/*
 * Copyright 2012 Digital Aggregates Corporation, Colorado, USA.
 * Licensed under the terms of your choice of the GPL.
 * Chip Overclock <coverclock@diag.com>
 */

#include <stdio.h>
#include <signal.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <errno.h>

static void handler(int signum) {
	fprintf(stderr, "signal %d!\n", signum);
}

int main(void) {
	int fd;
	struct termios tios;
	struct sigaction action;
	sigset_t set;
	sigset_t was;
	struct itimerval timer;
	struct itimerval remaining;
	char buffer[32];

	/* Configure serial port. */

	if ((fd = open("/dev/ttyS2", O_RDWR)) < 0) {
		perror("open");
		return 1;
	}

	if (!isatty(fd)) {
		errno = EINVAL;
		perror("isatty");
		return 1;
	}

	if (tcgetattr(fd, &tios) < 0) {
		perror("tcgetattr");
		return 1;
	}

#if 1
	tios.c_cc[VTIME] = 1;
	tios.c_cc[VMIN] = 32;
#endif

	if (tcsetattr(fd, TCSANOW, &tios) < 0) {
		perror("tcsetattr");
		return 1;
	}

	/* Install alarm signal handler. */

	if (sigaction(SIGALRM, (const struct sigaction *) 0, &action)) {
		perror("sigaction");
		return 1;
	}

	action.sa_handler = handler;
	action.sa_flags &= ~SA_RESTART;

	if (sigaction(SIGALRM, &action, (struct sigaction *) 0) < 0) {
		perror("sigaction");
		return 1;
	}

	/* Insure that SIGALRM is not blocked. */

	if (sigemptyset(&set) < 0) {
		perror("sigemptyset");
		return 1;
	}

	if (sigaddset(&set, SIGALRM) < 0) {
		perror("sigaddset");
		return 1;
	}

	if (sigprocmask(SIG_UNBLOCK, &set, (sigset_t *) 0) < 0) {
		perror("sigprocmask");
		return 1;
	}

	/* Start an one-shot interval timer. */

	timer.it_value.tv_sec = 5;
	timer.it_value.tv_usec = 0;

	timer.it_interval.tv_sec = 0;
	timer.it_interval.tv_usec = 0;

	if (setitimer(ITIMER_REAL, &timer, &remaining) < 0) {
		perror("setitimer");
		return 1;
	}

	/* Block on a read. */

	if (read(fd, buffer, sizeof(buffer)) < 0) {
		perror("read");
		return 1;
	}

	return 0;
}