1 //! Slice management and manipulation.
3 //! For more details see [`std::slice`].
5 //! [`std::slice`]: ../../std/slice/index.html
7 #![stable(feature = "rust1", since = "1.0.0")]
9 // How this module is organized.
11 // The library infrastructure for slices is fairly messy. There's
12 // a lot of stuff defined here. Let's keep it clean.
14 // The layout of this file is thus:
16 // * Inherent methods. This is where most of the slice API resides.
17 // * Implementations of a few common traits with important slice ops.
18 // * Definitions of a bunch of iterators.
20 // * The `raw` and `bytes` submodules.
21 // * Boilerplate trait implementations.
23 use crate::cmp::Ordering::{self, Less, Equal, Greater};
26 use crate::intrinsics::assume;
29 use crate::ops::{FnMut, Try, self};
30 use crate::option::Option;
31 use crate::option::Option::{None, Some};
32 use crate::result::Result;
33 use crate::result::Result::{Ok, Err};
36 use crate::marker::{Copy, Send, Sync, Sized, self};
38 #[unstable(feature = "slice_internals", issue = "0",
39 reason = "exposed from core to be reused in std; use the memchr crate")]
40 /// Pure rust memchr implementation, taken from rust-memchr
47 union Repr<'a, T: 'a> {
49 rust_mut: &'a mut [T],
66 /// Returns the number of elements in the slice.
71 /// let a = [1, 2, 3];
72 /// assert_eq!(a.len(), 3);
74 #[stable(feature = "rust1", since = "1.0.0")]
76 #[rustc_const_unstable(feature = "const_slice_len")]
77 pub const fn len(&self) -> usize {
79 Repr { rust: self }.raw.len
83 /// Returns `true` if the slice has a length of 0.
88 /// let a = [1, 2, 3];
89 /// assert!(!a.is_empty());
91 #[stable(feature = "rust1", since = "1.0.0")]
93 #[rustc_const_unstable(feature = "const_slice_len")]
94 pub const fn is_empty(&self) -> bool {
98 /// Returns the first element of the slice, or `None` if it is empty.
103 /// let v = [10, 40, 30];
104 /// assert_eq!(Some(&10), v.first());
106 /// let w: &[i32] = &[];
107 /// assert_eq!(None, w.first());
109 #[stable(feature = "rust1", since = "1.0.0")]
111 pub fn first(&self) -> Option<&T> {
115 /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
120 /// let x = &mut [0, 1, 2];
122 /// if let Some(first) = x.first_mut() {
125 /// assert_eq!(x, &[5, 1, 2]);
127 #[stable(feature = "rust1", since = "1.0.0")]
129 pub fn first_mut(&mut self) -> Option<&mut T> {
133 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
138 /// let x = &[0, 1, 2];
140 /// if let Some((first, elements)) = x.split_first() {
141 /// assert_eq!(first, &0);
142 /// assert_eq!(elements, &[1, 2]);
145 #[stable(feature = "slice_splits", since = "1.5.0")]
147 pub fn split_first(&self) -> Option<(&T, &[T])> {
148 if self.is_empty() { None } else { Some((&self[0], &self[1..])) }
151 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
156 /// let x = &mut [0, 1, 2];
158 /// if let Some((first, elements)) = x.split_first_mut() {
163 /// assert_eq!(x, &[3, 4, 5]);
165 #[stable(feature = "slice_splits", since = "1.5.0")]
167 pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
168 if self.is_empty() { None } else {
169 let split = self.split_at_mut(1);
170 Some((&mut split.0[0], split.1))
174 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
179 /// let x = &[0, 1, 2];
181 /// if let Some((last, elements)) = x.split_last() {
182 /// assert_eq!(last, &2);
183 /// assert_eq!(elements, &[0, 1]);
186 #[stable(feature = "slice_splits", since = "1.5.0")]
188 pub fn split_last(&self) -> Option<(&T, &[T])> {
189 let len = self.len();
190 if len == 0 { None } else { Some((&self[len - 1], &self[..(len - 1)])) }
193 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
198 /// let x = &mut [0, 1, 2];
200 /// if let Some((last, elements)) = x.split_last_mut() {
205 /// assert_eq!(x, &[4, 5, 3]);
207 #[stable(feature = "slice_splits", since = "1.5.0")]
209 pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
210 let len = self.len();
211 if len == 0 { None } else {
212 let split = self.split_at_mut(len - 1);
213 Some((&mut split.1[0], split.0))
218 /// Returns the last element of the slice, or `None` if it is empty.
223 /// let v = [10, 40, 30];
224 /// assert_eq!(Some(&30), v.last());
226 /// let w: &[i32] = &[];
227 /// assert_eq!(None, w.last());
229 #[stable(feature = "rust1", since = "1.0.0")]
231 pub fn last(&self) -> Option<&T> {
232 let last_idx = self.len().checked_sub(1)?;
236 /// Returns a mutable pointer to the last item in the slice.
241 /// let x = &mut [0, 1, 2];
243 /// if let Some(last) = x.last_mut() {
246 /// assert_eq!(x, &[0, 1, 10]);
248 #[stable(feature = "rust1", since = "1.0.0")]
250 pub fn last_mut(&mut self) -> Option<&mut T> {
251 let last_idx = self.len().checked_sub(1)?;
252 self.get_mut(last_idx)
255 /// Returns a reference to an element or subslice depending on the type of
258 /// - If given a position, returns a reference to the element at that
259 /// position or `None` if out of bounds.
260 /// - If given a range, returns the subslice corresponding to that range,
261 /// or `None` if out of bounds.
266 /// let v = [10, 40, 30];
267 /// assert_eq!(Some(&40), v.get(1));
268 /// assert_eq!(Some(&[10, 40][..]), v.get(0..2));
269 /// assert_eq!(None, v.get(3));
270 /// assert_eq!(None, v.get(0..4));
272 #[stable(feature = "rust1", since = "1.0.0")]
274 pub fn get<I>(&self, index: I) -> Option<&I::Output>
275 where I: SliceIndex<Self>
280 /// Returns a mutable reference to an element or subslice depending on the
281 /// type of index (see [`get`]) or `None` if the index is out of bounds.
283 /// [`get`]: #method.get
288 /// let x = &mut [0, 1, 2];
290 /// if let Some(elem) = x.get_mut(1) {
293 /// assert_eq!(x, &[0, 42, 2]);
295 #[stable(feature = "rust1", since = "1.0.0")]
297 pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output>
298 where I: SliceIndex<Self>
303 /// Returns a reference to an element or subslice, without doing bounds
306 /// This is generally not recommended, use with caution! For a safe
307 /// alternative see [`get`].
309 /// [`get`]: #method.get
314 /// let x = &[1, 2, 4];
317 /// assert_eq!(x.get_unchecked(1), &2);
320 #[stable(feature = "rust1", since = "1.0.0")]
322 pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output
323 where I: SliceIndex<Self>
325 index.get_unchecked(self)
328 /// Returns a mutable reference to an element or subslice, without doing
331 /// This is generally not recommended, use with caution! For a safe
332 /// alternative see [`get_mut`].
334 /// [`get_mut`]: #method.get_mut
339 /// let x = &mut [1, 2, 4];
342 /// let elem = x.get_unchecked_mut(1);
345 /// assert_eq!(x, &[1, 13, 4]);
347 #[stable(feature = "rust1", since = "1.0.0")]
349 pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
350 where I: SliceIndex<Self>
352 index.get_unchecked_mut(self)
355 /// Returns a raw pointer to the slice's buffer.
357 /// The caller must ensure that the slice outlives the pointer this
358 /// function returns, or else it will end up pointing to garbage.
360 /// Modifying the container referenced by this slice may cause its buffer
361 /// to be reallocated, which would also make any pointers to it invalid.
366 /// let x = &[1, 2, 4];
367 /// let x_ptr = x.as_ptr();
370 /// for i in 0..x.len() {
371 /// assert_eq!(x.get_unchecked(i), &*x_ptr.add(i));
375 #[stable(feature = "rust1", since = "1.0.0")]
377 pub const fn as_ptr(&self) -> *const T {
378 self as *const [T] as *const T
381 /// Returns an unsafe mutable pointer to the slice's buffer.
383 /// The caller must ensure that the slice outlives the pointer this
384 /// function returns, or else it will end up pointing to garbage.
386 /// Modifying the container referenced by this slice may cause its buffer
387 /// to be reallocated, which would also make any pointers to it invalid.
392 /// let x = &mut [1, 2, 4];
393 /// let x_ptr = x.as_mut_ptr();
396 /// for i in 0..x.len() {
397 /// *x_ptr.add(i) += 2;
400 /// assert_eq!(x, &[3, 4, 6]);
402 #[stable(feature = "rust1", since = "1.0.0")]
404 pub fn as_mut_ptr(&mut self) -> *mut T {
405 self as *mut [T] as *mut T
408 /// Swaps two elements in the slice.
412 /// * a - The index of the first element
413 /// * b - The index of the second element
417 /// Panics if `a` or `b` are out of bounds.
422 /// let mut v = ["a", "b", "c", "d"];
424 /// assert!(v == ["a", "d", "c", "b"]);
426 #[stable(feature = "rust1", since = "1.0.0")]
428 pub fn swap(&mut self, a: usize, b: usize) {
430 // Can't take two mutable loans from one vector, so instead just cast
431 // them to their raw pointers to do the swap
432 let pa: *mut T = &mut self[a];
433 let pb: *mut T = &mut self[b];
438 /// Reverses the order of elements in the slice, in place.
443 /// let mut v = [1, 2, 3];
445 /// assert!(v == [3, 2, 1]);
447 #[stable(feature = "rust1", since = "1.0.0")]
449 pub fn reverse(&mut self) {
450 let mut i: usize = 0;
453 // For very small types, all the individual reads in the normal
454 // path perform poorly. We can do better, given efficient unaligned
455 // load/store, by loading a larger chunk and reversing a register.
457 // Ideally LLVM would do this for us, as it knows better than we do
458 // whether unaligned reads are efficient (since that changes between
459 // different ARM versions, for example) and what the best chunk size
460 // would be. Unfortunately, as of LLVM 4.0 (2017-05) it only unrolls
461 // the loop, so we need to do this ourselves. (Hypothesis: reverse
462 // is troublesome because the sides can be aligned differently --
463 // will be, when the length is odd -- so there's no way of emitting
464 // pre- and postludes to use fully-aligned SIMD in the middle.)
