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;
39 use ops::{FnMut, Try, self};
41 use option::Option::{None, Some};
43 use result::Result::{Ok, Err};
46 use marker::{Copy, Send, Sync, Sized, self};
47 use iter_private::TrustedRandomAccess;
49 #[unstable(feature = "slice_internals", issue = "0",
50 reason = "exposed from core to be reused in std; use the memchr crate")]
51 /// Pure rust memchr implementation, taken from rust-memchr
58 union Repr<'a, T: 'a> {
60 rust_mut: &'a mut [T],
77 /// Returns the number of elements in the slice.
82 /// let a = [1, 2, 3];
83 /// assert_eq!(a.len(), 3);
85 #[stable(feature = "rust1", since = "1.0.0")]
87 #[rustc_const_unstable(feature = "const_slice_len")]
88 pub const fn len(&self) -> usize {
90 Repr { rust: self }.raw.len
94 /// Returns `true` if the slice has a length of 0.
99 /// let a = [1, 2, 3];
100 /// assert!(!a.is_empty());
102 #[stable(feature = "rust1", since = "1.0.0")]
104 #[rustc_const_unstable(feature = "const_slice_len")]
105 pub const fn is_empty(&self) -> bool {
109 /// Returns the first element of the slice, or `None` if it is empty.
114 /// let v = [10, 40, 30];
115 /// assert_eq!(Some(&10), v.first());
117 /// let w: &[i32] = &[];
118 /// assert_eq!(None, w.first());
120 #[stable(feature = "rust1", since = "1.0.0")]
122 pub fn first(&self) -> Option<&T> {
126 /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
131 /// let x = &mut [0, 1, 2];
133 /// if let Some(first) = x.first_mut() {
136 /// assert_eq!(x, &[5, 1, 2]);
138 #[stable(feature = "rust1", since = "1.0.0")]
140 pub fn first_mut(&mut self) -> Option<&mut T> {
144 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
149 /// let x = &[0, 1, 2];
151 /// if let Some((first, elements)) = x.split_first() {
152 /// assert_eq!(first, &0);
153 /// assert_eq!(elements, &[1, 2]);
156 #[stable(feature = "slice_splits", since = "1.5.0")]
158 pub fn split_first(&self) -> Option<(&T, &[T])> {
159 if self.is_empty() { None } else { Some((&self[0], &self[1..])) }
162 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
167 /// let x = &mut [0, 1, 2];
169 /// if let Some((first, elements)) = x.split_first_mut() {
174 /// assert_eq!(x, &[3, 4, 5]);
176 #[stable(feature = "slice_splits", since = "1.5.0")]
178 pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
179 if self.is_empty() { None } else {
180 let split = self.split_at_mut(1);
181 Some((&mut split.0[0], split.1))
185 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
190 /// let x = &[0, 1, 2];
192 /// if let Some((last, elements)) = x.split_last() {
193 /// assert_eq!(last, &2);
194 /// assert_eq!(elements, &[0, 1]);
197 #[stable(feature = "slice_splits", since = "1.5.0")]
199 pub fn split_last(&self) -> Option<(&T, &[T])> {
200 let len = self.len();
201 if len == 0 { None } else { Some((&self[len - 1], &self[..(len - 1)])) }
204 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
209 /// let x = &mut [0, 1, 2];
211 /// if let Some((last, elements)) = x.split_last_mut() {
216 /// assert_eq!(x, &[4, 5, 3]);
218 #[stable(feature = "slice_splits", since = "1.5.0")]
220 pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
221 let len = self.len();
222 if len == 0 { None } else {
223 let split = self.split_at_mut(len - 1);
224 Some((&mut split.1[0], split.0))
229 /// Returns the last element of the slice, or `None` if it is empty.
234 /// let v = [10, 40, 30];
235 /// assert_eq!(Some(&30), v.last());
237 /// let w: &[i32] = &[];
238 /// assert_eq!(None, w.last());
240 #[stable(feature = "rust1", since = "1.0.0")]
242 pub fn last(&self) -> Option<&T> {
243 let last_idx = self.len().checked_sub(1)?;
247 /// Returns a mutable pointer to the last item in the slice.
252 /// let x = &mut [0, 1, 2];
254 /// if let Some(last) = x.last_mut() {
257 /// assert_eq!(x, &[0, 1, 10]);
259 #[stable(feature = "rust1", since = "1.0.0")]
261 pub fn last_mut(&mut self) -> Option<&mut T> {
262 let last_idx = self.len().checked_sub(1)?;
263 self.get_mut(last_idx)
266 /// Returns a reference to an element or subslice depending on the type of
269 /// - If given a position, returns a reference to the element at that
270 /// position or `None` if out of bounds.
271 /// - If given a range, returns the subslice corresponding to that range,
272 /// or `None` if out of bounds.
277 /// let v = [10, 40, 30];
278 /// assert_eq!(Some(&40), v.get(1));
279 /// assert_eq!(Some(&[10, 40][..]), v.get(0..2));
280 /// assert_eq!(None, v.get(3));
281 /// assert_eq!(None, v.get(0..4));
283 #[stable(feature = "rust1", since = "1.0.0")]
285 pub fn get<I>(&self, index: I) -> Option<&I::Output>
286 where I: SliceIndex<Self>
291 /// Returns a mutable reference to an element or subslice depending on the
292 /// type of index (see [`get`]) or `None` if the index is out of bounds.
294 /// [`get`]: #method.get
299 /// let x = &mut [0, 1, 2];
301 /// if let Some(elem) = x.get_mut(1) {
304 /// assert_eq!(x, &[0, 42, 2]);
306 #[stable(feature = "rust1", since = "1.0.0")]
308 pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output>
309 where I: SliceIndex<Self>
314 /// Returns a reference to an element or subslice, without doing bounds
317 /// This is generally not recommended, use with caution! For a safe
318 /// alternative see [`get`].
320 /// [`get`]: #method.get
325 /// let x = &[1, 2, 4];
328 /// assert_eq!(x.get_unchecked(1), &2);
331 #[stable(feature = "rust1", since = "1.0.0")]
333 pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output
334 where I: SliceIndex<Self>
336 index.get_unchecked(self)
339 /// Returns a mutable reference to an element or subslice, without doing
342 /// This is generally not recommended, use with caution! For a safe
343 /// alternative see [`get_mut`].
345 /// [`get_mut`]: #method.get_mut
350 /// let x = &mut [1, 2, 4];
353 /// let elem = x.get_unchecked_mut(1);
356 /// assert_eq!(x, &[1, 13, 4]);
358 #[stable(feature = "rust1", since = "1.0.0")]
360 pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
361 where I: SliceIndex<Self>
363 index.get_unchecked_mut(self)
366 /// Returns a raw pointer to the slice's buffer.
368 /// The caller must ensure that the slice outlives the pointer this
369 /// function returns, or else it will end up pointing to garbage.
371 /// Modifying the container referenced by this slice may cause its buffer
372 /// to be reallocated, which would also make any pointers to it invalid.
377 /// let x = &[1, 2, 4];
378 /// let x_ptr = x.as_ptr();
381 /// for i in 0..x.len() {
382 /// assert_eq!(x.get_unchecked(i), &*x_ptr.add(i));
386 #[stable(feature = "rust1", since = "1.0.0")]
388 #[rustc_const_unstable(feature = "const_slice_as_ptr")]
389 pub const fn as_ptr(&self) -> *const T {
390 self as *const [T] as *const T
393 /// Returns an unsafe mutable pointer to the slice's buffer.
395 /// The caller must ensure that the slice outlives the pointer this
396 /// function returns, or else it will end up pointing to garbage.
398 /// Modifying the container referenced by this slice may cause its buffer
399 /// to be reallocated, which would also make any pointers to it invalid.
404 /// let x = &mut [1, 2, 4];
405 /// let x_ptr = x.as_mut_ptr();
408 /// for i in 0..x.len() {
409 /// *x_ptr.add(i) += 2;
412 /// assert_eq!(x, &[3, 4, 6]);
414 #[stable(feature = "rust1", since = "1.0.0")]
416 pub fn as_mut_ptr(&mut self) -> *mut T {
417 self as *mut [T] as *mut T
420 /// Swaps two elements in the slice.
424 /// * a - The index of the first element
425 /// * b - The index of the second element
429 /// Panics if `a` or `b` are out of bounds.
434 /// let mut v = ["a", "b", "c", "d"];
436 /// assert!(v == ["a", "d", "c", "b"]);
438 #[stable(feature = "rust1", since = "1.0.0")]
440 pub fn swap(&mut self, a: usize, b: usize) {
442 // Can't take two mutable loans from one vector, so instead just cast
443 // them to their raw pointers to do the swap
444 let pa: *mut T = &mut self[a];
445 let pb: *mut T = &mut self[b];
450 /// Reverses the order of elements in the slice, in place.
455 /// let mut v = [1, 2, 3];
457 /// assert!(v == [3, 2, 1]);
459 #[stable(feature = "rust1", since = "1.0.0")]
461 pub fn reverse(&mut self) {
462 let mut i: usize = 0;
465 // For very small types, all the individual reads in the normal
466 // path perform poorly. We can do better, given efficient unaligned
467 // load/store, by loading a larger chunk and reversing a register.
469 // Ideally LLVM would do this for us, as it knows better than we do
470 // whether unaligned reads are efficient (since that changes between
471 // different ARM versions, for example) and what the best chunk size
472 // would be. Unfortunately, as of LLVM 4.0 (2017-05) it only unrolls
473 // the loop, so we need to do this ourselves. (Hypothesis: reverse
474 // is troublesome because the sides can be aligned differently --
475 // will be, when the length is odd -- so there's no way of emitting
476 // pre- and postludes to use fully-aligned SIMD in the middle.)
479 cfg!(any(target_arch = "x86", target_arch = "x86_64"));
481 if fast_unaligned && mem::size_of::<T>() == 1 {
482 // Use the llvm.bswap intrinsic to reverse u8s in a usize
483 let chunk = mem::size_of::<usize>();
484 while i + chunk - 1 < ln / 2 {
486 let pa: *mut T = self.get_unchecked_mut(i);
487 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
488 let va = ptr::read_unaligned(pa as *mut usize);
489 let vb = ptr::read_unaligned(pb as *mut usize);
490 ptr::write_unaligned(pa as *mut usize, vb.swap_bytes());
491 ptr::write_unaligned(pb as *mut usize, va.swap_bytes());
497 if fast_unaligned && mem::size_of::<T>() == 2 {
498 // Use rotate-by-16 to reverse u16s in a u32
499 let chunk = mem::size_of::<u32>() / 2;
500 while i + chunk - 1 < ln / 2 {
502 let pa: *mut T = self.get_unchecked_mut(i);
503 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
504 let va = ptr::read_unaligned(pa as *mut u32);
505 let vb = ptr::read_unaligned(pb as *mut u32);
506 ptr::write_unaligned(pa as *mut u32, vb.rotate_left(16));
507 ptr::write_unaligned(pb as *mut u32, va.rotate_left(16));
514 // Unsafe swap to avoid the bounds check in safe swap.
516 let pa: *mut T = self.get_unchecked_mut(i);
517 let pb: *mut T = self.get_unchecked_mut(ln - i - 1);
524 /// Returns an iterator over the slice.
529 /// let x = &[1, 2, 4];
530 /// let mut iterator = x.iter();
532 /// assert_eq!(iterator.next(), Some(&1));
533 /// assert_eq!(iterator.next(), Some(&2));
534 /// assert_eq!(iterator.next(), Some(&4));
535 /// assert_eq!(iterator.next(), None);
537 #[stable(feature = "rust1", since = "1.0.0")]
539 pub fn iter(&self) -> Iter<T> {
541 let ptr = self.as_ptr();
542 assume(!ptr.is_null());
544 let end = if mem::size_of::<T>() == 0 {
545 (ptr as *const u8).wrapping_add(self.len()) as *const T
553 _marker: marker::PhantomData
558 /// Returns an iterator that allows modifying each value.
563 /// let x = &mut [1, 2, 4];
564 /// for elem in x.iter_mut() {
567 /// assert_eq!(x, &[3, 4, 6]);
569 #[stable(feature = "rust1", since = "1.0.0")]
571 pub fn iter_mut(&mut self) -> IterMut<T> {
573 let ptr = self.as_mut_ptr();
574 assume(!ptr.is_null());
576 let end = if mem::size_of::<T>() == 0 {
577 (ptr as *mut u8).wrapping_add(self.len()) as *mut T
585 _marker: marker::PhantomData
590 /// Returns an iterator over all contiguous windows of length
591 /// `size`. The windows overlap. If the slice is shorter than
592 /// `size`, the iterator returns no values.
596 /// Panics if `size` is 0.
601 /// let slice = ['r', 'u', 's', 't'];
602 /// let mut iter = slice.windows(2);
603 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
604 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
605 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
606 /// assert!(iter.next().is_none());
609 /// If the slice is shorter than `size`:
612 /// let slice = ['f', 'o', 'o'];
613 /// let mut iter = slice.windows(4);
614 /// assert!(iter.next().is_none());
616 #[stable(feature = "rust1", since = "1.0.0")]
618 pub fn windows(&self, size: usize) -> Windows<T> {
620 Windows { v: self, size }
623 /// Returns an iterator over `chunk_size` elements of the slice at a
624 /// time. The chunks are slices and do not overlap. If `chunk_size` does
625 /// not divide the length of the slice, then the last chunk will
626 /// not have length `chunk_size`.
628 /// See [`chunks_exact`] for a variant of this iterator that returns chunks
629 /// of always exactly `chunk_size` elements.
633 /// Panics if `chunk_size` is 0.
638 /// let slice = ['l', 'o', 'r', 'e', 'm'];
639 /// let mut iter = slice.chunks(2);
640 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
641 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
642 /// assert_eq!(iter.next().unwrap(), &['m']);
643 /// assert!(iter.next().is_none());
646 /// [`chunks_exact`]: #method.chunks_exact
647 #[stable(feature = "rust1", since = "1.0.0")]
649 pub fn chunks(&self, chunk_size: usize) -> Chunks<T> {
650 assert!(chunk_size != 0);
651 Chunks { v: self, chunk_size }
654 /// Returns an iterator over `chunk_size` elements of the slice at a time.
