| // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| //! A dynamically-sized view into a contiguous sequence, `[T]`. |
| //! |
| //! 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!("{} is a number!", n); |
| //! } |
| //! ``` |
| //! |
| //! 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. |
| //! |
| //! *[See also the slice primitive type](../../std/primitive.slice.html).* |
| //! |
| //! [`Clone`]: ../../std/clone/trait.Clone.html |
| //! [`Eq`]: ../../std/cmp/trait.Eq.html |
| //! [`Ord`]: ../../std/cmp/trait.Ord.html |
| //! [`Iter`]: struct.Iter.html |
| //! [`Hash`]: ../../std/hash/trait.Hash.html |
| //! [`.iter`]: ../../std/primitive.slice.html#method.iter |
| //! [`.iter_mut`]: ../../std/primitive.slice.html#method.iter_mut |
| //! [`.split`]: ../../std/primitive.slice.html#method.split |
| //! [`.splitn`]: ../../std/primitive.slice.html#method.splitn |
| //! [`.chunks`]: ../../std/primitive.slice.html#method.chunks |
| //! [`.windows`]: ../../std/primitive.slice.html#method.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::cmp::Ordering::{self, Less}; |
| use core::mem::size_of; |
| use core::mem; |
| use core::ptr; |
| use core::slice as core_slice; |
| |
| use borrow::{Borrow, BorrowMut, ToOwned}; |
| use boxed::Box; |
| use vec::Vec; |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::slice::{Chunks, Windows}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::slice::{Iter, IterMut}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::slice::{SplitMut, ChunksMut, Split}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::slice::{SplitN, RSplitN, SplitNMut, RSplitNMut}; |
| #[unstable(feature = "slice_rsplit", issue = "41020")] |
| pub use core::slice::{RSplit, RSplitMut}; |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use core::slice::{from_raw_parts, from_raw_parts_mut}; |
| #[unstable(feature = "from_ref", issue = "45703")] |
| pub use core::slice::{from_ref, from_ref_mut}; |
| #[unstable(feature = "slice_get_slice", issue = "35729")] |
| pub use core::slice::SliceIndex; |
| #[unstable(feature = "exact_chunks", issue = "47115")] |
| pub use core::slice::{ExactChunks, ExactChunksMut}; |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Basic slice extension methods |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| // HACK(japaric) needed for the implementation of `vec!` macro during testing |
| // NB see the hack module in this file for more details |
| #[cfg(test)] |
| pub use self::hack::into_vec; |
| |
| // HACK(japaric) needed for the implementation of `Vec::clone` during testing |
| // NB see the hack module in this file for more details |
| #[cfg(test)] |
| pub use self::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 |
| mod hack { |
| use boxed::Box; |
| use core::mem; |
| |
| #[cfg(test)] |
| use string::ToString; |
| use vec::Vec; |
| |
| pub fn into_vec<T>(mut b: Box<[T]>) -> Vec<T> { |
| unsafe { |
| let xs = Vec::from_raw_parts(b.as_mut_ptr(), b.len(), b.len()); |
| mem::forget(b); |
| xs |
| } |
| } |
| |
| #[inline] |
| pub fn to_vec<T>(s: &[T]) -> Vec<T> |
| where T: Clone |
| { |
| let mut vector = Vec::with_capacity(s.len()); |
| vector.extend_from_slice(s); |
| vector |
| } |
| } |
| |
| #[lang = "slice"] |
| #[cfg(not(test))] |
| impl<T> [T] { |
| /// Returns the number of elements in the slice. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let a = [1, 2, 3]; |
| /// assert_eq!(a.len(), 3); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn len(&self) -> usize { |
| core_slice::SliceExt::len(self) |
| } |
| |
| /// Returns `true` if the slice has a length of 0. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let a = [1, 2, 3]; |
| /// assert!(!a.is_empty()); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn is_empty(&self) -> bool { |
| core_slice::SliceExt::is_empty(self) |
| } |
| |
| /// Returns the first element of the slice, or `None` if it is empty. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = [10, 40, 30]; |
| /// assert_eq!(Some(&10), v.first()); |
| /// |
| /// let w: &[i32] = &[]; |
| /// assert_eq!(None, w.first()); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn first(&self) -> Option<&T> { |
| core_slice::SliceExt::first(self) |
| } |
| |
| /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &mut [0, 1, 2]; |
| /// |
| /// if let Some(first) = x.first_mut() { |
| /// *first = 5; |
| /// } |
| /// assert_eq!(x, &[5, 1, 2]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn first_mut(&mut self) -> Option<&mut T> { |
| core_slice::SliceExt::first_mut(self) |
| } |
| |
| /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &[0, 1, 2]; |
| /// |
| /// if let Some((first, elements)) = x.split_first() { |
| /// assert_eq!(first, &0); |
| /// assert_eq!(elements, &[1, 2]); |
| /// } |
| /// ``` |
| #[stable(feature = "slice_splits", since = "1.5.0")] |
| #[inline] |
| pub fn split_first(&self) -> Option<(&T, &[T])> { |
| core_slice::SliceExt::split_first(self) |
| } |
| |
| /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &mut [0, 1, 2]; |
| /// |
| /// if let Some((first, elements)) = x.split_first_mut() { |
| /// *first = 3; |
| /// elements[0] = 4; |
| /// elements[1] = 5; |
| /// } |
| /// assert_eq!(x, &[3, 4, 5]); |
| /// ``` |
| #[stable(feature = "slice_splits", since = "1.5.0")] |
| #[inline] |
| pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> { |
| core_slice::SliceExt::split_first_mut(self) |
| } |
| |
| /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &[0, 1, 2]; |
| /// |
| /// if let Some((last, elements)) = x.split_last() { |
| /// assert_eq!(last, &2); |
| /// assert_eq!(elements, &[0, 1]); |
| /// } |
| /// ``` |
| #[stable(feature = "slice_splits", since = "1.5.0")] |
| #[inline] |
| pub fn split_last(&self) -> Option<(&T, &[T])> { |
| core_slice::SliceExt::split_last(self) |
| |
| } |
| |
| /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &mut [0, 1, 2]; |
| /// |
| /// if let Some((last, elements)) = x.split_last_mut() { |
| /// *last = 3; |
| /// elements[0] = 4; |
| /// elements[1] = 5; |
| /// } |
| /// assert_eq!(x, &[4, 5, 3]); |
| /// ``` |
| #[stable(feature = "slice_splits", since = "1.5.0")] |
| #[inline] |
| pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> { |
| core_slice::SliceExt::split_last_mut(self) |
| } |
| |
| /// Returns the last element of the slice, or `None` if it is empty. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = [10, 40, 30]; |
