minix/lib/libsys/clock_time.c

   1
   2 #include "sysutil.h"
   3 #include <sys/time.h>
   4
   5 /*
   6  * This routine returns the time in seconds since 1.1.1970.  MINIX is an
   7  * astrophysically naive system that assumes the earth rotates at a constant
   8  * rate and that such things as leap seconds do not exist.  If a non-NULL
   9  * pointer to a timespec structure is given, that structure is filled with
  10  * the current time in subsecond precision.
  11  */
  12 time_t
  13 clock_time(struct timespec *tv)
  14 {
  15         struct minix_kerninfo *minix_kerninfo;
  16         uint32_t system_hz;
  17         clock_t realtime;
  18         time_t boottime, sec;
  19
  20         minix_kerninfo = get_minix_kerninfo();
  21
  22         /* We assume atomic 32-bit field retrieval.  TODO: 64-bit support. */
  23         boottime = minix_kerninfo->kclockinfo->boottime;
  24         realtime = minix_kerninfo->kclockinfo->realtime;
  25         system_hz = minix_kerninfo->kclockinfo->hz;
  26
  27         sec = boottime + realtime / system_hz;
  28
  29         if (tv != NULL) {
  30                 tv->tv_sec = sec;
  31
  32                 /*
  33                  * We do not want to overflow, and system_hz can be as high as
  34                  * 50kHz.
  35                  */
  36                 if (system_hz < LONG_MAX / 40000)
  37                         tv->tv_nsec = (realtime % system_hz) * 40000 /
  38                             system_hz * 25000;
  39                 else
  40                         tv->tv_nsec = 0;        /* bad, but what's better? */
  41         }
  42
  43         return sec;
  44 }