655 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
656 /// not divide the length of the slice, then the last chunk will not
657 /// have length `chunk_size`.
659 /// See [`chunks_exact_mut`] for a variant of this iterator that returns chunks
660 /// of always exactly `chunk_size` elements.
664 /// Panics if `chunk_size` is 0.
669 /// let v = &mut [0, 0, 0, 0, 0];
670 /// let mut count = 1;
672 /// for chunk in v.chunks_mut(2) {
673 /// for elem in chunk.iter_mut() {
678 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
681 /// [`chunks_exact_mut`]: #method.chunks_exact_mut
682 #[stable(feature = "rust1", since = "1.0.0")]
684 pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T> {
685 assert!(chunk_size != 0);
686 ChunksMut { v: self, chunk_size }
689 /// Returns an iterator over `chunk_size` elements of the slice at a
690 /// time. The chunks are slices and do not overlap. If `chunk_size` does
691 /// not divide the length of the slice, then the last up to `chunk_size-1`
692 /// elements will be omitted and can be retrieved from the `remainder`
693 /// function of the iterator.
695 /// Due to each chunk having exactly `chunk_size` elements, the compiler
696 /// can often optimize the resulting code better than in the case of
701 /// Panics if `chunk_size` is 0.
706 /// #![feature(chunks_exact)]
708 /// let slice = ['l', 'o', 'r', 'e', 'm'];
709 /// let mut iter = slice.chunks_exact(2);
710 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
711 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
712 /// assert!(iter.next().is_none());
715 /// [`chunks`]: #method.chunks
716 #[unstable(feature = "chunks_exact", issue = "47115")]
718 pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<T> {
719 assert!(chunk_size != 0);
720 let rem = self.len() % chunk_size;
721 let len = self.len() - rem;
722 let (fst, snd) = self.split_at(len);
723 ChunksExact { v: fst, rem: snd, chunk_size }
726 /// Returns an iterator over `chunk_size` elements of the slice at a time.
727 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
728 /// not divide the length of the slice, then the last up to `chunk_size-1`
729 /// elements will be omitted and can be retrieved from the `into_remainder`
730 /// function of the iterator.
732 /// Due to each chunk having exactly `chunk_size` elements, the compiler
733 /// can often optimize the resulting code better than in the case of
738 /// Panics if `chunk_size` is 0.
743 /// #![feature(chunks_exact)]
745 /// let v = &mut [0, 0, 0, 0, 0];
746 /// let mut count = 1;
748 /// for chunk in v.chunks_exact_mut(2) {
749 /// for elem in chunk.iter_mut() {
754 /// assert_eq!(v, &[1, 1, 2, 2, 0]);
757 /// [`chunks_mut`]: #method.chunks_mut
758 #[unstable(feature = "chunks_exact", issue = "47115")]
760 pub fn chunks_exact_mut(&mut self, chunk_size: usize) -> ChunksExactMut<T> {
761 assert!(chunk_size != 0);
762 let rem = self.len() % chunk_size;
763 let len = self.len() - rem;
764 let (fst, snd) = self.split_at_mut(len);
765 ChunksExactMut { v: fst, rem: snd, chunk_size }
768 /// Divides one slice into two at an index.
770 /// The first will contain all indices from `[0, mid)` (excluding
771 /// the index `mid` itself) and the second will contain all
772 /// indices from `[mid, len)` (excluding the index `len` itself).
776 /// Panics if `mid > len`.
781 /// let v = [1, 2, 3, 4, 5, 6];
784 /// let (left, right) = v.split_at(0);
785 /// assert!(left == []);
786 /// assert!(right == [1, 2, 3, 4, 5, 6]);
790 /// let (left, right) = v.split_at(2);
791 /// assert!(left == [1, 2]);
792 /// assert!(right == [3, 4, 5, 6]);
796 /// let (left, right) = v.split_at(6);
797 /// assert!(left == [1, 2, 3, 4, 5, 6]);
798 /// assert!(right == []);
801 #[stable(feature = "rust1", since = "1.0.0")]
803 pub fn split_at(&self, mid: usize) -> (&[T], &[T]) {
804 (&self[..mid], &self[mid..])
807 /// Divides one mutable slice into two at an index.
809 /// The first will contain all indices from `[0, mid)` (excluding
810 /// the index `mid` itself) and the second will contain all
811 /// indices from `[mid, len)` (excluding the index `len` itself).
815 /// Panics if `mid > len`.
820 /// let mut v = [1, 0, 3, 0, 5, 6];
821 /// // scoped to restrict the lifetime of the borrows
823 /// let (left, right) = v.split_at_mut(2);
824 /// assert!(left == [1, 0]);
825 /// assert!(right == [3, 0, 5, 6]);
829 /// assert!(v == [1, 2, 3, 4, 5, 6]);
831 #[stable(feature = "rust1", since = "1.0.0")]
833 pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
834 let len = self.len();
835 let ptr = self.as_mut_ptr();
840 (from_raw_parts_mut(ptr, mid),
841 from_raw_parts_mut(ptr.add(mid), len - mid))
845 /// Returns an iterator over subslices separated by elements that match
846 /// `pred`. The matched element is not contained in the subslices.
851 /// let slice = [10, 40, 33, 20];
852 /// let mut iter = slice.split(|num| num % 3 == 0);
854 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
855 /// assert_eq!(iter.next().unwrap(), &[20]);
856 /// assert!(iter.next().is_none());
859 /// If the first element is matched, an empty slice will be the first item
860 /// returned by the iterator. Similarly, if the last element in the slice
861 /// is matched, an empty slice will be the last item returned by the
865 /// let slice = [10, 40, 33];
866 /// let mut iter = slice.split(|num| num % 3 == 0);
868 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
869 /// assert_eq!(iter.next().unwrap(), &[]);
870 /// assert!(iter.next().is_none());
873 /// If two matched elements are directly adjacent, an empty slice will be
874 /// present between them:
877 /// let slice = [10, 6, 33, 20];
878 /// let mut iter = slice.split(|num| num % 3 == 0);
880 /// assert_eq!(iter.next().unwrap(), &[10]);
881 /// assert_eq!(iter.next().unwrap(), &[]);
882 /// assert_eq!(iter.next().unwrap(), &[20]);
883 /// assert!(iter.next().is_none());
885 #[stable(feature = "rust1", since = "1.0.0")]
887 pub fn split<F>(&self, pred: F) -> Split<T, F>
888 where F: FnMut(&T) -> bool
897 /// Returns an iterator over mutable subslices separated by elements that
898 /// match `pred`. The matched element is not contained in the subslices.
903 /// let mut v = [10, 40, 30, 20, 60, 50];
905 /// for group in v.split_mut(|num| *num % 3 == 0) {
908 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
910 #[stable(feature = "rust1", since = "1.0.0")]
912 pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<T, F>
913 where F: FnMut(&T) -> bool
915 SplitMut { v: self, pred, finished: false }
918 /// Returns an iterator over subslices separated by elements that match
919 /// `pred`, starting at the end of the slice and working backwards.
920 /// The matched element is not contained in the subslices.
925 /// let slice = [11, 22, 33, 0, 44, 55];
926 /// let mut iter = slice.rsplit(|num| *num == 0);
928 /// assert_eq!(iter.next().unwrap(), &[44, 55]);
929 /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
930 /// assert_eq!(iter.next(), None);
933 /// As with `split()`, if the first or last element is matched, an empty
934 /// slice will be the first (or last) item returned by the iterator.
937 /// let v = &[0, 1, 1, 2, 3, 5, 8];
938 /// let mut it = v.rsplit(|n| *n % 2 == 0);
939 /// assert_eq!(it.next().unwrap(), &[]);
940 /// assert_eq!(it.next().unwrap(), &[3, 5]);
941 /// assert_eq!(it.next().unwrap(), &[1, 1]);
942 /// assert_eq!(it.next().unwrap(), &[]);
943 /// assert_eq!(it.next(), None);
945 #[stable(feature = "slice_rsplit", since = "1.27.0")]
947 pub fn rsplit<F>(&self, pred: F) -> RSplit<T, F>
948 where F: FnMut(&T) -> bool
950 RSplit { inner: self.split(pred) }
953 /// Returns an iterator over mutable subslices separated by elements that
954 /// match `pred`, starting at the end of the slice and working
955 /// backwards. The matched element is not contained in the subslices.
960 /// let mut v = [100, 400, 300, 200, 600, 500];
962 /// let mut count = 0;
963 /// for group in v.rsplit_mut(|num| *num % 3 == 0) {
965 /// group[0] = count;
967 /// assert_eq!(v, [3, 400, 300, 2, 600, 1]);
970 #[stable(feature = "slice_rsplit", since = "1.27.0")]
972 pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<T, F>
973 where F: FnMut(&T) -> bool
975 RSplitMut { inner: self.split_mut(pred) }
978 /// Returns an iterator over subslices separated by elements that match
979 /// `pred`, limited to returning at most `n` items. The matched element is
980 /// not contained in the subslices.
982 /// The last element returned, if any, will contain the remainder of the
987 /// Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`,
991 /// let v = [10, 40, 30, 20, 60, 50];
993 /// for group in v.splitn(2, |num| *num % 3 == 0) {
994 /// println!("{:?}", group);
997 #[stable(feature = "rust1", since = "1.0.0")]
999 pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F>
1000 where F: FnMut(&T) -> bool
1003 inner: GenericSplitN {
1004 iter: self.split(pred),
1010 /// Returns an iterator over subslices separated by elements that match
1011 /// `pred`, limited to returning at most `n` items. The matched element is
1012 /// not contained in the subslices.
1014 /// The last element returned, if any, will contain the remainder of the
1020 /// let mut v = [10, 40, 30, 20, 60, 50];
1022 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
1025 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
1027 #[stable(feature = "rust1", since = "1.0.0")]
1029 pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<T, F>
1030 where F: FnMut(&T) -> bool
1033 inner: GenericSplitN {
1034 iter: self.split_mut(pred),
1040 /// Returns an iterator over subslices separated by elements that match
1041 /// `pred` limited to returning at most `n` items. This starts at the end of
1042 /// the slice and works backwards. The matched element is not contained in
1045 /// The last element returned, if any, will contain the remainder of the
1050 /// Print the slice split once, starting from the end, by numbers divisible
1051 /// by 3 (i.e. `[50]`, `[10, 40, 30, 20]`):
1054 /// let v = [10, 40, 30, 20, 60, 50];
1056 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
1057 /// println!("{:?}", group);
1060 #[stable(feature = "rust1", since = "1.0.0")]
1062 pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F>
1063 where F: FnMut(&T) -> bool
1066 inner: GenericSplitN {
1067 iter: self.rsplit(pred),
1073 /// Returns an iterator over subslices separated by elements that match
1074 /// `pred` limited to returning at most `n` items. This starts at the end of
1075 /// the slice and works backwards. The matched element is not contained in
1078 /// The last element returned, if any, will contain the remainder of the
1084 /// let mut s = [10, 40, 30, 20, 60, 50];
1086 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
1089 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
1091 #[stable(feature = "rust1", since = "1.0.0")]
1093 pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<T, F>
1094 where F: FnMut(&T) -> bool
1097 inner: GenericSplitN {
1098 iter: self.rsplit_mut(pred),
1104 /// Returns `true` if the slice contains an element with the given value.
1109 /// let v = [10, 40, 30];
1110 /// assert!(v.contains(&30));
1111 /// assert!(!v.contains(&50));
1113 #[stable(feature = "rust1", since = "1.0.0")]
1114 pub fn contains(&self, x: &T) -> bool
1117 x.slice_contains(self)
1120 /// Returns `true` if `needle` is a prefix of the slice.
1125 /// let v = [10, 40, 30];
1126 /// assert!(v.starts_with(&[10]));
1127 /// assert!(v.starts_with(&[10, 40]));
1128 /// assert!(!v.starts_with(&[50]));
1129 /// assert!(!v.starts_with(&[10, 50]));
1132 /// Always returns `true` if `needle` is an empty slice:
1135 /// let v = &[10, 40, 30];
1136 /// assert!(v.starts_with(&[]));
1137 /// let v: &[u8] = &[];
1138 /// assert!(v.starts_with(&[]));
1140 #[stable(feature = "rust1", since = "1.0.0")]
1141 pub fn starts_with(&self, needle: &[T]) -> bool
1144 let n = needle.len();
1145 self.len() >= n && needle == &self[..n]
1148 /// Returns `true` if `needle` is a suffix of the slice.
1153 /// let v = [10, 40, 30];
1154 /// assert!(v.ends_with(&[30]));
1155 /// assert!(v.ends_with(&[40, 30]));
1156 /// assert!(!v.ends_with(&[50]));
1157 /// assert!(!v.ends_with(&[50, 30]));
1160 /// Always returns `true` if `needle` is an empty slice:
1163 /// let v = &[10, 40, 30];
1164 /// assert!(v.ends_with(&[]));
1165 /// let v: &[u8] = &[];
1166 /// assert!(v.ends_with(&[]));
1168 #[stable(feature = "rust1", since = "1.0.0")]
1169 pub fn ends_with(&self, needle: &[T]) -> bool
1172 let (m, n) = (self.len(), needle.len());
1173 m >= n && needle == &self[m-n..]
1176 /// Binary searches this sorted slice for a given element.
1178 /// If the value is found then [`Result::Ok`] is returned, containing the
1179 /// index of the matching element. If there are multiple matches, then any
1180 /// one of the matches could be returned. If the value is not found then
1181 /// [`Result::Err`] is returned, containing the index where a matching
1182 /// element could be inserted while maintaining sorted order.
1186 /// Looks up a series of four elements. The first is found, with a
1187 /// uniquely determined position; the second and third are not
1188 /// found; the fourth could match any position in `[1, 4]`.
1191 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1193 /// assert_eq!(s.binary_search(&13), Ok(9));
1194 /// assert_eq!(s.binary_search(&4), Err(7));
1195 /// assert_eq!(s.binary_search(&100), Err(13));
1196 /// let r = s.binary_search(&1);
1197 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1199 #[stable(feature = "rust1", since = "1.0.0")]
1200 pub fn binary_search(&self, x: &T) -> Result<usize, usize>
1203 self.binary_search_by(|p| p.cmp(x))
1206 /// Binary searches this sorted slice with a comparator function.
