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Diffstat (limited to 'rust/alloc/slice.rs')
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diff --git a/rust/alloc/slice.rs b/rust/alloc/slice.rs deleted file mode 100644 index e444e97fa145..000000000000 --- a/rust/alloc/slice.rs +++ /dev/null @@ -1,1204 +0,0 @@ -// SPDX-License-Identifier: Apache-2.0 OR MIT - -//! A dynamically-sized view into a contiguous sequence, `[T]`. -//! -//! *[See also the slice primitive type](slice).* -//! -//! Slices are a view into a block of memory represented as a pointer and a -//! length. -//! -//! ``` -//! // slicing a Vec -//! let vec = vec![1, 2, 3]; -//! let int_slice = &vec[..]; -//! // coercing an array to a slice -//! let str_slice: &[&str] = &["one", "two", "three"]; -//! ``` -//! -//! Slices are either mutable or shared. The shared slice type is `&[T]`, -//! while the mutable slice type is `&mut [T]`, where `T` represents the element -//! type. For example, you can mutate the block of memory that a mutable slice -//! points to: -//! -//! ``` -//! let x = &mut [1, 2, 3]; -//! x[1] = 7; -//! assert_eq!(x, &[1, 7, 3]); -//! ``` -//! -//! Here are some of the things this module contains: -//! -//! ## Structs -//! -//! There are several structs that are useful for slices, such as [`Iter`], which -//! represents iteration over a slice. -//! -//! ## Trait Implementations -//! -//! There are several implementations of common traits for slices. Some examples -//! include: -//! -//! * [`Clone`] -//! * [`Eq`], [`Ord`] - for slices whose element type are [`Eq`] or [`Ord`]. -//! * [`Hash`] - for slices whose element type is [`Hash`]. -//! -//! ## Iteration -//! -//! The slices implement `IntoIterator`. The iterator yields references to the -//! slice elements. -//! -//! ``` -//! let numbers = &[0, 1, 2]; -//! for n in numbers { -//! println!("{n} is a number!"); -//! } -//! ``` -//! -//! The mutable slice yields mutable references to the elements: -//! -//! ``` -//! let mut scores = [7, 8, 9]; -//! for score in &mut scores[..] { -//! *score += 1; -//! } -//! ``` -//! -//! This iterator yields mutable references to the slice's elements, so while -//! the element type of the slice is `i32`, the element type of the iterator is -//! `&mut i32`. -//! -//! * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default -//! iterators. -//! * Further methods that return iterators are [`.split`], [`.splitn`], -//! [`.chunks`], [`.windows`] and more. -//! -//! [`Hash`]: core::hash::Hash -//! [`.iter`]: slice::iter -//! [`.iter_mut`]: slice::iter_mut -//! [`.split`]: slice::split -//! [`.splitn`]: slice::splitn -//! [`.chunks`]: slice::chunks -//! [`.windows`]: slice::windows -#![stable(feature = "rust1", since = "1.0.0")] -// Many of the usings in this module are only used in the test configuration. -// It's cleaner to just turn off the unused_imports warning than to fix them. -#![cfg_attr(test, allow(unused_imports, dead_code))] - -use core::borrow::{Borrow, BorrowMut}; -#[cfg(not(no_global_oom_handling))] -use core::cmp::Ordering::{self, Less}; -#[cfg(not(no_global_oom_handling))] -use core::mem; -#[cfg(not(no_global_oom_handling))] -use core::mem::size_of; -#[cfg(not(no_global_oom_handling))] -use core::ptr; - -use crate::alloc::Allocator; -#[cfg(not(no_global_oom_handling))] -use crate::alloc::Global; -#[cfg(not(no_global_oom_handling))] -use crate::borrow::ToOwned; -use crate::boxed::Box; -use crate::vec::Vec; - -#[unstable(feature = "slice_range", issue = "76393")] -pub use core::slice::range; -#[unstable(feature = "array_chunks", issue = "74985")] -pub use core::slice::ArrayChunks; -#[unstable(feature = "array_chunks", issue = "74985")] -pub use core::slice::ArrayChunksMut; -#[unstable(feature = "array_windows", issue = "75027")] -pub use core::slice::ArrayWindows; -#[stable(feature = "inherent_ascii_escape", since = "1.60.0")] -pub use core::slice::EscapeAscii; -#[stable(feature = "slice_get_slice", since = "1.28.0")] -pub use core::slice::SliceIndex; -#[stable(feature = "from_ref", since = "1.28.0")] -pub use core::slice::{from_mut, from_ref}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use core::slice::{from_raw_parts, from_raw_parts_mut}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use core::slice::{Chunks, Windows}; -#[stable(feature = "chunks_exact", since = "1.31.0")] -pub use core::slice::{ChunksExact, ChunksExactMut}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use core::slice::{ChunksMut, Split, SplitMut}; -#[unstable(feature = "slice_group_by", issue = "80552")] -pub use core::slice::{GroupBy, GroupByMut}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use core::slice::{Iter, IterMut}; -#[stable(feature = "rchunks", since = "1.31.0")] -pub use core::slice::{RChunks, RChunksExact, RChunksExactMut, RChunksMut}; -#[stable(feature = "slice_rsplit", since = "1.27.0")] -pub use core::slice::{RSplit, RSplitMut}; -#[stable(feature = "rust1", since = "1.0.0")] -pub use core::slice::{RSplitN, RSplitNMut, SplitN, SplitNMut}; -#[stable(feature = "split_inclusive", since = "1.51.0")] -pub use core::slice::{SplitInclusive, SplitInclusiveMut}; - -//////////////////////////////////////////////////////////////////////////////// -// Basic slice extension methods -//////////////////////////////////////////////////////////////////////////////// - -// HACK(japaric) needed for the implementation of `vec!