| /// assert_eq!(Some(&30), v.last()); |
| /// |
| /// let w: &[i32] = &[]; |
| /// assert_eq!(None, w.last()); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn last(&self) -> Option<&T> { |
| core_slice::SliceExt::last(self) |
| } |
| |
| /// Returns a mutable pointer to the last item in the slice. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &mut [0, 1, 2]; |
| /// |
| /// if let Some(last) = x.last_mut() { |
| /// *last = 10; |
| /// } |
| /// assert_eq!(x, &[0, 1, 10]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn last_mut(&mut self) -> Option<&mut T> { |
| core_slice::SliceExt::last_mut(self) |
| } |
| |
| /// Returns a reference to an element or subslice depending on the type of |
| /// index. |
| /// |
| /// - If given a position, returns a reference to the element at that |
| /// position or `None` if out of bounds. |
| /// - If given a range, returns the subslice corresponding to that range, |
| /// or `None` if out of bounds. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = [10, 40, 30]; |
| /// assert_eq!(Some(&40), v.get(1)); |
| /// assert_eq!(Some(&[10, 40][..]), v.get(0..2)); |
| /// assert_eq!(None, v.get(3)); |
| /// assert_eq!(None, v.get(0..4)); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn get<I>(&self, index: I) -> Option<&I::Output> |
| where I: SliceIndex<Self> |
| { |
| core_slice::SliceExt::get(self, index) |
| } |
| |
| /// Returns a mutable reference to an element or subslice depending on the |
| /// type of index (see [`get`]) or `None` if the index is out of bounds. |
| /// |
| /// [`get`]: #method.get |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &mut [0, 1, 2]; |
| /// |
| /// if let Some(elem) = x.get_mut(1) { |
| /// *elem = 42; |
| /// } |
| /// assert_eq!(x, &[0, 42, 2]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output> |
| where I: SliceIndex<Self> |
| { |
| core_slice::SliceExt::get_mut(self, index) |
| } |
| |
| /// Returns a reference to an element or subslice, without doing bounds |
| /// checking. |
| /// |
| /// This is generally not recommended, use with caution! For a safe |
| /// alternative see [`get`]. |
| /// |
| /// [`get`]: #method.get |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &[1, 2, 4]; |
| /// |
| /// unsafe { |
| /// assert_eq!(x.get_unchecked(1), &2); |
| /// } |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output |
| where I: SliceIndex<Self> |
| { |
| core_slice::SliceExt::get_unchecked(self, index) |
| } |
| |
| /// Returns a mutable reference to an element or subslice, without doing |
| /// bounds checking. |
| /// |
| /// This is generally not recommended, use with caution! For a safe |
| /// alternative see [`get_mut`]. |
| /// |
| /// [`get_mut`]: #method.get_mut |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &mut [1, 2, 4]; |
| /// |
| /// unsafe { |
| /// let elem = x.get_unchecked_mut(1); |
| /// *elem = 13; |
| /// } |
| /// assert_eq!(x, &[1, 13, 4]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output |
| where I: SliceIndex<Self> |
| { |
| core_slice::SliceExt::get_unchecked_mut(self, index) |
| } |
| |
| /// Returns a raw pointer to the slice's buffer. |
| /// |
| /// The caller must ensure that the slice outlives the pointer this |
| /// function returns, or else it will end up pointing to garbage. |
| /// |
| /// Modifying the container referenced by this slice may cause its buffer |
| /// to be reallocated, which would also make any pointers to it invalid. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &[1, 2, 4]; |
| /// let x_ptr = x.as_ptr(); |
| /// |
| /// unsafe { |
| /// for i in 0..x.len() { |
| /// assert_eq!(x.get_unchecked(i), &*x_ptr.offset(i as isize)); |
| /// } |
| /// } |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn as_ptr(&self) -> *const T { |
| core_slice::SliceExt::as_ptr(self) |
| } |
| |
| /// Returns an unsafe mutable pointer to the slice's buffer. |
| /// |
| /// The caller must ensure that the slice outlives the pointer this |
| /// function returns, or else it will end up pointing to garbage. |
| /// |
| /// Modifying the container referenced by this slice may cause its buffer |
| /// to be reallocated, which would also make any pointers to it invalid. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &mut [1, 2, 4]; |
| /// let x_ptr = x.as_mut_ptr(); |
| /// |
| /// unsafe { |
| /// for i in 0..x.len() { |
| /// *x_ptr.offset(i as isize) += 2; |
| /// } |
| /// } |
| /// assert_eq!(x, &[3, 4, 6]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn as_mut_ptr(&mut self) -> *mut T { |
| core_slice::SliceExt::as_mut_ptr(self) |
| } |
| |
| /// Swaps two elements in the slice. |
| /// |
| /// # Arguments |
| /// |
| /// * a - The index of the first element |
| /// * b - The index of the second element |
| /// |
| /// # Panics |
| /// |
| /// Panics if `a` or `b` are out of bounds. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut v = ["a", "b", "c", "d"]; |
| /// v.swap(1, 3); |
| /// assert!(v == ["a", "d", "c", "b"]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn swap(&mut self, a: usize, b: usize) { |
| core_slice::SliceExt::swap(self, a, b) |
| } |
| |
| /// Reverses the order of elements in the slice, in place. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut v = [1, 2, 3]; |
| /// v.reverse(); |
| /// assert!(v == [3, 2, 1]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn reverse(&mut self) { |
| core_slice::SliceExt::reverse(self) |
| } |
| |
| /// Returns an iterator over the slice. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &[1, 2, 4]; |
| /// let mut iterator = x.iter(); |
| /// |
| /// assert_eq!(iterator.next(), Some(&1)); |
| /// assert_eq!(iterator.next(), Some(&2)); |
| /// assert_eq!(iterator.next(), Some(&4)); |
| /// assert_eq!(iterator.next(), None); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn iter(&self) -> Iter<T> { |
| core_slice::SliceExt::iter(self) |
| } |
| |
| /// Returns an iterator that allows modifying each value. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = &mut [1, 2, 4]; |
| /// for elem in x.iter_mut() { |
| /// *elem += 2; |
| /// } |
| /// assert_eq!(x, &[3, 4, 6]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn iter_mut(&mut self) -> IterMut<T> { |
| core_slice::SliceExt::iter_mut(self) |
| } |
| |
| /// Returns an iterator over all contiguous windows of length |
| /// `size`. The windows overlap. If the slice is shorter than |
