text: /* Copyright (C) 1994 Free Software Foundation, Inc.
  This file is part of the GNU C Library.
  
  The GNU C Library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Library General Public License as
  published by the Free Software Foundation; either version 2 of the
  License, or (at your option) any later version.
  
  The GNU C Library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Library General Public License for more details.
  
  You should have received a copy of the GNU Library General Public
  License along with the GNU C Library; see the file COPYING.LIB.  If
  not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  Cambridge, MA 02139, USA.  */
  
  #include <ansidecl.h>
  #include <stddef.h>
  #include <errno.h>
  #include <sys/time.h>
  #include <hurd.h>
  
  /* XXX Temporary cheezoid implementation; see __setitmr.c.  */
  
  /* These are defined in __setitmr.c.  */
  extern spin_lock_t _hurd_itimer_lock;
  extern struct itimerval _hurd_itimerval;
  extern struct timeval _hurd_itimer_started;
  
  static inline void
  subtract_timeval (struct timeval *from, const struct timeval *subtract)
  {
    from->tv_usec -= subtract->tv_usec;
    from->tv_sec -= subtract->tv_sec;
    while (from->tv_usec < 0)
      {
        --from->tv_sec;
        from->tv_usec += 1000000;
      }
  }
  
  /* Set *VALUE to the current setting of timer WHICH.
     Return 0 on success, -1 on errors.  */
  int
  DEFUN(__getitimer, (which, value),
        enum __itimer_which which AND struct itimerval *value)
  {
    struct itimerval val;
    struct timeval elapsed;
  
    switch (which)
      {
      default:
        return __hurd_fail (EINVAL);
  
      case ITIMER_VIRTUAL:
      case ITIMER_PROF:
        return __hurd_fail (ENOSYS);
  
      case ITIMER_REAL:
        break;
      }
  
    /* Get the time now.  */
    if (__gettimeofday (&elapsed, NULL) < 0)
      return -1;
  
    /* Extract the current timer setting; and the time it was set, so we can
       calculate the time elapsed so far.  */
    HURD_CRITICAL_BEGIN;
    __spin_lock (&_hurd_itimer_lock);
    val = _hurd_itimerval;
    subtract_timeval (&elapsed, &_hurd_itimer_started);
    __spin_unlock (&_hurd_itimer_lock);
    HURD_CRITICAL_END;
  
    if ((val.it_value.tv_sec | val.it_value.tv_usec) != 0)
      {
        /* There is a pending alarm set.  VAL indicates the interval it was
  	 set for, relative to the time recorded in _hurd_itimer_started.
  	 Now compensate for the time elapsed since to get the user's
  	 conception of the current value of the timer (as if the value
  	 stored decreased every microsecond).  */
        if (timercmp (&val.it_value, &elapsed, <))
  	{
  	  /* Hmm.  The timer should have just gone off, but has not been
  	     reset.  This is a possible timing glitch.  The alarm will signal
  	     soon, so fabricate a value for how soon.  */
  	  val.it_value.tv_sec = 0;
  	  val.it_value.tv_usec = 10; /* Random.  */
  	}
        else
  	/* Subtract the time elapsed since the timer was set
  	   from the current timer value the user sees.  */
  	subtract_timeval (&val.it_value, &elapsed);
      }
  
    *value = val;
    return 0;
  }
  