1 // Copyright 2012-2017 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 //! Slice management and manipulation
13 //! For more details see [`std::slice`].
15 //! [`std::slice`]: ../../std/slice/index.html
17 #![stable(feature = "rust1", since = "1.0.0")]
19 // How this module is organized.
21 // The library infrastructure for slices is fairly messy. There's
22 // a lot of stuff defined here. Let's keep it clean.
24 // The layout of this file is thus:
26 // * Inherent methods. This is where most of the slice API resides.
27 // * Implementations of a few common traits with important slice ops.
28 // * Definitions of a bunch of iterators.
30 // * The `raw` and `bytes` submodules.
31 // * Boilerplate trait implementations.
33 use cmp::Ordering::{self, Less, Equal, Greater};
36 use intrinsics::assume;
38 use ops::{FnMut, Try, self};
40 use option::Option::{None, Some};
42 use result::Result::{Ok, Err};
45 use marker::{Copy, Send, Sync, Sized, self};
46 use iter_private::TrustedRandomAccess;
48 #[unstable(feature = "slice_internals", issue = "0",
49 reason = "exposed from core to be reused in std; use the memchr crate")]
50 /// Pure rust memchr implementation, taken from rust-memchr
57 union Repr<'a, T: 'a> {
59 rust_mut: &'a mut [T],
76 /// Returns the number of elements in the slice.
81 /// let a = [1, 2, 3];
82 /// assert_eq!(a.len(), 3);
84 #[stable(feature = "rust1", since = "1.0.0")]
86 #[rustc_const_unstable(feature = "const_slice_len")]
87 pub const fn len(&self) -> usize {
89 Repr { rust: self }.raw.len
93 /// Returns `true` if the slice has a length of 0.
98 /// let a = [1, 2, 3];
99 /// assert!(!a.is_empty());
101 #[stable(feature = "rust1", since = "1.0.0")]
103 #[rustc_const_unstable(feature = "const_slice_len")]
104 pub const fn is_empty(&self) -> bool {
108 /// Returns the first element of the slice, or `None` if it is empty.
113 /// let v = [10, 40, 30];
114 /// assert_eq!(Some(&10), v.first());
116 /// let w: &[i32] = &[];
117 /// assert_eq!(None, w.first());
119 #[stable(feature = "rust1", since = "1.0.0")]
121 pub fn first(&self) -> Option<&T> {
125 /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
130 /// let x = &mut [0, 1, 2];
132 /// if let Some(first) = x.first_mut() {
135 /// assert_eq!(x, &[5, 1, 2]);
137 #[stable(feature = "rust1", since = "1.0.0")]
139 pub fn first_mut(&mut self) -> Option<&mut T> {
143 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
148 /// let x = &[0, 1, 2];
150 /// if let Some((first, elements)) = x.split_first() {
151 /// assert_eq!(first, &0);
152 /// assert_eq!(elements, &[1, 2]);
155 #[stable(feature = "slice_splits", since = "1.5.0")]
157 pub fn split_first(&self) -> Option<(&T, &[T])> {
158 if self.is_empty() { None } else { Some((&self[0], &self[1..])) }
161 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
166 /// let x = &mut [0, 1, 2];
168 /// if let Some((first, elements)) = x.split_first_mut() {
173 /// assert_eq!(x, &[3, 4, 5]);
175 #[stable(feature = "slice_splits", since = "1.5.0")]
177 pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
178 if self.is_empty() { None } else {
179 let split = self.split_at_mut(1);
180 Some((&mut split.0[0], split.1))
184 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
189 /// let x = &[0, 1, 2];
191 /// if let Some((last, elements)) = x.split_last() {
192 /// assert_eq!(last, &2);
193 /// assert_eq!(elements, &[0, 1]);
196 #[stable(feature = "slice_splits", since = "1.5.0")]
198 pub fn split_last(&self) -> Option<(&T, &[T])> {
199 let len = self.len();
200 if len == 0 { None } else { Some((&self[len - 1], &self[..(len - 1)])) }
203 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
208 /// let x = &mut [0, 1, 2];
210 /// if let Some((last, elements)) = x.split_last_mut() {
215 /// assert_eq!(x, &[4, 5, 3]);
217 #[stable(feature = "slice_splits", since = "1.5.0")]
219 pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
220 let len = self.len();
221 if len == 0 { None } else {
222 let split = self.split_at_mut(len - 1);
223 Some((&mut split.1[0], split.0))
228 /// Returns the last element of the slice, or `None` if it is empty.
233 /// let v = [10, 40, 30];
234 /// assert_eq!(Some(&30), v.last());
236 /// let w: &[i32] = &[];
237 /// assert_eq!(None, w.last());
239 #[stable(feature = "rust1", since = "1.0.0")]
241 pub fn last(&self) -> Option<&T> {
242 let last_idx = self.len().checked_sub(1)?;
246 /// Returns a mutable pointer to the last item in the slice.
251 /// let x = &mut [0, 1, 2];
253 /// if let Some(last) = x.last_mut() {
256 /// assert_eq!(x, &[0, 1, 10]);
258 #[stable(feature = "rust1", since = "1.0.0")]
260 pub fn last_mut(&mut self) -> Option<&mut T> {
261 let last_idx = self.len().checked_sub(1)?;
262 self.get_mut(last_idx)
265 /// Returns a reference to an element or subslice depending on the type of
268 /// - If given a position, returns a reference to the element at that
269 /// position or `None` if out of bounds.
270 /// - If given a range, returns the subslice corresponding to that range,
271 /// or `None` if out of bounds.
276 /// let v = [10, 40, 30];
277 /// assert_eq!(Some(&40), v.get(1));
278 /// assert_eq!(Some(&[10, 40][..]), v.get(0..2));
279 /// assert_eq!(None, v.get(3));
280 /// assert_eq!(None, v.get(0..4));
282 #[stable(feature = "rust1", since = "1.0.0")]
284 pub fn get<I>(&self, index: I) -> Option<&I::Output>
285 where I: SliceIndex<Self>
290 /// Returns a mutable reference to an element or subslice depending on the
291 /// type of index (see [`get`]) or `None` if the index is out of bounds.
293 /// [`get`]: #method.get
298 /// let x = &mut [0, 1, 2];
300 /// if let Some(elem) = x.get_mut(1) {
303 /// assert_eq!(x, &[0, 42, 2]);
305 #[stable(feature = "rust1", since = "1.0.0")]
307 pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output>
308 where I: SliceIndex<Self>
313 /// Returns a reference to an element or subslice, without doing bounds
316 /// This is generally not recommended, use with caution! For a safe
317 /// alternative see [`get`].
319 /// [`get`]: #method.get
324 /// let x = &[1, 2, 4];
327 /// assert_eq!(x.get_unchecked(1), &2);
330 #[stable(feature = "rust1", since = "1.0.0")]
332 pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output
333 where I: SliceIndex<Self>
335 index.get_unchecked(self)
338 /// Returns a mutable reference to an element or subslice, without doing
341 /// This is generally not recommended, use with caution! For a safe
342 /// alternative see [`get_mut`].
344 /// [`get_mut`]: #method.get_mut
349 /// let x = &mut [1, 2, 4];
352 /// let elem = x.get_unchecked_mut(1);
355 /// assert_eq!(x, &[1, 13, 4]);
357 #[stable(feature = "rust1", since = "1.0.0")]
359 pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
360 where I: SliceIndex<Self>
362 index.get_unchecked_mut(self)
365 /// Returns a raw pointer to the slice's buffer.
367 /// The caller must ensure that the slice outlives the pointer this
368 /// function returns, or else it will end up pointing to garbage.
370 /// Modifying the container referenced by this slice may cause its buffer
371 /// to be reallocated, which would also make any pointers to it invalid.
376 /// let x = &[1, 2, 4];
377 /// let x_ptr = x.as_ptr();
380 /// for i in 0..x.len() {
381 /// assert_eq!(x.get_unchecked(i), &*x_ptr.add(i));
385 #[stable(feature = "rust1", since = "1.0.0")]
387 #[rustc_const_unstable(feature = "const_slice_as_ptr")]
388 pub const fn as_ptr(&self) -> *const T {
389 self as *const [T] as *const T
392 /// Returns an unsafe mutable pointer to the slice's buffer.
394 /// The caller must ensure that the slice outlives the pointer this
395 /// function returns, or else it will end up pointing to garbage.
397 /// Modifying the container referenced by this slice may cause its buffer
398 /// to be reallocated, which would also make any pointers to it invalid.
403 /// let x = &mut [1, 2, 4];
404 /// let x_ptr = x.as_mut_ptr();
407 /// for i in 0..x.len() {
408 /// *x_ptr.add(i) += 2;
411 /// assert_eq!(x, &[3, 4, 6]);
413 #[stable(feature = "rust1", since = "1.0.0")]
415 pub fn as_mut_ptr(&mut self) -> *mut T {
416 self as *mut [T] as *mut T
419 /// Swaps two elements in the slice.
423 /// * a - The index of the first element
424 /// * b - The index of the second element
428 /// Panics if `a` or `b` are out of bounds.
433 /// let mut v = ["a", "b", "c", "d"];
435 /// assert!(v == ["a", "d", "c", "b"]);
437 #[stable(feature = "rust1", since = "1.0.0")]
439 pub fn swap(&mut self, a: usize, b: usize) {
441 // Can't take two mutable loans from one vector, so instead just cast
442 // them to their raw pointers to do the swap
443 let pa: *mut T = &mut self[a];
444 let pb: *mut T = &mut self[b];
449 /// Reverses the order of elements in the slice, in place.
454 /// let mut v = [1, 2, 3];
456 /// assert!(v == [3, 2, 1]);
458 #[stable(feature = "rust1", since = "1.0.0")]
460 pub fn reverse(&mut self) {
461 let mut i: usize = 0;
464 // For very small types, all the individual reads in the normal
465 // path perform poorly. We can do better, given efficient unaligned
466 // load/store, by loading a larger chunk and reversing a register.
468 // Ideally LLVM would do this for us, as it knows better than we do
469 // whether unaligned reads are efficient (since that changes between
470 // different ARM versions, for example) and what the best chunk size
471 // would be. Unfortunately, as of LLVM 4.0 (2017-05) it only unrolls
472 // the loop, so we need to do this ourselves. (Hypothesis: reverse
473 // is troublesome because the sides can be aligned differently --
474 // will be, when the length is odd -- so there's no way of emitting
475 // pre- and postludes to use fully-aligned SIMD in the middle.)
478 cfg!(any(target_arch = "x86", target_arch = "x86_64"));
480 if fast_unaligned && mem::size_of::<T>() == 1 {
481 // Use the llvm.bswap intrinsic to reverse u8s in a usize
482 let chunk = mem::size_of::<usize>();
483 while i + chunk - 1 < ln / 2 {
485 let pa: *mut T = self.get_unchecked_mut(i);
486 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
487 let va = ptr::read_unaligned(pa as *mut usize);
488 let vb = ptr::read_unaligned(pb as *mut usize);
489 ptr::write_unaligned(pa as *mut usize, vb.swap_bytes());
490 ptr::write_unaligned(pb as *mut usize, va.swap_bytes());
496 if fast_unaligned && mem::size_of::<T>() == 2 {
497 // Use rotate-by-16 to reverse u16s in a u32
498 let chunk = mem::size_of::<u32>() / 2;
499 while i + chunk - 1 < ln / 2 {
501 let pa: *mut T = self.get_unchecked_mut(i);
502 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
503 let va = ptr::read_unaligned(pa as *mut u32);
504 let vb = ptr::read_unaligned(pb as *mut u32);
505 ptr::write_unaligned(pa as *mut u32, vb.rotate_left(16));
506 ptr::write_unaligned(pb as *mut u32, va.rotate_left(16));
513 // Unsafe swap to avoid the bounds check in safe swap.
515 let pa: *mut T = self.get_unchecked_mut(i);
516 let pb: *mut T = self.get_unchecked_mut(ln - i - 1);
523 /// Returns an iterator over the slice.
528 /// let x = &[1, 2, 4];
529 /// let mut iterator = x.iter();
531 /// assert_eq!(iterator.next(), Some(&1));
532 /// assert_eq!(iterator.next(), Some(&2));
533 /// assert_eq!(iterator.next(), Some(&4));
534 /// assert_eq!(iterator.next(), None);
536 #[stable(feature = "rust1", since = "1.0.0")]
538 pub fn iter(&self) -> Iter<T> {
540 let ptr = self.as_ptr();
541 assume(!ptr.is_null());
543 let end = if mem::size_of::<T>() == 0 {
544 (ptr as *const u8).wrapping_add(self.len()) as *const T
552 _marker: marker::PhantomData
557 /// Returns an iterator that allows modifying each value.
562 /// let x = &mut [1, 2, 4];
563 /// for elem in x.iter_mut() {
566 /// assert_eq!(x, &[3, 4, 6]);
568 #[stable(feature = "rust1", since = "1.0.0")]
570 pub fn iter_mut(&mut self) -> IterMut<T> {
572 let ptr = self.as_mut_ptr();
573 assume(!ptr.is_null());
575 let end = if mem::size_of::<T>() == 0 {
576 (ptr as *mut u8).wrapping_add(self.len()) as *mut T
584 _marker: marker::PhantomData
589 /// Returns an iterator over all contiguous windows of length
590 /// `size`. The windows overlap. If the slice is shorter than
591 /// `size`, the iterator returns no values.
595 /// Panics if `size` is 0.
600 /// let slice = ['r', 'u', 's', 't'];
601 /// let mut iter = slice.windows(2);
602 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
603 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
604 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
605 /// assert!(iter.next().is_none());
608 /// If the slice is shorter than `size`:
611 /// let slice = ['f', 'o', 'o'];
612 /// let mut iter = slice.windows(4);
613 /// assert!(iter.next().is_none());
615 #[stable(feature = "rust1", since = "1.0.0")]
617 pub fn windows(&self, size: usize) -> Windows<T> {
619 Windows { v: self, size }
622 /// Returns an iterator over `chunk_size` elements of the slice at a
623 /// time. The chunks are slices and do not overlap. If `chunk_size` does
624 /// not divide the length of the slice, then the last chunk will
625 /// not have length `chunk_size`.