` macro during testing -// N.B., see the `hack` module in this file for more details. -#[cfg(test)] -pub use hack::into_vec; - -// HACK(japaric) needed for the implementation of `Vec::clone` during testing -// N.B., see the `hack` module in this file for more details. -#[cfg(test)] -pub use hack::to_vec; - -// HACK(japaric): With cfg(test) `impl [T]` is not available, these three -// functions are actually methods that are in `impl [T]` but not in -// `core::slice::SliceExt` - we need to supply these functions for the -// `test_permutations` test -pub(crate) mod hack { - use core::alloc::Allocator; - - use crate::boxed::Box; - use crate::vec::Vec; - - // We shouldn't add inline attribute to this since this is used in - // `vec!` macro mostly and causes perf regression. See #71204 for - // discussion and perf results. - pub fn into_vec<T, A: Allocator>(b: Box<[T], A>) -> Vec<T, A> { - unsafe { - let len = b.len(); - let (b, alloc) = Box::into_raw_with_allocator(b); - Vec::from_raw_parts_in(b as *mut T, len, len, alloc) - } - } - - #[cfg(not(no_global_oom_handling))] - #[inline] - pub fn to_vec<T: ConvertVec, A: Allocator>(s: &[T], alloc: A) -> Vec<T, A> { - T::to_vec(s, alloc) - } - - #[cfg(not(no_global_oom_handling))] - pub trait ConvertVec { - fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A> - where - Self: Sized; - } - - #[cfg(not(no_global_oom_handling))] - impl<T: Clone> ConvertVec for T { - #[inline] - default fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A> { - struct DropGuard<'a, T, A: Allocator> { - vec: &'a mut Vec<T, A>, - num_init: usize, - } - impl<'a, T, A: Allocator> Drop for DropGuard<'a, T, A> { - #[inline] - fn drop(&mut self) { - // SAFETY: - // items were marked initialized in the loop below - unsafe { - self.vec.set_len(self.num_init); - } - } - } - let mut vec = Vec::with_capacity_in(s.len(), alloc); - let mut guard = DropGuard { vec: &mut vec, num_init: 0 }; - let slots = guard.vec.spare_capacity_mut(); - // .take(slots.len()) is necessary for LLVM to remove bounds checks - // and has better codegen than zip. - for (i, b) in s.iter().enumerate().take(slots.len()) { - guard.num_init = i; - slots[i].write(b.clone()); - } - core::mem::forget(guard); - // SAFETY: - // the vec was allocated and initialized above to at least this length. - unsafe { - vec.set_len(s.len()); - } - vec - } - } - - #[cfg(not(no_global_oom_handling))] - impl<T: Copy> ConvertVec for T { - #[inline] - fn to_vec<A: Allocator>(s: &[Self], alloc: A) -> Vec<Self, A> { - let mut v = Vec::with_capacity_in(s.len(), alloc); - // SAFETY: - // allocated above with the capacity of `s`, and initialize to `s.len()` in - // ptr::copy_to_non_overlapping below. - unsafe { - s.as_ptr().copy_to_nonoverlapping(v.as_mut_ptr(), s.len()); - v.set_len(s.len()); - } - v - } - } -} - -#[cfg(not(test))] -impl<T> [T] { - /// Sorts the slice. - /// - /// This sort is stable (i.e., does not reorder equal elements) and *O*(*n* \* log(*n*)) worst-case. - /// - /// When applicable, unstable sorting is preferred because it is generally faster than stable - /// sorting and it doesn't allocate auxiliary memory. - /// See [`sort_unstable`](slice::sort_unstable). - /// - /// # Current implementation - /// - /// The current algorithm is an adaptive, iterative merge sort inspired by - /// [timsort](https://en.wikipedia.org/wiki/Timsort). - /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of - /// two or more sorted sequences concatenated one after another. - /// - /// Also, it allocates temporary storage half the size of `self`, but for short slices a - /// non-allocating insertion sort is used instead. - /// - /// # Examples - /// - /// ``` - /// let mut v = [-5, 4, 1, -3, 2]; - /// - /// v.sort(); - /// assert!(v == [-5, -3, 1, 2, 4]); - /// ``` - #[cfg(not(no_global_oom_handling))] - #[rustc_allow_incoherent_impl] - #[stable(feature = "rust1", since = "1.0.0")] - #[inline] - pub fn sort(&mut self) - where - T: Ord, - { - merge_sort(self, |a, b| a.lt(b)); - } - - /// Sorts the slice with a comparator function. - /// - /// This sort is stable (i.e., does not reorder equal elements) and *O*(*n* \* log(*n*)) worst-case. - /// - /// The comparator function must define a total ordering for the elements in the slice. If - /// the ordering is not total, the order of the elements is unspecified. An order is a - /// total order if it is (for all `a`, `b` and `c`): - /// - /// * total and antisymmetric: exactly one of `a < b`, `a == b` or `a > b` is true, and - /// * transitive, `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`. - /// - /// For example, while [`f64`] doesn't implement [`Ord`] because `NaN != NaN`, we can use - /// `partial_cmp` as our sort function when we know the slice doesn't contain a `NaN`. - /// - /// ``` - /// let mut floats = [5f64, 4.0, 1.0, 3.0, 2.0]; - /// floats.sort_by(|a, b| a.partial_cmp(b).unwrap()); - /// assert_eq!