usr/src/lib/libc/port/sys/time_util.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #pragma ident   "%Z%%M% %I%     %E% SMI"
  28
  29 #include <sys/types.h>
  30 #include <time.h>
  31 #include <errno.h>
  32
  33 /*
  34  * This function is blatently stolen from the kernel.
  35  * See the dissertation in the comments preceding the
  36  * hrt2ts() function in:
  37  *      kernel/os/timers.c
  38  */
  39 void
  40 hrt2ts(hrtime_t hrt, timespec_t *tsp)
  41 {
  42         uint32_t sec, nsec, tmp;
  43
  44         tmp = (uint32_t)(hrt >> 30);
  45         sec = tmp - (tmp >> 2);
  46         sec = tmp - (sec >> 5);
  47         sec = tmp + (sec >> 1);
  48         sec = tmp - (sec >> 6) + 7;
  49         sec = tmp - (sec >> 3);
  50         sec = tmp + (sec >> 1);
  51         sec = tmp + (sec >> 3);
  52         sec = tmp + (sec >> 4);
  53         tmp = (sec << 7) - sec - sec - sec;
  54         tmp = (tmp << 7) - tmp - tmp - tmp;
  55         tmp = (tmp << 7) - tmp - tmp - tmp;
  56         nsec = (uint32_t)hrt - (tmp << 9);
  57         while (nsec >= NANOSEC) {
  58                 nsec -= NANOSEC;
  59                 sec++;
  60         }
  61         tsp->tv_sec = (time_t)sec;
  62         tsp->tv_nsec = nsec;
  63 }
  64
  65 /*
  66  * Convert absolute time to relative time.
  67  * All *timedwait() system call traps expect relative time.
  68  */
  69 void
  70 abstime_to_reltime(clockid_t clock_id,
  71         const timespec_t *abstime, timespec_t *reltime)
  72 {
  73         extern int __clock_gettime(clockid_t, timespec_t *);
  74         timespec_t now;
  75
  76         if (clock_id == CLOCK_HIGHRES)
  77                 hrt2ts(gethrtime(), &now);
  78         else
  79                 (void) __clock_gettime(clock_id, &now);
  80         if (abstime->tv_nsec >= now.tv_nsec) {
  81                 reltime->tv_sec = abstime->tv_sec - now.tv_sec;
  82                 reltime->tv_nsec = abstime->tv_nsec - now.tv_nsec;
  83         } else {
  84                 reltime->tv_sec = abstime->tv_sec - now.tv_sec - 1;
  85                 reltime->tv_nsec = abstime->tv_nsec - now.tv_nsec + NANOSEC;
  86         }
  87         /*
  88          * If the absolute time has already passed,
  89          * just set the relative time to zero.
  90          */
  91         if (reltime->tv_sec < 0) {
  92                 reltime->tv_sec = 0;
  93                 reltime->tv_nsec = 0;
  94         }
  95         /*
  96          * If the specified absolute time has a bad nanoseconds value,
  97          * assign it to the relative time value.  If the interface
  98          * attempts to sleep, the bad value will be detected then.
  99          * The SUSV3 Posix spec is very clear that such detection
 100          * should not happen until an attempt to sleep is made.
 101          */
 102         if ((ulong_t)abstime->tv_nsec >= NANOSEC)
 103                 reltime->tv_nsec = abstime->tv_nsec;
 104 }