627 /// See [`chunks_exact`] for a variant of this iterator that returns chunks
628 /// of always exactly `chunk_size` elements.
632 /// Panics if `chunk_size` is 0.
637 /// let slice = ['l', 'o', 'r', 'e', 'm'];
638 /// let mut iter = slice.chunks(2);
639 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
640 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
641 /// assert_eq!(iter.next().unwrap(), &['m']);
642 /// assert!(iter.next().is_none());
645 /// [`chunks_exact`]: #method.chunks_exact
646 #[stable(feature = "rust1", since = "1.0.0")]
648 pub fn chunks(&self, chunk_size: usize) -> Chunks<T> {
649 assert!(chunk_size != 0);
650 Chunks { v: self, chunk_size }
653 /// Returns an iterator over `chunk_size` elements of the slice at a time.
654 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
655 /// not divide the length of the slice, then the last chunk will not
656 /// have length `chunk_size`.
658 /// See [`chunks_exact_mut`] for a variant of this iterator that returns chunks
659 /// of always exactly `chunk_size` elements.
663 /// Panics if `chunk_size` is 0.
668 /// let v = &mut [0, 0, 0, 0, 0];
669 /// let mut count = 1;
671 /// for chunk in v.chunks_mut(2) {
672 /// for elem in chunk.iter_mut() {
677 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
680 /// [`chunks_exact_mut`]: #method.chunks_exact_mut
681 #[stable(feature = "rust1", since = "1.0.0")]
683 pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T> {
684 assert!(chunk_size != 0);
685 ChunksMut { v: self, chunk_size }
688 /// Returns an iterator over `chunk_size` elements of the slice at a
689 /// time. The chunks are slices and do not overlap. If `chunk_size` does
690 /// not divide the length of the slice, then the last up to `chunk_size-1`
691 /// elements will be omitted and can be retrieved from the `remainder`
692 /// function of the iterator.
694 /// Due to each chunk having exactly `chunk_size` elements, the compiler
695 /// can often optimize the resulting code better than in the case of
700 /// Panics if `chunk_size` is 0.
705 /// #![feature(chunks_exact)]
707 /// let slice = ['l', 'o', 'r', 'e', 'm'];
708 /// let mut iter = slice.chunks_exact(2);
709 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
710 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
711 /// assert!(iter.next().is_none());
714 /// [`chunks`]: #method.chunks
715 #[unstable(feature = "chunks_exact", issue = "47115")]
717 pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<T> {
718 assert!(chunk_size != 0);
719 let rem = self.len() % chunk_size;
720 let len = self.len() - rem;
721 let (fst, snd) = self.split_at(len);
722 ChunksExact { v: fst, rem: snd, chunk_size }
725 /// Returns an iterator over `chunk_size` elements of the slice at a time.
726 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
727 /// not divide the length of the slice, then the last up to `chunk_size-1`
728 /// elements will be omitted and can be retrieved from the `into_remainder`
729 /// function of the iterator.
731 /// Due to each chunk having exactly `chunk_size` elements, the compiler
732 /// can often optimize the resulting code better than in the case of
737 /// Panics if `chunk_size` is 0.
742 /// #![feature(chunks_exact)]
744 /// let v = &mut [0, 0, 0, 0, 0];
745 /// let mut count = 1;
747 /// for chunk in v.chunks_exact_mut(2) {
748 /// for elem in chunk.iter_mut() {
753 /// assert_eq!(v, &[1, 1, 2, 2, 0]);
756 /// [`chunks_mut`]: #method.chunks_mut
757 #[unstable(feature = "chunks_exact", issue = "47115")]
759 pub fn chunks_exact_mut(&mut self, chunk_size: usize) -> ChunksExactMut<T> {
760 assert!(chunk_size != 0);
761 let rem = self.len() % chunk_size;
762 let len = self.len() - rem;
763 let (fst, snd) = self.split_at_mut(len);
764 ChunksExactMut { v: fst, rem: snd, chunk_size }
767 /// Divides one slice into two at an index.
769 /// The first will contain all indices from `[0, mid)` (excluding
770 /// the index `mid` itself) and the second will contain all
771 /// indices from `[mid, len)` (excluding the index `len` itself).
775 /// Panics if `mid > len`.
780 /// let v = [1, 2, 3, 4, 5, 6];
783 /// let (left, right) = v.split_at(0);
784 /// assert!(left == []);
785 /// assert!(right == [1, 2, 3, 4, 5, 6]);
789 /// let (left, right) = v.split_at(2);
790 /// assert!(left == [1, 2]);
791 /// assert!(right == [3, 4, 5, 6]);
795 /// let (left, right) = v.split_at(6);
796 /// assert!(left == [1, 2, 3, 4, 5, 6]);
797 /// assert!(right == []);
800 #[stable(feature = "rust1", since = "1.0.0")]
802 pub fn split_at(&self, mid: usize) -> (&[T], &[T]) {
803 (&self[..mid], &self[mid..])
806 /// Divides one mutable slice into two at an index.
808 /// The first will contain all indices from `[0, mid)` (excluding
809 /// the index `mid` itself) and the second will contain all
810 /// indices from `[mid, len)` (excluding the index `len` itself).
814 /// Panics if `mid > len`.
819 /// let mut v = [1, 0, 3, 0, 5, 6];
820 /// // scoped to restrict the lifetime of the borrows
822 /// let (left, right) = v.split_at_mut(2);
823 /// assert!(left == [1, 0]);
824 /// assert!(right == [3, 0, 5, 6]);
828 /// assert!(v == [1, 2, 3, 4, 5, 6]);
830 #[stable(feature = "rust1", since = "1.0.0")]
832 pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
833 let len = self.len();
834 let ptr = self.as_mut_ptr();
839 (from_raw_parts_mut(ptr, mid),
840 from_raw_parts_mut(ptr.add(mid), len - mid))
844 /// Returns an iterator over subslices separated by elements that match
845 /// `pred`. The matched element is not contained in the subslices.
850 /// let slice = [10, 40, 33, 20];
851 /// let mut iter = slice.split(|num| num % 3 == 0);
853 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
854 /// assert_eq!(iter.next().unwrap(), &[20]);
855 /// assert!(iter.next().is_none());
858 /// If the first element is matched, an empty slice will be the first item
859 /// returned by the iterator. Similarly, if the last element in the slice
860 /// is matched, an empty slice will be the last item returned by the
864 /// let slice = [10, 40, 33];
865 /// let mut iter = slice.split(|num| num % 3 == 0);
867 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
868 /// assert_eq!(iter.next().unwrap(), &[]);
869 /// assert!(iter.next().is_none());
872 /// If two matched elements are directly adjacent, an empty slice will be
873 /// present between them:
876 /// let slice = [10, 6, 33, 20];
877 /// let mut iter = slice.split(|num| num % 3 == 0);
879 /// assert_eq!(iter.next().unwrap(), &[10]);
880 /// assert_eq!(iter.next().unwrap(), &[]);
881 /// assert_eq!(iter.next().unwrap(), &[20]);
882 /// assert!(iter.next().is_none());
884 #[stable(feature = "rust1", since = "1.0.0")]
886 pub fn split<F>(&self, pred: F) -> Split<T, F>
887 where F: FnMut(&T) -> bool
896 /// Returns an iterator over mutable subslices separated by elements that
897 /// match `pred`. The matched element is not contained in the subslices.
902 /// let mut v = [10, 40, 30, 20, 60, 50];
904 /// for group in v.split_mut(|num| *num % 3 == 0) {
907 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
909 #[stable(feature = "rust1", since = "1.0.0")]
911 pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<T, F>
912 where F: FnMut(&T) -> bool
914 SplitMut { v: self, pred, finished: false }
917 /// Returns an iterator over subslices separated by elements that match
918 /// `pred`, starting at the end of the slice and working backwards.
919 /// The matched element is not contained in the subslices.
924 /// let slice = [11, 22, 33, 0, 44, 55];
925 /// let mut iter = slice.rsplit(|num| *num == 0);
927 /// assert_eq!(iter.next().unwrap(), &[44, 55]);
928 /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
929 /// assert_eq!(iter.next(), None);
932 /// As with `split()`, if the first or last element is matched, an empty
933 /// slice will be the first (or last) item returned by the iterator.
936 /// let v = &[0, 1, 1, 2, 3, 5, 8];
937 /// let mut it = v.rsplit(|n| *n % 2 == 0);
938 /// assert_eq!(it.next().unwrap(), &[]);
939 /// assert_eq!(it.next().unwrap(), &[3, 5]);
940 /// assert_eq!(it.next().unwrap(), &[1, 1]);
941 /// assert_eq!(it.next().unwrap(), &[]);
942 /// assert_eq!(it.next(), None);
944 #[stable(feature = "slice_rsplit", since = "1.27.0")]
946 pub fn rsplit<F>(&self, pred: F) -> RSplit<T, F>
947 where F: FnMut(&T) -> bool
949 RSplit { inner: self.split(pred) }
952 /// Returns an iterator over mutable subslices separated by elements that
953 /// match `pred`, starting at the end of the slice and working
954 /// backwards. The matched element is not contained in the subslices.
959 /// let mut v = [100, 400, 300, 200, 600, 500];
961 /// let mut count = 0;
962 /// for group in v.rsplit_mut(|num| *num % 3 == 0) {
964 /// group[0] = count;
966 /// assert_eq!(v, [3, 400, 300, 2, 600, 1]);
969 #[stable(feature = "slice_rsplit", since = "1.27.0")]
971 pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<T, F>
972 where F: FnMut(&T) -> bool
974 RSplitMut { inner: self.split_mut(pred) }
977 /// Returns an iterator over subslices separated by elements that match
978 /// `pred`, limited to returning at most `n` items. The matched element is
979 /// not contained in the subslices.
981 /// The last element returned, if any, will contain the remainder of the
986 /// Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`,
990 /// let v = [10, 40, 30, 20, 60, 50];
992 /// for group in v.splitn(2, |num| *num % 3 == 0) {
993 /// println!("{:?}", group);
996 #[stable(feature = "rust1", since = "1.0.0")]
998 pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F>
999 where F: FnMut(&T) -> bool
1002 inner: GenericSplitN {
1003 iter: self.split(pred),
1009 /// Returns an iterator over subslices separated by elements that match
1010 /// `pred`, limited to returning at most `n` items. The matched element is
1011 /// not contained in the subslices.
1013 /// The last element returned, if any, will contain the remainder of the
1019 /// let mut v = [10, 40, 30, 20, 60, 50];
1021 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
1024 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
1026 #[stable(feature = "rust1", since = "1.0.0")]
1028 pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<T, F>
1029 where F: FnMut(&T) -> bool
1032 inner: GenericSplitN {
1033 iter: self.split_mut(pred),
1039 /// Returns an iterator over subslices separated by elements that match
1040 /// `pred` limited to returning at most `n` items. This starts at the end of
1041 /// the slice and works backwards. The matched element is not contained in
1044 /// The last element returned, if any, will contain the remainder of the
1049 /// Print the slice split once, starting from the end, by numbers divisible
1050 /// by 3 (i.e. `[50]`, `[10, 40, 30, 20]`):
1053 /// let v = [10, 40, 30, 20, 60, 50];
1055 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
1056 /// println!("{:?}", group);
1059 #[stable(feature = "rust1", since = "1.0.0")]
1061 pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F>
1062 where F: FnMut(&T) -> bool
1065 inner: GenericSplitN {
1066 iter: self.rsplit(pred),
1072 /// Returns an iterator over subslices separated by elements that match
1073 /// `pred` limited to returning at most `n` items. This starts at the end of
1074 /// the slice and works backwards. The matched element is not contained in
1077 /// The last element returned, if any, will contain the remainder of the
1083 /// let mut s = [10, 40, 30, 20, 60, 50];
1085 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
1088 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
1090 #[stable(feature = "rust1", since = "1.0.0")]
1092 pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<T, F>
1093 where F: FnMut(&T) -> bool
1096 inner: GenericSplitN {
1097 iter: self.rsplit_mut(pred),
1103 /// Returns `true` if the slice contains an element with the given value.
1108 /// let v = [10, 40, 30];
1109 /// assert!(v.contains(&30));
1110 /// assert!(!v.contains(&50));
1112 #[stable(feature = "rust1", since = "1.0.0")]
1113 pub fn contains(&self, x: &T) -> bool
1116 x.slice_contains(self)
1119 /// Returns `true` if `needle` is a prefix of the slice.
1124 /// let v = [10, 40, 30];
1125 /// assert!(v.starts_with(&[10]));
1126 /// assert!(v.starts_with(&[10, 40]));
1127 /// assert!(!v.starts_with(&[50]));
1128 /// assert!(!v.starts_with(&[10, 50]));
1131 /// Always returns `true` if `needle` is an empty slice:
1134 /// let v = &[10, 40, 30];
1135 /// assert!(v.starts_with(&[]));
1136 /// let v: &[u8] = &[];
1137 /// assert!(v.starts_with(&[]));
1139 #[stable(feature = "rust1", since = "1.0.0")]
1140 pub fn starts_with(&self, needle: &[T]) -> bool
1143 let n = needle.len();
1144 self.len() >= n && needle == &self[..n]
1147 /// Returns `true` if `needle` is a suffix of the slice.
1152 /// let v = [10, 40, 30];
1153 /// assert!(v.ends_with(&[30]));
1154 /// assert!(v.ends_with(&[40, 30]));
1155 /// assert!(!v.ends_with(&[50]));
1156 /// assert!(!v.ends_with(&[50, 30]));
1159 /// Always returns `true` if `needle` is an empty slice:
1162 /// let v = &[10, 40, 30];
1163 /// assert!(v.ends_with(&[]));
1164 /// let v: &[u8] = &[];
1165 /// assert!(v.ends_with(&[]));
1167 #[stable(feature = "rust1", since = "1.0.0")]
1168 pub fn ends_with(&self, needle: &[T]) -> bool
1171 let (m, n) = (self.len(), needle.len());
1172 m >= n && needle == &self[m-n..]
1175 /// Binary searches this sorted slice for a given element.
