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pitdickerpitdicker
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Windows: rewrite using GetTimeZoneInformationForYear
And add test against previous implementation
1 parent 5fb4fab commit acb693a

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5 files changed

+526
-106
lines changed

5 files changed

+526
-106
lines changed

‎src/naive/datetime/mod.rs

+17
Original file line numberDiff line numberDiff line change
@@ -790,6 +790,23 @@ impl NaiveDateTime {
790790
NaiveDateTime { date, time }
791791
}
792792

793+
/// Subtracts given `FixedOffset` from the current datetime.
794+
/// The resulting value may be outside the valid range of [`NaiveDateTime`].
795+
///
796+
/// This can be useful for intermediate values, but the resulting out-of-range `NaiveDate`
797+
/// should not be exposed to library users.
798+
#[must_use]
799+
#[allow(unused)] // currently only used in `Local` but not on all platforms
800+
pub(crate) fn overflowing_sub_offset(self, rhs: FixedOffset) -> NaiveDateTime {
801+
let (time, days) = self.time.overflowing_sub_offset(rhs);
802+
let date = match days {
803+
-1 => self.date.pred_opt().unwrap_or(NaiveDate::BEFORE_MIN),
804+
1 => self.date.succ_opt().unwrap_or(NaiveDate::AFTER_MAX),
805+
_ => self.date,
806+
};
807+
NaiveDateTime { date, time }
808+
}
809+
793810
/// Subtracts given `TimeDelta` from the current date and time.
794811
///
795812
/// As a part of Chrono's [leap second handling](./struct.NaiveTime.html#leap-second-handling),

‎src/offset/local/mod.rs

+259
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,9 @@
33

44
//! The local (system) time zone.
55
6+
#[cfg(windows)]
7+
use std::cmp::Ordering;
8+
69
#[cfg(any(feature = "rkyv", feature = "rkyv-16", feature = "rkyv-32", feature = "rkyv-64"))]
710
use rkyv::{Archive, Deserialize, Serialize};
811

@@ -183,11 +186,96 @@ impl TimeZone for Local {
183186
}
184187
}
185188

189+
#[cfg(windows)]
190+
#[derive(Copy, Clone, Eq, PartialEq)]
191+
struct Transition {
192+
transition_utc: NaiveDateTime,
193+
offset_before: FixedOffset,
194+
offset_after: FixedOffset,
195+
}
196+
197+
#[cfg(windows)]
198+
impl Transition {
199+
fn new(
200+
transition_local: NaiveDateTime,
201+
offset_before: FixedOffset,
202+
offset_after: FixedOffset,
203+
) -> Transition {
204+
// It is no problem if the transition time in UTC falls a couple of hours inside the buffer
205+
// space around the `NaiveDateTime` range (although it is very theoretical to have a
206+
// transition at midnight around `NaiveDate::(MIN|MAX)`.
207+
let transition_utc = transition_local.overflowing_sub_offset(offset_before);
208+
Transition { transition_utc, offset_before, offset_after }
209+
}
210+
}
211+
212+
#[cfg(windows)]
213+
impl PartialOrd for Transition {
214+
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
215+
Some(self.transition_utc.cmp(&other.transition_utc))
216+
}
217+
}
218+
219+
#[cfg(windows)]
220+
impl Ord for Transition {
221+
fn cmp(&self, other: &Self) -> Ordering {
222+
self.transition_utc.cmp(&other.transition_utc)
223+
}
224+
}
225+
226+
// Calculate the time in UTC given a local time and transitions.
227+
// `transitions` must be sorted.
228+
#[cfg(windows)]
229+
fn lookup_with_dst_transitions(
230+
transitions: &[Transition],
231+
dt: NaiveDateTime,
232+
) -> LocalResult<FixedOffset> {
233+
for t in transitions.iter() {
234+
// A transition can result in the wall clock time going forward (creating a gap) or going
235+
// backward (creating a fold). We are interested in the earliest and latest wall time of the
236+
// transition, as this are the times between which `dt` does may not exist or is ambiguous.
237+
//
238+
// It is no problem if the transition times falls a couple of hours inside the buffer
239+
// space around the `NaiveDateTime` range (although it is very theoretical to have a
240+
// transition at midnight around `NaiveDate::(MIN|MAX)`.
241+
let (offset_min, offset_max) =
242+
match t.offset_after.local_minus_utc() > t.offset_before.local_minus_utc() {
243+
true => (t.offset_before, t.offset_after),
244+
false => (t.offset_after, t.offset_before),
245+
};
246+
let wall_earliest = t.transition_utc.overflowing_add_offset(offset_min);
247+
let wall_latest = t.transition_utc.overflowing_add_offset(offset_max);
248+
249+
if dt < wall_earliest {
250+
return LocalResult::Single(t.offset_before);
251+
} else if dt <= wall_latest {
252+
return match t.offset_after.local_minus_utc().cmp(&t.offset_before.local_minus_utc()) {
253+
Ordering::Equal => LocalResult::Single(t.offset_before),
254+
Ordering::Less => LocalResult::Ambiguous(t.offset_before, t.offset_after),
255+
Ordering::Greater => {
256+
if dt == wall_earliest {
257+
LocalResult::Single(t.offset_before)
258+
} else if dt == wall_latest {
259+
LocalResult::Single(t.offset_after)
260+
} else {
261+
LocalResult::None
262+
}
263+
}
264+
};
265+
}
266+
}
267+
LocalResult::Single(transitions.last().unwrap().offset_after)
268+
}
269+
186270
#[cfg(test)]
187271
mod tests {
188272
use super::Local;
273+
#[cfg(windows)]
274+
use crate::offset::local::{lookup_with_dst_transitions, Transition};
189275
use crate::offset::TimeZone;
190276
use crate::{Datelike, TimeDelta, Utc};
277+
#[cfg(windows)]
278+
use crate::{FixedOffset, LocalResult, NaiveDate, NaiveDateTime};
191279

