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const fn str::is_char_boundary

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This commit is contained in:
Zachary S 2024-10-23 14:22:32 -05:00
parent 8d94e06ec9
commit 8ee548fcf0
1 changed files with 7 additions and 6 deletions
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13
library/core/src/str/mod.rs
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@ -185,8 +185,9 @@ impl str {
/// ```
#[must_use]
#[stable(feature = "is_char_boundary", since = "1.9.0")]
#[rustc_const_unstable(feature = "const_is_char_boundary", issue = "131516")]
#[inline]
pub fn is_char_boundary(&self, index: usize) -> bool {
pub const fn is_char_boundary(&self, index: usize) -> bool {
// 0 is always ok.
// Test for 0 explicitly so that it can optimize out the check
// easily and skip reading string data for that case.
@ -195,8 +196,8 @@ impl str {
return true;
}
match self.as_bytes().get(index) {
// For `None` we have two options:
if index >= self.len() {
// For `true` we have two options:
//
// - index == self.len()
// Empty strings are valid, so return true
@ -205,9 +206,9 @@ impl str {
//
// The check is placed exactly here, because it improves generated
// code on higher opt-levels. See PR #84751 for more details.
None => index == self.len(),
Some(&b) => b.is_utf8_char_boundary(),
index == self.len()
} else {
self.as_bytes()[index].is_utf8_char_boundary()
}
}