1177 /// If the value is found then `Ok` is returned, containing the
1178 /// index of the matching element; if the value is not found then
1179 /// `Err` is returned, containing the index where a matching
1180 /// element could be inserted while maintaining sorted order.
1184 /// Looks up a series of four elements. The first is found, with a
1185 /// uniquely determined position; the second and third are not
1186 /// found; the fourth could match any position in `[1, 4]`.
1189 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1191 /// assert_eq!(s.binary_search(&13), Ok(9));
1192 /// assert_eq!(s.binary_search(&4), Err(7));
1193 /// assert_eq!(s.binary_search(&100), Err(13));
1194 /// let r = s.binary_search(&1);
1195 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1197 #[stable(feature = "rust1", since = "1.0.0")]
1198 pub fn binary_search(&self, x: &T) -> Result<usize, usize>
1201 self.binary_search_by(|p| p.cmp(x))
1204 /// Binary searches this sorted slice with a comparator function.
1206 /// The comparator function should implement an order consistent
1207 /// with the sort order of the underlying slice, returning an
1208 /// order code that indicates whether its argument is `Less`,
1209 /// `Equal` or `Greater` the desired target.
1211 /// If a matching value is found then returns `Ok`, containing
1212 /// the index for the matched element; if no match is found then
1213 /// `Err` is returned, containing the index where a matching
1214 /// element could be inserted while maintaining sorted order.
1218 /// Looks up a series of four elements. The first is found, with a
1219 /// uniquely determined position; the second and third are not
1220 /// found; the fourth could match any position in `[1, 4]`.
1223 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1226 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
1228 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
1230 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
1232 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
1233 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1235 #[stable(feature = "rust1", since = "1.0.0")]
1237 pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
1238 where F: FnMut(&'a T) -> Ordering
1241 let mut size = s.len();
1245 let mut base = 0usize;
1247 let half = size / 2;
1248 let mid = base + half;
1249 // mid is always in [0, size), that means mid is >= 0 and < size.
1250 // mid >= 0: by definition
1251 // mid < size: mid = size / 2 + size / 4 + size / 8 ...
1252 let cmp = f(unsafe { s.get_unchecked(mid) });
1253 base = if cmp == Greater { base } else { mid };
1256 // base is always in [0, size) because base <= mid.
1257 let cmp = f(unsafe { s.get_unchecked(base) });
1258 if cmp == Equal { Ok(base) } else { Err(base + (cmp == Less) as usize) }
1262 /// Binary searches this sorted slice with a key extraction function.
1264 /// Assumes that the slice is sorted by the key, for instance with
1265 /// [`sort_by_key`] using the same key extraction function.
1267 /// If a matching value is found then returns `Ok`, containing the
1268 /// index for the matched element; if no match is found then `Err`
1269 /// is returned, containing the index where a matching element could
1270 /// be inserted while maintaining sorted order.
1272 /// [`sort_by_key`]: #method.sort_by_key
1276 /// Looks up a series of four elements in a slice of pairs sorted by
1277 /// their second elements. The first is found, with a uniquely
1278 /// determined position; the second and third are not found; the
1279 /// fourth could match any position in `[1, 4]`.
1282 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
1283 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
1284 /// (1, 21), (2, 34), (4, 55)];
1286 /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9));
1287 /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7));
1288 /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
1289 /// let r = s.binary_search_by_key(&1, |&(a,b)| b);
1290 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1292 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
1294 pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
1295 where F: FnMut(&'a T) -> B,
1298 self.binary_search_by(|k| f(k).cmp(b))
1301 /// Sorts the slice, but may not preserve the order of equal elements.
1303 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1304 /// and `O(n log n)` worst-case.
1306 /// # Current implementation
1308 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1309 /// which combines the fast average case of randomized quicksort with the fast worst case of
1310 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1311 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1312 /// deterministic behavior.
1314 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1315 /// slice consists of several concatenated sorted sequences.
1320 /// let mut v = [-5, 4, 1, -3, 2];
1322 /// v.sort_unstable();
1323 /// assert!(v == [-5, -3, 1, 2, 4]);
1326 /// [pdqsort]: https://github.com/orlp/pdqsort
1327 #[stable(feature = "sort_unstable", since = "1.20.0")]
1329 pub fn sort_unstable(&mut self)
1332 sort::quicksort(self, |a, b| a.lt(b));
1335 /// Sorts the slice with a comparator function, but may not preserve the order of equal
1338 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1339 /// and `O(n log n)` worst-case.
1341 /// # Current implementation
1343 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1344 /// which combines the fast average case of randomized quicksort with the fast worst case of
1345 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1346 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1347 /// deterministic behavior.
1349 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1350 /// slice consists of several concatenated sorted sequences.
1355 /// let mut v = [5, 4, 1, 3, 2];
1356 /// v.sort_unstable_by(|a, b| a.cmp(b));
1357 /// assert!(v == [1, 2, 3, 4, 5]);
1359 /// // reverse sorting
1360 /// v.sort_unstable_by(|a, b| b.cmp(a));
1361 /// assert!(v == [5, 4, 3, 2, 1]);
1364 /// [pdqsort]: https://github.com/orlp/pdqsort
1365 #[stable(feature = "sort_unstable", since = "1.20.0")]
1367 pub fn sort_unstable_by<F>(&mut self, mut compare: F)
1368 where F: FnMut(&T, &T) -> Ordering
1370 sort::quicksort(self, |a, b| compare(a, b) == Ordering::Less);
1373 /// Sorts the slice with a key extraction function, but may not preserve the order of equal
1376 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1377 /// and `O(m n log(m n))` worst-case, where the key function is `O(m)`.
1379 /// # Current implementation
1381 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1382 /// which combines the fast average case of randomized quicksort with the fast worst case of
1383 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1384 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1385 /// deterministic behavior.
1390 /// let mut v = [-5i32, 4, 1, -3, 2];
1392 /// v.sort_unstable_by_key(|k| k.abs());
1393 /// assert!(v == [1, 2, -3, 4, -5]);
1396 /// [pdqsort]: https://github.com/orlp/pdqsort
1397 #[stable(feature = "sort_unstable", since = "1.20.0")]
1399 pub fn sort_unstable_by_key<K, F>(&mut self, mut f: F)
1400 where F: FnMut(&T) -> K, K: Ord
1402 sort::quicksort(self, |a, b| f(a).lt(&f(b)));
1405 /// Moves all consecutive repeated elements to the end of the slice according to the
1406 /// [`PartialEq`] trait implementation.
1408 /// Returns two slices. The first contains no consecutive repeated elements.
1409 /// The second contains all the duplicates in no specified order.
1411 /// If the slice is sorted, the first returned slice contains no duplicates.
1416 /// #![feature(slice_partition_dedup)]
1418 /// let mut slice = [1, 2, 2, 3, 3, 2, 1, 1];
1420 /// let (dedup, duplicates) = slice.partition_dedup();
1422 /// assert_eq!(dedup, [1, 2, 3, 2, 1]);
1423 /// assert_eq!(duplicates, [2, 3, 1]);
1425 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1427 pub fn partition_dedup(&mut self) -> (&mut [T], &mut [T])
1430 self.partition_dedup_by(|a, b| a == b)
1433 /// Moves all but the first of consecutive elements to the end of the slice satisfying
1434 /// a given equality relation.
1436 /// Returns two slices. The first contains no consecutive repeated elements.
1437 /// The second contains all the duplicates in no specified order.
1439 /// The `same_bucket` function is passed references to two elements from the slice and
1440 /// must determine if the elements compare equal. The elements are passed in opposite order
1441 /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is moved
1442 /// at the end of the slice.
1444 /// If the slice is sorted, the first returned slice contains no duplicates.
1449 /// #![feature(slice_partition_dedup)]
1451 /// let mut slice = ["foo", "Foo", "BAZ", "Bar", "bar", "baz", "BAZ"];
1453 /// let (dedup, duplicates) = slice.partition_dedup_by(|a, b| a.eq_ignore_ascii_case(b));
1455 /// assert_eq!(dedup, ["foo", "BAZ", "Bar", "baz"]);
1456 /// assert_eq!(duplicates, ["bar", "Foo", "BAZ"]);
1458 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1460 pub fn partition_dedup_by<F>(&mut self, mut same_bucket: F) -> (&mut [T], &mut [T])
1461 where F: FnMut(&mut T, &mut T) -> bool
1463 // Although we have a mutable reference to `self`, we cannot make
1464 // *arbitrary* changes. The `same_bucket` calls could panic, so we
1465 // must ensure that the slice is in a valid state at all times.
1467 // The way that we handle this is by using swaps; we iterate
1468 // over all the elements, swapping as we go so that at the end
1469 // the elements we wish to keep are in the front, and those we
1470 // wish to reject are at the back. We can then split the slice.
1471 // This operation is still O(n).
1473 // Example: We start in this state, where `r` represents "next
1474 // read" and `w` represents "next_write`.
1477 // +---+---+---+---+---+---+
1478 // | 0 | 1 | 1 | 2 | 3 | 3 |
1479 // +---+---+---+---+---+---+
1482 // Comparing self[r] against self[w-1], this is not a duplicate, so
1483 // we swap self[r] and self[w] (no effect as r==w) and then increment both
1484 // r and w, leaving us with:
1487 // +---+---+---+---+---+---+
1488 // | 0 | 1 | 1 | 2 | 3 | 3 |
1489 // +---+---+---+---+---+---+
1492 // Comparing self[r] against self[w-1], this value is a duplicate,
1493 // so we increment `r` but leave everything else unchanged:
1496 // +---+---+---+---+---+---+
1497 // | 0 | 1 | 1 | 2 | 3 | 3 |
1498 // +---+---+---+---+---+---+
1501 // Comparing self[r] against self[w-1], this is not a duplicate,
1502 // so swap self[r] and self[w] and advance r and w:
1505 // +---+---+---+---+---+---+
1506 // | 0 | 1 | 2 | 1 | 3 | 3 |
1507 // +---+---+---+---+---+---+
1510 // Not a duplicate, repeat:
1513 // +---+---+---+---+---+---+
1514 // | 0 | 1 | 2 | 3 | 1 | 3 |
1515 // +---+---+---+---+---+---+
1518 // Duplicate, advance r. End of slice. Split at w.
1520 let len = self.len();
1522 return (self, &mut [])
1525 let ptr = self.as_mut_ptr();
1526 let mut next_read: usize = 1;
1527 let mut next_write: usize = 1;
1530 // Avoid bounds checks by using raw pointers.
1531 while next_read < len {
1532 let ptr_read = ptr.add(next_read);
1533 let prev_ptr_write = ptr.add(next_write - 1);
1534 if !same_bucket(&mut *ptr_read, &mut *prev_ptr_write) {
1535 if next_read != next_write {
1536 let ptr_write = prev_ptr_write.offset(1);
1537 mem::swap(&mut *ptr_read, &mut *ptr_write);
1545 self.split_at_mut(next_write)
1548 /// Moves all but the first of consecutive elements to the end of the slice that resolve
1549 /// to the same key.
1551 /// Returns two slices. The first contains no consecutive repeated elements.
1552 /// The second contains all the duplicates in no specified order.
1554 /// If the slice is sorted, the first returned slice contains no duplicates.
1559 /// #![feature(slice_partition_dedup)]
1561 /// let mut slice = [10, 20, 21, 30, 30, 20, 11, 13];
1563 /// let (dedup, duplicates) = slice.partition_dedup_by_key(|i| *i / 10);
1565 /// assert_eq!(dedup, [10, 20, 30, 20, 11]);
1566 /// assert_eq!(duplicates, [21, 30, 13]);
1568 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1570 pub fn partition_dedup_by_key<K, F>(&mut self, mut key: F) -> (&mut [T], &mut [T])
1571 where F: FnMut(&mut T) -> K,
1574 self.partition_dedup_by(|a, b| key(a) == key(b))
1577 /// Rotates the slice in-place such that the first `mid` elements of the
1578 /// slice move to the end while the last `self.len() - mid` elements move to
1579 /// the front. After calling `rotate_left`, the element previously at index
1580 /// `mid` will become the first element in the slice.
1584 /// This function will panic if `mid` is greater than the length of the
1585 /// slice. Note that `mid == self.len()` does _not_ panic and is a no-op
1590 /// Takes linear (in `self.len()`) time.
1595 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1596 /// a.rotate_left(2);
1597 /// assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
1600 /// Rotating a subslice:
1603 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1604 /// a[1..5].rotate_left(1);
1605 /// assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']);
1607 #[stable(feature = "slice_rotate", since = "1.26.0")]
1608 pub fn rotate_left(&mut self, mid: usize) {
1609 assert!(mid <= self.len());
1610 let k = self.len() - mid;
1613 let p = self.as_mut_ptr();
1614 rotate::ptr_rotate(mid, p.add(mid), k);
1618 /// Rotates the slice in-place such that the first `self.len() - k`
1619 /// elements of the slice move to the end while the last `k` elements move
1620 /// to the front. After calling `rotate_right`, the element previously at
1621 /// index `self.len() - k` will become the first element in the slice.
1625 /// This function will panic if `k` is greater than the length of the
1626 /// slice. Note that `k == self.len()` does _not_ panic and is a no-op
1631 /// Takes linear (in `self.len()`) time.
1636 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1637 /// a.rotate_right(2);
1638 /// assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);
1641 /// Rotate a subslice:
1644 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1645 /// a[1..5].rotate_right(1);
1646 /// assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']);
1648 #[stable(feature = "slice_rotate", since = "1.26.0")]
1649 pub fn rotate_right(&mut self, k: usize) {
1650 assert!(k <= self.len());
1651 let mid = self.len() - k;
1654 let p = self.as_mut_ptr();
1655 rotate::ptr_rotate(mid, p.add(mid), k);
1659 /// Copies the elements from `src` into `self`.
1661 /// The length of `src` must be the same as `self`.
1663 /// If `src` implements `Copy`, it can be more performant to use
1664 /// [`copy_from_slice`].
1668 /// This function will panic if the two slices have different lengths.
