diff --git a/src/header/time/mod.rs b/src/header/time/mod.rs
index bb512797f8bcbc5dee593844f707c6d6bfb71c68..c22af065086b74ecdfa69d4b2fa4a06ff3452580 100644
--- a/src/header/time/mod.rs
+++ b/src/header/time/mod.rs
@@ -1,7 +1,9 @@
//! time implementation for Redox, following http://pubs.opengroup.org/onlinepubs/7908799/xsh/time.h.html
+use core::convert::{TryFrom, TryInto};
+
use crate::{
- header::errno::EIO,
+ header::errno::{EIO, EOVERFLOW},
platform::{self, types::*, Pal, Sys},
};
@@ -188,81 +190,92 @@ fn leap_year(year: c_int) -> bool {
#[no_mangle]
pub unsafe extern "C" fn gmtime_r(clock: *const time_t, result: *mut tm) -> *mut tm {
- let clock = *clock;
-
- let mut day = (clock / (60 * 60 * 24)) as c_int;
- if clock < 0 && clock % (60 * 60 * 24) != 0 {
- // -1 because for negative values round upwards
- // -0.3 == 0, but we want -1
- day -= 1;
- }
-
- (*result).tm_sec = (clock % 60) as c_int;
- (*result).tm_min = ((clock / 60) % 60) as c_int;
- (*result).tm_hour = ((clock / (60 * 60)) % 24) as c_int;
-
- while (*result).tm_sec < 0 {
- (*result).tm_sec += 60;
- (*result).tm_min -= 1;
- }
- while (*result).tm_min < 0 {
- (*result).tm_min += 60;
- (*result).tm_hour -= 1;
- }
- while (*result).tm_hour < 0 {
- (*result).tm_hour += 24;
- }
-
- // Jan 1th was a thursday, 4th of a zero-indexed week.
- (*result).tm_wday = (day + 4) % 7;
- if (*result).tm_wday < 0 {
- (*result).tm_wday += 7;
- }
-
- let mut year = 1970;
- if day < 0 {
- while day < 0 {
- let days_in_year = if leap_year(year) { 366 } else { 365 };
-
- day += days_in_year;
- year -= 1;
+ /* For the details of the algorithm used here, see
+ * http://howardhinnant.github.io/date_algorithms.html#civil_from_days
+ * Note that we need 0-based months here, though.
+ * Overall, this implementation should generate correct results as
+ * long as the tm_year value will fit in a c_int. */
+ const SECS_PER_DAY: time_t = 24*60*60;
+ const DAYS_PER_ERA: time_t = 146097;
+
+ let unix_secs = *clock;
+
+ /* Day number here is possibly negative, remainder will always be
+ * nonnegative when using Euclidean division */
+ let unix_days: time_t = unix_secs.div_euclid(SECS_PER_DAY);
+
+ /* In range [0, 86399]. Needs a u32 since this is larger (at least
+ * theoretically) than the guaranteed range of c_int */
+ let secs_of_day: u32 = unix_secs.rem_euclid(SECS_PER_DAY).try_into().unwrap();
+
+ /* Shift origin from 1970-01-01 to 0000-03-01 and find out where we
+ * are in terms of 400-year eras since then */
+ let days_since_origin = unix_days + 719468;
+ let era = days_since_origin.div_euclid(DAYS_PER_ERA);
+ let day_of_era = days_since_origin.rem_euclid(DAYS_PER_ERA);
+ let year_of_era = (day_of_era - day_of_era/1460 + day_of_era/36524 - day_of_era/146096) / 365;
+
+ /* "transformed" here refers to dates in a calendar where years
+ * start on March 1 */
+ let year_transformed = year_of_era + 400*era; // retain large range, don't convert to c_int yet
+ let day_of_year_transformed: c_int = (day_of_era - (365*year_of_era + year_of_era/4 - year_of_era/100)).try_into().unwrap();
+ let month_transformed: c_int = (5*day_of_year_transformed + 2)/153;
+
+ // Convert back to calendar with year starting on January 1
+ let month: c_int = (month_transformed + 2) % 12; // adapted to 0-based months
+ let year: time_t = if month < 2 {year_transformed + 1} else {year_transformed};
+
+ /* Subtract 1900 *before* converting down to c_int in order to
+ * maximize the range of input timestamps that will succeed */
+ match c_int::try_from(year - 1900) {
+ Ok(year_less_1900) => {
+ let mday: c_int = (day_of_year_transformed - (153*month_transformed+2)/5 + 1).try_into().unwrap();
+
+ /* 1970-01-01 was a Thursday. Again, Euclidean division is
+ * used to ensure a nonnegative remainder (range [0, 6]). */
+ let wday: c_int = ((unix_days + 4).rem_euclid(7)).try_into().unwrap();
+
+ /* Yes, duplicated code for now (to work on non-c_int-values
+ * so that we are not constrained by the subtraction of
+ * 1900) */
+ let is_leap_year: bool = year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
+
+ /* For dates that are March 1 or later, we can use day-of-
+ * year in the transformed calendar. For January and
+ * February, that value is sensitive to whether the previous
+ * year is a leap year. Therefore, we use the already
+ * computed date for those two months. */
+ let yday: c_int = match month {
+ 0 => mday - 1, // January
+ 1 => 31 + mday - 1, // February
+ _ => day_of_year_transformed + if is_leap_year {60} else {59},
+ };
+
+ let hour: c_int = (secs_of_day / (60*60)).try_into().unwrap();
+ let min: c_int = ((secs_of_day / 60) % 60).try_into().unwrap();
+ let sec: c_int = (secs_of_day % 60).try_into().unwrap();
+
+ *result = tm {
+ tm_sec: sec,
+ tm_min: min,
+ tm_hour: hour,
+ tm_mday: mday,
+ tm_mon: month,
+ tm_year: year_less_1900,
+ tm_wday: wday,
+ tm_yday: yday,
+ tm_isdst: 0,
+ tm_gmtoff: 0,
+ tm_zone: UTC,
+ };
+
+ result
}
- (*result).tm_year = year - 1900;
- (*result).tm_yday = day + 1;
- } else {
- loop {
- let days_in_year = if leap_year(year) { 366 } else { 365 };
-
- if day < days_in_year {
- break;
- }
-
- day -= days_in_year;
- year += 1;
- }
- (*result).tm_year = year - 1900;
- (*result).tm_yday = day;
- }
-
- let leap = if leap_year(year) { 1 } else { 0 };
- (*result).tm_mon = 0;
- loop {
- let days_in_month = MONTH_DAYS[leap][(*result).tm_mon as usize];
-
- if day < days_in_month {
- break;
+ Err(_) => {
+ platform::errno = EOVERFLOW;
+ core::ptr::null_mut()
}
-
- day -= days_in_month;
- (*result).tm_mon += 1;
}
- (*result).tm_mday = 1 + day as c_int;
-
- (*result).tm_isdst = 0;
- (*result).tm_gmtoff = 0;
- (*result).tm_zone = UTC;
-
- result
}
#[no_mangle]