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, Greater, Less}
;
103 use core
::mem
::size_of
;
106 use core
::slice
as core_slice
;
108 use borrow
::{Borrow, BorrowMut, ToOwned}
;
111 #[stable(feature = "rust1", since = "1.0.0")]
112 pub use core
::slice
::{Chunks, Windows}
;
113 #[stable(feature = "rust1", since = "1.0.0")]
114 pub use core
::slice
::{Iter, IterMut}
;
115 #[stable(feature = "rust1", since = "1.0.0")]
116 pub use core
::slice
::{SplitMut, ChunksMut, Split}
;
117 #[stable(feature = "rust1", since = "1.0.0")]
118 pub use core
::slice
::{SplitN, RSplitN, SplitNMut, RSplitNMut}
;
119 #[stable(feature = "rust1", since = "1.0.0")]
120 pub use core
::slice
::{from_raw_parts, from_raw_parts_mut}
;
122 ////////////////////////////////////////////////////////////////////////////////
123 // Basic slice extension methods
124 ////////////////////////////////////////////////////////////////////////////////
126 // HACK(japaric) needed for the implementation of `vec!` macro during testing
127 // NB see the hack module in this file for more details
129 pub use self::hack
::into_vec
;
131 // HACK(japaric) needed for the implementation of `Vec::clone` during testing
132 // NB see the hack module in this file for more details
134 pub use self::hack
::to_vec
;
136 // HACK(japaric): With cfg(test) `impl [T]` is not available, these three
137 // functions are actually methods that are in `impl [T]` but not in
138 // `core::slice::SliceExt` - we need to supply these functions for the
139 // `test_permutations` test
141 use alloc
::boxed
::Box
;
145 use string
::ToString
;
148 pub fn into_vec
<T
>(mut b
: Box
<[T
]>) -> Vec
<T
> {
150 let xs
= Vec
::from_raw_parts(b
.as_mut_ptr(), b
.len(), b
.len());
157 pub fn to_vec
<T
>(s
: &[T
]) -> Vec
<T
>
160 let mut vector
= Vec
::with_capacity(s
.len());
161 vector
.extend_from_slice(s
);
169 /// Returns the number of elements in the slice.
174 /// let a = [1, 2, 3];
175 /// assert_eq!(a.len(), 3);
177 #[stable(feature = "rust1", since = "1.0.0")]
179 pub fn len(&self) -> usize {
180 core_slice
::SliceExt
::len(self)
183 /// Returns true if the slice has a length of 0.
188 /// let a = [1, 2, 3];
189 /// assert!(!a.is_empty());
191 #[stable(feature = "rust1", since = "1.0.0")]
193 pub fn is_empty(&self) -> bool
{
194 core_slice
::SliceExt
::is_empty(self)
197 /// Returns the first element of a slice, or `None` if it is empty.
202 /// let v = [10, 40, 30];
203 /// assert_eq!(Some(&10), v.first());
205 /// let w: &[i32] = &[];
206 /// assert_eq!(None, w.first());
208 #[stable(feature = "rust1", since = "1.0.0")]
210 pub fn first(&self) -> Option
<&T
> {
211 core_slice
::SliceExt
::first(self)
214 /// Returns a mutable pointer to the first element of a slice, or `None` if it is empty.
219 /// let x = &mut [0, 1, 2];
221 /// if let Some(first) = x.first_mut() {
224 /// assert_eq!(x, &[5, 1, 2]);
226 #[stable(feature = "rust1", since = "1.0.0")]
228 pub fn first_mut(&mut self) -> Option
<&mut T
> {
229 core_slice
::SliceExt
::first_mut(self)
232 /// Returns the first and all the rest of the elements of a slice.
237 /// let x = &[0, 1, 2];
239 /// if let Some((first, elements)) = x.split_first() {
240 /// assert_eq!(first, &0);
241 /// assert_eq!(elements, &[1, 2]);
244 #[stable(feature = "slice_splits", since = "1.5.0")]
246 pub fn split_first(&self) -> Option
<(&T
, &[T
])> {
247 core_slice
::SliceExt
::split_first(self)
250 /// Returns the first and all the rest of the elements of a slice.
255 /// let x = &mut [0, 1, 2];
257 /// if let Some((first, elements)) = x.split_first_mut() {
262 /// assert_eq!(x, &[3, 4, 5]);
264 #[stable(feature = "slice_splits", since = "1.5.0")]
266 pub fn split_first_mut(&mut self) -> Option
<(&mut T
, &mut [T
])> {
267 core_slice
::SliceExt
::split_first_mut(self)
270 /// Returns the last and all the rest of the elements of a slice.
275 /// let x = &[0, 1, 2];
277 /// if let Some((last, elements)) = x.split_last() {
278 /// assert_eq!(last, &2);
279 /// assert_eq!(elements, &[0, 1]);
282 #[stable(feature = "slice_splits", since = "1.5.0")]
284 pub fn split_last(&self) -> Option
<(&T
, &[T
])> {
285 core_slice
::SliceExt
::split_last(self)
289 /// Returns the last and all the rest of the elements of a slice.