467 cfg!(any(target_arch = "x86", target_arch = "x86_64"));
469 if fast_unaligned && mem::size_of::<T>() == 1 {
470 // Use the llvm.bswap intrinsic to reverse u8s in a usize
471 let chunk = mem::size_of::<usize>();
472 while i + chunk - 1 < ln / 2 {
474 let pa: *mut T = self.get_unchecked_mut(i);
475 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
476 let va = ptr::read_unaligned(pa as *mut usize);
477 let vb = ptr::read_unaligned(pb as *mut usize);
478 ptr::write_unaligned(pa as *mut usize, vb.swap_bytes());
479 ptr::write_unaligned(pb as *mut usize, va.swap_bytes());
485 if fast_unaligned && mem::size_of::<T>() == 2 {
486 // Use rotate-by-16 to reverse u16s in a u32
487 let chunk = mem::size_of::<u32>() / 2;
488 while i + chunk - 1 < ln / 2 {
490 let pa: *mut T = self.get_unchecked_mut(i);
491 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
492 let va = ptr::read_unaligned(pa as *mut u32);
493 let vb = ptr::read_unaligned(pb as *mut u32);
494 ptr::write_unaligned(pa as *mut u32, vb.rotate_left(16));
495 ptr::write_unaligned(pb as *mut u32, va.rotate_left(16));
502 // Unsafe swap to avoid the bounds check in safe swap.
504 let pa: *mut T = self.get_unchecked_mut(i);
505 let pb: *mut T = self.get_unchecked_mut(ln - i - 1);
512 /// Returns an iterator over the slice.
517 /// let x = &[1, 2, 4];
518 /// let mut iterator = x.iter();
520 /// assert_eq!(iterator.next(), Some(&1));
521 /// assert_eq!(iterator.next(), Some(&2));
522 /// assert_eq!(iterator.next(), Some(&4));
523 /// assert_eq!(iterator.next(), None);
525 #[stable(feature = "rust1", since = "1.0.0")]
527 pub fn iter(&self) -> Iter<'_, T> {
529 let ptr = self.as_ptr();
530 assume(!ptr.is_null());
532 let end = if mem::size_of::<T>() == 0 {
533 (ptr as *const u8).wrapping_add(self.len()) as *const T
541 _marker: marker::PhantomData
546 /// Returns an iterator that allows modifying each value.
551 /// let x = &mut [1, 2, 4];
552 /// for elem in x.iter_mut() {
555 /// assert_eq!(x, &[3, 4, 6]);
557 #[stable(feature = "rust1", since = "1.0.0")]
559 pub fn iter_mut(&mut self) -> IterMut<'_, T> {
561 let ptr = self.as_mut_ptr();
562 assume(!ptr.is_null());
564 let end = if mem::size_of::<T>() == 0 {
565 (ptr as *mut u8).wrapping_add(self.len()) as *mut T
573 _marker: marker::PhantomData
578 /// Returns an iterator over all contiguous windows of length
579 /// `size`. The windows overlap. If the slice is shorter than
580 /// `size`, the iterator returns no values.
584 /// Panics if `size` is 0.
589 /// let slice = ['r', 'u', 's', 't'];
590 /// let mut iter = slice.windows(2);
591 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
592 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
593 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
594 /// assert!(iter.next().is_none());
597 /// If the slice is shorter than `size`:
600 /// let slice = ['f', 'o', 'o'];
601 /// let mut iter = slice.windows(4);
602 /// assert!(iter.next().is_none());
604 #[stable(feature = "rust1", since = "1.0.0")]
606 pub fn windows(&self, size: usize) -> Windows<'_, T> {
608 Windows { v: self, size }
611 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
612 /// beginning of the slice.
614 /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the
615 /// slice, then the last chunk will not have length `chunk_size`.
617 /// See [`chunks_exact`] for a variant of this iterator that returns chunks of always exactly
618 /// `chunk_size` elements, and [`rchunks`] for the same iterator but starting at the end of the
619 /// slice of the slice.
623 /// Panics if `chunk_size` is 0.
628 /// let slice = ['l', 'o', 'r', 'e', 'm'];
629 /// let mut iter = slice.chunks(2);
630 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
631 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
632 /// assert_eq!(iter.next().unwrap(), &['m']);
633 /// assert!(iter.next().is_none());
636 /// [`chunks_exact`]: #method.chunks_exact
637 /// [`rchunks`]: #method.rchunks
638 #[stable(feature = "rust1", since = "1.0.0")]
640 pub fn chunks(&self, chunk_size: usize) -> Chunks<'_, T> {
641 assert!(chunk_size != 0);
642 Chunks { v: self, chunk_size }
645 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
646 /// beginning of the slice.
648 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the
649 /// length of the slice, then the last chunk will not have length `chunk_size`.
651 /// See [`chunks_exact_mut`] for a variant of this iterator that returns chunks of always
652 /// exactly `chunk_size` elements, and [`rchunks_mut`] for the same iterator but starting at
653 /// the end of the slice of the slice.
657 /// Panics if `chunk_size` is 0.
662 /// let v = &mut [0, 0, 0, 0, 0];
663 /// let mut count = 1;
665 /// for chunk in v.chunks_mut(2) {
666 /// for elem in chunk.iter_mut() {
671 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
674 /// [`chunks_exact_mut`]: #method.chunks_exact_mut
675 /// [`rchunks_mut`]: #method.rchunks_mut
676 #[stable(feature = "rust1", since = "1.0.0")]
678 pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<'_, T> {
679 assert!(chunk_size != 0);
680 ChunksMut { v: self, chunk_size }
683 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
684 /// beginning of the slice.
686 /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the
687 /// slice, then the last up to `chunk_size-1` elements will be omitted and can be retrieved
688 /// from the `remainder` function of the iterator.
690 /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the
691 /// resulting code better than in the case of [`chunks`].
693 /// See [`chunks`] for a variant of this iterator that also returns the remainder as a smaller
694 /// chunk, and [`rchunks_exact`] for the same iterator but starting at the end of the slice.
698 /// Panics if `chunk_size` is 0.
703 /// let slice = ['l', 'o', 'r', 'e', 'm'];
704 /// let mut iter = slice.chunks_exact(2);
705 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
706 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
707 /// assert!(iter.next().is_none());
708 /// assert_eq!(iter.remainder(), &['m']);
711 /// [`chunks`]: #method.chunks
712 /// [`rchunks_exact`]: #method.rchunks_exact
713 #[stable(feature = "chunks_exact", since = "1.31.0")]
715 pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, T> {
716 assert!(chunk_size != 0);
717 let rem = self.len() % chunk_size;
718 let len = self.len() - rem;
719 let (fst, snd) = self.split_at(len);
720 ChunksExact { v: fst, rem: snd, chunk_size }
723 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
724 /// beginning of the slice.
726 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the
727 /// length of the slice, then the last up to `chunk_size-1` elements will be omitted and can be
728 /// retrieved from the `into_remainder` function of the iterator.
730 /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the
731 /// resulting code better than in the case of [`chunks_mut`].
733 /// See [`chunks_mut`] for a variant of this iterator that also returns the remainder as a
734 /// smaller chunk, and [`rchunks_exact_mut`] for the same iterator but starting at the end of
735 /// the slice of the slice.
739 /// Panics if `chunk_size` is 0.
744 /// let v = &mut [0, 0, 0, 0, 0];
745 /// let mut count = 1;
747 /// for chunk in v.chunks_exact_mut(2) {
748 /// for elem in chunk.iter_mut() {
753 /// assert_eq!(v, &[1, 1, 2, 2, 0]);
756 /// [`chunks_mut`]: #method.chunks_mut
757 /// [`rchunks_exact_mut`]: #method.rchunks_exact_mut
758 #[stable(feature = "chunks_exact", since = "1.31.0")]
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 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end
771 /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the
772 /// slice, then the last chunk will not have length `chunk_size`.
774 /// See [`rchunks_exact`] for a variant of this iterator that returns chunks of always exactly
775 /// `chunk_size` elements, and [`chunks`] for the same iterator but starting at the beginning
780 /// Panics if `chunk_size` is 0.
785 /// let slice = ['l', 'o', 'r', 'e', 'm'];
786 /// let mut iter = slice.rchunks(2);
787 /// assert_eq!(iter.next().unwrap(), &['e', 'm']);
788 /// assert_eq!(iter.next().unwrap(), &['o', 'r']);
789 /// assert_eq!(iter.next().unwrap(), &['l']);
790 /// assert!(iter.next().is_none());
793 /// [`rchunks_exact`]: #method.rchunks_exact
794 /// [`chunks`]: #method.chunks
795 #[stable(feature = "rchunks", since = "1.31.0")]
797 pub fn rchunks(&self, chunk_size: usize) -> RChunks<'_, T> {
798 assert!(chunk_size != 0);
799 RChunks { v: self, chunk_size }
802 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end
805 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the
806 /// length of the slice, then the last chunk will not have length `chunk_size`.
808 /// See [`rchunks_exact_mut`] for a variant of this iterator that returns chunks of always
809 /// exactly `chunk_size` elements, and [`chunks_mut`] for the same iterator but starting at the
810 /// beginning of the slice.
814 /// Panics if `chunk_size` is 0.
819 /// let v = &mut [0, 0, 0, 0, 0];
820 /// let mut count = 1;
822 /// for chunk in v.rchunks_mut(2) {
823 /// for elem in chunk.iter_mut() {
828 /// assert_eq!(v, &[3, 2, 2, 1, 1]);
831 /// [`rchunks_exact_mut`]: #method.rchunks_exact_mut
832 /// [`chunks_mut`]: #method.chunks_mut
833 #[stable(feature = "rchunks", since = "1.31.0")]
835 pub fn rchunks_mut(&mut self, chunk_size: usize) -> RChunksMut<'_, T> {
836 assert!(chunk_size != 0);
837 RChunksMut { v: self, chunk_size }
840 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the
841 /// end of the slice.
843 /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the
844 /// slice, then the last up to `chunk_size-1` elements will be omitted and can be retrieved
845 /// from the `remainder` function of the iterator.
847 /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the
848 /// resulting code better than in the case of [`chunks`].
850 /// See [`rchunks`] for a variant of this iterator that also returns the remainder as a smaller
851 /// chunk, and [`chunks_exact`] for the same iterator but starting at the beginning of the
856 /// Panics if `chunk_size` is 0.
861 /// let slice = ['l', 'o', 'r', 'e', 'm'];
862 /// let mut iter = slice.rchunks_exact(2);
863 /// assert_eq!(iter.next().unwrap(), &['e', 'm']);
864 /// assert_eq!(iter.next().unwrap(), &['o', 'r']);
865 /// assert!(iter.next().is_none());
866 /// assert_eq!(iter.remainder(), &['l']);
869 /// [`chunks`]: #method.chunks
870 /// [`rchunks`]: #method.rchunks
871 /// [`chunks_exact`]: #method.chunks_exact
872 #[stable(feature = "rchunks", since = "1.31.0")]
874 pub fn rchunks_exact(&self, chunk_size: usize) -> RChunksExact<'_, T> {
875 assert!(chunk_size != 0);
876 let rem = self.len() % chunk_size;
877 let (fst, snd) = self.split_at(rem);
878 RChunksExact { v: snd, rem: fst, chunk_size }
881 /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end
884 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does not divide the
885 /// length of the slice, then the last up to `chunk_size-1` elements will be omitted and can be
886 /// retrieved from the `into_remainder` function of the iterator.
