ptimer_destroy -- destroy the timer.
ptimer_granularity -- returns the approximate granularity of the timers.
- Timers operate in milliseconds, but return floating point values
- that can be more precise. For example, to measure the time it
- takes to run a loop, you can use something like:
+ Timers measure time in milliseconds, but the timings they return
+ are floating point numbers, so they can carry as much precision as
+ the underlying system timer supports. For example, to measure the
+ time it takes to run a loop, you can use something like:
ptimer *tmr = ptimer_new ();
while (...)
/* The code below this point is independent of timer implementation. */
struct ptimer {
- /* Whether the start time has been set. */
- int initialized;
-
/* The starting point in time which, subtracted from the current
time, yields elapsed time. */
ptimer_system_time start;
struct ptimer *
ptimer_new (void)
{
- struct ptimer *wt = xnew0 (struct ptimer);
+ struct ptimer *pt = xnew0 (struct ptimer);
#ifdef IMPL_init
static int init_done;
if (!init_done)
IMPL_init ();
}
#endif
- ptimer_reset (wt);
- return wt;
+ ptimer_reset (pt);
+ return pt;
}
/* Free the resources associated with the timer. Its further use is
prohibited. */
void
-ptimer_destroy (struct ptimer *wt)
+ptimer_destroy (struct ptimer *pt)
{
- xfree (wt);
+ xfree (pt);
}
-/* Reset timer WT. This establishes the starting point from which
+/* Reset timer PT. This establishes the starting point from which
ptimer_read() will return the number of elapsed milliseconds.
It is allowed to reset a previously used timer. */
void
-ptimer_reset (struct ptimer *wt)
+ptimer_reset (struct ptimer *pt)
{
/* Set the start time to the current time. */
- IMPL_measure (&wt->start);
- wt->elapsed_last = 0;
- wt->elapsed_pre_start = 0;
- wt->initialized = 1;
+ IMPL_measure (&pt->start);
+ pt->elapsed_last = 0;
+ pt->elapsed_pre_start = 0;
}
/* Measure the elapsed time since timer creation/reset and return it
ignored. */
double
-ptimer_measure (struct ptimer *wt)
+ptimer_measure (struct ptimer *pt)
{
ptimer_system_time now;
double elapsed;
- assert (wt->initialized != 0);
-
IMPL_measure (&now);
- elapsed = wt->elapsed_pre_start + IMPL_diff (&now, &wt->start);
+ elapsed = pt->elapsed_pre_start + IMPL_diff (&now, &pt->start);
/* Ideally we'd just return the difference between NOW and
- wt->start. However, the system timer can be set back, and we
+ pt->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
+ we reset pt->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
This cannot happen with Windows and POSIX monotonic/highres
timers, but the check is not expensive. */
- if (elapsed < wt->elapsed_last)
+ if (elapsed < pt->elapsed_last)
{
- wt->start = now;
- wt->elapsed_pre_start = wt->elapsed_last;
- elapsed = wt->elapsed_last;
+ pt->start = now;
+ pt->elapsed_pre_start = pt->elapsed_last;
+ elapsed = pt->elapsed_last;
}
- wt->elapsed_last = elapsed;
+ pt->elapsed_last = elapsed;
return elapsed;
}
ptimer_reset and the last call to ptimer_update. */
double
-ptimer_read (const struct ptimer *wt)
+ptimer_read (const struct ptimer *pt)
{
- return wt->elapsed_last;
+ return pt->elapsed_last;
}
/* Return the assessed resolution of the timer implementation, in