294 /// let x = &mut [0, 1, 2];
296 /// if let Some((last, elements)) = x.split_last_mut() {
301 /// assert_eq!(x, &[4, 5, 3]);
303 #[stable(feature = "slice_splits", since = "1.5.0")]
305 pub fn split_last_mut(&mut self) -> Option
<(&mut T
, &mut [T
])> {
306 core_slice
::SliceExt
::split_last_mut(self)
309 /// Returns the last element of a slice, or `None` if it is empty.
314 /// let v = [10, 40, 30];
315 /// assert_eq!(Some(&30), v.last());
317 /// let w: &[i32] = &[];
318 /// assert_eq!(None, w.last());
320 #[stable(feature = "rust1", since = "1.0.0")]
322 pub fn last(&self) -> Option
<&T
> {
323 core_slice
::SliceExt
::last(self)
326 /// Returns a mutable pointer to the last item in the slice.
331 /// let x = &mut [0, 1, 2];
333 /// if let Some(last) = x.last_mut() {
336 /// assert_eq!(x, &[0, 1, 10]);
338 #[stable(feature = "rust1", since = "1.0.0")]
340 pub fn last_mut(&mut self) -> Option
<&mut T
> {
341 core_slice
::SliceExt
::last_mut(self)
344 /// Returns the element of a slice at the given index, or `None` if the
345 /// index is out of bounds.
350 /// let v = [10, 40, 30];
351 /// assert_eq!(Some(&40), v.get(1));
352 /// assert_eq!(None, v.get(3));
354 #[stable(feature = "rust1", since = "1.0.0")]
356 pub fn get(&self, index
: usize) -> Option
<&T
> {
357 core_slice
::SliceExt
::get(self, index
)
360 /// Returns a mutable reference to the element at the given index.
365 /// let x = &mut [0, 1, 2];
367 /// if let Some(elem) = x.get_mut(1) {
370 /// assert_eq!(x, &[0, 42, 2]);
372 /// or `None` if the index is out of bounds
373 #[stable(feature = "rust1", since = "1.0.0")]
375 pub fn get_mut(&mut self, index
: usize) -> Option
<&mut T
> {
376 core_slice
::SliceExt
::get_mut(self, index
)
379 /// Returns a pointer to the element at the given index, without doing
380 /// bounds checking. So use it very carefully!
385 /// let x = &[1, 2, 4];
388 /// assert_eq!(x.get_unchecked(1), &2);
391 #[stable(feature = "rust1", since = "1.0.0")]
393 pub unsafe fn get_unchecked(&self, index
: usize) -> &T
{
394 core_slice
::SliceExt
::get_unchecked(self, index
)
397 /// Returns an unsafe mutable pointer to the element in index. So use it
403 /// let x = &mut [1, 2, 4];
406 /// let elem = x.get_unchecked_mut(1);
409 /// assert_eq!(x, &[1, 13, 4]);
411 #[stable(feature = "rust1", since = "1.0.0")]
413 pub unsafe fn get_unchecked_mut(&mut self, index
: usize) -> &mut T
{
414 core_slice
::SliceExt
::get_unchecked_mut(self, index
)
417 /// Returns an raw pointer to the slice's buffer.
419 /// The caller must ensure that the slice outlives the pointer this
420 /// function returns, or else it will end up pointing to garbage.
422 /// Modifying the slice may cause its buffer to be reallocated, which
423 /// would also make any pointers to it invalid.
428 /// let x = &[1, 2, 4];
429 /// let x_ptr = x.as_ptr();
432 /// for i in 0..x.len() {
433 /// assert_eq!(x.get_unchecked(i), &*x_ptr.offset(i as isize));
437 #[stable(feature = "rust1", since = "1.0.0")]
439 pub fn as_ptr(&self) -> *const T
{
440 core_slice
::SliceExt
::as_ptr(self)
443 /// Returns an unsafe mutable pointer to the slice's buffer.
445 /// The caller must ensure that the slice outlives the pointer this
446 /// function returns, or else it will end up pointing to garbage.
448 /// Modifying the slice may cause its buffer to be reallocated, which
449 /// would also make any pointers to it invalid.
454 /// let x = &mut [1, 2, 4];
455 /// let x_ptr = x.as_mut_ptr();
458 /// for i in 0..x.len() {
459 /// *x_ptr.offset(i as isize) += 2;
462 /// assert_eq!(x, &[3, 4, 6]);
464 #[stable(feature = "rust1", since = "1.0.0")]
466 pub fn as_mut_ptr(&mut self) -> *mut T
{
467 core_slice
::SliceExt
::as_mut_ptr(self)
470 /// Swaps two elements in a slice.
474 /// * a - The index of the first element
475 /// * b - The index of the second element
479 /// Panics if `a` or `b` are out of bounds.
484 /// let mut v = ["a", "b", "c", "d"];
486 /// assert!(v == ["a", "d", "c", "b"]);
488 #[stable(feature = "rust1", since = "1.0.0")]
490 pub fn swap(&mut self, a
: usize, b
: usize) {
491 core_slice
::SliceExt
::swap(self, a
, b
)
494 /// Reverse the order of elements in a slice, in place.