| /// `size`, the iterator returns no values. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `size` is 0. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let slice = ['r', 'u', 's', 't']; |
| /// let mut iter = slice.windows(2); |
| /// assert_eq!(iter.next().unwrap(), &['r', 'u']); |
| /// assert_eq!(iter.next().unwrap(), &['u', 's']); |
| /// assert_eq!(iter.next().unwrap(), &['s', 't']); |
| /// assert!(iter.next().is_none()); |
| /// ``` |
| /// |
| /// If the slice is shorter than `size`: |
| /// |
| /// ``` |
| /// let slice = ['f', 'o', 'o']; |
| /// let mut iter = slice.windows(4); |
| /// assert!(iter.next().is_none()); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn windows(&self, size: usize) -> Windows<T> { |
| core_slice::SliceExt::windows(self, size) |
| } |
| |
| /// Returns an iterator over `chunk_size` elements of the slice at a |
| /// time. The chunks are slices and do not overlap. If `chunk_size` does |
| /// not divide the length of the slice, then the last chunk will |
| /// not have length `chunk_size`. |
| /// |
| /// See [`exact_chunks`] for a variant of this iterator that returns chunks |
| /// of always exactly `chunk_size` elements. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `chunk_size` is 0. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let slice = ['l', 'o', 'r', 'e', 'm']; |
| /// let mut iter = slice.chunks(2); |
| /// assert_eq!(iter.next().unwrap(), &['l', 'o']); |
| /// assert_eq!(iter.next().unwrap(), &['r', 'e']); |
| /// assert_eq!(iter.next().unwrap(), &['m']); |
| /// assert!(iter.next().is_none()); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn chunks(&self, chunk_size: usize) -> Chunks<T> { |
| core_slice::SliceExt::chunks(self, chunk_size) |
| } |
| |
| /// Returns an iterator over `chunk_size` elements of the slice at a |
| /// time. The chunks are slices and do not overlap. If `chunk_size` does |
| /// not divide the length of the slice, then the last up to `chunk_size-1` |
| /// elements will be omitted. |
| /// |
| /// Due to each chunk having exactly `chunk_size` elements, the compiler |
| /// can often optimize the resulting code better than in the case of |
| /// [`chunks`]. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `chunk_size` is 0. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(exact_chunks)] |
| /// |
| /// let slice = ['l', 'o', 'r', 'e', 'm']; |
| /// let mut iter = slice.exact_chunks(2); |
| /// assert_eq!(iter.next().unwrap(), &['l', 'o']); |
| /// assert_eq!(iter.next().unwrap(), &['r', 'e']); |
| /// assert!(iter.next().is_none()); |
| /// ``` |
| #[unstable(feature = "exact_chunks", issue = "47115")] |
| #[inline] |
| pub fn exact_chunks(&self, chunk_size: usize) -> ExactChunks<T> { |
| core_slice::SliceExt::exact_chunks(self, chunk_size) |
| } |
| |
| /// Returns an iterator over `chunk_size` elements of the slice at a time. |
| /// The chunks are mutable slices, and do not overlap. If `chunk_size` does |
| /// not divide the length of the slice, then the last chunk will not |
| /// have length `chunk_size`. |
| /// |
| /// See [`exact_chunks_mut`] for a variant of this iterator that returns chunks |
| /// of always exactly `chunk_size` elements. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `chunk_size` is 0. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = &mut [0, 0, 0, 0, 0]; |
| /// let mut count = 1; |
| /// |
| /// for chunk in v.chunks_mut(2) { |
| /// for elem in chunk.iter_mut() { |
| /// *elem += count; |
| /// } |
| /// count += 1; |
| /// } |
| /// assert_eq!(v, &[1, 1, 2, 2, 3]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T> { |
| core_slice::SliceExt::chunks_mut(self, chunk_size) |
| } |
| |
| /// Returns an iterator over `chunk_size` elements of the slice at a time. |
| /// The chunks are mutable slices, and do not overlap. If `chunk_size` does |
| /// not divide the length of the slice, then the last up to `chunk_size-1` |
| /// elements will be omitted. |
| /// |
| /// |
| /// Due to each chunk having exactly `chunk_size` elements, the compiler |
| /// can often optimize the resulting code better than in the case of |
| /// [`chunks_mut`]. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `chunk_size` is 0. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(exact_chunks)] |
| /// |
| /// let v = &mut [0, 0, 0, 0, 0]; |
| /// let mut count = 1; |
| /// |
| /// for chunk in v.exact_chunks_mut(2) { |
| /// for elem in chunk.iter_mut() { |
| /// *elem += count; |
| /// } |
| /// count += 1; |
| /// } |
| /// assert_eq!(v, &[1, 1, 2, 2, 0]); |
| /// ``` |
| #[unstable(feature = "exact_chunks", issue = "47115")] |
| #[inline] |
| pub fn exact_chunks_mut(&mut self, chunk_size: usize) -> ExactChunksMut<T> { |
| core_slice::SliceExt::exact_chunks_mut(self, chunk_size) |
| } |
| |
| /// Divides one slice into two at an index. |
| /// |
| /// The first will contain all indices from `[0, mid)` (excluding |
| /// the index `mid` itself) and the second will contain all |
| /// indices from `[mid, len)` (excluding the index `len` itself). |
| /// |
| /// # Panics |
| /// |
| /// Panics if `mid > len`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = [1, 2, 3, 4, 5, 6]; |
| /// |
| /// { |
| /// let (left, right) = v.split_at(0); |
| /// assert!(left == []); |
| /// assert!(right == [1, 2, 3, 4, 5, 6]); |
| /// } |
| /// |
| /// { |
| /// let (left, right) = v.split_at(2); |
| /// assert!(left == [1, 2]); |
| /// assert!(right == [3, 4, 5, 6]); |
| /// } |
| /// |
| /// { |
| /// let (left, right) = v.split_at(6); |
| /// assert!(left == [1, 2, 3, 4, 5, 6]); |
| /// assert!(right == []); |
| /// } |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn split_at(&self, mid: usize) -> (&[T], &[T]) { |
| core_slice::SliceExt::split_at(self, mid) |
| } |
| |
| /// Divides one mutable slice into two at an index. |
| /// |
| /// The first will contain all indices from `[0, mid)` (excluding |
| /// the index `mid` itself) and the second will contain all |
| /// indices from `[mid, len)` (excluding the index `len` itself). |
| /// |
| /// # Panics |
| /// |
| /// Panics if `mid > len`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut v = [1, 0, 3, 0, 5, 6]; |
| /// // scoped to restrict the lifetime of the borrows |
| /// { |
| /// let (left, right) = v.split_at_mut(2); |
| /// assert!(left == [1, 0]); |
| /// assert!(right == [3, 0, 5, 6]); |
| /// left[1] = 2; |
| /// right[1] = 4; |
| /// } |
| /// assert!(v == [1, 2, 3, 4, 5, 6]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) { |
