1use std::cmp::Ordering;
2
3use super::parser::Cursor;
4use super::timezone::{LocalTimeType, SECONDS_PER_WEEK};
5use super::{
6 Error, CUMUL_DAY_IN_MONTHS_NORMAL_YEAR, DAYS_PER_WEEK, DAY_IN_MONTHS_NORMAL_YEAR,
7 SECONDS_PER_DAY,
8};
9
10/// Transition rule
11#[derive(Debug, Copy, Clone, Eq, PartialEq)]
12pub(super) enum TransitionRule {
13 /// Fixed local time type
14 Fixed(LocalTimeType),
15 /// Alternate local time types
16 Alternate(AlternateTime),
17}
18
19impl TransitionRule {
20 /// Parse a POSIX TZ string containing a time zone description, as described in [the POSIX documentation of the `TZ` environment variable](https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html).
21 ///
22 /// TZ string extensions from [RFC 8536](https://datatracker.ietf.org/doc/html/rfc8536#section-3.3.1) may be used.
23 ///
24 pub(super) fn from_tz_string(
25 tz_string: &[u8],
26 use_string_extensions: bool,
27 ) -> Result<Self, Error> {
28 let mut cursor = Cursor::new(tz_string);
29
30 let std_time_zone = Some(parse_name(&mut cursor)?);
31 let std_offset = parse_offset(&mut cursor)?;
32
33 if cursor.is_empty() {
34 return Ok(LocalTimeType::new(-std_offset, false, std_time_zone)?.into());
35 }
36
37 let dst_time_zone = Some(parse_name(&mut cursor)?);
38
39 let dst_offset = match cursor.peek() {
40 Some(&b',') => std_offset - 3600,
41 Some(_) => parse_offset(&mut cursor)?,
42 None => {
43 return Err(Error::UnsupportedTzString("DST start and end rules must be provided"))
44 }
45 };
46
47 if cursor.is_empty() {
48 return Err(Error::UnsupportedTzString("DST start and end rules must be provided"));
49 }
50
51 cursor.read_tag(b",")?;
52 let (dst_start, dst_start_time) = RuleDay::parse(&mut cursor, use_string_extensions)?;
53
54 cursor.read_tag(b",")?;
55 let (dst_end, dst_end_time) = RuleDay::parse(&mut cursor, use_string_extensions)?;
56
57 if !cursor.is_empty() {
58 return Err(Error::InvalidTzString("remaining data after parsing TZ string"));
59 }
60
61 Ok(AlternateTime::new(
62 LocalTimeType::new(-std_offset, false, std_time_zone)?,
63 LocalTimeType::new(-dst_offset, true, dst_time_zone)?,
64 dst_start,
65 dst_start_time,
66 dst_end,
67 dst_end_time,
68 )?
69 .into())
70 }
71
72 /// Find the local time type associated to the transition rule at the specified Unix time in seconds
73 pub(super) fn find_local_time_type(&self, unix_time: i64) -> Result<&LocalTimeType, Error> {
74 match self {
75 TransitionRule::Fixed(local_time_type) => Ok(local_time_type),
76 TransitionRule::Alternate(alternate_time) => {
77 alternate_time.find_local_time_type(unix_time)
78 }
79 }
80 }
81
82 /// Find the local time type associated to the transition rule at the specified Unix time in seconds
83 pub(super) fn find_local_time_type_from_local(
84 &self,
85 local_time: i64,
86 year: i32,
87 ) -> Result<crate::LocalResult<LocalTimeType>, Error> {
88 match self {
89 TransitionRule::Fixed(local_time_type) => {
90 Ok(crate::LocalResult::Single(*local_time_type))
91 }
92 TransitionRule::Alternate(alternate_time) => {
93 alternate_time.find_local_time_type_from_local(local_time, year)
94 }
95 }
96 }
97}
98
99impl From<LocalTimeType> for TransitionRule {
100 fn from(inner: LocalTimeType) -> Self {
101 TransitionRule::Fixed(inner)
102 }
103}
104
105impl From<AlternateTime> for TransitionRule {
106 fn from(inner: AlternateTime) -> Self {
107 TransitionRule::Alternate(inner)
108 }
109}
110
111/// Transition rule representing alternate local time types
112#[derive(Debug, Copy, Clone, Eq, PartialEq)]
113pub(super) struct AlternateTime {
114 /// Local time type for standard time
115 pub(super) std: LocalTimeType,
116 /// Local time type for Daylight Saving Time
117 pub(super) dst: LocalTimeType,
118 /// Start day of Daylight Saving Time
119 dst_start: RuleDay,
120 /// Local start day time of Daylight Saving Time, in seconds
121 dst_start_time: i32,
122 /// End day of Daylight Saving Time
123 dst_end: RuleDay,
124 /// Local end day time of Daylight Saving Time, in seconds
125 dst_end_time: i32,
126}
127
128impl AlternateTime {
129 /// Construct a transition rule representing alternate local time types
130 const fn new(
131 std: LocalTimeType,
132 dst: LocalTimeType,
133 dst_start: RuleDay,
134 dst_start_time: i32,
135 dst_end: RuleDay,
136 dst_end_time: i32,
137 ) -> Result<Self, Error> {
138 // Overflow is not possible
139 if !((dst_start_time as i64).abs() < SECONDS_PER_WEEK
140 && (dst_end_time as i64).abs() < SECONDS_PER_WEEK)
141 {
142 return Err(Error::TransitionRule("invalid DST start or end time"));
143 }
