microcom: add new applet, this time for real

util-linux/microcom.c

@@ -0,0 +1,135 @@
+/* microcom.c
+ *
+ * bare bones 'talk to modem' program - similar to 'cu -l $device'
+ * inspired by mgetty's microcom
+ *
+ */
+#include "busybox.h"
+
+int microcom_main(int argc, char **argv);
+int microcom_main(int argc, char **argv)
+{
+	struct pollfd pfd[2];
+#define sfd (pfd[1].fd)
+	char *device_lock_file = NULL;
+	const char *s;
+	const char *opt_s = "9600";
+	unsigned speed;
+	int len;
+	int exitcode = 1;
+	struct termios tio0, tiosfd, tio;
+
+	getopt32(argv, "s:", &opt_s);
+	argc -= optind;
+	argv += optind;
+	if (!argv[0])
+		bb_show_usage();
+	speed = xatou(opt_s);
+
+	// try to create lock file in /var/lock
+	s = bb_basename(argv[0]);
+	if (!s[0]) {
+		errno = ENODEV;
+		bb_perror_msg_and_die("can't lock device");
+	}
+	device_lock_file = xasprintf("/var/lock/LCK..%s", s);
+	sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
+	if (sfd < 0) {
+		if (ENABLE_FEATURE_CLEAN_UP)
+			free(device_lock_file);
+		device_lock_file = NULL;
+		if (errno == EEXIST)
+			bb_perror_msg_and_die("can't lock device");
+		// We don't abort on other errors: /var/lock can be
+		// non-writable or non-existent
+	} else {
+		// %4d to make mgetty happy. It treats 4-bytes lock files as binary,
+		// not text, PID. Making 5+ char file. Brrr...
+		s = xasprintf("%4d\n", getpid());
+		write(sfd, s, strlen(s));
+		if (ENABLE_FEATURE_CLEAN_UP)
+			free((char*)s);
+		close(sfd);
+	}
+
+	// open device
+	sfd = open(argv[0], O_RDWR | O_NDELAY);
+	if (sfd < 0) {
+		bb_perror_msg("can't open device");
+		goto unlock_and_exit;
+	}
+	fcntl(sfd, F_SETFL, O_RDWR); // why?
+
+	// put stdin to "raw mode", handle one character at a time
+	tcgetattr(STDIN_FILENO, &tio0);
+	tio = tio0;
+	tio.c_lflag &= ~(ICANON|ECHO);
+	tio.c_iflag &= ~(IXON|ICRNL);
+	tio.c_oflag &= ~(ONLCR);
+	tio.c_cc[VMIN] = 1;
+	tio.c_cc[VTIME] = 0;
+	if (tcsetattr(STDIN_FILENO, TCSANOW, &tio)) {
+		bb_perror_msg("can't tcsetattr for %s", "stdin");
+		goto unlock_and_exit;
+	}
+
+	/* same thing for modem (plus: set baud rate) - TODO: make CLI option */
+	tcgetattr(sfd, &tiosfd);
+	tio = tiosfd;
+	tio.c_lflag &= ~(ICANON|ECHO);
+	tio.c_iflag &= ~(IXON|ICRNL);
+	tio.c_oflag &= ~(ONLCR);
+	tio.c_cc[VMIN] = 1;
+	tio.c_cc[VTIME] = 0;
+	cfsetispeed(&tio, tty_value_to_baud(speed));
+	cfsetospeed(&tio, tty_value_to_baud(speed));
+	if (tcsetattr(sfd, TCSANOW, &tio)) {
+		bb_perror_msg("can't tcsetattr for %s", "device");
+		goto unlock_and_exit;
+	}
+
+	// disable SIGINT
+	signal(SIGINT, SIG_IGN);
+
+	// drain stdin
+	tcflush(STDIN_FILENO, TCIFLUSH);
+	printf("connected to '%s' (%d bps), exit with ctrl-X...\r\n", argv[0], speed);
+
+	// main loop: check with poll(), then read/write bytes across
+	pfd[0].fd = STDIN_FILENO;
+	pfd[0].events = POLLIN;
+	/*pfd[1].fd = sfd;*/
+	pfd[1].events = POLLIN;
+	while (1) {
+		int i;
+		while (-1 == poll(pfd, 2, -1) && EINTR == errno)
+			continue;
+		for (i = 0; i < 2; ++i) {
+			if (pfd[i].revents & POLLIN) { 
+				len = read(pfd[i].fd, bb_common_bufsiz1, COMMON_BUFSIZE);
+				if (len > 0) {
+					if (!i && 24 == bb_common_bufsiz1[0])
+						goto done; // ^X exits
+					write(pfd[1-i].fd, bb_common_bufsiz1, len);
+				}
+			}
+		}
+	}
+ done:
+	tcsetattr(sfd, TCSANOW, &tiosfd);
+	tcsetattr(STDIN_FILENO, TCSANOW, &tio0);
+	tcflush(STDIN_FILENO, TCIFLUSH);
+
+	if (ENABLE_FEATURE_CLEAN_UP)
+		close(sfd);
+	exitcode = 0;
+
+ unlock_and_exit:
+	// delete lock file
+	if (device_lock_file) {
+		unlink(device_lock_file);
+		if (ENABLE_FEATURE_CLEAN_UP)
+			free(device_lock_file);
+	}
+	return exitcode;
+}