(floats, [1.0, 2.0, 3.0, 4.0, 5.0]); - /// ``` - /// - /// When applicable, unstable sorting is preferred because it is generally faster than stable - /// sorting and it doesn't allocate auxiliary memory. - /// See [`sort_unstable_by`](slice::sort_unstable_by). - /// - /// # Current implementation - /// - /// The current algorithm is an adaptive, iterative merge sort inspired by - /// [timsort](https://en.wikipedia.org/wiki/Timsort). - /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of - /// two or more sorted sequences concatenated one after another. - /// - /// Also, it allocates temporary storage half the size of `self`, but for short slices a - /// non-allocating insertion sort is used instead. - /// - /// # Examples - /// - /// ``` - /// let mut v = [5, 4, 1, 3, 2]; - /// v.sort_by(|a, b| a.cmp(b)); - /// assert!(v == [1, 2, 3, 4, 5]); - /// - /// // reverse sorting - /// v.sort_by(|a, b| b.cmp(a)); - /// assert!(v == [5, 4, 3, 2, 1]); - /// ``` - #[cfg(not(no_global_oom_handling))] - #[rustc_allow_incoherent_impl] - #[stable(feature = "rust1", since = "1.0.0")] - #[inline] - pub fn sort_by<F>(&mut self, mut compare: F) - where - F: FnMut(&T, &T) -> Ordering, - { - merge_sort(self, |a, b| compare(a, b) == Less); - } - - /// Sorts the slice with a key extraction function. - /// - /// This sort is stable (i.e., does not reorder equal elements) and *O*(*m* \* *n* \* log(*n*)) - /// worst-case, where the key function is *O*(*m*). - /// - /// For expensive key functions (e.g. functions that are not simple property accesses or - /// basic operations), [`sort_by_cached_key`](slice::sort_by_cached_key) is likely to be - /// significantly faster, as it does not recompute element keys. - /// - /// When applicable, unstable sorting is preferred because it is generally faster than stable - /// sorting and it doesn't allocate auxiliary memory. - /// See [`sort_unstable_by_key`](slice::sort_unstable_by_key). - /// - /// # Current implementation - /// - /// The current algorithm is an adaptive, iterative merge sort inspired by - /// [timsort](https://en.wikipedia.org/wiki/Timsort). - /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of - /// two or more sorted sequences concatenated one after another. - /// - /// Also, it allocates temporary storage half the size of `self`, but for short slices a - /// non-allocating insertion sort is used instead. - /// - /// # Examples - /// - /// ``` - /// let mut v = [-5i32, 4, 1, -3, 2]; - /// - /// v.sort_by_key(|k| k.abs()); - /// assert!(v == [1, 2, -3, 4, -5]); - /// ``` - #[cfg(not(no_global_oom_handling))] - #[rustc_allow_incoherent_impl] - #[stable(feature = "slice_sort_by_key", since = "1.7.0")] - #[inline] - pub fn sort_by_key<K, F>(&mut self, mut f: F) - where - F: FnMut(&T) -> K, - K: Ord, - { - merge_sort(self, |a, b| f(a).lt(&f(b))); - } - - /// Sorts the slice with a key extraction function. - /// - /// During sorting, the key function is called at most once per element, by using - /// temporary storage to remember the results of key evaluation. - /// The order of calls to the key function is unspecified and may change in future versions - /// of the standard library. - /// - /// This sort is stable (i.e., does not reorder equal elements) and *O*(*m* \* *n* + *n* \* log(*n*)) - /// worst-case, where the key function is *O*(*m*). - /// - /// For simple key functions (e.g., functions that are property accesses or - /// basic operations), [`sort_by_key`](slice::sort_by_key) is likely to be - /// faster. - /// - /// # Current implementation - /// - /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters, - /// which combines the fast average case of randomized quicksort with the fast worst case of - /// heapsort, while achieving linear time on slices with certain patterns. It uses some - /// randomization to avoid degenerate cases, but with a fixed seed to always provide - /// deterministic behavior. - /// - /// In the worst case, the algorithm allocates temporary storage in a `Vec<(K, usize)>` the - /// length of the slice. - /// - /// # Examples - /// - /// ``` - /// let mut v = [-5i32, 4, 32, -3, 2]; - /// - /// v.sort_by_cached_key(|k| k.to_string()); - /// assert!