499 /// let mut v = [1, 2, 3];
501 /// assert!(v == [3, 2, 1]);
503 #[stable(feature = "rust1", since = "1.0.0")]
505 pub fn reverse(&mut self) {
506 core_slice
::SliceExt
::reverse(self)
509 /// Returns an iterator over the slice.
514 /// let x = &[1, 2, 4];
515 /// let mut iterator = x.iter();
517 /// assert_eq!(iterator.next(), Some(&1));
518 /// assert_eq!(iterator.next(), Some(&2));
519 /// assert_eq!(iterator.next(), Some(&4));
520 /// assert_eq!(iterator.next(), None);
522 #[stable(feature = "rust1", since = "1.0.0")]
524 pub fn iter(&self) -> Iter
<T
> {
525 core_slice
::SliceExt
::iter(self)
528 /// Returns an iterator that allows modifying each value.
533 /// let x = &mut [1, 2, 4];
535 /// let iterator = x.iter_mut();
537 /// for elem in iterator {
541 /// assert_eq!(x, &[3, 4, 6]);
543 #[stable(feature = "rust1", since = "1.0.0")]
545 pub fn iter_mut(&mut self) -> IterMut
<T
> {
546 core_slice
::SliceExt
::iter_mut(self)
549 /// Returns an iterator over all contiguous windows of length
550 /// `size`. The windows overlap. If the slice is shorter than
551 /// `size`, the iterator returns no values.
555 /// Panics if `size` is 0.
560 /// let slice = ['r', 'u', 's', 't'];
561 /// let mut iter = slice.windows(2);
562 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
563 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
564 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
565 /// assert!(iter.next().is_none());
568 /// If the slice is shorter than `size`:
571 /// let slice = ['f', 'o', 'o'];
572 /// let mut iter = slice.windows(4);
573 /// assert!(iter.next().is_none());
575 #[stable(feature = "rust1", since = "1.0.0")]
577 pub fn windows(&self, size
: usize) -> Windows
<T
> {
578 core_slice
::SliceExt
::windows(self, size
)
581 /// Returns an iterator over `size` elements of the slice at a
582 /// time. The chunks are slices and do not overlap. If `size` does
583 /// not divide the length of the slice, then the last chunk will
584 /// not have length `size`.
588 /// Panics if `size` is 0.
593 /// let slice = ['l', 'o', 'r', 'e', 'm'];
594 /// let mut iter = slice.chunks(2);
595 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
596 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
597 /// assert_eq!(iter.next().unwrap(), &['m']);
598 /// assert!(iter.next().is_none());
600 #[stable(feature = "rust1", since = "1.0.0")]
602 pub fn chunks(&self, size
: usize) -> Chunks
<T
> {
603 core_slice
::SliceExt
::chunks(self, size
)
606 /// Returns an iterator over `chunk_size` elements of the slice at a time.
607 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
608 /// not divide the length of the slice, then the last chunk will not
609 /// have length `chunk_size`.
613 /// Panics if `chunk_size` is 0.
618 /// let v = &mut [0, 0, 0, 0, 0];
619 /// let mut count = 1;
621 /// for chunk in v.chunks_mut(2) {
622 /// for elem in chunk.iter_mut() {
627 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
629 #[stable(feature = "rust1", since = "1.0.0")]
631 pub fn chunks_mut(&mut self, chunk_size
: usize) -> ChunksMut
<T
> {
632 core_slice
::SliceExt
::chunks_mut(self, chunk_size
)
635 /// Divides one slice into two at an index.
637 /// The first will contain all indices from `[0, mid)` (excluding
638 /// the index `mid` itself) and the second will contain all
639 /// indices from `[mid, len)` (excluding the index `len` itself).
643 /// Panics if `mid > len`.
648 /// let v = [10, 40, 30, 20, 50];
649 /// let (v1, v2) = v.split_at(2);
650 /// assert_eq!([10, 40], v1);
651 /// assert_eq!([30, 20, 50], v2);
653 #[stable(feature = "rust1", since = "1.0.0")]
655 pub fn split_at(&self, mid
: usize) -> (&[T
], &[T
]) {
656 core_slice
::SliceExt
::split_at(self, mid
)
659 /// Divides one `&mut` into two at an index.
661 /// The first will contain all indices from `[0, mid)` (excluding
662 /// the index `mid` itself) and the second will contain all
663 /// indices from `[mid, len)` (excluding the index `len` itself).
667 /// Panics if `mid > len`.
672 /// let mut v = [1, 2, 3, 4, 5, 6];
674 /// // scoped to restrict the lifetime of the borrows
676 /// let (left, right) = v.split_at_mut(0);
677 /// assert!(left == []);
678 /// assert!(right == [1, 2, 3, 4, 5, 6]);
682 /// let (left, right) = v.split_at_mut(2);
683 /// assert!(left == [1, 2]);
684 /// assert!(right == [3, 4, 5, 6]);
688 /// let (left, right) = v.split_at_mut(6);
689 /// assert!(left == [1, 2, 3, 4, 5, 6]);
690 /// assert!(right == []);
693 #[stable(feature = "rust1", since = "1.0.0")]
695 pub fn split_at_mut(&mut self, mid
: usize) -> (&mut [T
], &mut [T
]) {
696 core_slice
::SliceExt
::split_at_mut(self, mid
)
699 /// Returns an iterator over subslices separated by elements that match
700 /// `pred`. The matched element is not contained in the subslices.