1208 /// The comparator function should implement an order consistent
1209 /// with the sort order of the underlying slice, returning an
1210 /// order code that indicates whether its argument is `Less`,
1211 /// `Equal` or `Greater` the desired target.
1213 /// If the value is found then [`Result::Ok`] is returned, containing the
1214 /// index of the matching element. If there are multiple matches, then any
1215 /// one of the matches could be returned. If the value is not found then
1216 /// [`Result::Err`] is returned, containing the index where a matching
1217 /// element could be inserted while maintaining sorted order.
1221 /// Looks up a series of four elements. The first is found, with a
1222 /// uniquely determined position; the second and third are not
1223 /// found; the fourth could match any position in `[1, 4]`.
1226 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1229 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
1231 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
1233 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
1235 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
1236 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1238 #[stable(feature = "rust1", since = "1.0.0")]
1240 pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
1241 where F: FnMut(&'a T) -> Ordering
1244 let mut size = s.len();
1248 let mut base = 0usize;
1250 let half = size / 2;
1251 let mid = base + half;
1252 // mid is always in [0, size), that means mid is >= 0 and < size.
1253 // mid >= 0: by definition
1254 // mid < size: mid = size / 2 + size / 4 + size / 8 ...
1255 let cmp = f(unsafe { s.get_unchecked(mid) });
1256 base = if cmp == Greater { base } else { mid };
1259 // base is always in [0, size) because base <= mid.
1260 let cmp = f(unsafe { s.get_unchecked(base) });
1261 if cmp == Equal { Ok(base) } else { Err(base + (cmp == Less) as usize) }
1265 /// Binary searches this sorted slice with a key extraction function.
1267 /// Assumes that the slice is sorted by the key, for instance with
1268 /// [`sort_by_key`] using the same key extraction function.
1270 /// If the value is found then [`Result::Ok`] is returned, containing the
1271 /// index of the matching element. If there are multiple matches, then any
1272 /// one of the matches could be returned. If the value is not found then
1273 /// [`Result::Err`] is returned, containing the index where a matching
1274 /// element could be inserted while maintaining sorted order.
1276 /// [`sort_by_key`]: #method.sort_by_key
1280 /// Looks up a series of four elements in a slice of pairs sorted by
1281 /// their second elements. The first is found, with a uniquely
1282 /// determined position; the second and third are not found; the
1283 /// fourth could match any position in `[1, 4]`.
1286 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
1287 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
1288 /// (1, 21), (2, 34), (4, 55)];
1290 /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9));
1291 /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7));
1292 /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
1293 /// let r = s.binary_search_by_key(&1, |&(a,b)| b);
1294 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1296 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
1298 pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
1299 where F: FnMut(&'a T) -> B,
1302 self.binary_search_by(|k| f(k).cmp(b))
1305 /// Sorts the slice, but may not preserve the order of equal elements.
1307 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1308 /// and `O(n log n)` worst-case.
1310 /// # Current implementation
1312 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1313 /// which combines the fast average case of randomized quicksort with the fast worst case of
1314 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1315 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1316 /// deterministic behavior.
1318 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1319 /// slice consists of several concatenated sorted sequences.
1324 /// let mut v = [-5, 4, 1, -3, 2];
1326 /// v.sort_unstable();
1327 /// assert!(v == [-5, -3, 1, 2, 4]);
1330 /// [pdqsort]: https://github.com/orlp/pdqsort
1331 #[stable(feature = "sort_unstable", since = "1.20.0")]
1333 pub fn sort_unstable(&mut self)
1336 sort::quicksort(self, |a, b| a.lt(b));
1339 /// Sorts the slice with a comparator function, but may not preserve the order of equal
1342 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1343 /// and `O(n log n)` worst-case.
1345 /// # Current implementation
1347 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1348 /// which combines the fast average case of randomized quicksort with the fast worst case of
1349 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1350 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1351 /// deterministic behavior.
1353 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1354 /// slice consists of several concatenated sorted sequences.
1359 /// let mut v = [5, 4, 1, 3, 2];
1360 /// v.sort_unstable_by(|a, b| a.cmp(b));
1361 /// assert!(v == [1, 2, 3, 4, 5]);
1363 /// // reverse sorting
1364 /// v.sort_unstable_by(|a, b| b.cmp(a));
1365 /// assert!(v == [5, 4, 3, 2, 1]);
1368 /// [pdqsort]: https://github.com/orlp/pdqsort
1369 #[stable(feature = "sort_unstable", since = "1.20.0")]
1371 pub fn sort_unstable_by<F>(&mut self, mut compare: F)
1372 where F: FnMut(&T, &T) -> Ordering
1374 sort::quicksort(self, |a, b| compare(a, b) == Ordering::Less);
1377 /// Sorts the slice with a key extraction function, but may not preserve the order of equal
1380 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1381 /// and `O(m n log(m n))` worst-case, where the key function is `O(m)`.
1383 /// # Current implementation
1385 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1386 /// which combines the fast average case of randomized quicksort with the fast worst case of
1387 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1388 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1389 /// deterministic behavior.
1394 /// let mut v = [-5i32, 4, 1, -3, 2];
1396 /// v.sort_unstable_by_key(|k| k.abs());
1397 /// assert!(v == [1, 2, -3, 4, -5]);
1400 /// [pdqsort]: https://github.com/orlp/pdqsort
1401 #[stable(feature = "sort_unstable", since = "1.20.0")]
1403 pub fn sort_unstable_by_key<K, F>(&mut self, mut f: F)
1404 where F: FnMut(&T) -> K, K: Ord
1406 sort::quicksort(self, |a, b| f(a).lt(&f(b)));
1409 /// Moves all consecutive repeated elements to the end of the slice according to the
1410 /// [`PartialEq`] trait implementation.
1412 /// Returns two slices. The first contains no consecutive repeated elements.
1413 /// The second contains all the duplicates in no specified order.
1415 /// If the slice is sorted, the first returned slice contains no duplicates.
1420 /// #![feature(slice_partition_dedup)]
1422 /// let mut slice = [1, 2, 2, 3, 3, 2, 1, 1];
1424 /// let (dedup, duplicates) = slice.partition_dedup();
1426 /// assert_eq!(dedup, [1, 2, 3, 2, 1]);
1427 /// assert_eq!(duplicates, [2, 3, 1]);
1429 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1431 pub fn partition_dedup(&mut self) -> (&mut [T], &mut [T])
1434 self.partition_dedup_by(|a, b| a == b)
1437 /// Moves all but the first of consecutive elements to the end of the slice satisfying
1438 /// a given equality relation.
1440 /// Returns two slices. The first contains no consecutive repeated elements.
1441 /// The second contains all the duplicates in no specified order.
1443 /// The `same_bucket` function is passed references to two elements from the slice and
1444 /// must determine if the elements compare equal. The elements are passed in opposite order
1445 /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is moved
1446 /// at the end of the slice.
1448 /// If the slice is sorted, the first returned slice contains no duplicates.
1453 /// #![feature(slice_partition_dedup)]
1455 /// let mut slice = ["foo", "Foo", "BAZ", "Bar", "bar", "baz", "BAZ"];
1457 /// let (dedup, duplicates) = slice.partition_dedup_by(|a, b| a.eq_ignore_ascii_case(b));
1459 /// assert_eq!(dedup, ["foo", "BAZ", "Bar", "baz"]);
1460 /// assert_eq!(duplicates, ["bar", "Foo", "BAZ"]);
1462 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1464 pub fn partition_dedup_by<F>(&mut self, mut same_bucket: F) -> (&mut [T], &mut [T])
1465 where F: FnMut(&mut T, &mut T) -> bool
1467 // Although we have a mutable reference to `self`, we cannot make
1468 // *arbitrary* changes. The `same_bucket` calls could panic, so we
1469 // must ensure that the slice is in a valid state at all times.
1471 // The way that we handle this is by using swaps; we iterate
1472 // over all the elements, swapping as we go so that at the end
1473 // the elements we wish to keep are in the front, and those we
1474 // wish to reject are at the back. We can then split the slice.
1475 // This operation is still O(n).
1477 // Example: We start in this state, where `r` represents "next
1478 // read" and `w` represents "next_write`.
1481 // +---+---+---+---+---+---+
1482 // | 0 | 1 | 1 | 2 | 3 | 3 |
1483 // +---+---+---+---+---+---+
1486 // Comparing self[r] against self[w-1], this is not a duplicate, so
1487 // we swap self[r] and self[w] (no effect as r==w) and then increment both
1488 // r and w, leaving us with:
1491 // +---+---+---+---+---+---+
1492 // | 0 | 1 | 1 | 2 | 3 | 3 |
1493 // +---+---+---+---+---+---+
1496 // Comparing self[r] against self[w-1], this value is a duplicate,
1497 // so we increment `r` but leave everything else unchanged:
1500 // +---+---+---+---+---+---+
1501 // | 0 | 1 | 1 | 2 | 3 | 3 |
1502 // +---+---+---+---+---+---+
1505 // Comparing self[r] against self[w-1], this is not a duplicate,
1506 // so swap self[r] and self[w] and advance r and w:
1509 // +---+---+---+---+---+---+
1510 // | 0 | 1 | 2 | 1 | 3 | 3 |
1511 // +---+---+---+---+---+---+
1514 // Not a duplicate, repeat:
1517 // +---+---+---+---+---+---+
1518 // | 0 | 1 | 2 | 3 | 1 | 3 |
1519 // +---+---+---+---+---+---+
1522 // Duplicate, advance r. End of slice. Split at w.
1524 let len = self.len();
1526 return (self, &mut [])
1529 let ptr = self.as_mut_ptr();
1530 let mut next_read: usize = 1;
1531 let mut next_write: usize = 1;
1534 // Avoid bounds checks by using raw pointers.
1535 while next_read < len {
1536 let ptr_read = ptr.add(next_read);
1537 let prev_ptr_write = ptr.add(next_write - 1);
1538 if !same_bucket(&mut *ptr_read, &mut *prev_ptr_write) {
1539 if next_read != next_write {
1540 let ptr_write = prev_ptr_write.offset(1);
1541 mem::swap(&mut *ptr_read, &mut *ptr_write);
1549 self.split_at_mut(next_write)
1552 /// Moves all but the first of consecutive elements to the end of the slice that resolve
1553 /// to the same key.
1555 /// Returns two slices. The first contains no consecutive repeated elements.
1556 /// The second contains all the duplicates in no specified order.
1558 /// If the slice is sorted, the first returned slice contains no duplicates.
1563 /// #![feature(slice_partition_dedup)]
1565 /// let mut slice = [10, 20, 21, 30, 30, 20, 11, 13];
1567 /// let (dedup, duplicates) = slice.partition_dedup_by_key(|i| *i / 10);
1569 /// assert_eq!(dedup, [10, 20, 30, 20, 11]);
1570 /// assert_eq!(duplicates, [21, 30, 13]);
1572 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1574 pub fn partition_dedup_by_key<K, F>(&mut self, mut key: F) -> (&mut [T], &mut [T])
1575 where F: FnMut(&mut T) -> K,
1578 self.partition_dedup_by(|a, b| key(a) == key(b))
1581 /// Rotates the slice in-place such that the first `mid` elements of the
1582 /// slice move to the end while the last `self.len() - mid` elements move to
1583 /// the front. After calling `rotate_left`, the element previously at index
1584 /// `mid` will become the first element in the slice.
1588 /// This function will panic if `mid` is greater than the length of the
1589 /// slice. Note that `mid == self.len()` does _not_ panic and is a no-op
1594 /// Takes linear (in `self.len()`) time.
1599 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1600 /// a.rotate_left(2);
1601 /// assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
1604 /// Rotating a subslice:
1607 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1608 /// a[1..5].rotate_left(1);
1609 /// assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']);
1611 #[stable(feature = "slice_rotate", since = "1.26.0")]
1612 pub fn rotate_left(&mut self, mid: usize) {
1613 assert!(mid <= self.len());
1614 let k = self.len() - mid;
1617 let p = self.as_mut_ptr();
1618 rotate::ptr_rotate(mid, p.add(mid), k);
1622 /// Rotates the slice in-place such that the first `self.len() - k`
1623 /// elements of the slice move to the end while the last `k` elements move
1624 /// to the front. After calling `rotate_right`, the element previously at
1625 /// index `self.len() - k` will become the first element in the slice.
1629 /// This function will panic if `k` is greater than the length of the
1630 /// slice. Note that `k == self.len()` does _not_ panic and is a no-op
1635 /// Takes linear (in `self.len()`) time.
1640 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1641 /// a.rotate_right(2);
1642 /// assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);
1645 /// Rotate a subslice:
1648 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1649 /// a[1..5].rotate_right(1);
1650 /// assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']);
1652 #[stable(feature = "slice_rotate", since = "1.26.0")]
1653 pub fn rotate_right(&mut self, k: usize) {
1654 assert!(k <= self.len());
1655 let mid = self.len() - k;
1658 let p = self.as_mut_ptr();
1659 rotate::ptr_rotate(mid, p.add(mid), k);
1663 /// Copies the elements from `src` into `self`.
1665 /// The length of `src` must be the same as `self`.
1667 /// If `src` implements `Copy`, it can be more performant to use
1668 /// [`copy_from_slice`].
1672 /// This function will panic if the two slices have different lengths.
1676 /// Cloning two elements from a slice into another:
1679 /// let src = [1, 2, 3, 4];
1680 /// let mut dst = [0, 0];
1682 /// // Because the slices have to be the same length,
1683 /// // we slice the source slice from four elements
1684 /// // to two. It will panic if we don't do this.
1685 /// dst.clone_from_slice(&src[2..]);
1687 /// assert_eq!(src, [1, 2, 3, 4]);
1688 /// assert_eq!(dst, [3, 4]);
1691 /// Rust enforces that there can only be one mutable reference with no
1692 /// immutable references to a particular piece of data in a particular
1693 /// scope. Because of this, attempting to use `clone_from_slice` on a
1694 /// single slice will result in a compile failure:
1697 /// let mut slice = [1, 2, 3, 4, 5];
1699 /// slice[..2].clone_from_slice(&slice[3..]); // compile fail!
