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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
//! Utilities for performing ordering operations on locales.
use core::cmp::Ordering;
/// The result of a subtag iterator comparison operation.
///
/// See [`Locale::strict_cmp_iter`].
///
/// # Examples
///
/// Check whether a stream of subtags contains two expected locales back-to-back:
///
/// ```
/// use icu::locid::{locale, Locale, SubtagOrderingResult};
/// use std::cmp::Ordering;
///
/// let subtags = b"en-US-it-IT".split(|b| *b == b'-');
/// let locales = [locale!("en-US"), locale!("it-IT")];
/// let mut result = SubtagOrderingResult::Subtags(subtags);
/// for loc in locales.iter() {
/// match result {
/// SubtagOrderingResult::Subtags(it) => {
/// result = loc.strict_cmp_iter(it);
/// }
/// SubtagOrderingResult::Ordering(ord) => break,
/// }
/// }
///
/// assert_eq!(Ordering::Equal, result.end());
/// ```
///
/// [`Locale::strict_cmp_iter`]: crate::Locale::strict_cmp_iter
#[allow(clippy::exhaustive_enums)] // well-defined exhaustive enum semantics
#[derive(Debug)]
pub enum SubtagOrderingResult<I> {
/// Potentially remaining subtags after the comparison operation.
Subtags(I),
/// Resolved ordering between the locale object and the subtags.
Ordering(Ordering),
}
impl<I> SubtagOrderingResult<I>
where
I: Iterator,
{
/// Invoke this function if there are no remaining locale objects to chain in order to get
/// a fully resolved [`Ordering`].
#[inline]
pub fn end(self) -> Ordering {
match self {
Self::Subtags(mut it) => match it.next() {
Some(_) => Ordering::Less,
None => Ordering::Equal,
},
Self::Ordering(o) => o,
}
}
}
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