144
145 Ok(Self { std, dst, dst_start, dst_start_time, dst_end, dst_end_time })
146 }
147
148 /// Find the local time type associated to the alternate transition rule at the specified Unix time in seconds
149 fn find_local_time_type(&self, unix_time: i64) -> Result<&LocalTimeType, Error> {
150 // Overflow is not possible
151 let dst_start_time_in_utc = self.dst_start_time as i64 - self.std.ut_offset as i64;
152 let dst_end_time_in_utc = self.dst_end_time as i64 - self.dst.ut_offset as i64;
153
154 let current_year = match UtcDateTime::from_timespec(unix_time) {
155 Ok(dt) => dt.year,
156 Err(error) => return Err(error),
157 };
158
159 // Check if the current year is valid for the following computations
160 if !(i32::min_value() + 2 <= current_year && current_year <= i32::max_value() - 2) {
161 return Err(Error::OutOfRange("out of range date time"));
162 }
163
164 let current_year_dst_start_unix_time =
165 self.dst_start.unix_time(current_year, dst_start_time_in_utc);
166 let current_year_dst_end_unix_time =
167 self.dst_end.unix_time(current_year, dst_end_time_in_utc);
168
169 // Check DST start/end Unix times for previous/current/next years to support for transition day times outside of [0h, 24h] range
170 let is_dst =
171 match Ord::cmp(&current_year_dst_start_unix_time, &current_year_dst_end_unix_time) {
172 Ordering::Less | Ordering::Equal => {
173 if unix_time < current_year_dst_start_unix_time {
174 let previous_year_dst_end_unix_time =
175 self.dst_end.unix_time(current_year - 1, dst_end_time_in_utc);
176 if unix_time < previous_year_dst_end_unix_time {
177 let previous_year_dst_start_unix_time =
178 self.dst_start.unix_time(current_year - 1, dst_start_time_in_utc);
179 previous_year_dst_start_unix_time <= unix_time
180 } else {
181 false
182 }
183 } else if unix_time < current_year_dst_end_unix_time {
184 true
185 } else {
186 let next_year_dst_start_unix_time =
187 self.dst_start.unix_time(current_year + 1, dst_start_time_in_utc);
188 if next_year_dst_start_unix_time <= unix_time {
189 let next_year_dst_end_unix_time =
190 self.dst_end.unix_time(current_year + 1, dst_end_time_in_utc);
191 unix_time < next_year_dst_end_unix_time
192 } else {
193 false
194 }
195 }
196 }
197 Ordering::Greater => {
198 if unix_time < current_year_dst_end_unix_time {
199 let previous_year_dst_start_unix_time =
200 self.dst_start.unix_time(current_year - 1, dst_start_time_in_utc);
201 if unix_time < previous_year_dst_start_unix_time {
202 let previous_year_dst_end_unix_time =
203 self.dst_end.unix_time(current_year - 1, dst_end_time_in_utc);
204 unix_time < previous_year_dst_end_unix_time
205 } else {
206 true
207 }
208 } else if unix_time < current_year_dst_start_unix_time {
209 false
210 } else {
211 let next_year_dst_end_unix_time =
212 self.dst_end.unix_time(current_year + 1, dst_end_time_in_utc);
213 if next_year_dst_end_unix_time <= unix_time {
214 let next_year_dst_start_unix_time =
215 self.dst_start.unix_time(current_year + 1, dst_start_time_in_utc);
216 next_year_dst_start_unix_time <= unix_time
217 } else {
218 true
219 }
220 }
221 }
222 };
223
224 if is_dst {
225 Ok(&self.dst)
226 } else {
227 Ok(&self.std)
228 }
229 }
230
231 fn find_local_time_type_from_local(
232 &self,
233 local_time: i64,
234 current_year: i32,
235 ) -> Result<crate::LocalResult<LocalTimeType>, Error> {
236 // Check if the current year is valid for the following computations
237 if !(i32::min_value() + 2 <= current_year && current_year <= i32::max_value() - 2) {
238 return Err(Error::OutOfRange("out of range date time"));
239 }
240
241 let dst_start_transition_start =
242 self.dst_start.unix_time(current_year, 0) + i64::from(self.dst_start_time);
243 let dst_start_transition_end = self.dst_start.unix_time(current_year, 0)
244 + i64::from(self.dst_start_time)
245 + i64::from(self.dst.ut_offset)
246 - i64::from(self.std.ut_offset);
247
248 let dst_end_transition_start =
249 self.dst_end.unix_time(current_year, 0) + i64::from(self.dst_end_time);
250 let dst_end_transition_end = self.dst_end.unix_time(current_year, 0)
251 + i64::from(self.dst_end_time)
252 + i64::from(self.std.ut_offset)
253 - i64::from(self.dst.ut_offset);
254
255 match self.std.ut_offset.cmp(&self.dst.ut_offset) {
256 Ordering::Equal => Ok(crate::LocalResult::Single(self.std)),
257 Ordering::Less => {
258 if self.dst_start.transition_date(current_year).0
259 < self.dst_end.transition_date(current_year).0
260 {
261 // northern hemisphere
262 // For the DST END transition, the `start` happens at a later timestamp than the `end`.
