1 // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! A dynamically-sized view into a contiguous sequence, `[T]`.
13 //! Slices are a view into a block of memory represented as a pointer and a
18 //! let vec = vec![1, 2, 3];
19 //! let int_slice = &vec[..];
20 //! // coercing an array to a slice
21 //! let str_slice: &[&str] = &["one", "two", "three"];
24 //! Slices are either mutable or shared. The shared slice type is `&[T]`,
25 //! while the mutable slice type is `&mut [T]`, where `T` represents the element
26 //! type. For example, you can mutate the block of memory that a mutable slice
30 //! let x = &mut [1, 2, 3];
32 //! assert_eq!(x, &[1, 7, 3]);
35 //! Here are some of the things this module contains:
39 //! There are several structs that are useful for slices, such as [`Iter`], which
40 //! represents iteration over a slice.
42 //! ## Trait Implementations
44 //! There are several implementations of common traits for slices. Some examples
48 //! * [`Eq`], [`Ord`] - for slices whose element type are [`Eq`] or [`Ord`].
49 //! * [`Hash`] - for slices whose element type is [`Hash`].
53 //! The slices implement `IntoIterator`. The iterator yields references to the
57 //! let numbers = &[0, 1, 2];
58 //! for n in numbers {
59 //! println!("{} is a number!", n);
63 //! The mutable slice yields mutable references to the elements:
66 //! let mut scores = [7, 8, 9];
67 //! for score in &mut scores[..] {
72 //! This iterator yields mutable references to the slice's elements, so while
73 //! the element type of the slice is `i32`, the element type of the iterator is
76 //! * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default
78 //! * Further methods that return iterators are [`.split`], [`.splitn`],
79 //! [`.chunks`], [`.windows`] and more.
81 //! *[See also the slice primitive type](../../std/primitive.slice.html).*
83 //! [`Clone`]: ../../std/clone/trait.Clone.html
84 //! [`Eq`]: ../../std/cmp/trait.Eq.html
85 //! [`Ord`]: ../../std/cmp/trait.Ord.html
86 //! [`Iter`]: struct.Iter.html
87 //! [`Hash`]: ../../std/hash/trait.Hash.html
88 //! [`.iter`]: ../../std/primitive.slice.html#method.iter
89 //! [`.iter_mut`]: ../../std/primitive.slice.html#method.iter_mut
90 //! [`.split`]: ../../std/primitive.slice.html#method.split
91 //! [`.splitn`]: ../../std/primitive.slice.html#method.splitn
92 //! [`.chunks`]: ../../std/primitive.slice.html#method.chunks
93 //! [`.windows`]: ../../std/primitive.slice.html#method.windows
94 #![stable(feature = "rust1", since = "1.0.0")]
96 // Many of the usings in this module are only used in the test configuration.
97 // It's cleaner to just turn off the unused_imports warning than to fix them.
98 #![cfg_attr(test, allow(unused_imports, dead_code))]
100 use alloc
::boxed
::Box
;
101 use core
::cmp
::Ordering
::{self, Less}
;
102 use core
::mem
::size_of
;
105 use core
::slice
as core_slice
;
107 use borrow
::{Borrow, BorrowMut, ToOwned}
;
110 #[stable(feature = "rust1", since = "1.0.0")]
111 pub use core
::slice
::{Chunks, Windows}
;
112 #[stable(feature = "rust1", since = "1.0.0")]
113 pub use core
::slice
::{Iter, IterMut}
;
114 #[stable(feature = "rust1", since = "1.0.0")]
115 pub use core
::slice
::{SplitMut, ChunksMut, Split}
;
116 #[stable(feature = "rust1", since = "1.0.0")]
117 pub use core
::slice
::{SplitN, RSplitN, SplitNMut, RSplitNMut}
;
118 #[unstable(feature = "slice_rsplit", issue = "41020")]
119 pub use core
::slice
::{RSplit, RSplitMut}
;
120 #[stable(feature = "rust1", since = "1.0.0")]
121 pub use core
::slice
::{from_raw_parts, from_raw_parts_mut}
;
122 #[unstable(feature = "slice_get_slice", issue = "35729")]
123 pub use core
::slice
::SliceIndex
;
125 ////////////////////////////////////////////////////////////////////////////////
126 // Basic slice extension methods
127 ////////////////////////////////////////////////////////////////////////////////
129 // HACK(japaric) needed for the implementation of `vec!` macro during testing
130 // NB see the hack module in this file for more details
132 pub use self::hack
::into_vec
;
134 // HACK(japaric) needed for the implementation of `Vec::clone` during testing
135 // NB see the hack module in this file for more details
137 pub use self::hack
::to_vec
;
139 // HACK(japaric): With cfg(test) `impl [T]` is not available, these three
140 // functions are actually methods that are in `impl [T]` but not in
141 // `core::slice::SliceExt` - we need to supply these functions for the
142 // `test_permutations` test
144 use alloc
::boxed
::Box
;
148 use string
::ToString
;
151 pub fn into_vec
<T
>(mut b
: Box
<[T
]>) -> Vec
<T
> {
153 let xs
= Vec
::from_raw_parts(b
.as_mut_ptr(), b
.len(), b
.len());
160 pub fn to_vec
<T
>(s
: &[T
]) -> Vec
<T
>
163 let mut vector
= Vec
::with_capacity(s
.len());
164 vector
.extend_from_slice(s
);
172 /// Returns the number of elements in the slice.
177 /// let a = [1, 2, 3];
178 /// assert_eq!(a.len(), 3);
180 #[stable(feature = "rust1", since = "1.0.0")]
182 pub fn len(&self) -> usize {
183 core_slice
::SliceExt
::len(self)
186 /// Returns `true` if the slice has a length of 0.
191 /// let a = [1, 2, 3];
192 /// assert!(!a.is_empty());
194 #[stable(feature = "rust1", since = "1.0.0")]
196 pub fn is_empty(&self) -> bool
{
197 core_slice
::SliceExt
::is_empty(self)
200 /// Returns the first element of the slice, or `None` if it is empty.
