#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/select.h>
#include <fcntl.h>    // File control definitions
#include <termios.h>  // Posix terminal control definitions
#include <unistd.h>   // close()

#define SIZEOF_ARRAY(array) (sizeof(array)/sizeof(array[0]))

int OpenSerial(const char *dev)
{
  int fd;
  struct termios serdev;

  fd = open(dev, O_RDWR | O_NOCTTY | O_NONBLOCK);
  if (fd == -1) {
    return -1;
  }
  
  tcgetattr(fd, &serdev);
  
  // Set the Baud Rate (115200)
  cfsetispeed(&serdev, B115200);
  cfsetospeed(&serdev, B115200);
  
  // Enable receiver
  serdev.c_cflag |= (CLOCAL | CREAD);
  
  // Set the parity (NONE)
  serdev.c_cflag &= ~(PARENB | PARODD);
  serdev.c_iflag &= ~(INPCK | ISTRIP | IGNPAR | PARMRK);
  
  // Set the stop bits (1)
  serdev.c_cflag &= ~CSTOPB;
  
  // Set the databits (8)
  serdev.c_cflag &= ~CSIZE;
  serdev.c_cflag |= CS8;
  
  // Set the flow control (RTS/CTS). No SW Handshake
  serdev.c_cflag |= CRTSCTS;
  serdev.c_iflag &= ~(IXON | IXOFF | IXANY);
  
  // Set everything else
  serdev.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);  // Raw input
  serdev.c_oflag &= ~OPOST;                           // Raw output
  serdev.c_cc[VMIN] = 0;
  serdev.c_cc[VTIME] = 2;
  tcsetattr(fd, TCSANOW, &serdev);

  fcntl(fd, F_SETFL, 0);
  return fd;
}

int WriteSerial(int fd, const char *buff, size_t len, size_t *off)
{
  ssize_t r;

  if (*off >= len) return -1;
  printf("Writing\n");
  r = write(fd, buff+ *off, len - *off);
  printf("Written %d\n", r);
  if (r < 0) return -2;
  *off += r;
  return r;
}

int main(void)
{
  char writestr[] = "This is a test. We're testing Cygwin writes\n";
  size_t off = 0;
  int fdSerial;
  int result;
  fd_set setRead;
  fd_set setWrite;

  fdSerial = OpenSerial("/dev/com2");
  if (fdSerial < 0) return EXIT_FAILURE;

  for (;;) {
    FD_ZERO(&setRead);
    FD_ZERO(&setWrite);
    FD_SET(fdSerial, &setWrite);
    result = select(fdSerial+1, &setRead, &setWrite, NULL, NULL);
    if (result < 0) {
      printf("Select() returned error\n");
      close(fdSerial);
      return EXIT_FAILURE;
    }
    if (FD_ISSET(fdSerial, &setWrite)) {
      WriteSerial(fdSerial, writestr, SIZEOF_ARRAY(writestr)-1, &off);
      if (off == SIZEOF_ARRAY(writestr)-1) off = 0;
    }
  }
}