1672 /// Cloning two elements from a slice into another:
1675 /// let src = [1, 2, 3, 4];
1676 /// let mut dst = [0, 0];
1678 /// // Because the slices have to be the same length,
1679 /// // we slice the source slice from four elements
1680 /// // to two. It will panic if we don't do this.
1681 /// dst.clone_from_slice(&src[2..]);
1683 /// assert_eq!(src, [1, 2, 3, 4]);
1684 /// assert_eq!(dst, [3, 4]);
1687 /// Rust enforces that there can only be one mutable reference with no
1688 /// immutable references to a particular piece of data in a particular
1689 /// scope. Because of this, attempting to use `clone_from_slice` on a
1690 /// single slice will result in a compile failure:
1693 /// let mut slice = [1, 2, 3, 4, 5];
1695 /// slice[..2].clone_from_slice(&slice[3..]); // compile fail!
1698 /// To work around this, we can use [`split_at_mut`] to create two distinct
1699 /// sub-slices from a slice:
1702 /// let mut slice = [1, 2, 3, 4, 5];
1705 /// let (left, right) = slice.split_at_mut(2);
1706 /// left.clone_from_slice(&right[1..]);
1709 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
1712 /// [`copy_from_slice`]: #method.copy_from_slice
1713 /// [`split_at_mut`]: #method.split_at_mut
1714 #[stable(feature = "clone_from_slice", since = "1.7.0")]
1715 pub fn clone_from_slice(&mut self, src: &[T]) where T: Clone {
1716 assert!(self.len() == src.len(),
1717 "destination and source slices have different lengths");
1718 // NOTE: We need to explicitly slice them to the same length
1719 // for bounds checking to be elided, and the optimizer will
1720 // generate memcpy for simple cases (for example T = u8).
1721 let len = self.len();
1722 let src = &src[..len];
1724 self[i].clone_from(&src[i]);
1729 /// Copies all elements from `src` into `self`, using a memcpy.
1731 /// The length of `src` must be the same as `self`.
1733 /// If `src` does not implement `Copy`, use [`clone_from_slice`].
1737 /// This function will panic if the two slices have different lengths.
1741 /// Copying two elements from a slice into another:
1744 /// let src = [1, 2, 3, 4];
1745 /// let mut dst = [0, 0];
1747 /// // Because the slices have to be the same length,
1748 /// // we slice the source slice from four elements
1749 /// // to two. It will panic if we don't do this.
1750 /// dst.copy_from_slice(&src[2..]);
1752 /// assert_eq!(src, [1, 2, 3, 4]);
1753 /// assert_eq!(dst, [3, 4]);
1756 /// Rust enforces that there can only be one mutable reference with no
1757 /// immutable references to a particular piece of data in a particular
1758 /// scope. Because of this, attempting to use `copy_from_slice` on a
1759 /// single slice will result in a compile failure:
1762 /// let mut slice = [1, 2, 3, 4, 5];
1764 /// slice[..2].copy_from_slice(&slice[3..]); // compile fail!
1767 /// To work around this, we can use [`split_at_mut`] to create two distinct
1768 /// sub-slices from a slice:
1771 /// let mut slice = [1, 2, 3, 4, 5];
1774 /// let (left, right) = slice.split_at_mut(2);
1775 /// left.copy_from_slice(&right[1..]);
1778 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
1781 /// [`clone_from_slice`]: #method.clone_from_slice
1782 /// [`split_at_mut`]: #method.split_at_mut
1783 #[stable(feature = "copy_from_slice", since = "1.9.0")]
1784 pub fn copy_from_slice(&mut self, src: &[T]) where T: Copy {
1785 assert_eq!(self.len(), src.len(),
1786 "destination and source slices have different lengths");
1788 ptr::copy_nonoverlapping(
1789 src.as_ptr(), self.as_mut_ptr(), self.len());
1793 /// Copies elements from one part of the slice to another part of itself,
1794 /// using a memmove.
1796 /// `src` is the range within `self` to copy from. `dest` is the starting
1797 /// index of the range within `self` to copy to, which will have the same
1798 /// length as `src`. The two ranges may overlap. The ends of the two ranges
1799 /// must be less than or equal to `self.len()`.
1803 /// This function will panic if either range exceeds the end of the slice,
1804 /// or if the end of `src` is before the start.
1808 /// Copying four bytes within a slice:
1811 /// # #![feature(copy_within)]
1812 /// let mut bytes = *b"Hello, World!";
1814 /// bytes.copy_within(1..5, 8);
1816 /// assert_eq!(&bytes, b"Hello, Wello!");
1818 #[unstable(feature = "copy_within", issue = "54236")]
1819 pub fn copy_within<R: ops::RangeBounds<usize>>(&mut self, src: R, dest: usize)
1823 let src_start = match src.start_bound() {
1824 ops::Bound::Included(&n) => n,
1825 ops::Bound::Excluded(&n) => n
1827 .unwrap_or_else(|| slice_index_overflow_fail()),
1828 ops::Bound::Unbounded => 0,
1830 let src_end = match src.end_bound() {
1831 ops::Bound::Included(&n) => n
1833 .unwrap_or_else(|| slice_index_overflow_fail()),
1834 ops::Bound::Excluded(&n) => n,
1835 ops::Bound::Unbounded => self.len(),
1837 assert!(src_start <= src_end, "src end is before src start");
1838 assert!(src_end <= self.len(), "src is out of bounds");
1839 let count = src_end - src_start;
1840 assert!(dest <= self.len() - count, "dest is out of bounds");
1843 self.get_unchecked(src_start),
1844 self.get_unchecked_mut(dest),
1850 /// Swaps all elements in `self` with those in `other`.
1852 /// The length of `other` must be the same as `self`.
1856 /// This function will panic if the two slices have different lengths.
1860 /// Swapping two elements across slices:
1863 /// let mut slice1 = [0, 0];
1864 /// let mut slice2 = [1, 2, 3, 4];
1866 /// slice1.swap_with_slice(&mut slice2[2..]);
1868 /// assert_eq!(slice1, [3, 4]);
1869 /// assert_eq!(slice2, [1, 2, 0, 0]);
1872 /// Rust enforces that there can only be one mutable reference to a
1873 /// particular piece of data in a particular scope. Because of this,
1874 /// attempting to use `swap_with_slice` on a single slice will result in
1875 /// a compile failure:
1878 /// let mut slice = [1, 2, 3, 4, 5];
1879 /// slice[..2].swap_with_slice(&mut slice[3..]); // compile fail!
1882 /// To work around this, we can use [`split_at_mut`] to create two distinct
1883 /// mutable sub-slices from a slice:
1886 /// let mut slice = [1, 2, 3, 4, 5];
1889 /// let (left, right) = slice.split_at_mut(2);
1890 /// left.swap_with_slice(&mut right[1..]);
1893 /// assert_eq!(slice, [4, 5, 3, 1, 2]);
1896 /// [`split_at_mut`]: #method.split_at_mut
1897 #[stable(feature = "swap_with_slice", since = "1.27.0")]
1898 pub fn swap_with_slice(&mut self, other: &mut [T]) {
1899 assert!(self.len() == other.len(),
1900 "destination and source slices have different lengths");
1902 ptr::swap_nonoverlapping(
1903 self.as_mut_ptr(), other.as_mut_ptr(), self.len());
1907 /// Function to calculate lengths of the middle and trailing slice for `align_to{,_mut}`.
1908 fn align_to_offsets<U>(&self) -> (usize, usize) {
1909 // What we gonna do about `rest` is figure out what multiple of `U`s we can put in a
1910 // lowest number of `T`s. And how many `T`s we need for each such "multiple".
1912 // Consider for example T=u8 U=u16. Then we can put 1 U in 2 Ts. Simple. Now, consider
1913 // for example a case where size_of::<T> = 16, size_of::<U> = 24. We can put 2 Us in
1914 // place of every 3 Ts in the `rest` slice. A bit more complicated.
1916 // Formula to calculate this is:
1918 // Us = lcm(size_of::<T>, size_of::<U>) / size_of::<U>
1919 // Ts = lcm(size_of::<T>, size_of::<U>) / size_of::<T>
1921 // Expanded and simplified:
1923 // Us = size_of::<T> / gcd(size_of::<T>, size_of::<U>)
1924 // Ts = size_of::<U> / gcd(size_of::<T>, size_of::<U>)
1926 // Luckily since all this is constant-evaluated... performance here matters not!
1928 fn gcd(a: usize, b: usize) -> usize {
1929 // iterative stein’s algorithm
1930 // We should still make this `const fn` (and revert to recursive algorithm if we do)
1931 // because relying on llvm to consteval all this is… well, it makes me
1932 let (ctz_a, mut ctz_b) = unsafe {
1933 if a == 0 { return b; }
1934 if b == 0 { return a; }
1935 (::intrinsics::cttz_nonzero(a), ::intrinsics::cttz_nonzero(b))
1937 let k = ctz_a.min(ctz_b);
1938 let mut a = a >> ctz_a;
1941 // remove all factors of 2 from b
1944 ::mem::swap(&mut a, &mut b);
1951 ctz_b = ::intrinsics::cttz_nonzero(b);
1956 let gcd: usize = gcd(::mem::size_of::<T>(), ::mem::size_of::<U>());
1957 let ts: usize = ::mem::size_of::<U>() / gcd;
1958 let us: usize = ::mem::size_of::<T>() / gcd;
1960 // Armed with this knowledge, we can find how many `U`s we can fit!
1961 let us_len = self.len() / ts * us;
1962 // And how many `T`s will be in the trailing slice!
1963 let ts_len = self.len() % ts;
1967 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
1970 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
1971 /// slice of a new type, and the suffix slice. The method does a best effort to make the
1972 /// middle slice the greatest length possible for a given type and input slice, but only
1973 /// your algorithm's performance should depend on that, not its correctness.
1975 /// This method has no purpose when either input element `T` or output element `U` are
1976 /// zero-sized and will return the original slice without splitting anything.
1980 /// This method is essentially a `transmute` with respect to the elements in the returned
1981 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
1989 /// let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
1990 /// let (prefix, shorts, suffix) = bytes.align_to::<u16>();
1991 /// // less_efficient_algorithm_for_bytes(prefix);
1992 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
1993 /// // less_efficient_algorithm_for_bytes(suffix);
1996 #[stable(feature = "slice_align_to", since = "1.30.0")]
1997 pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T]) {
1998 // Note that most of this function will be constant-evaluated,
1999 if ::mem::size_of::<U>() == 0 || ::mem::size_of::<T>() == 0 {
2000 // handle ZSTs specially, which is – don't handle them at all.
2001 return (self, &[], &[]);
2004 // First, find at what point do we split between the first and 2nd slice. Easy with
2005 // ptr.align_offset.
2006 let ptr = self.as_ptr();
2007 let offset = ::ptr::align_offset(ptr, ::mem::align_of::<U>());
2008 if offset > self.len() {
2011 let (left, rest) = self.split_at(offset);
2012 // now `rest` is definitely aligned, so `from_raw_parts_mut` below is okay
2013 let (us_len, ts_len) = rest.align_to_offsets::<U>();
2015 from_raw_parts(rest.as_ptr() as *const U, us_len),
2016 from_raw_parts(rest.as_ptr().add(rest.len() - ts_len), ts_len))
2020 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
2023 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
2024 /// slice of a new type, and the suffix slice. The method does a best effort to make the
2025 /// middle slice the greatest length possible for a given type and input slice, but only
2026 /// your algorithm's performance should depend on that, not its correctness.
2028 /// This method has no purpose when either input element `T` or output element `U` are
2029 /// zero-sized and will return the original slice without splitting anything.
2033 /// This method is essentially a `transmute` with respect to the elements in the returned
2034 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
2042 /// let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
2043 /// let (prefix, shorts, suffix) = bytes.align_to_mut::<u16>();
2044 /// // less_efficient_algorithm_for_bytes(prefix);
2045 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
2046 /// // less_efficient_algorithm_for_bytes(suffix);
2049 #[stable(feature = "slice_align_to", since = "1.30.0")]
2050 pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T]) {
2051 // Note that most of this function will be constant-evaluated,
2052 if ::mem::size_of::<U>() == 0 || ::mem::size_of::<T>() == 0 {
2053 // handle ZSTs specially, which is – don't handle them at all.
2054 return (self, &mut [], &mut []);
2057 // First, find at what point do we split between the first and 2nd slice. Easy with
2058 // ptr.align_offset.
2059 let ptr = self.as_ptr();
2060 let offset = ::ptr::align_offset(ptr, ::mem::align_of::<U>());
2061 if offset > self.len() {
2062 (self, &mut [], &mut [])
2064 let (left, rest) = self.split_at_mut(offset);
2065 // now `rest` is definitely aligned, so `from_raw_parts_mut` below is okay
2066 let (us_len, ts_len) = rest.align_to_offsets::<U>();
2067 let mut_ptr = rest.as_mut_ptr();
2069 from_raw_parts_mut(mut_ptr as *mut U, us_len),
2070 from_raw_parts_mut(mut_ptr.add(rest.len() - ts_len), ts_len))
2075 #[lang = "slice_u8"]
2078 /// Checks if all bytes in this slice are within the ASCII range.
2079 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2081 pub fn is_ascii(&self) -> bool {
2082 self.iter().all(|b| b.is_ascii())
2085 /// Checks that two slices are an ASCII case-insensitive match.
2087 /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
2088 /// but without allocating and copying temporaries.
2089 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2091 pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool {
2092 self.len() == other.len() &&
2093 self.iter().zip(other).all(|(a, b)| {
2094 a.eq_ignore_ascii_case(b)
2098 /// Converts this slice to its ASCII upper case equivalent in-place.
2100 /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
2101 /// but non-ASCII letters are unchanged.
2103 /// To return a new uppercased value without modifying the existing one, use
2104 /// [`to_ascii_uppercase`].
2106 /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
2107 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2109 pub fn make_ascii_uppercase(&mut self) {
2111 byte.make_ascii_uppercase();
2115 /// Converts this slice to its ASCII lower case equivalent in-place.
2117 /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
2118 /// but non-ASCII letters are unchanged.
2120 /// To return a new lowercased value without modifying the existing one, use
2121 /// [`to_ascii_lowercase`].