205 /// let v = [10, 40, 30];
206 /// assert_eq!(Some(&10), v.first());
208 /// let w: &[i32] = &[];
209 /// assert_eq!(None, w.first());
211 #[stable(feature = "rust1", since = "1.0.0")]
213 pub fn first(&self) -> Option
<&T
> {
214 core_slice
::SliceExt
::first(self)
217 /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
222 /// let x = &mut [0, 1, 2];
224 /// if let Some(first) = x.first_mut() {
227 /// assert_eq!(x, &[5, 1, 2]);
229 #[stable(feature = "rust1", since = "1.0.0")]
231 pub fn first_mut(&mut self) -> Option
<&mut T
> {
232 core_slice
::SliceExt
::first_mut(self)
235 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
240 /// let x = &[0, 1, 2];
242 /// if let Some((first, elements)) = x.split_first() {
243 /// assert_eq!(first, &0);
244 /// assert_eq!(elements, &[1, 2]);
247 #[stable(feature = "slice_splits", since = "1.5.0")]
249 pub fn split_first(&self) -> Option
<(&T
, &[T
])> {
250 core_slice
::SliceExt
::split_first(self)
253 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
258 /// let x = &mut [0, 1, 2];
260 /// if let Some((first, elements)) = x.split_first_mut() {
265 /// assert_eq!(x, &[3, 4, 5]);
267 #[stable(feature = "slice_splits", since = "1.5.0")]
269 pub fn split_first_mut(&mut self) -> Option
<(&mut T
, &mut [T
])> {
270 core_slice
::SliceExt
::split_first_mut(self)
273 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
278 /// let x = &[0, 1, 2];
280 /// if let Some((last, elements)) = x.split_last() {
281 /// assert_eq!(last, &2);
282 /// assert_eq!(elements, &[0, 1]);
285 #[stable(feature = "slice_splits", since = "1.5.0")]
287 pub fn split_last(&self) -> Option
<(&T
, &[T
])> {
288 core_slice
::SliceExt
::split_last(self)
292 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
297 /// let x = &mut [0, 1, 2];
299 /// if let Some((last, elements)) = x.split_last_mut() {
304 /// assert_eq!(x, &[4, 5, 3]);
306 #[stable(feature = "slice_splits", since = "1.5.0")]
308 pub fn split_last_mut(&mut self) -> Option
<(&mut T
, &mut [T
])> {
309 core_slice
::SliceExt
::split_last_mut(self)
312 /// Returns the last element of the slice, or `None` if it is empty.
317 /// let v = [10, 40, 30];
318 /// assert_eq!(Some(&30), v.last());
320 /// let w: &[i32] = &[];
321 /// assert_eq!(None, w.last());
323 #[stable(feature = "rust1", since = "1.0.0")]
325 pub fn last(&self) -> Option
<&T
> {
326 core_slice
::SliceExt
::last(self)
329 /// Returns a mutable pointer to the last item in the slice.
334 /// let x = &mut [0, 1, 2];
336 /// if let Some(last) = x.last_mut() {
339 /// assert_eq!(x, &[0, 1, 10]);
341 #[stable(feature = "rust1", since = "1.0.0")]
343 pub fn last_mut(&mut self) -> Option
<&mut T
> {
344 core_slice
::SliceExt
::last_mut(self)
347 /// Returns a reference to an element or subslice depending on the type of
350 /// - If given a position, returns a reference to the element at that
351 /// position or `None` if out of bounds.
352 /// - If given a range, returns the subslice corresponding to that range,
353 /// or `None` if out of bounds.
358 /// let v = [10, 40, 30];
359 /// assert_eq!(Some(&40), v.get(1));
360 /// assert_eq!(Some(&[10, 40][..]), v.get(0..2));
361 /// assert_eq!(None, v.get(3));
362 /// assert_eq!(None, v.get(0..4));
364 #[stable(feature = "rust1", since = "1.0.0")]
366 pub fn get
<I
>(&self, index
: I
) -> Option
<&I
::Output
>
367 where I
: SliceIndex
<Self>
369 core_slice
::SliceExt
::get(self, index
)
372 /// Returns a mutable reference to an element or subslice depending on the
373 /// type of index (see [`get`]) or `None` if the index is out of bounds.
375 /// [`get`]: #method.get
380 /// let x = &mut [0, 1, 2];
382 /// if let Some(elem) = x.get_mut(1) {
385 /// assert_eq!(x, &[0, 42, 2]);
387 #[stable(feature = "rust1", since = "1.0.0")]
389 pub fn get_mut
<I
>(&mut self, index
: I
) -> Option
<&mut I
::Output
>
390 where I
: SliceIndex
<Self>
392 core_slice
::SliceExt
::get_mut(self, index
)
395 /// Returns a reference to an element or subslice, without doing bounds
396 /// checking. So use it very carefully!
401 /// let x = &[1, 2, 4];
404 /// assert_eq!(x.get_unchecked(1), &2);
407 #[stable(feature = "rust1", since = "1.0.0")]
409 pub unsafe fn get_unchecked
<I
>(&self, index
: I
) -> &I
::Output
410 where I
: SliceIndex
<Self>
412 core_slice
::SliceExt
::get_unchecked(self, index
)
415 /// Returns a mutable reference to an element or subslice, without doing
416 /// bounds checking. So use it very carefully!
421 /// let x = &mut [1, 2, 4];
424 /// let elem = x.get_unchecked_mut(1);
427 /// assert_eq!(x, &[1, 13, 4]);
429 #[stable(feature = "rust1", since = "1.0.0")]
431 pub unsafe fn get_unchecked_mut
<I
>(&mut self, index
: I
) -> &mut I
::Output
432 where I
: SliceIndex
<Self>
434 core_slice
::SliceExt
::get_unchecked_mut(self, index
)
437 /// Returns a raw pointer to the slice's buffer.
439 /// The caller must ensure that the slice outlives the pointer this
440 /// function returns, or else it will end up pointing to garbage.
442 /// Modifying the container referenced by this slice may cause its buffer
443 /// to be reallocated, which would also make any pointers to it invalid.
448 /// let x = &[1, 2, 4];
449 /// let x_ptr = x.as_ptr();
452 /// for i in 0..x.len() {
453 /// assert_eq!(x.get_unchecked(i), &*x_ptr.offset(i as isize));
457 #[stable(feature = "rust1", since = "1.0.0")]
459 pub fn as_ptr(&self) -> *const T
{
460 core_slice
::SliceExt
::as_ptr(self)
463 /// Returns an unsafe mutable pointer to the slice's buffer.
465 /// The caller must ensure that the slice outlives the pointer this
466 /// function returns, or else it will end up pointing to garbage.
468 /// Modifying the container referenced by this slice may cause its buffer
469 /// to be reallocated, which would also make any pointers to it invalid.
474 /// let x = &mut [1, 2, 4];
475 /// let x_ptr = x.as_mut_ptr();
478 /// for i in 0..x.len() {
479 /// *x_ptr.offset(i as isize) += 2;
482 /// assert_eq!(x, &[3, 4, 6]);
484 #[stable(feature = "rust1", since = "1.0.0")]
486 pub fn as_mut_ptr(&mut self) -> *mut T
{
487 core_slice
::SliceExt
::as_mut_ptr(self)
490 /// Swaps two elements in the slice.
494 /// * a - The index of the first element
495 /// * b - The index of the second element
499 /// Panics if `a` or `b` are out of bounds.
504 /// let mut v = ["a", "b", "c", "d"];
506 /// assert!(v == ["a", "d", "c", "b"]);
508 #[stable(feature = "rust1", since = "1.0.0")]
510 pub fn swap(&mut self, a
: usize, b
: usize) {
511 core_slice
::SliceExt
::swap(self, a
, b
)
514 /// Reverses the order of elements in the slice, in place.
519 /// let mut v = [1, 2, 3];
521 /// assert!(v == [3, 2, 1]);
523 #[stable(feature = "rust1", since = "1.0.0")]
525 pub fn reverse(&mut self) {
526 core_slice
::SliceExt
::reverse(self)
529 /// Returns an iterator over the slice.