(v == [-3, -5, 2, 32, 4]); - /// ``` - /// - /// [pdqsort]: https://github.com/orlp/pdqsort - #[cfg(not(no_global_oom_handling))] - #[rustc_allow_incoherent_impl] - #[stable(feature = "slice_sort_by_cached_key", since = "1.34.0")] - #[inline] - pub fn sort_by_cached_key<K, F>(&mut self, f: F) - where - F: FnMut(&T) -> K, - K: Ord, - { - // Helper macro for indexing our vector by the smallest possible type, to reduce allocation. - macro_rules! sort_by_key { - ($t:ty, $slice:ident, $f:ident) => {{ - let mut indices: Vec<_> = - $slice.iter().map($f).enumerate().map(|(i, k)| (k, i as $t)).collect(); - // The elements of `indices` are unique, as they are indexed, so any sort will be - // stable with respect to the original slice. We use `sort_unstable` here because - // it requires less memory allocation. - indices.sort_unstable(); - for i in 0..$slice.len() { - let mut index = indices[i].1; - while (index as usize) < i { - index = indices[index as usize].1; - } - indices[i].1 = index; - $slice.swap(i, index as usize); - } - }}; - } - - let sz_u8 = mem::size_of::<(K, u8)>(); - let sz_u16 = mem::size_of::<(K, u16)>(); - let sz_u32 = mem::size_of::<(K, u32)>(); - let sz_usize = mem::size_of::<(K, usize)>(); - - let len = self.len(); - if len < 2 { - return; - } - if sz_u8 < sz_u16 && len <= (u8::MAX as usize) { - return sort_by_key!(u8, self, f); - } - if sz_u16 < sz_u32 && len <= (u16::MAX as usize) { - return sort_by_key!(u16, self, f); - } - if sz_u32 < sz_usize && len <= (u32::MAX as usize) { - return sort_by_key!(u32, self, f); - } - sort_by_key!(usize, self, f) - } - - /// Copies `self` into a new `Vec`. - /// - /// # Examples - /// - /// ``` - /// let s = [10, 40, 30]; - /// let x = s.to_vec(); - /// // Here, `s` and `x` can be modified independently. - /// ``` - #[cfg(not(no_global_oom_handling))] - #[rustc_allow_incoherent_impl] - #[rustc_conversion_suggestion] - #[stable(feature = "rust1", since = "1.0.0")] - #[inline] - pub fn to_vec(&self) -> Vec<T> - where - T: Clone, - { - self.to_vec_in(Global) - } - - /// Copies `self` into a new `Vec` with an allocator. - /// - /// # Examples - /// - /// ``` - /// #![feature(allocator_api)] - /// - /// use std::alloc::System; - /// - /// let s = [10, 40, 30]; - /// let x = s.to_vec_in(System); - /// // Here, `s` and `x` can be modified independently. - /// ``` - #[cfg(not(no_global_oom_handling))] - #[rustc_allow_incoherent_impl] - #[inline] - #[unstable(feature = "allocator_api", issue = "32838")] - pub fn to_vec_in<A: Allocator>(&self, alloc: A) -> Vec<T, A> - where - T: Clone, - { - // N.B., see the `hack` module in this file for more details. - hack::to_vec(self, alloc) - } - - /// Converts `self` into a vector without clones or allocation. - /// - /// The resulting vector can be converted back into a box via - /// `Vec<T>`'s `into_boxed_slice` method. - /// - /// # Examples - /// - /// ``` - /// let s: Box<[i32]> = Box::new([10, 40, 30]); - /// let x = s.into_vec(); - /// // `s` cannot be used anymore because it has been converted into `x`. - /// - /// assert_eq!(x, vec![10, 40, 30]); - /// ``` - #[rustc_allow_incoherent_impl] - #[stable(feature = "rust1", since = "1.0.0")] - #[inline] - pub fn into_vec<A: Allocator>(self: Box<Self, A>) -> Vec<T, A> { - // N.B., see the `hack` module in this file for more details. - hack::into_vec(self) - } - - /// Creates a vector by repeating a slice `n` times. - /// - /// # Panics - /// - /// This function will panic if the capacity would overflow. - /// - /// # Examples - /// - /// Basic usage: - /// - /// ``` - /// assert_eq!([1, 2].repeat(3), vec![1, 2, 1, 2, 1, 2]); - /// ``` - /// - /// A panic upon overflow: - /// - /// ```should_panic - /// // this will panic at runtime - /// b"0123456789abcdef".repeat(usize::MAX); - /// ``` - #[rustc_allow_incoherent_impl] - #[cfg(not(no_global_oom_handling))] - #[stable(feature = "repeat_generic_slice", since = "1.40.0")] - pub fn repeat(&self, n: usize) -> Vec<T> - where - T: Copy, - { - if n == 0 { - return Vec::new(); - } - - // If `n` is larger than zero, it can be split as - // `n = 2^expn + rem (2^expn > rem, expn >= 0, rem >= 0)`. - // `2^expn` is the number represented by the leftmost '1' bit of `n`, - // and `rem` is the remaining part of `n`. - - // Using `Vec` to access `set_len()`. - let capacity = self.len().checked_mul(n).expect("capacity overflow"); - let mut buf = Vec::with_capacity(capacity); - - // `2^expn` repetition is done by doubling `buf` `expn`-times. - buf.extend(self); - { - let mut m = n >> 1; - // If `m > 0`, there are remaining bits up to the leftmost '1'. - while m > 0 { - // `buf.extend(buf)`: - unsafe { - ptr::copy_nonoverlapping( - buf.as_ptr(), - (buf.as_mut_ptr() as *mut T).add(buf.len()), - buf.len(), - ); - // `buf` has capacity of `self.len() * n`. - let buf_len = buf.len(); - buf.set_len(buf_len * 2); - } - - m >>= 1; - } - } - - // `rem` (`= n - 2^expn`) repetition is done by copying - // first `rem` repetitions from `buf` itself. - let rem_len = capacity - buf.len(); // `self.len() * rem` - if rem_len > 0 { - // `buf.extend(buf[0 .. rem_len])`: - unsafe { - // This is non-overlapping since `2^expn > rem`. - ptr::copy_nonoverlapping( - buf.as_ptr(), - (buf.as_mut_ptr() as *mut T).add(buf.len()), - rem_len, - ); - // `buf.len() + rem_len` equals to `buf.capacity()` (`= self.len() * n`). - buf.set_len(capacity); - } - } - buf - } - - /// Flattens a slice of `T` into a single value `Self::Output`. - /// - /// # Examples - /// - /// ``` - /// assert_eq!