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https://github.com/chronotope/chrono.git
synced 2025-11-04 07:23:49 +00:00
Revise Months API
* Provide `checked_add_months()` and `checked_sub_months()` for callers that would like to avoid panics * Document panic potential in `Add` and `Sub` implementations * Implement additional traits for `Months` per API guidelines * Hide inner type for `Months` and add constructor * Use lower-level APIs to clamp day
This commit is contained in:
Dirkjan Ochtman
parent
ab688c384f
commit
bd3b48d1a9
11
src/month.rs
11
src/month.rs
@ -190,8 +190,15 @@ impl num_traits::FromPrimitive for Month {
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}
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/// A duration in calendar months
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#[derive(Clone, Debug, PartialEq)]
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pub struct Months(pub usize);
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#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, PartialOrd)]
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pub struct Months(pub(crate) u32);
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impl Months {
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/// Construct a new `Months` from a number of months
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pub fn new(num: u32) -> Self {
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Self(num)
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}
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}
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/// An error resulting from reading `<Month>` value with `FromStr`.
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#[derive(Clone, PartialEq)]
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@ -597,31 +597,99 @@ impl NaiveDate {
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parsed.to_naive_date()
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}
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/// Private function to calculate necessary primitives for `Add<Month>`
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/// Add a duration in [`Months`] to the date
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///
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/// # Arguments
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/// If the day would be out of range for the resulting month, use the last day for that month.
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///
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/// * `delta` - Number of months (+/-) to add
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/// Returns `None` if the resulting date would be out of range.
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///
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/// # Returns
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/// ```
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/// # use chrono::{NaiveDate, Months};
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/// assert_eq!(
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/// NaiveDate::from_ymd(2022, 2, 20).checked_add_months(Months::new(6)),
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/// Some(NaiveDate::from_ymd(2022, 8, 20))
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/// );
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/// assert_eq!(
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/// NaiveDate::from_ymd(2022, 7, 31).checked_add_months(Months::new(2)),
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/// Some(NaiveDate::from_ymd(2022, 9, 30))
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/// );
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/// ```
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pub fn checked_add_months(self, months: Months) -> Option<Self> {
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if months.0 == 0 {
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return Some(self);
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}
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match months.0 <= core::i32::MAX as u32 {
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true => self.diff_months(months.0 as i32),
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false => None,
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}
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}
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/// Subtract a duration in [`Months`] from the date
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///
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/// A new NaiveDate on the first day of the resulting year & month
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fn add_months_get_first_day(&self, delta: i32) -> NaiveDate {
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let zeroed_months = self.month() as i32 - 1; // zero-based for modulo operations
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let res_months = zeroed_months + delta;
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let delta_years = if res_months < 0 {
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if (-res_months) % 12 > 0 {
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res_months / 12 - 1
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} else {
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res_months / 12
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}
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/// If the day would be out of range for the resulting month, use the last day for that month.
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///
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/// Returns `None` if the resulting date would be out of range.
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///
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/// ```
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/// # use chrono::{NaiveDate, Months};
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/// assert_eq!(
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/// NaiveDate::from_ymd(2022, 2, 20).checked_sub_months(Months::new(6)),
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/// Some(NaiveDate::from_ymd(2021, 8, 20))
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/// );
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/// ```
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pub fn checked_sub_months(self, months: Months) -> Option<Self> {
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if months.0 == 0 {
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return Some(self);
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}
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// Copy `i32::MIN` here so we don't have to do a complicated cast
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match months.0 <= 2_147_483_648 {
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true => self.diff_months(-(months.0 as i32)),
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false => None,
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}
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}
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fn diff_months(self, months: i32) -> Option<Self> {
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let (years, left) = ((months / 12), (months % 12));
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// Determine new year (without taking months into account for now
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let year = if (years > 0 && years > (MAX_YEAR - self.year()))
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|| (years < 0 && years < (MIN_YEAR - self.year()))
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{
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return None;
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} else {
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res_months / 12
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self.year() + years
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};
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let res_years = self.year() + delta_years;
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let res_months = res_months % 12;
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let res_months = if res_months < 0 { res_months + 12 } else { res_months };
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NaiveDate::from_ymd(res_years, res_months as u32 + 1, 1)
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// Determine new month
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let month = self.month() as i32 + left;
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let (year, month) = if month <= 0 {
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if year == MIN_YEAR {
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return None;
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}
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(year - 1, month + 12)
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} else if month > 12 {
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if year == MAX_YEAR {
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return None;
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}
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(year + 1, month - 12)
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} else {
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(year, month)
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};
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// Clamp original day in case new month is shorter
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let flags = YearFlags::from_year(year);
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let feb_days = if flags.ndays() == 366 { 29 } else { 28 };
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let days = [31, feb_days, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
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let day = Ord::min(self.day(), days[(month - 1) as usize]);
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NaiveDate::from_mdf(year, Mdf::new(month as u32, day, flags))
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}
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/// Makes a new `NaiveDateTime` from the current date and given `NaiveTime`.
