311 lines
10 KiB
C
311 lines
10 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 2006 Poul-Henning Kamp
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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* Convert MS-DOS FAT format timestamps to and from unix timespecs
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*
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* FAT filestamps originally consisted of two 16 bit integers, encoded like
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* this:
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*
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* yyyyyyymmmmddddd (year - 1980, month, day)
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*
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* hhhhhmmmmmmsssss (hour, minutes, seconds divided by two)
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*
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* Subsequently even Microsoft realized that files could be accessed in less
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* than two seconds and a byte was added containing:
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*
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* sfffffff (second mod two, 100ths of second)
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*
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* FAT timestamps are in the local timezone, with no indication of which
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* timezone much less if daylight savings time applies.
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*
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* Later on again, in Windows NT, timestamps were defined relative to GMT.
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*
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* Purists will point out that UTC replaced GMT for such uses around
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* half a century ago, already then. Ironically "NT" was an abbreviation of
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* "New Technology". Anyway...
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*
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* The 'utc' argument determines if the resulting FATTIME timestamp
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* should be on the UTC or local timezone calendar.
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*
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* The conversion functions below cut time into four-year leap-year
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* cycles rather than single years and uses table lookups inside those
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* cycles to get the months and years sorted out.
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*
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* Obviously we cannot calculate the correct table index going from
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* a posix seconds count to Y/M/D, but we can get pretty close by
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* dividing the daycount by 32 (giving a too low index), and then
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* adjusting upwards a couple of steps if necessary.
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*
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* FAT timestamps have 7 bits for the year and starts at 1980, so
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* they can represent up to 2107 which means that the non-leap-year
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* 2100 must be handled.
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*
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* XXX: As long as time_t is 32 bits this is not relevant or easily
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* XXX: testable. Revisit when time_t grows bigger.
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* XXX: grepfodder: 64 bit time_t, y2100, y2.1k, 2100, leap year
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*
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*/
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#include <sys/clock.h>
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#define DAY (24 * 60 * 60) /* Length of day in seconds */
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#define YEAR 365 /* Length of normal year */
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#define LYC (4 * YEAR + 1) /* Length of 4 year leap-year cycle */
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#define T1980 (10 * 365 + 2) /* Days from 1970 to 1980 */
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/* End of month is N days from start of (normal) year */
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#define JAN 31
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#define FEB (JAN + 28)
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#define MAR (FEB + 31)
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#define APR (MAR + 30)
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#define MAY (APR + 31)
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#define JUN (MAY + 30)
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#define JUL (JUN + 31)
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#define AUG (JUL + 31)
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#define SEP (AUG + 30)
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#define OCT (SEP + 31)
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#define NOV (OCT + 30)
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#define DEC (NOV + 31)
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/* Table of months in a 4 year leap-year cycle */
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#define ENC(y,m) (((y) << 9) | ((m) << 5))
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static const struct {
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uint16_t days; /* month start in days relative to cycle */
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uint16_t coded; /* encoded year + month information */
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} mtab[48] = {
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{ 0 + 0 * YEAR, ENC(0, 1) },
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{ JAN + 0 * YEAR, ENC(0, 2) }, { FEB + 0 * YEAR + 1, ENC(0, 3) },
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{ MAR + 0 * YEAR + 1, ENC(0, 4) }, { APR + 0 * YEAR + 1, ENC(0, 5) },
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{ MAY + 0 * YEAR + 1, ENC(0, 6) }, { JUN + 0 * YEAR + 1, ENC(0, 7) },
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{ JUL + 0 * YEAR + 1, ENC(0, 8) }, { AUG + 0 * YEAR + 1, ENC(0, 9) },
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{ SEP + 0 * YEAR + 1, ENC(0, 10) }, { OCT + 0 * YEAR + 1, ENC(0, 11) },
