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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:38 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:12:43 +0000 |
commit | cf94bdc0742c13e2a0cac864c478b8626b266e1b (patch) | |
tree | 044670aa50cc5e2b4229aa0b6b3df6676730c0a6 /library/core/src/slice/mod.rs | |
parent | Adding debian version 1.65.0+dfsg1-2. (diff) | |
download | rustc-cf94bdc0742c13e2a0cac864c478b8626b266e1b.tar.xz rustc-cf94bdc0742c13e2a0cac864c478b8626b266e1b.zip |
Merging upstream version 1.66.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | library/core/src/slice/mod.rs | 132 |
1 files changed, 90 insertions, 42 deletions
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs index 6a7150d29..4f1bb1734 100644 --- a/library/core/src/slice/mod.rs +++ b/library/core/src/slice/mod.rs @@ -9,7 +9,7 @@ use crate::cmp::Ordering::{self, Greater, Less}; use crate::intrinsics::{assert_unsafe_precondition, exact_div}; use crate::marker::Copy; -use crate::mem; +use crate::mem::{self, SizedTypeProperties}; use crate::num::NonZeroUsize; use crate::ops::{Bound, FnMut, OneSidedRange, Range, RangeBounds}; use crate::option::Option; @@ -123,18 +123,11 @@ impl<T> [T] { #[lang = "slice_len_fn"] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_slice_len", since = "1.39.0")] + #[rustc_allow_const_fn_unstable(ptr_metadata)] #[inline] #[must_use] - // SAFETY: const sound because we transmute out the length field as a usize (which it must be) pub const fn len(&self) -> usize { - // FIXME: Replace with `crate::ptr::metadata(self)` when that is const-stable. - // As of this writing this causes a "Const-stable functions can only call other - // const-stable functions" error. - - // SAFETY: Accessing the value from the `PtrRepr` union is safe since *const T - // and PtrComponents<T> have the same memory layouts. Only std can make this - // guarantee. - unsafe { crate::ptr::PtrRepr { const_ptr: self }.components.metadata } + ptr::metadata(self) } /// Returns `true` if the slice has a length of 0. @@ -660,7 +653,10 @@ impl<T> [T] { let ptr = this.as_mut_ptr(); // SAFETY: caller has to guarantee that `a < self.len()` and `b < self.len()` unsafe { - assert_unsafe_precondition!([T](a: usize, b: usize, this: &mut [T]) => a < this.len() && b < this.len()); + assert_unsafe_precondition!( + "slice::swap_unchecked requires that the indices are within the slice", + [T](a: usize, b: usize, this: &mut [T]) => a < this.len() && b < this.len() + ); ptr::swap(ptr.add(a), ptr.add(b)); } } @@ -976,7 +972,10 @@ impl<T> [T] { let this = self; // SAFETY: Caller must guarantee that `N` is nonzero and exactly divides the slice length let new_len = unsafe { - assert_unsafe_precondition!([T](this: &[T], N: usize) => N != 0 && this.len() % N == 0); + assert_unsafe_precondition!( + "slice::as_chunks_unchecked requires `N != 0` and the slice to split exactly into `N`-element chunks", + [T](this: &[T], N: usize) => N != 0 && this.len() % N == 0 + ); exact_div(self.len(), N) }; // SAFETY: We cast a slice of `new_len * N` elements into @@ -1116,7 +1115,10 @@ impl<T> [T] { let this = &*self; // SAFETY: Caller must guarantee that `N` is nonzero and exactly divides the slice length let new_len = unsafe { - assert_unsafe_precondition!([T](this: &[T], N: usize) => N != 0 && this.len() % N == 0); + assert_unsafe_precondition!( + "slice::as_chunks_unchecked_mut requires `N != 0` and the slice to split exactly into `N`-element chunks", + [T](this: &[T], N: usize) => N != 0 && this.len() % N == 0 + ); exact_div(this.len(), N) }; // SAFETY: We cast a slice of `new_len * N` elements into @@ -1580,7 +1582,8 @@ impl<T> [T] { #[inline] #[track_caller] #[must_use] - pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) { + #[rustc_const_unstable(feature = "const_slice_split_at_mut", issue = "101804")] + pub const fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) { assert!(mid <= self.len()); // SAFETY: `[ptr; mid]` and `[mid; len]` are inside `self`, which // fulfills the requirements of `from_raw_parts_mut`. @@ -1679,9 +1682,10 @@ impl<T> [T] { /// assert_eq!(v, [1, 2, 3, 4, 5, 6]); /// ``` #[unstable(feature = "slice_split_at_unchecked", reason = "new API", issue = "76014")] + #[rustc_const_unstable(feature = "const_slice_split_at_mut", issue = "101804")] #[inline] #[must_use] - pub unsafe fn split_at_mut_unchecked(&mut self, mid: usize) -> (&mut [T], &mut [T]) { + pub const unsafe fn split_at_mut_unchecked(&mut self, mid: usize) -> (&mut [T], &mut [T]) { let len = self.len(); let ptr = self.as_mut_ptr(); @@ -1690,7 +1694,10 @@ impl<T> [T] { // `[ptr; mid]` and `[mid; len]` are not overlapping, so returning a mutable reference // is fine. unsafe { - assert_unsafe_precondition!