1464 lines
44 KiB
Rust
1464 lines
44 KiB
Rust
// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! A dynamically-sized view into a contiguous sequence, `[T]`.
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//!
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//! Slices are a view into a block of memory represented as a pointer and a
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//! length.
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//!
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//! ```
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//! // slicing a Vec
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//! let vec = vec![1, 2, 3];
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//! let int_slice = &vec[..];
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//! // coercing an array to a slice
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//! let str_slice: &[&str] = &["one", "two", "three"];
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//! ```
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//!
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//! Slices are either mutable or shared. The shared slice type is `&[T]`,
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//! while the mutable slice type is `&mut [T]`, where `T` represents the element
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//! type. For example, you can mutate the block of memory that a mutable slice
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//! points to:
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//!
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//! ```
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//! let x = &mut [1, 2, 3];
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//! x[1] = 7;
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//! assert_eq!(x, &[1, 7, 3]);
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//! ```
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//!
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//! Here are some of the things this module contains:
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//!
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//! ## Structs
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//!
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//! There are several structs that are useful for slices, such as `Iter`, which
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//! represents iteration over a slice.
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//!
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//! ## Trait Implementations
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//!
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//! There are several implementations of common traits for slices. Some examples
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//! include:
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//!
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//! * `Clone`
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//! * `Eq`, `Ord` - for slices whose element type are `Eq` or `Ord`.
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//! * `Hash` - for slices whose element type is `Hash`
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//!
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//! ## Iteration
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//!
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//! The slices implement `IntoIterator`. The iterator yields references to the
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//! slice elements.
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//!
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//! ```
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//! let numbers = &[0, 1, 2];
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//! for n in numbers {
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//! println!("{} is a number!", n);
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//! }
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//! ```
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//!
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//! The mutable slice yields mutable references to the elements:
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//!
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//! ```
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//! let mut scores = [7, 8, 9];
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//! for score in &mut scores[..] {
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//! *score += 1;
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//! }
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//! ```
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//!
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//! This iterator yields mutable references to the slice's elements, so while
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//! the element type of the slice is `i32`, the element type of the iterator is
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//! `&mut i32`.
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//!
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//! * `.iter()` and `.iter_mut()` are the explicit methods to return the default
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//! iterators.
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//! * Further methods that return iterators are `.split()`, `.splitn()`,
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//! `.chunks()`, `.windows()` and more.
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//!
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//! *[See also the slice primitive type](../../std/primitive.slice.html).*
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#![stable(feature = "rust1", since = "1.0.0")]
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// Many of the usings in this module are only used in the test configuration.
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// It's cleaner to just turn off the unused_imports warning than to fix them.
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#![cfg_attr(test, allow(unused_imports, dead_code))]
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use alloc::boxed::Box;
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use core::cmp::Ordering::{self, Greater, Less};
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use core::cmp;
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use core::mem::size_of;
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use core::mem;
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use core::ptr;
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use core::slice as core_slice;
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use borrow::{Borrow, BorrowMut, ToOwned};
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use vec::Vec;
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use core::slice::{Chunks, Windows};
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use core::slice::{Iter, IterMut};
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use core::slice::{SplitMut, ChunksMut, Split};
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use core::slice::{SplitN, RSplitN, SplitNMut, RSplitNMut};
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use core::slice::{from_raw_parts, from_raw_parts_mut};
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////////////////////////////////////////////////////////////////////////////////
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// Basic slice extension methods
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////////////////////////////////////////////////////////////////////////////////
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// HACK(japaric) needed for the implementation of `vec!` macro during testing
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// NB see the hack module in this file for more details
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#[cfg(test)]
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pub use self::hack::into_vec;
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// HACK(japaric) needed for the implementation of `Vec::clone` during testing
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// NB see the hack module in this file for more details
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#[cfg(test)]
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pub use self::hack::to_vec;
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// HACK(japaric): With cfg(test) `impl [T]` is not available, these three
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// functions are actually methods that are in `impl [T]` but not in
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// `core::slice::SliceExt` - we need to supply these functions for the
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// `test_permutations` test
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mod hack {
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use alloc::boxed::Box;
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use core::mem;
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#[cfg(test)]
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use string::ToString;
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use vec::Vec;
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pub fn into_vec<T>(mut b: Box<[T]>) -> Vec<T> {
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unsafe {
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let xs = Vec::from_raw_parts(b.as_mut_ptr(), b.len(), b.len());
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mem::forget(b);
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xs
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}
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}
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#[inline]
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pub fn to_vec<T>(s: &[T]) -> Vec<T>
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where T: Clone
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{
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let mut vector = Vec::with_capacity(s.len());
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vector.extend_from_slice(s);
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vector
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}
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}
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#[lang = "slice"]
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#[cfg(not(test))]
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impl<T> [T] {
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/// Returns the number of elements in the slice.
