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-rw-r--r--fs/isofs/util.c83
1 files changed, 83 insertions, 0 deletions
diff --git a/fs/isofs/util.c b/fs/isofs/util.c
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+/*
+ * linux/fs/isofs/util.c
+ */
+
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/iso_fs.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;
+}
+
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