diff options
Diffstat (limited to 'library/core/src/str/traits.rs')
| -rw-r--r-- | library/core/src/str/traits.rs | 72 |
1 files changed, 41 insertions, 31 deletions
diff --git a/library/core/src/str/traits.rs b/library/core/src/str/traits.rs index 68f62ce8b..41c097b55 100644 --- a/library/core/src/str/traits.rs +++ b/library/core/src/str/traits.rs @@ -1,6 +1,7 @@ //! Trait implementations for `str`. use crate::cmp::Ordering; +use crate::intrinsics::assert_unsafe_precondition; use crate::ops; use crate::ptr; use crate::slice::SliceIndex; @@ -194,7 +195,21 @@ unsafe impl const SliceIndex<str> for ops::Range<usize> { let slice = slice as *const [u8]; // SAFETY: the caller guarantees that `self` is in bounds of `slice` // which satisfies all the conditions for `add`. - let ptr = unsafe { slice.as_ptr().add(self.start) }; + let ptr = unsafe { + let this = ops::Range { ..self }; + assert_unsafe_precondition!( + "str::get_unchecked requires that the range is within the string slice", + (this: ops::Range<usize>, slice: *const [u8]) => + // We'd like to check that the bounds are on char boundaries, + // but there's not really a way to do so without reading + // behind the pointer, which has aliasing implications. + // It's also not possible to move this check up to + // `str::get_unchecked` without adding a special function + // to `SliceIndex` just for this. + this.end >= this.start && this.end <= slice.len() + ); + slice.as_ptr().add(self.start) + }; let len = self.end - self.start; ptr::slice_from_raw_parts(ptr, len) as *const str } @@ -202,7 +217,15 @@ unsafe impl const SliceIndex<str> for ops::Range<usize> { unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { let slice = slice as *mut [u8]; // SAFETY: see comments for `get_unchecked`. - let ptr = unsafe { slice.as_mut_ptr().add(self.start) }; + let ptr = unsafe { + let this = ops::Range { ..self }; + assert_unsafe_precondition!( + "str::get_unchecked_mut requires that the range is within the string slice", + (this: ops::Range<usize>, slice: *mut [u8]) => + this.end >= this.start && this.end <= slice.len() + ); + slice.as_mut_ptr().add(self.start) + }; let len = self.end - self.start; ptr::slice_from_raw_parts_mut(ptr, len) as *mut str } @@ -272,15 +295,13 @@ unsafe impl const SliceIndex<str> for ops::RangeTo<usize> { } #[inline] unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { - let slice = slice as *const [u8]; - let ptr = slice.as_ptr(); - ptr::slice_from_raw_parts(ptr, self.end) as *const str + // SAFETY: the caller has to uphold the safety contract for `get_unchecked`. + unsafe { (0..self.end).get_unchecked(slice) } } #[inline] unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { - let slice = slice as *mut [u8]; - let ptr = slice.as_mut_ptr(); - ptr::slice_from_raw_parts_mut(ptr, self.end) as *mut str + // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`. + unsafe { (0..self.end).get_unchecked_mut(slice) } } #[inline] fn index(self, slice: &str) -> &Self::Output { @@ -343,20 +364,15 @@ unsafe impl const SliceIndex<str> for ops::RangeFrom<usize> { } #[inline] unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { - let slice = slice as *const [u8]; - // SAFETY: the caller guarantees that `self` is in bounds of `slice` - // which satisfies all the conditions for `add`. - let ptr = unsafe { slice.as_ptr().add(self.start) }; - let len = slice.len() - self.start; - ptr::slice_from_raw_parts(ptr, len) as *const str + let len = (slice as *const [u8]).len(); + // SAFETY: the caller has to uphold the safety contract for `get_unchecked`. + unsafe { (self.start..len).get_unchecked(slice) } } #[inline] unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { - let slice = slice as *mut [u8]; - // SAFETY: identical to `get_unchecked`. - let ptr = unsafe { slice.as_mut_ptr().add(self.start) }; - let len = slice.len() - self.start; - ptr::slice_from_raw_parts_mut(ptr, len) as *mut str + let len = (slice as *mut [u8]).len(); + // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`. + unsafe { (self.start..len).get_unchecked_mut(slice) } } #[inline] fn index(self, slice: &str) -> &Self::Output { @@ -452,35 +468,29 @@ unsafe impl const SliceIndex<str> for ops::RangeToInclusive<usize> { type Output = str; #[inline] fn get(self, slice: &str) -> Option<&Self::Output> { - if self.end == usize::MAX { None } else { (..self.end + 1).get(slice) } + (0..=self.end).get(slice) } #[inline] fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { - if self.end == usize::MAX { None } else { (..self.end + 1).get_mut(slice) } + (0..=self.end).get_mut(slice) } #[inline] unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { // SAFETY: the caller must uphold the safety contract for `get_unchecked`. - unsafe { (..self.end + 1).get_unchecked(slice) } + unsafe { (0..=self.end).get_unchecked(slice) } } #[inline] unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`. - unsafe { (..self.end + 1).get_unchecked_mut(slice) } + unsafe { (0..=self.end).get_unchecked_mut(slice) } } #[inline] fn index(self, slice: &str) -> &Self::Output { - if self.end == usize::MAX { - str_index_overflow_fail(); - } - (..self.end + 1).index(slice) + (0..=self.end).index(slice) } #[inline] fn index_mut(self, slice: &mut str) -> &mut Self::Output { - if self.end == usize::MAX { - str_index_overflow_fail(); - } - (..self.end + 1).index_mut(slice) + (0..=self.end).index_mut(slice) } } |