534 /// let x = &[1, 2, 4];
535 /// let mut iterator = x.iter();
537 /// assert_eq!(iterator.next(), Some(&1));
538 /// assert_eq!(iterator.next(), Some(&2));
539 /// assert_eq!(iterator.next(), Some(&4));
540 /// assert_eq!(iterator.next(), None);
542 #[stable(feature = "rust1", since = "1.0.0")]
544 pub fn iter(&self) -> Iter
<T
> {
545 core_slice
::SliceExt
::iter(self)
548 /// Returns an iterator that allows modifying each value.
553 /// let x = &mut [1, 2, 4];
554 /// for elem in x.iter_mut() {
557 /// assert_eq!(x, &[3, 4, 6]);
559 #[stable(feature = "rust1", since = "1.0.0")]
561 pub fn iter_mut(&mut self) -> IterMut
<T
> {
562 core_slice
::SliceExt
::iter_mut(self)
565 /// Returns an iterator over all contiguous windows of length
566 /// `size`. The windows overlap. If the slice is shorter than
567 /// `size`, the iterator returns no values.
571 /// Panics if `size` is 0.
576 /// let slice = ['r', 'u', 's', 't'];
577 /// let mut iter = slice.windows(2);
578 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
579 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
580 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
581 /// assert!(iter.next().is_none());
584 /// If the slice is shorter than `size`:
587 /// let slice = ['f', 'o', 'o'];
588 /// let mut iter = slice.windows(4);
589 /// assert!(iter.next().is_none());
591 #[stable(feature = "rust1", since = "1.0.0")]
593 pub fn windows(&self, size
: usize) -> Windows
<T
> {
594 core_slice
::SliceExt
::windows(self, size
)
597 /// Returns an iterator over `size` elements of the slice at a
598 /// time. The chunks are slices and do not overlap. If `size` does
599 /// not divide the length of the slice, then the last chunk will
600 /// not have length `size`.
604 /// Panics if `size` is 0.
609 /// let slice = ['l', 'o', 'r', 'e', 'm'];
610 /// let mut iter = slice.chunks(2);
611 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
612 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
613 /// assert_eq!(iter.next().unwrap(), &['m']);
614 /// assert!(iter.next().is_none());
616 #[stable(feature = "rust1", since = "1.0.0")]
618 pub fn chunks(&self, size
: usize) -> Chunks
<T
> {
619 core_slice
::SliceExt
::chunks(self, size
)
622 /// Returns an iterator over `chunk_size` elements of the slice at a time.
623 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
624 /// not divide the length of the slice, then the last chunk will not
625 /// have length `chunk_size`.
629 /// Panics if `chunk_size` is 0.
634 /// let v = &mut [0, 0, 0, 0, 0];
635 /// let mut count = 1;
637 /// for chunk in v.chunks_mut(2) {
638 /// for elem in chunk.iter_mut() {
643 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
645 #[stable(feature = "rust1", since = "1.0.0")]
647 pub fn chunks_mut(&mut self, chunk_size
: usize) -> ChunksMut
<T
> {
648 core_slice
::SliceExt
::chunks_mut(self, chunk_size
)
651 /// Divides one slice into two at an index.
653 /// The first will contain all indices from `[0, mid)` (excluding
654 /// the index `mid` itself) and the second will contain all
655 /// indices from `[mid, len)` (excluding the index `len` itself).
659 /// Panics if `mid > len`.
664 /// let v = [10, 40, 30, 20, 50];
665 /// let (v1, v2) = v.split_at(2);
666 /// assert_eq!([10, 40], v1);
667 /// assert_eq!([30, 20, 50], v2);
669 #[stable(feature = "rust1", since = "1.0.0")]
671 pub fn split_at(&self, mid
: usize) -> (&[T
], &[T
]) {
672 core_slice
::SliceExt
::split_at(self, mid
)
675 /// Divides one `&mut` into two at an index.
677 /// The first will contain all indices from `[0, mid)` (excluding
678 /// the index `mid` itself) and the second will contain all
679 /// indices from `[mid, len)` (excluding the index `len` itself).
683 /// Panics if `mid > len`.
688 /// let mut v = [1, 2, 3, 4, 5, 6];
690 /// // scoped to restrict the lifetime of the borrows
692 /// let (left, right) = v.split_at_mut(0);
693 /// assert!(left == []);
694 /// assert!(right == [1, 2, 3, 4, 5, 6]);
698 /// let (left, right) = v.split_at_mut(2);
699 /// assert!(left == [1, 2]);
700 /// assert!(right == [3, 4, 5, 6]);
704 /// let (left, right) = v.split_at_mut(6);
705 /// assert!(left == [1, 2, 3, 4, 5, 6]);
706 /// assert!(right == []);
709 #[stable(feature = "rust1", since = "1.0.0")]
711 pub fn split_at_mut(&mut self, mid
: usize) -> (&mut [T
], &mut [T
]) {
712 core_slice
::SliceExt
::split_at_mut(self, mid
)
715 /// Returns an iterator over subslices separated by elements that match
716 /// `pred`. The matched element is not contained in the subslices.
721 /// let slice = [10, 40, 33, 20];
722 /// let mut iter = slice.split(|num| num % 3 == 0);
724 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
725 /// assert_eq!(iter.next().unwrap(), &[20]);
726 /// assert!(iter.next().is_none());
729 /// If the first element is matched, an empty slice will be the first item
730 /// returned by the iterator. Similarly, if the last element in the slice
731 /// is matched, an empty slice will be the last item returned by the
735 /// let slice = [10, 40, 33];
736 /// let mut iter = slice.split(|num| num % 3 == 0);
738 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
739 /// assert_eq!(iter.next().unwrap(), &[]);
740 /// assert!(iter.next().is_none());
743 /// If two matched elements are directly adjacent, an empty slice will be
744 /// present between them:
747 /// let slice = [10, 6, 33, 20];
748 /// let mut iter = slice.split(|num| num % 3 == 0);
750 /// assert_eq!(iter.next().unwrap(), &[10]);
751 /// assert_eq!(iter.next().unwrap(), &[]);
752 /// assert_eq!(iter.next().unwrap(), &[20]);
753 /// assert!(iter.next().is_none());
755 #[stable(feature = "rust1", since = "1.0.0")]
757 pub fn split
<F
>(&self, pred
: F
) -> Split
<T
, F
>
758 where F
: FnMut(&T
) -> bool
760 core_slice
::SliceExt
::split(self, pred
)
763 /// Returns an iterator over mutable subslices separated by elements that
764 /// match `pred`. The matched element is not contained in the subslices.
769 /// let mut v = [10, 40, 30, 20, 60, 50];
771 /// for group in v.split_mut(|num| *num % 3 == 0) {
774 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
776 #[stable(feature = "rust1", since = "1.0.0")]
778 pub fn split_mut
<F
>(&mut self, pred
: F
) -> SplitMut
<T
, F
>
779 where F
: FnMut(&T
) -> bool
781 core_slice
::SliceExt
::split_mut(self, pred
)
784 /// Returns an iterator over subslices separated by elements that match
785 /// `pred`, starting at the end of the slice and working backwards.
