1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 *  linux/fs/isofs/util.c
 4 */
 5
 6#include <linux/time.h>
 7#include "isofs.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
19int iso_date(u8 *p, int flag)
20{
21	int year, month, day, hour, minute, second, tz;
22	int crtime;
23
24	year = p[0];
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		crtime = mktime64(year+1900, month, day, hour, minute, second);
 
 
 
 
 
 
 
 
 
 
 
37
38		/* sign extend */
39		if (tz & 0x80)
40			tz |= (-1 << 8);
41		
42		/* 
43		 * The timezone offset is unreliable on some disks,
44		 * so we make a sanity check.  In no case is it ever
45		 * more than 13 hours from GMT, which is 52*15min.
46		 * The time is always stored in localtime with the
47		 * timezone offset being what get added to GMT to
48		 * get to localtime.  Thus we need to subtract the offset
49		 * to get to true GMT, which is what we store the time
50		 * as internally.  On the local system, the user may set
51		 * their timezone any way they wish, of course, so GMT
52		 * gets converted back to localtime on the receiving
53		 * system.
54		 *
55		 * NOTE: mkisofs in versions prior to mkisofs-1.10 had
56		 * the sign wrong on the timezone offset.  This has now
57		 * been corrected there too, but if you are getting screwy
58		 * results this may be the explanation.  If enough people
59		 * complain, a user configuration option could be added
60		 * to add the timezone offset in with the wrong sign
61		 * for 'compatibility' with older discs, but I cannot see how
62		 * it will matter that much.
63		 *
64		 * Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann)
65		 * for pointing out the sign error.
66		 */
67		if (-52 <= tz && tz <= 52)
68			crtime -= tz * 15 * 60;
69	}
70	return crtime;
71}		

 
 1/*
 2 *  linux/fs/isofs/util.c
 3 */
 4
 
 5#include "isofs.h"
 6
 7/* 
 8 * We have to convert from a MM/DD/YY format to the Unix ctime format.
 9 * We have to take into account leap years and all of that good stuff.
10 * Unfortunately, the kernel does not have the information on hand to
11 * take into account daylight savings time, but it shouldn't matter.
12 * The time stored should be localtime (with or without DST in effect),
13 * and the timezone offset should hold the offset required to get back
14 * to GMT.  Thus  we should always be correct.
15 */
16
17int iso_date(char * p, int flag)
18{
19	int year, month, day, hour, minute, second, tz;
20	int crtime, days, i;
21
22	year = p[0] - 70;
23	month = p[1];
24	day = p[2];
25	hour = p[3];
26	minute = p[4];
27	second = p[5];
28	if (flag == 0) tz = p[6]; /* High sierra has no time zone */
29	else tz = 0;
30	
31	if (year < 0) {
32		crtime = 0;
33	} else {
34		int monlen[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
35
36		days = year * 365;
37		if (year > 2)
38			days += (year+1) / 4;
39		for (i = 1; i < month; i++)
40			days += monlen[i-1];
41		if (((year+2) % 4) == 0 && month > 2)
42			days++;
43		days += day - 1;
44		crtime = ((((days * 24) + hour) * 60 + minute) * 60)
45			+ second;
46
47		/* sign extend */
48		if (tz & 0x80)
49			tz |= (-1 << 8);
50		
51		/* 
52		 * The timezone offset is unreliable on some disks,
53		 * so we make a sanity check.  In no case is it ever
54		 * more than 13 hours from GMT, which is 52*15min.
55		 * The time is always stored in localtime with the
56		 * timezone offset being what get added to GMT to
57		 * get to localtime.  Thus we need to subtract the offset
58		 * to get to true GMT, which is what we store the time
59		 * as internally.  On the local system, the user may set
60		 * their timezone any way they wish, of course, so GMT
61		 * gets converted back to localtime on the receiving
62		 * system.
63		 *
64		 * NOTE: mkisofs in versions prior to mkisofs-1.10 had
65		 * the sign wrong on the timezone offset.  This has now
66		 * been corrected there too, but if you are getting screwy
67		 * results this may be the explanation.  If enough people
68		 * complain, a user configuration option could be added
69		 * to add the timezone offset in with the wrong sign
70		 * for 'compatibility' with older discs, but I cannot see how
71		 * it will matter that much.
72		 *
73		 * Thanks to kuhlmav@elec.canterbury.ac.nz (Volker Kuhlmann)
74		 * for pointing out the sign error.
75		 */
76		if (-52 <= tz && tz <= 52)
77			crtime -= tz * 15 * 60;
78	}
79	return crtime;
80}