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///
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/// # Example
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///
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/// ```
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/// let a = [1, 2, 3];
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/// assert_eq!(a.len(), 3);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn len(&self) -> usize {
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core_slice::SliceExt::len(self)
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}
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/// Returns true if the slice has a length of 0
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///
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/// # Example
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///
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/// ```
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/// let a = [1, 2, 3];
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/// assert!(!a.is_empty());
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_empty(&self) -> bool {
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core_slice::SliceExt::is_empty(self)
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}
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/// Returns the first element of a slice, or `None` if it is empty.
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///
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/// # Examples
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///
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/// ```
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/// let v = [10, 40, 30];
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/// assert_eq!(Some(&10), v.first());
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///
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/// let w: &[i32] = &[];
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/// assert_eq!(None, w.first());
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn first(&self) -> Option<&T> {
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core_slice::SliceExt::first(self)
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}
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/// Returns a mutable pointer to the first element of a slice, or `None` if it is empty.
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///
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/// # Examples
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///
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/// ```
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/// let x = &mut [0, 1, 2];
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///
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/// if let Some(first) = x.first_mut() {
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/// *first = 5;
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/// }
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/// assert_eq!(x, &[5, 1, 2]);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn first_mut(&mut self) -> Option<&mut T> {
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core_slice::SliceExt::first_mut(self)
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}
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/// Returns the first and all the rest of the elements of a slice.
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///
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/// # Examples
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///
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/// ```
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/// let x = &[0, 1, 2];
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///
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/// if let Some((first, elements)) = x.split_first() {
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/// assert_eq!(first, &0);
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/// assert_eq!(elements, &[1, 2]);
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/// }
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/// ```
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#[stable(feature = "slice_splits", since = "1.5.0")]
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#[inline]
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pub fn split_first(&self) -> Option<(&T, &[T])> {
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core_slice::SliceExt::split_first(self)
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}
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/// Returns the first and all the rest of the elements of a slice.
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///
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/// # Examples
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///
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/// ```
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/// let x = &mut [0, 1, 2];
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///
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/// if let Some((first, elements)) = x.split_first_mut() {
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/// *first = 3;
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/// elements[0] = 4;
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/// elements[1] = 5;
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/// }
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/// assert_eq!(x, &[3, 4, 5]);
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/// ```
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#[stable(feature = "slice_splits", since = "1.5.0")]
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#[inline]
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pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
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core_slice::SliceExt::split_first_mut(self)
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}
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/// Returns the last and all the rest of the elements of a slice.
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///
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/// # Examples
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///
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/// ```
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/// let x = &[0, 1, 2];
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///
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/// if let Some((last, elements)) = x.split_last() {
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/// assert_eq!(last, &2);
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/// assert_eq!(elements, &[0, 1]);
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/// }
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/// ```
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#[stable(feature = "slice_splits", since = "1.5.0")]
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#[inline]
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pub fn split_last(&self) -> Option<(&T, &[T])> {
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core_slice::SliceExt::split_last(self)
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}
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/// Returns the last and all the rest of the elements of a slice.
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///
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/// # Examples
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///
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/// ```
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/// let x = &mut [0, 1, 2];
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///
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/// if let Some((last, elements)) = x.split_last_mut() {
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/// *last = 3;
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/// elements[0] = 4;
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/// elements[1] = 5;
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/// }
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/// assert_eq!(x, &[4, 5, 3]);
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/// ```
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#[stable(feature = "slice_splits", since = "1.5.0")]
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#[inline]
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pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
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core_slice::SliceExt::split_last_mut(self)
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}
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/// Returns the last element of a slice, or `None` if it is empty.
