Auto merge of #122616 - Jules-Bertholet:casemappingiter-layout, r=Nilstrieb
Optimize `core::char::CaseMappingIter` Godbolt says this saves a few instructions… `@rustbot` label T-libs A-layout C-optimization
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1c19595575
@ -42,7 +42,7 @@
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use crate::error::Error;
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use crate::escape;
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use crate::fmt::{self, Write};
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use crate::iter::FusedIterator;
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use crate::iter::{FusedIterator, TrustedLen, TrustedRandomAccess, TrustedRandomAccessNoCoerce};
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use crate::num::NonZero;
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pub(crate) use self::methods::EscapeDebugExtArgs;
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@ -373,176 +373,229 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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}
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}
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/// Returns an iterator that yields the lowercase equivalent of a `char`.
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///
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/// This `struct` is created by the [`to_lowercase`] method on [`char`]. See
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/// its documentation for more.
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///
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/// [`to_lowercase`]: char::to_lowercase
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#[stable(feature = "rust1", since = "1.0.0")]
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#[derive(Debug, Clone)]
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pub struct ToLowercase(CaseMappingIter);
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macro_rules! casemappingiter_impls {
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($(#[$attr:meta])* $ITER_NAME:ident) => {
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$(#[$attr])*
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#[stable(feature = "rust1", since = "1.0.0")]
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#[derive(Debug, Clone)]
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pub struct $ITER_NAME(CaseMappingIter);
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#[stable(feature = "rust1", since = "1.0.0")]
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impl Iterator for ToLowercase {
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type Item = char;
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fn next(&mut self) -> Option<char> {
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self.0.next()
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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self.0.size_hint()
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#[stable(feature = "rust1", since = "1.0.0")]
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impl Iterator for $ITER_NAME {
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type Item = char;
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fn next(&mut self) -> Option<char> {
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self.0.next()
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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self.0.size_hint()
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}
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fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
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where
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Fold: FnMut(Acc, Self::Item) -> Acc,
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{
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self.0.fold(init, fold)
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}
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fn count(self) -> usize {
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self.0.count()
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}
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fn last(self) -> Option<Self::Item> {
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self.0.last()
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}
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fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
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self.0.advance_by(n)
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}
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unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
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// SAFETY: just forwarding requirements to caller
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unsafe { self.0.__iterator_get_unchecked(idx) }
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}
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}
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#[stable(feature = "case_mapping_double_ended", since = "1.59.0")]
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impl DoubleEndedIterator for $ITER_NAME {
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fn next_back(&mut self) -> Option<char> {
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self.0.next_back()
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}
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fn rfold<Acc, Fold>(self, init: Acc, rfold: Fold) -> Acc
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where
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Fold: FnMut(Acc, Self::Item) -> Acc,
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{
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self.0.rfold(init, rfold)
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}
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fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
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self.0.advance_back_by(n)
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}
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}
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#[stable(feature = "fused", since = "1.26.0")]
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impl FusedIterator for $ITER_NAME {}
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#[stable(feature = "exact_size_case_mapping_iter", since = "1.35.0")]
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impl ExactSizeIterator for $ITER_NAME {
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fn len(&self) -> usize {
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self.0.len()
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}
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fn is_empty(&self) -> bool {
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self.0.is_empty()
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}
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}
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// SAFETY: forwards to inner `array::IntoIter`
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#[unstable(feature = "trusted_len", issue = "37572")]
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unsafe impl TrustedLen for $ITER_NAME {}
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// SAFETY: forwards to inner `array::IntoIter`
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#[doc(hidden)]
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#[unstable(feature = "std_internals", issue = "none")]
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unsafe impl TrustedRandomAccessNoCoerce for $ITER_NAME {
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const MAY_HAVE_SIDE_EFFECT: bool = false;
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}
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// SAFETY: this iter has no subtypes/supertypes
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#[doc(hidden)]
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#[unstable(feature = "std_internals", issue = "none")]
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unsafe impl TrustedRandomAccess for $ITER_NAME {}
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#[stable(feature = "char_struct_display", since = "1.16.0")]
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impl fmt::Display for $ITER_NAME {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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fmt::Display::fmt(&self.0, f)
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}
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}
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}
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}
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#[stable(feature = "case_mapping_double_ended", since = "1.59.0")]
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impl DoubleEndedIterator for ToLowercase {
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fn next_back(&mut self) -> Option<char> {
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self.0.next_back()
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}
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casemappingiter_impls! {
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/// Returns an iterator that yields the lowercase equivalent of a `char`.
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///
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/// This `struct` is created by the [`to_lowercase`] method on [`char`]. See
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/// its documentation for more.
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///
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/// [`to_lowercase`]: char::to_lowercase
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ToLowercase
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}
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#[stable(feature = "fused", since = "1.26.0")]
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impl FusedIterator for ToLowercase {}
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#[stable(feature = "exact_size_case_mapping_iter", since = "1.35.0")]
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impl ExactSizeIterator for ToLowercase {}
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/// Returns an iterator that yields the uppercase equivalent of a `char`.
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///
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/// This `struct` is created by the [`to_uppercase`] method on [`char`]. See
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/// its documentation for more.
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///
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/// [`to_uppercase`]: char::to_uppercase
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#[stable(feature = "rust1", since = "1.0.0")]
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#[derive(Debug, Clone)]
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pub struct ToUppercase(CaseMappingIter);
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#[stable(feature = "rust1", since = "1.0.0")]
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impl Iterator for ToUppercase {
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type Item = char;
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fn next(&mut self) -> Option<char> {
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self.0.next()
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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self.0.size_hint()
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}
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casemappingiter_impls! {
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/// Returns an iterator that yields the uppercase equivalent of a `char`.
