+double
+wtimer_elapsed (struct wget_timer *wt)
+{
+ wget_sys_time now;
+ double elapsed;
+
+ wtimer_sys_set (&now);
+ elapsed = wt->elapsed_pre_start + wtimer_sys_diff (&now, &wt->start);
+
+ /* Ideally we'd just return the difference between NOW and
+ wt->start. However, the system timer can be set back, and we
+ could return a value smaller than when we were last called, even
+ a negative value. Both of these would confuse the callers, which
+ expect us to return monotonically nondecreasing values.
+
+ Therefore: if ELAPSED is smaller than its previous known value,
+ we reset wt->start to the current time and effectively start
+ measuring from this point. But since we don't want the elapsed
+ value to start from zero, we set elapsed_pre_start to the last
+ elapsed time and increment all future calculations by that
+ amount. */
+
+ if (elapsed < wt->elapsed_last)
+ {
+ wt->start = now;
+ wt->elapsed_pre_start = wt->elapsed_last;
+ elapsed = wt->elapsed_last;
+ }
+
+ wt->elapsed_last = elapsed;
+ return elapsed;
+}
+
+/* Return the assessed granularity of the timer implementation, in
+ milliseconds. This is used by code that tries to substitute a
+ better value for timers that have returned zero. */
+
+double