786 /// The matched element is not contained in the subslices.
791 /// #![feature(slice_rsplit)]
793 /// let slice = [11, 22, 33, 0, 44, 55];
794 /// let mut iter = slice.rsplit(|num| *num == 0);
796 /// assert_eq!(iter.next().unwrap(), &[44, 55]);
797 /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
798 /// assert_eq!(iter.next(), None);
801 /// As with `split()`, if the first or last element is matched, an empty
802 /// slice will be the first (or last) item returned by the iterator.
805 /// #![feature(slice_rsplit)]
807 /// let v = &[0, 1, 1, 2, 3, 5, 8];
808 /// let mut it = v.rsplit(|n| *n % 2 == 0);
809 /// assert_eq!(it.next().unwrap(), &[]);
810 /// assert_eq!(it.next().unwrap(), &[3, 5]);
811 /// assert_eq!(it.next().unwrap(), &[1, 1]);
812 /// assert_eq!(it.next().unwrap(), &[]);
813 /// assert_eq!(it.next(), None);
815 #[unstable(feature = "slice_rsplit", issue = "41020")]
817 pub fn rsplit
<F
>(&self, pred
: F
) -> RSplit
<T
, F
>
818 where F
: FnMut(&T
) -> bool
820 core_slice
::SliceExt
::rsplit(self, pred
)
823 /// Returns an iterator over mutable subslices separated by elements that
824 /// match `pred`, starting at the end of the slice and working
825 /// backwards. The matched element is not contained in the subslices.
830 /// #![feature(slice_rsplit)]
832 /// let mut v = [100, 400, 300, 200, 600, 500];
834 /// let mut count = 0;
835 /// for group in v.rsplit_mut(|num| *num % 3 == 0) {
837 /// group[0] = count;
839 /// assert_eq!(v, [3, 400, 300, 2, 600, 1]);
842 #[unstable(feature = "slice_rsplit", issue = "41020")]
844 pub fn rsplit_mut
<F
>(&mut self, pred
: F
) -> RSplitMut
<T
, F
>
845 where F
: FnMut(&T
) -> bool
847 core_slice
::SliceExt
::rsplit_mut(self, pred
)
850 /// Returns an iterator over subslices separated by elements that match
851 /// `pred`, limited to returning at most `n` items. The matched element is
852 /// not contained in the subslices.
854 /// The last element returned, if any, will contain the remainder of the
859 /// Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`,
863 /// let v = [10, 40, 30, 20, 60, 50];
865 /// for group in v.splitn(2, |num| *num % 3 == 0) {
866 /// println!("{:?}", group);
869 #[stable(feature = "rust1", since = "1.0.0")]
871 pub fn splitn
<F
>(&self, n
: usize, pred
: F
) -> SplitN
<T
, F
>
872 where F
: FnMut(&T
) -> bool
874 core_slice
::SliceExt
::splitn(self, n
, pred
)
877 /// Returns an iterator over subslices separated by elements that match
878 /// `pred`, limited to returning at most `n` items. The matched element is
879 /// not contained in the subslices.
881 /// The last element returned, if any, will contain the remainder of the
887 /// let mut v = [10, 40, 30, 20, 60, 50];
889 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
892 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
894 #[stable(feature = "rust1", since = "1.0.0")]
896 pub fn splitn_mut
<F
>(&mut self, n
: usize, pred
: F
) -> SplitNMut
<T
, F
>
897 where F
: FnMut(&T
) -> bool
899 core_slice
::SliceExt
::splitn_mut(self, n
, pred
)
902 /// Returns an iterator over subslices separated by elements that match
903 /// `pred` limited to returning at most `n` items. This starts at the end of
904 /// the slice and works backwards. The matched element is not contained in
907 /// The last element returned, if any, will contain the remainder of the
912 /// Print the slice split once, starting from the end, by numbers divisible
913 /// by 3 (i.e. `[50]`, `[10, 40, 30, 20]`):
916 /// let v = [10, 40, 30, 20, 60, 50];
918 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
919 /// println!("{:?}", group);
922 #[stable(feature = "rust1", since = "1.0.0")]
924 pub fn rsplitn
<F
>(&self, n
: usize, pred
: F
) -> RSplitN
<T
, F
>
925 where F
: FnMut(&T
) -> bool
927 core_slice
::SliceExt
::rsplitn(self, n
, pred
)
930 /// Returns an iterator over subslices separated by elements that match
931 /// `pred` limited to returning at most `n` items. This starts at the end of
932 /// the slice and works backwards. The matched element is not contained in
935 /// The last element returned, if any, will contain the remainder of the
941 /// let mut s = [10, 40, 30, 20, 60, 50];
943 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
946 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
948 #[stable(feature = "rust1", since = "1.0.0")]
950 pub fn rsplitn_mut
<F
>(&mut self, n
: usize, pred
: F
) -> RSplitNMut
<T
, F
>
951 where F
: FnMut(&T
) -> bool
953 core_slice
::SliceExt
::rsplitn_mut(self, n
, pred
)
956 /// Returns `true` if the slice contains an element with the given value.
961 /// let v = [10, 40, 30];
962 /// assert!(v.contains(&30));
963 /// assert!(!v.contains(&50));
965 #[stable(feature = "rust1", since = "1.0.0")]
966 pub fn contains(&self, x
: &T
) -> bool
969 core_slice
::SliceExt
::contains(self, x
)
972 /// Returns `true` if `needle` is a prefix of the slice.
977 /// let v = [10, 40, 30];
978 /// assert!(v.starts_with(&[10]));
979 /// assert!(v.starts_with(&[10, 40]));
980 /// assert!(!v.starts_with(&[50]));
981 /// assert!(!v.starts_with(&[10, 50]));
984 /// Always returns `true` if `needle` is an empty slice:
987 /// let v = &[10, 40, 30];
988 /// assert!(v.starts_with(&[]));
989 /// let v: &[u8] = &[];
990 /// assert!(v.starts_with(&[]));
992 #[stable(feature = "rust1", since = "1.0.0")]
993 pub fn starts_with(&self, needle
: &[T
]) -> bool
996 core_slice
::SliceExt
::starts_with(self, needle
)
999 /// Returns `true` if `needle` is a suffix of the slice.
1004 /// let v = [10, 40, 30];
1005 /// assert!(v.ends_with(&[30]));
1006 /// assert!(v.ends_with(&[40, 30]));
1007 /// assert!(!v.ends_with(&[50]));
1008 /// assert!(!v.ends_with(&[50, 30]));
1011 /// Always returns `true` if `needle` is an empty slice:
1014 /// let v = &[10, 40, 30];
1015 /// assert!(v.ends_with(&[]));
1016 /// let v: &[u8] = &[];
1017 /// assert!(v.ends_with(&[]));
1019 #[stable(feature = "rust1", since = "1.0.0")]
1020 pub fn ends_with(&self, needle
: &[T
]) -> bool
1023 core_slice
::SliceExt
::ends_with(self, needle
)
1026 /// Binary searches this sorted slice for a given element.
