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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/isofs/util.c
3 */
4
Oscar Forner Martineze4a93be2015-01-06 16:54:19 -08005#include <linux/time.h>
Al Viro94f2f7152005-04-25 18:32:12 -07006#include "isofs.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -07007
8/*
9 * We have to convert from a MM/DD/YY format to the Unix ctime format.
10 * We have to take into account leap years and all of that good stuff.
11 * Unfortunately, the kernel does not have the information on hand to
12 * take into account daylight savings time, but it shouldn't matter.
13 * The time stored should be localtime (with or without DST in effect),
14 * and the timezone offset should hold the offset required to get back
15 * to GMT. Thus we should always be correct.
16 */
17
18int iso_date(char * p, int flag)
19{
20 int year, month, day, hour, minute, second, tz;
Oscar Forner Martineze4a93be2015-01-06 16:54:19 -080021 int crtime;
Linus Torvalds1da177e2005-04-16 15:20:36 -070022
Oscar Forner Martineze4a93be2015-01-06 16:54:19 -080023 year = p[0];
Linus Torvalds1da177e2005-04-16 15:20:36 -070024 month = p[1];
25 day = p[2];
26 hour = p[3];
27 minute = p[4];
28 second = p[5];
29 if (flag == 0) tz = p[6]; /* High sierra has no time zone */
30 else tz = 0;
31
32 if (year < 0) {
33 crtime = 0;
34 } else {
Oscar Forner Martineze4a93be2015-01-06 16:54:19 -080035 crtime = mktime64(year+1900, month, day, hour, minute, second);
Linus Torvalds1da177e2005-04-16 15:20:36 -070036
37 /* sign extend */
38 if (tz & 0x80)
39 tz |= (-1 << 8);
40
41 /*
42 * The timezone offset is unreliable on some disks,
43 * so we make a sanity check. In no case is it ever
44 * more than 13 hours from GMT, which is 52*15min.
45 * The time is always stored in localtime with the
46 * timezone offset being what get added to GMT to
47 * get to localtime. Thus we need to subtract the offset
48 * to get to true GMT, which is what we store the time
49 * as internally. On the local system, the user may set
50 * their timezone any way they wish, of course, so GMT
51 * gets converted back to localtime on the receiving
52 * system.
53 *
54 * NOTE: mkisofs in versions prior to mkisofs-1.10 had
55 * the sign wrong on the timezone offset. This has now
56 * been corrected there too, but if you are getting screwy
57 * results this may be the explanation. If enough people
58 * complain, a user configuration option could be added
59 * to add the timezone offset in with the wrong sign
60 * for 'compatibility' with older discs, but I cannot see how
61 * it will matter that much.
62 *
63 * Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann)
64 * for pointing out the sign error.
65 */
66 if (-52 <= tz && tz <= 52)
67 crtime -= tz * 15 * 60;
68 }
69 return crtime;
70}