705 /// let slice = [10, 40, 33, 20];
706 /// let mut iter = slice.split(|num| num % 3 == 0);
708 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
709 /// assert_eq!(iter.next().unwrap(), &[20]);
710 /// assert!(iter.next().is_none());
713 /// If the first element is matched, an empty slice will be the first item
714 /// returned by the iterator. Similarly, if the last element in the slice
715 /// is matched, an empty slice will be the last item returned by the
719 /// let slice = [10, 40, 33];
720 /// let mut iter = slice.split(|num| num % 3 == 0);
722 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
723 /// assert_eq!(iter.next().unwrap(), &[]);
724 /// assert!(iter.next().is_none());
727 /// If two matched elements are directly adjacent, an empty slice will be
728 /// present between them:
731 /// let slice = [10, 6, 33, 20];
732 /// let mut iter = slice.split(|num| num % 3 == 0);
734 /// assert_eq!(iter.next().unwrap(), &[10]);
735 /// assert_eq!(iter.next().unwrap(), &[]);
736 /// assert_eq!(iter.next().unwrap(), &[20]);
737 /// assert!(iter.next().is_none());
739 #[stable(feature = "rust1", since = "1.0.0")]
741 pub fn split
<F
>(&self, pred
: F
) -> Split
<T
, F
>
742 where F
: FnMut(&T
) -> bool
744 core_slice
::SliceExt
::split(self, pred
)
747 /// Returns an iterator over mutable subslices separated by elements that
748 /// match `pred`. The matched element is not contained in the subslices.
753 /// let mut v = [10, 40, 30, 20, 60, 50];
755 /// for group in v.split_mut(|num| *num % 3 == 0) {
758 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
760 #[stable(feature = "rust1", since = "1.0.0")]
762 pub fn split_mut
<F
>(&mut self, pred
: F
) -> SplitMut
<T
, F
>
763 where F
: FnMut(&T
) -> bool
765 core_slice
::SliceExt
::split_mut(self, pred
)
768 /// Returns an iterator over subslices separated by elements that match
769 /// `pred`, limited to returning at most `n` items. The matched element is
770 /// not contained in the subslices.
772 /// The last element returned, if any, will contain the remainder of the
777 /// Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`,
781 /// let v = [10, 40, 30, 20, 60, 50];
783 /// for group in v.splitn(2, |num| *num % 3 == 0) {
784 /// println!("{:?}", group);
787 #[stable(feature = "rust1", since = "1.0.0")]
789 pub fn splitn
<F
>(&self, n
: usize, pred
: F
) -> SplitN
<T
, F
>
790 where F
: FnMut(&T
) -> bool
792 core_slice
::SliceExt
::splitn(self, n
, pred
)
795 /// Returns an iterator over subslices separated by elements that match
796 /// `pred`, limited to returning at most `n` items. The matched element is
797 /// not contained in the subslices.
799 /// The last element returned, if any, will contain the remainder of the
805 /// let mut v = [10, 40, 30, 20, 60, 50];
807 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
810 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
812 #[stable(feature = "rust1", since = "1.0.0")]
814 pub fn splitn_mut
<F
>(&mut self, n
: usize, pred
: F
) -> SplitNMut
<T
, F
>
815 where F
: FnMut(&T
) -> bool
817 core_slice
::SliceExt
::splitn_mut(self, n
, pred
)
820 /// Returns an iterator over subslices separated by elements that match
821 /// `pred` limited to returning at most `n` items. This starts at the end of
822 /// the slice and works backwards. The matched element is not contained in
825 /// The last element returned, if any, will contain the remainder of the
830 /// Print the slice split once, starting from the end, by numbers divisible
831 /// by 3 (i.e. `[50]`, `[10, 40, 30, 20]`):
834 /// let v = [10, 40, 30, 20, 60, 50];
836 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
837 /// println!("{:?}", group);
840 #[stable(feature = "rust1", since = "1.0.0")]
842 pub fn rsplitn
<F
>(&self, n
: usize, pred
: F
) -> RSplitN
<T
, F
>
843 where F
: FnMut(&T
) -> bool
845 core_slice
::SliceExt
::rsplitn(self, n
, pred
)
848 /// Returns an iterator over subslices separated by elements that match
849 /// `pred` limited to returning at most `n` items. This starts at the end of
850 /// the slice and works backwards. The matched element is not contained in
853 /// The last element returned, if any, will contain the remainder of the
859 /// let mut s = [10, 40, 30, 20, 60, 50];
861 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
864 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
866 #[stable(feature = "rust1", since = "1.0.0")]
868 pub fn rsplitn_mut
<F
>(&mut self, n
: usize, pred
: F
) -> RSplitNMut
<T
, F
>
869 where F
: FnMut(&T
) -> bool
871 core_slice
::SliceExt
::rsplitn_mut(self, n
, pred
)
874 /// Returns true if the slice contains an element with the given value.