2123 /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
2124 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2126 pub fn make_ascii_lowercase(&mut self) {
2128 byte.make_ascii_lowercase();
2134 #[stable(feature = "rust1", since = "1.0.0")]
2135 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
2136 impl<T, I> ops::Index<I> for [T]
2137 where I: SliceIndex<[T]>
2139 type Output = I::Output;
2142 fn index(&self, index: I) -> &I::Output {
2147 #[stable(feature = "rust1", since = "1.0.0")]
2148 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
2149 impl<T, I> ops::IndexMut<I> for [T]
2150 where I: SliceIndex<[T]>
2153 fn index_mut(&mut self, index: I) -> &mut I::Output {
2154 index.index_mut(self)
2160 fn slice_index_len_fail(index: usize, len: usize) -> ! {
2161 panic!("index {} out of range for slice of length {}", index, len);
2166 fn slice_index_order_fail(index: usize, end: usize) -> ! {
2167 panic!("slice index starts at {} but ends at {}", index, end);
2172 fn slice_index_overflow_fail() -> ! {
2173 panic!("attempted to index slice up to maximum usize");
2176 mod private_slice_index {
2178 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2181 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2182 impl Sealed for usize {}
2183 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2184 impl Sealed for ops::Range<usize> {}
2185 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2186 impl Sealed for ops::RangeTo<usize> {}
2187 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2188 impl Sealed for ops::RangeFrom<usize> {}
2189 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2190 impl Sealed for ops::RangeFull {}
2191 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2192 impl Sealed for ops::RangeInclusive<usize> {}
2193 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2194 impl Sealed for ops::RangeToInclusive<usize> {}
2197 /// A helper trait used for indexing operations.
2198 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2199 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
2200 pub trait SliceIndex<T: ?Sized>: private_slice_index::Sealed {
2201 /// The output type returned by methods.
2202 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2203 type Output: ?Sized;
2205 /// Returns a shared reference to the output at this location, if in
2207 #[unstable(feature = "slice_index_methods", issue = "0")]
2208 fn get(self, slice: &T) -> Option<&Self::Output>;
2210 /// Returns a mutable reference to the output at this location, if in
2212 #[unstable(feature = "slice_index_methods", issue = "0")]
2213 fn get_mut(self, slice: &mut T) -> Option<&mut Self::Output>;
2215 /// Returns a shared reference to the output at this location, without
2216 /// performing any bounds checking.
2217 #[unstable(feature = "slice_index_methods", issue = "0")]
2218 unsafe fn get_unchecked(self, slice: &T) -> &Self::Output;
2220 /// Returns a mutable reference to the output at this location, without
2221 /// performing any bounds checking.
2222 #[unstable(feature = "slice_index_methods", issue = "0")]
2223 unsafe fn get_unchecked_mut(self, slice: &mut T) -> &mut Self::Output;
2225 /// Returns a shared reference to the output at this location, panicking
2226 /// if out of bounds.
2227 #[unstable(feature = "slice_index_methods", issue = "0")]
2228 fn index(self, slice: &T) -> &Self::Output;
2230 /// Returns a mutable reference to the output at this location, panicking
2231 /// if out of bounds.
2232 #[unstable(feature = "slice_index_methods", issue = "0")]
2233 fn index_mut(self, slice: &mut T) -> &mut Self::Output;
2236 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2237 impl<T> SliceIndex<[T]> for usize {
2241 fn get(self, slice: &[T]) -> Option<&T> {
2242 if self < slice.len() {
2244 Some(self.get_unchecked(slice))
2252 fn get_mut(self, slice: &mut [T]) -> Option<&mut T> {
2253 if self < slice.len() {
2255 Some(self.get_unchecked_mut(slice))
2263 unsafe fn get_unchecked(self, slice: &[T]) -> &T {
2264 &*slice.as_ptr().add(self)
2268 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut T {
2269 &mut *slice.as_mut_ptr().add(self)
2273 fn index(self, slice: &[T]) -> &T {
2274 // NB: use intrinsic indexing
2279 fn index_mut(self, slice: &mut [T]) -> &mut T {
2280 // NB: use intrinsic indexing
2285 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2286 impl<T> SliceIndex<[T]> for ops::Range<usize> {
2290 fn get(self, slice: &[T]) -> Option<&[T]> {
2291 if self.start > self.end || self.end > slice.len() {
2295 Some(self.get_unchecked(slice))
2301 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2302 if self.start > self.end || self.end > slice.len() {
2306 Some(self.get_unchecked_mut(slice))
2312 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2313 from_raw_parts(slice.as_ptr().add(self.start), self.end - self.start)
2317 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2318 from_raw_parts_mut(slice.as_mut_ptr().add(self.start), self.end - self.start)
2322 fn index(self, slice: &[T]) -> &[T] {
2323 if self.start > self.end {
2324 slice_index_order_fail(self.start, self.end);
2325 } else if self.end > slice.len() {
2326 slice_index_len_fail(self.end, slice.len());
2329 self.get_unchecked(slice)
2334 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2335 if self.start > self.end {
2336 slice_index_order_fail(self.start, self.end);
2337 } else if self.end > slice.len() {
2338 slice_index_len_fail(self.end, slice.len());
2341 self.get_unchecked_mut(slice)
2346 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2347 impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {
2351 fn get(self, slice: &[T]) -> Option<&[T]> {
2352 (0..self.end).get(slice)
2356 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2357 (0..self.end).get_mut(slice)
2361 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2362 (0..self.end).get_unchecked(slice)
2366 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2367 (0..self.end).get_unchecked_mut(slice)
2371 fn index(self, slice: &[T]) -> &[T] {
2372 (0..self.end).index(slice)
2376 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2377 (0..self.end).index_mut(slice)
2381 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2382 impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {
2386 fn get(self, slice: &[T]) -> Option<&[T]> {
2387 (self.start..slice.len()).get(slice)
2391 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2392 (self.start..slice.len()).get_mut(slice)
2396 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2397 (self.start..slice.len()).get_unchecked(slice)
2401 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2402 (self.start..slice.len()).get_unchecked_mut(slice)
2406 fn index(self, slice: &[T]) -> &[T] {
2407 (self.start..slice.len()).index(slice)
2411 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2412 (self.start..slice.len()).index_mut(slice)
2416 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2417 impl<T> SliceIndex<[T]> for ops::RangeFull {
2421 fn get(self, slice: &[T]) -> Option<&[T]> {
2426 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2431 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2436 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2441 fn index(self, slice: &[T]) -> &[T] {
2446 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2452 #[stable(feature = "inclusive_range", since = "1.26.0")]
2453 impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> {
2457 fn get(self, slice: &[T]) -> Option<&[T]> {
2458 if *self.end() == usize::max_value() { None }
2459 else { (*self.start()..self.end() + 1).get(slice) }
2463 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2464 if *self.end() == usize::max_value() { None }
2465 else { (*self.start()..self.end() + 1).get_mut(slice) }
2469 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2470 (*self.start()..self.end() + 1).get_unchecked(slice)
2474 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2475 (*self.start()..self.end() + 1).get_unchecked_mut(slice)
2479 fn index(self, slice: &[T]) -> &[T] {
2480 if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
2481 (*self.start()..self.end() + 1).index(slice)
2485 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2486 if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
2487 (*self.start()..self.end() + 1).index_mut(slice)
2491 #[stable(feature = "inclusive_range", since = "1.26.0")]
2492 impl<T> SliceIndex<[T]> for ops::RangeToInclusive<usize> {
2496 fn get(self, slice: &[T]) -> Option<&[T]> {
2497 (0..=self.end).get(slice)
2501 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2502 (0..=self.end).get_mut(slice)
2506 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2507 (0..=self.end).get_unchecked(slice)
2511 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2512 (0..=self.end).get_unchecked_mut(slice)
2516 fn index(self, slice: &[T]) -> &[T] {
2517 (0..=self.end).index(slice)
2521 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2522 (0..=self.end).index_mut(slice)
2526 ////////////////////////////////////////////////////////////////////////////////
2528 ////////////////////////////////////////////////////////////////////////////////
2530 #[stable(feature = "rust1", since = "1.0.0")]
2531 impl<'a, T> Default for &'a [T] {
2532 /// Creates an empty slice.
2533 fn default() -> &'a [T] { &[] }
2536 #[stable(feature = "mut_slice_default", since = "1.5.0")]
2537 impl<'a, T> Default for &'a mut [T] {
2538 /// Creates a mutable empty slice.
2539 fn default() -> &'a mut [T] { &mut [] }
2546 #[stable(feature = "rust1", since = "1.0.0")]
2547 impl<'a, T> IntoIterator for &'a [T] {
2549 type IntoIter = Iter<'a, T>;
2551 fn into_iter(self) -> Iter<'a, T> {
2556 #[stable(feature = "rust1", since = "1.0.0")]
2557 impl<'a, T> IntoIterator for &'a mut [T] {
2558 type Item = &'a mut T;
2559 type IntoIter = IterMut<'a, T>;
2561 fn into_iter(self) -> IterMut<'a, T> {
2566 // Macro helper functions
2568 fn size_from_ptr<T>(_: *const T) -> usize {
2572 // Inlining is_empty and len makes a huge performance difference
2573 macro_rules! is_empty {
2574 // The way we encode the length of a ZST iterator, this works both for ZST
2576 ($self: ident) => {$self.ptr == $self.end}
2578 // To get rid of some bounds checks (see `position`), we compute the length in a somewhat
2579 // unexpected way. (Tested by `codegen/slice-position-bounds-check`.)
2581 ($self: ident) => {{
2582 let start = $self.ptr;
2583 let diff = ($self.end as usize).wrapping_sub(start as usize);
2584 let size = size_from_ptr(start);
2588 // Using division instead of `offset_from` helps LLVM remove bounds checks
2594 // The shared definition of the `Iter` and `IterMut` iterators
2595 macro_rules! iterator {
2596 (struct $name:ident -> $ptr:ty, $elem:ty, $raw_mut:tt, $( $mut_:tt )*) => {
2597 impl<'a, T> $name<'a, T> {
2598 // Helper function for creating a slice from the iterator.
2600 fn make_slice(&self) -> &'a [T] {
2601 unsafe { from_raw_parts(self.ptr, len!(self)) }
2604 // Helper function for moving the start of the iterator forwards by `offset` elements,
2605 // returning the old start.
2606 // Unsafe because the offset must be in-bounds or one-past-the-end.
2608 unsafe fn post_inc_start(&mut self, offset: isize) -> * $raw_mut T {
2609 if mem::size_of::<T>() == 0 {
2610 // This is *reducing* the length. `ptr` never changes with ZST.
2611 self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
2615 self.ptr = self.ptr.offset(offset);
2620 // Helper function for moving the end of the iterator backwards by `offset` elements,
2621 // returning the new end.
2622 // Unsafe because the offset must be in-bounds or one-past-the-end.
2624 unsafe fn pre_dec_end(&mut self, offset: isize) -> * $raw_mut T {
2625 if mem::size_of::<T>() == 0 {
2626 self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
2629 self.end = self.end.offset(-offset);
2635 #[stable(feature = "rust1", since = "1.0.0")]
2636 impl<'a, T> ExactSizeIterator for $name<'a, T> {
2638 fn len(&self) -> usize {
2643 fn is_empty(&self) -> bool {
2648 #[stable(feature = "rust1", since = "1.0.0")]
2649 impl<'a, T> Iterator for $name<'a, T> {
2653 fn next(&mut self) -> Option<$elem> {
2654 // could be implemented with slices, but this avoids bounds checks
2656 assume(!self.ptr.is_null());
2657 if mem::size_of::<T>() != 0 {
2658 assume(!self.end.is_null());
2660 if is_empty!(self) {
2663 Some(& $( $mut_ )* *self.post_inc_start(1))
2669 fn size_hint(&self) -> (usize, Option<usize>) {
2670 let exact = len!(self);
2671 (exact, Some(exact))
2675 fn count(self) -> usize {
2680 fn nth(&mut self, n: usize) -> Option<$elem> {
2681 if n >= len!(self) {
2682 // This iterator is now empty.
2683 if mem::size_of::<T>() == 0 {
2684 // We have to do it this way as `ptr` may never be 0, but `end`
2685 // could be (due to wrapping).
2686 self.end = self.ptr;
2688 self.ptr = self.end;
2692 // We are in bounds. `offset` does the right thing even for ZSTs.
2694 let elem = Some(& $( $mut_ )* *self.ptr.add(n));
2695 self.post_inc_start((n as isize).wrapping_add(1));
2701 fn last(mut self) -> Option<$elem> {
2706 fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where
2707 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
2709 // manual unrolling is needed when there are conditional exits from the loop
2710 let mut accum = init;
2712 while len!(self) >= 4 {
2713 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2714 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2715 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2716 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2718 while !is_empty!(self) {
2719 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2726 fn fold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
2727 where Fold: FnMut(Acc, Self::Item) -> Acc,
2729 // Let LLVM unroll this, rather than using the default
2730 // impl that would force the manual unrolling above
2731 let mut accum = init;
2732 while let Some(x) = self.next() {
2733 accum = f(accum, x);
2739 #[rustc_inherit_overflow_checks]
2740 fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
2742 P: FnMut(Self::Item) -> bool,
2744 // The addition might panic on overflow.
