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use core::{
fmt::{self, Debug},
iter::FusedIterator,
};
use crate::Weekday;
/// A collection of [`Weekday`]s stored as a single byte.
///
/// This type is `Copy` and provides efficient set-like and slice-like operations.
/// Many operations are `const` as well.
///
/// Implemented as a bitmask where bits 1-7 correspond to Monday-Sunday.
#[derive(Clone, Copy, Default, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct WeekdaySet(u8); // Invariant: the 8-th bit is always 0.
impl WeekdaySet {
/// Create a `WeekdaySet` from an array of [`Weekday`]s.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::EMPTY, WeekdaySet::from_array([]));
/// assert_eq!(WeekdaySet::single(Mon), WeekdaySet::from_array([Mon]));
/// assert_eq!(WeekdaySet::ALL, WeekdaySet::from_array([Mon, Tue, Wed, Thu, Fri, Sat, Sun]));
/// ```
pub const fn from_array<const C: usize>(days: [Weekday; C]) -> Self {
let mut acc = Self::EMPTY;
let mut idx = 0;
while idx < days.len() {
acc.0 |= Self::single(days[idx]).0;
idx += 1;
}
acc
}
/// Create a `WeekdaySet` from a single [`Weekday`].
pub const fn single(weekday: Weekday) -> Self {
match weekday {
Weekday::Mon => Self(0b000_0001),
Weekday::Tue => Self(0b000_0010),
Weekday::Wed => Self(0b000_0100),
Weekday::Thu => Self(0b000_1000),
Weekday::Fri => Self(0b001_0000),
Weekday::Sat => Self(0b010_0000),
Weekday::Sun => Self(0b100_0000),
}
}
/// Returns `Some(day)` if this collection contains exactly one day.
///
/// Returns `None` otherwise.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::single(Mon).single_day(), Some(Mon));
/// assert_eq!(WeekdaySet::from_array([Mon, Tue]).single_day(), None);
/// assert_eq!(WeekdaySet::EMPTY.single_day(), None);
/// assert_eq!(WeekdaySet::ALL.single_day(), None);
/// ```
pub const fn single_day(self) -> Option<Weekday> {
match self {
Self(0b000_0001) => Some(Weekday::Mon),
Self(0b000_0010) => Some(Weekday::Tue),
Self(0b000_0100) => Some(Weekday::Wed),
Self(0b000_1000) => Some(Weekday::Thu),
Self(0b001_0000) => Some(Weekday::Fri),
Self(0b010_0000) => Some(Weekday::Sat),
Self(0b100_0000) => Some(Weekday::Sun),
_ => None,
}
}
/// Adds a day to the collection.
///
/// Returns `true` if the day was new to the collection.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// let mut weekdays = WeekdaySet::single(Mon);
/// assert!(weekdays.insert(Tue));
/// assert!(!weekdays.insert(Tue));
/// ```
pub fn insert(&mut self, day: Weekday) -> bool {
if self.contains(day) {
return false;
}
self.0 |= Self::single(day).0;
true
}
/// Removes a day from the collection.
///
/// Returns `true` if the collection did contain the day.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// let mut weekdays = WeekdaySet::single(Mon);
/// assert!(weekdays.remove(Mon));
/// assert!(!weekdays.remove(Mon));
/// ```
pub fn remove(&mut self, day: Weekday) -> bool {
if self.contains(day) {
self.0 &= !Self::single(day).0;
return true;
}
false
}
/// Returns `true` if `other` contains all days in `self`.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert!(WeekdaySet::single(Mon).is_subset(WeekdaySet::ALL));
/// assert!(!WeekdaySet::single(Mon).is_subset(WeekdaySet::EMPTY));
/// assert!(WeekdaySet::EMPTY.is_subset(WeekdaySet::single(Mon)));
/// ```
pub const fn is_subset(self, other: Self) -> bool {
self.intersection(other).0 == self.0
}
/// Returns days that are in both `self` and `other`.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::single(Mon).intersection(WeekdaySet::single(Mon)), WeekdaySet::single(Mon));
/// assert_eq!(WeekdaySet::single(Mon).intersection(WeekdaySet::single(Tue)), WeekdaySet::EMPTY);
/// assert_eq!(WeekdaySet::ALL.intersection(WeekdaySet::single(Mon)), WeekdaySet::single(Mon));
/// assert_eq!(WeekdaySet::ALL.intersection(WeekdaySet::EMPTY), WeekdaySet::EMPTY);
/// ```
pub const fn intersection(self, other: Self) -> Self {
Self(self.0 & other.0)
}
/// Returns days that are in either `self` or `other`.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::single(Mon).union(WeekdaySet::single(Mon)), WeekdaySet::single(Mon));
/// assert_eq!(WeekdaySet::single(Mon).union(WeekdaySet::single(Tue)), WeekdaySet::from_array([Mon, Tue]));
/// assert_eq!(WeekdaySet::ALL.union(WeekdaySet::single(Mon)), WeekdaySet::ALL);
/// assert_eq!(WeekdaySet::ALL.union(WeekdaySet::EMPTY), WeekdaySet::ALL);
/// ```
pub const fn union(self, other: Self) -> Self {
Self(self.0 | other.0)
}
/// Returns days that are in `self` or `other` but not in both.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::single(Mon).symmetric_difference(WeekdaySet::single(Mon)), WeekdaySet::EMPTY);
/// assert_eq!(WeekdaySet::single(Mon).symmetric_difference(WeekdaySet::single(Tue)), WeekdaySet::from_array([Mon, Tue]));
/// assert_eq!(
/// WeekdaySet::ALL.symmetric_difference(WeekdaySet::single(Mon)),
/// WeekdaySet::from_array([Tue, Wed, Thu, Fri, Sat, Sun]),
/// );
/// assert_eq!(WeekdaySet::ALL.symmetric_difference(WeekdaySet::EMPTY), WeekdaySet::ALL);
/// ```
pub const fn symmetric_difference(self, other: Self) -> Self {
Self(self.0 ^ other.0)
}
/// Returns days that are in `self` but not in `other`.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::single(Mon).difference(WeekdaySet::single(Mon)), WeekdaySet::EMPTY);
/// assert_eq!(WeekdaySet::single(Mon).difference(WeekdaySet::single(Tue)), WeekdaySet::single(Mon));
/// assert_eq!(WeekdaySet::EMPTY.difference(WeekdaySet::single(Mon)), WeekdaySet::EMPTY);
/// ```
pub const fn difference(self, other: Self) -> Self {
Self(self.0 & !other.0)
}
/// Get the first day in the collection, starting from Monday.