888 /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the
889 /// resulting code better than in the case of [`chunks_mut`].
891 /// See [`rchunks_mut`] for a variant of this iterator that also returns the remainder as a
892 /// smaller chunk, and [`chunks_exact_mut`] for the same iterator but starting at the beginning
897 /// Panics if `chunk_size` is 0.
902 /// let v = &mut [0, 0, 0, 0, 0];
903 /// let mut count = 1;
905 /// for chunk in v.rchunks_exact_mut(2) {
906 /// for elem in chunk.iter_mut() {
911 /// assert_eq!(v, &[0, 2, 2, 1, 1]);
914 /// [`chunks_mut`]: #method.chunks_mut
915 /// [`rchunks_mut`]: #method.rchunks_mut
916 /// [`chunks_exact_mut`]: #method.chunks_exact_mut
917 #[stable(feature = "rchunks", since = "1.31.0")]
919 pub fn rchunks_exact_mut(&mut self, chunk_size: usize) -> RChunksExactMut<'_, T> {
920 assert!(chunk_size != 0);
921 let rem = self.len() % chunk_size;
922 let (fst, snd) = self.split_at_mut(rem);
923 RChunksExactMut { v: snd, rem: fst, chunk_size }
926 /// Divides one slice into two at an index.
928 /// The first will contain all indices from `[0, mid)` (excluding
929 /// the index `mid` itself) and the second will contain all
930 /// indices from `[mid, len)` (excluding the index `len` itself).
934 /// Panics if `mid > len`.
939 /// let v = [1, 2, 3, 4, 5, 6];
942 /// let (left, right) = v.split_at(0);
943 /// assert!(left == []);
944 /// assert!(right == [1, 2, 3, 4, 5, 6]);
948 /// let (left, right) = v.split_at(2);
949 /// assert!(left == [1, 2]);
950 /// assert!(right == [3, 4, 5, 6]);
954 /// let (left, right) = v.split_at(6);
955 /// assert!(left == [1, 2, 3, 4, 5, 6]);
956 /// assert!(right == []);
959 #[stable(feature = "rust1", since = "1.0.0")]
961 pub fn split_at(&self, mid: usize) -> (&[T], &[T]) {
962 (&self[..mid], &self[mid..])
965 /// Divides one mutable slice into two at an index.
967 /// The first will contain all indices from `[0, mid)` (excluding
968 /// the index `mid` itself) and the second will contain all
969 /// indices from `[mid, len)` (excluding the index `len` itself).
973 /// Panics if `mid > len`.
978 /// let mut v = [1, 0, 3, 0, 5, 6];
979 /// // scoped to restrict the lifetime of the borrows
981 /// let (left, right) = v.split_at_mut(2);
982 /// assert!(left == [1, 0]);
983 /// assert!(right == [3, 0, 5, 6]);
987 /// assert!(v == [1, 2, 3, 4, 5, 6]);
989 #[stable(feature = "rust1", since = "1.0.0")]
991 pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
992 let len = self.len();
993 let ptr = self.as_mut_ptr();
998 (from_raw_parts_mut(ptr, mid),
999 from_raw_parts_mut(ptr.add(mid), len - mid))
1003 /// Returns an iterator over subslices separated by elements that match
1004 /// `pred`. The matched element is not contained in the subslices.
1009 /// let slice = [10, 40, 33, 20];
1010 /// let mut iter = slice.split(|num| num % 3 == 0);
1012 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
1013 /// assert_eq!(iter.next().unwrap(), &[20]);
1014 /// assert!(iter.next().is_none());
1017 /// If the first element is matched, an empty slice will be the first item
1018 /// returned by the iterator. Similarly, if the last element in the slice
1019 /// is matched, an empty slice will be the last item returned by the
1023 /// let slice = [10, 40, 33];
1024 /// let mut iter = slice.split(|num| num % 3 == 0);
1026 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
1027 /// assert_eq!(iter.next().unwrap(), &[]);
1028 /// assert!(iter.next().is_none());
1031 /// If two matched elements are directly adjacent, an empty slice will be
1032 /// present between them:
1035 /// let slice = [10, 6, 33, 20];
1036 /// let mut iter = slice.split(|num| num % 3 == 0);
1038 /// assert_eq!(iter.next().unwrap(), &[10]);
1039 /// assert_eq!(iter.next().unwrap(), &[]);
1040 /// assert_eq!(iter.next().unwrap(), &[20]);
1041 /// assert!(iter.next().is_none());
1043 #[stable(feature = "rust1", since = "1.0.0")]
1045 pub fn split<F>(&self, pred: F) -> Split<'_, T, F>
1046 where F: FnMut(&T) -> bool
1055 /// Returns an iterator over mutable subslices separated by elements that
1056 /// match `pred`. The matched element is not contained in the subslices.
1061 /// let mut v = [10, 40, 30, 20, 60, 50];
1063 /// for group in v.split_mut(|num| *num % 3 == 0) {
1066 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
1068 #[stable(feature = "rust1", since = "1.0.0")]
1070 pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<'_, T, F>
1071 where F: FnMut(&T) -> bool
1073 SplitMut { v: self, pred, finished: false }
1076 /// Returns an iterator over subslices separated by elements that match
1077 /// `pred`, starting at the end of the slice and working backwards.
1078 /// The matched element is not contained in the subslices.
1083 /// let slice = [11, 22, 33, 0, 44, 55];
1084 /// let mut iter = slice.rsplit(|num| *num == 0);
1086 /// assert_eq!(iter.next().unwrap(), &[44, 55]);
1087 /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
1088 /// assert_eq!(iter.next(), None);
1091 /// As with `split()`, if the first or last element is matched, an empty
1092 /// slice will be the first (or last) item returned by the iterator.
1095 /// let v = &[0, 1, 1, 2, 3, 5, 8];
1096 /// let mut it = v.rsplit(|n| *n % 2 == 0);
1097 /// assert_eq!(it.next().unwrap(), &[]);
1098 /// assert_eq!(it.next().unwrap(), &[3, 5]);
1099 /// assert_eq!(it.next().unwrap(), &[1, 1]);
1100 /// assert_eq!(it.next().unwrap(), &[]);
1101 /// assert_eq!(it.next(), None);
1103 #[stable(feature = "slice_rsplit", since = "1.27.0")]
1105 pub fn rsplit<F>(&self, pred: F) -> RSplit<'_, T, F>
1106 where F: FnMut(&T) -> bool
1108 RSplit { inner: self.split(pred) }
1111 /// Returns an iterator over mutable subslices separated by elements that
1112 /// match `pred`, starting at the end of the slice and working
1113 /// backwards. The matched element is not contained in the subslices.
1118 /// let mut v = [100, 400, 300, 200, 600, 500];
1120 /// let mut count = 0;
1121 /// for group in v.rsplit_mut(|num| *num % 3 == 0) {
1123 /// group[0] = count;
1125 /// assert_eq!(v, [3, 400, 300, 2, 600, 1]);
1128 #[stable(feature = "slice_rsplit", since = "1.27.0")]
1130 pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<'_, T, F>
1131 where F: FnMut(&T) -> bool
1133 RSplitMut { inner: self.split_mut(pred) }
1136 /// Returns an iterator over subslices separated by elements that match
1137 /// `pred`, limited to returning at most `n` items. The matched element is
1138 /// not contained in the subslices.
1140 /// The last element returned, if any, will contain the remainder of the
1145 /// Print the slice split once by numbers divisible by 3 (i.e., `[10, 40]`,
1146 /// `[20, 60, 50]`):
1149 /// let v = [10, 40, 30, 20, 60, 50];
1151 /// for group in v.splitn(2, |num| *num % 3 == 0) {
1152 /// println!("{:?}", group);
1155 #[stable(feature = "rust1", since = "1.0.0")]
1157 pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<'_, T, F>
1158 where F: FnMut(&T) -> bool
1161 inner: GenericSplitN {
1162 iter: self.split(pred),
1168 /// Returns an iterator over subslices separated by elements that match
1169 /// `pred`, limited to returning at most `n` items. The matched element is
1170 /// not contained in the subslices.
1172 /// The last element returned, if any, will contain the remainder of the
1178 /// let mut v = [10, 40, 30, 20, 60, 50];
1180 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
1183 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
1185 #[stable(feature = "rust1", since = "1.0.0")]
1187 pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<'_, T, F>
1188 where F: FnMut(&T) -> bool
1191 inner: GenericSplitN {
1192 iter: self.split_mut(pred),
1198 /// Returns an iterator over subslices separated by elements that match
1199 /// `pred` limited to returning at most `n` items. This starts at the end of
1200 /// the slice and works backwards. The matched element is not contained in
1203 /// The last element returned, if any, will contain the remainder of the
1208 /// Print the slice split once, starting from the end, by numbers divisible
1209 /// by 3 (i.e., `[50]`, `[10, 40, 30, 20]`):
1212 /// let v = [10, 40, 30, 20, 60, 50];
1214 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
1215 /// println!("{:?}", group);
1218 #[stable(feature = "rust1", since = "1.0.0")]
1220 pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<'_, T, F>
1221 where F: FnMut(&T) -> bool
1224 inner: GenericSplitN {
1225 iter: self.rsplit(pred),
1231 /// Returns an iterator over subslices separated by elements that match
1232 /// `pred` limited to returning at most `n` items. This starts at the end of
1233 /// the slice and works backwards. The matched element is not contained in
1236 /// The last element returned, if any, will contain the remainder of the
1242 /// let mut s = [10, 40, 30, 20, 60, 50];
1244 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
1247 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
1249 #[stable(feature = "rust1", since = "1.0.0")]
1251 pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<'_, T, F>
1252 where F: FnMut(&T) -> bool
1255 inner: GenericSplitN {
1256 iter: self.rsplit_mut(pred),
1262 /// Returns `true` if the slice contains an element with the given value.
1267 /// let v = [10, 40, 30];
1268 /// assert!(v.contains(&30));
1269 /// assert!(!v.contains(&50));
1271 #[stable(feature = "rust1", since = "1.0.0")]
1272 pub fn contains(&self, x: &T) -> bool
1275 x.slice_contains(self)
1278 /// Returns `true` if `needle` is a prefix of the slice.
1283 /// let v = [10, 40, 30];
1284 /// assert!(v.starts_with(&[10]));
1285 /// assert!(v.starts_with(&[10, 40]));
1286 /// assert!(!v.starts_with(&[50]));
1287 /// assert!(!v.starts_with(&[10, 50]));
1290 /// Always returns `true` if `needle` is an empty slice:
1293 /// let v = &[10, 40, 30];
1294 /// assert!(v.starts_with(&[]));
1295 /// let v: &[u8] = &[];
1296 /// assert!(v.starts_with(&[]));
1298 #[stable(feature = "rust1", since = "1.0.0")]
1299 pub fn starts_with(&self, needle: &[T]) -> bool
1302 let n = needle.len();
1303 self.len() >= n && needle == &self[..n]
1306 /// Returns `true` if `needle` is a suffix of the slice.
