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/*************************************************************************
* Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com> *
* *
* This file is part of The Sandglass Library. *
* *
* The Sandglass Library is free software; you can redistribute it *
* and/or modify it under the terms of the GNU Lesser General Public *
* License as published by the Free Software Foundation; either version *
* 3 of the License, or (at your option) any later version. *
* *
* The Sandglass Library is distributed in the hope that it will be *
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty *
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public *
* License along with this program. If not, see *
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
#include "sandglass_impl.h"
#include "sandglass.h"
#include <time.h>
#include <unistd.h>
/* Gets the number of clock ticks per second */
double
sandglass_tsc_resolution()
{
static long tsc = 0;
static struct timespec ts = { .tv_sec = 0, .tv_nsec = 10000000L };
struct timespec curr, until;
if (tsc == 0) {
sandglass_get_currtime(&curr);
until = curr;
sandglass_timespec_add(&until, &ts);
tsc = sandglass_get_tsc();
/* Spin */
do {
sandglass_get_currtime(&curr);
} while (sandglass_timespec_cmp(&curr, &until) < 0);
tsc = sandglass_get_tsc() - tsc;
/* Adjust ts to the time actually waited */
sandglass_timespec_sub(&curr, &until);
sandglass_timespec_add(&ts, &curr);
}
return tsc*1.0e9/ts.tv_nsec;
}
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