1028 /// If the value is found then `Ok` is returned, containing the
1029 /// index of the matching element; if the value is not found then
1030 /// `Err` is returned, containing the index where a matching
1031 /// element could be inserted while maintaining sorted order.
1035 /// Looks up a series of four elements. The first is found, with a
1036 /// uniquely determined position; the second and third are not
1037 /// found; the fourth could match any position in `[1, 4]`.
1040 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1042 /// assert_eq!(s.binary_search(&13), Ok(9));
1043 /// assert_eq!(s.binary_search(&4), Err(7));
1044 /// assert_eq!(s.binary_search(&100), Err(13));
1045 /// let r = s.binary_search(&1);
1046 /// assert!(match r { Ok(1...4) => true, _ => false, });
1048 #[stable(feature = "rust1", since = "1.0.0")]
1049 pub fn binary_search(&self, x
: &T
) -> Result
<usize, usize>
1052 core_slice
::SliceExt
::binary_search(self, x
)
1055 /// Binary searches this sorted slice with a comparator function.
1057 /// The comparator function should implement an order consistent
1058 /// with the sort order of the underlying slice, returning an
1059 /// order code that indicates whether its argument is `Less`,
1060 /// `Equal` or `Greater` the desired target.
1062 /// If a matching value is found then returns `Ok`, containing
1063 /// the index for the matched element; if no match is found then
1064 /// `Err` is returned, containing the index where a matching
1065 /// element could be inserted while maintaining sorted order.
1069 /// Looks up a series of four elements. The first is found, with a
1070 /// uniquely determined position; the second and third are not
1071 /// found; the fourth could match any position in `[1, 4]`.
1074 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1077 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
1079 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
1081 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
1083 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
1084 /// assert!(match r { Ok(1...4) => true, _ => false, });
1086 #[stable(feature = "rust1", since = "1.0.0")]
1088 pub fn binary_search_by
<'a
, F
>(&'a
self, f
: F
) -> Result
<usize, usize>
1089 where F
: FnMut(&'a T
) -> Ordering
1091 core_slice
::SliceExt
::binary_search_by(self, f
)
1094 /// Binary searches this sorted slice with a key extraction function.
1096 /// Assumes that the slice is sorted by the key, for instance with
1097 /// [`sort_by_key`] using the same key extraction function.
1099 /// If a matching value is found then returns `Ok`, containing the
1100 /// index for the matched element; if no match is found then `Err`
1101 /// is returned, containing the index where a matching element could
1102 /// be inserted while maintaining sorted order.
1104 /// [`sort_by_key`]: #method.sort_by_key
1108 /// Looks up a series of four elements in a slice of pairs sorted by
1109 /// their second elements. The first is found, with a uniquely
1110 /// determined position; the second and third are not found; the
1111 /// fourth could match any position in `[1, 4]`.
1114 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
1115 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
1116 /// (1, 21), (2, 34), (4, 55)];
1118 /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9));
1119 /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7));
1120 /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
1121 /// let r = s.binary_search_by_key(&1, |&(a,b)| b);
1122 /// assert!(match r { Ok(1...4) => true, _ => false, });
1124 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
1126 pub fn binary_search_by_key
<'a
, B
, F
>(&'a
self, b
: &B
, f
: F
) -> Result
<usize, usize>
1127 where F
: FnMut(&'a T
) -> B
,
1130 core_slice
::SliceExt
::binary_search_by_key(self, b
, f
)
1133 /// Sorts the slice.
1135 /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
1137 /// # Current implementation
1139 /// The current algorithm is an adaptive, iterative merge sort inspired by
1140 /// [timsort](https://en.wikipedia.org/wiki/Timsort).
1141 /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
1142 /// two or more sorted sequences concatenated one after another.
1144 /// Also, it allocates temporary storage half the size of `self`, but for short slices a
1145 /// non-allocating insertion sort is used instead.
1150 /// let mut v = [-5, 4, 1, -3, 2];
1153 /// assert!(v == [-5, -3, 1, 2, 4]);
1155 #[stable(feature = "rust1", since = "1.0.0")]
1157 pub fn sort(&mut self)
1160 merge_sort(self, |a
, b
| a
.lt(b
));
1163 /// Sorts the slice with a comparator function.
1165 /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
1167 /// # Current implementation
1169 /// The current algorithm is an adaptive, iterative merge sort inspired by
1170 /// [timsort](https://en.wikipedia.org/wiki/Timsort).
1171 /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
1172 /// two or more sorted sequences concatenated one after another.
1174 /// Also, it allocates temporary storage half the size of `self`, but for short slices a
1175 /// non-allocating insertion sort is used instead.
1180 /// let mut v = [5, 4, 1, 3, 2];
1181 /// v.sort_by(|a, b| a.cmp(b));
1182 /// assert!(v == [1, 2, 3, 4, 5]);
1184 /// // reverse sorting
1185 /// v.sort_by(|a, b| b.cmp(a));
1186 /// assert!(v == [5, 4, 3, 2, 1]);
1188 #[stable(feature = "rust1", since = "1.0.0")]
1190 pub fn sort_by
<F
>(&mut self, mut compare
: F
)
1191 where F
: FnMut(&T
, &T
) -> Ordering
1193 merge_sort(self, |a
, b
| compare(a
, b
) == Less
);
1196 /// Sorts the slice with a key extraction function.
1198 /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
1200 /// # Current implementation
1202 /// The current algorithm is an adaptive, iterative merge sort inspired by
1203 /// [timsort](https://en.wikipedia.org/wiki/Timsort).
1204 /// It is designed to be very fast in cases where the slice is nearly sorted, or consists of
1205 /// two or more sorted sequences concatenated one after another.
1207 /// Also, it allocates temporary storage half the size of `self`, but for short slices a
1208 /// non-allocating insertion sort is used instead.
1213 /// let mut v = [-5i32, 4, 1, -3, 2];
1215 /// v.sort_by_key(|k| k.abs());
1216 /// assert!(v == [1, 2, -3, 4, -5]);
1218 #[stable(feature = "slice_sort_by_key", since = "1.7.0")]
1220 pub fn sort_by_key
<B
, F
>(&mut self, mut f
: F
)
1221 where F
: FnMut(&T
) -> B
, B
: Ord
1223 merge_sort(self, |a
, b
| f(a
).lt(&f(b
)));
1226 /// Sorts the slice, but may not preserve the order of equal elements.
1228 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1229 /// and `O(n log n)` worst-case.
1231 /// # Current implementation
1233 /// The current algorithm is based on Orson Peters' [pattern-defeating quicksort][pdqsort],
1234 /// which is a quicksort variant designed to be very fast on certain kinds of patterns,
1235 /// sometimes achieving linear time. It is randomized but deterministic, and falls back to
1236 /// heapsort on degenerate inputs.
1238 /// It is generally faster than stable sorting, except in a few special cases, e.g. when the
1239 /// slice consists of several concatenated sorted sequences.
1244 /// #![feature(sort_unstable)]
1246 /// let mut v = [-5, 4, 1, -3, 2];
1248 /// v.sort_unstable();
1249 /// assert!(v == [-5, -3, 1, 2, 4]);
1252 /// [pdqsort]: https://github.com/orlp/pdqsort
1253 // FIXME #40585: Mention `sort_unstable` in the documentation for `sort`.