(["hello", "world"].concat(), "helloworld"); - /// assert_eq!([[1, 2], [3, 4]].concat(), [1, 2, 3, 4]); - /// ``` - #[rustc_allow_incoherent_impl] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn concat<Item: ?Sized>(&self) -> <Self as Concat<Item>>::Output - where - Self: Concat<Item>, - { - Concat::concat(self) - } - - /// Flattens a slice of `T` into a single value `Self::Output`, placing a - /// given separator between each. - /// - /// # Examples - /// - /// ``` - /// assert_eq!(["hello", "world"].join(" "), "hello world"); - /// assert_eq!([[1, 2], [3, 4]].join(&0), [1, 2, 0, 3, 4]); - /// assert_eq!([[1, 2], [3, 4]].join(&[0, 0][..]), [1, 2, 0, 0, 3, 4]); - /// ``` - #[rustc_allow_incoherent_impl] - #[stable(feature = "rename_connect_to_join", since = "1.3.0")] - pub fn join<Separator>(&self, sep: Separator) -> <Self as Join<Separator>>::Output - where - Self: Join<Separator>, - { - Join::join(self, sep) - } - - /// Flattens a slice of `T` into a single value `Self::Output`, placing a - /// given separator between each. - /// - /// # Examples - /// - /// ``` - /// # #![allow(deprecated)] - /// assert_eq!(["hello", "world"].connect(" "), "hello world"); - /// assert_eq!([[1, 2], [3, 4]].connect(&0), [1, 2, 0, 3, 4]); - /// ``` - #[rustc_allow_incoherent_impl] - #[stable(feature = "rust1", since = "1.0.0")] - #[deprecated(since = "1.3.0", note = "renamed to join")] - pub fn connect<Separator>(&self, sep: Separator) -> <Self as Join<Separator>>::Output - where - Self: Join<Separator>, - { - Join::join(self, sep) - } -} - -#[cfg(not(test))] -impl [u8] { - /// Returns a vector containing a copy of this slice where each byte - /// is mapped to its ASCII upper case equivalent. - /// - /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', - /// but non-ASCII letters are unchanged. - /// - /// To uppercase the value in-place, use [`make_ascii_uppercase`]. - /// - /// [`make_ascii_uppercase`]: slice::make_ascii_uppercase - #[cfg(not(no_global_oom_handling))] - #[rustc_allow_incoherent_impl] - #[must_use = "this returns the uppercase bytes as a new Vec, \ - without modifying the original"] - #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] - #[inline] - pub fn to_ascii_uppercase(&self) -> Vec<u8> { - let mut me = self.to_vec(); - me.make_ascii_uppercase(); - me - } - - /// Returns a vector containing a copy of this slice where each byte - /// is mapped to its ASCII lower case equivalent. - /// - /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', - /// but non-ASCII letters are unchanged. - /// - /// To lowercase the value in-place, use [`make_ascii_lowercase`]. - /// - /// [`make_ascii_lowercase`]: slice::make_ascii_lowercase - #[cfg(not(no_global_oom_handling))] - #[rustc_allow_incoherent_impl] - #[must_use = "this returns the lowercase bytes as a new Vec, \ - without modifying the original"] - #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] - #[inline] - pub fn to_ascii_lowercase(&self) -> Vec<u8> { - let mut me = self.to_vec(); - me.make_ascii_lowercase(); - me - } -} - -//////////////////////////////////////////////////////////////////////////////// -// Extension traits for slices over specific kinds of data -//////////////////////////////////////////////////////////////////////////////// - -/// Helper trait for [`[T]::concat`](slice::concat). -/// -/// Note: the `Item` type parameter is not used in this trait, -/// but it allows impls to be more generic. -/// Without it, we get this error: -/// -/// ```error -/// error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predica -/// --> src/liballoc/slice.rs:608:6 -/// | -/// 608 | impl<T: Clone, V: Borrow<[T]>> Concat for [V] { -/// | ^ unconstrained type parameter -/// ``` -/// -/// This is because there could exist `V` types with multiple `Borrow<[_]>` impls, -/// such that multiple `T` types would apply: -/// -/// ``` -/// # #[allow(dead_code)] -/// pub struct Foo(Vec<u32>, Vec<String>); -/// -/// impl std::borrow::Borrow<[u32]> for Foo { -/// fn borrow(&self) -> &[u32] { &self.0 } -/// } -/// -/// impl std::borrow::Borrow<[String]> for Foo { -/// fn borrow(&self) -> &[String] { &self.1 } -/// } -/// ``` -#[unstable(feature = "slice_concat_trait", issue = "27747")] -pub trait Concat<Item: ?Sized> { - #[unstable(feature = "slice_concat_trait", issue = "27747")] - /// The resulting type after concatenation - type Output; - - /// Implementation of [`[T]::concat`](slice::concat) - #[unstable(feature = "slice_concat_trait", issue = "27747")] - fn