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Add additional checks for AlternateTime #789

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Add additional checks for AlternateTime #789

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f4b0e71
Add additional checks for AlternateTime
x-hgg-x Aug 24, 2022
39cbf40
Check all TZ files in the database
x-hgg-x Aug 29, 2022
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14 changes: 12 additions & 2 deletions src/offset/local/tz_info/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ pub(crate) use timezone::TimeZone;

mod parser;
mod rule;
mod rule_check;

/// Unified error type for everything in the crate
#[derive(Debug)]
Expand Down Expand Up @@ -123,9 +124,18 @@ const SECONDS_PER_HOUR: i64 = 3600;
const SECONDS_PER_DAY: i64 = SECONDS_PER_HOUR * HOURS_PER_DAY;
/// Number of days in one week
const DAYS_PER_WEEK: i64 = 7;
/// Number of months in one year
const MONTHS_PER_YEAR: i64 = 12;
/// Number of seconds in a normal year
const SECONDS_PER_NORMAL_YEAR: i64 = 365 * SECONDS_PER_DAY;
/// Number of seconds in a leap year
const SECONDS_PER_LEAP_YEAR: i64 = 366 * SECONDS_PER_DAY;

/// Month days in a normal year
const DAY_IN_MONTHS_NORMAL_YEAR: [i64; 12] = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
const DAYS_IN_MONTHS_NORMAL_YEAR: [i64; 12] = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
/// Cumulated month days in a normal year
const CUMUL_DAY_IN_MONTHS_NORMAL_YEAR: [i64; 12] =
const CUMUL_DAYS_IN_MONTHS_NORMAL_YEAR: [i64; 12] =
[0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
/// Cumulated month days in a leap year
const CUMUL_DAYS_IN_MONTHS_LEAP_YEAR: [i64; 12] =
[0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335];
80 changes: 49 additions & 31 deletions src/offset/local/tz_info/rule.rs
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Original file line number Diff line number Diff line change
@@ -1,10 +1,11 @@
use std::cmp::Ordering;

use super::parser::Cursor;
use super::rule_check::check_dst_transition_rules_consistency;
use super::timezone::{LocalTimeType, SECONDS_PER_WEEK};
use super::{
rem_euclid, Error, CUMUL_DAY_IN_MONTHS_NORMAL_YEAR, DAYS_PER_WEEK, DAY_IN_MONTHS_NORMAL_YEAR,
SECONDS_PER_DAY,
rem_euclid, Error, CUMUL_DAYS_IN_MONTHS_LEAP_YEAR, CUMUL_DAYS_IN_MONTHS_NORMAL_YEAR,
DAYS_IN_MONTHS_NORMAL_YEAR, DAYS_PER_WEEK, SECONDS_PER_DAY,
};

/// Transition rule
Expand Down Expand Up @@ -135,13 +136,39 @@ impl AlternateTime {
dst_end: RuleDay,
dst_end_time: i32,
) -> Result<Self, Error> {
let std_ut_offset = std.ut_offset as i64;
let dst_ut_offset = dst.ut_offset as i64;

// Limit UTC offset to POSIX-required range
if !(-25 * SECONDS_PER_HOUR < std_ut_offset && std_ut_offset < 26 * SECONDS_PER_HOUR) {
return Err(Error::TransitionRule("invalid standard time UTC offset"));
}

if !(-25 * SECONDS_PER_HOUR < dst_ut_offset && dst_ut_offset < 26 * SECONDS_PER_HOUR) {
return Err(Error::TransitionRule("invalid Daylight Saving Time UTC offset"));
}

// Overflow is not possible
if !((dst_start_time as i64).abs() < SECONDS_PER_WEEK
&& (dst_end_time as i64).abs() < SECONDS_PER_WEEK)
{
return Err(Error::TransitionRule("invalid DST start or end time"));
}

// Check DST transition rules consistency
if !check_dst_transition_rules_consistency(
&std,
&dst,
dst_start,
dst_start_time,
dst_end,
dst_end_time,
) {
return Err(Error::TransitionRule(
"DST transition rules are not consistent from one year to another",
));
}

Ok(Self { std, dst, dst_start, dst_start_time, dst_end, dst_end_time })
}

Expand All @@ -166,7 +193,9 @@ impl AlternateTime {
let current_year_dst_end_unix_time =
self.dst_end.unix_time(current_year, dst_end_time_in_utc);

// Check DST start/end Unix times for previous/current/next years to support for transition day times outside of [0h, 24h] range
// Check DST start/end Unix times for previous/current/next years to support for transition day times outside of [0h, 24h] range.
// This is enough since the absolute value of DST start/end time in UTC is less than 2 weeks.
// Moreover, inconsistent DST transition rules are not allowed, so there won't be additional transitions at the year boundary.
let is_dst =
match Ord::cmp(&current_year_dst_start_unix_time, &current_year_dst_end_unix_time) {
Ordering::Less | Ordering::Equal => {
Expand Down Expand Up @@ -448,10 +477,10 @@ fn parse_signed_hhmmss(cursor: &mut Cursor) -> Result<(i32, i32, i32, i32), Erro

