| // 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, |
| } |
| } |
