nanogui: An average accurate periodic timer
Subject:
Re: [nanogui] An average accurate periodic timer
From:
"Greg Haerr" ####@####.####
Date:
28 Aug 2002 17:08:36 -0000
Message-Id: <029501c24eb4$198ac5c0$3aba46a6@xmission.com>
: What I want from periodic timer is, although each timer event may not
: arrives accurately, the average time should be accurate. That is to
: say, there should be exactly 40 timer events come from server in 1
: second if the timer period is 25ms.
To solve this problem, perhaps the third argument to GrCreateTimer
should be the type of timer, not just a boolean for periodic or not.
I haven't yet added Alex's GrCreateTimer patch, since it changes the
API and will break existing programs. I will be adding it creating
a GrCreateTimerEx entry point, with GrCreateTimer #defined
to the new *Ex entry point.
Comments?
Regards,
Greg
:
: To solve this problem, I modify slightly the way to calculate new
: timeout value. Instead of base on current time, I calculate it base
: on old timeout value. Please see the patch below.
:
: I believe it is not of gerenal interest. But it is useful to me.
:
: Regards,
: Sheng
:
:
: --- microwin-aph/src/engine/devtimer.c Mon Apr 8 10:30:18 2002
: +++ microwin-aph-new/src/engine/devtimer.c Wed Aug 28 09:34:31 2002
: @@ -65,6 +65,7 @@
: static struct timeval current_time;
:
: static void calculate_timeval(struct timeval *tv, MWTIMEOUT to);
: +static void calculate_timeval_strict(struct timeval *tv, MWTIMEOUT to);
: static signed long time_to_expiry(struct timeval *t);
:
: MWTIMER *GdAddTimer(MWTIMEOUT timeout, MWTIMERCB callback, void *arg,
: @@ -159,7 +160,7 @@
: if(time_to_expiry(&t->timeout) <= 0) {
: t->callback(t->arg);
: if(!t->periodic) GdDestroyTimer(t);
: - else calculate_timeval(&t->timeout, t->period);
: + else calculate_timeval_strict(&t->timeout,
: t->period);
: }
: t = n;
: }
: @@ -175,6 +176,16 @@
: {
: tv->tv_sec = current_time.tv_sec + (to / 1000);
: tv->tv_usec = current_time.tv_usec + ((to % 1000) * 1000);
: + if(tv->tv_usec > 1000000) {
: + tv->tv_sec++;
: + tv->tv_usec -= 1000000;
: + }
: +}
: +
: +static void calculate_timeval_strict(struct timeval *tv, MWTIMEOUT to)
: +{
: + tv->tv_sec += (to / 1000);
: + tv->tv_usec += ((to % 1000) * 1000);
: if(tv->tv_usec > 1000000) {
: tv->tv_sec++;
: tv->tv_usec -= 1000000;
:
:
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