192280
#[test]
193281
fn verify_correct_offsets() {
@@ -264,6 +352,177 @@ mod tests {
264352
}
265353
}
266354

355+
#[test]
356+
#[cfg(windows)]
357+
fn test_lookup_with_dst_transitions() {
358+
let ymdhms = |y, m, d, h, n, s| {
359+
NaiveDate::from_ymd_opt(y, m, d).unwrap().and_hms_opt(h, n, s).unwrap()
360+
};
361+
362+
#[track_caller]
363+
#[allow(clippy::too_many_arguments)]
364+
fn compare_lookup(
365+
transitions: &[Transition],
366+
y: i32,
367+
m: u32,
368+
d: u32,
369+
h: u32,
370+
n: u32,
371+
s: u32,
372+
result: LocalResult<FixedOffset>,
373+
) {
374+
let dt = NaiveDate::from_ymd_opt(y, m, d).unwrap().and_hms_opt(h, n, s).unwrap();
375+
assert_eq!(lookup_with_dst_transitions(transitions, dt), result);
376+
}
377+
378+
// dst transition before std transition
379+
// dst offset > std offset
380+
let std = FixedOffset::east_opt(3 * 60 * 60).unwrap();
381+
let dst = FixedOffset::east_opt(4 * 60 * 60).unwrap();
382+
let transitions = [
383+
Transition::new(ymdhms(2023, 3, 26, 2, 0, 0), std, dst),
384+
Transition::new(ymdhms(2023, 10, 29, 3, 0, 0), dst, std),
385+
];
386+
compare_lookup(&transitions, 2023, 3, 26, 1, 0, 0, LocalResult::Single(std));
387+
compare_lookup(&transitions, 2023, 3, 26, 2, 0, 0, LocalResult::Single(std));
388+
compare_lookup(&transitions, 2023, 3, 26, 2, 30, 0, LocalResult::None);
389+
compare_lookup(&transitions, 2023, 3, 26, 3, 0, 0, LocalResult::Single(dst));
390+
compare_lookup(&transitions, 2023, 3, 26, 4, 0, 0, LocalResult::Single(dst));
391+
392+
compare_lookup(&transitions, 2023, 10, 29, 1, 0, 0, LocalResult::Single(dst));
393+
compare_lookup(&transitions, 2023, 10, 29, 2, 0, 0, LocalResult::Ambiguous(dst, std));
394+
compare_lookup(&transitions, 2023, 10, 29, 2, 30, 0, LocalResult::Ambiguous(dst, std));
395+
compare_lookup(&transitions, 2023, 10, 29, 3, 0, 0, LocalResult::Ambiguous(dst, std));
396+
compare_lookup(&transitions, 2023, 10, 29, 4, 0, 0, LocalResult::Single(std));
397+
398+
// std transition before dst transition
399+
// dst offset > std offset
400+
let std = FixedOffset::east_opt(-5 * 60 * 60).unwrap();
401+
let dst = FixedOffset::east_opt(-4 * 60 * 60).unwrap();
402+
let transitions = [
403+
Transition::new(ymdhms(2023, 3, 24, 3, 0, 0), dst, std),
404+
Transition::new(ymdhms(2023, 10, 27, 2, 0, 0), std, dst),
405+
];
406+
compare_lookup(&transitions, 2023, 3, 24, 1, 0, 0, LocalResult::Single(dst));
407+
compare_lookup(&transitions, 2023, 3, 24, 2, 0, 0, LocalResult::Ambiguous(dst, std));
408+
compare_lookup(&transitions, 2023, 3, 24, 2, 30, 0, LocalResult::Ambiguous(dst, std));
409+
compare_lookup(&transitions, 2023, 3, 24, 3, 0, 0, LocalResult::Ambiguous(dst, std));
410+
compare_lookup(&transitions, 2023, 3, 24, 4, 0, 0, LocalResult::Single(std));
411+
412+
compare_lookup(&transitions, 2023, 10, 27, 1, 0, 0, LocalResult::Single(std));
413+
compare_lookup(&transitions, 2023, 10, 27, 2, 0, 0, LocalResult::Single(std));
