minix/lib/posix/_nanosleep.c

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/* nanosleep() - Sleep for a number of seconds. Author: Erik van der Kouwe
* 25 July 2009
*/
#include <lib.h>
#define nanosleep _nanosleep
#include <unistd.h>
#include <errno.h>
#include <time.h>
#include <sys/select.h>
#include <sys/time.h>
#define MSEC_PER_SEC 1000
#define USEC_PER_MSEC 1000
#define NSEC_PER_USEC 1000
#define USEC_PER_SEC (USEC_PER_MSEC * MSEC_PER_SEC)
#define NSEC_PER_SEC (NSEC_PER_USEC * USEC_PER_SEC)
int nanosleep(const struct timespec *rqtp, struct timespec *rmtp)
{
struct timeval timeout, timestart = { 0, 0 }, timeend;
int errno_select, r;
struct timespec rqt;
/* check parameters */
if (!rqtp)
return EFAULT;
if (rqtp->tv_sec < 0 ||
rqtp->tv_nsec < 0 ||
rqtp->tv_nsec >= NSEC_PER_SEC)
return EINVAL;
/* store *rqtp to make sure it is not overwritten */
rqt = *rqtp;
/* keep track of start time if needed */
if (rmtp)
{
rmtp->tv_sec = 0;
rmtp->tv_nsec = 0;
if (gettimeofday(&timestart, NULL) < 0)
return -1;
}
/* use select to wait */
timeout.tv_sec = rqt.tv_sec;
timeout.tv_usec = (rqt.tv_nsec + NSEC_PER_USEC - 1) / NSEC_PER_USEC;
r = select(0, NULL, NULL, NULL, &timeout);
/* return remaining time only if requested */
/* if select succeeded then we slept all time */
if (!rmtp || r >= 0)
return r;
/* measure end time; preserve errno */
errno_select = errno;
if (gettimeofday(&timeend, NULL) < 0)
return -1;
errno = errno_select;
/* compute remaining time */
rmtp->tv_sec = rqt.tv_sec - (timeend.tv_sec - timestart.tv_sec);
rmtp->tv_nsec = rqt.tv_nsec - (timeend.tv_usec - timestart.tv_usec) * NSEC_PER_USEC;
/* bring remaining time into canonical form */
while (rmtp->tv_nsec < 0)
{
rmtp->tv_sec -= 1;
rmtp->tv_nsec += NSEC_PER_SEC;
}
while (rmtp->tv_nsec > NSEC_PER_SEC)
{
rmtp->tv_sec += 1;
rmtp->tv_nsec -= NSEC_PER_SEC;
}
/* remaining time must not be negative */
if (rmtp->tv_sec < 0)
{
rmtp->tv_sec = 0;
rmtp->tv_nsec = 0;
}
return r;
}