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/* $OpenBSD: ntpleaps.h,v 1.4 2007/11/25 16:40:04 jmc Exp $ */
/*
* Copyright (c) 2002 Thorsten Glaser. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDERS 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.
*
*/
/* Leap second support for SNTP clients
* This header file and its corresponding C file provide generic
* ability for NTP or SNTP clients to correctly handle leap seconds
* by reading them from an always existing file and subtracting the
* leap seconds from the NTP return value before setting the posix
* clock. This is fairly portable between operating systems and may
* be used for patching other ntp clients, too. The tzfile used is:
* /usr/share/zoneinfo/right/UTC which is available on any unix-like
* platform with the Olson tz library, which is necessary to get real
* leap second zoneinfo files and userland support anyways.
*/
#ifndef _NTPLEAPS_H
#define _NTPLEAPS_H
/* Offset between struct timeval.tv_sec and a tai64_t */
#define NTPLEAPS_OFFSET (4611686018427387914ULL)
/* Hide this ugly value from programmes */
#define SEC_TO_TAI64(s) (NTPLEAPS_OFFSET + (u_int64_t)(s))
#define TAI64_TO_SEC(t) ((t) - NTPLEAPS_OFFSET)
/* Initializes the leap second table. Does not need to be called
* before usage of the subtract function, but calls ntpleaps_read.
* returns 0 on success, -1 on error (displays a warning on stderr)
*/
int ntpleaps_init(void);
/* Re-reads the leap second table, thus consuming quite much time.
* Ought to be called from within daemons at least once a month to
* ensure the in-memory table is always up-to-date.
* returns 0 on success, -1 on error (leap seconds will not be available)
*/
int ntpleaps_read(void);
/* Subtracts leap seconds from the given value (converts NTP time
* to posix clock tick time.
* returns 0 on success, -1 on error (time is unchanged), 1 on leap second
*/
int ntpleaps_sub(u_int64_t *);
#endif
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