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{ NOV + 0 * YEAR + 1, ENC(0, 12) }, { DEC + 0 * YEAR + 1, ENC(1, 1) },
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{ JAN + 1 * YEAR + 1, ENC(1, 2) }, { FEB + 1 * YEAR + 1, ENC(1, 3) },
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{ MAR + 1 * YEAR + 1, ENC(1, 4) }, { APR + 1 * YEAR + 1, ENC(1, 5) },
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{ MAY + 1 * YEAR + 1, ENC(1, 6) }, { JUN + 1 * YEAR + 1, ENC(1, 7) },
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{ JUL + 1 * YEAR + 1, ENC(1, 8) }, { AUG + 1 * YEAR + 1, ENC(1, 9) },
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{ SEP + 1 * YEAR + 1, ENC(1, 10) }, { OCT + 1 * YEAR + 1, ENC(1, 11) },
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{ NOV + 1 * YEAR + 1, ENC(1, 12) }, { DEC + 1 * YEAR + 1, ENC(2, 1) },
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{ JAN + 2 * YEAR + 1, ENC(2, 2) }, { FEB + 2 * YEAR + 1, ENC(2, 3) },
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{ MAR + 2 * YEAR + 1, ENC(2, 4) }, { APR + 2 * YEAR + 1, ENC(2, 5) },
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{ MAY + 2 * YEAR + 1, ENC(2, 6) }, { JUN + 2 * YEAR + 1, ENC(2, 7) },
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{ JUL + 2 * YEAR + 1, ENC(2, 8) }, { AUG + 2 * YEAR + 1, ENC(2, 9) },
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{ SEP + 2 * YEAR + 1, ENC(2, 10) }, { OCT + 2 * YEAR + 1, ENC(2, 11) },
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{ NOV + 2 * YEAR + 1, ENC(2, 12) }, { DEC + 2 * YEAR + 1, ENC(3, 1) },
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{ JAN + 3 * YEAR + 1, ENC(3, 2) }, { FEB + 3 * YEAR + 1, ENC(3, 3) },
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{ MAR + 3 * YEAR + 1, ENC(3, 4) }, { APR + 3 * YEAR + 1, ENC(3, 5) },
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{ MAY + 3 * YEAR + 1, ENC(3, 6) }, { JUN + 3 * YEAR + 1, ENC(3, 7) },
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{ JUL + 3 * YEAR + 1, ENC(3, 8) }, { AUG + 3 * YEAR + 1, ENC(3, 9) },
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{ SEP + 3 * YEAR + 1, ENC(3, 10) }, { OCT + 3 * YEAR + 1, ENC(3, 11) },
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{ NOV + 3 * YEAR + 1, ENC(3, 12) }
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};
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void
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timespec2fattime(const struct timespec *tsp, int utc, uint16_t *ddp,
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uint16_t *dtp, uint8_t *dhp)
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{
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time_t t1;
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unsigned t2, l, m;
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t1 = tsp->tv_sec;
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if (!utc)
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t1 -= utc_offset();
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if (dhp != NULL)
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*dhp = (tsp->tv_sec & 1) * 100 + tsp->tv_nsec / 10000000;
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if (dtp != NULL) {
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*dtp = (t1 / 2) % 30;
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*dtp |= ((t1 / 60) % 60) << 5;
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*dtp |= ((t1 / 3600) % 24) << 11;
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}
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if (ddp != NULL) {
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t2 = t1 / DAY;
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if (t2 < T1980) {
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/* Impossible date, truncate to 1980-01-01 */
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*ddp = 0x0021;
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} else {
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t2 -= T1980;
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/*
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* 2100 is not a leap year.
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* XXX: a 32 bit time_t can not get us here.
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*/
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if (t2 >= ((2100 - 1980) / 4 * LYC + FEB))
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t2++;
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/* Account for full leapyear cycles */
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l = t2 / LYC;
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*ddp = (l * 4) << 9;
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t2 -= l * LYC;
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/* Find approximate table entry */
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m = t2 / 32;
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/* Find correct table entry */
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while (m < 47 && mtab[m + 1].days <= t2)
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m++;
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/* Get year + month from the table */
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*ddp += mtab[m].coded;
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/* And apply the day in the month */
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t2 -= mtab[m].days - 1;
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*ddp |= t2;
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}
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}
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}
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/*
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* Table indexed by the bottom two bits of year + four bits of the month
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* from the FAT timestamp, returning number of days into 4 year long
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* leap-year cycle
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*/
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#define DCOD(m, y, l) ((m) + YEAR * (y) + (l))
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static const uint16_t daytab[64] = {
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0, DCOD( 0, 0, 0), DCOD(JAN, 0, 0), DCOD(FEB, 0, 1),
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DCOD(MAR, 0, 1), DCOD(APR, 0, 1), DCOD(MAY, 0, 1), DCOD(JUN, 0, 1),
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DCOD(JUL, 0, 1), DCOD(AUG, 0, 1), DCOD(SEP, 0, 1), DCOD(OCT, 0, 1),
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DCOD(NOV, 0, 1), DCOD(DEC, 0, 1), 0, 0,
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0, DCOD( 0, 1, 1), DCOD(JAN, 1, 1), DCOD(FEB, 1, 1),
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DCOD(MAR, 1, 1), DCOD(APR, 1, 1), DCOD(MAY, 1, 1), DCOD(JUN, 1, 1),
