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const fn str::split_at*

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This commit is contained in:
Zachary S 2024-10-23 14:22:56 -05:00
parent 8ee548fcf0
commit aa493d0b60
2 changed files with 31 additions and 6 deletions
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2
library/core/src/lib.rs
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@ -196,7 +196,9 @@
#![feature(cfg_target_has_atomic_equal_alignment)]
#![feature(cfg_ub_checks)]
#![feature(const_for)]
#![feature(const_is_char_boundary)]
#![feature(const_precise_live_drops)]
#![feature(const_str_split_at)]
#![feature(decl_macro)]
#![feature(deprecated_suggestion)]
#![feature(doc_cfg)]

35
library/core/src/str/mod.rs
View File

@ -640,7 +640,8 @@ pub unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut s
#[inline]
#[must_use]
#[stable(feature = "str_split_at", since = "1.4.0")]
pub fn split_at(&self, mid: usize) -> (&str, &str) {
#[rustc_const_unstable(feature = "const_str_split_at", issue = "131518")]
pub const fn split_at(&self, mid: usize) -> (&str, &str) {
match self.split_at_checked(mid) {
None => slice_error_fail(self, 0, mid),
Some(pair) => pair,
@ -680,7 +681,8 @@ pub fn split_at(&self, mid: usize) -> (&str, &str) {
#[inline]
#[must_use]
#[stable(feature = "str_split_at", since = "1.4.0")]
pub fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str) {
#[rustc_const_unstable(feature = "const_str_split_at", issue = "131518")]
pub const fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str) {
// is_char_boundary checks that the index is in [0, .len()]
if self.is_char_boundary(mid) {
// SAFETY: just checked that `mid` is on a char boundary.
@ -719,11 +721,12 @@ pub fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str) {
#[inline]
#[must_use]
#[stable(feature = "split_at_checked", since = "1.80.0")]
pub fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)> {
#[rustc_const_unstable(feature = "const_str_split_at", issue = "131518")]
pub const fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)> {
// is_char_boundary checks that the index is in [0, .len()]
if self.is_char_boundary(mid) {
// SAFETY: just checked that `mid` is on a char boundary.
Some(unsafe { (self.get_unchecked(0..mid), self.get_unchecked(mid..self.len())) })
Some(unsafe { self.split_at_unchecked(mid) })
} else {
None
}
@ -759,7 +762,9 @@ pub fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)> {
#[inline]
#[must_use]
#[stable(feature = "split_at_checked", since = "1.80.0")]
pub fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut str, &mut str)> {
#[rustc_const_unstable(feature = "const_str_split_at", issue = "131518")]
#[rustc_allow_const_fn_unstable(const_is_char_boundary)]
pub const fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut str, &mut str)> {
// is_char_boundary checks that the index is in [0, .len()]
if self.is_char_boundary(mid) {
// SAFETY: just checked that `mid` is on a char boundary.
@ -775,7 +780,25 @@ pub fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut str, &mut str
///
/// The caller must ensure that `mid` is a valid byte offset from the start
/// of the string and falls on the boundary of a UTF-8 code point.
unsafe fn split_at_mut_unchecked(&mut self, mid: usize) -> (&mut str, &mut str) {
const unsafe fn split_at_unchecked(&self, mid: usize) -> (&str, &str) {
let len = self.len();
let ptr = self.as_ptr();
// SAFETY: caller guarantees `mid` is on a char boundary.
unsafe {
(
from_utf8_unchecked(slice::from_raw_parts(ptr, mid)),
from_utf8_unchecked(slice::from_raw_parts(ptr.add(mid), len - mid)),
)
}
}
/// Divides one string slice into two at an index.
///
/// # Safety
///
/// The caller must ensure that `mid` is a valid byte offset from the start
/// of the string and falls on the boundary of a UTF-8 code point.
const unsafe fn split_at_mut_unchecked(&mut self, mid: usize) -> (&mut str, &mut str) {
let len = self.len();
let ptr = self.as_mut_ptr();
// SAFETY: caller guarantees `mid` is on a char boundary.