diff options
| -rw-r--r-- | library/core/src/slice/index.rs | 112 | ||||
| -rw-r--r-- | library/core/tests/slice.rs | 43 |
2 files changed, 155 insertions, 0 deletions
diff --git a/library/core/src/slice/index.rs b/library/core/src/slice/index.rs index c92b37b14be..f7224303549 100644 --- a/library/core/src/slice/index.rs +++ b/library/core/src/slice/index.rs @@ -81,6 +81,8 @@ mod private_slice_index { impl Sealed for ops::RangeInclusive<usize> {} #[stable(feature = "slice_get_slice", since = "1.28.0")] impl Sealed for ops::RangeToInclusive<usize> {} + #[stable(feature = "slice_index_with_ops_bound_pair", since = "1.53.0")] + impl Sealed for (ops::Bound<usize>, ops::Bound<usize>) {} } /// A helper trait used for indexing operations. @@ -546,3 +548,113 @@ where ops::Range { start, end } } + +/// Convert pair of `ops::Bound`s into `ops::Range` without performing any bounds checking and (in debug) overflow checking +fn into_range_unchecked( + len: usize, + (start, end): (ops::Bound<usize>, ops::Bound<usize>), +) -> ops::Range<usize> { + use ops::Bound; + let start = match start { + Bound::Included(i) => i, + Bound::Excluded(i) => i + 1, + Bound::Unbounded => 0, + }; + let end = match end { + Bound::Included(i) => i + 1, + Bound::Excluded(i) => i, + Bound::Unbounded => len, + }; + start..end +} + +/// Convert pair of `ops::Bound`s into `ops::Range`. +/// Returns `None` on overflowing indices. +fn into_range( + len: usize, + (start, end): (ops::Bound<usize>, ops::Bound<usize>), +) -> Option<ops::Range<usize>> { + use ops::Bound; + let start = match start { + Bound::Included(start) => start, + Bound::Excluded(start) => start.checked_add(1)?, + Bound::Unbounded => 0, + }; + + let end = match end { + Bound::Included(end) => end.checked_add(1)?, + Bound::Excluded(end) => end, + Bound::Unbounded => len, + }; + + // Don't bother with checking `start < end` and `end <= len` + // since these checks are handled by `Range` impls + + Some(start..end) +} + +/// Convert pair of `ops::Bound`s into `ops::Range`. +/// Panics on overflowing indices. +fn into_slice_range( + len: usize, + (start, end): (ops::Bound<usize>, ops::Bound<usize>), +) -> ops::Range<usize> { + use ops::Bound; + let start = match start { + Bound::Included(start) => start, + Bound::Excluded(start) => { + start.checked_add(1).unwrap_or_else(|| slice_start_index_overflow_fail()) + } + Bound::Unbounded => 0, + }; + + let end = match end { + Bound::Included(end) => { + end.checked_add(1).unwrap_or_else(|| slice_end_index_overflow_fail()) + } + Bound::Excluded(end) => end, + Bound::Unbounded => len, + }; + + // Don't bother with checking `start < end` and `end <= len` + // since these checks are handled by `Range` impls + + start..end +} + +#[stable(feature = "slice_index_with_ops_bound_pair", since = "1.53.0")] +unsafe impl<T> SliceIndex<[T]> for (ops::Bound<usize>, ops::Bound<usize>) { + type Output = [T]; + + #[inline] + fn get(self, slice: &[T]) -> Option<&Self::Output> { + into_range(slice.len(), self)?.get(slice) + } + + #[inline] + fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> { + into_range(slice.len(), self)?.get_mut(slice) + } + + #[inline] + unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked`. + unsafe { into_range_unchecked(slice.len(), self).get_unchecked(slice) } + } + + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`. + unsafe { into_range_unchecked(slice.len(), self).get_unchecked_mut(slice) } + } + + #[inline] + fn index(self, slice: &[T]) -> &Self::Output { + into_slice_range(slice.len(), self).index(slice) + } + + #[inline] + fn index_mut(self, slice: &mut [T]) -> &mut Self::Output { + into_slice_range(slice.len(), self).index_mut(slice) + } +} diff --git a/library/core/tests/slice.rs b/library/core/tests/slice.rs index 7e198631cc7..3a98cd9d2ee 100644 --- a/library/core/tests/slice.rs +++ b/library/core/tests/slice.rs @@ -1280,6 +1280,9 @@ mod slice_index { } )*) => {$( mod $case_name { + #[allow(unused_imports)] + use core::ops::Bound; + #[test] fn pass() { let mut v = $data; @@ -1376,6 +1379,24 @@ mod slice_index { bad: data[7..=6]; message: "out of range"; } + + in mod boundpair_len { + data: [0, 1, 2, 3, 4, 5]; + + good: data[(Bound::Included(6), Bound::Unbounded)] == []; + good: data[(Bound::Unbounded, Bound::Included(5))] == [0, 1, 2, 3, 4, 5]; + good: data[(Bound::Unbounded, Bound::Excluded(6))] == [0, 1, 2, 3, 4, 5]; + good: data[(Bound::Included(0), Bound::Included(5))] == [0, 1, 2, 3, 4, 5]; + good: data[(Bound::Included(0), Bound::Excluded(6))] == [0, 1, 2, 3, 4, 5]; + good: data[(Bound::Included(2), Bound::Excluded(4))] == [2, 3]; + good: data[(Bound::Excluded(1), Bound::Included(4))] == [2, 3, 4]; + good: data[(Bound::Excluded(5), Bound::Excluded(6))] == []; + good: data[(Bound::Included(6), Bound::Excluded(6))] == []; + good: data[(Bound::Excluded(5), Bound::Included(5))] == []; + good: data[(Bound::Included(6), Bound::Included(5))] == []; + bad: data[(Bound::Unbounded, Bound::Included(6))]; + message: "out of range"; + } } panic_cases! { @@ -1416,6 +1437,14 @@ mod slice_index { bad: data[4..=2]; message: "but ends at"; } + + in mod boundpair_neg_width { + data: [0, 1, 2, 3, 4, 5]; + + good: data[(Bound::Included(4), Bound::Excluded(4))] == []; + bad: data[(Bound::Included(4), Bound::Excluded(3))]; + message: "but ends at"; + } } panic_cases! { @@ -1434,6 +1463,20 @@ mod slice_index { bad: data[..= usize::MAX]; message: "maximum usize"; } + + in mod boundpair_overflow_end { + data: [0; 1]; + + bad: data[(Bound::Unbounded, Bound::Included(usize::MAX))]; + message: "maximum usize"; + } + + in mod boundpair_overflow_start { + data: [0; 1]; + + bad: data[(Bound::Excluded(usize::MAX), Bound::Unbounded)]; + message: "maximum usize"; + } } // panic_cases! } |