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Optimize core::char::CaseMappingIter #122616

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merged 2 commits into from
Mar 29, 2024
Merged

Optimize core::char::CaseMappingIter #122616

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1c137b7
Optimize `core::char::CaseMappingIter` layout
Jules-Bertholet Mar 17, 2024
2f1ab2c
Reimplement `CaseMappingIter` with `core::array::IntoIter`
Jules-Bertholet Mar 19, 2024
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54 changes: 27 additions & 27 deletions library/core/src/char/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -443,10 +443,10 @@ impl ExactSizeIterator for ToUppercase {}

#[derive(Debug, Clone)]
enum CaseMappingIter {
Three(char, char, char),
Two(char, char),
One(char),
Zero,
One(char),
Two([char; 2]),
Three([char; 3]),
}

impl CaseMappingIter {
Expand All @@ -455,10 +455,10 @@ impl CaseMappingIter {
if chars[1] == '\0' {
CaseMappingIter::One(chars[0]) // Including if chars[0] == '\0'
} else {
CaseMappingIter::Two(chars[0], chars[1])
CaseMappingIter::Two([chars[0], chars[1]])
}
} else {
CaseMappingIter::Three(chars[0], chars[1], chars[2])
CaseMappingIter::Three([chars[0], chars[1], chars[2]])
}
}
}
Expand All @@ -467,28 +467,28 @@ impl Iterator for CaseMappingIter {
type Item = char;
fn next(&mut self) -> Option<char> {
match *self {
CaseMappingIter::Three(a, b, c) => {
*self = CaseMappingIter::Two(b, c);
Some(a)
CaseMappingIter::Zero => None,
CaseMappingIter::One(c) => {
*self = CaseMappingIter::Zero;
Some(c)
}
CaseMappingIter::Two(b, c) => {
CaseMappingIter::Two([b, c]) => {
*self = CaseMappingIter::One(c);
Some(b)
}
CaseMappingIter::One(c) => {
*self = CaseMappingIter::Zero;
Some(c)
CaseMappingIter::Three([a, b, c]) => {
*self = CaseMappingIter::Two([b, c]);
Some(a)
}
CaseMappingIter::Zero => None,
}
}

fn size_hint(&self) -> (usize, Option<usize>) {
let size = match self {
CaseMappingIter::Three(..) => 3,
CaseMappingIter::Two(..) => 2,
CaseMappingIter::One(_) => 1,
CaseMappingIter::Zero => 0,
CaseMappingIter::One(_) => 1,
CaseMappingIter::Two(..) => 2,
CaseMappingIter::Three(..) => 3,
};
(size, Some(size))
}
Expand All @@ -497,37 +497,37 @@ impl Iterator for CaseMappingIter {
impl DoubleEndedIterator for CaseMappingIter {
fn next_back(&mut self) -> Option<char> {
match *self {
CaseMappingIter::Three(a, b, c) => {
*self = CaseMappingIter::Two(a, b);
CaseMappingIter::Zero => None,
CaseMappingIter::One(c) => {
*self = CaseMappingIter::Zero;
Some(c)
}
CaseMappingIter::Two(b, c) => {
CaseMappingIter::Two([b, c]) => {
*self = CaseMappingIter::One(b);
Some(c)
}
CaseMappingIter::One(c) => {
*self = CaseMappingIter::Zero;
CaseMappingIter::Three([a, b, c]) => {
*self = CaseMappingIter::Two([a, b]);
Some(c)
}
CaseMappingIter::Zero => None,
}
}
}

impl fmt::Display for CaseMappingIter {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self {
CaseMappingIter::Three(a, b, c) => {
f.write_char(a)?;
CaseMappingIter::Zero => Ok(()),
CaseMappingIter::One(c) => f.write_char(c),
CaseMappingIter::Two([b, c]) => {
f.write_char(b)?;
f.write_char(c)
}
CaseMappingIter::Two(b, c) => {
CaseMappingIter::Three([a, b, c]) => {
f.write_char(a)?;
f.write_char(b)?;
f.write_char(c)
}
CaseMappingIter::One(c) => f.write_char(c),
CaseMappingIter::Zero => Ok(()),
}
}
}
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