watcher: Add a method to query the watcher state

This allows a user to check if the watcher is actually running, and potentially
perform read operations directly instead of relying on watcher.

src/libstrongswan/processing/watcher.h

@@ -23,6 +23,7 @@
 
 typedef struct watcher_t watcher_t;
 typedef enum watcher_event_t watcher_event_t;
+typedef enum watcher_state_t watcher_state_t;
 
 #include <library.h>
 
@@ -56,6 +57,18 @@ enum watcher_event_t {
 	WATCHER_EXCEPT = (1<<2),
 };
 
+/**
+ * State the watcher currently is in
+ */
+enum watcher_state_t {
+	/** no watcher thread running or queued */
+	WATCHER_STOPPED = 0,
+	/** a job has been queued for watching, but not yet started */
+	WATCHER_QUEUED,
+	/** a watcher thread is active, dispatching socket events */
+	WATCHER_RUNNING,
+};
+
 /**
  * Watch multiple file descriptors using select().
  */
@@ -85,6 +98,13 @@ struct watcher_t {
 	 */
 	void (*remove)(watcher_t *this, int fd);
 
+	/**
+	 * Get the current watcher state
+	 *
+	 * @reutrn			currently active watcher state
+	 */
+	watcher_state_t (*get_state)(watcher_t *this);
+
 	/**
 	 * Destroy a watcher_t.
 	 */