263 if local_time <= dst_start_transition_start {
264 Ok(crate::LocalResult::Single(self.std))
265 } else if local_time > dst_start_transition_start
266 && local_time < dst_start_transition_end
267 {
268 Ok(crate::LocalResult::None)
269 } else if local_time >= dst_start_transition_end
270 && local_time < dst_end_transition_end
271 {
272 Ok(crate::LocalResult::Single(self.dst))
273 } else if local_time >= dst_end_transition_end
274 && local_time <= dst_end_transition_start
275 {
276 Ok(crate::LocalResult::Ambiguous(self.std, self.dst))
277 } else {
278 Ok(crate::LocalResult::Single(self.std))
279 }
280 } else {
281 // southern hemisphere regular DST
282 // For the DST END transition, the `start` happens at a later timestamp than the `end`.
283 if local_time < dst_end_transition_end {
284 Ok(crate::LocalResult::Single(self.dst))
285 } else if local_time >= dst_end_transition_end
286 && local_time <= dst_end_transition_start
287 {
288 Ok(crate::LocalResult::Ambiguous(self.std, self.dst))
289 } else if local_time > dst_end_transition_end
290 && local_time < dst_start_transition_start
291 {
292 Ok(crate::LocalResult::Single(self.std))
293 } else if local_time >= dst_start_transition_start
294 && local_time < dst_start_transition_end
295 {
296 Ok(crate::LocalResult::None)
297 } else {
298 Ok(crate::LocalResult::Single(self.dst))
299 }
300 }
301 }
302 Ordering::Greater => {
303 if self.dst_start.transition_date(current_year).0
304 < self.dst_end.transition_date(current_year).0
305 {
306 // southern hemisphere reverse DST
307 // For the DST END transition, the `start` happens at a later timestamp than the `end`.
308 if local_time < dst_start_transition_end {
309 Ok(crate::LocalResult::Single(self.std))
310 } else if local_time >= dst_start_transition_end
311 && local_time <= dst_start_transition_start
312 {
313 Ok(crate::LocalResult::Ambiguous(self.dst, self.std))
314 } else if local_time > dst_start_transition_start
315 && local_time < dst_end_transition_start
316 {
317 Ok(crate::LocalResult::Single(self.dst))
318 } else if local_time >= dst_end_transition_start
319 && local_time < dst_end_transition_end
320 {
321 Ok(crate::LocalResult::None)
322 } else {
323 Ok(crate::LocalResult::Single(self.std))
324 }
325 } else {
326 // northern hemisphere reverse DST
327 // For the DST END transition, the `start` happens at a later timestamp than the `end`.
328 if local_time <= dst_end_transition_start {
329 Ok(crate::LocalResult::Single(self.dst))
330 } else if local_time > dst_end_transition_start
331 && local_time < dst_end_transition_end
332 {
333 Ok(crate::LocalResult::None)
334 } else if local_time >= dst_end_transition_end
335 && local_time < dst_start_transition_end
336 {
337 Ok(crate::LocalResult::Single(self.std))
338 } else if local_time >= dst_start_transition_end
339 && local_time <= dst_start_transition_start
340 {
341 Ok(crate::LocalResult::Ambiguous(self.dst, self.std))
342 } else {
343 Ok(crate::LocalResult::Single(self.dst))
344 }
345 }
346 }
347 }
348 }
349}
350
351/// Parse time zone name
352fn parse_name<'a>(cursor: &mut Cursor<'a>) -> Result<&'a [u8], Error> {
353 match cursor.peek() {
354 Some(b'<') => {}
355 _ => return Ok(cursor.read_while(u8::is_ascii_alphabetic)?),
356 }
357
358 cursor.read_exact(count:1)?;
359 let unquoted: &[u8] = cursor.read_until(|&x: u8| x == b'>')?;
360 cursor.read_exact(count:1)?;
361 Ok(unquoted)
362}
363
364/// Parse time zone offset
365fn parse_offset(cursor: &mut Cursor) -> Result<i32, Error> {
366 let (sign: i32, hour: i32, minute: i32, second: i32) = parse_signed_hhmmss(cursor)?;
367
368 if !(0..=24).contains(&hour) {
369 return Err(Error::InvalidTzString("invalid offset hour"));
370 }
371 if !(0..=59).contains(&minute) {
372 return Err(Error::InvalidTzString("invalid offset minute"));
373 }
374 if !(0..=59).contains(&second) {
375 return Err(Error::InvalidTzString("invalid offset second"));
376 }
377
378 Ok(sign * (hour * 3600 + minute * 60 + second))
379}
380
381/// Parse transition rule time
382fn parse_rule_time(cursor: &mut Cursor) -> Result<i32, Error> {
383 let (hour: i32, minute: i32, second: i32) = parse_hhmmss(cursor)?;
384
385 if !(0..=24).contains(&hour) {
386 return Err(Error::InvalidTzString("invalid day time hour"));
387 }
388 if !(0..=59).contains(&minute) {
389 return Err(Error::InvalidTzString("invalid day time minute"));