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@ -1594,6 +1662,10 @@ impl Add<Months> for NaiveDate {
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/// An addition of months to `NaiveDate` clamped to valid days in resulting month.
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///
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/// # Panics
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///
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/// Panics if the resulting date would be out of range.
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///
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/// # Example
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///
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/// ```
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@ -1601,19 +1673,15 @@ impl Add<Months> for NaiveDate {
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///
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/// let from_ymd = NaiveDate::from_ymd;
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///
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/// assert_eq!(from_ymd(2014, 1, 1) + Months(1), from_ymd(2014, 2, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) + Months(11), from_ymd(2014, 12, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) + Months(12), from_ymd(2015, 1, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) + Months(13), from_ymd(2015, 2, 1));
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/// assert_eq!(from_ymd(2014, 1, 31) + Months(1), from_ymd(2014, 2, 28));
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/// assert_eq!(from_ymd(2020, 1, 31) + Months(1), from_ymd(2020, 2, 29));
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/// assert_eq!(from_ymd(2014, 1, 1) + Months::new(1), from_ymd(2014, 2, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) + Months::new(11), from_ymd(2014, 12, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) + Months::new(12), from_ymd(2015, 1, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) + Months::new(13), from_ymd(2015, 2, 1));
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/// assert_eq!(from_ymd(2014, 1, 31) + Months::new(1), from_ymd(2014, 2, 28));
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/// assert_eq!(from_ymd(2020, 1, 31) + Months::new(1), from_ymd(2020, 2, 29));
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/// ```
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fn add(self, months: Months) -> Self::Output {
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let target = self.add_months_get_first_day(months.0 as i32);
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let target_plus = target.add_months_get_first_day(1);
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let last_day = target_plus.sub(Duration::days(1));
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let day = core::cmp::min(self.day(), last_day.day());
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NaiveDate::from_ymd(target.year(), target.month(), day)
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self.checked_add_months(months).unwrap()
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}
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}
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@ -1622,6 +1690,10 @@ impl Sub<Months> for NaiveDate {
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/// A subtraction of Months from `NaiveDate` clamped to valid days in resulting month.
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///
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/// # Panics
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///
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/// Panics if the resulting date would be out of range.
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///
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/// # Example
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///
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/// ```
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@ -1629,16 +1701,12 @@ impl Sub<Months> for NaiveDate {
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///
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/// let from_ymd = NaiveDate::from_ymd;
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///
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/// assert_eq!(from_ymd(2014, 1, 1) - Months(11), from_ymd(2013, 2, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) - Months(12), from_ymd(2013, 1, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) - Months(13), from_ymd(2012, 12, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) - Months::new(11), from_ymd(2013, 2, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) - Months::new(12), from_ymd(2013, 1, 1));
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/// assert_eq!(from_ymd(2014, 1, 1) - Months::new(13), from_ymd(2012, 12, 1));
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/// ```
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fn sub(self, months: Months) -> Self::Output {
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let target = self.add_months_get_first_day(-(months.0 as i32));
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let target_plus = target.add_months_get_first_day(1);
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let last_day = target_plus.sub(Duration::days(1));
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let day = core::cmp::min(self.day(), last_day.day());
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NaiveDate::from_ymd(target.year(), target.month(), day)
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self.checked_sub_months(months).unwrap()
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}
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}
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@ -2077,49 +2145,92 @@ mod serde {
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#[cfg(test)]
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mod tests {
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use super::NaiveDate;
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use super::{MAX_DAYS_FROM_YEAR_0, MAX_YEAR, MIN_DAYS_FROM_YEAR_0, MIN_YEAR};
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use super::{
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Months, NaiveDate, MAX_DAYS_FROM_YEAR_0, MAX_YEAR, MIN_DAYS_FROM_YEAR_0, MIN_YEAR,
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};
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use crate::oldtime::Duration;
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use crate::{Datelike, Weekday};
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use std::{i32, u32};
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#[test]
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fn test_add_months_get_first_day() {
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fn diff_months() {
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// identity
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assert_eq!(