1702 /// To work around this, we can use [`split_at_mut`] to create two distinct
1703 /// sub-slices from a slice:
1706 /// let mut slice = [1, 2, 3, 4, 5];
1709 /// let (left, right) = slice.split_at_mut(2);
1710 /// left.clone_from_slice(&right[1..]);
1713 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
1716 /// [`copy_from_slice`]: #method.copy_from_slice
1717 /// [`split_at_mut`]: #method.split_at_mut
1718 #[stable(feature = "clone_from_slice", since = "1.7.0")]
1719 pub fn clone_from_slice(&mut self, src: &[T]) where T: Clone {
1720 assert!(self.len() == src.len(),
1721 "destination and source slices have different lengths");
1722 // NOTE: We need to explicitly slice them to the same length
1723 // for bounds checking to be elided, and the optimizer will
1724 // generate memcpy for simple cases (for example T = u8).
1725 let len = self.len();
1726 let src = &src[..len];
1728 self[i].clone_from(&src[i]);
1733 /// Copies all elements from `src` into `self`, using a memcpy.
1735 /// The length of `src` must be the same as `self`.
1737 /// If `src` does not implement `Copy`, use [`clone_from_slice`].
1741 /// This function will panic if the two slices have different lengths.
1745 /// Copying two elements from a slice into another:
1748 /// let src = [1, 2, 3, 4];
1749 /// let mut dst = [0, 0];
1751 /// // Because the slices have to be the same length,
1752 /// // we slice the source slice from four elements
1753 /// // to two. It will panic if we don't do this.
1754 /// dst.copy_from_slice(&src[2..]);
1756 /// assert_eq!(src, [1, 2, 3, 4]);
1757 /// assert_eq!(dst, [3, 4]);
1760 /// Rust enforces that there can only be one mutable reference with no
1761 /// immutable references to a particular piece of data in a particular
1762 /// scope. Because of this, attempting to use `copy_from_slice` on a
1763 /// single slice will result in a compile failure:
1766 /// let mut slice = [1, 2, 3, 4, 5];
1768 /// slice[..2].copy_from_slice(&slice[3..]); // compile fail!
1771 /// To work around this, we can use [`split_at_mut`] to create two distinct
1772 /// sub-slices from a slice:
1775 /// let mut slice = [1, 2, 3, 4, 5];
1778 /// let (left, right) = slice.split_at_mut(2);
1779 /// left.copy_from_slice(&right[1..]);
1782 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
1785 /// [`clone_from_slice`]: #method.clone_from_slice
1786 /// [`split_at_mut`]: #method.split_at_mut
1787 #[stable(feature = "copy_from_slice", since = "1.9.0")]
1788 pub fn copy_from_slice(&mut self, src: &[T]) where T: Copy {
1789 assert_eq!(self.len(), src.len(),
1790 "destination and source slices have different lengths");
1792 ptr::copy_nonoverlapping(
1793 src.as_ptr(), self.as_mut_ptr(), self.len());
1797 /// Copies elements from one part of the slice to another part of itself,
1798 /// using a memmove.
1800 /// `src` is the range within `self` to copy from. `dest` is the starting
1801 /// index of the range within `self` to copy to, which will have the same
1802 /// length as `src`. The two ranges may overlap. The ends of the two ranges
1803 /// must be less than or equal to `self.len()`.
1807 /// This function will panic if either range exceeds the end of the slice,
1808 /// or if the end of `src` is before the start.
1812 /// Copying four bytes within a slice:
1815 /// # #![feature(copy_within)]
1816 /// let mut bytes = *b"Hello, World!";
1818 /// bytes.copy_within(1..5, 8);
1820 /// assert_eq!(&bytes, b"Hello, Wello!");
1822 #[unstable(feature = "copy_within", issue = "54236")]
1823 pub fn copy_within<R: ops::RangeBounds<usize>>(&mut self, src: R, dest: usize)
1827 let src_start = match src.start_bound() {
1828 ops::Bound::Included(&n) => n,
1829 ops::Bound::Excluded(&n) => n
1831 .unwrap_or_else(|| slice_index_overflow_fail()),
1832 ops::Bound::Unbounded => 0,
1834 let src_end = match src.end_bound() {
1835 ops::Bound::Included(&n) => n
1837 .unwrap_or_else(|| slice_index_overflow_fail()),
1838 ops::Bound::Excluded(&n) => n,
1839 ops::Bound::Unbounded => self.len(),
1841 assert!(src_start <= src_end, "src end is before src start");
1842 assert!(src_end <= self.len(), "src is out of bounds");
1843 let count = src_end - src_start;
1844 assert!(dest <= self.len() - count, "dest is out of bounds");
1847 self.get_unchecked(src_start),
1848 self.get_unchecked_mut(dest),
1854 /// Swaps all elements in `self` with those in `other`.
1856 /// The length of `other` must be the same as `self`.
1860 /// This function will panic if the two slices have different lengths.
1864 /// Swapping two elements across slices:
1867 /// let mut slice1 = [0, 0];
1868 /// let mut slice2 = [1, 2, 3, 4];
1870 /// slice1.swap_with_slice(&mut slice2[2..]);
1872 /// assert_eq!(slice1, [3, 4]);
1873 /// assert_eq!(slice2, [1, 2, 0, 0]);
1876 /// Rust enforces that there can only be one mutable reference to a
1877 /// particular piece of data in a particular scope. Because of this,
1878 /// attempting to use `swap_with_slice` on a single slice will result in
1879 /// a compile failure:
1882 /// let mut slice = [1, 2, 3, 4, 5];
1883 /// slice[..2].swap_with_slice(&mut slice[3..]); // compile fail!
1886 /// To work around this, we can use [`split_at_mut`] to create two distinct
1887 /// mutable sub-slices from a slice:
1890 /// let mut slice = [1, 2, 3, 4, 5];
1893 /// let (left, right) = slice.split_at_mut(2);
1894 /// left.swap_with_slice(&mut right[1..]);
1897 /// assert_eq!(slice, [4, 5, 3, 1, 2]);
1900 /// [`split_at_mut`]: #method.split_at_mut
1901 #[stable(feature = "swap_with_slice", since = "1.27.0")]
1902 pub fn swap_with_slice(&mut self, other: &mut [T]) {
1903 assert!(self.len() == other.len(),
1904 "destination and source slices have different lengths");
1906 ptr::swap_nonoverlapping(
1907 self.as_mut_ptr(), other.as_mut_ptr(), self.len());
1911 /// Function to calculate lengths of the middle and trailing slice for `align_to{,_mut}`.
1912 fn align_to_offsets<U>(&self) -> (usize, usize) {
1913 // What we gonna do about `rest` is figure out what multiple of `U`s we can put in a
1914 // lowest number of `T`s. And how many `T`s we need for each such "multiple".
1916 // Consider for example T=u8 U=u16. Then we can put 1 U in 2 Ts. Simple. Now, consider
1917 // for example a case where size_of::<T> = 16, size_of::<U> = 24. We can put 2 Us in
1918 // place of every 3 Ts in the `rest` slice. A bit more complicated.
1920 // Formula to calculate this is:
1922 // Us = lcm(size_of::<T>, size_of::<U>) / size_of::<U>
1923 // Ts = lcm(size_of::<T>, size_of::<U>) / size_of::<T>
1925 // Expanded and simplified:
1927 // Us = size_of::<T> / gcd(size_of::<T>, size_of::<U>)
1928 // Ts = size_of::<U> / gcd(size_of::<T>, size_of::<U>)
1930 // Luckily since all this is constant-evaluated... performance here matters not!
1932 fn gcd(a: usize, b: usize) -> usize {
1933 // iterative stein’s algorithm
1934 // We should still make this `const fn` (and revert to recursive algorithm if we do)
1935 // because relying on llvm to consteval all this is… well, it makes me
1936 let (ctz_a, mut ctz_b) = unsafe {
1937 if a == 0 { return b; }
1938 if b == 0 { return a; }
1939 (::intrinsics::cttz_nonzero(a), ::intrinsics::cttz_nonzero(b))
1941 let k = ctz_a.min(ctz_b);
1942 let mut a = a >> ctz_a;
1945 // remove all factors of 2 from b
1948 ::mem::swap(&mut a, &mut b);
1955 ctz_b = ::intrinsics::cttz_nonzero(b);
1960 let gcd: usize = gcd(::mem::size_of::<T>(), ::mem::size_of::<U>());
1961 let ts: usize = ::mem::size_of::<U>() / gcd;
1962 let us: usize = ::mem::size_of::<T>() / gcd;
1964 // Armed with this knowledge, we can find how many `U`s we can fit!
1965 let us_len = self.len() / ts * us;
1966 // And how many `T`s will be in the trailing slice!
1967 let ts_len = self.len() % ts;
1971 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
1974 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
1975 /// slice of a new type, and the suffix slice. The method does a best effort to make the
1976 /// middle slice the greatest length possible for a given type and input slice, but only
1977 /// your algorithm's performance should depend on that, not its correctness.
1979 /// This method has no purpose when either input element `T` or output element `U` are
1980 /// zero-sized and will return the original slice without splitting anything.
1984 /// This method is essentially a `transmute` with respect to the elements in the returned
1985 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
1993 /// let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
1994 /// let (prefix, shorts, suffix) = bytes.align_to::<u16>();
1995 /// // less_efficient_algorithm_for_bytes(prefix);
1996 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
1997 /// // less_efficient_algorithm_for_bytes(suffix);
2000 #[stable(feature = "slice_align_to", since = "1.30.0")]
2001 pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T]) {
2002 // Note that most of this function will be constant-evaluated,
2003 if ::mem::size_of::<U>() == 0 || ::mem::size_of::<T>() == 0 {
2004 // handle ZSTs specially, which is – don't handle them at all.
2005 return (self, &[], &[]);
2008 // First, find at what point do we split between the first and 2nd slice. Easy with
2009 // ptr.align_offset.
2010 let ptr = self.as_ptr();
2011 let offset = ::ptr::align_offset(ptr, ::mem::align_of::<U>());
2012 if offset > self.len() {
2015 let (left, rest) = self.split_at(offset);
2016 // now `rest` is definitely aligned, so `from_raw_parts_mut` below is okay
2017 let (us_len, ts_len) = rest.align_to_offsets::<U>();
2019 from_raw_parts(rest.as_ptr() as *const U, us_len),
2020 from_raw_parts(rest.as_ptr().add(rest.len() - ts_len), ts_len))
2024 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
2027 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
2028 /// slice of a new type, and the suffix slice. The method does a best effort to make the
2029 /// middle slice the greatest length possible for a given type and input slice, but only
2030 /// your algorithm's performance should depend on that, not its correctness.
2032 /// This method has no purpose when either input element `T` or output element `U` are
2033 /// zero-sized and will return the original slice without splitting anything.
2037 /// This method is essentially a `transmute` with respect to the elements in the returned
2038 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
2046 /// let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
2047 /// let (prefix, shorts, suffix) = bytes.align_to_mut::<u16>();
2048 /// // less_efficient_algorithm_for_bytes(prefix);
2049 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
2050 /// // less_efficient_algorithm_for_bytes(suffix);
2053 #[stable(feature = "slice_align_to", since = "1.30.0")]
2054 pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T]) {
2055 // Note that most of this function will be constant-evaluated,
2056 if ::mem::size_of::<U>() == 0 || ::mem::size_of::<T>() == 0 {
2057 // handle ZSTs specially, which is – don't handle them at all.
2058 return (self, &mut [], &mut []);
2061 // First, find at what point do we split between the first and 2nd slice. Easy with
2062 // ptr.align_offset.
2063 let ptr = self.as_ptr();
2064 let offset = ::ptr::align_offset(ptr, ::mem::align_of::<U>());
2065 if offset > self.len() {
2066 (self, &mut [], &mut [])
2068 let (left, rest) = self.split_at_mut(offset);
2069 // now `rest` is definitely aligned, so `from_raw_parts_mut` below is okay
2070 let (us_len, ts_len) = rest.align_to_offsets::<U>();
2071 let mut_ptr = rest.as_mut_ptr();
2073 from_raw_parts_mut(mut_ptr as *mut U, us_len),
2074 from_raw_parts_mut(mut_ptr.add(rest.len() - ts_len), ts_len))
2079 #[lang = "slice_u8"]
2082 /// Checks if all bytes in this slice are within the ASCII range.
2083 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2085 pub fn is_ascii(&self) -> bool {
2086 self.iter().all(|b| b.is_ascii())
2089 /// Checks that two slices are an ASCII case-insensitive match.
2091 /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
2092 /// but without allocating and copying temporaries.
2093 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2095 pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool {
2096 self.len() == other.len() &&
2097 self.iter().zip(other).all(|(a, b)| {
2098 a.eq_ignore_ascii_case(b)
2102 /// Converts this slice to its ASCII upper case equivalent in-place.
2104 /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
2105 /// but non-ASCII letters are unchanged.
2107 /// To return a new uppercased value without modifying the existing one, use
2108 /// [`to_ascii_uppercase`].
2110 /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
2111 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2113 pub fn make_ascii_uppercase(&mut self) {
2115 byte.make_ascii_uppercase();
2119 /// Converts this slice to its ASCII lower case equivalent in-place.
2121 /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
2122 /// but non-ASCII letters are unchanged.
2124 /// To return a new lowercased value without modifying the existing one, use
2125 /// [`to_ascii_lowercase`].
