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