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NaiveDate::from_ymd(2014, 1, 1).add_months_get_first_day(1),
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NaiveDate::from_ymd(2014, 2, 1)
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NaiveDate::from_ymd(2022, 8, 3).checked_add_months(Months::new(0)),
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Some(NaiveDate::from_ymd(2022, 8, 3))
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);
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// add with months exceeding `i32::MAX`
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assert_eq!(
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NaiveDate::from_ymd(2014, 1, 31).add_months_get_first_day(1),
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NaiveDate::from_ymd(2014, 2, 1)
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NaiveDate::from_ymd(2022, 8, 3).checked_add_months(Months::new(i32::MAX as u32 + 1)),
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None
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);
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// sub with months exceeindg `i32::MIN`
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assert_eq!(
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NaiveDate::from_ymd(2020, 1, 10).add_months_get_first_day(1),
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NaiveDate::from_ymd(2020, 2, 1)
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NaiveDate::from_ymd(2022, 8, 3)
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.checked_sub_months(Months::new((i32::MIN as i64).abs() as u32 + 1)),
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None
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);
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// add overflowing year
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assert_eq!(NaiveDate::MAX.checked_add_months(Months::new(1)), None);
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// add underflowing year
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assert_eq!(NaiveDate::MIN.checked_sub_months(Months::new(1)), None);
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// sub crossing year 0 boundary
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assert_eq!(
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NaiveDate::from_ymd(2014, 1, 1).add_months_get_first_day(-1),
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NaiveDate::from_ymd(2013, 12, 1)
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NaiveDate::from_ymd(2022, 8, 3).checked_sub_months(Months::new(2050 * 12)),
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Some(NaiveDate::from_ymd(-28, 8, 3))
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);
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// add crossing year boundary
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assert_eq!(
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NaiveDate::from_ymd(2014, 1, 31).add_months_get_first_day(-1),
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NaiveDate::from_ymd(2013, 12, 1)
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NaiveDate::from_ymd(2022, 8, 3).checked_add_months(Months::new(6)),
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Some(NaiveDate::from_ymd(2023, 2, 3))
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);
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// sub crossing year boundary
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assert_eq!(
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NaiveDate::from_ymd(2020, 1, 10).add_months_get_first_day(-1),
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NaiveDate::from_ymd(2019, 12, 1)
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NaiveDate::from_ymd(2022, 8, 3).checked_sub_months(Months::new(10)),
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Some(NaiveDate::from_ymd(2021, 10, 3))
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);
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// add clamping day, non-leap year
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assert_eq!(
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NaiveDate::from_ymd(2014, 1, 10).add_months_get_first_day(-11),
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NaiveDate::from_ymd(2013, 2, 1)
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NaiveDate::from_ymd(2022, 1, 29).checked_add_months(Months::new(1)),
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Some(NaiveDate::from_ymd(2022, 2, 28))
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);
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// add to leap day
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assert_eq!(
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NaiveDate::from_ymd(2014, 1, 10).add_months_get_first_day(-12),
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NaiveDate::from_ymd(2013, 1, 1)
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NaiveDate::from_ymd(2022, 10, 29).checked_add_months(Months::new(16)),
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Some(NaiveDate::from_ymd(2024, 2, 29))
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);
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// add into december
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assert_eq!(
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NaiveDate::from_ymd(2014, 1, 10).add_months_get_first_day(-13),
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NaiveDate::from_ymd(2012, 12, 1)
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NaiveDate::from_ymd(2022, 10, 31).checked_add_months(Months::new(2)),
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Some(NaiveDate::from_ymd(2022, 12, 31))
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);
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// sub into december
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assert_eq!(
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NaiveDate::from_ymd(2022, 10, 31).checked_sub_months(Months::new(10)),
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Some(NaiveDate::from_ymd(2021, 12, 31))
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);
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// add into january
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assert_eq!(
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NaiveDate::from_ymd(2022, 8, 3).checked_add_months(Months::new(5)),
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Some(NaiveDate::from_ymd(2023, 1, 3))
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);
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// sub into january
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assert_eq!(
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NaiveDate::from_ymd(2022, 8, 3).checked_sub_months(Months::new(7)),
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Some(NaiveDate::from_ymd(2022, 1, 3))
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);
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}
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