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Diffstat (limited to 'exfat/libexfat/time.c')
| -rw-r--r-- | exfat/libexfat/time.c | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/exfat/libexfat/time.c b/exfat/libexfat/time.c new file mode 100644 index 000000000..890930eac --- /dev/null +++ b/exfat/libexfat/time.c @@ -0,0 +1,156 @@ +/* + time.c (03.02.12) + exFAT file system implementation library. + + Copyright (C) 2010-2012 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; +} |