2746 self.try_fold(0, move |i, x| {
2747 if predicate(x) { Err(i) }
2751 unsafe { assume(i < n) };
2757 fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where
2758 P: FnMut(Self::Item) -> bool,
2759 Self: Sized + ExactSizeIterator + DoubleEndedIterator
2761 // No need for an overflow check here, because `ExactSizeIterator`
2763 self.try_rfold(n, move |i, x| {
2765 if predicate(x) { Err(i) }
2769 unsafe { assume(i < n) };
2775 #[stable(feature = "rust1", since = "1.0.0")]
2776 impl<'a, T> DoubleEndedIterator for $name<'a, T> {
2778 fn next_back(&mut self) -> Option<$elem> {
2779 // could be implemented with slices, but this avoids bounds checks
2781 assume(!self.ptr.is_null());
2782 if mem::size_of::<T>() != 0 {
2783 assume(!self.end.is_null());
2785 if is_empty!(self) {
2788 Some(& $( $mut_ )* *self.pre_dec_end(1))
2794 fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where
2795 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
2797 // manual unrolling is needed when there are conditional exits from the loop
2798 let mut accum = init;
2800 while len!(self) >= 4 {
2801 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2802 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2803 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2804 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2806 // inlining is_empty everywhere makes a huge performance difference
2807 while !is_empty!(self) {
2808 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2815 fn rfold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
2816 where Fold: FnMut(Acc, Self::Item) -> Acc,
2818 // Let LLVM unroll this, rather than using the default
2819 // impl that would force the manual unrolling above
2820 let mut accum = init;
2821 while let Some(x) = self.next_back() {
2822 accum = f(accum, x);
2828 #[stable(feature = "fused", since = "1.26.0")]
2829 impl<'a, T> FusedIterator for $name<'a, T> {}
2831 #[unstable(feature = "trusted_len", issue = "37572")]
2832 unsafe impl<'a, T> TrustedLen for $name<'a, T> {}
2836 /// Immutable slice iterator
2838 /// This struct is created by the [`iter`] method on [slices].
2845 /// // First, we declare a type which has `iter` method to get the `Iter` struct (&[usize here]):
2846 /// let slice = &[1, 2, 3];
2848 /// // Then, we iterate over it:
2849 /// for element in slice.iter() {
2850 /// println!("{}", element);
2854 /// [`iter`]: ../../std/primitive.slice.html#method.iter
2855 /// [slices]: ../../std/primitive.slice.html
2856 #[stable(feature = "rust1", since = "1.0.0")]
2857 pub struct Iter<'a, T: 'a> {
2859 end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
2860 // ptr == end is a quick test for the Iterator being empty, that works
2861 // for both ZST and non-ZST.
2862 _marker: marker::PhantomData<&'a T>,
2865 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2866 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
2867 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2868 f.debug_tuple("Iter")
2869 .field(&self.as_slice())
2874 #[stable(feature = "rust1", since = "1.0.0")]
2875 unsafe impl<'a, T: Sync> Sync for Iter<'a, T> {}
2876 #[stable(feature = "rust1", since = "1.0.0")]
2877 unsafe impl<'a, T: Sync> Send for Iter<'a, T> {}
2879 impl<'a, T> Iter<'a, T> {
2880 /// View the underlying data as a subslice of the original data.
2882 /// This has the same lifetime as the original slice, and so the
2883 /// iterator can continue to be used while this exists.
2890 /// // First, we declare a type which has the `iter` method to get the `Iter`
2891 /// // struct (&[usize here]):
2892 /// let slice = &[1, 2, 3];
2894 /// // Then, we get the iterator:
2895 /// let mut iter = slice.iter();
2896 /// // So if we print what `as_slice` method returns here, we have "[1, 2, 3]":
2897 /// println!("{:?}", iter.as_slice());
2899 /// // Next, we move to the second element of the slice:
2901 /// // Now `as_slice` returns "[2, 3]":
2902 /// println!("{:?}", iter.as_slice());
2904 #[stable(feature = "iter_to_slice", since = "1.4.0")]
2905 pub fn as_slice(&self) -> &'a [T] {
2910 iterator!{struct Iter -> *const T, &'a T, const, /* no mut */}
2912 #[stable(feature = "rust1", since = "1.0.0")]
2913 impl<'a, T> Clone for Iter<'a, T> {
2914 fn clone(&self) -> Iter<'a, T> { Iter { ptr: self.ptr, end: self.end, _marker: self._marker } }
2917 #[stable(feature = "slice_iter_as_ref", since = "1.13.0")]
2918 impl<'a, T> AsRef<[T]> for Iter<'a, T> {
2919 fn as_ref(&self) -> &[T] {
2924 /// Mutable slice iterator.
2926 /// This struct is created by the [`iter_mut`] method on [slices].
2933 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
2934 /// // struct (&[usize here]):
2935 /// let mut slice = &mut [1, 2, 3];
2937 /// // Then, we iterate over it and increment each element value:
2938 /// for element in slice.iter_mut() {
2942 /// // We now have "[2, 3, 4]":
2943 /// println!("{:?}", slice);
2946 /// [`iter_mut`]: ../../std/primitive.slice.html#method.iter_mut
2947 /// [slices]: ../../std/primitive.slice.html
2948 #[stable(feature = "rust1", since = "1.0.0")]
2949 pub struct IterMut<'a, T: 'a> {
2951 end: *mut T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
2952 // ptr == end is a quick test for the Iterator being empty, that works
2953 // for both ZST and non-ZST.
2954 _marker: marker::PhantomData<&'a mut T>,
2957 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2958 impl<'a, T: 'a + fmt::Debug> fmt::Debug for IterMut<'a, T> {
2959 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2960 f.debug_tuple("IterMut")
2961 .field(&self.make_slice())
2966 #[stable(feature = "rust1", since = "1.0.0")]
2967 unsafe impl<'a, T: Sync> Sync for IterMut<'a, T> {}
2968 #[stable(feature = "rust1", since = "1.0.0")]
2969 unsafe impl<'a, T: Send> Send for IterMut<'a, T> {}
2971 impl<'a, T> IterMut<'a, T> {
2972 /// View the underlying data as a subslice of the original data.
2974 /// To avoid creating `&mut` references that alias, this is forced
2975 /// to consume the iterator.
2982 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
2983 /// // struct (&[usize here]):
2984 /// let mut slice = &mut [1, 2, 3];
2987 /// // Then, we get the iterator:
2988 /// let mut iter = slice.iter_mut();
2989 /// // We move to next element:
2991 /// // So if we print what `into_slice` method returns here, we have "[2, 3]":
2992 /// println!("{:?}", iter.into_slice());
2995 /// // Now let's modify a value of the slice:
2997 /// // First we get back the iterator:
2998 /// let mut iter = slice.iter_mut();
2999 /// // We change the value of the first element of the slice returned by the `next` method:
3000 /// *iter.next().unwrap() += 1;
3002 /// // Now slice is "[2, 2, 3]":
3003 /// println!("{:?}", slice);
3005 #[stable(feature = "iter_to_slice", since = "1.4.0")]
3006 pub fn into_slice(self) -> &'a mut [T] {
3007 unsafe { from_raw_parts_mut(self.ptr, len!(self)) }
3011 iterator!{struct IterMut -> *mut T, &'a mut T, mut, mut}
3013 /// An internal abstraction over the splitting iterators, so that
3014 /// splitn, splitn_mut etc can be implemented once.
3016 trait SplitIter: DoubleEndedIterator {
3017 /// Marks the underlying iterator as complete, extracting the remaining
3018 /// portion of the slice.
3019 fn finish(&mut self) -> Option<Self::Item>;
3022 /// An iterator over subslices separated by elements that match a predicate
3025 /// This struct is created by the [`split`] method on [slices].
3027 /// [`split`]: ../../std/primitive.slice.html#method.split
3028 /// [slices]: ../../std/primitive.slice.html
3029 #[stable(feature = "rust1", since = "1.0.0")]
3030 pub struct Split<'a, T:'a, P> where P: FnMut(&T) -> bool {
3036 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3037 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for Split<'a, T, P> where P: FnMut(&T) -> bool {
3038 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3039 f.debug_struct("Split")
3040 .field("v", &self.v)
3041 .field("finished", &self.finished)
3046 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3047 #[stable(feature = "rust1", since = "1.0.0")]
3048 impl<'a, T, P> Clone for Split<'a, T, P> where P: Clone + FnMut(&T) -> bool {
3049 fn clone(&self) -> Split<'a, T, P> {
3052 pred: self.pred.clone(),
3053 finished: self.finished,
3058 #[stable(feature = "rust1", since = "1.0.0")]
3059 impl<'a, T, P> Iterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
3060 type Item = &'a [T];
3063 fn next(&mut self) -> Option<&'a [T]> {
3064 if self.finished { return None; }
3066 match self.v.iter().position(|x| (self.pred)(x)) {
3067 None => self.finish(),
3069 let ret = Some(&self.v[..idx]);
3070 self.v = &self.v[idx + 1..];
3077 fn size_hint(&self) -> (usize, Option<usize>) {
3081 (1, Some(self.v.len() + 1))
3086 #[stable(feature = "rust1", since = "1.0.0")]
3087 impl<'a, T, P> DoubleEndedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
3089 fn next_back(&mut self) -> Option<&'a [T]> {
3090 if self.finished { return None; }
3092 match self.v.iter().rposition(|x| (self.pred)(x)) {
3093 None => self.finish(),
3095 let ret = Some(&self.v[idx + 1..]);
3096 self.v = &self.v[..idx];
3103 impl<'a, T, P> SplitIter for Split<'a, T, P> where P: FnMut(&T) -> bool {
3105 fn finish(&mut self) -> Option<&'a [T]> {
3106 if self.finished { None } else { self.finished = true; Some(self.v) }
3110 #[stable(feature = "fused", since = "1.26.0")]
3111 impl<'a, T, P> FusedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {}
3113 /// An iterator over the subslices of the vector which are separated
3114 /// by elements that match `pred`.
3116 /// This struct is created by the [`split_mut`] method on [slices].
3118 /// [`split_mut`]: ../../std/primitive.slice.html#method.split_mut
3119 /// [slices]: ../../std/primitive.slice.html
3120 #[stable(feature = "rust1", since = "1.0.0")]
3121 pub struct SplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
3127 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3128 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3129 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3130 f.debug_struct("SplitMut")
3131 .field("v", &self.v)
3132 .field("finished", &self.finished)
3137 impl<'a, T, P> SplitIter for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3139 fn finish(&mut self) -> Option<&'a mut [T]> {
3143 self.finished = true;
3144 Some(mem::replace(&mut self.v, &mut []))
3149 #[stable(feature = "rust1", since = "1.0.0")]
3150 impl<'a, T, P> Iterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3151 type Item = &'a mut [T];
3154 fn next(&mut self) -> Option<&'a mut [T]> {
3155 if self.finished { return None; }
3157 let idx_opt = { // work around borrowck limitations
3158 let pred = &mut self.pred;
3159 self.v.iter().position(|x| (*pred)(x))
3162 None => self.finish(),
3164 let tmp = mem::replace(&mut self.v, &mut []);
3165 let (head, tail) = tmp.split_at_mut(idx);
3166 self.v = &mut tail[1..];
3173 fn size_hint(&self) -> (usize, Option<usize>) {
3177 // if the predicate doesn't match anything, we yield one slice
3178 // if it matches every element, we yield len+1 empty slices.
3179 (1, Some(self.v.len() + 1))
3184 #[stable(feature = "rust1", since = "1.0.0")]
3185 impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> where
3186 P: FnMut(&T) -> bool,
3189 fn next_back(&mut self) -> Option<&'a mut [T]> {
3190 if self.finished { return None; }
3192 let idx_opt = { // work around borrowck limitations
3193 let pred = &mut self.pred;
3194 self.v.iter().rposition(|x| (*pred)(x))
3197 None => self.finish(),
3199 let tmp = mem::replace(&mut self.v, &mut []);
3200 let (head, tail) = tmp.split_at_mut(idx);
3202 Some(&mut tail[1..])
3208 #[stable(feature = "fused", since = "1.26.0")]
3209 impl<'a, T, P> FusedIterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {}
3211 /// An iterator over subslices separated by elements that match a predicate
3212 /// function, starting from the end of the slice.
3214 /// This struct is created by the [`rsplit`] method on [slices].
3216 /// [`rsplit`]: ../../std/primitive.slice.html#method.rsplit
3217 /// [slices]: ../../std/primitive.slice.html
3218 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3219 #[derive(Clone)] // Is this correct, or does it incorrectly require `T: Clone`?
3220 pub struct RSplit<'a, T:'a, P> where P: FnMut(&T) -> bool {
3221 inner: Split<'a, T, P>
3224 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3225 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3226 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3227 f.debug_struct("RSplit")
3228 .field("v", &self.inner.v)
3229 .field("finished", &self.inner.finished)
3234 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3235 impl<'a, T, P> Iterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3236 type Item = &'a [T];
3239 fn next(&mut self) -> Option<&'a [T]> {
3240 self.inner.next_back()
3244 fn size_hint(&self) -> (usize, Option<usize>) {
3245 self.inner.size_hint()
3249 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3250 impl<'a, T, P> DoubleEndedIterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3252 fn next_back(&mut self) -> Option<&'a [T]> {
3257 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3258 impl<'a, T, P> SplitIter for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3260 fn finish(&mut self) -> Option<&'a [T]> {
3265 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3266 impl<'a, T, P> FusedIterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {}
3268 /// An iterator over the subslices of the vector which are separated
3269 /// by elements that match `pred`, starting from the end of the slice.
3271 /// This struct is created by the [`rsplit_mut`] method on [slices].
3273 /// [`rsplit_mut`]: ../../std/primitive.slice.html#method.rsplit_mut
3274 /// [slices]: ../../std/primitive.slice.html
3275 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3276 pub struct RSplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
3277 inner: SplitMut<'a, T, P>
3280 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3281 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3282 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3283 f.debug_struct("RSplitMut")
3284 .field("v", &self.inner.v)
3285 .field("finished", &self.inner.finished)
3290 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3291 impl<'a, T, P> SplitIter for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3293 fn finish(&mut self) -> Option<&'a mut [T]> {
3298 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3299 impl<'a, T, P> Iterator for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3300 type Item = &'a mut [T];
3303 fn next(&mut self) -> Option<&'a mut [T]> {
3304 self.inner.next_back()
3308 fn size_hint(&self) -> (usize, Option<usize>) {
3309 self.inner.size_hint()
3313 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3314 impl<'a, T, P> DoubleEndedIterator for RSplitMut<'a, T, P> where
3315 P: FnMut(&T) -> bool,
3318 fn next_back(&mut self) -> Option<&'a mut [T]> {
3323 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3324 impl<'a, T, P> FusedIterator for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {}
3326 /// An private iterator over subslices separated by elements that
3327 /// match a predicate function, splitting at most a fixed number of
3330 struct GenericSplitN<I> {
3335 impl<T, I: SplitIter<Item=T>> Iterator for GenericSplitN<I> {
3339 fn next(&mut self) -> Option<T> {
3342 1 => { self.count -= 1; self.iter.finish() }
3343 _ => { self.count -= 1; self.iter.next() }
3348 fn size_hint(&self) -> (usize, Option<usize>) {
3349 let (lower, upper_opt) = self.iter.size_hint();
3350 (lower, upper_opt.map(|upper| cmp::min(self.count, upper)))
3354 /// An iterator over subslices separated by elements that match a predicate
3355 /// function, limited to a given number of splits.
