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/* $OpenBSD: ntpleaps.h,v 1.2 2002/07/31 12:48:46 jakob Exp $ */
/*
* Copyright (c) 2002 by Thorsten "mirabile" Glaser <x86@ePOST.de>
*
* Permission is hereby granted to any person obtaining a copy of this work
* to deal in the work, without restrictions, including unlimited rights to
* use, copy, modify, merge, publish, distribute, sublicense or sell copies
* of the work, and to permit persons to whom the work is furnished to also
* do so, as long as due credit is given to the original author and contri-
* butors, and the following disclaimer is kept in all substantial portions
* of the work or accompanying documentation:
*
* This work is provided "AS IS", without warranty of any kind, neither ex-
* press nor implied, including, but not limited to, the warranties of mer-
* chantability, fitness for particular purposes and noninfringement. In NO
* event shall the author and contributors be liable for any claim, damages
* and such, whether in contract, strict liability or otherwise, arising in
* any way out of this work, even if advised of the possibility of such.
*/
/* 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 funtion, 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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