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1da177e4 LT |
1 | /* |
2 | * linux/fs/isofs/util.c | |
3 | */ | |
4 | ||
5 | #include <linux/time.h> | |
6 | #include <linux/fs.h> | |
7 | #include <linux/iso_fs.h> | |
8 | ||
9 | /* | |
10 | * We have to convert from a MM/DD/YY format to the Unix ctime format. | |
11 | * We have to take into account leap years and all of that good stuff. | |
12 | * Unfortunately, the kernel does not have the information on hand to | |
13 | * take into account daylight savings time, but it shouldn't matter. | |
14 | * The time stored should be localtime (with or without DST in effect), | |
15 | * and the timezone offset should hold the offset required to get back | |
16 | * to GMT. Thus we should always be correct. | |
17 | */ | |
18 | ||
19 | int iso_date(char * p, int flag) | |
20 | { | |
21 | int year, month, day, hour, minute, second, tz; | |
22 | int crtime, days, i; | |
23 | ||
24 | year = p[0] - 70; | |
25 | month = p[1]; | |
26 | day = p[2]; | |
27 | hour = p[3]; | |
28 | minute = p[4]; | |
29 | second = p[5]; | |
30 | if (flag == 0) tz = p[6]; /* High sierra has no time zone */ | |
31 | else tz = 0; | |
32 | ||
33 | if (year < 0) { | |
34 | crtime = 0; | |
35 | } else { | |
36 | int monlen[12] = {31,28,31,30,31,30,31,31,30,31,30,31}; | |
37 | ||
38 | days = year * 365; | |
39 | if (year > 2) | |
40 | days += (year+1) / 4; | |
41 | for (i = 1; i < month; i++) | |
42 | days += monlen[i-1]; | |
43 | if (((year+2) % 4) == 0 && month > 2) | |
44 | days++; | |
45 | days += day - 1; | |
46 | crtime = ((((days * 24) + hour) * 60 + minute) * 60) | |
47 | + second; | |
48 | ||
49 | /* sign extend */ | |
50 | if (tz & 0x80) | |
51 | tz |= (-1 << 8); | |
52 | ||
53 | /* | |
54 | * The timezone offset is unreliable on some disks, | |
55 | * so we make a sanity check. In no case is it ever | |
56 | * more than 13 hours from GMT, which is 52*15min. | |
57 | * The time is always stored in localtime with the | |
58 | * timezone offset being what get added to GMT to | |
59 | * get to localtime. Thus we need to subtract the offset | |
60 | * to get to true GMT, which is what we store the time | |
61 | * as internally. On the local system, the user may set | |
62 | * their timezone any way they wish, of course, so GMT | |
63 | * gets converted back to localtime on the receiving | |
64 | * system. | |
65 | * | |
66 | * NOTE: mkisofs in versions prior to mkisofs-1.10 had | |
67 | * the sign wrong on the timezone offset. This has now | |
68 | * been corrected there too, but if you are getting screwy | |
69 | * results this may be the explanation. If enough people | |
70 | * complain, a user configuration option could be added | |
71 | * to add the timezone offset in with the wrong sign | |
72 | * for 'compatibility' with older discs, but I cannot see how | |
73 | * it will matter that much. | |
74 | * | |
75 | * Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann) | |
76 | * for pointing out the sign error. | |
77 | */ | |
78 | if (-52 <= tz && tz <= 52) | |
79 | crtime -= tz * 15 * 60; | |
80 | } | |
81 | return crtime; | |
82 | } | |
83 |