Line data    Source code

       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           0 : int iso_date(u8 *p, int flag)
      20             : {
      21           0 :         int year, month, day, hour, minute, second, tz;
      22           0 :         int crtime;
      23             : 
      24           0 :         year = p[0];
      25           0 :         month = p[1];
      26           0 :         day = p[2];
      27           0 :         hour = p[3];
      28           0 :         minute = p[4];
      29           0 :         second = p[5];
      30           0 :         if (flag == 0) tz = p[6]; /* High sierra has no time zone */
      31             :         else tz = 0;
      32             :         
      33           0 :         if (year < 0) {
      34             :                 crtime = 0;
      35             :         } else {
      36           0 :                 crtime = mktime64(year+1900, month, day, hour, minute, second);
      37             : 
      38             :                 /* sign extend */
      39           0 :                 if (tz & 0x80)
      40           0 :                         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           0 :                 if (-52 <= tz && tz <= 52)
      68           0 :                         crtime -= tz * 15 * 60;
      69             :         }
      70           0 :         return crtime;
      71             : }