1254 #[unstable(feature = "sort_unstable", issue = "40585")]
1256 pub fn sort_unstable(&mut self)
1259 core_slice
::SliceExt
::sort_unstable(self);
1262 /// Sorts the slice with a comparator function, but may not preserve the order of equal
1265 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1266 /// and `O(n log n)` worst-case.
1268 /// # Current implementation
1270 /// The current algorithm is based on Orson Peters' [pattern-defeating quicksort][pdqsort],
1271 /// which is a quicksort variant designed to be very fast on certain kinds of patterns,
1272 /// sometimes achieving linear time. It is randomized but deterministic, and falls back to
1273 /// heapsort on degenerate inputs.
1275 /// It is generally faster than stable sorting, except in a few special cases, e.g. when the
1276 /// slice consists of several concatenated sorted sequences.
1281 /// #![feature(sort_unstable)]
1283 /// let mut v = [5, 4, 1, 3, 2];
1284 /// v.sort_unstable_by(|a, b| a.cmp(b));
1285 /// assert!(v == [1, 2, 3, 4, 5]);
1287 /// // reverse sorting
1288 /// v.sort_unstable_by(|a, b| b.cmp(a));
1289 /// assert!(v == [5, 4, 3, 2, 1]);
1292 /// [pdqsort]: https://github.com/orlp/pdqsort
1293 // FIXME #40585: Mention `sort_unstable_by` in the documentation for `sort_by`.
1294 #[unstable(feature = "sort_unstable", issue = "40585")]
1296 pub fn sort_unstable_by
<F
>(&mut self, compare
: F
)
1297 where F
: FnMut(&T
, &T
) -> Ordering
1299 core_slice
::SliceExt
::sort_unstable_by(self, compare
);
1302 /// Sorts the slice with a key extraction function, but may not preserve the order of equal
1305 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1306 /// and `O(n log n)` worst-case.
1308 /// # Current implementation
1310 /// The current algorithm is based on Orson Peters' [pattern-defeating quicksort][pdqsort],
1311 /// which is a quicksort variant designed to be very fast on certain kinds of patterns,
1312 /// sometimes achieving linear time. It is randomized but deterministic, and falls back to
1313 /// heapsort on degenerate inputs.
1315 /// It is generally faster than stable sorting, except in a few special cases, e.g. when the
1316 /// slice consists of several concatenated sorted sequences.
1321 /// #![feature(sort_unstable)]
1323 /// let mut v = [-5i32, 4, 1, -3, 2];
1325 /// v.sort_unstable_by_key(|k| k.abs());
1326 /// assert!(v == [1, 2, -3, 4, -5]);
1329 /// [pdqsort]: https://github.com/orlp/pdqsort
1330 // FIXME #40585: Mention `sort_unstable_by_key` in the documentation for `sort_by_key`.
1331 #[unstable(feature = "sort_unstable", issue = "40585")]
1333 pub fn sort_unstable_by_key
<B
, F
>(&mut self, f
: F
)
1334 where F
: FnMut(&T
) -> B
,
1337 core_slice
::SliceExt
::sort_unstable_by_key(self, f
);
1340 /// Copies the elements from `src` into `self`.
1342 /// The length of `src` must be the same as `self`.
1346 /// This function will panic if the two slices have different lengths.
1351 /// let mut dst = [0, 0, 0];
1352 /// let src = [1, 2, 3];
1354 /// dst.clone_from_slice(&src);
1355 /// assert!(dst == [1, 2, 3]);
1357 #[stable(feature = "clone_from_slice", since = "1.7.0")]
1358 pub fn clone_from_slice(&mut self, src
: &[T
]) where T
: Clone
{
1359 core_slice
::SliceExt
::clone_from_slice(self, src
)
1362 /// Copies all elements from `src` into `self`, using a memcpy.
1364 /// The length of `src` must be the same as `self`.
1368 /// This function will panic if the two slices have different lengths.
1373 /// let mut dst = [0, 0, 0];
1374 /// let src = [1, 2, 3];
1376 /// dst.copy_from_slice(&src);
1377 /// assert_eq!(src, dst);
1379 #[stable(feature = "copy_from_slice", since = "1.9.0")]
1380 pub fn copy_from_slice(&mut self, src
: &[T
]) where T
: Copy
{
1381 core_slice
::SliceExt
::copy_from_slice(self, src
)
1384 /// Copies `self` into a new `Vec`.
1389 /// let s = [10, 40, 30];
1390 /// let x = s.to_vec();
1391 /// // Here, `s` and `x` can be modified independently.
1393 #[stable(feature = "rust1", since = "1.0.0")]
1395 pub fn to_vec(&self) -> Vec
<T
>
1398 // NB see hack module in this file
1402 /// Converts `self` into a vector without clones or allocation.
1407 /// let s: Box<[i32]> = Box::new([10, 40, 30]);
1408 /// let x = s.into_vec();
1409 /// // `s` cannot be used anymore because it has been converted into `x`.
1411 /// assert_eq!(x, vec![10, 40, 30]);
1413 #[stable(feature = "rust1", since = "1.0.0")]
1415 pub fn into_vec(self: Box
<Self>) -> Vec
<T
> {
1416 // NB see hack module in this file
1417 hack
::into_vec(self)
1421 ////////////////////////////////////////////////////////////////////////////////
1422 // Extension traits for slices over specific kinds of data
1423 ////////////////////////////////////////////////////////////////////////////////
1424 #[unstable(feature = "slice_concat_ext",
1425 reason
= "trait should not have to exist",
1427 /// An extension trait for concatenating slices
1428 pub trait SliceConcatExt
<T
: ?Sized
> {
1429 #[unstable(feature = "slice_concat_ext",
1430 reason
= "trait should not have to exist",
1432 /// The resulting type after concatenation
1435 /// Flattens a slice of `T` into a single value `Self::Output`.
1440 /// assert_eq!(["hello", "world"].concat(), "helloworld");
1442 #[stable(feature = "rust1", since = "1.0.0")]
1443 fn concat(&self) -> Self::Output
;
1445 /// Flattens a slice of `T` into a single value `Self::Output`, placing a
1446 /// given separator between each.
