nps_flightgear.c

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#include "nps_flightgear.h"

#include <sys/socket.h>
#include <sys/time.h>
#include <errno.h>
#include <time.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>


#include "std.h"
#include "../flight_gear.h"
#include "nps_fdm.h"
#include "nps_atmosphere.h"

static struct  {
  int socket;
  struct sockaddr_in addr;
  int socket_in;
  unsigned int initial_time;
  unsigned int time_offset;
} flightgear;


double htond(double x)
{
  int *p = (int *)&x;
  int tmp = p[0];
  p[0] = htonl(p[1]);
  p[1] = htonl(tmp);

  return x;
}


float htonf(float x)
{
  int *p = (int *)&x;
  *p = htonl(*p);
  return x;
}


void nps_flightgear_init(const char *host,  unsigned int port, unsigned int port_in, unsigned int time_offset)
{
  int so_reuseaddr = 1;
  struct protoent *pte = getprotobyname("UDP");
  flightgear.socket = socket(PF_INET, SOCK_DGRAM, pte->p_proto);
  if (flightgear.socket < 0){
    perror("nps_flightgear_init flightgear.socket socket()");
    exit(errno);
  }
  if ( setsockopt(flightgear.socket, SOL_SOCKET, SO_REUSEADDR,
      &so_reuseaddr, sizeof(so_reuseaddr)) == -1) {
    perror("nps_flightgear_init flightgear.socket setsockopt()");
    exit(errno);
  }

  flightgear.addr.sin_family = PF_INET;
  flightgear.addr.sin_port = htons(port);
  flightgear.addr.sin_addr.s_addr = inet_addr(host);

  // incoming flight gear socket
  // only bind to socket if port_in is not zero
  if (port_in > 0) {
    struct sockaddr_in addr_in;
    flightgear.socket_in = socket(PF_INET, SOCK_DGRAM, pte->p_proto);
    if (flightgear.socket_in < 0) {
      perror("nps_flightgear_init flightgear.socket_in socket()");
      exit(errno);
    }
    if ( setsockopt(flightgear.socket_in, SOL_SOCKET, SO_REUSEADDR,
        &so_reuseaddr, sizeof(so_reuseaddr)) == -1) {
      perror("nps_flightgear_init flightgear.socket_in setsockopt()");
      exit(errno);
    }
    addr_in.sin_family = PF_INET;
    addr_in.sin_port = htons(port_in);
    addr_in.sin_addr.s_addr = htonl(INADDR_ANY);

    if (bind(flightgear.socket_in, (struct sockaddr*)&addr_in, sizeof(addr_in)) == -1) {
      perror("nps_flightgear_init bind()");
      exit(errno);
    }
    else{
      printf("Bount to port %u to receive from\n", port_in);
    }
  }
  else {
    flightgear.socket_in = -1;
  }

  // get current time to use as inital when computing cur_time for FG
  time_t t = time(NULL);
  flightgear.initial_time = t;
  flightgear.time_offset = time_offset;
}

void nps_flightgear_send_fdm()
{
  struct FGNetFDM fgfdm;

  memset(&fgfdm, 0, sizeof(fgfdm));
  fgfdm.version = htonl(FG_NET_FDM_VERSION);

  fgfdm.latitude  = htond(fdm.lla_pos.lat);
  fgfdm.longitude = htond(fdm.lla_pos.lon);
  fgfdm.altitude  = htond(fdm.lla_pos.alt);


  fgfdm.agl = htonf((float)fdm.agl);

  fgfdm.phi = htonf((float)fdm.ltp_to_body_eulers.phi);
  fgfdm.theta = htonf((float)fdm.ltp_to_body_eulers.theta);
  fgfdm.psi = htonf((float)fdm.ltp_to_body_eulers.psi);

  fgfdm.vcas = htonf(0.);
  fgfdm.climb_rate = htonf(0.);

  fgfdm.num_tanks = htonl(1);
  fgfdm.fuel_quantity[0] = htonf(0.);

  fgfdm.cur_time = htonl(flightgear.initial_time + rint(fdm.time));
  // if cur_time is zero, flightgear would take the real current time
  //gui.cur_time = 0;
  // warp is used as an offset to the current time in seconds
  fgfdm.warp = htonl(flightgear.time_offset);