2127 /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
2128 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2130 pub fn make_ascii_lowercase(&mut self) {
2132 byte.make_ascii_lowercase();
2138 #[stable(feature = "rust1", since = "1.0.0")]
2139 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
2140 impl<T, I> ops::Index<I> for [T]
2141 where I: SliceIndex<[T]>
2143 type Output = I::Output;
2146 fn index(&self, index: I) -> &I::Output {
2151 #[stable(feature = "rust1", since = "1.0.0")]
2152 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
2153 impl<T, I> ops::IndexMut<I> for [T]
2154 where I: SliceIndex<[T]>
2157 fn index_mut(&mut self, index: I) -> &mut I::Output {
2158 index.index_mut(self)
2164 fn slice_index_len_fail(index: usize, len: usize) -> ! {
2165 panic!("index {} out of range for slice of length {}", index, len);
2170 fn slice_index_order_fail(index: usize, end: usize) -> ! {
2171 panic!("slice index starts at {} but ends at {}", index, end);
2176 fn slice_index_overflow_fail() -> ! {
2177 panic!("attempted to index slice up to maximum usize");
2180 mod private_slice_index {
2182 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2185 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2186 impl Sealed for usize {}
2187 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2188 impl Sealed for ops::Range<usize> {}
2189 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2190 impl Sealed for ops::RangeTo<usize> {}
2191 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2192 impl Sealed for ops::RangeFrom<usize> {}
2193 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2194 impl Sealed for ops::RangeFull {}
2195 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2196 impl Sealed for ops::RangeInclusive<usize> {}
2197 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2198 impl Sealed for ops::RangeToInclusive<usize> {}
2201 /// A helper trait used for indexing operations.
2202 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2203 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
2204 pub trait SliceIndex<T: ?Sized>: private_slice_index::Sealed {
2205 /// The output type returned by methods.
2206 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2207 type Output: ?Sized;
2209 /// Returns a shared reference to the output at this location, if in
2211 #[unstable(feature = "slice_index_methods", issue = "0")]
2212 fn get(self, slice: &T) -> Option<&Self::Output>;
2214 /// Returns a mutable reference to the output at this location, if in
2216 #[unstable(feature = "slice_index_methods", issue = "0")]
2217 fn get_mut(self, slice: &mut T) -> Option<&mut Self::Output>;
2219 /// Returns a shared reference to the output at this location, without
2220 /// performing any bounds checking.
2221 #[unstable(feature = "slice_index_methods", issue = "0")]
2222 unsafe fn get_unchecked(self, slice: &T) -> &Self::Output;
2224 /// Returns a mutable reference to the output at this location, without
2225 /// performing any bounds checking.
2226 #[unstable(feature = "slice_index_methods", issue = "0")]
2227 unsafe fn get_unchecked_mut(self, slice: &mut T) -> &mut Self::Output;
2229 /// Returns a shared reference to the output at this location, panicking
2230 /// if out of bounds.
2231 #[unstable(feature = "slice_index_methods", issue = "0")]
2232 fn index(self, slice: &T) -> &Self::Output;
2234 /// Returns a mutable reference to the output at this location, panicking
2235 /// if out of bounds.
2236 #[unstable(feature = "slice_index_methods", issue = "0")]
2237 fn index_mut(self, slice: &mut T) -> &mut Self::Output;
2240 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2241 impl<T> SliceIndex<[T]> for usize {
2245 fn get(self, slice: &[T]) -> Option<&T> {
2246 if self < slice.len() {
2248 Some(self.get_unchecked(slice))
2256 fn get_mut(self, slice: &mut [T]) -> Option<&mut T> {
2257 if self < slice.len() {
2259 Some(self.get_unchecked_mut(slice))
2267 unsafe fn get_unchecked(self, slice: &[T]) -> &T {
2268 &*slice.as_ptr().add(self)
2272 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut T {
2273 &mut *slice.as_mut_ptr().add(self)
2277 fn index(self, slice: &[T]) -> &T {
2278 // NB: use intrinsic indexing
2283 fn index_mut(self, slice: &mut [T]) -> &mut T {
2284 // NB: use intrinsic indexing
2289 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2290 impl<T> SliceIndex<[T]> for ops::Range<usize> {
2294 fn get(self, slice: &[T]) -> Option<&[T]> {
2295 if self.start > self.end || self.end > slice.len() {
2299 Some(self.get_unchecked(slice))
2305 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2306 if self.start > self.end || self.end > slice.len() {
2310 Some(self.get_unchecked_mut(slice))
2316 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2317 from_raw_parts(slice.as_ptr().add(self.start), self.end - self.start)
2321 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2322 from_raw_parts_mut(slice.as_mut_ptr().add(self.start), self.end - self.start)
2326 fn index(self, slice: &[T]) -> &[T] {
2327 if self.start > self.end {
2328 slice_index_order_fail(self.start, self.end);
2329 } else if self.end > slice.len() {
2330 slice_index_len_fail(self.end, slice.len());
2333 self.get_unchecked(slice)
2338 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2339 if self.start > self.end {
2340 slice_index_order_fail(self.start, self.end);
2341 } else if self.end > slice.len() {
2342 slice_index_len_fail(self.end, slice.len());
2345 self.get_unchecked_mut(slice)
2350 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2351 impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {
2355 fn get(self, slice: &[T]) -> Option<&[T]> {
2356 (0..self.end).get(slice)
2360 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2361 (0..self.end).get_mut(slice)
2365 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2366 (0..self.end).get_unchecked(slice)
2370 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2371 (0..self.end).get_unchecked_mut(slice)
2375 fn index(self, slice: &[T]) -> &[T] {
2376 (0..self.end).index(slice)
2380 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2381 (0..self.end).index_mut(slice)
2385 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2386 impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {
2390 fn get(self, slice: &[T]) -> Option<&[T]> {
2391 (self.start..slice.len()).get(slice)
2395 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2396 (self.start..slice.len()).get_mut(slice)
2400 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2401 (self.start..slice.len()).get_unchecked(slice)
2405 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2406 (self.start..slice.len()).get_unchecked_mut(slice)
2410 fn index(self, slice: &[T]) -> &[T] {
2411 (self.start..slice.len()).index(slice)
2415 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2416 (self.start..slice.len()).index_mut(slice)
2420 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2421 impl<T> SliceIndex<[T]> for ops::RangeFull {
2425 fn get(self, slice: &[T]) -> Option<&[T]> {
2430 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2435 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2440 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2445 fn index(self, slice: &[T]) -> &[T] {
2450 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2456 #[stable(feature = "inclusive_range", since = "1.26.0")]
2457 impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> {
2461 fn get(self, slice: &[T]) -> Option<&[T]> {
2462 if *self.end() == usize::max_value() { None }
2463 else { (*self.start()..self.end() + 1).get(slice) }
2467 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2468 if *self.end() == usize::max_value() { None }
2469 else { (*self.start()..self.end() + 1).get_mut(slice) }
2473 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2474 (*self.start()..self.end() + 1).get_unchecked(slice)
2478 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2479 (*self.start()..self.end() + 1).get_unchecked_mut(slice)
2483 fn index(self, slice: &[T]) -> &[T] {
2484 if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
2485 (*self.start()..self.end() + 1).index(slice)
2489 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2490 if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
2491 (*self.start()..self.end() + 1).index_mut(slice)
2495 #[stable(feature = "inclusive_range", since = "1.26.0")]
2496 impl<T> SliceIndex<[T]> for ops::RangeToInclusive<usize> {
2500 fn get(self, slice: &[T]) -> Option<&[T]> {
2501 (0..=self.end).get(slice)
2505 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2506 (0..=self.end).get_mut(slice)
2510 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2511 (0..=self.end).get_unchecked(slice)
2515 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2516 (0..=self.end).get_unchecked_mut(slice)
2520 fn index(self, slice: &[T]) -> &[T] {
2521 (0..=self.end).index(slice)
2525 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2526 (0..=self.end).index_mut(slice)
2530 ////////////////////////////////////////////////////////////////////////////////
2532 ////////////////////////////////////////////////////////////////////////////////
2534 #[stable(feature = "rust1", since = "1.0.0")]
2535 impl<T> Default for &[T] {
2536 /// Creates an empty slice.
2537 fn default() -> Self { &[] }
2540 #[stable(feature = "mut_slice_default", since = "1.5.0")]
2541 impl<T> Default for &mut [T] {
2542 /// Creates a mutable empty slice.
2543 fn default() -> Self { &mut [] }
2550 #[stable(feature = "rust1", since = "1.0.0")]
2551 impl<'a, T> IntoIterator for &'a [T] {
2553 type IntoIter = Iter<'a, T>;
2555 fn into_iter(self) -> Iter<'a, T> {
2560 #[stable(feature = "rust1", since = "1.0.0")]
2561 impl<'a, T> IntoIterator for &'a mut [T] {
2562 type Item = &'a mut T;
2563 type IntoIter = IterMut<'a, T>;
2565 fn into_iter(self) -> IterMut<'a, T> {
2570 // Macro helper functions
2572 fn size_from_ptr<T>(_: *const T) -> usize {
2576 // Inlining is_empty and len makes a huge performance difference
2577 macro_rules! is_empty {
2578 // The way we encode the length of a ZST iterator, this works both for ZST
2580 ($self: ident) => {$self.ptr == $self.end}
2582 // To get rid of some bounds checks (see `position`), we compute the length in a somewhat
2583 // unexpected way. (Tested by `codegen/slice-position-bounds-check`.)
2585 ($self: ident) => {{
2586 let start = $self.ptr;
2587 let diff = ($self.end as usize).wrapping_sub(start as usize);
2588 let size = size_from_ptr(start);
2592 // Using division instead of `offset_from` helps LLVM remove bounds checks
2598 // The shared definition of the `Iter` and `IterMut` iterators
2599 macro_rules! iterator {
2600 (struct $name:ident -> $ptr:ty, $elem:ty, $raw_mut:tt, $( $mut_:tt )*) => {
2601 impl<'a, T> $name<'a, T> {
2602 // Helper function for creating a slice from the iterator.
2604 fn make_slice(&self) -> &'a [T] {
2605 unsafe { from_raw_parts(self.ptr, len!(self)) }
2608 // Helper function for moving the start of the iterator forwards by `offset` elements,
2609 // returning the old start.
2610 // Unsafe because the offset must be in-bounds or one-past-the-end.
2612 unsafe fn post_inc_start(&mut self, offset: isize) -> * $raw_mut T {
2613 if mem::size_of::<T>() == 0 {
2614 // This is *reducing* the length. `ptr` never changes with ZST.
2615 self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
2619 self.ptr = self.ptr.offset(offset);
2624 // Helper function for moving the end of the iterator backwards by `offset` elements,
2625 // returning the new end.
2626 // Unsafe because the offset must be in-bounds or one-past-the-end.
2628 unsafe fn pre_dec_end(&mut self, offset: isize) -> * $raw_mut T {
2629 if mem::size_of::<T>() == 0 {
2630 self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
2633 self.end = self.end.offset(-offset);
2639 #[stable(feature = "rust1", since = "1.0.0")]
2640 impl<'a, T> ExactSizeIterator for $name<'a, T> {
2642 fn len(&self) -> usize {
2647 fn is_empty(&self) -> bool {
2652 #[stable(feature = "rust1", since = "1.0.0")]
2653 impl<'a, T> Iterator for $name<'a, T> {
2657 fn next(&mut self) -> Option<$elem> {
2658 // could be implemented with slices, but this avoids bounds checks
2660 assume(!self.ptr.is_null());
2661 if mem::size_of::<T>() != 0 {
2662 assume(!self.end.is_null());
2664 if is_empty!(self) {
2667 Some(& $( $mut_ )* *self.post_inc_start(1))
2673 fn size_hint(&self) -> (usize, Option<usize>) {
2674 let exact = len!(self);
2675 (exact, Some(exact))
2679 fn count(self) -> usize {
2684 fn nth(&mut self, n: usize) -> Option<$elem> {
2685 if n >= len!(self) {
2686 // This iterator is now empty.
2687 if mem::size_of::<T>() == 0 {
2688 // We have to do it this way as `ptr` may never be 0, but `end`
2689 // could be (due to wrapping).
2690 self.end = self.ptr;
2692 self.ptr = self.end;
2696 // We are in bounds. `offset` does the right thing even for ZSTs.
2698 let elem = Some(& $( $mut_ )* *self.ptr.add(n));
2699 self.post_inc_start((n as isize).wrapping_add(1));
2705 fn last(mut self) -> Option<$elem> {
2710 fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where
2711 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
2713 // manual unrolling is needed when there are conditional exits from the loop
2714 let mut accum = init;
2716 while len!(self) >= 4 {
2717 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2718 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2719 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2720 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2722 while !is_empty!(self) {
2723 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2730 fn fold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
2731 where Fold: FnMut(Acc, Self::Item) -> Acc,
2733 // Let LLVM unroll this, rather than using the default
2734 // impl that would force the manual unrolling above
2735 let mut accum = init;
2736 while let Some(x) = self.next() {
2737 accum = f(accum, x);
2743 #[rustc_inherit_overflow_checks]
2744 fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
2746 P: FnMut(Self::Item) -> bool,
2748 // The addition might panic on overflow.
2750 self.try_fold(0, move |i, x| {
2751 if predicate(x) { Err(i) }
2755 unsafe { assume(i < n) };
2761 fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where
2762 P: FnMut(Self::Item) -> bool,
2763 Self: Sized + ExactSizeIterator + DoubleEndedIterator
2765 // No need for an overflow check here, because `ExactSizeIterator`
2767 self.try_rfold(n, move |i, x| {
2769 if predicate(x) { Err(i) }
2773 unsafe { assume(i < n) };
2779 #[stable(feature = "rust1", since = "1.0.0")]
2780 impl<'a, T> DoubleEndedIterator for $name<'a, T> {
2782 fn next_back(&mut self) -> Option<$elem> {
2783 // could be implemented with slices, but this avoids bounds checks
2785 assume(!self.ptr.is_null());
2786 if mem::size_of::<T>() != 0 {
2787 assume(!self.end.is_null());
2789 if is_empty!(self) {
2792 Some(& $( $mut_ )* *self.pre_dec_end(1))
2798 fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where
2799 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
2801 // manual unrolling is needed when there are conditional exits from the loop
2802 let mut accum = init;
2804 while len!(self) >= 4 {
2805 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2806 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2807 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2808 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2810 // inlining is_empty everywhere makes a huge performance difference
2811 while !is_empty!(self) {
2812 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2819 fn rfold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
2820 where Fold: FnMut(Acc, Self::Item) -> Acc,
2822 // Let LLVM unroll this, rather than using the default
2823 // impl that would force the manual unrolling above
2824 let mut accum = init;
2825 while let Some(x) = self.next_back() {
2826 accum = f(accum, x);
2832 #[stable(feature = "fused", since = "1.26.0")]
2833 impl<'a, T> FusedIterator for $name<'a, T> {}
2835 #[unstable(feature = "trusted_len", issue = "37572")]
2836 unsafe impl<'a, T> TrustedLen for $name<'a, T> {}
2840 /// Immutable slice iterator
2842 /// This struct is created by the [`iter`] method on [slices].