concat(slice: &Self) -> Self::Output; -} - -/// Helper trait for [`[T]::join`](slice::join) -#[unstable(feature = "slice_concat_trait", issue = "27747")] -pub trait Join<Separator> { - #[unstable(feature = "slice_concat_trait", issue = "27747")] - /// The resulting type after concatenation - type Output; - - /// Implementation of [`[T]::join`](slice::join) - #[unstable(feature = "slice_concat_trait", issue = "27747")] - fn join(slice: &Self, sep: Separator) -> Self::Output; -} - -#[cfg(not(no_global_oom_handling))] -#[unstable(feature = "slice_concat_ext", issue = "27747")] -impl<T: Clone, V: Borrow<[T]>> Concat<T> for [V] { - type Output = Vec<T>; - - fn concat(slice: &Self) -> Vec<T> { - let size = slice.iter().map(|slice| slice.borrow().len()).sum(); - let mut result = Vec::with_capacity(size); - for v in slice { - result.extend_from_slice(v.borrow()) - } - result - } -} - -#[cfg(not(no_global_oom_handling))] -#[unstable(feature = "slice_concat_ext", issue = "27747")] -impl<T: Clone, V: Borrow<[T]>> Join<&T> for [V] { - type Output = Vec<T>; - - fn join(slice: &Self, sep: &T) -> Vec<T> { - let mut iter = slice.iter(); - let first = match iter.next() { - Some(first) => first, - None => return vec![], - }; - let size = slice.iter().map(|v| v.borrow().len()).sum::<usize>() + slice.len() - 1; - let mut result = Vec::with_capacity(size); - result.extend_from_slice(first.borrow()); - - for v in iter { - result.push(sep.clone()); - result.extend_from_slice(v.borrow()) - } - result - } -} - -#[cfg(not(no_global_oom_handling))] -#[unstable(feature = "slice_concat_ext", issue = "27747")] -impl<T: Clone, V: Borrow<[T]>> Join<&[T]> for [V] { - type Output = Vec<T>; - - fn join(slice: &Self, sep: &[T]) -> Vec<T> { - let mut iter = slice.iter(); - let first = match iter.next() { - Some(first) => first, - None => return vec![], - }; - let size = - slice.iter().map(|v| v.borrow().len()).sum::<usize>() + sep.len() * (slice.len() - 1); - let mut result = Vec::with_capacity(size); - result.extend_from_slice(first.borrow()); - - for v in iter { - result.extend_from_slice(sep); - result.extend_from_slice(v.borrow()) - } - result - } -} - -//////////////////////////////////////////////////////////////////////////////// -// Standard trait implementations for slices -//////////////////////////////////////////////////////////////////////////////// - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> Borrow<[T]> for Vec<T> { - fn borrow(&self) -> &[T] { - &self[..] - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> BorrowMut<[T]> for Vec<T> { - fn borrow_mut(&mut self) -> &mut [T] { - &mut self[..] - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: Clone> ToOwned for [T] { - type Owned = Vec<T>; - #[cfg(not(test))] - fn to_owned(&self) -> Vec<T> { - self.to_vec() - } - - #[cfg(test)] - fn to_owned(&self) -> Vec<T> { - hack::to_vec(self, Global) - } - - fn clone_into(&self, target: &mut Vec<T>) { - // drop anything in target that will not be overwritten - target.truncate(self.len()); - - // target.len <= self.len due to the truncate above, so the - // slices here are always in-bounds. - let (init, tail) = self.split_at(target.len()); - - // reuse the contained values' allocations/resources. - target.clone_from_slice(init); - target.extend_from_slice(tail); - } -} - -//////////////////////////////////////////////////////////////////////////////// -// Sorting -//////////////////////////////////////////////////////////////////////////////// - -/// Inserts `v[0]` into pre-sorted sequence `v[1..]` so that whole `v[..]` becomes sorted. -/// -/// This is the integral subroutine of insertion sort. -#[cfg(not(no_global_oom_handling))] -fn insert_head<T, F>(v: &mut [T], is_less: &mut F) -where - F: FnMut(&T, &T) -> bool, -{ - if v.len() >= 2 && is_less(&v[1], &v[0]) { - unsafe { - // There are three ways to implement insertion here: - // - // 1. Swap adjacent elements until the first one gets to its final destination. - // However, this way we copy data around more than is necessary. If elements are big - // structures (costly to copy), this method will be slow. - // - // 2. Iterate until the right place for the first element is found. Then shift the - // elements succeeding it to make room for it and finally place it into the - // remaining hole. This is a good method. - // - // 3. Copy the first element into a temporary variable. Iterate until the right place - // for it is found. As we go along, copy every traversed element into the slot - // preceding it. Finally, copy data from the temporary variable into the remaining - // hole. This method is very good. Benchmarks demonstrated slightly better - // performance than with the 2nd method. - // - // All methods were benchmarked, and the 3rd showed best results. So we chose that one. - let tmp = mem::ManuallyDrop::new(ptr::read(&v[0])); - - // Intermediate state of the insertion