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///
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/// # Examples
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///
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/// ```
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/// let v = [10, 40, 30];
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/// assert_eq!(Some(&30), v.last());
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///
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/// let w: &[i32] = &[];
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/// assert_eq!(None, w.last());
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn last(&self) -> Option<&T> {
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core_slice::SliceExt::last(self)
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}
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/// Returns a mutable pointer to the last item in the slice.
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///
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/// # Examples
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///
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/// ```
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/// let x = &mut [0, 1, 2];
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///
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/// if let Some(last) = x.last_mut() {
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/// *last = 10;
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/// }
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/// assert_eq!(x, &[0, 1, 10]);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn last_mut(&mut self) -> Option<&mut T> {
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core_slice::SliceExt::last_mut(self)
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}
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/// Returns the element of a slice at the given index, or `None` if the
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/// index is out of bounds.
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///
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/// # Examples
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///
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/// ```
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/// let v = [10, 40, 30];
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/// assert_eq!(Some(&40), v.get(1));
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/// assert_eq!(None, v.get(3));
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn get(&self, index: usize) -> Option<&T> {
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core_slice::SliceExt::get(self, index)
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}
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/// Returns a mutable reference to the element at the given index.
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///
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/// # Examples
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///
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/// ```
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/// let x = &mut [0, 1, 2];
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///
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/// if let Some(elem) = x.get_mut(1) {
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/// *elem = 42;
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/// }
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/// assert_eq!(x, &[0, 42, 2]);
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/// ```
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/// or `None` if the index is out of bounds
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn get_mut(&mut self, index: usize) -> Option<&mut T> {
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core_slice::SliceExt::get_mut(self, index)
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}
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/// Returns a pointer to the element at the given index, without doing
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/// bounds checking. So use it very carefully!
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///
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/// # Examples
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///
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/// ```
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/// let x = &[1, 2, 4];
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///
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/// unsafe {
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/// assert_eq!(x.get_unchecked(1), &2);
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/// }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub unsafe fn get_unchecked(&self, index: usize) -> &T {
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core_slice::SliceExt::get_unchecked(self, index)
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}
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/// Returns an unsafe mutable pointer to the element in index. So use it
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/// very carefully!
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///
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/// # Examples
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///
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/// ```
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/// let x = &mut [1, 2, 4];
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///
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/// unsafe {
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/// let elem = x.get_unchecked_mut(1);
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/// *elem = 13;
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/// }
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/// assert_eq!(x, &[1, 13, 4]);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut T {
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core_slice::SliceExt::get_unchecked_mut(self, index)
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}
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/// Returns an raw pointer to the slice's buffer
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///
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/// The caller must ensure that the slice outlives the pointer this
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/// function returns, or else it will end up pointing to garbage.
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///
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/// Modifying the slice may cause its buffer to be reallocated, which
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/// would also make any pointers to it invalid.
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///
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/// # Examples
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///
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/// ```
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/// let x = &[1, 2, 4];
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/// let x_ptr = x.as_ptr();
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///
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/// unsafe {
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/// for i in 0..x.len() {
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/// assert_eq!(x.get_unchecked(i), &*x_ptr.offset(i as isize));
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/// }
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/// }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn as_ptr(&self) -> *const T {
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core_slice::SliceExt::as_ptr(self)
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}
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/// Returns an unsafe mutable pointer to the slice's buffer.
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///
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/// The caller must ensure that the slice outlives the pointer this
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/// function returns, or else it will end up pointing to garbage.
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///
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/// Modifying the slice may cause its buffer to be reallocated, which
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/// would also make any pointers to it invalid.
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///
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/// # Examples
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///
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/// ```
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/// let x = &mut [1, 2, 4];
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/// let x_ptr = x.as_mut_ptr();
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///
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/// unsafe {
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/// for i in 0..x.len() {
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/// *x_ptr.offset(i as isize) += 2;
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/// }
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/// }
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/// assert_eq!(x, &[3, 4, 6]);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn as_mut_ptr(&mut self) -> *mut T {
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core_slice::SliceExt::as_mut_ptr(self)
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}
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/// Swaps two elements in a slice.
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///
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/// # Arguments
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///
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/// * a - The index of the first element
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/// * b - The index of the second element
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///
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/// # Panics
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///
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/// Panics if `a` or `b` are out of bounds.
