minix/lib/libc/sys/nanosleep.c

   1 /*      nanosleep() - Sleep for a number of seconds.    Author: Erik van der Kouwe
   2  *                                                              25 July 2009
   3  */
   4
   5 #include <sys/cdefs.h>
   6 #include "namespace.h"
   7 #include <lib.h>
   8
   9 #include <unistd.h>
  10 #include <errno.h>
  11 #include <time.h>
  12 #include <sys/select.h>
  13 #include <sys/time.h>
  14
  15 #define MSEC_PER_SEC 1000
  16 #define USEC_PER_MSEC 1000
  17 #define NSEC_PER_USEC 1000
  18
  19 #define USEC_PER_SEC (USEC_PER_MSEC * MSEC_PER_SEC)
  20 #define NSEC_PER_SEC (NSEC_PER_USEC * USEC_PER_SEC)
  21
  22 int nanosleep(const struct timespec *rqtp, struct timespec *rmtp)
  23 {
  24         struct timeval timeout, timestart = { 0, 0 }, timeend;
  25         int errno_select, r;
  26         struct timespec rqt;
  27
  28         /* check parameters */
  29         if (!rqtp) {
  30                 errno = EFAULT;
  31                 return -1;
  32         }
  33
  34         if (rqtp->tv_sec < 0 ||
  35                 rqtp->tv_nsec < 0 ||
  36                 rqtp->tv_nsec >= NSEC_PER_SEC) {
  37                 errno = EINVAL;
  38                 return -1;
  39         }
  40
  41         /* store *rqtp to make sure it is not overwritten */
  42         rqt = *rqtp;
  43
  44         /* keep track of start time if needed */
  45         if (rmtp)
  46         {
  47                 rmtp->tv_sec = 0;
  48                 rmtp->tv_nsec = 0;
  49                 if (gettimeofday(&timestart, NULL) < 0)
  50                         return -1;
  51         }
  52
  53         /* use select to wait */
  54         timeout.tv_sec = rqt.tv_sec;
  55         timeout.tv_usec = (rqt.tv_nsec + NSEC_PER_USEC - 1) / NSEC_PER_USEC;
  56         r = select(0, NULL, NULL, NULL, &timeout);
  57
  58         /* return remaining time only if requested */
  59         /* if select succeeded then we slept all time */
  60         if (!rmtp || r >= 0)
  61                 return r;
  62
  63         /* measure end time; preserve errno */
  64         errno_select = errno;
  65         if (gettimeofday(&timeend, NULL) < 0)
  66                 return -1;
  67
  68         errno = errno_select;
  69
  70         /* compute remaining time */
  71         rmtp->tv_sec = rqt.tv_sec - (timeend.tv_sec - timestart.tv_sec);
  72         rmtp->tv_nsec = rqt.tv_nsec - (timeend.tv_usec - timestart.tv_usec) * NSEC_PER_USEC;
  73
  74         /* bring remaining time into canonical form */
  75         while (rmtp->tv_nsec < 0)
  76         {
  77                 rmtp->tv_sec -= 1;
  78                 rmtp->tv_nsec += NSEC_PER_SEC;
  79         }
  80
  81         while (rmtp->tv_nsec > NSEC_PER_SEC)
  82         {
  83                 rmtp->tv_sec += 1;
  84                 rmtp->tv_nsec -= NSEC_PER_SEC;
  85         }
  86
  87         /* remaining time must not be negative */
  88         if (rmtp->tv_sec < 0)
  89         {
  90                 rmtp->tv_sec = 0;
  91                 rmtp->tv_nsec = 0;
  92         }
  93
  94         return r;
  95 }
  96
  97
  98 #if defined(__minix) && defined(__weak_alias)
  99 __weak_alias(nanosleep, __nanosleep50)
 100 #endif