process is always tracked by `hole`, which - // serves two purposes: - // 1. Protects integrity of `v` from panics in `is_less`. - // 2. Fills the remaining hole in `v` in the end. - // - // Panic safety: - // - // If `is_less` panics at any point during the process, `hole` will get dropped and - // fill the hole in `v` with `tmp`, thus ensuring that `v` still holds every object it - // initially held exactly once. - let mut hole = InsertionHole { src: &*tmp, dest: &mut v[1] }; - ptr::copy_nonoverlapping(&v[1], &mut v[0], 1); - - for i in 2..v.len() { - if !is_less(&v[i], &*tmp) { - break; - } - ptr::copy_nonoverlapping(&v[i], &mut v[i - 1], 1); - hole.dest = &mut v[i]; - } - // `hole` gets dropped and thus copies `tmp` into the remaining hole in `v`. - } - } - - // When dropped, copies from `src` into `dest`. - struct InsertionHole<T> { - src: *const T, - dest: *mut T, - } - - impl<T> Drop for InsertionHole<T> { - fn drop(&mut self) { - unsafe { - ptr::copy_nonoverlapping(self.src, self.dest, 1); - } - } - } -} - -/// Merges non-decreasing runs `v[..mid]` and `v[mid..]` using `buf` as temporary storage, and -/// stores the result into `v[..]`. -/// -/// # Safety -/// -/// The two slices must be non-empty and `mid` must be in bounds. Buffer `buf` must be long enough -/// to hold a copy of the shorter slice. Also, `T` must not be a zero-sized type. -#[cfg(not(no_global_oom_handling))] -unsafe fn merge<T, F>(v: &mut [T], mid: usize, buf: *mut T, is_less: &mut F) -where - F: FnMut(&T, &T) -> bool, -{ - let len = v.len(); - let v = v.as_mut_ptr(); - let (v_mid, v_end) = unsafe { (v.add(mid), v.add(len)) }; - - // The merge process first copies the shorter run into `buf`. Then it traces the newly copied - // run and the longer run forwards (or backwards), comparing their next unconsumed elements and - // copying the lesser (or greater) one into `v`. - // - // As soon as the shorter run is fully consumed, the process is done. If the longer run gets - // consumed first, then we must copy whatever is left of the shorter run into the remaining - // hole in `v`. - // - // Intermediate state of the process is always tracked by `hole`, which serves two purposes: - // 1. Protects integrity of `v` from panics in `is_less`. - // 2. Fills the remaining hole in `v` if the longer run gets consumed first. - // - // Panic safety: - // - // If `is_less` panics at any point during the process, `hole` will get dropped and fill the - // hole in `v` with the unconsumed range in `buf`, thus ensuring that `v` still holds every - // object it initially held exactly once. - let mut hole; - - if mid <= len - mid { - // The left run is shorter. - unsafe { - ptr::copy_nonoverlapping(v, buf, mid); - hole = MergeHole { start: buf, end: buf.add(mid), dest: v }; - } - - // Initially, these pointers point to the beginnings of their arrays. - let left = &mut hole.start; - let mut right = v_mid; - let out = &mut hole.dest; - - while *left < hole.end && right < v_end { - // Consume the lesser side. - // If equal, prefer the left run to maintain stability. - unsafe { - let to_copy = if is_less(&*right, &**left) { - get_and_increment(&mut right) - } else { - get_and_increment(left) - }; - ptr::copy_nonoverlapping(to_copy, get_and_increment(out), 1); - } - } - } else { - // The right run is shorter. - unsafe { - ptr::copy_nonoverlapping(v_mid, buf, len - mid); - hole = MergeHole { start: buf, end: buf.add(len - mid), dest: v_mid }; - } - - // Initially, these pointers point past the ends of their arrays. - let left = &mut hole.dest; - let right = &mut hole.end; - let mut out = v_end; - - while v < *left && buf < *right { - // Consume the greater side. - // If equal, prefer the right run to maintain stability. - unsafe { - let to_copy = if is_less(&*right.offset(-1), &*left.offset(-1)) { - decrement_and_get(left) - } else { - decrement_and_get(right) - }; - ptr::copy_nonoverlapping(to_copy, decrement_and_get(&mut out), 1); - } - } - } - // Finally, `hole` gets dropped. If the shorter run was not fully consumed, whatever remains of - // it will now be copied into the hole in `v`. - - unsafe fn get_and_increment<T>(ptr: &mut *mut T) -> *mut T { - let old = *ptr; - *ptr = unsafe { ptr.offset(1) }; - old - } - - unsafe fn decrement_and_get<T>(ptr: &mut *mut T) -> *mut T { - *ptr = unsafe { ptr.offset(-1) }; - *ptr - } - - // When dropped, copies the range `start..end` into `dest..