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Move Datelike and Timelike traits into a traits module
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@djc
djc committed Mar 22, 2022
1 parent 861378f commit 65dd625
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230 changes: 2 additions & 228 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -658,182 +658,8 @@ pub use weekday::{ParseWeekdayError, Weekday};
mod month;
pub use month::{Month, ParseMonthError};

/// The common set of methods for date component.
pub trait Datelike: Sized {
/// Returns the year number in the [calendar date](./naive/struct.NaiveDate.html#calendar-date).
fn year(&self) -> i32;

/// Returns the absolute year number starting from 1 with a boolean flag,
/// which is false when the year predates the epoch (BCE/BC) and true otherwise (CE/AD).
#[inline]
fn year_ce(&self) -> (bool, u32) {
let year = self.year();
if year < 1 {
(false, (1 - year) as u32)
} else {
(true, year as u32)
}
}

/// Returns the month number starting from 1.
///
/// The return value ranges from 1 to 12.
fn month(&self) -> u32;

/// Returns the month number starting from 0.
///
/// The return value ranges from 0 to 11.
fn month0(&self) -> u32;

/// Returns the day of month starting from 1.
///
/// The return value ranges from 1 to 31. (The last day of month differs by months.)
fn day(&self) -> u32;

/// Returns the day of month starting from 0.
///
/// The return value ranges from 0 to 30. (The last day of month differs by months.)
fn day0(&self) -> u32;

/// Returns the day of year starting from 1.
///
/// The return value ranges from 1 to 366. (The last day of year differs by years.)
fn ordinal(&self) -> u32;

/// Returns the day of year starting from 0.
///
/// The return value ranges from 0 to 365. (The last day of year differs by years.)
fn ordinal0(&self) -> u32;

/// Returns the day of week.
fn weekday(&self) -> Weekday;

/// Returns the ISO week.
fn iso_week(&self) -> IsoWeek;

/// Makes a new value with the year number changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_year(&self, year: i32) -> Option<Self>;

/// Makes a new value with the month number (starting from 1) changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_month(&self, month: u32) -> Option<Self>;

/// Makes a new value with the month number (starting from 0) changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_month0(&self, month0: u32) -> Option<Self>;

/// Makes a new value with the day of month (starting from 1) changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_day(&self, day: u32) -> Option<Self>;

/// Makes a new value with the day of month (starting from 0) changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_day0(&self, day0: u32) -> Option<Self>;

/// Makes a new value with the day of year (starting from 1) changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_ordinal(&self, ordinal: u32) -> Option<Self>;

/// Makes a new value with the day of year (starting from 0) changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_ordinal0(&self, ordinal0: u32) -> Option<Self>;

/// Counts the days in the proleptic Gregorian calendar, with January 1, Year 1 (CE) as day 1.
///
/// # Examples
///
/// ```
/// use chrono::{NaiveDate, Datelike};
///
/// assert_eq!(NaiveDate::from_ymd(1970, 1, 1).num_days_from_ce(), 719_163);
/// assert_eq!(NaiveDate::from_ymd(2, 1, 1).num_days_from_ce(), 366);
/// assert_eq!(NaiveDate::from_ymd(1, 1, 1).num_days_from_ce(), 1);
/// assert_eq!(NaiveDate::from_ymd(0, 1, 1).num_days_from_ce(), -365);
/// ```
fn num_days_from_ce(&self) -> i32 {
// See test_num_days_from_ce_against_alternative_impl below for a more straightforward
// implementation.

// we know this wouldn't overflow since year is limited to 1/2^13 of i32's full range.
let mut year = self.year() - 1;
let mut ndays = 0;
if year < 0 {
let excess = 1 + (-year) / 400;
year += excess * 400;
ndays -= excess * 146_097;
}
let div_100 = year / 100;
ndays += ((year * 1461) >> 2) - div_100 + (div_100 >> 2);
ndays + self.ordinal() as i32
}
}

/// The common set of methods for time component.
pub trait Timelike: Sized {
/// Returns the hour number from 0 to 23.
fn hour(&self) -> u32;

