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mach_gettime.h
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#ifndef MACH_GETTIME_H
#define MACH_GETTIME_H
#include <sys/types.h>
#include <sys/_types/_timespec.h>
#include <mach/mach.h>
#include <mach/clock.h>
#include <mach/mach_time.h>
/* The opengroup spec isn't clear on the mapping from REALTIME to CALENDAR
being appropriate or not.
http://pubs.opengroup.org/onlinepubs/009695299/basedefs/time.h.html */
// XXX only supports a single timer
#define TIMER_ABSTIME -1
#define CLOCK_REALTIME CALENDAR_CLOCK
#define CLOCK_MONOTONIC SYSTEM_CLOCK
#if !defined(__DARWIN_C_LEVEL) || __DARWIN_C_LEVEL < 199309L
typedef int clockid_t;
#endif
/* the mach kernel uses struct mach_timespec, so struct timespec
is loaded from <sys/_types/_timespec.h> for compatibility */
// struct timespec { time_t tv_sec; long tv_nsec; };
int clock_gettime(clockid_t clk_id, struct timespec *tp);
#include <mach/mach_time.h>
#define MT_NANO (+1.0E-9)
#define MT_GIGA UINT64_C(1000000000)
// TODO create a list of timers,
static double mt_timebase = 0.0;
static uint64_t mt_timestart = 0;
// TODO be more careful in a multithreaded environment
int clock_gettime(clockid_t clk_id, struct timespec *tp)
{
kern_return_t retval = KERN_SUCCESS;
if( clk_id == TIMER_ABSTIME)
{
if (!mt_timestart) { // only one timer, initialized on the first call to the TIMER
mach_timebase_info_data_t tb = { 0 };
mach_timebase_info(&tb);
mt_timebase = tb.numer;
mt_timebase /= tb.denom;
mt_timestart = mach_absolute_time();
}
double diff = (mach_absolute_time() - mt_timestart) * mt_timebase;
tp->tv_sec = diff * MT_NANO;
tp->tv_nsec = diff - (tp->tv_sec * MT_GIGA);
}
else // other clk_ids are mapped to the corresponding mach clock_service
{
clock_serv_t cclock;
mach_timespec_t mts;
host_get_clock_service(mach_host_self(), clk_id, &cclock);
retval = clock_get_time(cclock, &mts);
mach_port_deallocate(mach_task_self(), cclock);
tp->tv_sec = mts.tv_sec;
tp->tv_nsec = mts.tv_nsec;
}
return retval;
}
#endif
clockid_t
int clockid_t
Definition mach_gettime.h:20
clock_gettime
int clock_gettime(clockid_t clk_id, struct timespec *tp)
Definition mach_gettime.h:39
MT_NANO
#define MT_NANO
Definition mach_gettime.h:31
MT_GIGA
#define MT_GIGA
Definition mach_gettime.h:32
TIMER_ABSTIME
#define TIMER_ABSTIME
Definition mach_gettime.h:15