1451 /// assert_eq!(["hello", "world"].join(" "), "hello world");
1453 #[stable(feature = "rename_connect_to_join", since = "1.3.0")]
1454 fn join(&self, sep
: &T
) -> Self::Output
;
1456 #[stable(feature = "rust1", since = "1.0.0")]
1457 #[rustc_deprecated(since = "1.3.0", reason = "renamed to join")]
1458 fn connect(&self, sep
: &T
) -> Self::Output
;
1461 #[unstable(feature = "slice_concat_ext",
1462 reason
= "trait should not have to exist",
1464 impl<T
: Clone
, V
: Borrow
<[T
]>> SliceConcatExt
<T
> for [V
] {
1465 type Output
= Vec
<T
>;
1467 fn concat(&self) -> Vec
<T
> {
1468 let size
= self.iter().fold(0, |acc
, v
| acc
+ v
.borrow().len());
1469 let mut result
= Vec
::with_capacity(size
);
1471 result
.extend_from_slice(v
.borrow())
1476 fn join(&self, sep
: &T
) -> Vec
<T
> {
1477 let size
= self.iter().fold(0, |acc
, v
| acc
+ v
.borrow().len());
1478 let mut result
= Vec
::with_capacity(size
+ self.len());
1479 let mut first
= true;
1484 result
.push(sep
.clone())
1486 result
.extend_from_slice(v
.borrow())
1491 fn connect(&self, sep
: &T
) -> Vec
<T
> {
1496 ////////////////////////////////////////////////////////////////////////////////
1497 // Standard trait implementations for slices
1498 ////////////////////////////////////////////////////////////////////////////////
1500 #[stable(feature = "rust1", since = "1.0.0")]
1501 impl<T
> Borrow
<[T
]> for Vec
<T
> {
1502 fn borrow(&self) -> &[T
] {
1507 #[stable(feature = "rust1", since = "1.0.0")]
1508 impl<T
> BorrowMut
<[T
]> for Vec
<T
> {
1509 fn borrow_mut(&mut self) -> &mut [T
] {
1514 #[stable(feature = "rust1", since = "1.0.0")]
1515 impl<T
: Clone
> ToOwned
for [T
] {
1516 type Owned
= Vec
<T
>;
1518 fn to_owned(&self) -> Vec
<T
> {
1522 // HACK(japaric): with cfg(test) the inherent `[T]::to_vec`, which is required for this method
1523 // definition, is not available. Since we don't require this method for testing purposes, I'll
1525 // NB see the slice::hack module in slice.rs for more information
1527 fn to_owned(&self) -> Vec
<T
> {
1528 panic
!("not available with cfg(test)")
1531 fn clone_into(&self, target
: &mut Vec
<T
>) {
1532 // drop anything in target that will not be overwritten
1533 target
.truncate(self.len());
1534 let len
= target
.len();
1536 // reuse the contained values' allocations/resources.
1537 target
.clone_from_slice(&self[..len
]);
1539 // target.len <= self.len due to the truncate above, so the
1540 // slice here is always in-bounds.
1541 target
.extend_from_slice(&self[len
..]);
1545 ////////////////////////////////////////////////////////////////////////////////
1547 ////////////////////////////////////////////////////////////////////////////////
1549 /// Inserts `v[0]` into pre-sorted sequence `v[1..]` so that whole `v[..]` becomes sorted.
1551 /// This is the integral subroutine of insertion sort.
1552 fn insert_head
<T
, F
>(v
: &mut [T
], is_less
: &mut F
)
1553 where F
: FnMut(&T
, &T
) -> bool
1555 if v
.len() >= 2 && is_less(&v
[1], &v
[0]) {
1557 // There are three ways to implement insertion here:
1559 // 1. Swap adjacent elements until the first one gets to its final destination.
1560 // However, this way we copy data around more than is necessary. If elements are big
1561 // structures (costly to copy), this method will be slow.
1563 // 2. Iterate until the right place for the first element is found. Then shift the
1564 // elements succeeding it to make room for it and finally place it into the
1565 // remaining hole. This is a good method.
1567 // 3. Copy the first element into a temporary variable. Iterate until the right place
1568 // for it is found. As we go along, copy every traversed element into the slot
1569 // preceding it. Finally, copy data from the temporary variable into the remaining
1570 // hole. This method is very good. Benchmarks demonstrated slightly better
1571 // performance than with the 2nd method.
1573 // All methods were benchmarked, and the 3rd showed best results. So we chose that one.
1574 let mut tmp
= mem
::ManuallyDrop
::new(ptr
::read(&v
[0]));
1576 // Intermediate state of the insertion process is always tracked by `hole`, which
1577 // serves two purposes:
1578 // 1. Protects integrity of `v` from panics in `is_less`.
1579 // 2. Fills the remaining hole in `v` in the end.
1583 // If `is_less` panics at any point during the process, `hole` will get dropped and
1584 // fill the hole in `v` with `tmp`, thus ensuring that `v` still holds every object it
1585 // initially held exactly once.
1586 let mut hole
= InsertionHole
{
1590 ptr
::copy_nonoverlapping(&v
[1], &mut v
[0], 1);
1592 for i
in 2..v
.len() {
1593 if !is_less(&v
[i
], &*tmp
) {
1596 ptr
::copy_nonoverlapping(&v
[i
], &mut v
[i
- 1], 1);
1597 hole
.dest
= &mut v
[i
];
1599 // `hole` gets dropped and thus copies `tmp` into the remaining hole in `v`.
1603 // When dropped, copies from `src` into `dest`.
1604 struct InsertionHole
<T
> {
1609 impl<T
> Drop
for InsertionHole
<T
> {
1610 fn drop(&mut self) {
1611 unsafe { ptr::copy_nonoverlapping(self.src, self.dest, 1); }
1616 /// Merges non-decreasing runs `v[..mid]` and `v[mid..]` using `buf` as temporary storage, and
1617 /// stores the result into `v[..]`.
1621 /// The two slices must be non-empty and `mid` must be in bounds. Buffer `buf` must be long enough
1622 /// to hold a copy of the shorter slice. Also, `T` must not be a zero-sized type.
1623 unsafe fn merge
<T
, F
>(v
: &mut [T
], mid
: usize, buf
: *mut T
, is_less
: &mut F
)
1624 where F
: FnMut(&T
, &T
) -> bool
1627 let v
= v
.as_mut_ptr();
1628 let v_mid
= v
.offset(mid
as isize);
1629 let v_end
= v
.offset(len
as isize);
1631 // The merge process first copies the shorter run into `buf`. Then it traces the newly copied
1632 // run and the longer run forwards (or backwards), comparing their next unconsumed elements and
1633 // copying the lesser (or greater) one into `v`.
1635 // As soon as the shorter run is fully consumed, the process is done. If the longer run gets
1636 // consumed first, then we must copy whatever is left of the shorter run into the remaining
1639 // Intermediate state of the process is always tracked by `hole`, which serves two purposes:
1640 // 1. Protects integrity of `v` from panics in `is_less`.
1641 // 2. Fills the remaining hole in `v` if the longer run gets consumed first.
1645 // If `is_less` panics at any point during the process, `hole` will get dropped and fill the
1646 // hole in `v` with the unconsumed range in `buf`, thus ensuring that `v` still holds every
1647 // object it initially held exactly once.
1650 if mid
<= len
- mid
{
1651 // The left run is shorter.
1652 ptr
::copy_nonoverlapping(v
, buf
, mid
);
1655 end
: buf
.offset(mid
as isize),
1659 // Initially, these pointers point to the beginnings of their arrays.
1660 let left
= &mut hole
.start
;
1661 let mut right
= v_mid
;
1662 let out
= &mut hole
.dest
;
1664 while *left
< hole
.end
&& right
< v_end
{
1665 // Consume the lesser side.
1666 // If equal, prefer the left run to maintain stability.