| core_slice::SliceExt::split_at_mut(self, mid) |
| } |
| |
| /// Returns an iterator over subslices separated by elements that match |
| /// `pred`. The matched element is not contained in the subslices. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let slice = [10, 40, 33, 20]; |
| /// let mut iter = slice.split(|num| num % 3 == 0); |
| /// |
| /// assert_eq!(iter.next().unwrap(), &[10, 40]); |
| /// assert_eq!(iter.next().unwrap(), &[20]); |
| /// assert!(iter.next().is_none()); |
| /// ``` |
| /// |
| /// If the first element is matched, an empty slice will be the first item |
| /// returned by the iterator. Similarly, if the last element in the slice |
| /// is matched, an empty slice will be the last item returned by the |
| /// iterator: |
| /// |
| /// ``` |
| /// let slice = [10, 40, 33]; |
| /// let mut iter = slice.split(|num| num % 3 == 0); |
| /// |
| /// assert_eq!(iter.next().unwrap(), &[10, 40]); |
| /// assert_eq!(iter.next().unwrap(), &[]); |
| /// assert!(iter.next().is_none()); |
| /// ``` |
| /// |
| /// If two matched elements are directly adjacent, an empty slice will be |
| /// present between them: |
| /// |
| /// ``` |
| /// let slice = [10, 6, 33, 20]; |
| /// let mut iter = slice.split(|num| num % 3 == 0); |
| /// |
| /// assert_eq!(iter.next().unwrap(), &[10]); |
| /// assert_eq!(iter.next().unwrap(), &[]); |
| /// assert_eq!(iter.next().unwrap(), &[20]); |
| /// assert!(iter.next().is_none()); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn split<F>(&self, pred: F) -> Split<T, F> |
| where F: FnMut(&T) -> bool |
| { |
| core_slice::SliceExt::split(self, pred) |
| } |
| |
| /// Returns an iterator over mutable subslices separated by elements that |
| /// match `pred`. The matched element is not contained in the subslices. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut v = [10, 40, 30, 20, 60, 50]; |
| /// |
| /// for group in v.split_mut(|num| *num % 3 == 0) { |
| /// group[0] = 1; |
| /// } |
| /// assert_eq!(v, [1, 40, 30, 1, 60, 1]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<T, F> |
| where F: FnMut(&T) -> bool |
| { |
| core_slice::SliceExt::split_mut(self, pred) |
| } |
| |
| /// Returns an iterator over subslices separated by elements that match |
| /// `pred`, starting at the end of the slice and working backwards. |
| /// The matched element is not contained in the subslices. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(slice_rsplit)] |
| /// |
| /// let slice = [11, 22, 33, 0, 44, 55]; |
| /// let mut iter = slice.rsplit(|num| *num == 0); |
| /// |
| /// assert_eq!(iter.next().unwrap(), &[44, 55]); |
| /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]); |
| /// assert_eq!(iter.next(), None); |
| /// ``` |
| /// |
| /// As with `split()`, if the first or last element is matched, an empty |
| /// slice will be the first (or last) item returned by the iterator. |
| /// |
| /// ``` |
| /// #![feature(slice_rsplit)] |
| /// |
| /// let v = &[0, 1, 1, 2, 3, 5, 8]; |
| /// let mut it = v.rsplit(|n| *n % 2 == 0); |
| /// assert_eq!(it.next().unwrap(), &[]); |
| /// assert_eq!(it.next().unwrap(), &[3, 5]); |
| /// assert_eq!(it.next().unwrap(), &[1, 1]); |
| /// assert_eq!(it.next().unwrap(), &[]); |
| /// assert_eq!(it.next(), None); |
| /// ``` |
| #[unstable(feature = "slice_rsplit", issue = "41020")] |
| #[inline] |
| pub fn rsplit<F>(&self, pred: F) -> RSplit<T, F> |
| where F: FnMut(&T) -> bool |
| { |
| core_slice::SliceExt::rsplit(self, pred) |
| } |
| |
| /// Returns an iterator over mutable subslices separated by elements that |
| /// match `pred`, starting at the end of the slice and working |
| /// backwards. The matched element is not contained in the subslices. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(slice_rsplit)] |
| /// |
| /// let mut v = [100, 400, 300, 200, 600, 500]; |
| /// |
| /// let mut count = 0; |
| /// for group in v.rsplit_mut(|num| *num % 3 == 0) { |
| /// count += 1; |
| /// group[0] = count; |
| /// } |
| /// assert_eq!(v, [3, 400, 300, 2, 600, 1]); |
| /// ``` |
| /// |
| #[unstable(feature = "slice_rsplit", issue = "41020")] |
| #[inline] |
| pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<T, F> |
| where F: FnMut(&T) -> bool |
| { |
| core_slice::SliceExt::rsplit_mut(self, pred) |
| } |
| |
| /// Returns an iterator over subslices separated by elements that match |
| /// `pred`, limited to returning at most `n` items. The matched element is |
| /// not contained in the subslices. |
| /// |
| /// The last element returned, if any, will contain the remainder of the |
| /// slice. |
| /// |
| /// # Examples |
| /// |
| /// Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`, |
| /// `[20, 60, 50]`): |
| /// |
| /// ``` |
| /// let v = [10, 40, 30, 20, 60, 50]; |
| /// |
| /// for group in v.splitn(2, |num| *num % 3 == 0) { |
| /// println!("{:?}", group); |
| /// } |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F> |
| where F: FnMut(&T) -> bool |
| { |
| core_slice::SliceExt::splitn(self, n, pred) |
| } |
| |
| /// Returns an iterator over subslices separated by elements that match |
| /// `pred`, limited to returning at most `n` items. The matched element is |
| /// not contained in the subslices. |
| /// |
| /// The last element returned, if any, will contain the remainder of the |
| /// slice. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut v = [10, 40, 30, 20, 60, 50]; |
| /// |
| /// for group in v.splitn_mut(2, |num| *num % 3 == 0) { |
| /// group[0] = 1; |
| /// } |
| /// assert_eq!(v, [1, 40, 30, 1, 60, 50]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<T, F> |
| where F: FnMut(&T) -> bool |
| { |
| core_slice::SliceExt::splitn_mut(self, n, pred) |
| } |
| |
| /// Returns an iterator over subslices separated by elements that match |
| /// `pred` limited to returning at most `n` items. This starts at the end of |
| /// the slice and works backwards. The matched element is not contained in |
| /// the subslices. |
| /// |
| /// The last element returned, if any, will contain the remainder of the |
| /// slice. |
| /// |
| /// # Examples |
| /// |
| /// Print the slice split once, starting from the end, by numbers divisible |
| /// by 3 (i.e. `[50]`, `[10, 40, 30, 20]`): |
| /// |
| /// ``` |
| /// let v = [10, 40, 30, 20, 60, 50]; |
| /// |
| /// for group in v.rsplitn(2, |num| *num % 3 == 0) { |
| /// println!("{:?}", group); |
