forked from osmocom/wireshark
68 lines
2.0 KiB
C
68 lines
2.0 KiB
C
/** @file
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*
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* Definitions of epoch values for various absolute time types.
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*
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* Wireshark - Network traffic analyzer
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* By Gerald Combs <gerald@wireshark.org>
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* Copyright 2006 Gerald Combs
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*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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#ifndef __EPOCHS_H__
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#define __EPOCHS_H__
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#include <glib.h>
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/*
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* Deltas between the epochs for various non-UN*X time stamp formats and
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* the January 1, 1970, 00:00:00 (proleptic?) UTC epoch for the UN*X time
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* stamp format.
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*/
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/*
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* 1900-01-01 00:00:00 (proleptic?) UTC.
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* Used by a number of time formats.
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*/
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#define EPOCH_DELTA_1900_01_01_00_00_00_UTC 2208988800U
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/*
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* 1904-01-01 00:00:00 (proleptic?) UTC.
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* Used in the classic Mac OS, and by formats, such as MPEG-4 Part 14 (MP4),
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* which is based on Apple's QuickTime format.
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*/
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#define EPOCH_DELTA_1904_01_01_00_00_00_UTC 2082844800U
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/*
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* 1601-01-01 (proleptic Gregorian) 00:00:00 (proleptic?) UTC.
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* The Windows NT epoch, used in a number of places, as it is
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* the start of a 400 year Gregorian cycle.
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*
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* This is
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*
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* 369*365.25*24*60*60-(3*24*60*60+6*60*60)
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*
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* or equivalently,
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*
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* (89*4*365.25+(3*4+1)*365)*24*60*60
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*
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* 1970-1601 is 369; 365.25 is the average length of a year in days,
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* including leap years.
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*
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* 369 = 4*92 + 1, so there are 92 groups of 4 consecutive years plus
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* one leftover year, 1969, with 365 days.
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*
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* All but three of the groups of 4 consecutive years average 365.25 days
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* per year, as they have one leap year in the group. However, 1700, 1800,
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* and 1900 were not leap years, as, while they're all evenly divisible by 4,
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* they're also evenly divisible by 100, but not evenly divisible by 400.
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*
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* So we have 89 groups of 4 consecutive years that average 365.25
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* days per year, 3 groups of 4 consecutive years that average 365 days
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* (as they lack a leap year), and one leftover year, 1969, that is
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* 365 days long.
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*/
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#define EPOCH_DELTA_1601_01_01_00_00_00_UTC G_GUINT64_CONSTANT(11644473600)
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#endif /* __EPOCHS_H__ */
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