1311 /// let v = [10, 40, 30];
1312 /// assert!(v.ends_with(&[30]));
1313 /// assert!(v.ends_with(&[40, 30]));
1314 /// assert!(!v.ends_with(&[50]));
1315 /// assert!(!v.ends_with(&[50, 30]));
1318 /// Always returns `true` if `needle` is an empty slice:
1321 /// let v = &[10, 40, 30];
1322 /// assert!(v.ends_with(&[]));
1323 /// let v: &[u8] = &[];
1324 /// assert!(v.ends_with(&[]));
1326 #[stable(feature = "rust1", since = "1.0.0")]
1327 pub fn ends_with(&self, needle: &[T]) -> bool
1330 let (m, n) = (self.len(), needle.len());
1331 m >= n && needle == &self[m-n..]
1334 /// Binary searches this sorted slice for a given element.
1336 /// If the value is found then [`Result::Ok`] is returned, containing the
1337 /// index of the matching element. If there are multiple matches, then any
1338 /// one of the matches could be returned. If the value is not found then
1339 /// [`Result::Err`] is returned, containing the index where a matching
1340 /// element could be inserted while maintaining sorted order.
1344 /// Looks up a series of four elements. The first is found, with a
1345 /// uniquely determined position; the second and third are not
1346 /// found; the fourth could match any position in `[1, 4]`.
1349 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1351 /// assert_eq!(s.binary_search(&13), Ok(9));
1352 /// assert_eq!(s.binary_search(&4), Err(7));
1353 /// assert_eq!(s.binary_search(&100), Err(13));
1354 /// let r = s.binary_search(&1);
1355 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1357 #[stable(feature = "rust1", since = "1.0.0")]
1358 pub fn binary_search(&self, x: &T) -> Result<usize, usize>
1361 self.binary_search_by(|p| p.cmp(x))
1364 /// Binary searches this sorted slice with a comparator function.
1366 /// The comparator function should implement an order consistent
1367 /// with the sort order of the underlying slice, returning an
1368 /// order code that indicates whether its argument is `Less`,
1369 /// `Equal` or `Greater` the desired target.
1371 /// If the value is found then [`Result::Ok`] is returned, containing the
1372 /// index of the matching element. If there are multiple matches, then any
1373 /// one of the matches could be returned. If the value is not found then
1374 /// [`Result::Err`] is returned, containing the index where a matching
1375 /// element could be inserted while maintaining sorted order.
1379 /// Looks up a series of four elements. The first is found, with a
1380 /// uniquely determined position; the second and third are not
1381 /// found; the fourth could match any position in `[1, 4]`.
1384 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1387 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
1389 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
1391 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
1393 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
1394 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1396 #[stable(feature = "rust1", since = "1.0.0")]
1398 pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
1399 where F: FnMut(&'a T) -> Ordering
1402 let mut size = s.len();
1406 let mut base = 0usize;
1408 let half = size / 2;
1409 let mid = base + half;
1410 // mid is always in [0, size), that means mid is >= 0 and < size.
1411 // mid >= 0: by definition
1412 // mid < size: mid = size / 2 + size / 4 + size / 8 ...
1413 let cmp = f(unsafe { s.get_unchecked(mid) });
1414 base = if cmp == Greater { base } else { mid };
1417 // base is always in [0, size) because base <= mid.
1418 let cmp = f(unsafe { s.get_unchecked(base) });
1419 if cmp == Equal { Ok(base) } else { Err(base + (cmp == Less) as usize) }
1423 /// Binary searches this sorted slice with a key extraction function.
1425 /// Assumes that the slice is sorted by the key, for instance with
1426 /// [`sort_by_key`] using the same key extraction function.
1428 /// If the value is found then [`Result::Ok`] is returned, containing the
1429 /// index of the matching element. If there are multiple matches, then any
1430 /// one of the matches could be returned. If the value is not found then
1431 /// [`Result::Err`] is returned, containing the index where a matching
1432 /// element could be inserted while maintaining sorted order.
1434 /// [`sort_by_key`]: #method.sort_by_key
1438 /// Looks up a series of four elements in a slice of pairs sorted by
1439 /// their second elements. The first is found, with a uniquely
1440 /// determined position; the second and third are not found; the
1441 /// fourth could match any position in `[1, 4]`.
1444 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
1445 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
1446 /// (1, 21), (2, 34), (4, 55)];
1448 /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9));
1449 /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7));
1450 /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
1451 /// let r = s.binary_search_by_key(&1, |&(a,b)| b);
1452 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1454 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
1456 pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
1457 where F: FnMut(&'a T) -> B,
1460 self.binary_search_by(|k| f(k).cmp(b))
1463 /// Sorts the slice, but may not preserve the order of equal elements.
1465 /// This sort is unstable (i.e., may reorder equal elements), in-place
1466 /// (i.e., does not allocate), and `O(n log n)` worst-case.
1468 /// # Current implementation
1470 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1471 /// which combines the fast average case of randomized quicksort with the fast worst case of
1472 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1473 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1474 /// deterministic behavior.
1476 /// It is typically faster than stable sorting, except in a few special cases, e.g., when the
1477 /// slice consists of several concatenated sorted sequences.
1482 /// let mut v = [-5, 4, 1, -3, 2];
1484 /// v.sort_unstable();
1485 /// assert!(v == [-5, -3, 1, 2, 4]);
1488 /// [pdqsort]: https://github.com/orlp/pdqsort
1489 #[stable(feature = "sort_unstable", since = "1.20.0")]
1491 pub fn sort_unstable(&mut self)
1494 sort::quicksort(self, |a, b| a.lt(b));
1497 /// Sorts the slice with a comparator function, but may not preserve the order of equal
1500 /// This sort is unstable (i.e., may reorder equal elements), in-place
1501 /// (i.e., does not allocate), and `O(n log n)` worst-case.
1503 /// The comparator function must define a total ordering for the elements in the slice. If
1504 /// the ordering is not total, the order of the elements is unspecified. An order is a
1505 /// total order if it is (for all a, b and c):
1507 /// * total and antisymmetric: exactly one of a < b, a == b or a > b is true; and
1508 /// * transitive, a < b and b < c implies a < c. The same must hold for both == and >.
1510 /// For example, while [`f64`] doesn't implement [`Ord`] because `NaN != NaN`, we can use
1511 /// `partial_cmp` as our sort function when we know the slice doesn't contain a `NaN`.
1514 /// let mut floats = [5f64, 4.0, 1.0, 3.0, 2.0];
1515 /// floats.sort_by(|a, b| a.partial_cmp(b).unwrap());
1516 /// assert_eq!(floats, [1.0, 2.0, 3.0, 4.0, 5.0]);
1519 /// # Current implementation
1521 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1522 /// which combines the fast average case of randomized quicksort with the fast worst case of
1523 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1524 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1525 /// deterministic behavior.
1527 /// It is typically faster than stable sorting, except in a few special cases, e.g., when the
1528 /// slice consists of several concatenated sorted sequences.
1533 /// let mut v = [5, 4, 1, 3, 2];
1534 /// v.sort_unstable_by(|a, b| a.cmp(b));
1535 /// assert!(v == [1, 2, 3, 4, 5]);
1537 /// // reverse sorting
1538 /// v.sort_unstable_by(|a, b| b.cmp(a));
1539 /// assert!(v == [5, 4, 3, 2, 1]);
1542 /// [pdqsort]: https://github.com/orlp/pdqsort
1543 #[stable(feature = "sort_unstable", since = "1.20.0")]
1545 pub fn sort_unstable_by<F>(&mut self, mut compare: F)
1546 where F: FnMut(&T, &T) -> Ordering
1548 sort::quicksort(self, |a, b| compare(a, b) == Ordering::Less);
1551 /// Sorts the slice with a key extraction function, but may not preserve the order of equal
1554 /// This sort is unstable (i.e., may reorder equal elements), in-place
1555 /// (i.e., does not allocate), and `O(m n log(m n))` worst-case, where the key function is
1558 /// # Current implementation
1560 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1561 /// which combines the fast average case of randomized quicksort with the fast worst case of
1562 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1563 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1564 /// deterministic behavior.
1566 /// Due to its key calling strategy, [`sort_unstable_by_key`](#method.sort_unstable_by_key)
1567 /// is likely to be slower than [`sort_by_cached_key`](#method.sort_by_cached_key) in
1568 /// cases where the key function is expensive.
1573 /// let mut v = [-5i32, 4, 1, -3, 2];
1575 /// v.sort_unstable_by_key(|k| k.abs());
1576 /// assert!(v == [1, 2, -3, 4, -5]);
1579 /// [pdqsort]: https://github.com/orlp/pdqsort
1580 #[stable(feature = "sort_unstable", since = "1.20.0")]
1582 pub fn sort_unstable_by_key<K, F>(&mut self, mut f: F)
1583 where F: FnMut(&T) -> K, K: Ord
1585 sort::quicksort(self, |a, b| f(a).lt(&f(b)));
1588 /// Reorder the slice such that the element at `index` is at its final sorted position.
1590 /// This reordering has the additional property that any value at position `i < index` will be
1591 /// less than or equal to any value at a position `j > index`. Additionally, this reordering is
1592 /// unstable (i.e. any number of equal elements may end up at position `index`), in-place
1593 /// (i.e. does not allocate), and `O(n)` worst-case. This function is also/ known as "kth
1594 /// element" in other libraries. It returns a triplet of the following values: all elements less
1595 /// than the one at the given index, the value at the given index, and all elements greater than
1596 /// the one at the given index.
1598 /// # Current implementation
1600 /// The current algorithm is based on the quickselect portion of the same quicksort algorithm
1601 /// used for [`sort_unstable`].
1603 /// [`sort_unstable`]: #method.sort_unstable
1607 /// Panics when `index >= len()`, meaning it always panics on empty slices.
1612 /// #![feature(slice_partition_at_index)]
1614 /// let mut v = [-5i32, 4, 1, -3, 2];
1616 /// // Find the median
1617 /// v.partition_at_index(2);
1619 /// // We are only guaranteed the slice will be one of the following, based on the way we sort
1620 /// // about the specified index.
1621 /// assert!(v == [-3, -5, 1, 2, 4] ||
1622 /// v == [-5, -3, 1, 2, 4] ||
1623 /// v == [-3, -5, 1, 4, 2] ||
1624 /// v == [-5, -3, 1, 4, 2]);
1626 #[unstable(feature = "slice_partition_at_index", issue = "55300")]
1628 pub fn partition_at_index(&mut self, index: usize) -> (&mut [T], &mut T, &mut [T])
1631 let mut f = |a: &T, b: &T| a.lt(b);
1632 sort::partition_at_index(self, index, &mut f)
1635 /// Reorder the slice with a comparator function such that the element at `index` is at its
1636 /// final sorted position.