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DCOD(JUL, 1, 1), DCOD(AUG, 1, 1), DCOD(SEP, 1, 1), DCOD(OCT, 1, 1),
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DCOD(NOV, 1, 1), DCOD(DEC, 1, 1), 0, 0,
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0, DCOD( 0, 2, 1), DCOD(JAN, 2, 1), DCOD(FEB, 2, 1),
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DCOD(MAR, 2, 1), DCOD(APR, 2, 1), DCOD(MAY, 2, 1), DCOD(JUN, 2, 1),
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DCOD(JUL, 2, 1), DCOD(AUG, 2, 1), DCOD(SEP, 2, 1), DCOD(OCT, 2, 1),
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DCOD(NOV, 2, 1), DCOD(DEC, 2, 1), 0, 0,
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0, DCOD( 0, 3, 1), DCOD(JAN, 3, 1), DCOD(FEB, 3, 1),
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DCOD(MAR, 3, 1), DCOD(APR, 3, 1), DCOD(MAY, 3, 1), DCOD(JUN, 3, 1),
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DCOD(JUL, 3, 1), DCOD(AUG, 3, 1), DCOD(SEP, 3, 1), DCOD(OCT, 3, 1),
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DCOD(NOV, 3, 1), DCOD(DEC, 3, 1), 0, 0
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};
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void
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fattime2timespec(unsigned dd, unsigned dt, unsigned dh, int utc,
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struct timespec *tsp)
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{
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unsigned day;
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/* Unpack time fields */
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tsp->tv_sec = (dt & 0x1f) << 1;
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tsp->tv_sec += ((dt & 0x7e0) >> 5) * 60;
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tsp->tv_sec += ((dt & 0xf800) >> 11) * 3600;
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tsp->tv_sec += dh / 100;
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tsp->tv_nsec = (dh % 100) * 10000000;
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/* Day of month */
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day = (dd & 0x1f) - 1;
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/* Full leap-year cycles */
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day += LYC * ((dd >> 11) & 0x1f);
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/* Month offset from leap-year cycle */
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day += daytab[(dd >> 5) & 0x3f];
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/*
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* 2100 is not a leap year.
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* XXX: a 32 bit time_t can not get us here.
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*/
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if (day >= ((2100 - 1980) / 4 * LYC + FEB))
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day--;
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/* Align with time_t epoch */
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day += T1980;
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tsp->tv_sec += DAY * day;
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if (!utc)
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tsp->tv_sec += utc_offset();
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}
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#ifdef TEST_DRIVER
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#include <stdio.h>
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#include <unistd.h>
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#include <stdlib.h>
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int
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main(int argc __unused, char **argv __unused)
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{
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int i;
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struct timespec ts;
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struct tm tm;
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double a;
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uint16_t d, t;
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uint8_t p;
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char buf[100];
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for (i = 0; i < 10000; i++) {
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do {
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ts.tv_sec = random();
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} while (ts.tv_sec < T1980 * 86400);
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ts.tv_nsec = random() % 1000000000;
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printf("%10d.%03ld -- ", ts.tv_sec, ts.tv_nsec / 1000000);
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gmtime_r(&ts.tv_sec, &tm);
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strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm);
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printf("%s -- ", buf);
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a = ts.tv_sec + ts.tv_nsec * 1e-9;
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d = t = p = 0;
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timet2fattime(&ts, &d, &t, &p);
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printf("%04x %04x %02x -- ", d, t, p);
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printf("%3d %02d %02d %02d %02d %02d -- ",
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((d >> 9) & 0x7f) + 1980,
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(d >> 5) & 0x0f,
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(d >> 0) & 0x1f,
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(t >> 11) & 0x1f,
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(t >> 5) & 0x3f,
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((t >> 0) & 0x1f) * 2);
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ts.tv_sec = ts.tv_nsec = 0;
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fattime2timet(d, t, p, &ts);
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printf("%10d.%03ld == ", ts.tv_sec, ts.tv_nsec / 1000000);
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gmtime_r(&ts.tv_sec, &tm);
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strftime(buf, sizeof buf, "%Y %m %d %H %M %S", &tm);
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printf("%s -- ", buf);
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a -= ts.tv_sec + ts.tv_nsec * 1e-9;
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printf("%.3f", a);
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printf("\n");
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}
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return (0);
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}
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#endif /* TEST_DRIVER */
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