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///
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/// # Examples
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///
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/// ```rust
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/// let mut v = ["a", "b", "c", "d"];
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/// v.swap(1, 3);
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/// assert!(v == ["a", "d", "c", "b"]);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn swap(&mut self, a: usize, b: usize) {
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core_slice::SliceExt::swap(self, a, b)
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}
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/// Reverse the order of elements in a slice, in place.
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///
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/// # Example
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///
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/// ```rust
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/// let mut v = [1, 2, 3];
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/// v.reverse();
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/// assert!(v == [3, 2, 1]);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn reverse(&mut self) {
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core_slice::SliceExt::reverse(self)
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}
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|
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/// Returns an iterator over the slice.
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///
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/// # Examples
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///
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/// ```
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/// let x = &[1, 2, 4];
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/// let mut iterator = x.iter();
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///
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/// assert_eq!(iterator.next(), Some(&1));
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/// assert_eq!(iterator.next(), Some(&2));
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/// assert_eq!(iterator.next(), Some(&4));
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/// assert_eq!(iterator.next(), None);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn iter(&self) -> Iter<T> {
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core_slice::SliceExt::iter(self)
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}
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/// Returns an iterator that allows modifying each value.
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///
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/// # Examples
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///
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|
/// ```
|
|
/// 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<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.
|
|
///
|
|
/// # Example
|
|
///
|
|
/// Print the adjacent pairs of a slice (i.e. `[1,2]`, `[2,3]`,
|
|
/// `[3,4]`):
|
|
///
|
|
/// ```rust
|
|
/// let v = &[1, 2, 3, 4];
|
|
/// for win in v.windows(2) {
|
|
/// println!("{:?}", win);
|
|
/// }
|
|
/// ```
|
|
#[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 `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
|
|
///
|
|
/// Print the slice two elements at a time (i.e. `[1,2]`,
|
|
/// `[3,4]`, `[5]`):
|
|
///
|
|
/// ```rust
|
|
/// let v = &[1, 2, 3, 4, 5];
|
|
///
|
|
/// for chunk in v.chunks(2) {
|
|
/// println!("{:?}", chunk);
|
|
/// }
|
|
/// ```
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
#[inline]
|
|
pub fn chunks(&self, size: usize) -> Chunks<T> {
|
|
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<T> {
|
|
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
|
|
///
|
|
/// ```rust
|
|
/// 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
|
|
///
|
|
/// Print the slice split by numbers divisible by 3 (i.e. `[10, 40]`,
|
|
/// `[20]`, `[50]`):
|
|
///
|
|
/// ```
|
|
/// let v = [10, 40, 30, 20, 60, 50];
|
|
///
|
|
/// for group in v.split(|num| *num % 3 == 0) {
|
|
/// println!("{:?}", group);
|
|
/// }
|
|
/// ```
|
|
#[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`, 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]));
|
|
/// ```
|
|
#[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]`.
|
|
///
|
|
/// ```rust
|
|
/// 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 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]`.
|
|
///
|
|
/// ```rust
|
|
/// 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<F>(&self, f: F) -> Result<usize, usize>
|
|
where F: FnMut(&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.
|
|
///
|
|
/// # 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]`.
|
|
///
|
|
/// ```rust
|
|
/// 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<B, F>(&self, b: &B, f: F) -> Result<usize, usize>
|
|
where F: FnMut(&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
|
|
/// approximately `2 * n` where `n` is the length of `self`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// 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 `key` to extract a key by which to
|
|
/// order the sort by.
|
|
///
|
|
/// This sort is stable and `O(n log n)` worst-case but allocates
|
|
/// approximately `2 * n`, where `n` is the length of `self`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// 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
|
|
{
|
|
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
|
|
/// approximately `2 * n`, where `n` is the length of `self`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// 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, 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
|
|
///
|
|
/// ```rust
|
|
/// 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
|
|
///
|
|
/// ```rust
|
|
/// 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<T>
|
|
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<Self>) -> Vec<T> {
|
|
// 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<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");
|
|
/// ```
|
|
#[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<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()
|
|
}
|
|
|
|
// 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<T> {
|
|
panic!("not available with cfg(test)")
|
|
}
|
|
}
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
// Sorting
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
fn insertion_sort<T, F>(v: &mut [T], mut compare: F)
|
|
where F: FnMut(&T, &T) -> Ordering
|
|
{
|
|
let len = v.len() as isize;
|
|
let buf_v = v.as_mut_ptr();
|
|
|
|
// 1 <= i < len;
|
|
for i in 1..len {
|
|
// j satisfies: 0 <= j <= i;
|
|
let mut j = i;
|
|
unsafe {
|
|
// `i` is in bounds.