3357 /// This struct is created by the [`splitn`] method on [slices].
3359 /// [`splitn`]: ../../std/primitive.slice.html#method.splitn
3360 /// [slices]: ../../std/primitive.slice.html
3361 #[stable(feature = "rust1", since = "1.0.0")]
3362 pub struct SplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3363 inner: GenericSplitN<Split<'a, T, P>>
3366 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3367 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitN<'a, T, P> where P: FnMut(&T) -> bool {
3368 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3369 f.debug_struct("SplitN")
3370 .field("inner", &self.inner)
3375 /// An iterator over subslices separated by elements that match a
3376 /// predicate function, limited to a given number of splits, starting
3377 /// from the end of the slice.
3379 /// This struct is created by the [`rsplitn`] method on [slices].
3381 /// [`rsplitn`]: ../../std/primitive.slice.html#method.rsplitn
3382 /// [slices]: ../../std/primitive.slice.html
3383 #[stable(feature = "rust1", since = "1.0.0")]
3384 pub struct RSplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3385 inner: GenericSplitN<RSplit<'a, T, P>>
3388 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3389 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitN<'a, T, P> where P: FnMut(&T) -> bool {
3390 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3391 f.debug_struct("RSplitN")
3392 .field("inner", &self.inner)
3397 /// An iterator over subslices separated by elements that match a predicate
3398 /// function, limited to a given number of splits.
3400 /// This struct is created by the [`splitn_mut`] method on [slices].
3402 /// [`splitn_mut`]: ../../std/primitive.slice.html#method.splitn_mut
3403 /// [slices]: ../../std/primitive.slice.html
3404 #[stable(feature = "rust1", since = "1.0.0")]
3405 pub struct SplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3406 inner: GenericSplitN<SplitMut<'a, T, P>>
3409 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3410 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitNMut<'a, T, P> where P: FnMut(&T) -> bool {
3411 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3412 f.debug_struct("SplitNMut")
3413 .field("inner", &self.inner)
3418 /// An iterator over subslices separated by elements that match a
3419 /// predicate function, limited to a given number of splits, starting
3420 /// from the end of the slice.
3422 /// This struct is created by the [`rsplitn_mut`] method on [slices].
3424 /// [`rsplitn_mut`]: ../../std/primitive.slice.html#method.rsplitn_mut
3425 /// [slices]: ../../std/primitive.slice.html
3426 #[stable(feature = "rust1", since = "1.0.0")]
3427 pub struct RSplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3428 inner: GenericSplitN<RSplitMut<'a, T, P>>
3431 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3432 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitNMut<'a, T, P> where P: FnMut(&T) -> bool {
3433 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3434 f.debug_struct("RSplitNMut")
3435 .field("inner", &self.inner)
3440 macro_rules! forward_iterator {
3441 ($name:ident: $elem:ident, $iter_of:ty) => {
3442 #[stable(feature = "rust1", since = "1.0.0")]
3443 impl<'a, $elem, P> Iterator for $name<'a, $elem, P> where
3444 P: FnMut(&T) -> bool
3446 type Item = $iter_of;
3449 fn next(&mut self) -> Option<$iter_of> {
3454 fn size_hint(&self) -> (usize, Option<usize>) {
3455 self.inner.size_hint()
3459 #[stable(feature = "fused", since = "1.26.0")]
3460 impl<'a, $elem, P> FusedIterator for $name<'a, $elem, P>
3461 where P: FnMut(&T) -> bool {}
3465 forward_iterator! { SplitN: T, &'a [T] }
3466 forward_iterator! { RSplitN: T, &'a [T] }
3467 forward_iterator! { SplitNMut: T, &'a mut [T] }
3468 forward_iterator! { RSplitNMut: T, &'a mut [T] }
3470 /// An iterator over overlapping subslices of length `size`.
3472 /// This struct is created by the [`windows`] method on [slices].
3474 /// [`windows`]: ../../std/primitive.slice.html#method.windows
3475 /// [slices]: ../../std/primitive.slice.html
3477 #[stable(feature = "rust1", since = "1.0.0")]
3478 pub struct Windows<'a, T:'a> {
3483 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3484 #[stable(feature = "rust1", since = "1.0.0")]
3485 impl<'a, T> Clone for Windows<'a, T> {
3486 fn clone(&self) -> Windows<'a, T> {
3494 #[stable(feature = "rust1", since = "1.0.0")]
3495 impl<'a, T> Iterator for Windows<'a, T> {
3496 type Item = &'a [T];
3499 fn next(&mut self) -> Option<&'a [T]> {
3500 if self.size > self.v.len() {
3503 let ret = Some(&self.v[..self.size]);
3504 self.v = &self.v[1..];
3510 fn size_hint(&self) -> (usize, Option<usize>) {
3511 if self.size > self.v.len() {
3514 let size = self.v.len() - self.size + 1;
3520 fn count(self) -> usize {
3525 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3526 let (end, overflow) = self.size.overflowing_add(n);
3527 if end > self.v.len() || overflow {
3531 let nth = &self.v[n..end];
3532 self.v = &self.v[n+1..];
3538 fn last(self) -> Option<Self::Item> {
3539 if self.size > self.v.len() {
3542 let start = self.v.len() - self.size;
3543 Some(&self.v[start..])
3548 #[stable(feature = "rust1", since = "1.0.0")]
3549 impl<'a, T> DoubleEndedIterator for Windows<'a, T> {
3551 fn next_back(&mut self) -> Option<&'a [T]> {
3552 if self.size > self.v.len() {
3555 let ret = Some(&self.v[self.v.len()-self.size..]);
3556 self.v = &self.v[..self.v.len()-1];
3562 #[stable(feature = "rust1", since = "1.0.0")]
3563 impl<'a, T> ExactSizeIterator for Windows<'a, T> {}
3565 #[unstable(feature = "trusted_len", issue = "37572")]
3566 unsafe impl<'a, T> TrustedLen for Windows<'a, T> {}
3568 #[stable(feature = "fused", since = "1.26.0")]
3569 impl<'a, T> FusedIterator for Windows<'a, T> {}
3572 unsafe impl<'a, T> TrustedRandomAccess for Windows<'a, T> {
3573 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3574 from_raw_parts(self.v.as_ptr().add(i), self.size)
3576 fn may_have_side_effect() -> bool { false }
3579 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
3582 /// When the slice len is not evenly divided by the chunk size, the last slice
3583 /// of the iteration will be the remainder.
3585 /// This struct is created by the [`chunks`] method on [slices].
3587 /// [`chunks`]: ../../std/primitive.slice.html#method.chunks
3588 /// [slices]: ../../std/primitive.slice.html
3590 #[stable(feature = "rust1", since = "1.0.0")]
3591 pub struct Chunks<'a, T:'a> {
3596 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3597 #[stable(feature = "rust1", since = "1.0.0")]
3598 impl<'a, T> Clone for Chunks<'a, T> {
3599 fn clone(&self) -> Chunks<'a, T> {
3602 chunk_size: self.chunk_size,
3607 #[stable(feature = "rust1", since = "1.0.0")]
3608 impl<'a, T> Iterator for Chunks<'a, T> {
3609 type Item = &'a [T];
3612 fn next(&mut self) -> Option<&'a [T]> {
3613 if self.v.is_empty() {
3616 let chunksz = cmp::min(self.v.len(), self.chunk_size);
3617 let (fst, snd) = self.v.split_at(chunksz);
3624 fn size_hint(&self) -> (usize, Option<usize>) {
3625 if self.v.is_empty() {
3628 let n = self.v.len() / self.chunk_size;
3629 let rem = self.v.len() % self.chunk_size;
3630 let n = if rem > 0 { n+1 } else { n };
3636 fn count(self) -> usize {
3641 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3642 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3643 if start >= self.v.len() || overflow {
3647 let end = match start.checked_add(self.chunk_size) {
3648 Some(sum) => cmp::min(self.v.len(), sum),
3649 None => self.v.len(),
3651 let nth = &self.v[start..end];
3652 self.v = &self.v[end..];
3658 fn last(self) -> Option<Self::Item> {
3659 if self.v.is_empty() {
3662 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
3663 Some(&self.v[start..])
3668 #[stable(feature = "rust1", since = "1.0.0")]
3669 impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
3671 fn next_back(&mut self) -> Option<&'a [T]> {
3672 if self.v.is_empty() {
3675 let remainder = self.v.len() % self.chunk_size;
3676 let chunksz = if remainder != 0 { remainder } else { self.chunk_size };
3677 let (fst, snd) = self.v.split_at(self.v.len() - chunksz);
3684 #[stable(feature = "rust1", since = "1.0.0")]
3685 impl<'a, T> ExactSizeIterator for Chunks<'a, T> {}
3687 #[unstable(feature = "trusted_len", issue = "37572")]
3688 unsafe impl<'a, T> TrustedLen for Chunks<'a, T> {}
3690 #[stable(feature = "fused", since = "1.26.0")]
3691 impl<'a, T> FusedIterator for Chunks<'a, T> {}
3694 unsafe impl<'a, T> TrustedRandomAccess for Chunks<'a, T> {
3695 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3696 let start = i * self.chunk_size;
3697 let end = match start.checked_add(self.chunk_size) {
3698 None => self.v.len(),
3699 Some(end) => cmp::min(end, self.v.len()),
3701 from_raw_parts(self.v.as_ptr().add(start), end - start)
3703 fn may_have_side_effect() -> bool { false }
3706 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3707 /// elements at a time). When the slice len is not evenly divided by the chunk
3708 /// size, the last slice of the iteration will be the remainder.
3710 /// This struct is created by the [`chunks_mut`] method on [slices].
3712 /// [`chunks_mut`]: ../../std/primitive.slice.html#method.chunks_mut
3713 /// [slices]: ../../std/primitive.slice.html
3715 #[stable(feature = "rust1", since = "1.0.0")]
3716 pub struct ChunksMut<'a, T:'a> {
3721 #[stable(feature = "rust1", since = "1.0.0")]
3722 impl<'a, T> Iterator for ChunksMut<'a, T> {
3723 type Item = &'a mut [T];
3726 fn next(&mut self) -> Option<&'a mut [T]> {
3727 if self.v.is_empty() {
3730 let sz = cmp::min(self.v.len(), self.chunk_size);
3731 let tmp = mem::replace(&mut self.v, &mut []);
3732 let (head, tail) = tmp.split_at_mut(sz);
3739 fn size_hint(&self) -> (usize, Option<usize>) {
3740 if self.v.is_empty() {
3743 let n = self.v.len() / self.chunk_size;
3744 let rem = self.v.len() % self.chunk_size;
3745 let n = if rem > 0 { n + 1 } else { n };
3751 fn count(self) -> usize {
3756 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
3757 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3758 if start >= self.v.len() || overflow {
3762 let end = match start.checked_add(self.chunk_size) {
3763 Some(sum) => cmp::min(self.v.len(), sum),
3764 None => self.v.len(),
3766 let tmp = mem::replace(&mut self.v, &mut []);
3767 let (head, tail) = tmp.split_at_mut(end);
3768 let (_, nth) = head.split_at_mut(start);
3775 fn last(self) -> Option<Self::Item> {
3776 if self.v.is_empty() {
3779 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
3780 Some(&mut self.v[start..])
3785 #[stable(feature = "rust1", since = "1.0.0")]
3786 impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
3788 fn next_back(&mut self) -> Option<&'a mut [T]> {
3789 if self.v.is_empty() {
3792 let remainder = self.v.len() % self.chunk_size;
3793 let sz = if remainder != 0 { remainder } else { self.chunk_size };
3794 let tmp = mem::replace(&mut self.v, &mut []);
3795 let tmp_len = tmp.len();
3796 let (head, tail) = tmp.split_at_mut(tmp_len - sz);
3803 #[stable(feature = "rust1", since = "1.0.0")]
3804 impl<'a, T> ExactSizeIterator for ChunksMut<'a, T> {}
3806 #[unstable(feature = "trusted_len", issue = "37572")]
3807 unsafe impl<'a, T> TrustedLen for ChunksMut<'a, T> {}
3809 #[stable(feature = "fused", since = "1.26.0")]
3810 impl<'a, T> FusedIterator for ChunksMut<'a, T> {}
3813 unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> {
3814 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
3815 let start = i * self.chunk_size;
3816 let end = match start.checked_add(self.chunk_size) {
3817 None => self.v.len(),
3818 Some(end) => cmp::min(end, self.v.len()),
3820 from_raw_parts_mut(self.v.as_mut_ptr().add(start), end - start)
3822 fn may_have_side_effect() -> bool { false }
3825 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
3828 /// When the slice len is not evenly divided by the chunk size, the last
3829 /// up to `chunk_size-1` elements will be omitted but can be retrieved from
3830 /// the [`remainder`] function from the iterator.
3832 /// This struct is created by the [`chunks_exact`] method on [slices].