2849 /// // First, we declare a type which has `iter` method to get the `Iter` struct (&[usize here]):
2850 /// let slice = &[1, 2, 3];
2852 /// // Then, we iterate over it:
2853 /// for element in slice.iter() {
2854 /// println!("{}", element);
2858 /// [`iter`]: ../../std/primitive.slice.html#method.iter
2859 /// [slices]: ../../std/primitive.slice.html
2860 #[stable(feature = "rust1", since = "1.0.0")]
2861 pub struct Iter<'a, T: 'a> {
2863 end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
2864 // ptr == end is a quick test for the Iterator being empty, that works
2865 // for both ZST and non-ZST.
2866 _marker: marker::PhantomData<&'a T>,
2869 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2870 impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
2871 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2872 f.debug_tuple("Iter")
2873 .field(&self.as_slice())
2878 #[stable(feature = "rust1", since = "1.0.0")]
2879 unsafe impl<T: Sync> Sync for Iter<'_, T> {}
2880 #[stable(feature = "rust1", since = "1.0.0")]
2881 unsafe impl<T: Sync> Send for Iter<'_, T> {}
2883 impl<'a, T> Iter<'a, T> {
2884 /// View the underlying data as a subslice of the original data.
2886 /// This has the same lifetime as the original slice, and so the
2887 /// iterator can continue to be used while this exists.
2894 /// // First, we declare a type which has the `iter` method to get the `Iter`
2895 /// // struct (&[usize here]):
2896 /// let slice = &[1, 2, 3];
2898 /// // Then, we get the iterator:
2899 /// let mut iter = slice.iter();
2900 /// // So if we print what `as_slice` method returns here, we have "[1, 2, 3]":
2901 /// println!("{:?}", iter.as_slice());
2903 /// // Next, we move to the second element of the slice:
2905 /// // Now `as_slice` returns "[2, 3]":
2906 /// println!("{:?}", iter.as_slice());
2908 #[stable(feature = "iter_to_slice", since = "1.4.0")]
2909 pub fn as_slice(&self) -> &'a [T] {
2914 iterator!{struct Iter -> *const T, &'a T, const, /* no mut */}
2916 #[stable(feature = "rust1", since = "1.0.0")]
2917 impl<T> Clone for Iter<'_, T> {
2918 fn clone(&self) -> Self { Iter { ptr: self.ptr, end: self.end, _marker: self._marker } }
2921 #[stable(feature = "slice_iter_as_ref", since = "1.13.0")]
2922 impl<T> AsRef<[T]> for Iter<'_, T> {
2923 fn as_ref(&self) -> &[T] {
2928 /// Mutable slice iterator.
2930 /// This struct is created by the [`iter_mut`] method on [slices].
2937 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
2938 /// // struct (&[usize here]):
2939 /// let mut slice = &mut [1, 2, 3];
2941 /// // Then, we iterate over it and increment each element value:
2942 /// for element in slice.iter_mut() {
2946 /// // We now have "[2, 3, 4]":
2947 /// println!("{:?}", slice);
2950 /// [`iter_mut`]: ../../std/primitive.slice.html#method.iter_mut
2951 /// [slices]: ../../std/primitive.slice.html
2952 #[stable(feature = "rust1", since = "1.0.0")]
2953 pub struct IterMut<'a, T: 'a> {
2955 end: *mut T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
2956 // ptr == end is a quick test for the Iterator being empty, that works
2957 // for both ZST and non-ZST.
2958 _marker: marker::PhantomData<&'a mut T>,
2961 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2962 impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
2963 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2964 f.debug_tuple("IterMut")
2965 .field(&self.make_slice())
2970 #[stable(feature = "rust1", since = "1.0.0")]
2971 unsafe impl<T: Sync> Sync for IterMut<'_, T> {}
2972 #[stable(feature = "rust1", since = "1.0.0")]
2973 unsafe impl<T: Send> Send for IterMut<'_, T> {}
2975 impl<'a, T> IterMut<'a, T> {
2976 /// View the underlying data as a subslice of the original data.
2978 /// To avoid creating `&mut` references that alias, this is forced
2979 /// to consume the iterator.
2986 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
2987 /// // struct (&[usize here]):
2988 /// let mut slice = &mut [1, 2, 3];
2991 /// // Then, we get the iterator:
2992 /// let mut iter = slice.iter_mut();
2993 /// // We move to next element:
2995 /// // So if we print what `into_slice` method returns here, we have "[2, 3]":
2996 /// println!("{:?}", iter.into_slice());
2999 /// // Now let's modify a value of the slice:
3001 /// // First we get back the iterator:
3002 /// let mut iter = slice.iter_mut();
3003 /// // We change the value of the first element of the slice returned by the `next` method:
3004 /// *iter.next().unwrap() += 1;
3006 /// // Now slice is "[2, 2, 3]":
3007 /// println!("{:?}", slice);
3009 #[stable(feature = "iter_to_slice", since = "1.4.0")]
3010 pub fn into_slice(self) -> &'a mut [T] {
3011 unsafe { from_raw_parts_mut(self.ptr, len!(self)) }
3015 iterator!{struct IterMut -> *mut T, &'a mut T, mut, mut}
3017 /// An internal abstraction over the splitting iterators, so that
3018 /// splitn, splitn_mut etc can be implemented once.
3020 trait SplitIter: DoubleEndedIterator {
3021 /// Marks the underlying iterator as complete, extracting the remaining
3022 /// portion of the slice.
3023 fn finish(&mut self) -> Option<Self::Item>;
3026 /// An iterator over subslices separated by elements that match a predicate
3029 /// This struct is created by the [`split`] method on [slices].
3031 /// [`split`]: ../../std/primitive.slice.html#method.split
3032 /// [slices]: ../../std/primitive.slice.html
3033 #[stable(feature = "rust1", since = "1.0.0")]
3034 pub struct Split<'a, T:'a, P> where P: FnMut(&T) -> bool {
3040 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3041 impl<T: fmt::Debug, P> fmt::Debug for Split<'_, T, P> where P: FnMut(&T) -> bool {
3042 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3043 f.debug_struct("Split")
3044 .field("v", &self.v)
3045 .field("finished", &self.finished)
3050 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3051 #[stable(feature = "rust1", since = "1.0.0")]
3052 impl<T, P> Clone for Split<'_, T, P> where P: Clone + FnMut(&T) -> bool {
3053 fn clone(&self) -> Self {
3056 pred: self.pred.clone(),
3057 finished: self.finished,
3062 #[stable(feature = "rust1", since = "1.0.0")]
3063 impl<'a, T, P> Iterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
3064 type Item = &'a [T];
3067 fn next(&mut self) -> Option<&'a [T]> {
3068 if self.finished { return None; }
3070 match self.v.iter().position(|x| (self.pred)(x)) {
3071 None => self.finish(),
3073 let ret = Some(&self.v[..idx]);
3074 self.v = &self.v[idx + 1..];
3081 fn size_hint(&self) -> (usize, Option<usize>) {
3085 (1, Some(self.v.len() + 1))
3090 #[stable(feature = "rust1", since = "1.0.0")]
3091 impl<'a, T, P> DoubleEndedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
3093 fn next_back(&mut self) -> Option<&'a [T]> {
3094 if self.finished { return None; }
3096 match self.v.iter().rposition(|x| (self.pred)(x)) {
3097 None => self.finish(),
3099 let ret = Some(&self.v[idx + 1..]);
3100 self.v = &self.v[..idx];
3107 impl<'a, T, P> SplitIter for Split<'a, T, P> where P: FnMut(&T) -> bool {
3109 fn finish(&mut self) -> Option<&'a [T]> {
3110 if self.finished { None } else { self.finished = true; Some(self.v) }
3114 #[stable(feature = "fused", since = "1.26.0")]
3115 impl<T, P> FusedIterator for Split<'_, T, P> where P: FnMut(&T) -> bool {}
3117 /// An iterator over the subslices of the vector which are separated
3118 /// by elements that match `pred`.
3120 /// This struct is created by the [`split_mut`] method on [slices].
3122 /// [`split_mut`]: ../../std/primitive.slice.html#method.split_mut
3123 /// [slices]: ../../std/primitive.slice.html
3124 #[stable(feature = "rust1", since = "1.0.0")]
3125 pub struct SplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
3131 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3132 impl<T: fmt::Debug, P> fmt::Debug for SplitMut<'_, T, P> where P: FnMut(&T) -> bool {
3133 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3134 f.debug_struct("SplitMut")
3135 .field("v", &self.v)
3136 .field("finished", &self.finished)
3141 impl<'a, T, P> SplitIter for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3143 fn finish(&mut self) -> Option<&'a mut [T]> {
3147 self.finished = true;
3148 Some(mem::replace(&mut self.v, &mut []))
3153 #[stable(feature = "rust1", since = "1.0.0")]
3154 impl<'a, T, P> Iterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3155 type Item = &'a mut [T];
3158 fn next(&mut self) -> Option<&'a mut [T]> {
3159 if self.finished { return None; }
3161 let idx_opt = { // work around borrowck limitations
3162 let pred = &mut self.pred;
3163 self.v.iter().position(|x| (*pred)(x))
3166 None => self.finish(),
3168 let tmp = mem::replace(&mut self.v, &mut []);
3169 let (head, tail) = tmp.split_at_mut(idx);
3170 self.v = &mut tail[1..];
3177 fn size_hint(&self) -> (usize, Option<usize>) {
3181 // if the predicate doesn't match anything, we yield one slice
3182 // if it matches every element, we yield len+1 empty slices.
3183 (1, Some(self.v.len() + 1))
3188 #[stable(feature = "rust1", since = "1.0.0")]
3189 impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> where
3190 P: FnMut(&T) -> bool,
3193 fn next_back(&mut self) -> Option<&'a mut [T]> {
3194 if self.finished { return None; }
3196 let idx_opt = { // work around borrowck limitations
3197 let pred = &mut self.pred;
3198 self.v.iter().rposition(|x| (*pred)(x))
3201 None => self.finish(),
3203 let tmp = mem::replace(&mut self.v, &mut []);
3204 let (head, tail) = tmp.split_at_mut(idx);
3206 Some(&mut tail[1..])
3212 #[stable(feature = "fused", since = "1.26.0")]
3213 impl<T, P> FusedIterator for SplitMut<'_, T, P> where P: FnMut(&T) -> bool {}
3215 /// An iterator over subslices separated by elements that match a predicate
3216 /// function, starting from the end of the slice.
3218 /// This struct is created by the [`rsplit`] method on [slices].
3220 /// [`rsplit`]: ../../std/primitive.slice.html#method.rsplit
3221 /// [slices]: ../../std/primitive.slice.html
3222 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3223 #[derive(Clone)] // Is this correct, or does it incorrectly require `T: Clone`?
3224 pub struct RSplit<'a, T:'a, P> where P: FnMut(&T) -> bool {
3225 inner: Split<'a, T, P>
3228 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3229 impl<T: fmt::Debug, P> fmt::Debug for RSplit<'_, T, P> where P: FnMut(&T) -> bool {
3230 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3231 f.debug_struct("RSplit")
3232 .field("v", &self.inner.v)
3233 .field("finished", &self.inner.finished)
3238 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3239 impl<'a, T, P> Iterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3240 type Item = &'a [T];
3243 fn next(&mut self) -> Option<&'a [T]> {
3244 self.inner.next_back()
3248 fn size_hint(&self) -> (usize, Option<usize>) {
3249 self.inner.size_hint()
3253 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3254 impl<'a, T, P> DoubleEndedIterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3256 fn next_back(&mut self) -> Option<&'a [T]> {
3261 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3262 impl<'a, T, P> SplitIter for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3264 fn finish(&mut self) -> Option<&'a [T]> {
3269 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3270 impl<T, P> FusedIterator for RSplit<'_, T, P> where P: FnMut(&T) -> bool {}
3272 /// An iterator over the subslices of the vector which are separated
3273 /// by elements that match `pred`, starting from the end of the slice.
3275 /// This struct is created by the [`rsplit_mut`] method on [slices].
3277 /// [`rsplit_mut`]: ../../std/primitive.slice.html#method.rsplit_mut
3278 /// [slices]: ../../std/primitive.slice.html
3279 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3280 pub struct RSplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
3281 inner: SplitMut<'a, T, P>
3284 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3285 impl<T: fmt::Debug, P> fmt::Debug for RSplitMut<'_, T, P> where P: FnMut(&T) -> bool {
3286 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3287 f.debug_struct("RSplitMut")
3288 .field("v", &self.inner.v)
3289 .field("finished", &self.inner.finished)
3294 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3295 impl<'a, T, P> SplitIter for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3297 fn finish(&mut self) -> Option<&'a mut [T]> {
3302 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3303 impl<'a, T, P> Iterator for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3304 type Item = &'a mut [T];
3307 fn next(&mut self) -> Option<&'a mut [T]> {
3308 self.inner.next_back()
3312 fn size_hint(&self) -> (usize, Option<usize>) {
3313 self.inner.size_hint()
3317 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3318 impl<'a, T, P> DoubleEndedIterator for RSplitMut<'a, T, P> where
3319 P: FnMut(&T) -> bool,
3322 fn next_back(&mut self) -> Option<&'a mut [T]> {
3327 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3328 impl<T, P> FusedIterator for RSplitMut<'_, T, P> where P: FnMut(&T) -> bool {}
3330 /// An private iterator over subslices separated by elements that
3331 /// match a predicate function, splitting at most a fixed number of
3334 struct GenericSplitN<I> {
3339 impl<T, I: SplitIter<Item=T>> Iterator for GenericSplitN<I> {
3343 fn next(&mut self) -> Option<T> {
3346 1 => { self.count -= 1; self.iter.finish() }
3347 _ => { self.count -= 1; self.iter.next() }
3352 fn size_hint(&self) -> (usize, Option<usize>) {
3353 let (lower, upper_opt) = self.iter.size_hint();
3354 (lower, upper_opt.map(|upper| cmp::min(self.count, upper)))
3358 /// An iterator over subslices separated by elements that match a predicate
3359 /// function, limited to a given number of splits.