///
/// Returns `None` if the collection is empty.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::single(Mon).first(), Some(Mon));
/// assert_eq!(WeekdaySet::single(Tue).first(), Some(Tue));
/// assert_eq!(WeekdaySet::ALL.first(), Some(Mon));
/// assert_eq!(WeekdaySet::EMPTY.first(), None);
/// ```
pub const fn first(self) -> Option<Weekday> {
if self.is_empty() {
return None;
}
// Find the first non-zero bit.
let bit = 1 << self.0.trailing_zeros();
Self(bit).single_day()
}
/// Get the last day in the collection, starting from Sunday.
///
/// Returns `None` if the collection is empty.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::single(Mon).last(), Some(Mon));
/// assert_eq!(WeekdaySet::single(Sun).last(), Some(Sun));
/// assert_eq!(WeekdaySet::from_array([Mon, Tue]).last(), Some(Tue));
/// assert_eq!(WeekdaySet::EMPTY.last(), None);
/// ```
pub fn last(self) -> Option<Weekday> {
if self.is_empty() {
return None;
}
// Find the last non-zero bit.
let bit = 1 << (7 - self.0.leading_zeros());
Self(bit).single_day()
}
/// Split the collection in two at the given day.
///
/// Returns a tuple `(before, after)`. `before` contains all days starting from Monday
/// up to but __not__ including `weekday`. `after` contains all days starting from `weekday`
/// up to and including Sunday.
const fn split_at(self, weekday: Weekday) -> (Self, Self) {
let days_after = 0b1000_0000 - Self::single(weekday).0;
let days_before = days_after ^ 0b0111_1111;
(Self(self.0 & days_before), Self(self.0 & days_after))
}
/// Iterate over the [`Weekday`]s in the collection starting from a given day.
///
/// Wraps around from Sunday to Monday if necessary.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// let weekdays = WeekdaySet::from_array([Mon, Wed, Fri]);
/// let mut iter = weekdays.iter(Wed);
/// assert_eq!(iter.next(), Some(Wed));
/// assert_eq!(iter.next(), Some(Fri));
/// assert_eq!(iter.next(), Some(Mon));
/// assert_eq!(iter.next(), None);
/// ```
pub const fn iter(self, start: Weekday) -> WeekdaySetIter {
WeekdaySetIter { days: self, start }
}
/// Returns `true` if the collection contains the given day.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert!(WeekdaySet::single(Mon).contains(Mon));
/// assert!(WeekdaySet::from_array([Mon, Tue]).contains(Tue));
/// assert!(!WeekdaySet::single(Mon).contains(Tue));
/// ```
pub const fn contains(self, day: Weekday) -> bool {
self.0 & Self::single(day).0 != 0
}
/// Returns `true` if the collection is empty.
///
/// # Example
/// ```
/// # use chrono::{Weekday, WeekdaySet};
/// assert!(WeekdaySet::EMPTY.is_empty());
/// assert!(!WeekdaySet::single(Weekday::Mon).is_empty());
/// ```
pub const fn is_empty(self) -> bool {
self.len() == 0
}
/// Returns the number of days in the collection.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(WeekdaySet::single(Mon).len(), 1);
/// assert_eq!(WeekdaySet::from_array([Mon, Wed, Fri]).len(), 3);
/// assert_eq!(WeekdaySet::ALL.len(), 7);
/// ```
pub const fn len(self) -> u8 {
self.0.count_ones() as u8
}
/// An empty `WeekdaySet`.
pub const EMPTY: Self = Self(0b000_0000);
/// A `WeekdaySet` containing all seven `Weekday`s.
pub const ALL: Self = Self(0b111_1111);
}
/// Print the underlying bitmask, padded to 7 bits.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!(format!("{:?}", WeekdaySet::single(Mon)), "WeekdaySet(0000001)");
/// assert_eq!(format!("{:?}", WeekdaySet::single(Tue)), "WeekdaySet(0000010)");
/// assert_eq!(format!("{:?}", WeekdaySet::ALL), "WeekdaySet(1111111)");
/// ```
impl Debug for WeekdaySet {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "WeekdaySet({:0>7b})", self.0)
}
}
/// An iterator over a collection of weekdays, starting from a given day.