879 /// let v = [10, 40, 30];
880 /// assert!(v.contains(&30));
881 /// assert!(!v.contains(&50));
883 #[stable(feature = "rust1", since = "1.0.0")]
884 pub fn contains(&self, x
: &T
) -> bool
887 core_slice
::SliceExt
::contains(self, x
)
890 /// Returns true if `needle` is a prefix of the slice.
895 /// let v = [10, 40, 30];
896 /// assert!(v.starts_with(&[10]));
897 /// assert!(v.starts_with(&[10, 40]));
898 /// assert!(!v.starts_with(&[50]));
899 /// assert!(!v.starts_with(&[10, 50]));
901 #[stable(feature = "rust1", since = "1.0.0")]
902 pub fn starts_with(&self, needle
: &[T
]) -> bool
905 core_slice
::SliceExt
::starts_with(self, needle
)
908 /// Returns true if `needle` is a suffix of the slice.
913 /// let v = [10, 40, 30];
914 /// assert!(v.ends_with(&[30]));
915 /// assert!(v.ends_with(&[40, 30]));
916 /// assert!(!v.ends_with(&[50]));
917 /// assert!(!v.ends_with(&[50, 30]));
919 #[stable(feature = "rust1", since = "1.0.0")]
920 pub fn ends_with(&self, needle
: &[T
]) -> bool
923 core_slice
::SliceExt
::ends_with(self, needle
)
926 /// Binary search a sorted slice for a given element.
928 /// If the value is found then `Ok` is returned, containing the
929 /// index of the matching element; if the value is not found then
930 /// `Err` is returned, containing the index where a matching
931 /// element could be inserted while maintaining sorted order.
935 /// Looks up a series of four elements. The first is found, with a
936 /// uniquely determined position; the second and third are not
937 /// found; the fourth could match any position in `[1, 4]`.
940 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
942 /// assert_eq!(s.binary_search(&13), Ok(9));
943 /// assert_eq!(s.binary_search(&4), Err(7));
944 /// assert_eq!(s.binary_search(&100), Err(13));
945 /// let r = s.binary_search(&1);
946 /// assert!(match r { Ok(1...4) => true, _ => false, });
948 #[stable(feature = "rust1", since = "1.0.0")]
949 pub fn binary_search(&self, x
: &T
) -> Result
<usize, usize>
952 core_slice
::SliceExt
::binary_search(self, x
)
955 /// Binary search a sorted slice with a comparator function.
957 /// The comparator function should implement an order consistent
958 /// with the sort order of the underlying slice, returning an
959 /// order code that indicates whether its argument is `Less`,
960 /// `Equal` or `Greater` the desired target.
962 /// If a matching value is found then returns `Ok`, containing
963 /// the index for the matched element; if no match is found then
964 /// `Err` is returned, containing the index where a matching
965 /// element could be inserted while maintaining sorted order.
969 /// Looks up a series of four elements. The first is found, with a
970 /// uniquely determined position; the second and third are not
971 /// found; the fourth could match any position in `[1, 4]`.
974 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
977 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
979 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
981 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
983 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
984 /// assert!(match r { Ok(1...4) => true, _ => false, });
986 #[stable(feature = "rust1", since = "1.0.0")]
988 pub fn binary_search_by
<'a
, F
>(&'a
self, f
: F
) -> Result
<usize, usize>
989 where F
: FnMut(&'a T
) -> Ordering
991 core_slice
::SliceExt
::binary_search_by(self, f
)
994 /// Binary search a sorted slice with a key extraction function.
996 /// Assumes that the slice is sorted by the key, for instance with
997 /// [`sort_by_key`] using the same key extraction function.
999 /// If a matching value is found then returns `Ok`, containing the
1000 /// index for the matched element; if no match is found then `Err`
1001 /// is returned, containing the index where a matching element could
1002 /// be inserted while maintaining sorted order.
1004 /// [`sort_by_key`]: #method.sort_by_key
1008 /// Looks up a series of four elements in a slice of pairs sorted by
1009 /// their second elements. The first is found, with a uniquely
1010 /// determined position; the second and third are not found; the
1011 /// fourth could match any position in `[1, 4]`.
1014 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
1015 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
1016 /// (1, 21), (2, 34), (4, 55)];
1018 /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9));
1019 /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7));
1020 /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
1021 /// let r = s.binary_search_by_key(&1, |&(a,b)| b);
1022 /// assert!(match r { Ok(1...4) => true, _ => false, });
1024 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
1026 pub fn binary_search_by_key
<'a
, B
, F
>(&'a
self, b
: &B
, f
: F
) -> Result
<usize, usize>
1027 where F
: FnMut(&'a T
) -> B
,
1030 core_slice
::SliceExt
::binary_search_by_key(self, b
, f
)
1033 /// This is equivalent to `self.sort_by(|a, b| a.cmp(b))`.
