// 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 or the MIT license // , 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 alloc::boxed::Box; use core::cmp::Ordering::{self, Greater}; use core::mem::size_of; use core::mem; use core::ptr; use core::slice as core_slice; use borrow::{Borrow, BorrowMut, ToOwned}; 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}; #[stable(feature = "rust1", since = "1.0.0")] pub use core::slice::{from_raw_parts, from_raw_parts_mut}; #[unstable(feature = "slice_get_slice", issue = "35729")] pub use core::slice::SliceIndex; //////////////////////////////////////////////////////////////////////////////// // 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 alloc::boxed::Box; use core::mem; #[cfg(test)] use string::ToString; use vec::Vec; pub fn into_vec(mut b: Box<[T]>) -> Vec { unsafe { let xs = Vec::from_raw_parts(b.as_mut_ptr(), b.len(), b.len()); mem::forget(b); xs } } #[inline] pub fn to_vec(s: &[T]) -> Vec where T: Clone { let mut vector = Vec::with_capacity(s.len()); vector.extend_from_slice(s); vector } } #[lang = "slice"] #[cfg(not(test))] impl [T] { /// Returns the number of elements in the slice. /// /// # Example /// /// ``` /// 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. /// /// # Example /// /// ``` /// 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 a 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 a 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 a slice. /// /// # 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 a slice. /// /// # 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 a slice. /// /// # 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 a slice. /// /// # 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 a 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 the element of a slice at the given index, or `None` if the /// index is out of bounds. /// /// # Examples /// /// ``` /// let v = [10, 40, 30]; /// assert_eq!(Some(&40), v.get(1)); /// assert_eq!(None, v.get(3)); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn get(&self, index: I) -> Option<&I::Output> where I: SliceIndex { core_slice::SliceExt::get(self, index) } /// Returns a mutable reference to the element at the given index. /// /// # Examples /// /// ``` /// let x = &mut [0, 1, 2]; /// /// if let Some(elem) = x.get_mut(1) { /// *elem = 42; /// } /// assert_eq!(x, &[0, 42, 2]); /// ``` /// or `None` if the index is out of bounds #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn get_mut(&mut self, index: I) -> Option<&mut I::Output> where I: SliceIndex { core_slice::SliceExt::get_mut(self, index) } /// Returns a pointer to the element at the given index, without doing /// bounds checking. So use it very carefully! /// /// # 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(&self, index: I) -> &I::Output where I: SliceIndex { core_slice::SliceExt::get_unchecked(self, index) } /// Returns an unsafe mutable pointer to the element in index. So use it /// very carefully! /// /// # 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(&mut self, index: I) -> &mut I::Output where I: SliceIndex { 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 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 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 a 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) } /// Reverse the order of elements in a slice, in place. /// /// # Example /// /// ``` /// 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 { core_slice::SliceExt::iter(self) } /// Returns an iterator that allows modifying each value. /// /// # Examples /// /// ``` /// let x = &mut [1, 2, 4]; /// { /// let iterator = x.iter_mut(); /// /// for elem in iterator { /// *elem += 2; /// } /// } /// assert_eq!(x, &[3, 4, 6]); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn iter_mut(&mut self) -> IterMut { 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. /// /// # Example /// /// ``` /// 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 { core_slice::SliceExt::windows(self, size) } /// Returns an iterator over `size` elements of the slice at a /// time. The chunks are slices and do not overlap. If `size` does /// not divide the length of the slice, then the last chunk will /// not have length `size`. /// /// # Panics /// /// Panics if `size` is 0. /// /// # Example /// /// ``` /// 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, size: usize) -> Chunks { core_slice::SliceExt::chunks(self, 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`. /// /// # 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 { core_slice::SliceExt::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 = [10, 40, 30, 20, 50]; /// let (v1, v2) = v.split_at(2); /// assert_eq!([10, 40], v1); /// assert_eq!([30, 20, 50], v2); /// ``` #[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 `&mut` 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, 2, 3, 4, 5, 6]; /// /// // scoped to restrict the lifetime of the borrows /// { /// let (left, right) = v.split_at_mut(0); /// assert!(left == []); /// assert!(right == [1, 2, 3, 4, 5, 6]); /// } /// /// { /// let (left, right) = v.split_at_mut(2); /// assert!(left == [1, 2]); /// assert!(right == [3, 4, 5, 6]); /// } /// /// { /// let (left, right) = v.split_at_mut(6); /// assert!(left == [1, 2, 3, 4, 5, 6]); /// assert!(right == []); /// } /// ``` #[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(&self, pred: F) -> Split 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(&mut self, pred: F) -> SplitMut where F: FnMut(&T) -> bool { core_slice::SliceExt::split_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(&self, n: usize, pred: F) -> SplitN 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(&mut self, n: usize, pred: F) -> SplitNMut 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(&self, n: usize, pred: F) -> RSplitN 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(&mut self, n: usize, pred: F) -> RSplitNMut 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])); /// ``` #[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])); /// ``` #[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 search a 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. /// /// # Example /// /// 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 where T: Ord { core_slice::SliceExt::binary_search(self, x) } /// Binary search a 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. /// /// # Example /// /// 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 where F: FnMut(&'a T) -> Ordering { core_slice::SliceExt::binary_search_by(self, f) } /// Binary search a 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 where F: FnMut(&'a T) -> B, B: Ord { core_slice::SliceExt::binary_search_by_key(self, b, f) } /// This is equivalent to `self.sort_by(|a, b| a.cmp(b))`. /// /// This sort is stable and `O(n log n)` worst-case, but allocates /// temporary storage half the size of `self`. /// /// # 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 { self.sort_by(|a, b| a.cmp(b)) } /// Sorts the slice, in place, using `f` to extract a key by which to /// order the sort by. /// /// This sort is stable and `O(n log n)` worst-case, but allocates /// temporary storage half the size of `self`. /// /// # 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(&mut self, mut f: F) where F: FnMut(&T) -> B, B: Ord { self.sort_by(|a, b| f(a).cmp(&f(b))) } /// Sorts the slice, in place, using `compare` to compare /// elements. /// /// This sort is stable and `O(n log n)` worst-case, but allocates /// temporary storage half the size of `self`. /// /// # 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(&mut self, compare: F) where F: FnMut(&T, &T) -> Ordering { merge_sort(self, compare) } /// Copies the elements from `src` into `self`. /// /// The length of `src` must be the same as `self`. /// /// # Panics /// /// This function will panic if the two slices have different lengths. /// /// # Example /// /// ``` /// let mut dst = [0, 0, 0]; /// let src = [1, 2, 3]; /// /// dst.clone_from_slice(&src); /// assert!(dst == [1, 2, 3]); /// ``` #[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`. /// /// # Panics /// /// This function will panic if the two slices have different lengths. /// /// # Example /// /// ``` /// let mut dst = [0, 0, 0]; /// let src = [1, 2, 3]; /// /// dst.copy_from_slice(&src); /// assert_eq!(src, dst); /// ``` #[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) } /// 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. /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn to_vec(&self) -> Vec where T: Clone { // NB see hack module in this file hack::to_vec(self) } /// Converts `self` into a vector without clones or allocation. /// /// # 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) -> Vec { // NB see hack module in this file hack::into_vec(self) } } //////////////////////////////////////////////////////////////////////////////// // 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 pub trait SliceConcatExt { #[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"); /// ``` #[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"); /// ``` #[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> SliceConcatExt for [V] { type Output = Vec; fn concat(&self) -> Vec { 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 { 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 { self.join(sep) } } //////////////////////////////////////////////////////////////////////////////// // Standard trait implementations for slices //////////////////////////////////////////////////////////////////////////////// #[stable(feature = "rust1", since = "1.0.0")] impl Borrow<[T]> for Vec { fn borrow(&self) -> &[T] { &self[..] } } #[stable(feature = "rust1", since = "1.0.0")] impl BorrowMut<[T]> for Vec { fn borrow_mut(&mut self) -> &mut [T] { &mut self[..] } } #[stable(feature = "rust1", since = "1.0.0")] impl ToOwned for [T] { type Owned = Vec; #[cfg(not(test))] fn to_owned(&self) -> Vec { self.to_vec() } // HACK(japaric): with cfg(test) the inherent `[T]::to_vec`, which is required for this method // definition, is not available. Since we don't require this method for testing purposes, I'll // just stub it // NB see the slice::hack module in slice.rs for more information #[cfg(test)] fn to_owned(&self) -> Vec { panic!("not available with cfg(test)") } } //////////////////////////////////////////////////////////////////////////////// // 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(v: &mut [T], compare: &mut F) where F: FnMut(&T, &T) -> Ordering { if v.len() >= 2 && compare(&v[0], &v[1]) == Greater { 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 = NoDrop { value: 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 `compare`. // 2. Fills the remaining hole in `v` in the end. // // Panic safety: // // If `compare` 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.value, dest: &mut v[1], }; ptr::copy_nonoverlapping(&v[1], &mut v[0], 1); for i in 2..v.len() { if compare(&tmp.value, &v[i]) != Greater { 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`. } } // Holds a value, but never drops it. #[allow(unions_with_drop_fields)] union NoDrop { value: T } // When dropped, copies from `src` into `dest`. struct InsertionHole { src: *mut T, dest: *mut T, } impl Drop for InsertionHole { 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(v: &mut [T], mid: usize, buf: *mut T, compare: &mut F) where F: FnMut(&T, &T) -> Ordering { 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 `compare`. // 2. Fills the remaining hole in `v` if the longer run gets consumed first. // // Panic safety: // // If `compare` 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 compare(&**left, &*right) == Greater { 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 compare(&*left.offset(-1), &*right.offset(-1)) == Greater { 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(ptr: &mut *mut T) -> *mut T { let old = *ptr; *ptr = ptr.offset(1); old } unsafe fn decrement_and_get(ptr: &mut *mut T) -> *mut T { *ptr = ptr.offset(-1); *ptr } // When dropped, copies the range `start..end` into `dest..`. struct MergeHole { start: *mut T, end: *mut T, dest: *mut T, } impl Drop for MergeHole { fn drop(&mut self) { // `T` is not a zero-sized type, so it's okay to divide by it's size. let len = (self.end as usize - self.start as usize) / mem::size_of::(); 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(v: &mut [T], mut compare: F) where F: FnMut(&T, &T) -> Ordering { // Sorting has no meaningful behavior on zero-sized types. if size_of::() == 0 { return; } // FIXME #12092: These numbers are platform-specific and need more extensive testing/tuning. // // If `v` has length up to `insertion_len`, simply switch to insertion sort because it is going // to perform better than merge sort. For bigger types `T`, the threshold is smaller. // // Short runs are extended using insertion sort to span at least `min_run` elements, in order // to improve performance. let (max_insertion, min_run) = if size_of::() <= 16 { (64, 32) } else { (32, 16) }; 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 compare); } } 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 // `compare` 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; if compare(&v[start], &v[start + 1]) == Greater { while start > 0 && compare(&v[start - 1], &v[start]) == Greater { start -= 1; } v[start..end].reverse(); } else { while start > 0 && compare(&v[start - 1], &v[start]) != Greater { 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 compare); } // Push this run onto the stack. runs.push(Run { start: 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 compare); } 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 it's 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 { 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, } }