port/sys/time_util.c

	time_util.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/types.h>
#include <time.h>
#include <errno.h>

/*
 * This function is blatently stolen from the kernel.
 * See the dissertation in the comments preceding the
 * hrt2ts() function in:
 *  uts/common/os/timers.c
 */
void
hrt2ts(hrtime_t hrt, timespec_t *tsp)
{
    uint32_t sec, nsec, tmp;

    tmp = (uint32_t)(hrt >> 30);
    sec = tmp - (tmp >> 2);
    sec = tmp - (sec >> 5);
    sec = tmp + (sec >> 1);
    sec = tmp - (sec >> 6) + 7;
    sec = tmp - (sec >> 3);
    sec = tmp + (sec >> 1);
    sec = tmp + (sec >> 3);
    sec = tmp + (sec >> 4);
    tmp = (sec << 7) - sec - sec - sec;
    tmp = (tmp << 7) - tmp - tmp - tmp;
    tmp = (tmp << 7) - tmp - tmp - tmp;
    nsec = (uint32_t)hrt - (tmp << 9);
    while (nsec >= NANOSEC) {
        nsec -= NANOSEC;
        sec++;
    }
    tsp->tv_sec = (time_t)sec;
    tsp->tv_nsec = nsec;
}

/*
 * Convert absolute time to relative time.
 * All *timedwait() system call traps expect relative time.
 */
void
abstime_to_reltime(clockid_t clock_id,
    const timespec_t *abstime, timespec_t *reltime)
{
    extern int __clock_gettime(clockid_t, timespec_t *);
    timespec_t now;

    if (clock_id == CLOCK_HIGHRES)
        hrt2ts(gethrtime(), &now);
    else
        (void) __clock_gettime(clock_id, &now);
    if (abstime->tv_nsec >= now.tv_nsec) {
        reltime->tv_sec = abstime->tv_sec - now.tv_sec;
        reltime->tv_nsec = abstime->tv_nsec - now.tv_nsec;
    } else {
        reltime->tv_sec = abstime->tv_sec - now.tv_sec - 1;
        reltime->tv_nsec = abstime->tv_nsec - now.tv_nsec + NANOSEC;
    }
    /*
     * If the absolute time has already passed,
     * just set the relative time to zero.
     */
    if (reltime->tv_sec < 0) {
        reltime->tv_sec = 0;
        reltime->tv_nsec = 0;
    }
    /*
     * If the specified absolute time has a bad nanoseconds value,
     * assign it to the relative time value.  If the interface
     * attempts to sleep, the bad value will be detected then.
     * The SUSV3 Posix spec is very clear that such detection
     * should not happen until an attempt to sleep is made.
     */
    if ((ulong_t)abstime->tv_nsec >= NANOSEC)
        reltime->tv_nsec = abstime->tv_nsec;
}