FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_time.c

     /*      $NetBSD: subr_time.c,v 1.4 2008/07/15 16:18:08 christos Exp $   */
     
     /*
      * Copyright (c) 1982, 1986, 1989, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)kern_clock.c        8.5 (Berkeley) 1/21/94
     *      @(#)kern_time.c 8.4 (Berkeley) 5/26/95
     */
    
    #include <sys/cdefs.h>
    __KERNEL_RCSID(0, "$NetBSD: subr_time.c,v 1.4 2008/07/15 16:18:08 christos Exp $");
    
    #include <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/timex.h>
    #include <sys/time.h>
    #include <sys/timetc.h>
    #include <sys/intr.h>
    
    /*
     * Compute number of hz until specified time.  Used to compute second
     * argument to callout_reset() from an absolute time.
     */
    int
    tvhzto(const struct timeval *tvp)
    {
            struct timeval now, tv;
    
            tv = *tvp;      /* Don't modify original tvp. */
            getmicrotime(&now);
            timersub(&tv, &now, &tv);
            return tvtohz(&tv);
    }
    
    /*
     * Compute number of ticks in the specified amount of time.
     */
    int
    tvtohz(const struct timeval *tv)
    {
            unsigned long ticks;
            long sec, usec;
    
            /*
             * If the number of usecs in the whole seconds part of the time
             * difference fits in a long, then the total number of usecs will
             * fit in an unsigned long.  Compute the total and convert it to
             * ticks, rounding up and adding 1 to allow for the current tick
             * to expire.  Rounding also depends on unsigned long arithmetic
             * to avoid overflow.
             *
             * Otherwise, if the number of ticks in the whole seconds part of
             * the time difference fits in a long, then convert the parts to
             * ticks separately and add, using similar rounding methods and
             * overflow avoidance.  This method would work in the previous
             * case, but it is slightly slower and assumes that hz is integral.
             *
             * Otherwise, round the time difference down to the maximum
             * representable value.
             *
             * If ints are 32-bit, then the maximum value for any timeout in
             * 10ms ticks is 248 days.
             */
            sec = tv->tv_sec;
            usec = tv->tv_usec;
    
            if (usec < 0) {
                    sec--;
                    usec += 1000000;
            }
    
            if (sec < 0 || (sec == 0 && usec <= 0)) {
                    /*
                     * Would expire now or in the past.  Return 0 ticks.
                    * This is different from the legacy tvhzto() interface,
                    * and callers need to check for it.
                    */
                   ticks = 0;
           } else if (sec <= (LONG_MAX / 1000000))
                   ticks = (((sec * 1000000) + (unsigned long)usec + (tick - 1))
                       / tick) + 1;
           else if (sec <= (LONG_MAX / hz))
                   ticks = (sec * hz) +
                       (((unsigned long)usec + (tick - 1)) / tick) + 1;
           else
                   ticks = LONG_MAX;
   
           if (ticks > INT_MAX)
                   ticks = INT_MAX;
   
           return ((int)ticks);
   }
   
   int
   tshzto(const struct timespec *tsp)
   {
           struct timespec now, ts;
   
           ts = *tsp;      /* Don't modify original tsp. */
           getnanotime(&now);
           timespecsub(&ts, &now, &ts);
           return tstohz(&ts);
   }
   /*
    * Compute number of ticks in the specified amount of time.
    */
   int
   tstohz(const struct timespec *ts)
   {
           struct timeval tv;
   
           /*
            * usec has great enough resolution for hz, so convert to a
            * timeval and use tvtohz() above.
            */
           TIMESPEC_TO_TIMEVAL(&tv, ts);
           return tvtohz(&tv);
   }
   
   /*
    * Check that a proposed value to load into the .it_value or
    * .it_interval part of an interval timer is acceptable, and
    * fix it to have at least minimal value (i.e. if it is less
    * than the resolution of the clock, round it up.)
    */
   int
   itimerfix(struct timeval *tv)
   {
   
           if (tv->tv_sec < 0 || tv->tv_usec < 0 || tv->tv_usec >= 1000000)
                   return (EINVAL);
           if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
                   tv->tv_usec = tick;
           return (0);
   }
   
   int
   itimespecfix(struct timespec *ts)
   {
   
           if (ts->tv_sec < 0 || ts->tv_nsec < 0 || ts->tv_nsec >= 1000000000)
                   return (EINVAL);
           if (ts->tv_sec == 0 && ts->tv_nsec != 0 && ts->tv_nsec < tick * 1000)
                   ts->tv_nsec = tick * 1000;
           return (0);
   }

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