root/fs/isofs/util.c

DEFINITIONS

1. iso_date

/*
 *  linux/fs/isofs/util.c
 */

#include "isofs.h"

/* 
 * 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;
}