3361 /// This struct is created by the [`splitn`] method on [slices].
3363 /// [`splitn`]: ../../std/primitive.slice.html#method.splitn
3364 /// [slices]: ../../std/primitive.slice.html
3365 #[stable(feature = "rust1", since = "1.0.0")]
3366 pub struct SplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3367 inner: GenericSplitN<Split<'a, T, P>>
3370 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3371 impl<T: fmt::Debug, P> fmt::Debug for SplitN<'_, T, P> where P: FnMut(&T) -> bool {
3372 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3373 f.debug_struct("SplitN")
3374 .field("inner", &self.inner)
3379 /// An iterator over subslices separated by elements that match a
3380 /// predicate function, limited to a given number of splits, starting
3381 /// from the end of the slice.
3383 /// This struct is created by the [`rsplitn`] method on [slices].
3385 /// [`rsplitn`]: ../../std/primitive.slice.html#method.rsplitn
3386 /// [slices]: ../../std/primitive.slice.html
3387 #[stable(feature = "rust1", since = "1.0.0")]
3388 pub struct RSplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3389 inner: GenericSplitN<RSplit<'a, T, P>>
3392 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3393 impl<T: fmt::Debug, P> fmt::Debug for RSplitN<'_, T, P> where P: FnMut(&T) -> bool {
3394 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3395 f.debug_struct("RSplitN")
3396 .field("inner", &self.inner)
3401 /// An iterator over subslices separated by elements that match a predicate
3402 /// function, limited to a given number of splits.
3404 /// This struct is created by the [`splitn_mut`] method on [slices].
3406 /// [`splitn_mut`]: ../../std/primitive.slice.html#method.splitn_mut
3407 /// [slices]: ../../std/primitive.slice.html
3408 #[stable(feature = "rust1", since = "1.0.0")]
3409 pub struct SplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3410 inner: GenericSplitN<SplitMut<'a, T, P>>
3413 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3414 impl<T: fmt::Debug, P> fmt::Debug for SplitNMut<'_, T, P> where P: FnMut(&T) -> bool {
3415 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3416 f.debug_struct("SplitNMut")
3417 .field("inner", &self.inner)
3422 /// An iterator over subslices separated by elements that match a
3423 /// predicate function, limited to a given number of splits, starting
3424 /// from the end of the slice.
3426 /// This struct is created by the [`rsplitn_mut`] method on [slices].
3428 /// [`rsplitn_mut`]: ../../std/primitive.slice.html#method.rsplitn_mut
3429 /// [slices]: ../../std/primitive.slice.html
3430 #[stable(feature = "rust1", since = "1.0.0")]
3431 pub struct RSplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3432 inner: GenericSplitN<RSplitMut<'a, T, P>>
3435 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3436 impl<T: fmt::Debug, P> fmt::Debug for RSplitNMut<'_, T, P> where P: FnMut(&T) -> bool {
3437 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3438 f.debug_struct("RSplitNMut")
3439 .field("inner", &self.inner)
3444 macro_rules! forward_iterator {
3445 ($name:ident: $elem:ident, $iter_of:ty) => {
3446 #[stable(feature = "rust1", since = "1.0.0")]
3447 impl<'a, $elem, P> Iterator for $name<'a, $elem, P> where
3448 P: FnMut(&T) -> bool
3450 type Item = $iter_of;
3453 fn next(&mut self) -> Option<$iter_of> {
3458 fn size_hint(&self) -> (usize, Option<usize>) {
3459 self.inner.size_hint()
3463 #[stable(feature = "fused", since = "1.26.0")]
3464 impl<'a, $elem, P> FusedIterator for $name<'a, $elem, P>
3465 where P: FnMut(&T) -> bool {}
3469 forward_iterator! { SplitN: T, &'a [T] }
3470 forward_iterator! { RSplitN: T, &'a [T] }
3471 forward_iterator! { SplitNMut: T, &'a mut [T] }
3472 forward_iterator! { RSplitNMut: T, &'a mut [T] }
3474 /// An iterator over overlapping subslices of length `size`.
3476 /// This struct is created by the [`windows`] method on [slices].
3478 /// [`windows`]: ../../std/primitive.slice.html#method.windows
3479 /// [slices]: ../../std/primitive.slice.html
3481 #[stable(feature = "rust1", since = "1.0.0")]
3482 pub struct Windows<'a, T:'a> {
3487 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3488 #[stable(feature = "rust1", since = "1.0.0")]
3489 impl<T> Clone for Windows<'_, T> {
3490 fn clone(&self) -> Self {
3498 #[stable(feature = "rust1", since = "1.0.0")]
3499 impl<'a, T> Iterator for Windows<'a, T> {
3500 type Item = &'a [T];
3503 fn next(&mut self) -> Option<&'a [T]> {
3504 if self.size > self.v.len() {
3507 let ret = Some(&self.v[..self.size]);
3508 self.v = &self.v[1..];
3514 fn size_hint(&self) -> (usize, Option<usize>) {
3515 if self.size > self.v.len() {
3518 let size = self.v.len() - self.size + 1;
3524 fn count(self) -> usize {
3529 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3530 let (end, overflow) = self.size.overflowing_add(n);
3531 if end > self.v.len() || overflow {
3535 let nth = &self.v[n..end];
3536 self.v = &self.v[n+1..];
3542 fn last(self) -> Option<Self::Item> {
3543 if self.size > self.v.len() {
3546 let start = self.v.len() - self.size;
3547 Some(&self.v[start..])
3552 #[stable(feature = "rust1", since = "1.0.0")]
3553 impl<'a, T> DoubleEndedIterator for Windows<'a, T> {
3555 fn next_back(&mut self) -> Option<&'a [T]> {
3556 if self.size > self.v.len() {
3559 let ret = Some(&self.v[self.v.len()-self.size..]);
3560 self.v = &self.v[..self.v.len()-1];
3566 #[stable(feature = "rust1", since = "1.0.0")]
3567 impl<T> ExactSizeIterator for Windows<'_, T> {}
3569 #[unstable(feature = "trusted_len", issue = "37572")]
3570 unsafe impl<T> TrustedLen for Windows<'_, T> {}
3572 #[stable(feature = "fused", since = "1.26.0")]
3573 impl<T> FusedIterator for Windows<'_, T> {}
3576 unsafe impl<'a, T> TrustedRandomAccess for Windows<'a, T> {
3577 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3578 from_raw_parts(self.v.as_ptr().add(i), self.size)
3580 fn may_have_side_effect() -> bool { false }
3583 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
3586 /// When the slice len is not evenly divided by the chunk size, the last slice
3587 /// of the iteration will be the remainder.
3589 /// This struct is created by the [`chunks`] method on [slices].
3591 /// [`chunks`]: ../../std/primitive.slice.html#method.chunks
3592 /// [slices]: ../../std/primitive.slice.html
3594 #[stable(feature = "rust1", since = "1.0.0")]
3595 pub struct Chunks<'a, T:'a> {
3600 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3601 #[stable(feature = "rust1", since = "1.0.0")]
3602 impl<T> Clone for Chunks<'_, T> {
3603 fn clone(&self) -> Self {
3606 chunk_size: self.chunk_size,
3611 #[stable(feature = "rust1", since = "1.0.0")]
3612 impl<'a, T> Iterator for Chunks<'a, T> {
3613 type Item = &'a [T];
3616 fn next(&mut self) -> Option<&'a [T]> {
3617 if self.v.is_empty() {
3620 let chunksz = cmp::min(self.v.len(), self.chunk_size);
3621 let (fst, snd) = self.v.split_at(chunksz);
3628 fn size_hint(&self) -> (usize, Option<usize>) {
3629 if self.v.is_empty() {
3632 let n = self.v.len() / self.chunk_size;
3633 let rem = self.v.len() % self.chunk_size;
3634 let n = if rem > 0 { n+1 } else { n };
3640 fn count(self) -> usize {
3645 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3646 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3647 if start >= self.v.len() || overflow {
3651 let end = match start.checked_add(self.chunk_size) {
3652 Some(sum) => cmp::min(self.v.len(), sum),
3653 None => self.v.len(),
3655 let nth = &self.v[start..end];
3656 self.v = &self.v[end..];
3662 fn last(self) -> Option<Self::Item> {
3663 if self.v.is_empty() {
3666 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
3667 Some(&self.v[start..])
3672 #[stable(feature = "rust1", since = "1.0.0")]
3673 impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
3675 fn next_back(&mut self) -> Option<&'a [T]> {
3676 if self.v.is_empty() {
3679 let remainder = self.v.len() % self.chunk_size;
3680 let chunksz = if remainder != 0 { remainder } else { self.chunk_size };
3681 let (fst, snd) = self.v.split_at(self.v.len() - chunksz);
3688 #[stable(feature = "rust1", since = "1.0.0")]
3689 impl<T> ExactSizeIterator for Chunks<'_, T> {}
3691 #[unstable(feature = "trusted_len", issue = "37572")]
3692 unsafe impl<T> TrustedLen for Chunks<'_, T> {}
3694 #[stable(feature = "fused", since = "1.26.0")]
3695 impl<T> FusedIterator for Chunks<'_, T> {}
3698 unsafe impl<'a, T> TrustedRandomAccess for Chunks<'a, T> {
3699 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3700 let start = i * self.chunk_size;
3701 let end = match start.checked_add(self.chunk_size) {
3702 None => self.v.len(),
3703 Some(end) => cmp::min(end, self.v.len()),
3705 from_raw_parts(self.v.as_ptr().add(start), end - start)
3707 fn may_have_side_effect() -> bool { false }
3710 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3711 /// elements at a time). When the slice len is not evenly divided by the chunk
3712 /// size, the last slice of the iteration will be the remainder.
3714 /// This struct is created by the [`chunks_mut`] method on [slices].
3716 /// [`chunks_mut`]: ../../std/primitive.slice.html#method.chunks_mut
3717 /// [slices]: ../../std/primitive.slice.html
3719 #[stable(feature = "rust1", since = "1.0.0")]
3720 pub struct ChunksMut<'a, T:'a> {
3725 #[stable(feature = "rust1", since = "1.0.0")]
3726 impl<'a, T> Iterator for ChunksMut<'a, T> {
3727 type Item = &'a mut [T];
3730 fn next(&mut self) -> Option<&'a mut [T]> {
3731 if self.v.is_empty() {
3734 let sz = cmp::min(self.v.len(), self.chunk_size);
3735 let tmp = mem::replace(&mut self.v, &mut []);
3736 let (head, tail) = tmp.split_at_mut(sz);
3743 fn size_hint(&self) -> (usize, Option<usize>) {
3744 if self.v.is_empty() {
3747 let n = self.v.len() / self.chunk_size;
3748 let rem = self.v.len() % self.chunk_size;
3749 let n = if rem > 0 { n + 1 } else { n };
3755 fn count(self) -> usize {
3760 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
3761 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3762 if start >= self.v.len() || overflow {
3766 let end = match start.checked_add(self.chunk_size) {
3767 Some(sum) => cmp::min(self.v.len(), sum),
3768 None => self.v.len(),
3770 let tmp = mem::replace(&mut self.v, &mut []);
3771 let (head, tail) = tmp.split_at_mut(end);
3772 let (_, nth) = head.split_at_mut(start);
3779 fn last(self) -> Option<Self::Item> {
3780 if self.v.is_empty() {
3783 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
3784 Some(&mut self.v[start..])
3789 #[stable(feature = "rust1", since = "1.0.0")]
3790 impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
3792 fn next_back(&mut self) -> Option<&'a mut [T]> {
3793 if self.v.is_empty() {
3796 let remainder = self.v.len() % self.chunk_size;
3797 let sz = if remainder != 0 { remainder } else { self.chunk_size };
3798 let tmp = mem::replace(&mut self.v, &mut []);
3799 let tmp_len = tmp.len();
3800 let (head, tail) = tmp.split_at_mut(tmp_len - sz);
3807 #[stable(feature = "rust1", since = "1.0.0")]
3808 impl<T> ExactSizeIterator for ChunksMut<'_, T> {}
3810 #[unstable(feature = "trusted_len", issue = "37572")]
3811 unsafe impl<T> TrustedLen for ChunksMut<'_, T> {}
3813 #[stable(feature = "fused", since = "1.26.0")]
3814 impl<T> FusedIterator for ChunksMut<'_, T> {}
3817 unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> {
3818 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
3819 let start = i * self.chunk_size;
3820 let end = match start.checked_add(self.chunk_size) {
3821 None => self.v.len(),
3822 Some(end) => cmp::min(end, self.v.len()),
3824 from_raw_parts_mut(self.v.as_mut_ptr().add(start), end - start)
3826 fn may_have_side_effect() -> bool { false }
3829 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
3832 /// When the slice len is not evenly divided by the chunk size, the last
3833 /// up to `chunk_size-1` elements will be omitted but can be retrieved from
3834 /// the [`remainder`] function from the iterator.
3836 /// This struct is created by the [`chunks_exact`] method on [slices].