`. - struct MergeHole<T> { - start: *mut T, - end: *mut T, - dest: *mut T, - } - - impl<T> Drop for MergeHole<T> { - fn drop(&mut self) { - // `T` is not a zero-sized type, and these are pointers into a slice's elements. - unsafe { - let len = self.end.sub_ptr(self.start); - ptr::copy_nonoverlapping(self.start, self.dest, len); - } - } - } -} - -/// This merge sort borrows some (but not all) ideas from TimSort, which is described in detail -/// [here](https://github.com/python/cpython/blob/main/Objects/listsort.txt). -/// -/// The algorithm identifies strictly descending and non-descending subsequences, which are called -/// natural runs. There is a stack of pending runs yet to be merged. Each newly found run is pushed -/// onto the stack, and then some pairs of adjacent runs are merged until these two invariants are -/// satisfied: -/// -/// 1. for every `i` in `1..runs.len()`: `runs[i - 1].len > runs[i].len` -/// 2. for every `i` in `2..runs.len()`: `runs[i - 2].len > runs[i - 1].len + runs[i].len` -/// -/// The invariants ensure that the total running time is *O*(*n* \* log(*n*)) worst-case. -#[cfg(not(no_global_oom_handling))] -fn merge_sort<T, F>(v: &mut [T], mut is_less: F) -where - F: FnMut(&T, &T) -> bool, -{ - // Slices of up to this length get sorted using insertion sort. - const MAX_INSERTION: usize = 20; - // Very short runs are extended using insertion sort to span at least this many elements. - const MIN_RUN: usize = 10; - - // Sorting has no meaningful behavior on zero-sized types. - if size_of::<T>() == 0 { - return; - } - - let len = v.len(); - - // Short arrays get sorted in-place via insertion sort to avoid allocations. - if len <= MAX_INSERTION { - if len >= 2 { - for i in (0..len - 1).rev() { - insert_head(&mut v[i..], &mut is_less); - } - } - return; - } - - // Allocate a buffer to use as scratch memory. We keep the length 0 so we can keep in it - // shallow copies of the contents of `v` without risking the dtors running on copies if - // `is_less` panics. When merging two sorted runs, this buffer holds a copy of the shorter run, - // which will always have length at most `len / 2`. - let mut buf = Vec::with_capacity(len / 2); - - // In order to identify natural runs in `v`, we traverse it backwards. That might seem like a - // strange decision, but consider the fact that merges more often go in the opposite direction - // (forwards). According to benchmarks, merging forwards is slightly faster than merging - // backwards. To conclude, identifying runs by traversing backwards improves performance. - let mut runs = vec![]; - let mut end = len; - while end > 0 { - // Find the next natural run, and reverse it if it's strictly descending. - let mut start = end - 1; - if start > 0 { - start -= 1; - unsafe { - if is_less(v.get_unchecked(start + 1), v.get_unchecked(start)) { - while start > 0 && is_less(v.get_unchecked(start), v.get_unchecked(start - 1)) { - start -= 1; - } - v[start..end].reverse(); - } else { - while start > 0 && !is_less(v.get_unchecked(start), v.get_unchecked(start - 1)) - { - start -= 1; - } - } - } - } - - // Insert some more elements into the run if it's too short. Insertion sort is faster than - // merge sort on short sequences, so this significantly improves performance. - while start > 0 && end - start < MIN_RUN { - start -= 1; - insert_head(&mut v[start..end], &mut is_less); - } - - // Push this run onto the stack. - runs.push(Run { start, len: end - start }); - end = start; - - // Merge some pairs of adjacent runs to satisfy the invariants. - while let Some(r) = collapse(&runs) { - let left = runs[r + 1]; - let right = runs[r]; - unsafe { - merge( - &mut v[left.start..right.start + right.len], - left.len, - buf.as_mut_ptr(), - &mut is_less, - ); - } - runs[r] = Run { start: left.start, len: left.len + right.len }; - runs.remove(r + 1); - } - } - - // Finally, exactly one run must remain in the stack. - debug_assert!(runs.len() == 1 && runs[0].start == 0 && runs[0].len == len); - - // Examines the stack of runs and identifies the next pair of runs to merge. More specifically, - // if `Some(r)` is returned, that means `runs[r]` and `runs[r + 1]` must be merged next. If the - // algorithm should continue building a new run instead, `None` is returned. - // - // TimSort is infamous for its buggy implementations, as described here: - // http://envisage-project.eu/timsort-specification-and-verification/ - // - // The gist of the story is: we must enforce the invariants on the top four runs on the stack. - // Enforcing them on just top three is not sufficient to ensure that the invariants will still - // hold for *all* runs in the stack. - // - // This function correctly checks invariants for the top four runs. Additionally, if the top - // run starts at index 0, it will always demand a merge operation until the stack is fully - // collapsed, in order to complete the sort. - #[inline] - fn collapse(runs: &[Run]) -> Option<usize> { - let n = runs.len(); - if n >= 2 - && (runs[n - 1].start == 0 - || runs[n - 2].len <= runs[n - 1].len - || (n >= 3 && runs[n - 3].len <= runs[n - 2].len + runs[n - 1].len) - || (n >= 4 && runs[n - 4].len <= runs[n - 3].len + runs[n - 2].len)) - { - if n >= 3 && runs[n - 3].len < runs[n - 1].len { Some(n - 3) } else { Some(n - 2) } - } else { - None - } - } - - #[derive(Clone, Copy)] - struct Run { - start: usize, - len: usize, - } -} |