lib/libc/sys-minix/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                 return EFAULT;
  31
  32         if (rqtp->tv_sec < 0 ||
  33                 rqtp->tv_nsec < 0 ||
  34                 rqtp->tv_nsec >= NSEC_PER_SEC)
  35                 return EINVAL;
  36
  37         /* store *rqtp to make sure it is not overwritten */
  38         rqt = *rqtp;
  39
  40         /* keep track of start time if needed */
  41         if (rmtp)
  42         {
  43                 rmtp->tv_sec = 0;
  44                 rmtp->tv_nsec = 0;
  45                 if (gettimeofday(&timestart, NULL) < 0)
  46                         return -1;
  47         }
  48
  49         /* use select to wait */
  50         timeout.tv_sec = rqt.tv_sec;
  51         timeout.tv_usec = (rqt.tv_nsec + NSEC_PER_USEC - 1) / NSEC_PER_USEC;
  52         r = select(0, NULL, NULL, NULL, &timeout);
  53
  54         /* return remaining time only if requested */
  55         /* if select succeeded then we slept all time */
  56         if (!rmtp || r >= 0)
  57                 return r;
  58
  59         /* measure end time; preserve errno */
  60         errno_select = errno;
  61         if (gettimeofday(&timeend, NULL) < 0)
  62                 return -1;
  63
  64         errno = errno_select;
  65
  66         /* compute remaining time */
  67         rmtp->tv_sec = rqt.tv_sec - (timeend.tv_sec - timestart.tv_sec);
  68         rmtp->tv_nsec = rqt.tv_nsec - (timeend.tv_usec - timestart.tv_usec) * NSEC_PER_USEC;
  69
  70         /* bring remaining time into canonical form */
  71         while (rmtp->tv_nsec < 0)
  72         {
  73                 rmtp->tv_sec -= 1;
  74                 rmtp->tv_nsec += NSEC_PER_SEC;
  75         }
  76
  77         while (rmtp->tv_nsec > NSEC_PER_SEC)
  78         {
  79                 rmtp->tv_sec += 1;
  80                 rmtp->tv_nsec -= NSEC_PER_SEC;
  81         }
  82
  83         /* remaining time must not be negative */
  84         if (rmtp->tv_sec < 0)
  85         {
  86                 rmtp->tv_sec = 0;
  87                 rmtp->tv_nsec = 0;
  88         }
  89
  90         return r;
  91 }
  92
  93
  94 #if defined(__minix) && defined(__weak_alias)
  95 __weak_alias(nanosleep, __nanosleep50)
  96 #endif