390 }
391 if !(0..=59).contains(&second) {
392 return Err(Error::InvalidTzString("invalid day time second"));
393 }
394
395 Ok(hour * 3600 + minute * 60 + second)
396}
397
398/// Parse transition rule time with TZ string extensions
399fn parse_rule_time_extended(cursor: &mut Cursor) -> Result<i32, Error> {
400 let (sign: i32, hour: i32, minute: i32, second: i32) = parse_signed_hhmmss(cursor)?;
401
402 if !(-167..=167).contains(&hour) {
403 return Err(Error::InvalidTzString("invalid day time hour"));
404 }
405 if !(0..=59).contains(&minute) {
406 return Err(Error::InvalidTzString("invalid day time minute"));
407 }
408 if !(0..=59).contains(&second) {
409 return Err(Error::InvalidTzString("invalid day time second"));
410 }
411
412 Ok(sign * (hour * 3600 + minute * 60 + second))
413}
414
415/// Parse hours, minutes and seconds
416fn parse_hhmmss(cursor: &mut Cursor) -> Result<(i32, i32, i32), Error> {
417 let hour: i32 = cursor.read_int()?;
418
419 let mut minute: i32 = 0;
420 let mut second: i32 = 0;
421
422 if cursor.read_optional_tag(b":")? {
423 minute = cursor.read_int()?;
424
425 if cursor.read_optional_tag(b":")? {
426 second = cursor.read_int()?;
427 }
428 }
429
430 Ok((hour, minute, second))
431}
432
433/// Parse signed hours, minutes and seconds
434fn parse_signed_hhmmss(cursor: &mut Cursor) -> Result<(i32, i32, i32, i32), Error> {
435 let mut sign: i32 = 1;
436 if let Some(&c: u8) = cursor.peek() {
437 if c == b'+' || c == b'-' {
438 cursor.read_exact(count:1)?;
439 if c == b'-' {
440 sign = -1;
441 }
442 }
443 }
444
445 let (hour: i32, minute: i32, second: i32) = parse_hhmmss(cursor)?;
446 Ok((sign, hour, minute, second))
447}
448
449/// Transition rule day
450#[derive(Debug, Copy, Clone, Eq, PartialEq)]
451enum RuleDay {
452 /// Julian day in `[1, 365]`, without taking occasional Feb 29 into account, which is not referenceable
453 Julian1WithoutLeap(u16),
454 /// Zero-based Julian day in `[0, 365]`, taking occasional Feb 29 into account
455 Julian0WithLeap(u16),
456 /// Day represented by a month, a month week and a week day
457 MonthWeekday {
458 /// Month in `[1, 12]`
459 month: u8,
460 /// Week of the month in `[1, 5]`, with `5` representing the last week of the month
461 week: u8,
462 /// Day of the week in `[0, 6]` from Sunday
463 week_day: u8,
464 },
465}
466
467impl RuleDay {
468 /// Parse transition rule
469 fn parse(cursor: &mut Cursor, use_string_extensions: bool) -> Result<(Self, i32), Error> {
470 let date = match cursor.peek() {
471 Some(b'M') => {
472 cursor.read_exact(1)?;
473 let month = cursor.read_int()?;
474 cursor.read_tag(b".")?;
475 let week = cursor.read_int()?;
476 cursor.read_tag(b".")?;
477 let week_day = cursor.read_int()?;
478 RuleDay::month_weekday(month, week, week_day)?
479 }
480 Some(b'J') => {
481 cursor.read_exact(1)?;
482 RuleDay::julian_1(cursor.read_int()?)?
483 }
484 _ => RuleDay::julian_0(cursor.read_int()?)?,
485 };
486
487 Ok((
488 date,
489 match (cursor.read_optional_tag(b"/")?, use_string_extensions) {
490 (false, _) => 2 * 3600,
491 (true, true) => parse_rule_time_extended(cursor)?,
492 (true, false) => parse_rule_time(cursor)?,
493 },
494 ))
495 }
496
497 /// Construct a transition rule day represented by a Julian day in `[1, 365]`, without taking occasional Feb 29 into account, which is not referenceable
498 fn julian_1(julian_day_1: u16) -> Result<Self, Error> {
499 if !(1..=365).contains(&julian_day_1) {
500 return Err(Error::TransitionRule("invalid rule day julian day"));
501 }
502
503 Ok(RuleDay::Julian1WithoutLeap(julian_day_1))
504 }
505
506 /// Construct a transition rule day represented by a zero-based Julian day in `[0, 365]`, taking occasional Feb 29 into account
507 const fn julian_0(julian_day_0: u16) -> Result<Self, Error> {
508 if julian_day_0 > 365 {
509 return Err(Error::TransitionRule("invalid rule day julian day"));
510 }
511
512 Ok(RuleDay::Julian0WithLeap(julian_day_0))
513 }
514
515 /// Construct a transition rule day represented by a month, a month week and a week day
516 fn month_weekday(month: u8, week: u8, week_day: u8) -> Result<Self, Error> {
517 if !(1..=12).contains(&month) {
518 return Err(Error::TransitionRule("invalid rule day month"));
519 }
520
521 if !(1..=5).contains(&week) {
522 return Err(Error::TransitionRule("invalid rule day week"));
523 }
524
525 if week_day > 6 {
