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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
commit | 26a029d407be480d791972afb5975cf62c9360a6 (patch) | |
tree | f435a8308119effd964b339f76abb83a57c29483 /third_party/rust/itertools/src/zip_longest.rs | |
parent | Initial commit. (diff) | |
download | firefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz firefox-26a029d407be480d791972afb5975cf62c9360a6.zip |
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/rust/itertools/src/zip_longest.rs')
-rw-r--r-- | third_party/rust/itertools/src/zip_longest.rs | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/third_party/rust/itertools/src/zip_longest.rs b/third_party/rust/itertools/src/zip_longest.rs new file mode 100644 index 0000000000..cb9a7bacb2 --- /dev/null +++ b/third_party/rust/itertools/src/zip_longest.rs @@ -0,0 +1,83 @@ +use std::cmp::Ordering::{Equal, Greater, Less}; +use super::size_hint; +use std::iter::{Fuse, FusedIterator}; + +use crate::either_or_both::EitherOrBoth; + +// ZipLongest originally written by SimonSapin, +// and dedicated to itertools https://github.com/rust-lang/rust/pull/19283 + +/// An iterator which iterates two other iterators simultaneously +/// +/// This iterator is *fused*. +/// +/// See [`.zip_longest()`](crate::Itertools::zip_longest) for more information. +#[derive(Clone, Debug)] +#[must_use = "iterator adaptors are lazy and do nothing unless consumed"] +pub struct ZipLongest<T, U> { + a: Fuse<T>, + b: Fuse<U>, +} + +/// Create a new `ZipLongest` iterator. +pub fn zip_longest<T, U>(a: T, b: U) -> ZipLongest<T, U> + where T: Iterator, + U: Iterator +{ + ZipLongest { + a: a.fuse(), + b: b.fuse(), + } +} + +impl<T, U> Iterator for ZipLongest<T, U> + where T: Iterator, + U: Iterator +{ + type Item = EitherOrBoth<T::Item, U::Item>; + + #[inline] + fn next(&mut self) -> Option<Self::Item> { + match (self.a.next(), self.b.next()) { + (None, None) => None, + (Some(a), None) => Some(EitherOrBoth::Left(a)), + (None, Some(b)) => Some(EitherOrBoth::Right(b)), + (Some(a), Some(b)) => Some(EitherOrBoth::Both(a, b)), + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + size_hint::max(self.a.size_hint(), self.b.size_hint()) + } +} + +impl<T, U> DoubleEndedIterator for ZipLongest<T, U> + where T: DoubleEndedIterator + ExactSizeIterator, + U: DoubleEndedIterator + ExactSizeIterator +{ + #[inline] + fn next_back(&mut self) -> Option<Self::Item> { + match self.a.len().cmp(&self.b.len()) { + Equal => match (self.a.next_back(), self.b.next_back()) { + (None, None) => None, + (Some(a), Some(b)) => Some(EitherOrBoth::Both(a, b)), + // These can only happen if .len() is inconsistent with .next_back() + (Some(a), None) => Some(EitherOrBoth::Left(a)), + (None, Some(b)) => Some(EitherOrBoth::Right(b)), + }, + Greater => self.a.next_back().map(EitherOrBoth::Left), + Less => self.b.next_back().map(EitherOrBoth::Right), + } + } +} + +impl<T, U> ExactSizeIterator for ZipLongest<T, U> + where T: ExactSizeIterator, + U: ExactSizeIterator +{} + +impl<T, U> FusedIterator for ZipLongest<T, U> + where T: Iterator, + U: Iterator +{} |