1638 /// This reordering has the additional property that any value at position `i < index` will be
1639 /// less than or equal to any value at a position `j > index` using the comparator function.
1640 /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at
1641 /// position `index`), in-place (i.e. does not allocate), and `O(n)` worst-case. This function
1642 /// is also known as "kth element" in other libraries. It returns a triplet of the following
1643 /// values: all elements less than the one at the given index, the value at the given index,
1644 /// and all elements greater than the one at the given index, using the provided comparator
1647 /// # Current implementation
1649 /// The current algorithm is based on the quickselect portion of the same quicksort algorithm
1650 /// used for [`sort_unstable`].
1652 /// [`sort_unstable`]: #method.sort_unstable
1656 /// Panics when `index >= len()`, meaning it always panics on empty slices.
1661 /// #![feature(slice_partition_at_index)]
1663 /// let mut v = [-5i32, 4, 1, -3, 2];
1665 /// // Find the median as if the slice were sorted in descending order.
1666 /// v.partition_at_index_by(2, |a, b| b.cmp(a));
1668 /// // We are only guaranteed the slice will be one of the following, based on the way we sort
1669 /// // about the specified index.
1670 /// assert!(v == [2, 4, 1, -5, -3] ||
1671 /// v == [2, 4, 1, -3, -5] ||
1672 /// v == [4, 2, 1, -5, -3] ||
1673 /// v == [4, 2, 1, -3, -5]);
1675 #[unstable(feature = "slice_partition_at_index", issue = "55300")]
1677 pub fn partition_at_index_by<F>(&mut self, index: usize, mut compare: F)
1678 -> (&mut [T], &mut T, &mut [T])
1679 where F: FnMut(&T, &T) -> Ordering
1681 let mut f = |a: &T, b: &T| compare(a, b) == Less;
1682 sort::partition_at_index(self, index, &mut f)
1685 /// Reorder the slice with a key extraction function such that the element at `index` is at its
1686 /// final sorted position.
1688 /// This reordering has the additional property that any value at position `i < index` will be
1689 /// less than or equal to any value at a position `j > index` using the key extraction function.
1690 /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at
1691 /// position `index`), in-place (i.e. does not allocate), and `O(n)` worst-case. This function
1692 /// is also known as "kth element" in other libraries. It returns a triplet of the following
1693 /// values: all elements less than the one at the given index, the value at the given index, and
1694 /// all elements greater than the one at the given index, using the provided key extraction
1697 /// # Current implementation
1699 /// The current algorithm is based on the quickselect portion of the same quicksort algorithm
1700 /// used for [`sort_unstable`].
1702 /// [`sort_unstable`]: #method.sort_unstable
1706 /// Panics when `index >= len()`, meaning it always panics on empty slices.
1711 /// #![feature(slice_partition_at_index)]
1713 /// let mut v = [-5i32, 4, 1, -3, 2];
1715 /// // Return the median as if the array were sorted according to absolute value.
1716 /// v.partition_at_index_by_key(2, |a| a.abs());
1718 /// // We are only guaranteed the slice will be one of the following, based on the way we sort
1719 /// // about the specified index.
1720 /// assert!(v == [1, 2, -3, 4, -5] ||
1721 /// v == [1, 2, -3, -5, 4] ||
1722 /// v == [2, 1, -3, 4, -5] ||
1723 /// v == [2, 1, -3, -5, 4]);
1725 #[unstable(feature = "slice_partition_at_index", issue = "55300")]
1727 pub fn partition_at_index_by_key<K, F>(&mut self, index: usize, mut f: F)
1728 -> (&mut [T], &mut T, &mut [T])
1729 where F: FnMut(&T) -> K, K: Ord
1731 let mut g = |a: &T, b: &T| f(a).lt(&f(b));
1732 sort::partition_at_index(self, index, &mut g)
1735 /// Moves all consecutive repeated elements to the end of the slice according to the
1736 /// [`PartialEq`] trait implementation.
1738 /// Returns two slices. The first contains no consecutive repeated elements.
1739 /// The second contains all the duplicates in no specified order.
1741 /// If the slice is sorted, the first returned slice contains no duplicates.
1746 /// #![feature(slice_partition_dedup)]
1748 /// let mut slice = [1, 2, 2, 3, 3, 2, 1, 1];
1750 /// let (dedup, duplicates) = slice.partition_dedup();
1752 /// assert_eq!(dedup, [1, 2, 3, 2, 1]);
1753 /// assert_eq!(duplicates, [2, 3, 1]);
1755 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1757 pub fn partition_dedup(&mut self) -> (&mut [T], &mut [T])
1760 self.partition_dedup_by(|a, b| a == b)
1763 /// Moves all but the first of consecutive elements to the end of the slice satisfying
1764 /// a given equality relation.
1766 /// Returns two slices. The first contains no consecutive repeated elements.
1767 /// The second contains all the duplicates in no specified order.
1769 /// The `same_bucket` function is passed references to two elements from the slice and
1770 /// must determine if the elements compare equal. The elements are passed in opposite order
1771 /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is moved
1772 /// at the end of the slice.
1774 /// If the slice is sorted, the first returned slice contains no duplicates.
1779 /// #![feature(slice_partition_dedup)]
1781 /// let mut slice = ["foo", "Foo", "BAZ", "Bar", "bar", "baz", "BAZ"];
1783 /// let (dedup, duplicates) = slice.partition_dedup_by(|a, b| a.eq_ignore_ascii_case(b));
1785 /// assert_eq!(dedup, ["foo", "BAZ", "Bar", "baz"]);
1786 /// assert_eq!(duplicates, ["bar", "Foo", "BAZ"]);
1788 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1790 pub fn partition_dedup_by<F>(&mut self, mut same_bucket: F) -> (&mut [T], &mut [T])
1791 where F: FnMut(&mut T, &mut T) -> bool
1793 // Although we have a mutable reference to `self`, we cannot make
1794 // *arbitrary* changes. The `same_bucket` calls could panic, so we
1795 // must ensure that the slice is in a valid state at all times.
1797 // The way that we handle this is by using swaps; we iterate
1798 // over all the elements, swapping as we go so that at the end
1799 // the elements we wish to keep are in the front, and those we
1800 // wish to reject are at the back. We can then split the slice.
1801 // This operation is still O(n).
1803 // Example: We start in this state, where `r` represents "next
1804 // read" and `w` represents "next_write`.
1807 // +---+---+---+---+---+---+
1808 // | 0 | 1 | 1 | 2 | 3 | 3 |
1809 // +---+---+---+---+---+---+
1812 // Comparing self[r] against self[w-1], this is not a duplicate, so
1813 // we swap self[r] and self[w] (no effect as r==w) and then increment both
1814 // r and w, leaving us with:
1817 // +---+---+---+---+---+---+
1818 // | 0 | 1 | 1 | 2 | 3 | 3 |
1819 // +---+---+---+---+---+---+
1822 // Comparing self[r] against self[w-1], this value is a duplicate,
1823 // so we increment `r` but leave everything else unchanged:
1826 // +---+---+---+---+---+---+
1827 // | 0 | 1 | 1 | 2 | 3 | 3 |
1828 // +---+---+---+---+---+---+
1831 // Comparing self[r] against self[w-1], this is not a duplicate,
1832 // so swap self[r] and self[w] and advance r and w:
1835 // +---+---+---+---+---+---+
1836 // | 0 | 1 | 2 | 1 | 3 | 3 |
1837 // +---+---+---+---+---+---+
1840 // Not a duplicate, repeat:
1843 // +---+---+---+---+---+---+
1844 // | 0 | 1 | 2 | 3 | 1 | 3 |
1845 // +---+---+---+---+---+---+
1848 // Duplicate, advance r. End of slice. Split at w.
1850 let len = self.len();
1852 return (self, &mut [])
1855 let ptr = self.as_mut_ptr();
1856 let mut next_read: usize = 1;
1857 let mut next_write: usize = 1;
1860 // Avoid bounds checks by using raw pointers.
1861 while next_read < len {
1862 let ptr_read = ptr.add(next_read);
1863 let prev_ptr_write = ptr.add(next_write - 1);
1864 if !same_bucket(&mut *ptr_read, &mut *prev_ptr_write) {
1865 if next_read != next_write {
1866 let ptr_write = prev_ptr_write.offset(1);
1867 mem::swap(&mut *ptr_read, &mut *ptr_write);
1875 self.split_at_mut(next_write)
1878 /// Moves all but the first of consecutive elements to the end of the slice that resolve
1879 /// to the same key.
1881 /// Returns two slices. The first contains no consecutive repeated elements.
1882 /// The second contains all the duplicates in no specified order.
1884 /// If the slice is sorted, the first returned slice contains no duplicates.
1889 /// #![feature(slice_partition_dedup)]
1891 /// let mut slice = [10, 20, 21, 30, 30, 20, 11, 13];
1893 /// let (dedup, duplicates) = slice.partition_dedup_by_key(|i| *i / 10);
1895 /// assert_eq!(dedup, [10, 20, 30, 20, 11]);
1896 /// assert_eq!(duplicates, [21, 30, 13]);
1898 #[unstable(feature = "slice_partition_dedup", issue = "54279")]
1900 pub fn partition_dedup_by_key<K, F>(&mut self, mut key: F) -> (&mut [T], &mut [T])
1901 where F: FnMut(&mut T) -> K,
1904 self.partition_dedup_by(|a, b| key(a) == key(b))
1907 /// Rotates the slice in-place such that the first `mid` elements of the
1908 /// slice move to the end while the last `self.len() - mid` elements move to
1909 /// the front. After calling `rotate_left`, the element previously at index
1910 /// `mid` will become the first element in the slice.
1914 /// This function will panic if `mid` is greater than the length of the
1915 /// slice. Note that `mid == self.len()` does _not_ panic and is a no-op
1920 /// Takes linear (in `self.len()`) time.
1925 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1926 /// a.rotate_left(2);
1927 /// assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
1930 /// Rotating a subslice:
1933 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1934 /// a[1..5].rotate_left(1);
1935 /// assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']);
1937 #[stable(feature = "slice_rotate", since = "1.26.0")]
1938 pub fn rotate_left(&mut self, mid: usize) {
1939 assert!(mid <= self.len());
1940 let k = self.len() - mid;
1943 let p = self.as_mut_ptr();
1944 rotate::ptr_rotate(mid, p.add(mid), k);
1948 /// Rotates the slice in-place such that the first `self.len() - k`
1949 /// elements of the slice move to the end while the last `k` elements move
1950 /// to the front. After calling `rotate_right`, the element previously at
1951 /// index `self.len() - k` will become the first element in the slice.
