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/*
* Precise timer routines using Mach kernel-space timing.
*
* It reports to be accurate by ~20us, unless the task is preempted.
*
* (C) 2003 Dan Christiansen
*
* Released into the public domain.
*/
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <mach/mach_time.h>
#include <mach/mach.h>
#include <mach/clock.h>
#include "../config.h"
#include "../mp_msg.h"
#include "timer.h"
/* Utility macros for mach_timespec_t - it uses nsec rather than usec */
/* returns time from t1 to t2, in seconds (as float) */
#define diff_time(t1, t2) \
(((t2).tv_sec - (t1).tv_sec) + \
((t2).tv_nsec - (t1).tv_nsec) / 1e9)
/* returns time from t1 to t2, in microseconds (as integer) */
#define udiff_time(t1, t2) \
(((t2).tv_sec - (t1).tv_sec) * 1000000 + \
((t2).tv_nsec - (t1).tv_nsec) / 1000)
/* returns float value of t, in seconds */
#define time_to_float(t) \
((t).tv_sec + (t).tv_nsec / 1e9)
/* returns integer value of t, in microseconds */
#define time_to_usec(t) \
((t).tv_sec * 1000000 + (t).tv_nsec / 1000)
/* sets ts to the value of f, in seconds */
#define float_to_time(f, ts) \
do { \
(ts).tv_sec = (unsigned int)(f); \
(ts).tv_nsec = (int)(((f) - (ts).sec) / 1000000000.0); \
} while (0)
/* sets ts to the value of i, in microseconds */
#define usec_to_time(i, ts) \
do { \
(ts).tv_sec = (i) / 1000000; \
(ts).tv_nsec = (i) % 1000000 * 1000; \
} while (0)
#define time_uadd(i, ts) \
do { \
(ts).tv_sec += (i) / 1000000; \
(ts).tv_nsec += (i) % 1000000 * 1000; \
while ((ts).tv_nsec > 1000000000) { \
(ts).tv_sec++; \
(ts).tv_nsec -= 1000000000; \
} \
} while (0)
/* global variables */
static double relative_time, startup_time;
static double timebase_ratio;
static mach_port_t clock_port;
/* sleep usec_delay microseconds */
int usec_sleep(int usec_delay)
{
mach_timespec_t start_time, end_time;
clock_get_time(clock_port, &start_time);
end_time = start_time;
time_uadd(usec_delay, end_time);
clock_sleep(clock_port, TIME_ABSOLUTE, end_time, NULL);
clock_get_time(clock_port, &end_time);
return usec_delay - udiff_time(start_time, end_time);
}
/* Returns current time in microseconds */
unsigned int GetTimer()
{
return (unsigned int)((mach_absolute_time() * timebase_ratio - startup_time)
* 1e6);
}
/* Returns current time in milliseconds */
unsigned int GetTimerMS()
{
return (unsigned int)(GetTimer() / 1000);
}
/* Returns time spent between now and last call in seconds */
float GetRelativeTime()
{
double last_time;
last_time = relative_time;
relative_time = mach_absolute_time() * timebase_ratio;
return (float)(relative_time-last_time);
}
/* Initialize timer, must be called at least once at start */
void InitTimer()
{
struct mach_timebase_info timebase;
/* get base for mach_absolute_time() */
mach_timebase_info(&timebase);
timebase_ratio = (double)timebase.numer / (double)timebase.denom
* (double)1e-9;
/* get mach port for the clock */
host_get_clock_service(mach_host_self(), REALTIME_CLOCK, &clock_port);
/* prepare for GetRelativeTime() */
relative_time = startup_time =
(double)(mach_absolute_time() * timebase_ratio);
}
#if 0
int main()
{
const long delay = 0.001*1e6;
const unsigned short attempts = 100;
int i,j[attempts],t[attempts],r[attempts];
double sqtotal;
double total;
InitTimer();
for (i = 0; i < attempts; i++) {
t[i] = j[i] = GetTimer();
r[i] = usec_sleep(delay);
j[i] = delay-(GetTimer() - j[i]);
fflush(stdout);
}
for (i = 0; i < attempts; i++) {
sqtotal += j[i]*j[i];
total += j[i];
printf("%2i=%0.06g \tr: %9i\tj: %9i\tr - j:%9i\n",
i, t[i] / 1e6, r[i], j[i], r[i] - j[i]);
}
printf("attempts: %i\ttotal=%g\trms=%g\tavg=%g\n", attempts, total,
sqrt(sqtotal/attempts),total/attempts);
return 0;
}
#endif
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