Introduce time_offset() helper and replace open-coded versions in timer.c

This function takes a struct timeval and offsets it by a (potentially fractional)
number of seconds, given as a 'double'.

include/ircaux.h

@@ -74,6 +74,7 @@ double 	BX_time_diff 		(struct timeval, struct timeval);
 double time_since(const struct timeval *tv_from);
 double time_until(const struct timeval *tv_to);
 int time_cmp(const struct timeval *a, const struct timeval *b);
+struct timeval *time_offset(struct timeval *tv, double offset);
 char *	BX_plural 			(int);
 int	BX_time_to_next_minute 	(void);
 char *	BX_remove_trailing_spaces 	(char *);

source/ircaux.c

@@ -1747,6 +1747,26 @@ int time_cmp(const struct timeval *a, const struct timeval *b)
 		return (a->tv_sec > b->tv_sec) - (a->tv_sec < b->tv_sec);
 }
 
+/* Add an offset, in seconds, to a timeval */
+struct timeval *time_offset(struct timeval *tv, double offset)
+{
+	time_t seconds = offset;		/* Discards fractional part */
+
+	offset -= seconds;
+	if (offset < 0.0)
+	{
+		/* This ensures we never make tv_usec go negative, since it might be unsigned. */
+		offset += 1.0;
+		seconds -= 1;
+	}
+	tv->tv_usec += offset * 1000000.0;
+	seconds += tv->tv_usec / 1000000;
+	tv->tv_usec %= 1000000;
+	tv->tv_sec += seconds;
+
+	return tv;
+}
+
 int BX_time_to_next_minute (void)
 {
 	time_t now = time(NULL);

source/timer.c

@@ -231,18 +231,7 @@ extern	void ExecuteTimers (void)
 				current->events--;
 			case -1:
 				{
-#if 1
+					time_offset(&current->time, current->interval);
-				double milli, seconds;
-				milli = current->interval * 1000 * 1000 + current->time.tv_usec;
-				seconds = current->time.tv_sec + (milli / 1000000);
-				milli = ((unsigned long)current) % 1000000;
-				current->time.tv_sec = seconds;
-				current->time.tv_usec = milli;
-#else
-				current->time.tv_usec += (current->interval * 1000);
-				current->time.tv_sec += (current->time.tv_usec / 1000000);
-				current->time.tv_usec %= 1000000;
-#endif
 					schedule_timer(current);
 					break;	
 				}
@@ -464,24 +453,11 @@ char *BX_add_timer(int update, char *refnum_want, double when, long events, int
 {
 	TimerList	*ntimer, *otimer = NULL;
 	char		refnum_got[REFNUM_MAX+1] = "";
-	double		seconds = 0.0, milli = 0.0;	
-extern	double		fmod(double, double);
 	
 	ntimer = (TimerList *) new_malloc(sizeof(TimerList));
 
 	get_time(&ntimer->time);
-#if 1
+	time_offset(&ntimer->time, when / 1000.0);
-	milli = when * 1000 + ntimer->time.tv_usec;
-	seconds = ntimer->time.tv_sec + (milli / 1000000);
-
-	milli = ((unsigned long)milli) % 1000000;
-	ntimer->time.tv_sec = seconds;
-	ntimer->time.tv_usec = milli;
-#else
-	ntimer->time.tv_usec += (unsigned long)when;
-	ntimer->time.tv_sec += ((when + ntimer->time.tv_usec) / 1000);
-	ntimer->time.tv_usec %= 1000;
-#endif
 
 	ntimer->interval = when / 1000;
 	ntimer->events = events;