Expose our cached gettimeofday value with a new interface

I've got a two use case that wants this for a fairly sensible purpose:
one external and on internal.

event.c

@@ -180,6 +180,22 @@ gettime(struct event_base *base, struct timeval *tp)
 	return (evutil_gettimeofday(tp, NULL));
 }
 
+int
+event_base_gettimeofday_cached(struct event_base *base, struct timeval *tv)
+{
+	int r;
+	if (!base) {
+		base = current_base;
+		if (!current_base)
+			return evutil_gettimeofday(tv, NULL);
+	}
+
+	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
+	r = gettime(base, tv);
+	EVBASE_RELEASE_LOCK(base, th_base_lock);
+	return r;
+}
+
 static inline void
 clear_time_cache(struct event_base *base)
 {

include/event2/event.h

@@ -671,6 +671,20 @@ void event_set_mem_functions(void *(*malloc_fn)(size_t sz),
 
 void event_base_dump_events(struct event_base *, FILE *);
 
+/** Sets 'tv' to the current time (as returned by gettimeofday()),
+    looking at the cached value in 'base' if possible, and calling
+    gettimeofday() or clock_gettime() as appropriate if there is no
+    cached time.
+
+    Generally, this value will only be cached while actually
+    processing event callbacks, and may be very inaccuate if your
+    callbacks take a long time to execute.
+
+    Returns 0 on success, negative on failure.
+ */
+int event_base_gettimeofday_cached(struct event_base *base,
+    struct timeval *tv);
+
 #ifdef __cplusplus
 }
 #endif