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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
use core::cmp::Ordering;
use core::fmt;
pub(crate) struct WriteComparator<'a> {
string: &'a [u8],
result: Ordering,
}
/// This is an infallible impl. Functions always return Ok, not Err.
impl<'a> fmt::Write for WriteComparator<'a> {
#[inline]
fn write_str(&mut self, other: &str) -> fmt::Result {
if self.result != Ordering::Equal {
return Ok(());
}
let cmp_len = core::cmp::min(other.len(), self.string.len());
let (this, remainder) = self.string.split_at(cmp_len);
self.string = remainder;
self.result = this.cmp(other.as_bytes());
Ok(())
}
}
impl<'a> WriteComparator<'a> {
#[inline]
pub fn new(string: &'a (impl AsRef<[u8]> + ?Sized)) -> Self {
Self {
string: string.as_ref(),
result: Ordering::Equal,
}
}
#[inline]
pub fn finish(self) -> Ordering {
if matches!(self.result, Ordering::Equal) && !self.string.is_empty() {
// Self is longer than Other
Ordering::Greater
} else {
self.result
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use core::fmt::Write;
mod data {
include!("../tests/data/data.rs");
}
#[test]
fn test_write_char() {
for a in data::KEBAB_CASE_STRINGS {
for b in data::KEBAB_CASE_STRINGS {
let mut wc = WriteComparator::new(a);
for ch in b.chars() {
wc.write_char(ch).unwrap();
}
assert_eq!(a.cmp(b), wc.finish(), "{a} <=> {b}");
}
}
}
#[test]
fn test_write_str() {
for a in data::KEBAB_CASE_STRINGS {
for b in data::KEBAB_CASE_STRINGS {
let mut wc = WriteComparator::new(a);
wc.write_str(b).unwrap();
assert_eq!(a.cmp(b), wc.finish(), "{a} <=> {b}");
}
}
}
#[test]
fn test_mixed() {
for a in data::KEBAB_CASE_STRINGS {
for b in data::KEBAB_CASE_STRINGS {
let mut wc = WriteComparator::new(a);
let mut first = true;
for substr in b.split('-') {
if first {
first = false;
} else {
wc.write_char('-').unwrap();
}
wc.write_str(substr).unwrap();
}
assert_eq!(a.cmp(b), wc.finish(), "{a} <=> {b}");
}
}
}
}