util.c (2237B)
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 19int iso_date(u8 *p, int flag) 20{ 21 int year, month, day, hour, minute, second, tz; 22 int crtime; 23 24 year = p[0]; 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 crtime = mktime64(year+1900, month, day, hour, minute, second); 37 38 /* sign extend */ 39 if (tz & 0x80) 40 tz |= (-1 << 8); 41 42 /* 43 * The timezone offset is unreliable on some disks, 44 * so we make a sanity check. In no case is it ever 45 * more than 13 hours from GMT, which is 52*15min. 46 * The time is always stored in localtime with the 47 * timezone offset being what get added to GMT to 48 * get to localtime. Thus we need to subtract the offset 49 * to get to true GMT, which is what we store the time 50 * as internally. On the local system, the user may set 51 * their timezone any way they wish, of course, so GMT 52 * gets converted back to localtime on the receiving 53 * system. 54 * 55 * NOTE: mkisofs in versions prior to mkisofs-1.10 had 56 * the sign wrong on the timezone offset. This has now 57 * been corrected there too, but if you are getting screwy 58 * results this may be the explanation. If enough people 59 * complain, a user configuration option could be added 60 * to add the timezone offset in with the wrong sign 61 * for 'compatibility' with older discs, but I cannot see how 62 * it will matter that much. 63 * 64 * Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann) 65 * for pointing out the sign error. 66 */ 67 if (-52 <= tz && tz <= 52) 68 crtime -= tz * 15 * 60; 69 } 70 return crtime; 71}