diff options
Diffstat (limited to 'fs/isofs/util.c')
| -rw-r--r-- | fs/isofs/util.c | 44 |
1 files changed, 37 insertions, 7 deletions
diff --git a/fs/isofs/util.c b/fs/isofs/util.c index b080406cd..75183cc8f 100644 --- a/fs/isofs/util.c +++ b/fs/isofs/util.c @@ -84,10 +84,16 @@ isonum_733 (char * p) 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, - so there will be cases (roughly half the time) where the dates are off by one hour. */ +/* + * 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; @@ -121,9 +127,33 @@ int iso_date(char * p, int flag) if (tz & 0x80) tz |= (-1 << 8); - /* timezone offset is unreliable on some disks */ - if (-48 <= tz && tz <= 52) - crtime += tz * 15 * 60; + /* + * 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 explaination. 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; } |