72 lines
2.2 KiB
C
72 lines
2.2 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/fs/isofs/util.c
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*/
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#include <linux/time.h>
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#include "isofs.h"
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/*
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* We have to convert from a MM/DD/YY format to the Unix ctime format.
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* We have to take into account leap years and all of that good stuff.
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* Unfortunately, the kernel does not have the information on hand to
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* take into account daylight savings time, but it shouldn't matter.
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* The time stored should be localtime (with or without DST in effect),
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* and the timezone offset should hold the offset required to get back
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* to GMT. Thus we should always be correct.
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*/
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int iso_date(u8 *p, int flag)
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{
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int year, month, day, hour, minute, second, tz;
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int crtime;
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year = p[0];
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month = p[1];
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day = p[2];
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hour = p[3];
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minute = p[4];
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second = p[5];
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if (flag == 0) tz = p[6]; /* High sierra has no time zone */
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else tz = 0;
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if (year < 0) {
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crtime = 0;
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} else {
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crtime = mktime64(year+1900, month, day, hour, minute, second);
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/* sign extend */
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if (tz & 0x80)
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tz |= (-1 << 8);
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/*
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* The timezone offset is unreliable on some disks,
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* so we make a sanity check. In no case is it ever
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* more than 13 hours from GMT, which is 52*15min.
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* The time is always stored in localtime with the
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* timezone offset being what get added to GMT to
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* get to localtime. Thus we need to subtract the offset
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* to get to true GMT, which is what we store the time
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* as internally. On the local system, the user may set
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* their timezone any way they wish, of course, so GMT
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* gets converted back to localtime on the receiving
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* system.
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*
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* NOTE: mkisofs in versions prior to mkisofs-1.10 had
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* the sign wrong on the timezone offset. This has now
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* been corrected there too, but if you are getting screwy
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* results this may be the explanation. If enough people
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* complain, a user configuration option could be added
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* to add the timezone offset in with the wrong sign
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* for 'compatibility' with older discs, but I cannot see how
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* it will matter that much.
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*
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* Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann)
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* for pointing out the sign error.
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*/
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if (-52 <= tz && tz <= 52)
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crtime -= tz * 15 * 60;
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}
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return crtime;
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}
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