Linux Cross Reference
Linux/fs/isofs/util.c

   /*
    *  linux/fs/isofs/util.c
    *
    *  The special functions in the file are numbered according to the section
    *  of the iso 9660 standard in which they are described.  isonum_733 will
    *  convert numbers according to section 7.3.3, etc.
    *
    *  isofs special functions.  This file was lifted in its entirety from
    *  the 386BSD iso9660 filesystem, by Pace Willisson <pace@blitz.com>.
   */
  
  #include <linux/time.h>
  
  int
  isonum_711 (char * p)
  {
          return (*p & 0xff);
  }
  
  int
  isonum_712 (char * p)
  {
          int val;
          
          val = *p;
          if (val & 0x80)
                  val |= 0xffffff00;
          return (val);
  }
  
  int
  isonum_721 (char * p)
  {
          return ((p[0] & 0xff) | ((p[1] & 0xff) << 8));
  }
  
  int
  isonum_722 (char * p)
  {
          return (((p[0] & 0xff) << 8) | (p[1] & 0xff));
  }
  
  int
  isonum_723 (char * p)
  {
  #if 0
          if (p[0] != p[3] || p[1] != p[2]) {
                  fprintf (stderr, "invalid format 7.2.3 number\n");
                  exit (1);
          }
  #endif
          return (isonum_721 (p));
  }
  
  int
  isonum_731 (char * p)
  {
          return ((p[0] & 0xff)
                  | ((p[1] & 0xff) << 8)
                  | ((p[2] & 0xff) << 16)
                  | ((p[3] & 0xff) << 24));
  }
  
  int
  isonum_732 (char * p)
  {
          return (((p[0] & 0xff) << 24)
                  | ((p[1] & 0xff) << 16)
                  | ((p[2] & 0xff) << 8)
                  | (p[3] & 0xff));
  }
  
  int
  isonum_733 (char * p)
  {
  #if 0
          int i;
  
          for (i = 0; i < 4; i++) {
                  if (p[i] != p[7-i]) {
                          fprintf (stderr, "bad format 7.3.3 number\n");
                          exit (1);
                  }
          }
  #endif
          return (isonum_731 (p));
  }
  
  /* 
   * We have to convert from a MM/DD/YY format to the Unix ctime format.
   * We have to take into account leap years and all of that good stuff.
   * Unfortunately, the kernel does not have the information on hand to
   * take into account daylight savings time, but it shouldn't matter.
   * The time stored should be localtime (with or without DST in effect),
   * and the timezone offset should hold the offset required to get back
   * to GMT.  Thus  we should always be correct.
   */
  
  int iso_date(char * p, int flag)
 {
         int year, month, day, hour, minute, second, tz;
         int crtime, days, i;
 
         year = p[0] - 70;
         month = p[1];
         day = p[2];
         hour = p[3];
         minute = p[4];
         second = p[5];
         if (flag == 0) tz = p[6]; /* High sierra has no time zone */
         else tz = 0;
         
         if (year < 0) {
                 crtime = 0;
         } else {
                 int monlen[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
 
                 days = year * 365;
                 if (year > 2)
                         days += (year+1) / 4;
                 for (i = 1; i < month; i++)
                         days += monlen[i-1];
                 if (((year+2) % 4) == 0 && month > 2)
                         days++;
                 days += day - 1;
                 crtime = ((((days * 24) + hour) * 60 + minute) * 60)
                         + second;
 
                 /* sign extend */
                 if (tz & 0x80)
                         tz |= (-1 << 8);
                 
                 /* 
                  * The timezone offset is unreliable on some disks,
                  * so we make a sanity check.  In no case is it ever
                  * more than 13 hours from GMT, which is 52*15min.
                  * The time is always stored in localtime with the
                  * timezone offset being what get added to GMT to
                  * get to localtime.  Thus we need to subtract the offset
                  * to get to true GMT, which is what we store the time
                  * as internally.  On the local system, the user may set
                  * their timezone any way they wish, of course, so GMT
                  * gets converted back to localtime on the receiving
                  * system.
                  *
                  * NOTE: mkisofs in versions prior to mkisofs-1.10 had
                  * the sign wrong on the timezone offset.  This has now
                  * been corrected there too, but if you are getting screwy
                  * results this may be the explanation.  If enough people
                  * complain, a user configuration option could be added
                  * to add the timezone offset in with the wrong sign
                  * for 'compatibility' with older discs, but I cannot see how
                  * it will matter that much.
                  *
                  * Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann)
                  * for pointing out the sign error.
                  */
                 if (-52 <= tz && tz <= 52)
                         crtime -= tz * 15 * 60;
         }
         return crtime;
 }