414+
compare_lookup(&transitions, 2023, 10, 27, 2, 30, 0, LocalResult::None);
415+
compare_lookup(&transitions, 2023, 10, 27, 3, 0, 0, LocalResult::Single(dst));
416+
compare_lookup(&transitions, 2023, 10, 27, 4, 0, 0, LocalResult::Single(dst));
417+
418+
// dst transition before std transition
419+
// dst offset < std offset
420+
let std = FixedOffset::east_opt(3 * 60 * 60).unwrap();
421+
let dst = FixedOffset::east_opt((2 * 60 + 30) * 60).unwrap();
422+
let transitions = [
423+
Transition::new(ymdhms(2023, 3, 26, 2, 30, 0), std, dst),
424+
Transition::new(ymdhms(2023, 10, 29, 2, 0, 0), dst, std),
425+
];
426+
compare_lookup(&transitions, 2023, 3, 26, 1, 0, 0, LocalResult::Single(std));
427+
compare_lookup(&transitions, 2023, 3, 26, 2, 0, 0, LocalResult::Ambiguous(std, dst));
428+
compare_lookup(&transitions, 2023, 3, 26, 2, 15, 0, LocalResult::Ambiguous(std, dst));
429+
compare_lookup(&transitions, 2023, 3, 26, 2, 30, 0, LocalResult::Ambiguous(std, dst));
430+
compare_lookup(&transitions, 2023, 3, 26, 3, 0, 0, LocalResult::Single(dst));
431+
432+
compare_lookup(&transitions, 2023, 10, 29, 1, 0, 0, LocalResult::Single(dst));
433+
compare_lookup(&transitions, 2023, 10, 29, 2, 0, 0, LocalResult::Single(dst));
434+
compare_lookup(&transitions, 2023, 10, 29, 2, 15, 0, LocalResult::None);
435+
compare_lookup(&transitions, 2023, 10, 29, 2, 30, 0, LocalResult::Single(std));
436+
compare_lookup(&transitions, 2023, 10, 29, 3, 0, 0, LocalResult::Single(std));
437+
438+
// std transition before dst transition
439+
// dst offset < std offset
440+
let std = FixedOffset::east_opt(-(4 * 60 + 30) * 60).unwrap();
441+
let dst = FixedOffset::east_opt(-5 * 60 * 60).unwrap();
442+
let transitions = [
443+
Transition::new(ymdhms(2023, 3, 24, 2, 0, 0), dst, std),
444+
Transition::new(ymdhms(2023, 10, 27, 2, 30, 0), std, dst),
445+
];
446+
compare_lookup(&transitions, 2023, 3, 24, 1, 0, 0, LocalResult::Single(dst));
447+
compare_lookup(&transitions, 2023, 3, 24, 2, 0, 0, LocalResult::Single(dst));
448+
compare_lookup(&transitions, 2023, 3, 24, 2, 15, 0, LocalResult::None);
449+
compare_lookup(&transitions, 2023, 3, 24, 2, 30, 0, LocalResult::Single(std));
450+
compare_lookup(&transitions, 2023, 3, 24, 3, 0, 0, LocalResult::Single(std));
451+
452+
compare_lookup(&transitions, 2023, 10, 27, 1, 0, 0, LocalResult::Single(std));
453+
compare_lookup(&transitions, 2023, 10, 27, 2, 0, 0, LocalResult::Ambiguous(std, dst));
454+
compare_lookup(&transitions, 2023, 10, 27, 2, 15, 0, LocalResult::Ambiguous(std, dst));
455+
compare_lookup(&transitions, 2023, 10, 27, 2, 30, 0, LocalResult::Ambiguous(std, dst));
456+
compare_lookup(&transitions, 2023, 10, 27, 3, 0, 0, LocalResult::Single(dst));
457+
458+
// offset stays the same
459+
let std = FixedOffset::east_opt(3 * 60 * 60).unwrap();
460+
let transitions = [
461+
Transition::new(ymdhms(2023, 3, 26, 2, 0, 0), std, std),
