44 lines
2.8 KiB
C
44 lines
2.8 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/conv/conv.h"
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#include "libc/macros.h"
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#include "libc/time/time.h"
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/**
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* Converts MS-DOS timestamp to UNIX.
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*
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* @note type signature supports dates greater than 2100
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* @see PKZIP, FAT
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*/
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int64_t DosDateTimeToUnix(unsigned date, unsigned time) {
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unsigned weekday, year, month, day, hour, minute, second, yday, leap;
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year = ((date & 0xfffffe00) >> 9) + 1980 - 1900;
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month = MAX(1, MIN(12, (date & 0x01e0) >> 5));
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day = (date & 0x001f) ? (date & 0x001f) - 1 : 0;
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hour = (time & 0x0000f800) >> 11;
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minute = (time & 0x000007e0) >> 5;
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second = (time & 0x0000001f) << 1;
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leap = year % 4 == 0 && (year % 100 || year % 400 == 0);
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yday = day + kMonthYearDay[leap][month - 1];
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return second + minute * 60 + hour * 3600 + yday * 86400 +
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(year - 70) * 31536000ull + ((year - 69) / 4) * 86400ull -
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((year - 1) / 100) * 86400ull + ((year + 299) / 400) * 86400ull;
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}
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