1955 /// This function will panic if `k` is greater than the length of the
1956 /// slice. Note that `k == self.len()` does _not_ panic and is a no-op
1961 /// Takes linear (in `self.len()`) time.
1966 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1967 /// a.rotate_right(2);
1968 /// assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);
1971 /// Rotate a subslice:
1974 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1975 /// a[1..5].rotate_right(1);
1976 /// assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']);
1978 #[stable(feature = "slice_rotate", since = "1.26.0")]
1979 pub fn rotate_right(&mut self, k: usize) {
1980 assert!(k <= self.len());
1981 let mid = self.len() - k;
1984 let p = self.as_mut_ptr();
1985 rotate::ptr_rotate(mid, p.add(mid), k);
1989 /// Copies the elements from `src` into `self`.
1991 /// The length of `src` must be the same as `self`.
1993 /// If `src` implements `Copy`, it can be more performant to use
1994 /// [`copy_from_slice`].
1998 /// This function will panic if the two slices have different lengths.
2002 /// Cloning two elements from a slice into another:
2005 /// let src = [1, 2, 3, 4];
2006 /// let mut dst = [0, 0];
2008 /// // Because the slices have to be the same length,
2009 /// // we slice the source slice from four elements
2010 /// // to two. It will panic if we don't do this.
2011 /// dst.clone_from_slice(&src[2..]);
2013 /// assert_eq!(src, [1, 2, 3, 4]);
2014 /// assert_eq!(dst, [3, 4]);
2017 /// Rust enforces that there can only be one mutable reference with no
2018 /// immutable references to a particular piece of data in a particular
2019 /// scope. Because of this, attempting to use `clone_from_slice` on a
2020 /// single slice will result in a compile failure:
2023 /// let mut slice = [1, 2, 3, 4, 5];
2025 /// slice[..2].clone_from_slice(&slice[3..]); // compile fail!
2028 /// To work around this, we can use [`split_at_mut`] to create two distinct
2029 /// sub-slices from a slice:
2032 /// let mut slice = [1, 2, 3, 4, 5];
2035 /// let (left, right) = slice.split_at_mut(2);
2036 /// left.clone_from_slice(&right[1..]);
2039 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
2042 /// [`copy_from_slice`]: #method.copy_from_slice
2043 /// [`split_at_mut`]: #method.split_at_mut
2044 #[stable(feature = "clone_from_slice", since = "1.7.0")]
2045 pub fn clone_from_slice(&mut self, src: &[T]) where T: Clone {
2046 assert!(self.len() == src.len(),
2047 "destination and source slices have different lengths");
2048 // NOTE: We need to explicitly slice them to the same length
2049 // for bounds checking to be elided, and the optimizer will
2050 // generate memcpy for simple cases (for example T = u8).
2051 let len = self.len();
2052 let src = &src[..len];
2054 self[i].clone_from(&src[i]);
2059 /// Copies all elements from `src` into `self`, using a memcpy.
2061 /// The length of `src` must be the same as `self`.
2063 /// If `src` does not implement `Copy`, use [`clone_from_slice`].
2067 /// This function will panic if the two slices have different lengths.
2071 /// Copying two elements from a slice into another:
2074 /// let src = [1, 2, 3, 4];
2075 /// let mut dst = [0, 0];
2077 /// // Because the slices have to be the same length,
2078 /// // we slice the source slice from four elements
2079 /// // to two. It will panic if we don't do this.
2080 /// dst.copy_from_slice(&src[2..]);
2082 /// assert_eq!(src, [1, 2, 3, 4]);
2083 /// assert_eq!(dst, [3, 4]);
2086 /// Rust enforces that there can only be one mutable reference with no
2087 /// immutable references to a particular piece of data in a particular
2088 /// scope. Because of this, attempting to use `copy_from_slice` on a
2089 /// single slice will result in a compile failure:
2092 /// let mut slice = [1, 2, 3, 4, 5];
2094 /// slice[..2].copy_from_slice(&slice[3..]); // compile fail!
2097 /// To work around this, we can use [`split_at_mut`] to create two distinct
2098 /// sub-slices from a slice:
2101 /// let mut slice = [1, 2, 3, 4, 5];
2104 /// let (left, right) = slice.split_at_mut(2);
2105 /// left.copy_from_slice(&right[1..]);
2108 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
2111 /// [`clone_from_slice`]: #method.clone_from_slice
2112 /// [`split_at_mut`]: #method.split_at_mut
2113 #[stable(feature = "copy_from_slice", since = "1.9.0")]
2114 pub fn copy_from_slice(&mut self, src: &[T]) where T: Copy {
2115 assert_eq!(self.len(), src.len(),
2116 "destination and source slices have different lengths");
2118 ptr::copy_nonoverlapping(
2119 src.as_ptr(), self.as_mut_ptr(), self.len());
2123 /// Copies elements from one part of the slice to another part of itself,
2124 /// using a memmove.
2126 /// `src` is the range within `self` to copy from. `dest` is the starting
2127 /// index of the range within `self` to copy to, which will have the same
2128 /// length as `src`. The two ranges may overlap. The ends of the two ranges
2129 /// must be less than or equal to `self.len()`.
2133 /// This function will panic if either range exceeds the end of the slice,
2134 /// or if the end of `src` is before the start.
2138 /// Copying four bytes within a slice:
2141 /// # #![feature(copy_within)]
2142 /// let mut bytes = *b"Hello, World!";
2144 /// bytes.copy_within(1..5, 8);
2146 /// assert_eq!(&bytes, b"Hello, Wello!");
2148 #[unstable(feature = "copy_within", issue = "54236")]
2149 pub fn copy_within<R: ops::RangeBounds<usize>>(&mut self, src: R, dest: usize)
2153 let src_start = match src.start_bound() {
2154 ops::Bound::Included(&n) => n,
2155 ops::Bound::Excluded(&n) => n
2157 .unwrap_or_else(|| slice_index_overflow_fail()),
2158 ops::Bound::Unbounded => 0,
2160 let src_end = match src.end_bound() {
2161 ops::Bound::Included(&n) => n
2163 .unwrap_or_else(|| slice_index_overflow_fail()),
2164 ops::Bound::Excluded(&n) => n,
2165 ops::Bound::Unbounded => self.len(),
2167 assert!(src_start <= src_end, "src end is before src start");
2168 assert!(src_end <= self.len(), "src is out of bounds");
2169 let count = src_end - src_start;
2170 assert!(dest <= self.len() - count, "dest is out of bounds");
2173 self.get_unchecked(src_start),
2174 self.get_unchecked_mut(dest),
2180 /// Swaps all elements in `self` with those in `other`.
2182 /// The length of `other` must be the same as `self`.
2186 /// This function will panic if the two slices have different lengths.
2190 /// Swapping two elements across slices:
2193 /// let mut slice1 = [0, 0];
2194 /// let mut slice2 = [1, 2, 3, 4];
2196 /// slice1.swap_with_slice(&mut slice2[2..]);
2198 /// assert_eq!(slice1, [3, 4]);
2199 /// assert_eq!(slice2, [1, 2, 0, 0]);
2202 /// Rust enforces that there can only be one mutable reference to a
2203 /// particular piece of data in a particular scope. Because of this,
2204 /// attempting to use `swap_with_slice` on a single slice will result in
2205 /// a compile failure:
2208 /// let mut slice = [1, 2, 3, 4, 5];
2209 /// slice[..2].swap_with_slice(&mut slice[3..]); // compile fail!
2212 /// To work around this, we can use [`split_at_mut`] to create two distinct
2213 /// mutable sub-slices from a slice:
2216 /// let mut slice = [1, 2, 3, 4, 5];
2219 /// let (left, right) = slice.split_at_mut(2);
2220 /// left.swap_with_slice(&mut right[1..]);
2223 /// assert_eq!(slice, [4, 5, 3, 1, 2]);
2226 /// [`split_at_mut`]: #method.split_at_mut
2227 #[stable(feature = "swap_with_slice", since = "1.27.0")]
2228 pub fn swap_with_slice(&mut self, other: &mut [T]) {
2229 assert!(self.len() == other.len(),
2230 "destination and source slices have different lengths");
2232 ptr::swap_nonoverlapping(
2233 self.as_mut_ptr(), other.as_mut_ptr(), self.len());
2237 /// Function to calculate lengths of the middle and trailing slice for `align_to{,_mut}`.
2238 fn align_to_offsets<U>(&self) -> (usize, usize) {
2239 // What we gonna do about `rest` is figure out what multiple of `U`s we can put in a
2240 // lowest number of `T`s. And how many `T`s we need for each such "multiple".
2242 // Consider for example T=u8 U=u16. Then we can put 1 U in 2 Ts. Simple. Now, consider
2243 // for example a case where size_of::<T> = 16, size_of::<U> = 24. We can put 2 Us in
2244 // place of every 3 Ts in the `rest` slice. A bit more complicated.
2246 // Formula to calculate this is:
2248 // Us = lcm(size_of::<T>, size_of::<U>) / size_of::<U>
2249 // Ts = lcm(size_of::<T>, size_of::<U>) / size_of::<T>
2251 // Expanded and simplified:
2253 // Us = size_of::<T> / gcd(size_of::<T>, size_of::<U>)
2254 // Ts = size_of::<U> / gcd(size_of::<T>, size_of::<U>)
2256 // Luckily since all this is constant-evaluated... performance here matters not!
2258 fn gcd(a: usize, b: usize) -> usize {
2259 use crate::intrinsics;
2260 // iterative stein’s algorithm
2261 // We should still make this `const fn` (and revert to recursive algorithm if we do)
2262 // because relying on llvm to consteval all this is… well, it makes me uncomfortable.
2263 let (ctz_a, mut ctz_b) = unsafe {
2264 if a == 0 { return b; }
2265 if b == 0 { return a; }
2266 (intrinsics::cttz_nonzero(a), intrinsics::cttz_nonzero(b))
2268 let k = ctz_a.min(ctz_b);
2269 let mut a = a >> ctz_a;
2272 // remove all factors of 2 from b
2275 mem::swap(&mut a, &mut b);
2282 ctz_b = intrinsics::cttz_nonzero(b);
2287 let gcd: usize = gcd(mem::size_of::<T>(), mem::size_of::<U>());
2288 let ts: usize = mem::size_of::<U>() / gcd;
2289 let us: usize = mem::size_of::<T>() / gcd;
2291 // Armed with this knowledge, we can find how many `U`s we can fit!
2292 let us_len = self.len() / ts * us;
2293 // And how many `T`s will be in the trailing slice!
2294 let ts_len = self.len() % ts;
2298 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
2301 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
2302 /// slice of a new type, and the suffix slice. The method does a best effort to make the
2303 /// middle slice the greatest length possible for a given type and input slice, but only
2304 /// your algorithm's performance should depend on that, not its correctness.