3838 /// [`chunks_exact`]: ../../std/primitive.slice.html#method.chunks_exact
3839 /// [`remainder`]: ../../std/slice/struct.ChunksExact.html#method.remainder
3840 /// [slices]: ../../std/primitive.slice.html
3842 #[unstable(feature = "chunks_exact", issue = "47115")]
3843 pub struct ChunksExact<'a, T:'a> {
3849 #[unstable(feature = "chunks_exact", issue = "47115")]
3850 impl<'a, T> ChunksExact<'a, T> {
3851 /// Return the remainder of the original slice that is not going to be
3852 /// returned by the iterator. The returned slice has at most `chunk_size-1`
3854 pub fn remainder(&self) -> &'a [T] {
3859 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3860 #[unstable(feature = "chunks_exact", issue = "47115")]
3861 impl<T> Clone for ChunksExact<'_, T> {
3862 fn clone(&self) -> Self {
3866 chunk_size: self.chunk_size,
3871 #[unstable(feature = "chunks_exact", issue = "47115")]
3872 impl<'a, T> Iterator for ChunksExact<'a, T> {
3873 type Item = &'a [T];
3876 fn next(&mut self) -> Option<&'a [T]> {
3877 if self.v.len() < self.chunk_size {
3880 let (fst, snd) = self.v.split_at(self.chunk_size);
3887 fn size_hint(&self) -> (usize, Option<usize>) {
3888 let n = self.v.len() / self.chunk_size;
3893 fn count(self) -> usize {
3898 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3899 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3900 if start >= self.v.len() || overflow {
3904 let (_, snd) = self.v.split_at(start);
3911 fn last(mut self) -> Option<Self::Item> {
3916 #[unstable(feature = "chunks_exact", issue = "47115")]
3917 impl<'a, T> DoubleEndedIterator for ChunksExact<'a, T> {
3919 fn next_back(&mut self) -> Option<&'a [T]> {
3920 if self.v.len() < self.chunk_size {
3923 let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size);
3930 #[unstable(feature = "chunks_exact", issue = "47115")]
3931 impl<T> ExactSizeIterator for ChunksExact<'_, T> {
3932 fn is_empty(&self) -> bool {
3937 #[unstable(feature = "trusted_len", issue = "37572")]
3938 unsafe impl<T> TrustedLen for ChunksExact<'_, T> {}
3940 #[unstable(feature = "chunks_exact", issue = "47115")]
3941 impl<T> FusedIterator for ChunksExact<'_, T> {}
3944 unsafe impl<'a, T> TrustedRandomAccess for ChunksExact<'a, T> {
3945 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3946 let start = i * self.chunk_size;
3947 from_raw_parts(self.v.as_ptr().add(start), self.chunk_size)
3949 fn may_have_side_effect() -> bool { false }
3952 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3953 /// elements at a time).
3955 /// When the slice len is not evenly divided by the chunk size, the last up to
3956 /// `chunk_size-1` elements will be omitted but can be retrieved from the
3957 /// [`into_remainder`] function from the iterator.
3959 /// This struct is created by the [`chunks_exact_mut`] method on [slices].
3961 /// [`chunks_exact_mut`]: ../../std/primitive.slice.html#method.chunks_exact_mut
3962 /// [`into_remainder`]: ../../std/slice/struct.ChunksExactMut.html#method.into_remainder
3963 /// [slices]: ../../std/primitive.slice.html
3965 #[unstable(feature = "chunks_exact", issue = "47115")]
3966 pub struct ChunksExactMut<'a, T:'a> {
3972 #[unstable(feature = "chunks_exact", issue = "47115")]
3973 impl<'a, T> ChunksExactMut<'a, T> {
3974 /// Return the remainder of the original slice that is not going to be
3975 /// returned by the iterator. The returned slice has at most `chunk_size-1`
3977 pub fn into_remainder(self) -> &'a mut [T] {
3982 #[unstable(feature = "chunks_exact", issue = "47115")]
3983 impl<'a, T> Iterator for ChunksExactMut<'a, T> {
3984 type Item = &'a mut [T];
3987 fn next(&mut self) -> Option<&'a mut [T]> {
3988 if self.v.len() < self.chunk_size {
3991 let tmp = mem::replace(&mut self.v, &mut []);
3992 let (head, tail) = tmp.split_at_mut(self.chunk_size);
3999 fn size_hint(&self) -> (usize, Option<usize>) {
4000 let n = self.v.len() / self.chunk_size;
4005 fn count(self) -> usize {
4010 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
4011 let (start, overflow) = n.overflowing_mul(self.chunk_size);
4012 if start >= self.v.len() || overflow {
4016 let tmp = mem::replace(&mut self.v, &mut []);
4017 let (_, snd) = tmp.split_at_mut(start);
4024 fn last(mut self) -> Option<Self::Item> {
4029 #[unstable(feature = "chunks_exact", issue = "47115")]
4030 impl<'a, T> DoubleEndedIterator for ChunksExactMut<'a, T> {
4032 fn next_back(&mut self) -> Option<&'a mut [T]> {
4033 if self.v.len() < self.chunk_size {
4036 let tmp = mem::replace(&mut self.v, &mut []);
4037 let tmp_len = tmp.len();
4038 let (head, tail) = tmp.split_at_mut(tmp_len - self.chunk_size);
4045 #[unstable(feature = "chunks_exact", issue = "47115")]
4046 impl<T> ExactSizeIterator for ChunksExactMut<'_, T> {
4047 fn is_empty(&self) -> bool {
4052 #[unstable(feature = "trusted_len", issue = "37572")]
4053 unsafe impl<T> TrustedLen for ChunksExactMut<'_, T> {}
4055 #[unstable(feature = "chunks_exact", issue = "47115")]
4056 impl<T> FusedIterator for ChunksExactMut<'_, T> {}
4059 unsafe impl<'a, T> TrustedRandomAccess for ChunksExactMut<'a, T> {
4060 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
4061 let start = i * self.chunk_size;
4062 from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size)
4064 fn may_have_side_effect() -> bool { false }
4071 /// Forms a slice from a pointer and a length.
4073 /// The `len` argument is the number of **elements**, not the number of bytes.
4077 /// This function is unsafe as there is no guarantee that the given pointer is
4078 /// valid for `len` elements, nor whether the lifetime inferred is a suitable
4079 /// lifetime for the returned slice.
4081 /// `data` must be non-null and aligned, even for zero-length slices. One
4082 /// reason for this is that enum layout optimizations may rely on references
4083 /// (including slices of any length) being aligned and non-null to distinguish
4084 /// them from other data. You can obtain a pointer that is usable as `data`
4085 /// for zero-length slices using [`NonNull::dangling()`].
4087 /// The total size of the slice must be no larger than `isize::MAX` **bytes**
4088 /// in memory. See the safety documentation of [`pointer::offset`].
4092 /// The lifetime for the returned slice is inferred from its usage. To
4093 /// prevent accidental misuse, it's suggested to tie the lifetime to whichever
4094 /// source lifetime is safe in the context, such as by providing a helper
4095 /// function taking the lifetime of a host value for the slice, or by explicit
4103 /// // manifest a slice for a single element
4105 /// let ptr = &x as *const _;
4106 /// let slice = unsafe { slice::from_raw_parts(ptr, 1) };
4107 /// assert_eq!(slice[0], 42);
4110 /// [`NonNull::dangling()`]: ../../std/ptr/struct.NonNull.html#method.dangling
4111 /// [`pointer::offset`]: ../../std/primitive.pointer.html#method.offset
4113 #[stable(feature = "rust1", since = "1.0.0")]
4114 pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
4115 debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
4116 debug_assert!(mem::size_of::<T>().saturating_mul(len) <= isize::MAX as usize,
4117 "attempt to create slice covering half the address space");
4118 Repr { raw: FatPtr { data, len } }.rust
4121 /// Performs the same functionality as [`from_raw_parts`], except that a
4122 /// mutable slice is returned.
4124 /// This function is unsafe for the same reasons as [`from_raw_parts`], as well
4125 /// as not being able to provide a non-aliasing guarantee of the returned
4126 /// mutable slice. `data` must be non-null and aligned even for zero-length
4127 /// slices as with [`from_raw_parts`]. The total size of the slice must be no
4128 /// larger than `isize::MAX` **bytes** in memory.
4130 /// See the documentation of [`from_raw_parts`] for more details.
4132 /// [`from_raw_parts`]: ../../std/slice/fn.from_raw_parts.html
4134 #[stable(feature = "rust1", since = "1.0.0")]
4135 pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] {
4136 debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
4137 debug_assert!(mem::size_of::<T>().saturating_mul(len) <= isize::MAX as usize,
4138 "attempt to create slice covering half the address space");
4139 Repr { raw: FatPtr { data, len } }.rust_mut
4142 /// Converts a reference to T into a slice of length 1 (without copying).
4143 #[stable(feature = "from_ref", since = "1.28.0")]
4144 pub fn from_ref<T>(s: &T) -> &[T] {
4146 from_raw_parts(s, 1)
4150 /// Converts a reference to T into a slice of length 1 (without copying).
4151 #[stable(feature = "from_ref", since = "1.28.0")]
4152 pub fn from_mut<T>(s: &mut T) -> &mut [T] {
4154 from_raw_parts_mut(s, 1)
4158 // This function is public only because there is no other way to unit test heapsort.
4159 #[unstable(feature = "sort_internals", reason = "internal to sort module", issue = "0")]
4161 pub fn heapsort<T, F>(v: &mut [T], mut is_less: F)
4162 where F: FnMut(&T, &T) -> bool
4164 sort::heapsort(v, &mut is_less);
4168 // Comparison traits
4172 /// Calls implementation provided memcmp.
4174 /// Interprets the data as u8.
4176 /// Returns 0 for equal, < 0 for less than and > 0 for greater
4178 // FIXME(#32610): Return type should be c_int
4179 fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32;
4182 #[stable(feature = "rust1", since = "1.0.0")]
4183 impl<A, B> PartialEq<[B]> for [A] where A: PartialEq<B> {
4184 fn eq(&self, other: &[B]) -> bool {
4185 SlicePartialEq::equal(self, other)
4188 fn ne(&self, other: &[B]) -> bool {
4189 SlicePartialEq::not_equal(self, other)
4193 #[stable(feature = "rust1", since = "1.0.0")]
4194 impl<T: Eq> Eq for [T] {}
4196 /// Implements comparison of vectors lexicographically.
4197 #[stable(feature = "rust1", since = "1.0.0")]
4198 impl<T: Ord> Ord for [T] {
4199 fn cmp(&self, other: &[T]) -> Ordering {
4200 SliceOrd::compare(self, other)
4204 /// Implements comparison of vectors lexicographically.
4205 #[stable(feature = "rust1", since = "1.0.0")]
4206 impl<T: PartialOrd> PartialOrd for [T] {
4207 fn partial_cmp(&self, other: &[T]) -> Option<Ordering> {
4208 SlicePartialOrd::partial_compare(self, other)
4213 // intermediate trait for specialization of slice's PartialEq
4214 trait SlicePartialEq<B> {
4215 fn equal(&self, other: &[B]) -> bool;
4217 fn not_equal(&self, other: &[B]) -> bool { !self.equal(other) }
4220 // Generic slice equality
4221 impl<A, B> SlicePartialEq<B> for [A]
4222 where A: PartialEq<B>
4224 default fn equal(&self, other: &[B]) -> bool {
4225 if self.len() != other.len() {
4229 for i in 0..self.len() {
4230 if !self[i].eq(&other[i]) {
4239 // Use memcmp for bytewise equality when the types allow
4240 impl<A> SlicePartialEq<A> for [A]
4241 where A: PartialEq<A> + BytewiseEquality
4243 fn equal(&self, other: &[A]) -> bool {
4244 if self.len() != other.len() {
4247 if self.as_ptr() == other.as_ptr() {
4251 let size = mem::size_of_val(self);
4252 memcmp(self.as_ptr() as *const u8,
4253 other.as_ptr() as *const u8, size) == 0
4259 // intermediate trait for specialization of slice's PartialOrd
4260 trait SlicePartialOrd<B> {
4261 fn partial_compare(&self, other: &[B]) -> Option<Ordering>;
4264 impl<A> SlicePartialOrd<A> for [A]
4267 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
4268 let l = cmp::min(self.len(), other.len());
4270 // Slice to the loop iteration range to enable bound check
4271 // elimination in the compiler
4272 let lhs = &self[..l];
4273 let rhs = &other[..l];
4276 match lhs[i].partial_cmp(&rhs[i]) {
4277 Some(Ordering::Equal) => (),
4278 non_eq => return non_eq,
4282 self.len().partial_cmp(&other.len())
4286 impl<A> SlicePartialOrd<A> for [A]
4289 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
4290 Some(SliceOrd::compare(self, other))
4295 // intermediate trait for specialization of slice's Ord
4297 fn compare(&self, other: &[B]) -> Ordering;
4300 impl<A> SliceOrd<A> for [A]
4303 default fn compare(&self, other: &[A]) -> Ordering {
4304 let l = cmp::min(self.len(), other.len());
4306 // Slice to the loop iteration range to enable bound check
4307 // elimination in the compiler
4308 let lhs = &self[..l];
4309 let rhs = &other[..l];
4312 match lhs[i].cmp(&rhs[i]) {
4313 Ordering::Equal => (),
4314 non_eq => return non_eq,
4318 self.len().cmp(&other.len())
4322 // memcmp compares a sequence of unsigned bytes lexicographically.
4323 // this matches the order we want for [u8], but no others (not even [i8]).
4324 impl SliceOrd<u8> for [u8] {
4326 fn compare(&self, other: &[u8]) -> Ordering {
4327 let order = unsafe {
4328 memcmp(self.as_ptr(), other.as_ptr(),
4329 cmp::min(self.len(), other.len()))
4332 self.len().cmp(&other.len())
4333 } else if order < 0 {
4342 /// Trait implemented for types that can be compared for equality using
4343 /// their bytewise representation
4344 trait BytewiseEquality { }
4346 macro_rules! impl_marker_for {
4347 ($traitname:ident, $($ty:ty)*) => {
4349 impl $traitname for $ty { }
4354 impl_marker_for!(BytewiseEquality,
4355 u8 i8 u16 i16 u32 i32 u64 i64 usize isize char bool);
4358 unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {
4359 unsafe fn get_unchecked(&mut self, i: usize) -> &'a T {
4362 fn may_have_side_effect() -> bool { false }
4366 unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> {
4367 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut T {
4368 &mut *self.ptr.add(i)
4370 fn may_have_side_effect() -> bool { false }
4373 trait SliceContains: Sized {
4374 fn slice_contains(&self, x: &[Self]) -> bool;
4377 impl<T> SliceContains for T where T: PartialEq {
4378 default fn slice_contains(&self, x: &[Self]) -> bool {
4379 x.iter().any(|y| *y == *self)
4383 impl SliceContains for u8 {
4384 fn slice_contains(&self, x: &[Self]) -> bool {
4385 memchr::memchr(*self, x).is_some()
4389 impl SliceContains for i8 {
4390 fn slice_contains(&self, x: &[Self]) -> bool {
4391 let byte = *self as u8;
4392 let bytes: &[u8] = unsafe { from_raw_parts(x.as_ptr() as *const u8, x.len()) };
4393 memchr::memchr(byte, bytes).is_some()