526 return Err(Error::TransitionRule("invalid rule day week day"));
527 }
528
529 Ok(RuleDay::MonthWeekday { month, week, week_day })
530 }
531
532 /// Get the transition date for the provided year
533 ///
534 /// ## Outputs
535 ///
536 /// * `month`: Month in `[1, 12]`
537 /// * `month_day`: Day of the month in `[1, 31]`
538 fn transition_date(&self, year: i32) -> (usize, i64) {
539 match *self {
540 RuleDay::Julian1WithoutLeap(year_day) => {
541 let year_day = year_day as i64;
542
543 let month = match CUMUL_DAY_IN_MONTHS_NORMAL_YEAR.binary_search(&(year_day - 1)) {
544 Ok(x) => x + 1,
545 Err(x) => x,
546 };
547
548 let month_day = year_day - CUMUL_DAY_IN_MONTHS_NORMAL_YEAR[month - 1];
549
550 (month, month_day)
551 }
552 RuleDay::Julian0WithLeap(year_day) => {
553 let leap = is_leap_year(year) as i64;
554
555 let cumul_day_in_months = [
556 0,
557 31,
558 59 + leap,
559 90 + leap,
560 120 + leap,
561 151 + leap,
562 181 + leap,
563 212 + leap,
564 243 + leap,
565 273 + leap,
566 304 + leap,
567 334 + leap,
568 ];
569
570 let year_day = year_day as i64;
571
572 let month = match cumul_day_in_months.binary_search(&year_day) {
573 Ok(x) => x + 1,
574 Err(x) => x,
575 };
576
577 let month_day = 1 + year_day - cumul_day_in_months[month - 1];
578
579 (month, month_day)
580 }
581 RuleDay::MonthWeekday { month: rule_month, week, week_day } => {
582 let leap = is_leap_year(year) as i64;
583
584 let month = rule_month as usize;
585
586 let mut day_in_month = DAY_IN_MONTHS_NORMAL_YEAR[month - 1];
587 if month == 2 {
588 day_in_month += leap;
589 }
590
591 let week_day_of_first_month_day =
592 (4 + days_since_unix_epoch(year, month, 1)).rem_euclid(DAYS_PER_WEEK);
593 let first_week_day_occurence_in_month =
594 1 + (week_day as i64 - week_day_of_first_month_day).rem_euclid(DAYS_PER_WEEK);
595
596 let mut month_day =
597 first_week_day_occurence_in_month + (week as i64 - 1) * DAYS_PER_WEEK;
598 if month_day > day_in_month {
599 month_day -= DAYS_PER_WEEK
600 }
601
602 (month, month_day)
603 }
604 }
605 }
606
607 /// Returns the UTC Unix time in seconds associated to the transition date for the provided year
608 fn unix_time(&self, year: i32, day_time_in_utc: i64) -> i64 {
609 let (month, month_day) = self.transition_date(year);
610 days_since_unix_epoch(year, month, month_day) * SECONDS_PER_DAY + day_time_in_utc
611 }
612}
613
614/// UTC date time exprimed in the [proleptic gregorian calendar](https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar)
615#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
616pub(crate) struct UtcDateTime {
617 /// Year
618 pub(crate) year: i32,
619 /// Month in `[1, 12]`
620 pub(crate) month: u8,
621 /// Day of the month in `[1, 31]`
622 pub(crate) month_day: u8,
623 /// Hours since midnight in `[0, 23]`
624 pub(crate) hour: u8,
625 /// Minutes in `[0, 59]`
626 pub(crate) minute: u8,
627 /// Seconds in `[0, 60]`, with a possible leap second
628 pub(crate) second: u8,
629}
630
631impl UtcDateTime {
632 /// Construct a UTC date time from a Unix time in seconds and nanoseconds
633 pub(crate) fn from_timespec(unix_time: i64) -> Result<Self, Error> {
634 let seconds = match unix_time.checked_sub(UNIX_OFFSET_SECS) {
635 Some(seconds) => seconds,
636 None => return Err(Error::OutOfRange("out of range operation")),
637 };
638
639 let mut remaining_days = seconds / SECONDS_PER_DAY;
640 let mut remaining_seconds = seconds % SECONDS_PER_DAY;
641 if remaining_seconds < 0 {
642 remaining_seconds += SECONDS_PER_DAY;
643 remaining_days -= 1;
644 }
645
646 let mut cycles_400_years = remaining_days / DAYS_PER_400_YEARS;
647 remaining_days %= DAYS_PER_400_YEARS;
648 if remaining_days < 0 {
649 remaining_days += DAYS_PER_400_YEARS;
650 cycles_400_years -= 1;
651 }
652
653 let cycles_100_years = Ord::min(remaining_days / DAYS_PER_100_YEARS, 3);
654 remaining_days -= cycles_100_years * DAYS_PER_100_YEARS;
655
656 let cycles_4_years = Ord::min(remaining_days / DAYS_PER_4_YEARS, 24);
657 remaining_days -= cycles_4_years * DAYS_PER_4_YEARS;
658
659 let remaining_years = Ord::min(remaining_days / DAYS_PER_NORMAL_YEAR, 3);
660 remaining_days -= remaining_years * DAYS_PER_NORMAL_YEAR;
661
662 let mut year = OFFSET_YEAR
663 + remaining_years
664 + cycles_4_years * 4
665 + cycles_100_years * 100
666 + cycles_400_years * 400;
667
668 let mut month = 0;