2306 /// This method has no purpose when either input element `T` or output element `U` are
2307 /// zero-sized and will return the original slice without splitting anything.
2311 /// This method is essentially a `transmute` with respect to the elements in the returned
2312 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
2320 /// let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
2321 /// let (prefix, shorts, suffix) = bytes.align_to::<u16>();
2322 /// // less_efficient_algorithm_for_bytes(prefix);
2323 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
2324 /// // less_efficient_algorithm_for_bytes(suffix);
2327 #[stable(feature = "slice_align_to", since = "1.30.0")]
2328 pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T]) {
2329 // Note that most of this function will be constant-evaluated,
2330 if mem::size_of::<U>() == 0 || mem::size_of::<T>() == 0 {
2331 // handle ZSTs specially, which is – don't handle them at all.
2332 return (self, &[], &[]);
2335 // First, find at what point do we split between the first and 2nd slice. Easy with
2336 // ptr.align_offset.
2337 let ptr = self.as_ptr();
2338 let offset = crate::ptr::align_offset(ptr, mem::align_of::<U>());
2339 if offset > self.len() {
2342 let (left, rest) = self.split_at(offset);
2343 // now `rest` is definitely aligned, so `from_raw_parts_mut` below is okay
2344 let (us_len, ts_len) = rest.align_to_offsets::<U>();
2346 from_raw_parts(rest.as_ptr() as *const U, us_len),
2347 from_raw_parts(rest.as_ptr().add(rest.len() - ts_len), ts_len))
2351 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
2354 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
2355 /// slice of a new type, and the suffix slice. The method does a best effort to make the
2356 /// middle slice the greatest length possible for a given type and input slice, but only
2357 /// your algorithm's performance should depend on that, not its correctness.
2359 /// This method has no purpose when either input element `T` or output element `U` are
2360 /// zero-sized and will return the original slice without splitting anything.
2364 /// This method is essentially a `transmute` with respect to the elements in the returned
2365 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
2373 /// let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
2374 /// let (prefix, shorts, suffix) = bytes.align_to_mut::<u16>();
2375 /// // less_efficient_algorithm_for_bytes(prefix);
2376 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
2377 /// // less_efficient_algorithm_for_bytes(suffix);
2380 #[stable(feature = "slice_align_to", since = "1.30.0")]
2381 pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T]) {
2382 // Note that most of this function will be constant-evaluated,
2383 if mem::size_of::<U>() == 0 || mem::size_of::<T>() == 0 {
2384 // handle ZSTs specially, which is – don't handle them at all.
2385 return (self, &mut [], &mut []);
2388 // First, find at what point do we split between the first and 2nd slice. Easy with
2389 // ptr.align_offset.
2390 let ptr = self.as_ptr();
2391 let offset = crate::ptr::align_offset(ptr, mem::align_of::<U>());
2392 if offset > self.len() {
2393 (self, &mut [], &mut [])
2395 let (left, rest) = self.split_at_mut(offset);
2396 // now `rest` is definitely aligned, so `from_raw_parts_mut` below is okay
2397 let (us_len, ts_len) = rest.align_to_offsets::<U>();
2398 let mut_ptr = rest.as_mut_ptr();
2400 from_raw_parts_mut(mut_ptr as *mut U, us_len),
2401 from_raw_parts_mut(mut_ptr.add(rest.len() - ts_len), ts_len))
2405 /// Checks if the elements of this slice are sorted.
2407 /// That is, for each element `a` and its following element `b`, `a <= b` must hold. If the
2408 /// slice yields exactly zero or one element, `true` is returned.
2410 /// Note that if `Self::Item` is only `PartialOrd`, but not `Ord`, the above definition
2411 /// implies that this function returns `false` if any two consecutive items are not
2417 /// #![feature(is_sorted)]
2418 /// let empty: [i32; 0] = [];
2420 /// assert!([1, 2, 2, 9].is_sorted());
2421 /// assert!(![1, 3, 2, 4].is_sorted());
2422 /// assert!([0].is_sorted());
2423 /// assert!(empty.is_sorted());
2424 /// assert!(![0.0, 1.0, std::f32::NAN].is_sorted());
2427 #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
2428 pub fn is_sorted(&self) -> bool
2432 self.is_sorted_by(|a, b| a.partial_cmp(b))
2435 /// Checks if the elements of this slice are sorted using the given comparator function.
2437 /// Instead of using `PartialOrd::partial_cmp`, this function uses the given `compare`
2438 /// function to determine the ordering of two elements. Apart from that, it's equivalent to
2439 /// [`is_sorted`]; see its documentation for more information.
2441 /// [`is_sorted`]: #method.is_sorted
2442 #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
2443 pub fn is_sorted_by<F>(&self, mut compare: F) -> bool
2445 F: FnMut(&T, &T) -> Option<Ordering>
2447 self.iter().is_sorted_by(|a, b| compare(*a, *b))
2450 /// Checks if the elements of this slice are sorted using the given key extraction function.
2452 /// Instead of comparing the slice's elements directly, this function compares the keys of the
2453 /// elements, as determined by `f`. Apart from that, it's equivalent to [`is_sorted`]; see its
2454 /// documentation for more information.
2456 /// [`is_sorted`]: #method.is_sorted
2461 /// #![feature(is_sorted)]
2463 /// assert!(["c", "bb", "aaa"].is_sorted_by_key(|s| s.len()));
2464 /// assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs()));
2467 #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")]
2468 pub fn is_sorted_by_key<F, K>(&self, mut f: F) -> bool
2473 self.is_sorted_by(|a, b| f(a).partial_cmp(&f(b)))
2477 #[lang = "slice_u8"]
2480 /// Checks if all bytes in this slice are within the ASCII range.
2481 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2483 pub fn is_ascii(&self) -> bool {
2484 self.iter().all(|b| b.is_ascii())
2487 /// Checks that two slices are an ASCII case-insensitive match.
2489 /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
2490 /// but without allocating and copying temporaries.
2491 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2493 pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool {
2494 self.len() == other.len() &&
2495 self.iter().zip(other).all(|(a, b)| {
2496 a.eq_ignore_ascii_case(b)
2500 /// Converts this slice to its ASCII upper case equivalent in-place.
2502 /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
2503 /// but non-ASCII letters are unchanged.
2505 /// To return a new uppercased value without modifying the existing one, use
2506 /// [`to_ascii_uppercase`].
2508 /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
2509 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2511 pub fn make_ascii_uppercase(&mut self) {
2513 byte.make_ascii_uppercase();
2517 /// Converts this slice to its ASCII lower case equivalent in-place.
2519 /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
2520 /// but non-ASCII letters are unchanged.
2522 /// To return a new lowercased value without modifying the existing one, use
2523 /// [`to_ascii_lowercase`].
2525 /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
2526 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2528 pub fn make_ascii_lowercase(&mut self) {
2530 byte.make_ascii_lowercase();
2536 #[stable(feature = "rust1", since = "1.0.0")]
2537 impl<T, I> ops::Index<I> for [T]
2538 where I: SliceIndex<[T]>
2540 type Output = I::Output;
2543 fn index(&self, index: I) -> &I::Output {
2548 #[stable(feature = "rust1", since = "1.0.0")]
2549 impl<T, I> ops::IndexMut<I> for [T]
2550 where I: SliceIndex<[T]>
2553 fn index_mut(&mut self, index: I) -> &mut I::Output {
2554 index.index_mut(self)
2560 fn slice_index_len_fail(index: usize, len: usize) -> ! {
2561 panic!("index {} out of range for slice of length {}", index, len);
2566 fn slice_index_order_fail(index: usize, end: usize) -> ! {
2567 panic!("slice index starts at {} but ends at {}", index, end);
2572 fn slice_index_overflow_fail() -> ! {
2573 panic!("attempted to index slice up to maximum usize");
2576 mod private_slice_index {
2578 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2581 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2582 impl Sealed for usize {}
2583 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2584 impl Sealed for ops::Range<usize> {}
2585 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2586 impl Sealed for ops::RangeTo<usize> {}
2587 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2588 impl Sealed for ops::RangeFrom<usize> {}
2589 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2590 impl Sealed for ops::RangeFull {}
2591 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2592 impl Sealed for ops::RangeInclusive<usize> {}
2593 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2594 impl Sealed for ops::RangeToInclusive<usize> {}
2597 /// A helper trait used for indexing operations.
2598 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2599 #[rustc_on_unimplemented(
2602 label = "string indices are ranges of `usize`",
2605 all(any(T = "str", T = "&str", T = "std::string::String"), _Self="{integer}"),
2606 note="you can use `.chars().nth()` or `.bytes().nth()`
2607 see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>"
2609 message = "the type `{T}` cannot be indexed by `{Self}`",
2610 label = "slice indices are of type `usize` or ranges of `usize`",
2612 pub trait SliceIndex<T: ?Sized>: private_slice_index::Sealed {
2613 /// The output type returned by methods.
2614 #[stable(feature = "slice_get_slice", since = "1.28.0")]
2615 type Output: ?Sized;
2617 /// Returns a shared reference to the output at this location, if in
2619 #[unstable(feature = "slice_index_methods", issue = "0")]
2620 fn get(self, slice: &T) -> Option<&Self::Output>;
2622 /// Returns a mutable reference to the output at this location, if in
2624 #[unstable(feature = "slice_index_methods", issue = "0")]
2625 fn get_mut(self, slice: &mut T) -> Option<&mut Self::Output>;
2627 /// Returns a shared reference to the output at this location, without
2628 /// performing any bounds checking.
2629 #[unstable(feature = "slice_index_methods", issue = "0")]
2630 unsafe fn get_unchecked(self, slice: &T) -> &Self::Output;
2632 /// Returns a mutable reference to the output at this location, without
2633 /// performing any bounds checking.
2634 #[unstable(feature = "slice_index_methods", issue = "0")]
2635 unsafe fn get_unchecked_mut(self, slice: &mut T) -> &mut Self::Output;
2637 /// Returns a shared reference to the output at this location, panicking
2638 /// if out of bounds.
2639 #[unstable(feature = "slice_index_methods", issue = "0")]
2640 fn index(self, slice: &T) -> &Self::Output;
2642 /// Returns a mutable reference to the output at this location, panicking
2643 /// if out of bounds.
