pcap_t*>(m_pcap), &header, &pkt_data)) >= 0)
                {
                        ++m_pcap_read_count;

                        // if packet is not from the lidar scanner we selected by IP,
                        // continue
                        if (pcap_offline_filter(
                                        reinterpret_cast<bpf_program*>(m_pcap_bpf_program), header,
                                        pkt_data) == 0)
                        {
                                if (m_verbose)
                                        std::cout
                                                << "[CVelodyneScanner] DEBUG: Filtering out packet #"
                                                << m_pcap_read_count << " in PCAP file.\n";
                                continue;
                        }

                        // Determine whether it is a DATA or POSITION packet:
                        m_pcap_file_empty = false;
                        const mrpt::system::TTimeStamp tim = mrpt::system::now();
                        const uint16_t udp_dst_port =
                                ntohs(*reinterpret_cast<const uint16_t*>(pkt_data + 0x24));

                        if (udp_dst_port == CVelodyneScanner::VELODYNE_POSITION_UDP_PORT)
                        {
                                if (m_verbose)
                                        std::cout << "[CVelodyneScanner] DEBUG: Packet #"
                                                          << m_pcap_read_count
                                                          << " in PCAP file is POSITION pkt.\n";
                                memcpy(
                                        out_pos_buffer, pkt_data + 42,
                                        CObservationVelodyneScan::POS_PACKET_SIZE);
                                pos_pkt_time = tim;  // success
                                return true;
                        }
                        else if (udp_dst_port == CVelodyneScanner::VELODYNE_DATA_UDP_PORT)
                        {
                                if (m_verbose)
                                        std::cout << "[CVelodyneScanner] DEBUG: Packet #"
                                                          << m_pcap_read_count
                                                          << " in PCAP file is DATA pkt.\n";
                                memcpy(
                                        out_data_buffer, pkt_data + 42,
                                        CObservationVelodyneScan::PACKET_SIZE);
                                data_pkt_time = tim;  // success
                                return true;
                        }
                        else
                        {
                                std::cerr << "[CVelodyneScanner] ERROR: Packet "
                                                  << m_pcap_read_count
                                                  << " in PCAP file passed the filter but does not "
                                                         "match expected UDP port numbers! Skipping it.\n";
                        }
                }

                if (m_pcap_file_empty)  // no data in file?
                {
                        fprintf(
                                stderr,
                                "[CVelodyneScanner] Maybe the PCAP file is empty? Error %d "
                                "reading Velodyne packet: `%s`\n",
                                res, pcap_geterr(reinterpret_cast<pcap_t*>(m_pcap)));
                        return true;
                }

                if (m_pcap_read_once)
                {
                        if (m_pcap_verbose)
                                printf(
                                        "[CVelodyneScanner] INFO: end of file reached -- done "
                                        "reading.\n");
                        std::this_thread::sleep_for(250ms);
                        return false;
                }

                if (m_pcap_repeat_delay > 0.0)
                {
                        if (m_pcap_verbose)
                                printf(
                                        "[CVelodyneScanner] INFO: end of file reached -- delaying "
                                        "%.3f seconds.\n",
                                        m_pcap_repeat_delay);
                        std::this_thread::sleep_for(
                                std::chrono::duration<double, std::milli>(
                                        m_pcap_repeat_delay * 1000.0));
                }

                if (m_pcap_verbose)
                        printf("[CVelodyneScanner] INFO: replaying Velodyne dump file.\n");

                // rewind the file
                pcap_close(reinterpret_cast<pcap_t*>(m_pcap));
                if ((m_pcap = pcap_open_offline(m_pcap_input_file.c_str(), errbuf)) ==
                        nullptr)
                {
                        THROW_EXCEPTION_FMT("Error opening PCAP file: '%s'", errbuf);
                }
                m_pcap_file_empty = true;  // maybe the file disappeared?
        }  // loop back and try again
#else
        THROW_EXCEPTION(
                "MRPT needs to be built against libpcap to enable this functionality")
#endif
}

bool CVelodyneScanner::setLidarReturnType(return_type_t ret_type)
{
        /* HTTP-based config: http://10.0.0.100/tab/config.html
                <form name='returns' method="post" action="/cgi/setting">
                <span>Return&nbsp;Type:&nbsp;</span> <select name="returns"
                onchange='javascript:this.form.submit()'>
                <option>Strongest</option>
                <option>Last</option>
                <option>Dual</option>
                </select>
                </form>
        */
        MRPT_START;
        std::string strRet;
        switch (ret_type)
        {
                case STRONGEST:
                        strRet = "Strongest";
                        break;
                case DUAL:
                        strRet = "Dual";
                        break;
                case LAST:
                        strRet = "Last";
                        break;
                case UNCHANGED:
                        return true;
                default:
                        THROW_EXCEPTION("Invalid value for return type!");
        };

        const std::string cmd = mrpt::format("returns=%s", strRet.c_str());
        return this->internal_send_http_post(cmd);
        MRPT_END;
}

bool CVelodyneScanner::setLidarRPM(int rpm)
{
        /* HTTP-based config: http://10.0.0.100/tab/config.html
        <form name='rpm' method="post" action="/cgi/setting">
        Motor
        &nbsp;RPM:&nbsp;<input type="text" name="rpm" size="5"
        style="text-align:right" /><input type="button" value="+"
        onclick="javascript:this.form.rpm.value++;this.form.submit()" /><input
        type="button" value="-"
        onclick="javascript:this.form.rpm.value--;this.form.submit()" />
        &nbsp;<input type="submit" value="Set" />
        </form>
        */

        MRPT_START;
        const std::string cmd = mrpt::format("rpm=%i", rpm);
        return this->internal_send_http_post(cmd);
        MRPT_END;
}

bool CVelodyneScanner::setLidarOnOff(bool on)
{
        // laser = on|off
        MRPT_START;
        const std::string cmd = mrpt::format("laser=%s", on ? "on" : "off");
        return this->internal_send_http_post(cmd);
        MRPT_END;
}

bool CVelodyneScanner::internal_send_http_post(const std::string& post_data)
{
        MRPT_START;

        ASSERTMSG_(
                !m_device_ip.empty(), "A device IP address must be specified first!");

        using namespace mrpt::comms::net;

        vector_byte post_out;
        string post_err_str;

        int http_rep_code;
        mrpt::utils::TParameters<string> extra_headers, out_headers;

        extra_headers["Origin"] = mrpt::format("http://%s", m_device_ip.c_str());
        extra_headers["Referer"] = mrpt::format("http://%s", m_device_ip.c_str());
        extra_headers["Upgrade-Insecure-Requests"] = "1";
        extra_headers["Content-Type"] = "application/x-www-form-urlencoded";

        ERRORCODE_HTTP ret = http_request(
                "POST", post_data,
                mrpt::format("http://%s/cgi/setting", m_device_ip.c_str()), post_out,
                post_err_str, 80 /* port */, string(), string(),  // user,pass
                &http_rep_code, &extra_headers, &out_headers);

        return mrpt::comms::net::erOk == ret &&
                   (http_rep_code == 200 || http_rep_code == 204);  // OK codes

        MRPT_END;
}