| /// } |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F> |
| where F: FnMut(&T) -> bool |
| { |
| core_slice::SliceExt::rsplitn(self, n, pred) |
| } |
| |
| /// Returns an iterator over subslices separated by elements that match |
| /// `pred` limited to returning at most `n` items. This starts at the end of |
| /// the slice and works backwards. The matched element is not contained in |
| /// the subslices. |
| /// |
| /// The last element returned, if any, will contain the remainder of the |
| /// slice. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut s = [10, 40, 30, 20, 60, 50]; |
| /// |
| /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) { |
| /// group[0] = 1; |
| /// } |
| /// assert_eq!(s, [1, 40, 30, 20, 60, 1]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<T, F> |
| where F: FnMut(&T) -> bool |
| { |
| core_slice::SliceExt::rsplitn_mut(self, n, pred) |
| } |
| |
| /// Returns `true` if the slice contains an element with the given value. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = [10, 40, 30]; |
| /// assert!(v.contains(&30)); |
| /// assert!(!v.contains(&50)); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn contains(&self, x: &T) -> bool |
| where T: PartialEq |
| { |
| core_slice::SliceExt::contains(self, x) |
| } |
| |
| /// Returns `true` if `needle` is a prefix of the slice. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = [10, 40, 30]; |
| /// assert!(v.starts_with(&[10])); |
| /// assert!(v.starts_with(&[10, 40])); |
| /// assert!(!v.starts_with(&[50])); |
| /// assert!(!v.starts_with(&[10, 50])); |
| /// ``` |
| /// |
| /// Always returns `true` if `needle` is an empty slice: |
| /// |
| /// ``` |
| /// let v = &[10, 40, 30]; |
| /// assert!(v.starts_with(&[])); |
| /// let v: &[u8] = &[]; |
| /// assert!(v.starts_with(&[])); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn starts_with(&self, needle: &[T]) -> bool |
| where T: PartialEq |
| { |
| core_slice::SliceExt::starts_with(self, needle) |
| } |
| |
| /// Returns `true` if `needle` is a suffix of the slice. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = [10, 40, 30]; |
| /// assert!(v.ends_with(&[30])); |
| /// assert!(v.ends_with(&[40, 30])); |
| /// assert!(!v.ends_with(&[50])); |
| /// assert!(!v.ends_with(&[50, 30])); |
| /// ``` |
| /// |
| /// Always returns `true` if `needle` is an empty slice: |
| /// |
| /// ``` |
| /// let v = &[10, 40, 30]; |
| /// assert!(v.ends_with(&[])); |
| /// let v: &[u8] = &[]; |
| /// assert!(v.ends_with(&[])); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn ends_with(&self, needle: &[T]) -> bool |
| where T: PartialEq |
| { |
| core_slice::SliceExt::ends_with(self, needle) |
| } |
| |
| /// Binary searches this sorted slice for a given element. |
| /// |
| /// If the value is found then `Ok` is returned, containing the |
| /// index of the matching element; if the value is not found then |
| /// `Err` is returned, containing the index where a matching |
| /// element could be inserted while maintaining sorted order. |
| /// |
| /// # Examples |
| /// |
| /// Looks up a series of four elements. The first is found, with a |
| /// uniquely determined position; the second and third are not |
| /// found; the fourth could match any position in `[1, 4]`. |
| /// |
| /// ``` |
| /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]; |
| /// |
| /// assert_eq!(s.binary_search(&13), Ok(9)); |
| /// assert_eq!(s.binary_search(&4), Err(7)); |
| /// assert_eq!(s.binary_search(&100), Err(13)); |
| /// let r = s.binary_search(&1); |
| /// assert!(match r { Ok(1...4) => true, _ => false, }); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn binary_search(&self, x: &T) -> Result<usize, usize> |
| where T: Ord |
| { |
| core_slice::SliceExt::binary_search(self, x) |
| } |
| |
| /// Binary searches this sorted slice with a comparator function. |
| /// |
| /// The comparator function should implement an order consistent |
| /// with the sort order of the underlying slice, returning an |
| /// order code that indicates whether its argument is `Less`, |
| /// `Equal` or `Greater` the desired target. |
| /// |
| /// If a matching value is found then returns `Ok`, containing |
| /// the index for the matched element; if no match is found then |
| /// `Err` is returned, containing the index where a matching |
| /// element could be inserted while maintaining sorted order. |
| /// |
| /// # Examples |
| /// |
| /// Looks up a series of four elements. The first is found, with a |
| /// uniquely determined position; the second and third are not |
| /// found; the fourth could match any position in `[1, 4]`. |
| /// |
| /// ``` |
| /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]; |
| /// |
| /// let seek = 13; |
| /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9)); |
| /// let seek = 4; |
| /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7)); |
| /// let seek = 100; |
| /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13)); |
| /// let seek = 1; |
| /// let r = s.binary_search_by(|probe| probe.cmp(&seek)); |
| /// assert!(match r { Ok(1...4) => true, _ => false, }); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize> |
| where F: FnMut(&'a T) -> Ordering |
| { |
| core_slice::SliceExt::binary_search_by(self, f) |
| } |
| |
| /// Binary searches this sorted slice with a key extraction function. |
| /// |
| /// Assumes that the slice is sorted by the key, for instance with |
| /// [`sort_by_key`] using the same key extraction function. |
| /// |
| /// If a matching value is found then returns `Ok`, containing the |
| /// index for the matched element; if no match is found then `Err` |
| /// is returned, containing the index where a matching element could |
| /// be inserted while maintaining sorted order. |
| /// |
| /// [`sort_by_key`]: #method.sort_by_key |
| /// |
| /// # Examples |
| /// |
| /// Looks up a series of four elements in a slice of pairs sorted by |
| /// their second elements. The first is found, with a uniquely |
| /// determined position; the second and third are not found; the |
| /// fourth could match any position in `[1, 4]`. |
| /// |
| /// ``` |
| /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1), |
| /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13), |
| /// (1, 21), (2, 34), (4, 55)]; |
| /// |
| /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9)); |
| /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7)); |
| /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13)); |