|
|
let read_ptr = buf_v.offset(i) as *const T;
|
|
|
|
// find where to insert, we need to do strict <,
|
|
// rather than <=, to maintain stability.
|
|
|
|
// 0 <= j - 1 < len, so .offset(j - 1) is in bounds.
|
|
while j > 0 && compare(&*read_ptr, &*buf_v.offset(j - 1)) == Less {
|
|
j -= 1;
|
|
}
|
|
|
|
// shift everything to the right, to make space to
|
|
// insert this value.
|
|
|
|
// j + 1 could be `len` (for the last `i`), but in
|
|
// that case, `i == j` so we don't copy. The
|
|
// `.offset(j)` is always in bounds.
|
|
|
|
if i != j {
|
|
let tmp = ptr::read(read_ptr);
|
|
ptr::copy(&*buf_v.offset(j), buf_v.offset(j + 1), (i - j) as usize);
|
|
ptr::copy_nonoverlapping(&tmp, buf_v.offset(j), 1);
|
|
mem::forget(tmp);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn merge_sort<T, F>(v: &mut [T], mut compare: F)
|
|
where F: FnMut(&T, &T) -> Ordering
|
|
{
|
|
// warning: this wildly uses unsafe.
|
|
const BASE_INSERTION: usize = 32;
|
|
const LARGE_INSERTION: usize = 16;
|
|
|
|
// FIXME #12092: smaller insertion runs seems to make sorting
|
|
// vectors of large elements a little faster on some platforms,
|
|
// but hasn't been tested/tuned extensively
|
|
let insertion = if size_of::<T>() <= 16 {
|
|
BASE_INSERTION
|
|
} else {
|
|
LARGE_INSERTION
|
|
};
|
|
|
|
let len = v.len();
|
|
|
|
// short vectors get sorted in-place via insertion sort to avoid allocations
|
|
if len <= insertion {
|
|
insertion_sort(v, compare);
|
|
return;
|
|
}
|
|
|
|
// allocate some memory to use as scratch memory, we keep the
|
|
// length 0 so we can keep shallow copies of the contents of `v`
|
|
// without risking the dtors running on an object twice if
|
|
// `compare` panics.
|
|
let mut working_space = Vec::with_capacity(2 * len);
|
|
// these both are buffers of length `len`.
|
|
let mut buf_dat = working_space.as_mut_ptr();
|
|
let mut buf_tmp = unsafe { buf_dat.offset(len as isize) };
|
|
|
|
// length `len`.
|
|
let buf_v = v.as_ptr();
|
|
|
|
// step 1. sort short runs with insertion sort. This takes the
|
|
// values from `v` and sorts them into `buf_dat`, leaving that
|
|
// with sorted runs of length INSERTION.
|
|
|
|
// We could hardcode the sorting comparisons here, and we could
|
|
// manipulate/step the pointers themselves, rather than repeatedly
|
|
// .offset-ing.
|
|
for start in (0..len).step_by(insertion) {
|
|
// start <= i < len;
|
|
for i in start..cmp::min(start + insertion, len) {
|
|
// j satisfies: start <= j <= i;
|
|
let mut j = i as isize;
|
|
unsafe {
|
|
// `i` is in bounds.
|
|
let read_ptr = buf_v.offset(i as isize);
|
|
|
|
// find where to insert, we need to do strict <,
|
|
// rather than <=, to maintain stability.
|
|
|
|
// start <= j - 1 < len, so .offset(j - 1) is in
|
|
// bounds.
|
|
while j > start as isize && compare(&*read_ptr, &*buf_dat.offset(j - 1)) == Less {
|
|
j -= 1;
|
|
}
|
|
|
|
// shift everything to the right, to make space to
|
|
// insert this value.
|
|
|
|
// j + 1 could be `len` (for the last `i`), but in
|
|
// that case, `i == j` so we don't copy. The
|
|
// `.offset(j)` is always in bounds.
