| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * linux/fs/isofs/util.c |
| 3 | */ |
| 4 | |
| Al Viro | 94f2f71 | 2005-04-25 18:32:12 -0700 | [diff] [blame] | 5 | #include "isofs.h" |
| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6 | |
| 7 | /* |
| 8 | * We have to convert from a MM/DD/YY format to the Unix ctime format. |
| 9 | * We have to take into account leap years and all of that good stuff. |
| 10 | * Unfortunately, the kernel does not have the information on hand to |
| 11 | * take into account daylight savings time, but it shouldn't matter. |
| 12 | * The time stored should be localtime (with or without DST in effect), |
| 13 | * and the timezone offset should hold the offset required to get back |
| 14 | * to GMT. Thus we should always be correct. |
| 15 | */ |
| 16 | |
| 17 | int iso_date(char * p, int flag) |
| 18 | { |
| 19 | int year, month, day, hour, minute, second, tz; |
| 20 | int crtime, days, i; |
| 21 | |
| 22 | year = p[0] - 70; |
| 23 | month = p[1]; |
| 24 | day = p[2]; |
| 25 | hour = p[3]; |
| 26 | minute = p[4]; |
| 27 | second = p[5]; |
| 28 | if (flag == 0) tz = p[6]; /* High sierra has no time zone */ |
| 29 | else tz = 0; |
| 30 | |
| 31 | if (year < 0) { |
| 32 | crtime = 0; |
| 33 | } else { |
| 34 | int monlen[12] = {31,28,31,30,31,30,31,31,30,31,30,31}; |
| 35 | |
| 36 | days = year * 365; |
| 37 | if (year > 2) |
| 38 | days += (year+1) / 4; |
| 39 | for (i = 1; i < month; i++) |
| 40 | days += monlen[i-1]; |
| 41 | if (((year+2) % 4) == 0 && month > 2) |
| 42 | days++; |
| 43 | days += day - 1; |
| 44 | crtime = ((((days * 24) + hour) * 60 + minute) * 60) |
| 45 | + second; |
| 46 | |
| 47 | /* sign extend */ |
| 48 | if (tz & 0x80) |
| 49 | tz |= (-1 << 8); |
| 50 | |
| 51 | /* |
| 52 | * The timezone offset is unreliable on some disks, |
| 53 | * so we make a sanity check. In no case is it ever |
| 54 | * more than 13 hours from GMT, which is 52*15min. |
| 55 | * The time is always stored in localtime with the |
| 56 | * timezone offset being what get added to GMT to |
| 57 | * get to localtime. Thus we need to subtract the offset |
| 58 | * to get to true GMT, which is what we store the time |
| 59 | * as internally. On the local system, the user may set |
| 60 | * their timezone any way they wish, of course, so GMT |
| 61 | * gets converted back to localtime on the receiving |
| 62 | * system. |
| 63 | * |
| 64 | * NOTE: mkisofs in versions prior to mkisofs-1.10 had |
| 65 | * the sign wrong on the timezone offset. This has now |
| 66 | * been corrected there too, but if you are getting screwy |
| 67 | * results this may be the explanation. If enough people |
| 68 | * complain, a user configuration option could be added |
| 69 | * to add the timezone offset in with the wrong sign |
| 70 | * for 'compatibility' with older discs, but I cannot see how |
| 71 | * it will matter that much. |
| 72 | * |
| 73 | * Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann) |
| 74 | * for pointing out the sign error. |
| 75 | */ |
| 76 | if (-52 <= tz && tz <= 52) |
| 77 | crtime -= tz * 15 * 60; |
| 78 | } |
| 79 | return crtime; |
| 80 | } |