((mid: usize, len: usize) => mid <= len); + assert_unsafe_precondition!( + "slice::split_at_mut_unchecked requires the index to be within the slice", + (mid: usize, len: usize) => mid <= len + ); (from_raw_parts_mut(ptr, mid), from_raw_parts_mut(ptr.add(mid), len - mid)) } } @@ -2074,7 +2081,7 @@ impl<T> [T] { SplitN::new(self.split(pred), n) } - /// Returns an iterator over subslices separated by elements that match + /// Returns an iterator over mutable subslices separated by elements that match /// `pred`, limited to returning at most `n` items. The matched element is /// not contained in the subslices. /// @@ -2357,6 +2364,28 @@ impl<T> [T] { /// assert!(match r { Ok(1..=4) => true, _ => false, }); /// ``` /// + /// If you want to find that whole *range* of matching items, rather than + /// an arbitrary matching one, that can be done using [`partition_point`]: + /// ``` + /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]; + /// + /// let low = s.partition_point(|x| x < &1); + /// assert_eq!(low, 1); + /// let high = s.partition_point(|x| x <= &1); + /// assert_eq!(high, 5); + /// let r = s.binary_search(&1); + /// assert!((low..high).contains(&r.unwrap())); + /// + /// assert!(s[..low].iter().all(|&x| x < 1)); + /// assert!(s[low..high].iter().all(|&x| x == 1)); + /// assert!(s[high..].iter().all(|&x| x > 1)); + /// + /// // For something not found, the "range" of equal items is empty + /// assert_eq!(s.partition_point(|x| x < &11), 9); + /// assert_eq!(s.partition_point(|x| x <= &11), 9); + /// assert_eq!(s.binary_search(&11), Err(9)); + /// ``` + /// /// If you want to insert an item to a sorted vector, while maintaining /// sort order, consider using [`partition_point`]: /// @@ -2424,15 +2453,20 @@ impl<T> [T] { where F: FnMut(&'a T) -> Ordering, { + // INVARIANTS: + // - 0 <= left <= left + size = right <= self.len() + // - f returns Less for everything in self[..left] + // - f returns Greater for everything in self[right..] let mut size = self.len(); let mut left = 0; let mut right = size; while left < right { let mid = left + size / 2; - // SAFETY: the call is made safe by the following invariants: - // - `mid >= 0` - // - `mid < size`: `mid` is limited by `[left; right)` bound. + // SAFETY: the while condition means `size` is strictly positive, so + // `size/2 < size`. Thus `left + size/2 < left + size`, which + // coupled with the `left + size <= self.len()` invariant means + // we have `left + size/2 < self.len()`, and this is in-bounds. let cmp = f(unsafe { self.get_unchecked(mid) }); // The reason why we use if/else control flow rather than match @@ -2450,6 +2484,10 @@ impl<T> [T] { size = right - left; } + + // SAFETY: directly true from the overall invariant. + // Note that this is `<=`, unlike the assume in the `Ok` path. + unsafe { crate::intrinsics::assume(left <= self.len()) }; Err(left) } @@ -2540,7 +2578,7 @@ impl<T> [T] { where T: Ord, { - sort::quicksort(self, |a, b| a.lt(b)); + sort::quicksort(self, T::lt); } /// Sorts the slice with a comparator function, but might not preserve the order of equal @@ -2643,9 +2681,10 @@ impl<T> [T] { /// less than or equal to any value at a position `j > index`. Additionally, this reordering is /// unstable (i.e. any number of equal elements may end up at position `index`), in-place /// (i.e. does not allocate), and *O*(*n*) worst-case. This function is also/ known as "kth - /// element" in other libraries. It returns a triplet of the following values: all elements less - /// than the one at the given index, the value at the given index, and all elements greater than - /// the one at the given index. + /// element" in other libraries. It returns a triplet of the following from the reordered slice: + /// the subslice prior to `index`, the element at `index`, and the subslice after `index`; + /// accordingly, the values in those two subslices will respectively all be less-than-or-equal-to + /// and greater-than-or-equal-to the value of the element at `index`. /// /// # Current implementation /// @@ -2679,8 +2718,7 @@ impl<T> [T] { where T: Ord, { - let mut f = |a: &T, b: &T| a.lt(b); - sort::partition_at_index(self, index, &mut f) + sort::partition_at_index(self, index, T::lt) } /// Reorder the slice with a comparator function such that the element at `index` is at its @@ -2690,10 +2728,11 @@ impl<T> [T] { /// less than or equal to any value at a position `j > index` using the comparator function. /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at /// position `index`), in-place (i.e. does not allocate), and *O*(*n*) worst-case. This function - /// is also known as "kth element" in other libraries. It returns a triplet of the following - /// values: all elements less than the one at the given index, the value at the given index, - /// and all elements greater than the one at the given index, using the provided comparator - /// function. + /// is also known as "kth element" in other libraries. It returns a triplet of the following from + /// the slice reordered according to the provided comparator function: the subslice prior to + /// `index`, the element at `index`, and the subslice after `index`; accordingly, the values in + /// those two subslices will respectively all be less-than-or-equal-to and greater-than-or-equal-to + /// the value of the element at `index`. /// /// # Current implementation /// @@ -2731,8 +2770,7 @@ impl<T> [T] { where F: FnMut(&T, &T) -> Ordering, { - let mut f = |a: &T, b: &T| compare(a, b) == Less; - sort::partition_at_index(self, index, &mut f) + sort::partition_at_index(self, index, |a: &T, b: &T| compare(a, b) == Less) } /// Reorder the slice with a key extraction function such that the element at `index` is at its @@ -2742,10 +2780,11 @@ impl<T> [T] { /// less than or equal to any value at a position `j > index` using the key extraction function. /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at /// position `index`), in-place (i.e. does not allocate), and *O*(*n*) worst-case. This function - /// is also known as "kth element" in other libraries. It returns a triplet of the following - /// values: all elements less than the one at the given index, the value at the given index, and - /// all elements greater than the one at the given index, using the provided key extraction - /// function. + /// is also known as "kth element" in other libraries. It returns a triplet of the following from + /// the slice reordered according to the provided key extraction function: the subslice prior to + /// `index`, the element at `index`, and the subslice after `index`; accordingly, the values in + /// those two subslices will respectively all be less-than-or-equal-to and greater-than-or-equal-to + /// the value of the element at `index`. /// /// # Current implementation /// @@ -2784,8 +2823,7 @@ impl<T> [T] { F: FnMut(&T) -> K, K: Ord, { - let mut g = |a: &T, b: &T| f(a).lt(&f(b)); - sort::partition_at_index(self, index, &mut g) + sort::partition_at_index(self, index, |a: &T, b: &T| f(a).lt(&f(b))) } /// Moves all consecutive repeated elements to the end of the slice according to the @@ -3459,7 +3497,7 @@ impl<T> [T] { #[must_use] pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T]) { // Note that most of this function will be constant-evaluated, - if mem::size_of::<U>() == 0 || mem::size_of::<T>() == 0 { + if U::IS_ZST || T::IS_ZST { // handle ZSTs specially, which is – don't handle them at all. return (self, &[], &[]); } @@ -3520,7 +3558,7 @@ impl<T> [T] { #[must_use] pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T]) { // Note that most of this function will be constant-evaluated, - if mem::size_of::<U>() == 0 || mem::size_of::<T>() == 0 { + if U::IS_ZST || T::IS_ZST { // handle ZSTs specially, which is – don't handle them at all. return (self, &mut [], &mut []); } @@ -3776,6 +3814,16 @@ impl<T> [T] { /// assert!(v[i..].iter().all(|&x| !(x < 5))); /// ``` /// + /// If all elements of the slice match the predicate, including if the slice + /// is empty, then the length of the slice will be returned: + /// + /// ``` + /// let a = [2, 4, 8]; + /// assert_eq!(a.partition_point(|x| x < &100), a.len()); + /// let a: [i32; 0] = []; + /// assert_eq!(a.partition_point(|x| x < &100), 0); + /// ``` + /// /// If you want to insert an item to a sorted vector, while maintaining /// sort order: /// @@ -4066,7 +4114,7 @@ impl<T, const N: usize> [[T; N]] { /// ``` #[unstable(feature = "slice_flatten", issue = "95629")] pub fn flatten(&self) -> &[T] { - let len = if crate::mem::size_of::<T>() == 0 { + let len = if T::IS_ZST { self.len().checked_mul(N).expect("slice len overflow") } else { // SAFETY: `self.len() * N` cannot overflow because `self` is @@ -4104,7 +4152,7 @@ impl<T, const N: usize> [[T; N]] { /// ``` #[unstable(feature = "slice_flatten", issue = "95629")] pub fn flatten_mut(&mut self) -> &mut [T] { - let len = if crate::mem::size_of::<T>() == 0 { + let len = if T::IS_ZST { self.len().checked_mul(N).expect("slice len overflow") } else { // SAFETY: `self.len() * N` cannot overflow because `self` is |