diff options
| -rw-r--r-- | library/core/src/lib.rs | 2 | ||||
| -rw-r--r-- | library/core/src/str/mod.rs | 35 |
2 files changed, 31 insertions, 6 deletions
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs index e323e88f261..8e735bb96ee 100644 --- a/library/core/src/lib.rs +++ b/library/core/src/lib.rs @@ -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)] diff --git a/library/core/src/str/mod.rs b/library/core/src/str/mod.rs index e5b8e015aea..f5c39af1d53 100644 --- a/library/core/src/str/mod.rs +++ b/library/core/src/str/mod.rs @@ -640,7 +640,8 @@ impl str { #[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 @@ impl 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 @@ impl 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 @@ impl 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 @@ impl 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. |