| /// let r = s.binary_search_by_key(&1, |&(a,b)| b); |
| /// assert!(match r { Ok(1...4) => true, _ => false, }); |
| /// ``` |
| #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")] |
| #[inline] |
| pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, f: F) -> Result<usize, usize> |
| where F: FnMut(&'a T) -> B, |
| B: Ord |
| { |
| core_slice::SliceExt::binary_search_by_key(self, b, f) |
| } |
| |
| /// 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`](#method.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]); |
| /// ``` |
| #[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. |
| /// |
| /// 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`](#method.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]); |
| /// ``` |
| #[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(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_by_key`](#method.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]); |
| /// ``` |
| #[stable(feature = "slice_sort_by_key", since = "1.7.0")] |
| #[inline] |
| pub fn sort_by_key<B, F>(&mut self, mut f: F) |
| where F: FnMut(&T) -> B, B: Ord |
| { |
| merge_sort(self, |a, b| f(a).lt(&f(b))); |
| } |
| |
| /// Sorts the slice, but may not preserve the order of equal elements. |
| /// |
| /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate), |
| /// and `O(n log n)` worst-case. |
| /// |
| /// # 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. |
| /// |
| /// It is typically faster than stable sorting, except in a few special cases, e.g. when the |
| /// slice consists of several concatenated sorted sequences. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut v = [-5, 4, 1, -3, 2]; |
| /// |
| /// v.sort_unstable(); |
| /// assert!(v == [-5, -3, 1, 2, 4]); |
| /// ``` |
| /// |
| /// [pdqsort]: https://github.com/orlp/pdqsort |
| #[stable(feature = "sort_unstable", since = "1.20.0")] |
| #[inline] |
| pub fn sort_unstable(&mut self) |
| where T: Ord |
| { |
| core_slice::SliceExt::sort_unstable(self); |
| } |
| |
| /// Sorts the slice with a comparator function, but may not preserve the order of equal |
| /// elements. |
| /// |
| /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate), |
| /// and `O(n log n)` worst-case. |
| /// |
| /// # 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. |
| /// |
| /// It is typically faster than stable sorting, except in a few special cases, e.g. when the |
| /// slice consists of several concatenated sorted sequences. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut v = [5, 4, 1, 3, 2]; |
| /// v.sort_unstable_by(|a, b| a.cmp(b)); |
| /// assert!(v == [1, 2, 3, 4, 5]); |
| /// |
| /// // reverse sorting |
| /// v.sort_unstable_by(|a, b| b.cmp(a)); |
| /// assert!(v == [5, 4, 3, 2, 1]); |
| /// ``` |
| /// |
| /// [pdqsort]: https://github.com/orlp/pdqsort |
| #[stable(feature = "sort_unstable", since = "1.20.0")] |
| #[inline] |
| pub fn sort_unstable_by<F>(&mut self, compare: F) |
| where F: FnMut(&T, &T) -> Ordering |
| { |
| core_slice::SliceExt::sort_unstable_by(self, compare); |
| } |
| |
| /// Sorts the slice with a key extraction function, but may not preserve the order of equal |
| /// elements. |
| /// |
| /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate), |
| /// and `O(n log n)` worst-case. |
| /// |
| /// # 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. |
| /// |
| /// It is typically faster than stable sorting, except in a few special cases, e.g. when the |
| /// slice consists of several concatenated sorted sequences. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let mut v = [-5i32, 4, 1, -3, 2]; |
| /// |
| /// v.sort_unstable_by_key(|k| k.abs()); |
| /// assert!(v == [1, 2, -3, 4, -5]); |
| /// ``` |
| /// |
| /// [pdqsort]: https://github.com/orlp/pdqsort |
| #[stable(feature = "sort_unstable", since = "1.20.0")] |
| #[inline] |
| pub fn sort_unstable_by_key<B, F>(&mut self, f: F) |
| where F: FnMut(&T) -> B, |
| B: Ord |
| { |
| core_slice::SliceExt::sort_unstable_by_key(self, f); |
| } |
| |
| /// Rotates the slice in-place such that the first `mid` elements of the |
| /// slice move to the end while the last `self.len() - mid` elements move to |
| /// the front. After calling `rotate_left`, the element previously at index |
| /// `mid` will become the first element in the slice. |
| /// |
| /// # Panics |
| /// |
| /// This function will panic if `mid` is greater than the length of the |
| /// slice. Note that `mid == self.len()` does _not_ panic and is a no-op |
| /// rotation. |
| /// |
| /// # Complexity |
| /// |
| /// Takes linear (in `self.len()`) time. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(slice_rotate)] |
| /// |
| /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; |
| /// a.rotate_left(2); |
| /// assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']); |
| /// ``` |
| /// |
| /// Rotating a subslice: |
| /// |
| /// ``` |
| /// #![feature(slice_rotate)] |
| /// |
| /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; |
| /// a[1..5].rotate_left(1); |
| /// assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']); |
| /// ``` |
| #[unstable(feature = "slice_rotate", issue = "41891")] |
| pub fn rotate_left(&mut self, mid: usize) { |
| core_slice::SliceExt::rotate_left(self, mid); |
| } |
| |
| #[unstable(feature = "slice_rotate", issue = "41891")] |
| #[rustc_deprecated(since = "", reason = "renamed to `rotate_left`")] |
| pub fn rotate(&mut self, mid: usize) { |
| core_slice::SliceExt::rotate_left(self, mid); |
| } |
| |
| /// Rotates the slice in-place such that the first `self.len() - k` |
| /// elements of the slice move to the end while the last `k` elements move |
| /// to the front. After calling `rotate_right`, the element previously at |
| /// index `self.len() - k` will become the first element in the slice. |
| /// |
| /// # Panics |
| /// |
| /// This function will panic if `k` is greater than the length of the |
| /// slice. Note that `k == self.len()` does _not_ panic and is a no-op |
| /// rotation. |
| /// |
| /// # Complexity |
| /// |
| /// Takes linear (in `self.len()`) time. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(slice_rotate)] |
| /// |
| /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; |
| /// a.rotate_right(2); |
| /// assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']); |
| /// ``` |
| /// |
| /// Rotate a subslice: |
| /// |
| /// ``` |