669 while month < DAY_IN_MONTHS_LEAP_YEAR_FROM_MARCH.len() {
670 let days = DAY_IN_MONTHS_LEAP_YEAR_FROM_MARCH[month];
671 if remaining_days < days {
672 break;
673 }
674 remaining_days -= days;
675 month += 1;
676 }
677 month += 2;
678
679 if month >= MONTHS_PER_YEAR as usize {
680 month -= MONTHS_PER_YEAR as usize;
681 year += 1;
682 }
683 month += 1;
684
685 let month_day = 1 + remaining_days;
686
687 let hour = remaining_seconds / SECONDS_PER_HOUR;
688 let minute = (remaining_seconds / SECONDS_PER_MINUTE) % MINUTES_PER_HOUR;
689 let second = remaining_seconds % SECONDS_PER_MINUTE;
690
691 let year = match year >= i32::min_value() as i64 && year <= i32::max_value() as i64 {
692 true => year as i32,
693 false => return Err(Error::OutOfRange("i64 is out of range for i32")),
694 };
695
696 Ok(Self {
697 year,
698 month: month as u8,
699 month_day: month_day as u8,
700 hour: hour as u8,
701 minute: minute as u8,
702 second: second as u8,
703 })
704 }
705}
706
707/// Number of nanoseconds in one second
708const NANOSECONDS_PER_SECOND: u32 = 1_000_000_000;
709/// Number of seconds in one minute
710const SECONDS_PER_MINUTE: i64 = 60;
711/// Number of seconds in one hour
712const SECONDS_PER_HOUR: i64 = 3600;
713/// Number of minutes in one hour
714const MINUTES_PER_HOUR: i64 = 60;
715/// Number of months in one year
716const MONTHS_PER_YEAR: i64 = 12;
717/// Number of days in a normal year
718const DAYS_PER_NORMAL_YEAR: i64 = 365;
719/// Number of days in 4 years (including 1 leap year)
720const DAYS_PER_4_YEARS: i64 = DAYS_PER_NORMAL_YEAR * 4 + 1;
721/// Number of days in 100 years (including 24 leap years)
722const DAYS_PER_100_YEARS: i64 = DAYS_PER_NORMAL_YEAR * 100 + 24;
723/// Number of days in 400 years (including 97 leap years)
724const DAYS_PER_400_YEARS: i64 = DAYS_PER_NORMAL_YEAR * 400 + 97;
725/// Unix time at `2000-03-01T00:00:00Z` (Wednesday)
726const UNIX_OFFSET_SECS: i64 = 951868800;
727/// Offset year
728const OFFSET_YEAR: i64 = 2000;
729/// Month days in a leap year from March
730const DAY_IN_MONTHS_LEAP_YEAR_FROM_MARCH: [i64; 12] =
731 [31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 29];
732
733/// Compute the number of days since Unix epoch (`1970-01-01T00:00:00Z`).
734///
735/// ## Inputs
736///
737/// * `year`: Year
738/// * `month`: Month in `[1, 12]`
739/// * `month_day`: Day of the month in `[1, 31]`
740pub(crate) const fn days_since_unix_epoch(year: i32, month: usize, month_day: i64) -> i64 {
741 let is_leap_year = is_leap_year(year);
742
743 let year = year as i64;
744
745 let mut result = (year - 1970) * 365;
746
747 if year >= 1970 {
748 result += (year - 1968) / 4;
749 result -= (year - 1900) / 100;
750 result += (year - 1600) / 400;
751
752 if is_leap_year && month < 3 {
753 result -= 1;
754 }
755 } else {
756 result += (year - 1972) / 4;
757 result -= (year - 2000) / 100;
758 result += (year - 2000) / 400;
759
760 if is_leap_year && month >= 3 {
761 result += 1;
762 }
763 }
764
765 result += CUMUL_DAY_IN_MONTHS_NORMAL_YEAR[month - 1] + month_day - 1;
766
767 result
768}
769
770/// Check if a year is a leap year
771pub(crate) const fn is_leap_year(year: i32) -> bool {
772 year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)
773}
774
775#[cfg(test)]
776mod tests {
777 use super::super::timezone::Transition;
778 use super::super::{Error, TimeZone};
779 use super::{AlternateTime, LocalTimeType, RuleDay, TransitionRule};
780
781 #[test]
782 fn test_quoted() -> Result<(), Error> {
783 let transition_rule = TransitionRule::from_tz_string(b"<-03>+3<+03>-3,J1,J365", false)?;
784 assert_eq!(
785 transition_rule,
786 AlternateTime::new(
787 LocalTimeType::new(-10800, false, Some(b"-03"))?,
788 LocalTimeType::new(10800, true, Some(b"+03"))?,
789 RuleDay::julian_1(1)?,
790 7200,
791 RuleDay::julian_1(365)?,
792 7200,
793 )?
794 .into()
795 );
796 Ok(())
797 }
798
799 #[test]
800 fn test_full() -> Result<(), Error> {
801 let tz_string = b"NZST-12:00:00NZDT-13:00:00,M10.1.0/02:00:00,M3.3.0/02:00:00";
802 let transition_rule = TransitionRule::from_tz_string(tz_string, false)?;
803 assert_eq!(
804 transition_rule,
805 AlternateTime::new(
806 LocalTimeType::new(43200, false, Some(b"NZST"))?,
807 LocalTimeType::new(46800, true, Some(b"NZDT"))?,
808 RuleDay::month_weekday(10, 1, 0)?,
809 7200,
810 RuleDay::month_weekday(3, 3, 0)?,
811 7200,
812 )?
