1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/fs/isofs/util.c 4 */ 5 6 #include <linux/time.h> 7 #include "isofs.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 struct timespec64 iso_date(u8 *p, int flags) 20 { 21 int year, month, day, hour, minute, second, tz; 22 struct timespec64 ts; 23 24 if (flags & ISO_DATE_LONG_FORM) { 25 year = (p[0] - '0') * 1000 + 26 (p[1] - '0') * 100 + 27 (p[2] - '0') * 10 + 28 (p[3] - '0') - 1900; 29 month = ((p[4] - '0') * 10 + (p[5] - '0')); 30 day = ((p[6] - '0') * 10 + (p[7] - '0')); 31 hour = ((p[8] - '0') * 10 + (p[9] - '0')); 32 minute = ((p[10] - '0') * 10 + (p[11] - '0')); 33 second = ((p[12] - '0') * 10 + (p[13] - '0')); 34 ts.tv_nsec = ((p[14] - '0') * 10 + (p[15] - '0')) * 10000000; 35 tz = p[16]; 36 } else { 37 year = p[0]; 38 month = p[1]; 39 day = p[2]; 40 hour = p[3]; 41 minute = p[4]; 42 second = p[5]; 43 ts.tv_nsec = 0; 44 /* High sierra has no time zone */ 45 tz = flags & ISO_DATE_HIGH_SIERRA ? 0 : p[6]; 46 } 47 48 if (year < 0) { 49 ts.tv_sec = 0; 50 } else { 51 ts.tv_sec = mktime64(year+1900, month, day, hour, minute, second); 52 53 /* sign extend */ 54 if (tz & 0x80) 55 tz |= (-1 << 8); 56 57 /* 58 * The timezone offset is unreliable on some disks, 59 * so we make a sanity check. In no case is it ever 60 * more than 13 hours from GMT, which is 52*15min. 61 * The time is always stored in localtime with the 62 * timezone offset being what get added to GMT to 63 * get to localtime. Thus we need to subtract the offset 64 * to get to true GMT, which is what we store the time 65 * as internally. On the local system, the user may set 66 * their timezone any way they wish, of course, so GMT 67 * gets converted back to localtime on the receiving 68 * system. 69 * 70 * NOTE: mkisofs in versions prior to mkisofs-1.10 had 71 * the sign wrong on the timezone offset. This has now 72 * been corrected there too, but if you are getting screwy 73 * results this may be the explanation. If enough people 74 * complain, a user configuration option could be added 75 * to add the timezone offset in with the wrong sign 76 * for 'compatibility' with older discs, but I cannot see how 77 * it will matter that much. 78 * 79 * Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann) 80 * for pointing out the sign error. 81 */ 82 if (-52 <= tz && tz <= 52) 83 ts.tv_sec -= tz * 15 * 60; 84 } 85 return ts; 86 } 87