fs/isofs/util.c

   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