///
/// See [`WeekdaySet::iter()`].
#[derive(Debug, Clone)]
pub struct WeekdaySetIter {
days: WeekdaySet,
start: Weekday,
}
impl Iterator for WeekdaySetIter {
type Item = Weekday;
fn next(&mut self) -> Option<Self::Item> {
if self.days.is_empty() {
return None;
}
// Split the collection in two at `start`.
// Look for the first day among the days after `start` first, including `start` itself.
// If there are no days after `start`, look for the first day among the days before `start`.
let (before, after) = self.days.split_at(self.start);
let days = if after.is_empty() { before } else { after };
let next = days.first().expect("the collection is not empty");
self.days.remove(next);
Some(next)
}
}
impl DoubleEndedIterator for WeekdaySetIter {
fn next_back(&mut self) -> Option<Self::Item> {
if self.days.is_empty() {
return None;
}
// Split the collection in two at `start`.
// Look for the last day among the days before `start` first, NOT including `start` itself.
// If there are no days before `start`, look for the last day among the days after `start`.
let (before, after) = self.days.split_at(self.start);
let days = if before.is_empty() { after } else { before };
let next_back = days.last().expect("the collection is not empty");
self.days.remove(next_back);
Some(next_back)
}
}
impl ExactSizeIterator for WeekdaySetIter {
fn len(&self) -> usize {
self.days.len().into()
}
}
impl FusedIterator for WeekdaySetIter {}
/// Print the collection as a slice-like list of weekdays.
///
/// # Example
/// ```
/// # use chrono::WeekdaySet;
/// use chrono::Weekday::*;
/// assert_eq!("[]", WeekdaySet::EMPTY.to_string());
/// assert_eq!("[Mon]", WeekdaySet::single(Mon).to_string());
/// assert_eq!("[Mon, Fri, Sun]", WeekdaySet::from_array([Mon, Fri, Sun]).to_string());
/// ```
impl fmt::Display for WeekdaySet {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
write!(f, "[")?;
let mut iter = self.iter(Weekday::Mon);
if let Some(first) = iter.next() {
write!(f, "{first}")?;
}
for weekday in iter {
write!(f, ", {weekday}")?;
}
write!(f, "]")
}
}
impl FromIterator<Weekday> for WeekdaySet {
fn from_iter<T: IntoIterator<Item = Weekday>>(iter: T) -> Self {
iter.into_iter().map(Self::single).fold(Self::EMPTY, Self::union)
}
}
#[cfg(test)]
mod tests {
use crate::Weekday;
use super::WeekdaySet;
impl WeekdaySet {
/// Iterate over all 128 possible sets, from `EMPTY` to `ALL`.
fn iter_all() -> impl Iterator<Item = Self> {
(0b0000_0000..0b1000_0000).map(Self)
}
}
/// Panics if the 8-th bit of `self` is not 0.
fn assert_8th_bit_invariant(days: WeekdaySet) {
assert!(days.0 & 0b1000_0000 == 0, "the 8-th bit of {days:?} is not 0");
}
#[test]
fn debug_prints_8th_bit_if_not_zero() {
assert_eq!(format!("{:?}", WeekdaySet(0b1000_0000)), "WeekdaySet(10000000)");
}
#[test]
fn bitwise_set_operations_preserve_8th_bit_invariant() {
for set1 in WeekdaySet::iter_all() {
for set2 in WeekdaySet::iter_all() {
assert_8th_bit_invariant(set1.union(set2));
assert_8th_bit_invariant(set1.intersection(set2));
assert_8th_bit_invariant(set1.symmetric_difference(set2));
}
}
}
/// Test `split_at` on all possible arguments.
#[test]
fn split_at_is_equivalent_to_iterating() {
use Weekday::*;
// `split_at()` is used in `iter()`, so we must not iterate
// over all days with `WeekdaySet::ALL.iter(Mon)`.
const WEEK: [Weekday; 7] = [Mon, Tue, Wed, Thu, Fri, Sat, Sun];
for weekdays in WeekdaySet::iter_all() {
for split_day in WEEK {
let expected_before: WeekdaySet = WEEK
.into_iter()
.take_while(|&day| day != split_day)
.filter(|&day| weekdays.contains(day))
.collect();
let expected_after: WeekdaySet = WEEK
.into_iter()
.skip_while(|&day| day != split_day)
.filter(|&day| weekdays.contains(day))
.collect();
assert_eq!(
(expected_before, expected_after),
weekdays.split_at(split_day),
"split_at({split_day}) failed for {weekdays}",
);
}
}
}
}