  // Engine
  fgfdm.num_engines = htonl(fdm.num_engines);
  for (int k = 0; k < FG_NET_FDM_MAX_ENGINES; k++) {
    // Temprary hack to clearly show when the engine is running
    if (fdm.eng_state[k] == 1) {
      fgfdm.rpm[k] = htonf(fdm.rpm[k]);
    } else {
      fgfdm.rpm[k] = htonf(0.0);
    }
    fgfdm.eng_state[k] = htonl(fdm.eng_state[k]);
  }

  //control surfaces
  fgfdm.elevator = htonf(fdm.elevator);
  fgfdm.left_aileron = htonf(fdm.left_aileron);
  fgfdm.right_aileron = htonf(fdm.right_aileron);
  fgfdm.rudder = htonf(fdm.rudder);
  fgfdm.left_flap = htonf(fdm.flap);
  fgfdm.right_flap = htonf(fdm.flap);

  if (sendto(flightgear.socket, (char *)(&fgfdm), sizeof(fgfdm), 0,
             (struct sockaddr *)&flightgear.addr, sizeof(flightgear.addr)) == -1) {
    fprintf(stderr, "error sending to FlightGear\n");
    fflush(stderr);
  }
}

void nps_flightgear_send()
{

  struct FGNetGUI gui;

  gui.version = FG_NET_GUI_VERSION;
  gui.padding1 = 0; // initialize the padding variable to zero

  gui.latitude  = fdm.lla_pos.lat;
  gui.longitude = fdm.lla_pos.lon;
  gui.altitude  = fdm.lla_pos.alt;
  //  printf("%f %f %f\n", gui.latitude, gui.longitude, gui.altitude);

  gui.agl = 1.111652;

  gui.phi = fdm.ltp_to_body_eulers.phi;
  gui.theta = fdm.ltp_to_body_eulers.theta;
  gui.psi = fdm.ltp_to_body_eulers.psi;

  gui.vcas = 0.;
  gui.climb_rate = 0.;

  gui.num_tanks = 1;
  gui.fuel_quantity[0] = 0.;

  gui.cur_time = flightgear.initial_time + rint(fdm.time);
  // if cur_time is zero, flightgear would take the real current time
  //gui.cur_time = 0;
  // warp is used as an offset to the current time in seconds
  gui.warp = flightgear.time_offset;

  gui.ground_elev = 0.;

  gui.tuned_freq = 125.65;
  gui.nav_radial = 90.;
  gui.in_range = 1;
  gui.dist_nm = 10.;
  gui.course_deviation_deg = 0.;
  gui.gs_deviation_deg = 0.;

  if (sendto(flightgear.socket, (char *)(&gui), sizeof(gui), 0,
             (struct sockaddr *)&flightgear.addr, sizeof(flightgear.addr)) == -1) {
    fprintf(stderr, "error sending to FlightGear\n");
    fflush(stderr);
  }

}


void nps_flightgear_receive() {

  if (flightgear.socket_in != -1) {
    // socket is correctly opened

    struct FGEnvironment env;
    size_t s_env = sizeof(env);
    int bytes_read;

    //read first message
    memset(&env, 0, s_env);
    bytes_read = recvfrom(flightgear.socket_in, (char*)(&env), s_env, MSG_DONTWAIT, NULL, NULL);
    while (bytes_read != -1) { // while we read a message (empty buffer)
      if (bytes_read == (int)s_env){
        // Update wind info
        nps_atmosphere_set_wind_ned(
            (double)env.wind_from_north,
            (double)env.wind_from_east,
            (double)env.wind_from_down);
      }
      else {
        //error
        printf("WARNING : ignoring packet with size %d (%d expected)", bytes_read, (int)s_env);
      }

      //read next message
      memset(&env, 0, s_env);
      bytes_read = recvfrom(flightgear.socket_in, (char*)(&env), s_env, MSG_DONTWAIT, NULL, NULL);
    }

    if ((errno & (EAGAIN | EWOULDBLOCK)) == 0) {
      perror("nps_flightgear_receive recvfrom()");
    }
  }

}