sysdeps/mach/hurd/getitimer.c

   1 /* Copyright (C) 1994, 1995, 1997 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <stddef.h>
  20 #include <errno.h>
  21 #include <sys/time.h>
  22 #include <hurd.h>
  23
  24 /* XXX Temporary cheezoid implementation; see __setitmr.c.  */
  25
  26 /* These are defined in __setitmr.c.  */
  27 extern spin_lock_t _hurd_itimer_lock;
  28 extern struct itimerval _hurd_itimerval;
  29 extern struct timeval _hurd_itimer_started;
  30
  31 static inline void
  32 subtract_timeval (struct timeval *from, const struct timeval *subtract)
  33 {
  34   from->tv_usec -= subtract->tv_usec;
  35   from->tv_sec -= subtract->tv_sec;
  36   while (from->tv_usec < 0)
  37     {
  38       --from->tv_sec;
  39       from->tv_usec += 1000000;
  40     }
  41 }
  42
  43 /* Set *VALUE to the current setting of timer WHICH.
  44    Return 0 on success, -1 on errors.  */
  45 int
  46 __getitimer (which, value)
  47      enum __itimer_which which;
  48      struct itimerval *value;
  49 {
  50   struct itimerval val;
  51   struct timeval elapsed;
  52
  53   switch (which)
  54     {
  55     default:
  56       return __hurd_fail (EINVAL);
  57
  58     case ITIMER_VIRTUAL:
  59     case ITIMER_PROF:
  60       return __hurd_fail (ENOSYS);
  61
  62     case ITIMER_REAL:
  63       break;
  64     }
  65
  66   /* Get the time now.  */
  67   if (__gettimeofday (&elapsed, NULL) < 0)
  68     return -1;
  69
  70   /* Extract the current timer setting; and the time it was set, so we can
  71      calculate the time elapsed so far.  */
  72   HURD_CRITICAL_BEGIN;
  73   __spin_lock (&_hurd_itimer_lock);
  74   val = _hurd_itimerval;
  75   subtract_timeval (&elapsed, &_hurd_itimer_started);
  76   __spin_unlock (&_hurd_itimer_lock);
  77   HURD_CRITICAL_END;
  78
  79   if ((val.it_value.tv_sec | val.it_value.tv_usec) != 0)
  80     {
  81       /* There is a pending alarm set.  VAL indicates the interval it was
  82          set for, relative to the time recorded in _hurd_itimer_started.
  83          Now compensate for the time elapsed since to get the user's
  84          conception of the current value of the timer (as if the value
  85          stored decreased every microsecond).  */
  86       if (timercmp (&val.it_value, &elapsed, <))
  87         {
  88           /* Hmm.  The timer should have just gone off, but has not been
  89              reset.  This is a possible timing glitch.  The alarm will signal
  90              soon, so fabricate a value for how soon.  */
  91           val.it_value.tv_sec = 0;
  92           val.it_value.tv_usec = 10; /* Random.  */
  93         }
  94       else
  95         /* Subtract the time elapsed since the timer was set
  96            from the current timer value the user sees.  */
  97         subtract_timeval (&val.it_value, &elapsed);
  98     }
  99
 100   *value = val;
 101   return 0;
 102 }
 103
 104 weak_alias (__getitimer, getitimer)