3 exFAT file system implementation library.
5 Copyright (C) 2010-2012 Andrew Nayenko
7 This program is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
23 /* timezone offset from UTC in seconds; positive for western timezones,
24 negative for eastern ones */
25 static long exfat_timezone;
27 #define SEC_IN_MIN 60ll
28 #define SEC_IN_HOUR (60 * SEC_IN_MIN)
29 #define SEC_IN_DAY (24 * SEC_IN_HOUR)
30 #define SEC_IN_YEAR (365 * SEC_IN_DAY) /* not leap year */
31 /* Unix epoch started at 0:00:00 UTC 1 January 1970 */
32 #define UNIX_EPOCH_YEAR 1970
33 /* exFAT epoch started at 0:00:00 UTC 1 January 1980 */
34 #define EXFAT_EPOCH_YEAR 1980
35 /* number of years from Unix epoch to exFAT epoch */
36 #define EPOCH_DIFF_YEAR (EXFAT_EPOCH_YEAR - UNIX_EPOCH_YEAR)
37 /* number of days from Unix epoch to exFAT epoch (considering leap days) */
38 #define EPOCH_DIFF_DAYS (EPOCH_DIFF_YEAR * 365 + EPOCH_DIFF_YEAR / 4)
39 /* number of seconds from Unix epoch to exFAT epoch (considering leap days) */
40 #define EPOCH_DIFF_SEC (EPOCH_DIFF_DAYS * SEC_IN_DAY)
41 /* number of leap years passed from exFAT epoch to the specified year
42 (excluding the specified year itself) */
43 #define LEAP_YEARS(year) ((EXFAT_EPOCH_YEAR + (year) - 1) / 4 \
44 - (EXFAT_EPOCH_YEAR - 1) / 4)
45 /* checks whether the specified year is leap */
46 #define IS_LEAP_YEAR(year) ((EXFAT_EPOCH_YEAR + (year)) % 4 == 0)
48 static const time_t days_in_year[] =
50 /* Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec */
51 0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
54 time_t exfat_exfat2unix(le16_t date, le16_t time, uint8_t centisec)
56 time_t unix_time = EPOCH_DIFF_SEC;
57 uint16_t ndate = le16_to_cpu(date);
58 uint16_t ntime = le16_to_cpu(time);
60 uint16_t day = ndate & 0x1f; /* 5 bits, 1-31 */
61 uint16_t month = ndate >> 5 & 0xf; /* 4 bits, 1-12 */
62 uint16_t year = ndate >> 9; /* 7 bits, 1-127 (+1980) */
64 uint16_t twosec = ntime & 0x1f; /* 5 bits, 0-29 (2 sec granularity) */
65 uint16_t min = ntime >> 5 & 0x3f; /* 6 bits, 0-59 */
66 uint16_t hour = ntime >> 11; /* 5 bits, 0-23 */
68 if (day == 0 || month == 0 || month > 12)
70 exfat_error("bad date %u-%02hu-%02hu",
71 year + EXFAT_EPOCH_YEAR, month, day);
74 if (hour > 23 || min > 59 || twosec > 29)
76 exfat_error("bad time %hu:%02hu:%02u",
77 hour, min, twosec * 2);
82 exfat_error("bad centiseconds count %hhu", centisec);
86 /* every 4th year between 1904 and 2096 is leap */
87 unix_time += year * SEC_IN_YEAR + LEAP_YEARS(year) * SEC_IN_DAY;
88 unix_time += days_in_year[month] * SEC_IN_DAY;
89 /* if it's leap year and February has passed we should add 1 day */
90 if ((EXFAT_EPOCH_YEAR + year) % 4 == 0 && month > 2)
91 unix_time += SEC_IN_DAY;
92 unix_time += (day - 1) * SEC_IN_DAY;
94 unix_time += hour * SEC_IN_HOUR;
95 unix_time += min * SEC_IN_MIN;
96 /* exFAT represents time with 2 sec granularity */
97 unix_time += twosec * 2;
98 unix_time += centisec / 100;
100 /* exFAT stores timestamps in local time, so we correct it to UTC */
101 unix_time += exfat_timezone;
106 void exfat_unix2exfat(time_t unix_time, le16_t* date, le16_t* time,
109 time_t shift = EPOCH_DIFF_SEC + exfat_timezone;
110 uint16_t day, month, year;
111 uint16_t twosec, min, hour;
115 /* time before exFAT epoch cannot be represented */
116 if (unix_time < shift)
121 days = unix_time / SEC_IN_DAY;
122 year = (4 * days) / (4 * 365 + 1);
123 days -= year * 365 + LEAP_YEARS(year);
125 for (i = 1; i <= 12; i++)
127 int leap_day = (IS_LEAP_YEAR(year) && i == 2);
128 int leap_sub = (IS_LEAP_YEAR(year) && i >= 3);
130 if (i == 12 || days - leap_sub < days_in_year[i + 1] + leap_day)
133 days -= days_in_year[i] + leap_sub;
139 hour = (unix_time % SEC_IN_DAY) / SEC_IN_HOUR;
140 min = (unix_time % SEC_IN_HOUR) / SEC_IN_MIN;
141 twosec = (unix_time % SEC_IN_MIN) / 2;
143 *date = cpu_to_le16(day | (month << 5) | (year << 9));
144 *time = cpu_to_le16(twosec | (min << 5) | (hour << 11));
146 *centisec = (unix_time % 2) * 100;
149 void exfat_tzset(void)
155 exfat_timezone = mktime(gmtime(&now)) - now;