813 .into()
814 );
815 Ok(())
816 }
817
818 #[test]
819 fn test_negative_dst() -> Result<(), Error> {
820 let tz_string = b"IST-1GMT0,M10.5.0,M3.5.0/1";
821 let transition_rule = TransitionRule::from_tz_string(tz_string, false)?;
822 assert_eq!(
823 transition_rule,
824 AlternateTime::new(
825 LocalTimeType::new(3600, false, Some(b"IST"))?,
826 LocalTimeType::new(0, true, Some(b"GMT"))?,
827 RuleDay::month_weekday(10, 5, 0)?,
828 7200,
829 RuleDay::month_weekday(3, 5, 0)?,
830 3600,
831 )?
832 .into()
833 );
834 Ok(())
835 }
836
837 #[test]
838 fn test_negative_hour() -> Result<(), Error> {
839 let tz_string = b"<-03>3<-02>,M3.5.0/-2,M10.5.0/-1";
840 assert!(TransitionRule::from_tz_string(tz_string, false).is_err());
841
842 assert_eq!(
843 TransitionRule::from_tz_string(tz_string, true)?,
844 AlternateTime::new(
845 LocalTimeType::new(-10800, false, Some(b"-03"))?,
846 LocalTimeType::new(-7200, true, Some(b"-02"))?,
847 RuleDay::month_weekday(3, 5, 0)?,
848 -7200,
849 RuleDay::month_weekday(10, 5, 0)?,
850 -3600,
851 )?
852 .into()
853 );
854 Ok(())
855 }
856
857 #[test]
858 fn test_all_year_dst() -> Result<(), Error> {
859 let tz_string = b"EST5EDT,0/0,J365/25";
860 assert!(TransitionRule::from_tz_string(tz_string, false).is_err());
861
862 assert_eq!(
863 TransitionRule::from_tz_string(tz_string, true)?,
864 AlternateTime::new(
865 LocalTimeType::new(-18000, false, Some(b"EST"))?,
866 LocalTimeType::new(-14400, true, Some(b"EDT"))?,
867 RuleDay::julian_0(0)?,
868 0,
869 RuleDay::julian_1(365)?,
870 90000,
871 )?
872 .into()
873 );
874 Ok(())
875 }
876
877 #[test]
878 fn test_v3_file() -> Result<(), Error> {
879 let bytes = b"TZif3\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x01\0\0\0\x04\0\0\x1c\x20\0\0IST\0TZif3\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x01\0\0\0\x01\0\0\0\0\0\0\0\x01\0\0\0\x01\0\0\0\x04\0\0\0\0\x7f\xe8\x17\x80\0\0\0\x1c\x20\0\0IST\0\x01\x01\x0aIST-2IDT,M3.4.4/26,M10.5.0\x0a";
880
881 let time_zone = TimeZone::from_tz_data(bytes)?;
882
883 let time_zone_result = TimeZone::new(
884 vec![Transition::new(2145916800, 0)],
885 vec![LocalTimeType::new(7200, false, Some(b"IST"))?],
886 Vec::new(),
887 Some(TransitionRule::from(AlternateTime::new(
888 LocalTimeType::new(7200, false, Some(b"IST"))?,
889 LocalTimeType::new(10800, true, Some(b"IDT"))?,
890 RuleDay::month_weekday(3, 4, 4)?,
891 93600,
892 RuleDay::month_weekday(10, 5, 0)?,
893 7200,
894 )?)),
895 )?;
896
897 assert_eq!(time_zone, time_zone_result);
898
899 Ok(())
900 }
901
902 #[test]
903 fn test_rule_day() -> Result<(), Error> {
904 let rule_day_j1 = RuleDay::julian_1(60)?;
905 assert_eq!(rule_day_j1.transition_date(2000), (3, 1));
906 assert_eq!(rule_day_j1.transition_date(2001), (3, 1));
907 assert_eq!(rule_day_j1.unix_time(2000, 43200), 951912000);
908
909 let rule_day_j0 = RuleDay::julian_0(59)?;
910 assert_eq!(rule_day_j0.transition_date(2000), (2, 29));
911 assert_eq!(rule_day_j0.transition_date(2001), (3, 1));
912 assert_eq!(rule_day_j0.unix_time(2000, 43200), 951825600);
913
914 let rule_day_mwd = RuleDay::month_weekday(2, 5, 2)?;
915 assert_eq!(rule_day_mwd.transition_date(2000), (2, 29));
916 assert_eq!(rule_day_mwd.transition_date(2001), (2, 27));
917 assert_eq!(rule_day_mwd.unix_time(2000, 43200), 951825600);
918 assert_eq!(rule_day_mwd.unix_time(2001, 43200), 983275200);
919
920 Ok(())
921 }
922
923 #[test]
924 fn test_transition_rule() -> Result<(), Error> {
925 let transition_rule_fixed = TransitionRule::from(LocalTimeType::new(-36000, false, None)?);
926 assert_eq!(transition_rule_fixed.find_local_time_type(0)?.offset(), -36000);
927
928 let transition_rule_dst = TransitionRule::from(AlternateTime::new(
929 LocalTimeType::new(43200, false, Some(b"NZST"))?,
930 LocalTimeType::new(46800, true, Some(b"NZDT"))?,
931 RuleDay::month_weekday(10, 1, 0)?,
932 7200,