1667 let to_copy
= if is_less(&*right
, &**left
) {
1668 get_and_increment(&mut right
)
1670 get_and_increment(left
)
1672 ptr
::copy_nonoverlapping(to_copy
, get_and_increment(out
), 1);
1675 // The right run is shorter.
1676 ptr
::copy_nonoverlapping(v_mid
, buf
, len
- mid
);
1679 end
: buf
.offset((len
- mid
) as isize),
1683 // Initially, these pointers point past the ends of their arrays.
1684 let left
= &mut hole
.dest
;
1685 let right
= &mut hole
.end
;
1686 let mut out
= v_end
;
1688 while v
< *left
&& buf
< *right
{
1689 // Consume the greater side.
1690 // If equal, prefer the right run to maintain stability.
1691 let to_copy
= if is_less(&*right
.offset(-1), &*left
.offset(-1)) {
1692 decrement_and_get(left
)
1694 decrement_and_get(right
)
1696 ptr
::copy_nonoverlapping(to_copy
, decrement_and_get(&mut out
), 1);
1699 // Finally, `hole` gets dropped. If the shorter run was not fully consumed, whatever remains of
1700 // it will now be copied into the hole in `v`.
1702 unsafe fn get_and_increment
<T
>(ptr
: &mut *mut T
) -> *mut T
{
1704 *ptr
= ptr
.offset(1);
1708 unsafe fn decrement_and_get
<T
>(ptr
: &mut *mut T
) -> *mut T
{
1709 *ptr
= ptr
.offset(-1);
1713 // When dropped, copies the range `start..end` into `dest..`.
1714 struct MergeHole
<T
> {
1720 impl<T
> Drop
for MergeHole
<T
> {
1721 fn drop(&mut self) {
1722 // `T` is not a zero-sized type, so it's okay to divide by it's size.
1723 let len
= (self.end
as usize - self.start
as usize) / mem
::size_of
::<T
>();
1724 unsafe { ptr::copy_nonoverlapping(self.start, self.dest, len); }
1729 /// This merge sort borrows some (but not all) ideas from TimSort, which is described in detail
1730 /// [here](http://svn.python.org/projects/python/trunk/Objects/listsort.txt).
1732 /// The algorithm identifies strictly descending and non-descending subsequences, which are called
1733 /// natural runs. There is a stack of pending runs yet to be merged. Each newly found run is pushed
1734 /// onto the stack, and then some pairs of adjacent runs are merged until these two invariants are
1737 /// 1. for every `i` in `1..runs.len()`: `runs[i - 1].len > runs[i].len`
1738 /// 2. for every `i` in `2..runs.len()`: `runs[i - 2].len > runs[i - 1].len + runs[i].len`
1740 /// The invariants ensure that the total running time is `O(n log n)` worst-case.
1741 fn merge_sort
<T
, F
>(v
: &mut [T
], mut is_less
: F
)
1742 where F
: FnMut(&T
, &T
) -> bool
1744 // Slices of up to this length get sorted using insertion sort.
1745 const MAX_INSERTION
: usize = 20;
1746 // Very short runs are extended using insertion sort to span at least this many elements.
1747 const MIN_RUN
: usize = 10;
1749 // Sorting has no meaningful behavior on zero-sized types.
1750 if size_of
::<T
>() == 0 {
1756 // Short arrays get sorted in-place via insertion sort to avoid allocations.
1757 if len
<= MAX_INSERTION
{
1759 for i
in (0..len
-1).rev() {
1760 insert_head(&mut v
[i
..], &mut is_less
);
1766 // Allocate a buffer to use as scratch memory. We keep the length 0 so we can keep in it
1767 // shallow copies of the contents of `v` without risking the dtors running on copies if
1768 // `is_less` panics. When merging two sorted runs, this buffer holds a copy of the shorter run,
1769 // which will always have length at most `len / 2`.
1770 let mut buf
= Vec
::with_capacity(len
/ 2);
1772 // In order to identify natural runs in `v`, we traverse it backwards. That might seem like a
1773 // strange decision, but consider the fact that merges more often go in the opposite direction
1774 // (forwards). According to benchmarks, merging forwards is slightly faster than merging
1775 // backwards. To conclude, identifying runs by traversing backwards improves performance.
1776 let mut runs
= vec
![];
1779 // Find the next natural run, and reverse it if it's strictly descending.
1780 let mut start
= end
- 1;
1784 if is_less(v
.get_unchecked(start
+ 1), v
.get_unchecked(start
)) {
1785 while start
> 0 && is_less(v
.get_unchecked(start
),
1786 v
.get_unchecked(start
- 1)) {
1789 v
[start
..end
].reverse();
1791 while start
> 0 && !is_less(v
.get_unchecked(start
),
1792 v
.get_unchecked(start
- 1)) {
1799 // Insert some more elements into the run if it's too short. Insertion sort is faster than
1800 // merge sort on short sequences, so this significantly improves performance.
1801 while start
> 0 && end
- start
< MIN_RUN
{
1803 insert_head(&mut v
[start
..end
], &mut is_less
);
1806 // Push this run onto the stack.
1813 // Merge some pairs of adjacent runs to satisfy the invariants.
1814 while let Some(r
) = collapse(&runs
) {
1815 let left
= runs
[r
+ 1];
1816 let right
= runs
[r
];
1818 merge(&mut v
[left
.start
.. right
.start
+ right
.len
], left
.len
, buf
.as_mut_ptr(),
1823 len
: left
.len
+ right
.len
,
1829 // Finally, exactly one run must remain in the stack.
1830 debug_assert
!(runs
.len() == 1 && runs
[0].start
== 0 && runs
[0].len
== len
);
1832 // Examines the stack of runs and identifies the next pair of runs to merge. More specifically,
1833 // if `Some(r)` is returned, that means `runs[r]` and `runs[r + 1]` must be merged next. If the
1834 // algorithm should continue building a new run instead, `None` is returned.
1836 // TimSort is infamous for it's buggy implementations, as described here:
1837 // http://envisage-project.eu/timsort-specification-and-verification/
1839 // The gist of the story is: we must enforce the invariants on the top four runs on the stack.
1840 // Enforcing them on just top three is not sufficient to ensure that the invariants will still
1841 // hold for *all* runs in the stack.
1843 // This function correctly checks invariants for the top four runs. Additionally, if the top
1844 // run starts at index 0, it will always demand a merge operation until the stack is fully
1845 // collapsed, in order to complete the sort.
1847 fn collapse(runs
: &[Run
]) -> Option
<usize> {
1849 if n
>= 2 && (runs
[n
- 1].start
== 0 ||
1850 runs
[n
- 2].len
<= runs
[n
- 1].len
||
1851 (n
>= 3 && runs
[n
- 3].len
<= runs
[n
- 2].len
+ runs
[n
- 1].len
) ||
1852 (n
>= 4 && runs
[n
- 4].len
<= runs
[n
- 3].len
+ runs
[n
- 2].len
)) {
1853 if n
>= 3 && runs
[n
- 3].len
< runs
[n
- 1].len
{
1863 #[derive(Clone, Copy)]