| /// #![feature(slice_rotate)] |
| /// |
| /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; |
| /// a[1..5].rotate_right(1); |
| /// assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']); |
| /// ``` |
| #[unstable(feature = "slice_rotate", issue = "41891")] |
| pub fn rotate_right(&mut self, k: usize) { |
| core_slice::SliceExt::rotate_right(self, k); |
| } |
| |
| /// Copies the elements from `src` into `self`. |
| /// |
| /// The length of `src` must be the same as `self`. |
| /// |
| /// If `src` implements `Copy`, it can be more performant to use |
| /// [`copy_from_slice`]. |
| /// |
| /// # Panics |
| /// |
| /// This function will panic if the two slices have different lengths. |
| /// |
| /// # Examples |
| /// |
| /// Cloning two elements from a slice into another: |
| /// |
| /// ``` |
| /// let src = [1, 2, 3, 4]; |
| /// let mut dst = [0, 0]; |
| /// |
| /// dst.clone_from_slice(&src[2..]); |
| /// |
| /// assert_eq!(src, [1, 2, 3, 4]); |
| /// assert_eq!(dst, [3, 4]); |
| /// ``` |
| /// |
| /// Rust enforces that there can only be one mutable reference with no |
| /// immutable references to a particular piece of data in a particular |
| /// scope. Because of this, attempting to use `clone_from_slice` on a |
| /// single slice will result in a compile failure: |
| /// |
| /// ```compile_fail |
| /// let mut slice = [1, 2, 3, 4, 5]; |
| /// |
| /// slice[..2].clone_from_slice(&slice[3..]); // compile fail! |
| /// ``` |
| /// |
| /// To work around this, we can use [`split_at_mut`] to create two distinct |
| /// sub-slices from a slice: |
| /// |
| /// ``` |
| /// let mut slice = [1, 2, 3, 4, 5]; |
| /// |
| /// { |
| /// let (left, right) = slice.split_at_mut(2); |
| /// left.clone_from_slice(&right[1..]); |
| /// } |
| /// |
| /// assert_eq!(slice, [4, 5, 3, 4, 5]); |
| /// ``` |
| /// |
| /// [`copy_from_slice`]: #method.copy_from_slice |
| /// [`split_at_mut`]: #method.split_at_mut |
| #[stable(feature = "clone_from_slice", since = "1.7.0")] |
| pub fn clone_from_slice(&mut self, src: &[T]) where T: Clone { |
| core_slice::SliceExt::clone_from_slice(self, src) |
| } |
| |
| /// Copies all elements from `src` into `self`, using a memcpy. |
| /// |
| /// The length of `src` must be the same as `self`. |
| /// |
| /// If `src` does not implement `Copy`, use [`clone_from_slice`]. |
| /// |
| /// # Panics |
| /// |
| /// This function will panic if the two slices have different lengths. |
| /// |
| /// # Examples |
| /// |
| /// Copying two elements from a slice into another: |
| /// |
| /// ``` |
| /// let src = [1, 2, 3, 4]; |
| /// let mut dst = [0, 0]; |
| /// |
| /// dst.copy_from_slice(&src[2..]); |
| /// |
| /// assert_eq!(src, [1, 2, 3, 4]); |
| /// assert_eq!(dst, [3, 4]); |
| /// ``` |
| /// |
| /// Rust enforces that there can only be one mutable reference with no |
| /// immutable references to a particular piece of data in a particular |
| /// scope. Because of this, attempting to use `copy_from_slice` on a |
| /// single slice will result in a compile failure: |
| /// |
| /// ```compile_fail |
| /// let mut slice = [1, 2, 3, 4, 5]; |
| /// |
| /// slice[..2].copy_from_slice(&slice[3..]); // compile fail! |
| /// ``` |
| /// |
| /// To work around this, we can use [`split_at_mut`] to create two distinct |
| /// sub-slices from a slice: |
| /// |
| /// ``` |
| /// let mut slice = [1, 2, 3, 4, 5]; |
| /// |
| /// { |
| /// let (left, right) = slice.split_at_mut(2); |
| /// left.copy_from_slice(&right[1..]); |
| /// } |
| /// |
| /// assert_eq!(slice, [4, 5, 3, 4, 5]); |
| /// ``` |
| /// |
| /// [`clone_from_slice`]: #method.clone_from_slice |
| /// [`split_at_mut`]: #method.split_at_mut |
| #[stable(feature = "copy_from_slice", since = "1.9.0")] |
| pub fn copy_from_slice(&mut self, src: &[T]) where T: Copy { |
| core_slice::SliceExt::copy_from_slice(self, src) |
| } |
| |
| /// Swaps all elements in `self` with those in `other`. |
| /// |
| /// The length of `other` must be the same as `self`. |
| /// |
| /// # Panics |
| /// |
| /// This function will panic if the two slices have different lengths. |
| /// |
| /// # Example |
| /// |
| /// Swapping two elements across slices: |
| /// |
| /// ``` |
| /// #![feature(swap_with_slice)] |
| /// |
| /// let mut slice1 = [0, 0]; |
| /// let mut slice2 = [1, 2, 3, 4]; |
| /// |
| /// slice1.swap_with_slice(&mut slice2[2..]); |
| /// |
| /// assert_eq!(slice1, [3, 4]); |
| /// assert_eq!(slice2, [1, 2, 0, 0]); |
| /// ``` |
| /// |
| /// Rust enforces that there can only be one mutable reference to a |
| /// particular piece of data in a particular scope. Because of this, |
| /// attempting to use `swap_with_slice` on a single slice will result in |
| /// a compile failure: |
| /// |
| /// ```compile_fail |
| /// #![feature(swap_with_slice)] |
| /// |
| /// let mut slice = [1, 2, 3, 4, 5]; |
| /// slice[..2].swap_with_slice(&mut slice[3..]); // compile fail! |
| /// ``` |
| /// |
| /// To work around this, we can use [`split_at_mut`] to create two distinct |
| /// mutable sub-slices from a slice: |
| /// |
| /// ``` |
| /// #![feature(swap_with_slice)] |
| /// |
| /// let mut slice = [1, 2, 3, 4, 5]; |
| /// |
| /// { |
| /// let (left, right) = slice.split_at_mut(2); |
| /// left.swap_with_slice(&mut right[1..]); |
| /// } |
| /// |
| /// assert_eq!(slice, [4, 5, 3, 1, 2]); |
| /// ``` |
| /// |
| /// [`split_at_mut`]: #method.split_at_mut |
| #[unstable(feature = "swap_with_slice", issue = "44030")] |
| pub fn swap_with_slice(&mut self, other: &mut [T]) { |
| core_slice::SliceExt::swap_with_slice(self, other) |
| } |
| |
| /// 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. |
| /// ``` |
| #[rustc_conversion_suggestion] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn to_vec(&self) -> Vec<T> |
| where T: Clone |
| { |
| // NB see hack module in this file |
| hack::to_vec(self) |
| } |
| |
| /// 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]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn into_vec(self: Box<Self>) -> Vec<T> { |
| // NB see hack module in this file |
| hack::into_vec(self) |
| } |
| } |
| |
| #[lang = "slice_u8"] |
| #[cfg(not(test))] |
| impl [u8] { |
| /// Checks if all bytes in this slice are within the ASCII range. |
| #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] |
| #[inline] |
| pub fn is_ascii(&self) -> bool { |
| self.iter().all(|b| b.is_ascii()) |
| } |
| |
| /// 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`]: #method.make_ascii_uppercase |