|
|
ptr::copy(&*buf_dat.offset(j), buf_dat.offset(j + 1), i - j as usize);
|
|
ptr::copy_nonoverlapping(read_ptr, buf_dat.offset(j), 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
// step 2. merge the sorted runs.
|
|
let mut width = insertion;
|
|
while width < len {
|
|
// merge the sorted runs of length `width` in `buf_dat` two at
|
|
// a time, placing the result in `buf_tmp`.
|
|
|
|
// 0 <= start <= len.
|
|
for start in (0..len).step_by(2 * width) {
|
|
// manipulate pointers directly for speed (rather than
|
|
// using a `for` loop with `range` and `.offset` inside
|
|
// that loop).
|
|
unsafe {
|
|
// the end of the first run & start of the
|
|
// second. Offset of `len` is defined, since this is
|
|
// precisely one byte past the end of the object.
|
|
let right_start = buf_dat.offset(cmp::min(start + width, len) as isize);
|
|
// end of the second. Similar reasoning to the above re safety.
|
|
let right_end_idx = cmp::min(start + 2 * width, len);
|
|
let right_end = buf_dat.offset(right_end_idx as isize);
|
|
|
|
// the pointers to the elements under consideration
|
|
// from the two runs.
|
|
|
|
// both of these are in bounds.
|
|
let mut left = buf_dat.offset(start as isize);
|
|
let mut right = right_start;
|
|
|
|
// where we're putting the results, it is a run of
|
|
// length `2*width`, so we step it once for each step
|
|
// of either `left` or `right`. `buf_tmp` has length
|
|
// `len`, so these are in bounds.
|
|
let mut out = buf_tmp.offset(start as isize);
|
|
let out_end = buf_tmp.offset(right_end_idx as isize);
|
|
|
|
// If left[last] <= right[0], they are already in order:
|
|
// fast-forward the left side (the right side is handled
|
|
// in the loop).
|
|
// If `right` is not empty then left is not empty, and
|
|
// the offsets are in bounds.
|
|
if right != right_end && compare(&*right.offset(-1), &*right) != Greater {
|
|
let elems = (right_start as usize - left as usize) / mem::size_of::<T>();
|
|
ptr::copy_nonoverlapping(&*left, out, elems);
|
|
out = out.offset(elems as isize);
|
|
left = right_start;
|
|
}
|
|
|
|
while out < out_end {
|
|
// Either the left or the right run are exhausted,
|
|
// so just copy the remainder from the other run
|
|
// and move on; this gives a huge speed-up (order
|
|
// of 25%) for mostly sorted vectors (the best
|
|
// case).
|
|
if left == right_start {
|
|
// the number remaining in this run.
|
|
let elems = (right_end as usize - right as usize) / mem::size_of::<T>();
|
|
ptr::copy_nonoverlapping(&*right, out, elems);
|
|
break;
|
|
} else if right == right_end {
|
|
let elems = (right_start as usize - left as usize) / mem::size_of::<T>();
|
|
ptr::copy_nonoverlapping(&*left, out, elems);
|
|
break;
|
|
}
|
|
|
|
// check which side is smaller, and that's the
|
|
// next element for the new run.
|
|
|
|
// `left < right_start` and `right < right_end`,
|
|
// so these are valid.
|
|
let to_copy = if compare(&*left, &*right) == Greater {
|
|
step(&mut right)
|
|
} else {
|
|
step(&mut left)
|
|
};
|
|
ptr::copy_nonoverlapping(&*to_copy, out, 1);
|
|
step(&mut out);
|
|
}
|
|
}
|
|
}
|
|
|
|
mem::swap(&mut buf_dat, &mut buf_tmp);
|
|
|
|
width *= 2;
|
|
}
|
|
|
|
// write the result to `v` in one go, so that there are never two copies
|
|
// of the same object in `v`.
|
|
unsafe {
|
|
ptr::copy_nonoverlapping(&*buf_dat, v.as_mut_ptr(), len);
|
|
}
|
|
|
|
// increment the pointer, returning the old pointer.
|
|
#[inline(always)]
|
|
unsafe fn step<T>(ptr: &mut *mut T) -> *mut T {
|
|
let old = *ptr;
|
|
*ptr = ptr.offset(1);
|
|
old
|
|
}
|
|
}
|