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