462+
Transition::new(ymdhms(2023, 10, 29, 3, 0, 0), std, std),
463+
];
464+
compare_lookup(&transitions, 2023, 3, 26, 2, 0, 0, LocalResult::Single(std));
465+
compare_lookup(&transitions, 2023, 10, 29, 3, 0, 0, LocalResult::Single(std));
466+
467+
// single transition
468+
let std = FixedOffset::east_opt(3 * 60 * 60).unwrap();
469+
let dst = FixedOffset::east_opt(4 * 60 * 60).unwrap();
470+
let transitions = [Transition::new(ymdhms(2023, 3, 26, 2, 0, 0), std, dst)];
471+
compare_lookup(&transitions, 2023, 3, 26, 1, 0, 0, LocalResult::Single(std));
472+
compare_lookup(&transitions, 2023, 3, 26, 2, 0, 0, LocalResult::Single(std));
473+
compare_lookup(&transitions, 2023, 3, 26, 2, 30, 0, LocalResult::None);
474+
compare_lookup(&transitions, 2023, 3, 26, 3, 0, 0, LocalResult::Single(dst));
475+
compare_lookup(&transitions, 2023, 3, 26, 4, 0, 0, LocalResult::Single(dst));
476+
}
477+
478+
#[test]
479+
#[cfg(windows)]
480+
fn test_lookup_with_dst_transitions_limits() {
481+
// Transition beyond UTC year end doesn't panic in year of `NaiveDate::MAX`
482+
let std = FixedOffset::east_opt(3 * 60 * 60).unwrap();
483+
let dst = FixedOffset::east_opt(4 * 60 * 60).unwrap();
484+
let transitions = [
485+
Transition::new(NaiveDateTime::MAX.with_month(7).unwrap(), std, dst),
486+
Transition::new(NaiveDateTime::MAX, dst, std),
487+
];
488+
assert_eq!(
489+
lookup_with_dst_transitions(&transitions, NaiveDateTime::MAX.with_month(3).unwrap()),
490+
LocalResult::Single(std)
491+
);
492+
assert_eq!(
493+
lookup_with_dst_transitions(&transitions, NaiveDateTime::MAX.with_month(8).unwrap()),
494+
LocalResult::Single(dst)
495+
);
496+
// Doesn't panic with `NaiveDateTime::MAX` as argument (which would be out of range when
497+
// converted to UTC).
498+
assert_eq!(
499+
lookup_with_dst_transitions(&transitions, NaiveDateTime::MAX),
500+
LocalResult::Ambiguous(dst, std)
501+
);
502+
503+
// Transition before UTC year end doesn't panic in year of `NaiveDate::MIN`
504+
let std = FixedOffset::west_opt(3 * 60 * 60).unwrap();
505+
let dst = FixedOffset::west_opt(4 * 60 * 60).unwrap();
506+
let transitions = [
507+
Transition::new(NaiveDateTime::MIN, std, dst),
508+
Transition::new(NaiveDateTime::MIN.with_month(6).unwrap(), dst, std),
509+
];
510+
assert_eq!(
511+
lookup_with_dst_transitions(&transitions, NaiveDateTime::MIN.with_month(3).unwrap()),
512+
LocalResult::Single(dst)
513+
);
514+
assert_eq!(
515+
lookup_with_dst_transitions(&transitions, NaiveDateTime::MIN.with_month(8).unwrap()),
516+
LocalResult::Single(std)
517+
);
518+
// Doesn't panic with `NaiveDateTime::MIN` as argument (which would be out of range when
519+
// converted to UTC).
520+
assert_eq!(
521+
lookup_with_dst_transitions(&transitions, NaiveDateTime::MIN),
522+
LocalResult::Ambiguous(std, dst)
523+
);
524+
}
525+
267526
#[test]
268527
#[cfg(feature = "rkyv-validation")]
269528
fn test_rkyv_validation() {