/// Transition rule day
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
enum RuleDay {
/// Julian day in `[1, 365]`, without taking occasional Feb 29 into account, which is not referenceable
pub(super) enum RuleDay {
/// Julian day in `[1, 365]`, without taking occasional February 29th into account, which is not referenceable
Julian1WithoutLeap(u16),
/// Zero-based Julian day in `[0, 365]`, taking occasional Feb 29 into account
/// Zero-based Julian day in `[0, 365]`, taking occasional February 29th into account and allowing December 32nd
Julian0WithLeap(u16),
/// Day represented by a month, a month week and a week day
MonthWeekday {
Expand Down Expand Up @@ -494,17 +523,17 @@ impl RuleDay {
))
}

/// Construct a transition rule day represented by a Julian day in `[1, 365]`, without taking occasional Feb 29 into account, which is not referenceable
fn julian_1(julian_day_1: u16) -> Result<Self, Error> {
/// Construct a transition rule day represented by a Julian day in `[1, 365]`, without taking occasional February 29th into account, which is not referenceable
pub(super) fn julian_1(julian_day_1: u16) -> Result<Self, Error> {
if !(1..=365).contains(&julian_day_1) {
return Err(Error::TransitionRule("invalid rule day julian day"));
}

Ok(RuleDay::Julian1WithoutLeap(julian_day_1))
}

/// Construct a transition rule day represented by a zero-based Julian day in `[0, 365]`, taking occasional Feb 29 into account
fn julian_0(julian_day_0: u16) -> Result<Self, Error> {
/// Construct a transition rule day represented by a zero-based Julian day in `[0, 365]`, taking occasional February 29th into account and allowing December 32nd
pub(super) fn julian_0(julian_day_0: u16) -> Result<Self, Error> {
if julian_day_0 > 365 {
return Err(Error::TransitionRule("invalid rule day julian day"));
}
Expand All @@ -513,7 +542,7 @@ impl RuleDay {
}

/// Construct a transition rule day represented by a month, a month week and a week day
fn month_weekday(month: u8, week: u8, week_day: u8) -> Result<Self, Error> {
pub(super) fn month_weekday(month: u8, week: u8, week_day: u8) -> Result<Self, Error> {
if !(1..=12).contains(&month) {
return Err(Error::TransitionRule("invalid rule day month"));
}
Expand All @@ -540,32 +569,21 @@ impl RuleDay {
RuleDay::Julian1WithoutLeap(year_day) => {
let year_day = year_day as i64;

let month = match CUMUL_DAY_IN_MONTHS_NORMAL_YEAR.binary_search(&(year_day - 1)) {
let month = match CUMUL_DAYS_IN_MONTHS_NORMAL_YEAR.binary_search(&(year_day - 1)) {
Ok(x) => x + 1,
Err(x) => x,
};

let month_day = year_day - CUMUL_DAY_IN_MONTHS_NORMAL_YEAR[month - 1];
let month_day = year_day - CUMUL_DAYS_IN_MONTHS_NORMAL_YEAR[month - 1];

(month, month_day)
}
RuleDay::Julian0WithLeap(year_day) => {
let leap = is_leap_year(year) as i64;

let cumul_day_in_months = [
0,
31,
59 + leap,
90 + leap,
120 + leap,
151 + leap,
181 + leap,
212 + leap,
243 + leap,
273 + leap,
304 + leap,
334 + leap,
];
let cumul_day_in_months = if is_leap_year(year) {
CUMUL_DAYS_IN_MONTHS_LEAP_YEAR
} else {
CUMUL_DAYS_IN_MONTHS_NORMAL_YEAR
};

let year_day = year_day as i64;

Expand All @@ -583,7 +601,7 @@ impl RuleDay {

let month = rule_month as usize;

let mut day_in_month = DAY_IN_MONTHS_NORMAL_YEAR[month - 1];
let mut day_in_month = DAYS_IN_MONTHS_NORMAL_YEAR[month - 1];
if month == 2 {
day_in_month += leap;
}
Expand Down Expand Up @@ -762,7 +780,7 @@ pub(crate) fn days_since_unix_epoch(year: i32, month: usize, month_day: i64) ->
}
}

result += CUMUL_DAY_IN_MONTHS_NORMAL_YEAR[month - 1] + month_day - 1;
result += CUMUL_DAYS_IN_MONTHS_NORMAL_YEAR[month - 1] + month_day - 1;

result
}
Expand Down