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 84