1035 /// This sort is stable and `O(n log n)` worst-case but allocates
1036 /// approximately `2 * n` where `n` is the length of `self`.
1041 /// let mut v = [-5, 4, 1, -3, 2];
1044 /// assert!(v == [-5, -3, 1, 2, 4]);
1046 #[stable(feature = "rust1", since = "1.0.0")]
1048 pub fn sort(&mut self)
1051 self.sort_by(|a
, b
| a
.cmp(b
))
1054 /// Sorts the slice, in place, using `f` to extract a key by which to
1055 /// order the sort by.
1057 /// This sort is stable and `O(n log n)` worst-case but allocates
1058 /// approximately `2 * n`, where `n` is the length of `self`.
1063 /// let mut v = [-5i32, 4, 1, -3, 2];
1065 /// v.sort_by_key(|k| k.abs());
1066 /// assert!(v == [1, 2, -3, 4, -5]);
1068 #[stable(feature = "slice_sort_by_key", since = "1.7.0")]
1070 pub fn sort_by_key
<B
, F
>(&mut self, mut f
: F
)
1071 where F
: FnMut(&T
) -> B
, B
: Ord
1073 self.sort_by(|a
, b
| f(a
).cmp(&f(b
)))
1076 /// Sorts the slice, in place, using `compare` to compare
1079 /// This sort is stable and `O(n log n)` worst-case but allocates
1080 /// approximately `2 * n`, where `n` is the length of `self`.
1085 /// let mut v = [5, 4, 1, 3, 2];
1086 /// v.sort_by(|a, b| a.cmp(b));
1087 /// assert!(v == [1, 2, 3, 4, 5]);
1089 /// // reverse sorting
1090 /// v.sort_by(|a, b| b.cmp(a));
1091 /// assert!(v == [5, 4, 3, 2, 1]);
1093 #[stable(feature = "rust1", since = "1.0.0")]
1095 pub fn sort_by
<F
>(&mut self, compare
: F
)
1096 where F
: FnMut(&T
, &T
) -> Ordering
1098 merge_sort(self, compare
)
1101 /// Copies the elements from `src` into `self`.
1103 /// The length of `src` must be the same as `self`.
1107 /// This function will panic if the two slices have different lengths.
1112 /// let mut dst = [0, 0, 0];
1113 /// let src = [1, 2, 3];
1115 /// dst.clone_from_slice(&src);
1116 /// assert!(dst == [1, 2, 3]);
1118 #[stable(feature = "clone_from_slice", since = "1.7.0")]
1119 pub fn clone_from_slice(&mut self, src
: &[T
]) where T
: Clone
{
1120 core_slice
::SliceExt
::clone_from_slice(self, src
)
1123 /// Copies all elements from `src` into `self`, using a memcpy.
1125 /// The length of `src` must be the same as `self`.
1129 /// This function will panic if the two slices have different lengths.
1134 /// let mut dst = [0, 0, 0];
1135 /// let src = [1, 2, 3];
1137 /// dst.copy_from_slice(&src);
1138 /// assert_eq!(src, dst);
1140 #[stable(feature = "copy_from_slice", since = "1.9.0")]
1141 pub fn copy_from_slice(&mut self, src
: &[T
]) where T
: Copy
{
1142 core_slice
::SliceExt
::copy_from_slice(self, src
)
1146 /// Copies `self` into a new `Vec`.
1151 /// let s = [10, 40, 30];
1152 /// let x = s.to_vec();
1153 /// // Here, `s` and `x` can be modified independently.
1155 #[stable(feature = "rust1", since = "1.0.0")]
1157 pub fn to_vec(&self) -> Vec
<T
>
1160 // NB see hack module in this file
1164 /// Converts `self` into a vector without clones or allocation.
1169 /// let s: Box<[i32]> = Box::new([10, 40, 30]);
1170 /// let x = s.into_vec();
1171 /// // `s` cannot be used anymore because it has been converted into `x`.
1173 /// assert_eq!(x, vec![10, 40, 30]);
1175 #[stable(feature = "rust1", since = "1.0.0")]
1177 pub fn into_vec(self: Box
<Self>) -> Vec
<T
> {
1178 // NB see hack module in this file
1179 hack
::into_vec(self)
1183 ////////////////////////////////////////////////////////////////////////////////
1184 // Extension traits for slices over specific kinds of data
1185 ////////////////////////////////////////////////////////////////////////////////
1186 #[unstable(feature = "slice_concat_ext",
1187 reason
= "trait should not have to exist",
1189 /// An extension trait for concatenating slices
1190 pub trait SliceConcatExt
<T
: ?Sized
> {
1191 #[unstable(feature = "slice_concat_ext",
1192 reason
= "trait should not have to exist",
1194 /// The resulting type after concatenation
1197 /// Flattens a slice of `T` into a single value `Self::Output`.
1202 /// assert_eq!(["hello", "world"].concat(), "helloworld");
1204 #[stable(feature = "rust1", since = "1.0.0")]
1205 fn concat(&self) -> Self::Output
;
1207 /// Flattens a slice of `T` into a single value `Self::Output`, placing a
1208 /// given separator between each.
