Add a function to query the state of the serial lines.

src/serial.h

@@ -46,6 +46,13 @@ typedef enum serial_queue_t {
 	SERIAL_QUEUE_BOTH = SERIAL_QUEUE_INPUT | SERIAL_QUEUE_OUTPUT
 } serial_queue_t;
 
+typedef enum serial_line_t {
+	SERIAL_LINE_DCD, // Data carrier detect
+	SERIAL_LINE_CTS, // Clear to send
+	SERIAL_LINE_DSR, // Data set ready
+	SERIAL_LINE_RNG, // Ring indicator
+} serial_line_t;
+
 int serial_errcode (void);
 const char* serial_errmsg (void);
 
@@ -96,6 +103,8 @@ int serial_set_rts (serial_t *device, int level);
 int serial_get_received (serial_t *device);
 int serial_get_transmitted (serial_t *device);
 
+int serial_get_line (serial_t *device, int line);
+
 int serial_sleep (unsigned long timeout /* milliseconds */);
 
 int serial_timer (void);

src/serial_posix.c

@@ -670,6 +670,35 @@ serial_get_transmitted (serial_t *device)
 }
 
 
+int
+serial_get_line (serial_t *device, int line)
+{
+	if (device == NULL)
+		return -1; // EINVAL (Invalid argument)
+
+	int status = 0;
+	if (ioctl (device->fd, TIOCMGET, &status) != 0) {
+		TRACE ("ioctl");
+		return -1;
+	}
+
+	switch (line) {
+	case SERIAL_LINE_DCD:
+		return (status & TIOCM_CAR) == TIOCM_CAR;
+	case SERIAL_LINE_CTS:
+		return (status & TIOCM_CTS) == TIOCM_CTS;
+	case SERIAL_LINE_DSR:
+		return (status & TIOCM_DSR) == TIOCM_DSR;
+	case SERIAL_LINE_RNG:
+		return (status & TIOCM_RNG) == TIOCM_RNG;
+	default:
+		return -1;
+	}
+
+	return 0;
+}
+
+
 int
 serial_sleep (unsigned long timeout)
 {

src/serial_win32.c

@@ -529,6 +529,35 @@ serial_get_transmitted (serial_t *device)
 }
 
 
+int
+serial_get_line (serial_t *device, int line)
+{
+	if (device == NULL)
+		return -1; // ERROR_INVALID_PARAMETER (The parameter is incorrect)
+
+	DWORD stats = 0;
+	if (!GetCommModemStatus (device->hFile, &stats)) {
+		TRACE ("GetCommModemStatus");
+		return -1;
+	}
+
+	switch (line) {
+	case SERIAL_LINE_DCD:
+		return (stats & MS_RLSD_ON) == MS_RLSD_ON;
+	case SERIAL_LINE_CTS:
+		return (stats & MS_CTS_ON) == MS_CTS_ON;
+	case SERIAL_LINE_DSR:
+		return (stats & MS_DSR_ON) == MS_DSR_ON;
+	case SERIAL_LINE_RNG:
+		return (stats & MS_RING_ON) == MS_RING_ON;
+	default:
+		return -1;
+	}
+
+	return 0;
+}
+
+
 int
 serial_sleep (unsigned long timeout)
 {