933 RuleDay::month_weekday(3, 3, 0)?,
934 7200,
935 )?);
936
937 assert_eq!(transition_rule_dst.find_local_time_type(953384399)?.offset(), 46800);
938 assert_eq!(transition_rule_dst.find_local_time_type(953384400)?.offset(), 43200);
939 assert_eq!(transition_rule_dst.find_local_time_type(970322399)?.offset(), 43200);
940 assert_eq!(transition_rule_dst.find_local_time_type(970322400)?.offset(), 46800);
941
942 let transition_rule_negative_dst = TransitionRule::from(AlternateTime::new(
943 LocalTimeType::new(3600, false, Some(b"IST"))?,
944 LocalTimeType::new(0, true, Some(b"GMT"))?,
945 RuleDay::month_weekday(10, 5, 0)?,
946 7200,
947 RuleDay::month_weekday(3, 5, 0)?,
948 3600,
949 )?);
950
951 assert_eq!(transition_rule_negative_dst.find_local_time_type(954032399)?.offset(), 0);
952 assert_eq!(transition_rule_negative_dst.find_local_time_type(954032400)?.offset(), 3600);
953 assert_eq!(transition_rule_negative_dst.find_local_time_type(972781199)?.offset(), 3600);
954 assert_eq!(transition_rule_negative_dst.find_local_time_type(972781200)?.offset(), 0);
955
956 let transition_rule_negative_time_1 = TransitionRule::from(AlternateTime::new(
957 LocalTimeType::new(0, false, None)?,
958 LocalTimeType::new(0, true, None)?,
959 RuleDay::julian_0(100)?,
960 0,
961 RuleDay::julian_0(101)?,
962 -86500,
963 )?);
964
965 assert!(transition_rule_negative_time_1.find_local_time_type(8639899)?.is_dst());
966 assert!(!transition_rule_negative_time_1.find_local_time_type(8639900)?.is_dst());
967 assert!(!transition_rule_negative_time_1.find_local_time_type(8639999)?.is_dst());
968 assert!(transition_rule_negative_time_1.find_local_time_type(8640000)?.is_dst());
969
970 let transition_rule_negative_time_2 = TransitionRule::from(AlternateTime::new(
971 LocalTimeType::new(-10800, false, Some(b"-03"))?,
972 LocalTimeType::new(-7200, true, Some(b"-02"))?,
973 RuleDay::month_weekday(3, 5, 0)?,
974 -7200,
975 RuleDay::month_weekday(10, 5, 0)?,
976 -3600,
977 )?);
978
979 assert_eq!(
980 transition_rule_negative_time_2.find_local_time_type(954032399)?.offset(),
981 -10800
982 );
983 assert_eq!(
984 transition_rule_negative_time_2.find_local_time_type(954032400)?.offset(),
985 -7200
986 );
987 assert_eq!(
988 transition_rule_negative_time_2.find_local_time_type(972781199)?.offset(),
989 -7200
990 );
991 assert_eq!(
992 transition_rule_negative_time_2.find_local_time_type(972781200)?.offset(),
993 -10800
994 );
995
996 let transition_rule_all_year_dst = TransitionRule::from(AlternateTime::new(
997 LocalTimeType::new(-18000, false, Some(b"EST"))?,
998 LocalTimeType::new(-14400, true, Some(b"EDT"))?,
999 RuleDay::julian_0(0)?,
1000 0,
1001 RuleDay::julian_1(365)?,
1002 90000,
1003 )?);
1004
1005 assert_eq!(transition_rule_all_year_dst.find_local_time_type(946702799)?.offset(), -14400);
1006 assert_eq!(transition_rule_all_year_dst.find_local_time_type(946702800)?.offset(), -14400);
1007
1008 Ok(())
1009 }
1010
1011 #[test]
1012 fn test_transition_rule_overflow() -> Result<(), Error> {
1013 let transition_rule_1 = TransitionRule::from(AlternateTime::new(
1014 LocalTimeType::new(-1, false, None)?,
1015 LocalTimeType::new(-1, true, None)?,
1016 RuleDay::julian_1(365)?,
1017 0,
1018 RuleDay::julian_1(1)?,
1019 0,
1020 )?);
1021
1022 let transition_rule_2 = TransitionRule::from(AlternateTime::new(
1023 LocalTimeType::new(1, false, None)?,
1024 LocalTimeType::new(1, true, None)?,
1025 RuleDay::julian_1(365)?,
1026 0,
1027 RuleDay::julian_1(1)?,
1028 0,
1029 )?);
1030
1031 let min_unix_time = -67768100567971200;
1032 let max_unix_time = 67767976233532799;
1033
1034 assert!(matches!(
1035 transition_rule_1.find_local_time_type(min_unix_time),
1036 Err(Error::OutOfRange(_))
1037 ));
1038 assert!(matches!(
1039 transition_rule_2.find_local_time_type(max_unix_time),
1040 Err(Error::OutOfRange(_))
1041 ));
1042
1043 Ok(())
1044 }
1045}
1046