1213 /// assert_eq!(["hello", "world"].join(" "), "hello world");
1215 #[stable(feature = "rename_connect_to_join", since = "1.3.0")]
1216 fn join(&self, sep
: &T
) -> Self::Output
;
1218 #[stable(feature = "rust1", since = "1.0.0")]
1219 #[rustc_deprecated(since = "1.3.0", reason = "renamed to join")]
1220 fn connect(&self, sep
: &T
) -> Self::Output
;
1223 #[unstable(feature = "slice_concat_ext",
1224 reason
= "trait should not have to exist",
1226 impl<T
: Clone
, V
: Borrow
<[T
]>> SliceConcatExt
<T
> for [V
] {
1227 type Output
= Vec
<T
>;
1229 fn concat(&self) -> Vec
<T
> {
1230 let size
= self.iter().fold(0, |acc
, v
| acc
+ v
.borrow().len());
1231 let mut result
= Vec
::with_capacity(size
);
1233 result
.extend_from_slice(v
.borrow())
1238 fn join(&self, sep
: &T
) -> Vec
<T
> {
1239 let size
= self.iter().fold(0, |acc
, v
| acc
+ v
.borrow().len());
1240 let mut result
= Vec
::with_capacity(size
+ self.len());
1241 let mut first
= true;
1246 result
.push(sep
.clone())
1248 result
.extend_from_slice(v
.borrow())
1253 fn connect(&self, sep
: &T
) -> Vec
<T
> {
1258 ////////////////////////////////////////////////////////////////////////////////
1259 // Standard trait implementations for slices
1260 ////////////////////////////////////////////////////////////////////////////////
1262 #[stable(feature = "rust1", since = "1.0.0")]
1263 impl<T
> Borrow
<[T
]> for Vec
<T
> {
1264 fn borrow(&self) -> &[T
] {
1269 #[stable(feature = "rust1", since = "1.0.0")]
1270 impl<T
> BorrowMut
<[T
]> for Vec
<T
> {
1271 fn borrow_mut(&mut self) -> &mut [T
] {
1276 #[stable(feature = "rust1", since = "1.0.0")]
1277 impl<T
: Clone
> ToOwned
for [T
] {
1278 type Owned
= Vec
<T
>;
1280 fn to_owned(&self) -> Vec
<T
> {
1284 // HACK(japaric): with cfg(test) the inherent `[T]::to_vec`, which is required for this method
1285 // definition, is not available. Since we don't require this method for testing purposes, I'll
1287 // NB see the slice::hack module in slice.rs for more information
1289 fn to_owned(&self) -> Vec
<T
> {
1290 panic
!("not available with cfg(test)")
1294 ////////////////////////////////////////////////////////////////////////////////
1296 ////////////////////////////////////////////////////////////////////////////////
1298 fn insertion_sort
<T
, F
>(v
: &mut [T
], mut compare
: F
)
1299 where F
: FnMut(&T
, &T
) -> Ordering
1301 let len
= v
.len() as isize;
1302 let buf_v
= v
.as_mut_ptr();
1306 // j satisfies: 0 <= j <= i;
1309 // `i` is in bounds.
1310 let read_ptr
= buf_v
.offset(i
) as *const T
;
1312 // find where to insert, we need to do strict <,
1313 // rather than <=, to maintain stability.
1315 // 0 <= j - 1 < len, so .offset(j - 1) is in bounds.
1316 while j
> 0 && compare(&*read_ptr
, &*buf_v
.offset(j
- 1)) == Less
{
1320 // shift everything to the right, to make space to
1321 // insert this value.
1323 // j + 1 could be `len` (for the last `i`), but in
1324 // that case, `i == j` so we don't copy. The
1325 // `.offset(j)` is always in bounds.
1328 let tmp
= ptr
::read(read_ptr
);
1329 ptr
::copy(&*buf_v
.offset(j
), buf_v
.offset(j
+ 1), (i
- j
) as usize);
1330 ptr
::copy_nonoverlapping(&tmp
, buf_v
.offset(j
), 1);
1337 fn merge_sort
<T
, F
>(v
: &mut [T
], mut compare
: F
)
1338 where F
: FnMut(&T
, &T
) -> Ordering
1340 // warning: this wildly uses unsafe.
1341 const BASE_INSERTION
: usize = 32;
1342 const LARGE_INSERTION
: usize = 16;
1344 // FIXME #12092: smaller insertion runs seems to make sorting
1345 // vectors of large elements a little faster on some platforms,
1346 // but hasn't been tested/tuned extensively
1347 let insertion
= if size_of
::<T
>() <= 16 {
1355 // short vectors get sorted in-place via insertion sort to avoid allocations
1356 if len
<= insertion
{
1357 insertion_sort(v
, compare
);
1361 // allocate some memory to use as scratch memory, we keep the
1362 // length 0 so we can keep shallow copies of the contents of `v`
1363 // without risking the dtors running on an object twice if
1364 // `compare` panics.
1365 let mut working_space
= Vec
::with_capacity(2 * len
);
1366 // these both are buffers of length `len`.