3834 /// [`chunks_exact`]: ../../std/primitive.slice.html#method.chunks_exact
3835 /// [`remainder`]: ../../std/slice/struct.ChunksExact.html#method.remainder
3836 /// [slices]: ../../std/primitive.slice.html
3838 #[unstable(feature = "chunks_exact", issue = "47115")]
3839 pub struct ChunksExact<'a, T:'a> {
3845 #[unstable(feature = "chunks_exact", issue = "47115")]
3846 impl<'a, T> ChunksExact<'a, T> {
3847 /// Return the remainder of the original slice that is not going to be
3848 /// returned by the iterator. The returned slice has at most `chunk_size-1`
3850 pub fn remainder(&self) -> &'a [T] {
3855 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3856 #[unstable(feature = "chunks_exact", issue = "47115")]
3857 impl<'a, T> Clone for ChunksExact<'a, T> {
3858 fn clone(&self) -> ChunksExact<'a, T> {
3862 chunk_size: self.chunk_size,
3867 #[unstable(feature = "chunks_exact", issue = "47115")]
3868 impl<'a, T> Iterator for ChunksExact<'a, T> {
3869 type Item = &'a [T];
3872 fn next(&mut self) -> Option<&'a [T]> {
3873 if self.v.len() < self.chunk_size {
3876 let (fst, snd) = self.v.split_at(self.chunk_size);
3883 fn size_hint(&self) -> (usize, Option<usize>) {
3884 let n = self.v.len() / self.chunk_size;
3889 fn count(self) -> usize {
3894 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3895 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3896 if start >= self.v.len() || overflow {
3900 let (_, snd) = self.v.split_at(start);
3907 fn last(mut self) -> Option<Self::Item> {
3912 #[unstable(feature = "chunks_exact", issue = "47115")]
3913 impl<'a, T> DoubleEndedIterator for ChunksExact<'a, T> {
3915 fn next_back(&mut self) -> Option<&'a [T]> {
3916 if self.v.len() < self.chunk_size {
3919 let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size);
3926 #[unstable(feature = "chunks_exact", issue = "47115")]
3927 impl<'a, T> ExactSizeIterator for ChunksExact<'a, T> {
3928 fn is_empty(&self) -> bool {
3933 #[unstable(feature = "trusted_len", issue = "37572")]
3934 unsafe impl<'a, T> TrustedLen for ChunksExact<'a, T> {}
3936 #[unstable(feature = "chunks_exact", issue = "47115")]
3937 impl<'a, T> FusedIterator for ChunksExact<'a, T> {}
3940 unsafe impl<'a, T> TrustedRandomAccess for ChunksExact<'a, T> {
3941 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3942 let start = i * self.chunk_size;
3943 from_raw_parts(self.v.as_ptr().add(start), self.chunk_size)
3945 fn may_have_side_effect() -> bool { false }
3948 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3949 /// elements at a time).
3951 /// When the slice len is not evenly divided by the chunk size, the last up to
3952 /// `chunk_size-1` elements will be omitted but can be retrieved from the
3953 /// [`into_remainder`] function from the iterator.
3955 /// This struct is created by the [`chunks_exact_mut`] method on [slices].
3957 /// [`chunks_exact_mut`]: ../../std/primitive.slice.html#method.chunks_exact_mut
3958 /// [`into_remainder`]: ../../std/slice/struct.ChunksExactMut.html#method.into_remainder
3959 /// [slices]: ../../std/primitive.slice.html
3961 #[unstable(feature = "chunks_exact", issue = "47115")]
3962 pub struct ChunksExactMut<'a, T:'a> {
3968 #[unstable(feature = "chunks_exact", issue = "47115")]
3969 impl<'a, T> ChunksExactMut<'a, T> {
3970 /// Return the remainder of the original slice that is not going to be
3971 /// returned by the iterator. The returned slice has at most `chunk_size-1`
3973 pub fn into_remainder(self) -> &'a mut [T] {
3978 #[unstable(feature = "chunks_exact", issue = "47115")]
3979 impl<'a, T> Iterator for ChunksExactMut<'a, T> {
3980 type Item = &'a mut [T];
3983 fn next(&mut self) -> Option<&'a mut [T]> {
3984 if self.v.len() < self.chunk_size {
3987 let tmp = mem::replace(&mut self.v, &mut []);
3988 let (head, tail) = tmp.split_at_mut(self.chunk_size);
3995 fn size_hint(&self) -> (usize, Option<usize>) {
3996 let n = self.v.len() / self.chunk_size;
4001 fn count(self) -> usize {
4006 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
4007 let (start, overflow) = n.overflowing_mul(self.chunk_size);
4008 if start >= self.v.len() || overflow {
4012 let tmp = mem::replace(&mut self.v, &mut []);
4013 let (_, snd) = tmp.split_at_mut(start);
4020 fn last(mut self) -> Option<Self::Item> {
4025 #[unstable(feature = "chunks_exact", issue = "47115")]
4026 impl<'a, T> DoubleEndedIterator for ChunksExactMut<'a, T> {
4028 fn next_back(&mut self) -> Option<&'a mut [T]> {
4029 if self.v.len() < self.chunk_size {
4032 let tmp = mem::replace(&mut self.v, &mut []);
4033 let tmp_len = tmp.len();
4034 let (head, tail) = tmp.split_at_mut(tmp_len - self.chunk_size);
4041 #[unstable(feature = "chunks_exact", issue = "47115")]
4042 impl<'a, T> ExactSizeIterator for ChunksExactMut<'a, T> {
4043 fn is_empty(&self) -> bool {
4048 #[unstable(feature = "trusted_len", issue = "37572")]
4049 unsafe impl<'a, T> TrustedLen for ChunksExactMut<'a, T> {}
4051 #[unstable(feature = "chunks_exact", issue = "47115")]
4052 impl<'a, T> FusedIterator for ChunksExactMut<'a, T> {}
4055 unsafe impl<'a, T> TrustedRandomAccess for ChunksExactMut<'a, T> {
4056 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
4057 let start = i * self.chunk_size;
4058 from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size)
4060 fn may_have_side_effect() -> bool { false }
4067 /// Forms a slice from a pointer and a length.
4069 /// The `len` argument is the number of **elements**, not the number of bytes.
4073 /// This function is unsafe as there is no guarantee that the given pointer is
4074 /// valid for `len` elements, nor whether the lifetime inferred is a suitable
4075 /// lifetime for the returned slice.
4077 /// `data` must be non-null and aligned, even for zero-length slices. One
4078 /// reason for this is that enum layout optimizations may rely on references
4079 /// (including slices of any length) being aligned and non-null to distinguish
4080 /// them from other data. You can obtain a pointer that is usable as `data`
4081 /// for zero-length slices using [`NonNull::dangling()`].
4085 /// The lifetime for the returned slice is inferred from its usage. To
4086 /// prevent accidental misuse, it's suggested to tie the lifetime to whichever
4087 /// source lifetime is safe in the context, such as by providing a helper
4088 /// function taking the lifetime of a host value for the slice, or by explicit
4096 /// // manifest a slice for a single element
4098 /// let ptr = &x as *const _;
4099 /// let slice = unsafe { slice::from_raw_parts(ptr, 1) };
4100 /// assert_eq!(slice[0], 42);
4103 /// [`NonNull::dangling()`]: ../../std/ptr/struct.NonNull.html#method.dangling
4105 #[stable(feature = "rust1", since = "1.0.0")]
4106 pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
4107 debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
4108 Repr { raw: FatPtr { data, len } }.rust
4111 /// Performs the same functionality as [`from_raw_parts`], except that a
4112 /// mutable slice is returned.
4114 /// This function is unsafe for the same reasons as [`from_raw_parts`], as well
4115 /// as not being able to provide a non-aliasing guarantee of the returned
4116 /// mutable slice. `data` must be non-null and aligned even for zero-length
4117 /// slices as with [`from_raw_parts`]. See the documentation of
4118 /// [`from_raw_parts`] for more details.
4120 /// [`from_raw_parts`]: ../../std/slice/fn.from_raw_parts.html
4122 #[stable(feature = "rust1", since = "1.0.0")]
4123 pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] {
4124 debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
4125 Repr { raw: FatPtr { data, len} }.rust_mut
4128 /// Converts a reference to T into a slice of length 1 (without copying).
4129 #[stable(feature = "from_ref", since = "1.28.0")]
4130 pub fn from_ref<T>(s: &T) -> &[T] {
4132 from_raw_parts(s, 1)
4136 /// Converts a reference to T into a slice of length 1 (without copying).
4137 #[stable(feature = "from_ref", since = "1.28.0")]
4138 pub fn from_mut<T>(s: &mut T) -> &mut [T] {
4140 from_raw_parts_mut(s, 1)
4144 // This function is public only because there is no other way to unit test heapsort.
4145 #[unstable(feature = "sort_internals", reason = "internal to sort module", issue = "0")]
4147 pub fn heapsort<T, F>(v: &mut [T], mut is_less: F)
4148 where F: FnMut(&T, &T) -> bool
4150 sort::heapsort(v, &mut is_less);
4154 // Comparison traits
4158 /// Calls implementation provided memcmp.
4160 /// Interprets the data as u8.
4162 /// Returns 0 for equal, < 0 for less than and > 0 for greater
4164 // FIXME(#32610): Return type should be c_int
4165 fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32;
4168 #[stable(feature = "rust1", since = "1.0.0")]
4169 impl<A, B> PartialEq<[B]> for [A] where A: PartialEq<B> {
4170 fn eq(&self, other: &[B]) -> bool {
4171 SlicePartialEq::equal(self, other)
4174 fn ne(&self, other: &[B]) -> bool {
4175 SlicePartialEq::not_equal(self, other)
4179 #[stable(feature = "rust1", since = "1.0.0")]
4180 impl<T: Eq> Eq for [T] {}
4182 /// Implements comparison of vectors lexicographically.
4183 #[stable(feature = "rust1", since = "1.0.0")]
4184 impl<T: Ord> Ord for [T] {
4185 fn cmp(&self, other: &[T]) -> Ordering {
4186 SliceOrd::compare(self, other)
4190 /// Implements comparison of vectors lexicographically.
4191 #[stable(feature = "rust1", since = "1.0.0")]
4192 impl<T: PartialOrd> PartialOrd for [T] {
4193 fn partial_cmp(&self, other: &[T]) -> Option<Ordering> {
4194 SlicePartialOrd::partial_compare(self, other)
4199 // intermediate trait for specialization of slice's PartialEq
4200 trait SlicePartialEq<B> {
4201 fn equal(&self, other: &[B]) -> bool;
4203 fn not_equal(&self, other: &[B]) -> bool { !self.equal(other) }
4206 // Generic slice equality
4207 impl<A, B> SlicePartialEq<B> for [A]
4208 where A: PartialEq<B>
4210 default fn equal(&self, other: &[B]) -> bool {
4211 if self.len() != other.len() {
4215 for i in 0..self.len() {
4216 if !self[i].eq(&other[i]) {
4225 // Use memcmp for bytewise equality when the types allow
4226 impl<A> SlicePartialEq<A> for [A]
4227 where A: PartialEq<A> + BytewiseEquality
4229 fn equal(&self, other: &[A]) -> bool {
4230 if self.len() != other.len() {
4233 if self.as_ptr() == other.as_ptr() {
4237 let size = mem::size_of_val(self);
4238 memcmp(self.as_ptr() as *const u8,
4239 other.as_ptr() as *const u8, size) == 0
4245 // intermediate trait for specialization of slice's PartialOrd
4246 trait SlicePartialOrd<B> {
4247 fn partial_compare(&self, other: &[B]) -> Option<Ordering>;
4250 impl<A> SlicePartialOrd<A> for [A]
4253 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
4254 let l = cmp::min(self.len(), other.len());
4256 // Slice to the loop iteration range to enable bound check
4257 // elimination in the compiler
4258 let lhs = &self[..l];
4259 let rhs = &other[..l];
4262 match lhs[i].partial_cmp(&rhs[i]) {
4263 Some(Ordering::Equal) => (),
4264 non_eq => return non_eq,
4268 self.len().partial_cmp(&other.len())
4272 impl<A> SlicePartialOrd<A> for [A]
4275 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
4276 Some(SliceOrd::compare(self, other))
4281 // intermediate trait for specialization of slice's Ord
4283 fn compare(&self, other: &[B]) -> Ordering;
4286 impl<A> SliceOrd<A> for [A]
4289 default fn compare(&self, other: &[A]) -> Ordering {
4290 let l = cmp::min(self.len(), other.len());
4292 // Slice to the loop iteration range to enable bound check
4293 // elimination in the compiler
4294 let lhs = &self[..l];
4295 let rhs = &other[..l];
4298 match lhs[i].cmp(&rhs[i]) {
4299 Ordering::Equal => (),
4300 non_eq => return non_eq,
4304 self.len().cmp(&other.len())
4308 // memcmp compares a sequence of unsigned bytes lexicographically.
4309 // this matches the order we want for [u8], but no others (not even [i8]).
4310 impl SliceOrd<u8> for [u8] {
4312 fn compare(&self, other: &[u8]) -> Ordering {
4313 let order = unsafe {
4314 memcmp(self.as_ptr(), other.as_ptr(),
4315 cmp::min(self.len(), other.len()))
4318 self.len().cmp(&other.len())
4319 } else if order < 0 {
4328 /// Trait implemented for types that can be compared for equality using
4329 /// their bytewise representation
4330 trait BytewiseEquality { }
4332 macro_rules! impl_marker_for {
4333 ($traitname:ident, $($ty:ty)*) => {
4335 impl $traitname for $ty { }
4340 impl_marker_for!(BytewiseEquality,
4341 u8 i8 u16 i16 u32 i32 u64 i64 usize isize char bool);
4344 unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {
4345 unsafe fn get_unchecked(&mut self, i: usize) -> &'a T {
4348 fn may_have_side_effect() -> bool { false }
4352 unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> {
4353 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut T {
4354 &mut *self.ptr.add(i)
4356 fn may_have_side_effect() -> bool { false }
4359 trait SliceContains: Sized {
4360 fn slice_contains(&self, x: &[Self]) -> bool;
4363 impl<T> SliceContains for T where T: PartialEq {
4364 default fn slice_contains(&self, x: &[Self]) -> bool {
4365 x.iter().any(|y| *y == *self)
4369 impl SliceContains for u8 {
4370 fn slice_contains(&self, x: &[Self]) -> bool {
4371 memchr::memchr(*self, x).is_some()
4375 impl SliceContains for i8 {
4376 fn slice_contains(&self, x: &[Self]) -> bool {
4377 let byte = *self as u8;
4378 let bytes: &[u8] = unsafe { from_raw_parts(x.as_ptr() as *const u8, x.len()) };
4379 memchr::memchr(byte, bytes).is_some()