--- /dev/null
+/*
+ time.c (03.02.12)
+ exFAT file system implementation library.
+
+ Copyright (C) 2009, 2010 Andrew Nayenko
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "exfat.h"
+
+/* timezone offset from UTC in seconds; positive for western timezones,
+ negative for eastern ones */
+static long exfat_timezone;
+
+#define SEC_IN_MIN 60ll
+#define SEC_IN_HOUR (60 * SEC_IN_MIN)
+#define SEC_IN_DAY (24 * SEC_IN_HOUR)
+#define SEC_IN_YEAR (365 * SEC_IN_DAY) /* not leap year */
+/* Unix epoch started at 0:00:00 UTC 1 January 1970 */
+#define UNIX_EPOCH_YEAR 1970
+/* exFAT epoch started at 0:00:00 UTC 1 January 1980 */
+#define EXFAT_EPOCH_YEAR 1980
+/* number of years from Unix epoch to exFAT epoch */
+#define EPOCH_DIFF_YEAR (EXFAT_EPOCH_YEAR - UNIX_EPOCH_YEAR)
+/* number of days from Unix epoch to exFAT epoch (considering leap days) */
+#define EPOCH_DIFF_DAYS (EPOCH_DIFF_YEAR * 365 + EPOCH_DIFF_YEAR / 4)
+/* number of seconds from Unix epoch to exFAT epoch (considering leap days) */
+#define EPOCH_DIFF_SEC (EPOCH_DIFF_DAYS * SEC_IN_DAY)
+/* number of leap years passed from exFAT epoch to the specified year
+ (excluding the specified year itself) */
+#define LEAP_YEARS(year) ((EXFAT_EPOCH_YEAR + (year) - 1) / 4 \
+ - (EXFAT_EPOCH_YEAR - 1) / 4)
+/* checks whether the specified year is leap */
+#define IS_LEAP_YEAR(year) ((EXFAT_EPOCH_YEAR + (year)) % 4 == 0)
+
+static const time_t days_in_year[] =
+{
+ /* Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec */
+ 0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
+};
+
+time_t exfat_exfat2unix(le16_t date, le16_t time, uint8_t centisec)
+{
+ time_t unix_time = EPOCH_DIFF_SEC;
+ uint16_t ndate = le16_to_cpu(date);
+ uint16_t ntime = le16_to_cpu(time);
+
+ uint16_t day = ndate & 0x1f; /* 5 bits, 1-31 */
+ uint16_t month = ndate >> 5 & 0xf; /* 4 bits, 1-12 */
+ uint16_t year = ndate >> 9; /* 7 bits, 1-127 (+1980) */
+
+ uint16_t twosec = ntime & 0x1f; /* 5 bits, 0-29 (2 sec granularity) */
+ uint16_t min = ntime >> 5 & 0x3f; /* 6 bits, 0-59 */
+ uint16_t hour = ntime >> 11; /* 5 bits, 0-23 */
+
+ if (day == 0 || month == 0 || month > 12)
+ {
+ exfat_error("bad date %u-%02hu-%02hu",
+ year + EXFAT_EPOCH_YEAR, month, day);
+ return 0;
+ }
+ if (hour > 23 || min > 59 || twosec > 29)
+ {
+ exfat_error("bad time %hu:%02hu:%02u",
+ hour, min, twosec * 2);
+ return 0;
+ }
+ if (centisec > 199)
+ {
+ exfat_error("bad centiseconds count %hhu", centisec);
+ return 0;
+ }
+
+ /* every 4th year between 1904 and 2096 is leap */
+ unix_time += year * SEC_IN_YEAR + LEAP_YEARS(year) * SEC_IN_DAY;
+ unix_time += days_in_year[month] * SEC_IN_DAY;
+ /* if it's leap year and February has passed we should add 1 day */
+ if ((EXFAT_EPOCH_YEAR + year) % 4 == 0 && month > 2)
+ unix_time += SEC_IN_DAY;
+ unix_time += (day - 1) * SEC_IN_DAY;
+
+ unix_time += hour * SEC_IN_HOUR;
+ unix_time += min * SEC_IN_MIN;
+ /* exFAT represents time with 2 sec granularity */
+ unix_time += twosec * 2;
+ unix_time += centisec / 100;
+
+ /* exFAT stores timestamps in local time, so we correct it to UTC */
+ unix_time += exfat_timezone;
+
+ return unix_time;
+}
+
+void exfat_unix2exfat(time_t unix_time, le16_t* date, le16_t* time,
+ uint8_t* centisec)
+{
+ time_t shift = EPOCH_DIFF_SEC + exfat_timezone;
+ uint16_t day, month, year;
+ uint16_t twosec, min, hour;
+ int days;
+ int i;
+
+ /* time before exFAT epoch cannot be represented */
+ if (unix_time < shift)
+ unix_time = shift;
+
+ unix_time -= shift;
+
+ days = unix_time / SEC_IN_DAY;
+ year = (4 * days) / (4 * 365 + 1);
+ days -= year * 365 + LEAP_YEARS(year);
+ month = 0;
+ for (i = 1; i <= 12; i++)
+ {
+ int leap_day = (IS_LEAP_YEAR(year) && i == 2);
+ int leap_sub = (IS_LEAP_YEAR(year) && i >= 3);
+
+ if (i == 12 || days - leap_sub < days_in_year[i + 1] + leap_day)
+ {
+ month = i;
+ days -= days_in_year[i] + leap_sub;
+ break;
+ }
+ }
+ day = days + 1;
+
+ hour = (unix_time % SEC_IN_DAY) / SEC_IN_HOUR;
+ min = (unix_time % SEC_IN_HOUR) / SEC_IN_MIN;
+ twosec = (unix_time % SEC_IN_MIN) / 2;
+
+ *date = cpu_to_le16(day | (month << 5) | (year << 9));
+ *time = cpu_to_le16(twosec | (min << 5) | (hour << 11));
+ if (centisec)
+ *centisec = (unix_time % 2) * 100;
+}
+
+void exfat_tzset(void)
+{
+ time_t now;
+
+ tzset();
+ now = time(NULL);
+ exfat_timezone = mktime(gmtime(&now)) - now;
+}
projects / sven / exfat-utils.git / blobdiff