/// Returns the hour number from 1 to 12 with a boolean flag,
/// which is false for AM and true for PM.
#[inline]
fn hour12(&self) -> (bool, u32) {
let hour = self.hour();
let mut hour12 = hour % 12;
if hour12 == 0 {
hour12 = 12;
}
(hour >= 12, hour12)
}

/// Returns the minute number from 0 to 59.
fn minute(&self) -> u32;

/// Returns the second number from 0 to 59.
fn second(&self) -> u32;

/// Returns the number of nanoseconds since the whole non-leap second.
/// The range from 1,000,000,000 to 1,999,999,999 represents
/// the [leap second](./naive/struct.NaiveTime.html#leap-second-handling).
fn nanosecond(&self) -> u32;

/// Makes a new value with the hour number changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_hour(&self, hour: u32) -> Option<Self>;

/// Makes a new value with the minute number changed.
///
/// Returns `None` when the resulting value would be invalid.
fn with_minute(&self, min: u32) -> Option<Self>;

/// Makes a new value with the second number changed.
///
/// Returns `None` when the resulting value would be invalid.
/// As with the [`second`](#tymethod.second) method,
/// the input range is restricted to 0 through 59.
fn with_second(&self, sec: u32) -> Option<Self>;

/// Makes a new value with nanoseconds since the whole non-leap second changed.
///
/// Returns `None` when the resulting value would be invalid.
/// As with the [`nanosecond`](#tymethod.nanosecond) method,
/// the input range can exceed 1,000,000,000 for leap seconds.
fn with_nanosecond(&self, nano: u32) -> Option<Self>;

/// Returns the number of non-leap seconds past the last midnight.
#[inline]
fn num_seconds_from_midnight(&self) -> u32 {
self.hour() * 3600 + self.minute() * 60 + self.second()
}
}
mod traits;
pub use traits::{Datelike, Timelike};

#[cfg(test)]
extern crate num_iter;
Expand Down Expand Up @@ -890,55 +716,3 @@ mod test {
assert_eq!((dt.year(), dt.month(), dt.day()), (2019, 1, 28));
}
}

/// Tests `Datelike::num_days_from_ce` against an alternative implementation.
///
/// The alternative implementation is not as short as the current one but it is simpler to
/// understand, with less unexplained magic constants.
#[test]
fn test_num_days_from_ce_against_alternative_impl() {
/// Returns the number of multiples of `div` in the range `start..end`.
///
/// If the range `start..end` is back-to-front, i.e. `start` is greater than `end`, the
/// behaviour is defined by the following equation:
/// `in_between(start, end, div) == - in_between(end, start, div)`.
///
/// When `div` is 1, this is equivalent to `end - start`, i.e. the length of `start..end`.
///
/// # Panics
///
/// Panics if `div` is not positive.
fn in_between(start: i32, end: i32, div: i32) -> i32 {
assert!(div > 0, "in_between: nonpositive div = {}", div);
let start = (start.div_euclid(div), start.rem_euclid(div));
let end = (end.div_euclid(div), end.rem_euclid(div));
// The lowest multiple of `div` greater than or equal to `start`, divided.
let start = start.0 + (start.1 != 0) as i32;
// The lowest multiple of `div` greater than or equal to `end`, divided.
let end = end.0 + (end.1 != 0) as i32;
end - start
}

/// Alternative implementation to `Datelike::num_days_from_ce`
fn num_days_from_ce<Date: Datelike>(date: &Date) -> i32 {
let year = date.year();
let diff = move |div| in_between(1, year, div);
// 365 days a year, one more in leap years. In the gregorian calendar, leap years are all
// the multiples of 4 except multiples of 100 but including multiples of 400.
date.ordinal() as i32 + 365 * diff(1) + diff(4) - diff(100) + diff(400)
}

use num_iter::range_inclusive;

for year in range_inclusive(naive::MIN_DATE.year(), naive::MAX_DATE.year()) {
let jan1_year = NaiveDate::from_ymd(year, 1, 1);
assert_eq!(
jan1_year.num_days_from_ce(),
num_days_from_ce(&jan1_year),
"on {:?}",
jan1_year
);
let mid_year = jan1_year + Duration::days(133);
assert_eq!(mid_year.num_days_from_ce(), num_days_from_ce(&mid_year), "on {:?}", mid_year);
}
}
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