/* Last modified on Sat Jan 8 2011, Hal Murray */

/*
 *  This is a hack to grab sentences from NMEA GPS receivers and
 *  print them out with the time the final CR/NL arrived.
 */

char *default_tty = "/dev/ttyUSB7";

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h> 
#include <termios.h>
#include <time.h>
#include <unistd.h>
#include <sys/time.h>


/* prototypes */
int SetupTTY(char *tty, int baud);

int fd = -1;

int SetupTTY(char *tty, int baud) {
  int err, i;
  struct termios mode;
  int baud_code;
  char buffer[100];

  printf("Listening to %s at %d baud\n", tty, baud);

  switch (baud) {
    case 4800:   baud_code = B4800;  break;
    case 19200:  baud_code = B19200; break;
    default:
      printf("# Unrecognized baud rate: %d\n", baud);
      sleep(10);
      return(1);
  }


  /* need NONBLOCK to avoid hanging if LOCAL flag isn't set */
  /* At least on real TTYs. */
  fd = open(tty, O_RDONLY | O_NONBLOCK);
  if (fd < 0) {
    printf("# Can't open %s: %s\n", tty, strerror(errno));
    sleep(10);
    return(1);
  }
  /* Setup all the mode bits.  Check with: stty -a -F /dev/ttyUSB1 */
  err = tcgetattr(fd, &mode);
  if (err < 0) {
    printf("# tcsetattr failed: %s\n", strerror(errno));
    sleep(10);
    return(1);
  }
  mode.c_iflag = IGNBRK | IGNPAR | IGNCR;
  mode.c_oflag = 0;
  mode.c_cflag = CS8 | CLOCAL | CREAD;
  mode.c_lflag = ICANON;                /* Line-at-a-time mode */
  for (i=0; i<NCCS; i++) mode.c_cc[i] = '\0';
  cfsetispeed(&mode, baud_code);
  cfsetospeed(&mode, baud_code);
  err = tcsetattr(fd, TCSANOW, &mode);
  if (err < 0) {
    printf("# tcsetattr failed: %s\n", strerror(errno));
    sleep(10);
    return(1);
  }

  /* reopen to turn off NONBLOCK flag */
  close(fd);
  fd = open(tty, O_RDONLY);
  if (fd < 0) {
    printf("# Can't re-open %s: %s\n", tty, strerror(errno));
    sleep(10);
    return(1);
  }

  err = tcflush(fd, TCIOFLUSH);
  if (err < 0) {
    printf("# tcflush failed: %s\n", strerror(errno));
    sleep(10);
    return(1);
  }
  /* Get rest of line in case we flush in the middle of one. */
  err = read(fd, buffer, sizeof(buffer));
  if (err < 0) {
    printf("# read/flush: %s\n", strerror(errno));
    sleep(10);
    return(1);
  }
  return(0);
}


int main(int argc, char *argv[])
{

  char *tty = default_tty;
  int baud = 4800;

  char buffer[100];
  int i, len;
  struct timeval now;
  struct tm *nowtm;

  for (i=1; i<argc; i++) {
    /* printf("## Arg %d: %s\n", i, argv[i]); */
    if      (!strcmp(argv[i], "4800"))  baud = 4800;
    else if (!strcmp(argv[i], "19200")) baud = 19200;
    else                                tty = argv[i];
  }

  if (SetupTTY(tty, baud)) return(1);

  while (1) {
    len = read(fd, buffer, sizeof(buffer));
    if (len < 0) {
      printf("# read failed: %s\n", strerror(errno));
      sleep(10);
      return(1);
    }
    gettimeofday(&now, NULL);
    if (len == sizeof(buffer)) len--;
    buffer[len] = '\0';
    if (buffer[len-1] == '\n') buffer[len-1] = '\0';
    nowtm = gmtime(&now.tv_sec);
    printf("%02d%02d%02d.%03d  %s\n",
      nowtm->tm_hour, nowtm->tm_min, nowtm->tm_sec,
      (int)now.tv_usec/1000, buffer);
  }
}