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///
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/// This `struct` is created by the [`to_uppercase`] method on [`char`]. See
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/// its documentation for more.
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///
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/// [`to_uppercase`]: char::to_uppercase
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ToUppercase
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}
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#[stable(feature = "case_mapping_double_ended", since = "1.59.0")]
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impl DoubleEndedIterator for ToUppercase {
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fn next_back(&mut self) -> Option<char> {
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self.0.next_back()
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}
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}
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#[stable(feature = "fused", since = "1.26.0")]
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impl FusedIterator for ToUppercase {}
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#[stable(feature = "exact_size_case_mapping_iter", since = "1.35.0")]
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impl ExactSizeIterator for ToUppercase {}
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#[derive(Debug, Clone)]
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enum CaseMappingIter {
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Three(char, char, char),
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Two(char, char),
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One(char),
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Zero,
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}
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struct CaseMappingIter(core::array::IntoIter<char, 3>);
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impl CaseMappingIter {
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#[inline]
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fn new(chars: [char; 3]) -> CaseMappingIter {
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let mut iter = chars.into_iter();
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if chars[2] == '\0' {
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iter.next_back();
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if chars[1] == '\0' {
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CaseMappingIter::One(chars[0]) // Including if chars[0] == '\0'
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} else {
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CaseMappingIter::Two(chars[0], chars[1])
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iter.next_back();
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// Deliberately don't check `chars[0]`,
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// as '\0' lowercases to itself
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}
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} else {
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CaseMappingIter::Three(chars[0], chars[1], chars[2])
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}
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CaseMappingIter(iter)
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}
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}
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impl Iterator for CaseMappingIter {
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type Item = char;
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fn next(&mut self) -> Option<char> {
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match *self {
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CaseMappingIter::Three(a, b, c) => {
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*self = CaseMappingIter::Two(b, c);
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Some(a)
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}
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CaseMappingIter::Two(b, c) => {
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*self = CaseMappingIter::One(c);
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Some(b)
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}
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CaseMappingIter::One(c) => {
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*self = CaseMappingIter::Zero;
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Some(c)
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}
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CaseMappingIter::Zero => None,
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}
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self.0.next()
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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let size = match self {
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CaseMappingIter::Three(..) => 3,
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CaseMappingIter::Two(..) => 2,
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CaseMappingIter::One(_) => 1,
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CaseMappingIter::Zero => 0,
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};
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(size, Some(size))
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self.0.size_hint()
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}
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fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
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where
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Fold: FnMut(Acc, Self::Item) -> Acc,
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{
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self.0.fold(init, fold)
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}
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fn count(self) -> usize {
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self.0.count()
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}
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fn last(self) -> Option<Self::Item> {
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self.0.last()
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}
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fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
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self.0.advance_by(n)
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}
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unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
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// SAFETY: just forwarding requirements to caller
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unsafe { self.0.__iterator_get_unchecked(idx) }
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}
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}
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impl DoubleEndedIterator for CaseMappingIter {
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fn next_back(&mut self) -> Option<char> {
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match *self {
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CaseMappingIter::Three(a, b, c) => {
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*self = CaseMappingIter::Two(a, b);
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Some(c)
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}
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CaseMappingIter::Two(b, c) => {
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*self = CaseMappingIter::One(b);
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Some(c)
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}
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CaseMappingIter::One(c) => {
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*self = CaseMappingIter::Zero;
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Some(c)
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}
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CaseMappingIter::Zero => None,
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}
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self.0.next_back()
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}
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fn rfold<Acc, Fold>(self, init: Acc, rfold: Fold) -> Acc
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where
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Fold: FnMut(Acc, Self::Item) -> Acc,
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{
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self.0.rfold(init, rfold)
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}
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fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
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self.0.advance_back_by(n)
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}
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}
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impl ExactSizeIterator for CaseMappingIter {
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fn len(&self) -> usize {
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self.0.len()
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}
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fn is_empty(&self) -> bool {
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self.0.is_empty()
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}
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}
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impl FusedIterator for CaseMappingIter {}
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// SAFETY: forwards to inner `array::IntoIter`
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unsafe impl TrustedLen for CaseMappingIter {}
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// SAFETY: forwards to inner `array::IntoIter`
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unsafe impl TrustedRandomAccessNoCoerce for CaseMappingIter {
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const MAY_HAVE_SIDE_EFFECT: bool = false;
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}
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// SAFETY: `CaseMappingIter` has no subtypes/supertypes
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unsafe impl TrustedRandomAccess for CaseMappingIter {}
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impl fmt::Display for CaseMappingIter {
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#[inline]
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match *self {
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CaseMappingIter::Three(a, b, c) => {
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f.write_char(a)?;
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f.write_char(b)?;
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f.write_char(c)
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}
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CaseMappingIter::Two(b, c) => {
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f.write_char(b)?;
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f.write_char(c)
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}
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CaseMappingIter::One(c) => f.write_char(c),
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CaseMappingIter::Zero => Ok(()),
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for c in self.0.clone() {
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f.write_char(c)?;
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}
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}
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}
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#[stable(feature = "char_struct_display", since = "1.16.0")]
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impl fmt::Display for ToLowercase {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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fmt::Display::fmt(&self.0, f)
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}
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}
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#[stable(feature = "char_struct_display", since = "1.16.0")]
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impl fmt::Display for ToUppercase {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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fmt::Display::fmt(&self.0, f)
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Ok(())
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}
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}
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