‎src/offset/local/win_bindings.rs

+20
Original file line numberDiff line numberDiff line change
@@ -1,10 +1,30 @@
11
// Bindings generated by `windows-bindgen` 0.52.0
22

33
#![allow(non_snake_case, non_upper_case_globals, non_camel_case_types, dead_code, clippy::all)]
4+
::windows_targets::link!("kernel32.dll" "system" fn GetTimeZoneInformationForYear(wyear : u16, pdtzi : *const DYNAMIC_TIME_ZONE_INFORMATION, ptzi : *mut TIME_ZONE_INFORMATION) -> BOOL);
45
::windows_targets::link!("kernel32.dll" "system" fn SystemTimeToFileTime(lpsystemtime : *const SYSTEMTIME, lpfiletime : *mut FILETIME) -> BOOL);
56
::windows_targets::link!("kernel32.dll" "system" fn SystemTimeToTzSpecificLocalTime(lptimezoneinformation : *const TIME_ZONE_INFORMATION, lpuniversaltime : *const SYSTEMTIME, lplocaltime : *mut SYSTEMTIME) -> BOOL);
67
::windows_targets::link!("kernel32.dll" "system" fn TzSpecificLocalTimeToSystemTime(lptimezoneinformation : *const TIME_ZONE_INFORMATION, lplocaltime : *const SYSTEMTIME, lpuniversaltime : *mut SYSTEMTIME) -> BOOL);
78
pub type BOOL = i32;
9+
pub type BOOLEAN = u8;
10+
#[repr(C)]
11+
pub struct DYNAMIC_TIME_ZONE_INFORMATION {
12+
pub Bias: i32,
13+
pub StandardName: [u16; 32],
14+
pub StandardDate: SYSTEMTIME,
15+
pub StandardBias: i32,
16+
pub DaylightName: [u16; 32],
17+
pub DaylightDate: SYSTEMTIME,
18+
pub DaylightBias: i32,
19+
pub TimeZoneKeyName: [u16; 128],
20+
pub DynamicDaylightTimeDisabled: BOOLEAN,
21+
}
22+
impl ::core::marker::Copy for DYNAMIC_TIME_ZONE_INFORMATION {}
23+
impl ::core::clone::Clone for DYNAMIC_TIME_ZONE_INFORMATION {
24+
fn clone(&self) -> Self {
25+
*self
26+
}
27+
}
828
#[repr(C)]
929
pub struct FILETIME {
1030
pub dwLowDateTime: u32,

‎src/offset/local/win_bindings.txt

+1
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
11
--out src/offset/local/win_bindings.rs
22
--config flatten sys
33
--filter
4+
Windows.Win32.System.Time.GetTimeZoneInformationForYear
45
Windows.Win32.System.Time.SystemTimeToFileTime
56
Windows.Win32.System.Time.SystemTimeToTzSpecificLocalTime
67
Windows.Win32.System.Time.TzSpecificLocalTimeToSystemTime

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