| #[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`]: #method.make_ascii_lowercase |
| #[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 |
| } |
| |
| /// Checks that two slices are an ASCII case-insensitive match. |
| /// |
| /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`, |
| /// but without allocating and copying temporaries. |
| #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] |
| #[inline] |
| pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool { |
| self.len() == other.len() && |
| self.iter().zip(other).all(|(a, b)| { |
| a.eq_ignore_ascii_case(b) |
| }) |
| } |
| |
| /// Converts this slice to its ASCII upper case equivalent in-place. |
| /// |
| /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', |
| /// but non-ASCII letters are unchanged. |
| /// |
| /// To return a new uppercased value without modifying the existing one, use |
| /// [`to_ascii_uppercase`]. |
| /// |
| /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase |
| #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] |
| #[inline] |
| pub fn make_ascii_uppercase(&mut self) { |
| for byte in self { |
| byte.make_ascii_uppercase(); |
| } |
| } |
| |
| /// Converts this slice to its ASCII lower case equivalent in-place. |
| /// |
| /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', |
| /// but non-ASCII letters are unchanged. |
| /// |
| /// To return a new lowercased value without modifying the existing one, use |
| /// [`to_ascii_lowercase`]. |
| /// |
| /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase |
| #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] |
| #[inline] |
| pub fn make_ascii_lowercase(&mut self) { |
| for byte in self { |
| byte.make_ascii_lowercase(); |
| } |
| } |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Extension traits for slices over specific kinds of data |
| //////////////////////////////////////////////////////////////////////////////// |
| #[unstable(feature = "slice_concat_ext", |
| reason = "trait should not have to exist", |
| issue = "27747")] |
| /// An extension trait for concatenating slices |
| /// |
| /// While this trait is unstable, the methods are stable. `SliceConcatExt` is |
| /// included in the [standard library prelude], so you can use [`join()`] and |
| /// [`concat()`] as if they existed on `[T]` itself. |
| /// |
| /// [standard library prelude]: ../../std/prelude/index.html |
| /// [`join()`]: #tymethod.join |
| /// [`concat()`]: #tymethod.concat |
| pub trait SliceConcatExt<T: ?Sized> { |
| #[unstable(feature = "slice_concat_ext", |
| reason = "trait should not have to exist", |
| issue = "27747")] |
| /// The resulting type after concatenation |
| type Output; |
| |
| /// 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]); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn concat(&self) -> Self::Output; |
| |
| /// 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]); |
| /// ``` |
| #[stable(feature = "rename_connect_to_join", since = "1.3.0")] |
| fn join(&self, sep: &T) -> Self::Output; |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_deprecated(since = "1.3.0", reason = "renamed to join")] |
| fn connect(&self, sep: &T) -> Self::Output; |
| } |
| |
| #[unstable(feature = "slice_concat_ext", |
| reason = "trait should not have to exist", |
| issue = "27747")] |
| impl<T: Clone, V: Borrow<[T]>> SliceConcatExt<T> for [V] { |
| type Output = Vec<T>; |
| |
| fn concat(&self) -> Vec<T> { |
| let size = self.iter().fold(0, |acc, v| acc + v.borrow().len()); |
| let mut result = Vec::with_capacity(size); |
| for v in self { |
| result.extend_from_slice(v.borrow()) |
| } |
| result |
| } |
| |
| fn join(&self, sep: &T) -> Vec<T> { |
| let size = self.iter().fold(0, |acc, v| acc + v.borrow().len()); |
| let mut result = Vec::with_capacity(size + self.len()); |
| let mut first = true; |
| for v in self { |
| if first { |
| first = false |
| } else { |
| result.push(sep.clone()) |
| } |
| result.extend_from_slice(v.borrow()) |
| } |
| result |
| } |
| |
| fn connect(&self, sep: &T) -> Vec<T> { |
| self.join(sep) |
| } |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // 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[..] |
| } |
| } |
| |
| #[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) |
| } |
| |
| fn clone_into(&self, target: &mut Vec<T>) { |
| // drop anything in target that will not be overwritten |
| target.truncate(self.len()); |
| let len = target.len(); |
| |
| // reuse the contained values' allocations/resources. |
| target.clone_from_slice(&self[..len]); |
| |
| // target.len <= self.len due to the truncate above, so the |
| // slice here is always in-bounds. |
| target.extend_from_slice(&self[len..]); |
| } |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Sorting |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| /// Inserts `v[0]` into pre-sorted sequence `v[1..]` so that whole `v[..]` becomes sorted. |
| /// |
| /// This is the integral subroutine of insertion sort. |
| 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 mut 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: &mut *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: *mut 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. |
| 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.offset(mid as isize); |
| let v_end = v.offset(len as isize); |
| |
| // 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. |
| ptr::copy_nonoverlapping(v, buf, mid); |
| hole = MergeHole { |
| start: buf, |
| end: buf.offset(mid as isize), |
| 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. |
| 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. |
| ptr::copy_nonoverlapping(v_mid, buf, len - mid); |
| hole = MergeHole { |
| start: buf, |
| end: buf.offset((len - mid) as isize), |
| 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. |
| 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 = ptr.offset(1); |
| old |
| } |
| |
| unsafe fn decrement_and_get<T>(ptr: &mut *mut T) -> *mut T { |
| *ptr = 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, so it's okay to divide by its size. |
| let len = (self.end as usize - self.start as usize) / mem::size_of::<T>(); |
| unsafe { 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](http://svn.python.org/projects/python/trunk/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. |
| 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, |
| } |
| } |