1367 let mut buf_dat
= working_space
.as_mut_ptr();
1368 let mut buf_tmp
= unsafe { buf_dat.offset(len as isize) }
;
1371 let buf_v
= v
.as_ptr();
1373 // step 1. sort short runs with insertion sort. This takes the
1374 // values from `v` and sorts them into `buf_dat`, leaving that
1375 // with sorted runs of length INSERTION.
1377 // We could hardcode the sorting comparisons here, and we could
1378 // manipulate/step the pointers themselves, rather than repeatedly
1380 for start
in (0..len
).step_by(insertion
) {
1381 // start <= i < len;
1382 for i
in start
..cmp
::min(start
+ insertion
, len
) {
1383 // j satisfies: start <= j <= i;
1384 let mut j
= i
as isize;
1386 // `i` is in bounds.
1387 let read_ptr
= buf_v
.offset(i
as isize);
1389 // find where to insert, we need to do strict <,
1390 // rather than <=, to maintain stability.
1392 // start <= j - 1 < len, so .offset(j - 1) is in
1394 while j
> start
as isize && compare(&*read_ptr
, &*buf_dat
.offset(j
- 1)) == Less
{
1398 // shift everything to the right, to make space to
1399 // insert this value.
1401 // j + 1 could be `len` (for the last `i`), but in
1402 // that case, `i == j` so we don't copy. The
1403 // `.offset(j)` is always in bounds.
1404 ptr
::copy(&*buf_dat
.offset(j
), buf_dat
.offset(j
+ 1), i
- j
as usize);
1405 ptr
::copy_nonoverlapping(read_ptr
, buf_dat
.offset(j
), 1);
1410 // step 2. merge the sorted runs.
1411 let mut width
= insertion
;
1413 // merge the sorted runs of length `width` in `buf_dat` two at
1414 // a time, placing the result in `buf_tmp`.
1416 // 0 <= start <= len.
1417 for start
in (0..len
).step_by(2 * width
) {
1418 // manipulate pointers directly for speed (rather than
1419 // using a `for` loop with `range` and `.offset` inside
1422 // the end of the first run & start of the
1423 // second. Offset of `len` is defined, since this is
1424 // precisely one byte past the end of the object.
1425 let right_start
= buf_dat
.offset(cmp
::min(start
+ width
, len
) as isize);
1426 // end of the second. Similar reasoning to the above re safety.
1427 let right_end_idx
= cmp
::min(start
+ 2 * width
, len
);
1428 let right_end
= buf_dat
.offset(right_end_idx
as isize);
1430 // the pointers to the elements under consideration
1431 // from the two runs.
1433 // both of these are in bounds.
1434 let mut left
= buf_dat
.offset(start
as isize);
1435 let mut right
= right_start
;
1437 // where we're putting the results, it is a run of
1438 // length `2*width`, so we step it once for each step
1439 // of either `left` or `right`. `buf_tmp` has length
1440 // `len`, so these are in bounds.
1441 let mut out
= buf_tmp
.offset(start
as isize);
1442 let out_end
= buf_tmp
.offset(right_end_idx
as isize);
1444 // If left[last] <= right[0], they are already in order:
1445 // fast-forward the left side (the right side is handled
1447 // If `right` is not empty then left is not empty, and
1448 // the offsets are in bounds.
1449 if right
!= right_end
&& compare(&*right
.offset(-1), &*right
) != Greater
{
1450 let elems
= (right_start
as usize - left
as usize) / mem
::size_of
::<T
>();
1451 ptr
::copy_nonoverlapping(&*left
, out
, elems
);
1452 out
= out
.offset(elems
as isize);
1456 while out
< out_end
{
1457 // Either the left or the right run are exhausted,
1458 // so just copy the remainder from the other run
1459 // and move on; this gives a huge speed-up (order
1460 // of 25%) for mostly sorted vectors (the best
1462 if left
== right_start
{
1463 // the number remaining in this run.
1464 let elems
= (right_end
as usize - right
as usize) / mem
::size_of
::<T
>();
1465 ptr
::copy_nonoverlapping(&*right
, out
, elems
);
1467 } else if right
== right_end
{
1468 let elems
= (right_start
as usize - left
as usize) / mem
::size_of
::<T
>();
1469 ptr
::copy_nonoverlapping(&*left
, out
, elems
);
1473 // check which side is smaller, and that's the
1474 // next element for the new run.
1476 // `left < right_start` and `right < right_end`,
1477 // so these are valid.
1478 let to_copy
= if compare(&*left
, &*right
) == Greater
{
1483 ptr
::copy_nonoverlapping(&*to_copy
, out
, 1);
1489 mem
::swap(&mut buf_dat
, &mut buf_tmp
);
1494 // write the result to `v` in one go, so that there are never two copies
1495 // of the same object in `v`.
1497 ptr
::copy_nonoverlapping(&*buf_dat
, v
.as_mut_ptr(), len
);
1500 // increment the pointer, returning the old pointer.
1502 unsafe fn step
<T
>(ptr
: &mut *mut T
) -> *mut T
{
1504 *ptr
= ptr
.offset(1);