2644 #[unstable(feature = "slice_index_methods", issue = "0")]
2645 fn index_mut(self, slice: &mut T) -> &mut Self::Output;
2648 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2649 impl<T> SliceIndex<[T]> for usize {
2653 fn get(self, slice: &[T]) -> Option<&T> {
2654 if self < slice.len() {
2656 Some(self.get_unchecked(slice))
2664 fn get_mut(self, slice: &mut [T]) -> Option<&mut T> {
2665 if self < slice.len() {
2667 Some(self.get_unchecked_mut(slice))
2675 unsafe fn get_unchecked(self, slice: &[T]) -> &T {
2676 &*slice.as_ptr().add(self)
2680 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut T {
2681 &mut *slice.as_mut_ptr().add(self)
2685 fn index(self, slice: &[T]) -> &T {
2686 // N.B., use intrinsic indexing
2691 fn index_mut(self, slice: &mut [T]) -> &mut T {
2692 // N.B., use intrinsic indexing
2697 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2698 impl<T> SliceIndex<[T]> for ops::Range<usize> {
2702 fn get(self, slice: &[T]) -> Option<&[T]> {
2703 if self.start > self.end || self.end > slice.len() {
2707 Some(self.get_unchecked(slice))
2713 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2714 if self.start > self.end || self.end > slice.len() {
2718 Some(self.get_unchecked_mut(slice))
2724 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2725 from_raw_parts(slice.as_ptr().add(self.start), self.end - self.start)
2729 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2730 from_raw_parts_mut(slice.as_mut_ptr().add(self.start), self.end - self.start)
2734 fn index(self, slice: &[T]) -> &[T] {
2735 if self.start > self.end {
2736 slice_index_order_fail(self.start, self.end);
2737 } else if self.end > slice.len() {
2738 slice_index_len_fail(self.end, slice.len());
2741 self.get_unchecked(slice)
2746 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2747 if self.start > self.end {
2748 slice_index_order_fail(self.start, self.end);
2749 } else if self.end > slice.len() {
2750 slice_index_len_fail(self.end, slice.len());
2753 self.get_unchecked_mut(slice)
2758 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2759 impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {
2763 fn get(self, slice: &[T]) -> Option<&[T]> {
2764 (0..self.end).get(slice)
2768 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2769 (0..self.end).get_mut(slice)
2773 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2774 (0..self.end).get_unchecked(slice)
2778 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2779 (0..self.end).get_unchecked_mut(slice)
2783 fn index(self, slice: &[T]) -> &[T] {
2784 (0..self.end).index(slice)
2788 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2789 (0..self.end).index_mut(slice)
2793 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2794 impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {
2798 fn get(self, slice: &[T]) -> Option<&[T]> {
2799 (self.start..slice.len()).get(slice)
2803 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2804 (self.start..slice.len()).get_mut(slice)
2808 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2809 (self.start..slice.len()).get_unchecked(slice)
2813 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2814 (self.start..slice.len()).get_unchecked_mut(slice)
2818 fn index(self, slice: &[T]) -> &[T] {
2819 (self.start..slice.len()).index(slice)
2823 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2824 (self.start..slice.len()).index_mut(slice)
2828 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2829 impl<T> SliceIndex<[T]> for ops::RangeFull {
2833 fn get(self, slice: &[T]) -> Option<&[T]> {
2838 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2843 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2848 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2853 fn index(self, slice: &[T]) -> &[T] {
2858 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2864 #[stable(feature = "inclusive_range", since = "1.26.0")]
2865 impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> {
2869 fn get(self, slice: &[T]) -> Option<&[T]> {
2870 if *self.end() == usize::max_value() { None }
2871 else { (*self.start()..self.end() + 1).get(slice) }
2875 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2876 if *self.end() == usize::max_value() { None }
2877 else { (*self.start()..self.end() + 1).get_mut(slice) }
2881 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2882 (*self.start()..self.end() + 1).get_unchecked(slice)
2886 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2887 (*self.start()..self.end() + 1).get_unchecked_mut(slice)
2891 fn index(self, slice: &[T]) -> &[T] {
2892 if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
2893 (*self.start()..self.end() + 1).index(slice)
2897 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2898 if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
2899 (*self.start()..self.end() + 1).index_mut(slice)
2903 #[stable(feature = "inclusive_range", since = "1.26.0")]
2904 impl<T> SliceIndex<[T]> for ops::RangeToInclusive<usize> {
2908 fn get(self, slice: &[T]) -> Option<&[T]> {
2909 (0..=self.end).get(slice)
2913 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2914 (0..=self.end).get_mut(slice)
2918 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2919 (0..=self.end).get_unchecked(slice)
2923 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2924 (0..=self.end).get_unchecked_mut(slice)
2928 fn index(self, slice: &[T]) -> &[T] {
2929 (0..=self.end).index(slice)
2933 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2934 (0..=self.end).index_mut(slice)
2938 ////////////////////////////////////////////////////////////////////////////////
2940 ////////////////////////////////////////////////////////////////////////////////
2942 #[stable(feature = "rust1", since = "1.0.0")]
2943 impl<T> Default for &[T] {
2944 /// Creates an empty slice.
2945 fn default() -> Self { &[] }
2948 #[stable(feature = "mut_slice_default", since = "1.5.0")]
2949 impl<T> Default for &mut [T] {
2950 /// Creates a mutable empty slice.
2951 fn default() -> Self { &mut [] }
2958 #[stable(feature = "rust1", since = "1.0.0")]
2959 impl<'a, T> IntoIterator for &'a [T] {
2961 type IntoIter = Iter<'a, T>;
2963 fn into_iter(self) -> Iter<'a, T> {
2968 #[stable(feature = "rust1", since = "1.0.0")]
2969 impl<'a, T> IntoIterator for &'a mut [T] {
2970 type Item = &'a mut T;
2971 type IntoIter = IterMut<'a, T>;
2973 fn into_iter(self) -> IterMut<'a, T> {
2978 // Macro helper functions
2980 fn size_from_ptr<T>(_: *const T) -> usize {
2984 // Inlining is_empty and len makes a huge performance difference
2985 macro_rules! is_empty {
2986 // The way we encode the length of a ZST iterator, this works both for ZST
2988 ($self: ident) => {$self.ptr == $self.end}
2990 // To get rid of some bounds checks (see `position`), we compute the length in a somewhat
2991 // unexpected way. (Tested by `codegen/slice-position-bounds-check`.)
2993 ($self: ident) => {{
2994 let start = $self.ptr;
2995 let diff = ($self.end as usize).wrapping_sub(start as usize);
2996 let size = size_from_ptr(start);
3000 // Using division instead of `offset_from` helps LLVM remove bounds checks
3006 // The shared definition of the `Iter` and `IterMut` iterators
3007 macro_rules! iterator {
3009 struct $name:ident -> $ptr:ty,
3015 impl<'a, T> $name<'a, T> {
3016 // Helper function for creating a slice from the iterator.
3018 fn make_slice(&self) -> &'a [T] {
3019 unsafe { from_raw_parts(self.ptr, len!(self)) }
3022 // Helper function for moving the start of the iterator forwards by `offset` elements,
3023 // returning the old start.
3024 // Unsafe because the offset must be in-bounds or one-past-the-end.
3026 unsafe fn post_inc_start(&mut self, offset: isize) -> * $raw_mut T {
3027 if mem::size_of::<T>() == 0 {
3028 // This is *reducing* the length. `ptr` never changes with ZST.
3029 self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
3033 self.ptr = self.ptr.offset(offset);
3038 // Helper function for moving the end of the iterator backwards by `offset` elements,
3039 // returning the new end.
3040 // Unsafe because the offset must be in-bounds or one-past-the-end.
3042 unsafe fn pre_dec_end(&mut self, offset: isize) -> * $raw_mut T {
3043 if mem::size_of::<T>() == 0 {
3044 self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
3047 self.end = self.end.offset(-offset);
3053 #[stable(feature = "rust1", since = "1.0.0")]
3054 impl<T> ExactSizeIterator for $name<'_, T> {
3056 fn len(&self) -> usize {
3061 fn is_empty(&self) -> bool {
3066 #[stable(feature = "rust1", since = "1.0.0")]
3067 impl<'a, T> Iterator for $name<'a, T> {
3071 fn next(&mut self) -> Option<$elem> {
3072 // could be implemented with slices, but this avoids bounds checks
3074 assume(!self.ptr.is_null());
3075 if mem::size_of::<T>() != 0 {
3076 assume(!self.end.is_null());
3078 if is_empty!(self) {
3081 Some(& $( $mut_ )* *self.post_inc_start(1))
3087 fn size_hint(&self) -> (usize, Option<usize>) {
3088 let exact = len!(self);
3089 (exact, Some(exact))
3093 fn count(self) -> usize {
3098 fn nth(&mut self, n: usize) -> Option<$elem> {
3099 if n >= len!(self) {
3100 // This iterator is now empty.
3101 if mem::size_of::<T>() == 0 {
3102 // We have to do it this way as `ptr` may never be 0, but `end`
3103 // could be (due to wrapping).
3104 self.end = self.ptr;
3106 self.ptr = self.end;
3110 // We are in bounds. `offset` does the right thing even for ZSTs.
3112 let elem = Some(& $( $mut_ )* *self.ptr.add(n));
3113 self.post_inc_start((n as isize).wrapping_add(1));
3119 fn last(mut self) -> Option<$elem> {
3124 fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where
3125 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
3127 // manual unrolling is needed when there are conditional exits from the loop
3128 let mut accum = init;
3130 while len!(self) >= 4 {
3131 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
3132 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
3133 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
3134 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
3136 while !is_empty!(self) {
3137 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
3144 fn fold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
3145 where Fold: FnMut(Acc, Self::Item) -> Acc,
3147 // Let LLVM unroll this, rather than using the default
3148 // impl that would force the manual unrolling above
3149 let mut accum = init;
3150 while let Some(x) = self.next() {
3151 accum = f(accum, x);
3157 #[rustc_inherit_overflow_checks]
3158 fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
3160 P: FnMut(Self::Item) -> bool,
3162 // The addition might panic on overflow.
3164 self.try_fold(0, move |i, x| {
3165 if predicate(x) { Err(i) }
3169 unsafe { assume(i < n) };
3175 fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where
3176 P: FnMut(Self::Item) -> bool,
3177 Self: Sized + ExactSizeIterator + DoubleEndedIterator
3179 // No need for an overflow check here, because `ExactSizeIterator`
3181 self.try_rfold(n, move |i, x| {
3183 if predicate(x) { Err(i) }
3187 unsafe { assume(i < n) };
3195 #[stable(feature = "rust1", since = "1.0.0")]
3196 impl<'a, T> DoubleEndedIterator for $name<'a, T> {
3198 fn next_back(&mut self) -> Option<$elem> {
3199 // could be implemented with slices, but this avoids bounds checks
3201 assume(!self.ptr.is_null());
3202 if mem::size_of::<T>() != 0 {
3203 assume(!self.end.is_null());
3205 if is_empty!(self) {
3208 Some(& $( $mut_ )* *self.pre_dec_end(1))
3214 fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where
3215 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
3217 // manual unrolling is needed when there are conditional exits from the loop
3218 let mut accum = init;
3220 while len!(self) >= 4 {
3221 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
3222 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
3223 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
3224 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
3226 // inlining is_empty everywhere makes a huge performance difference
3227 while !is_empty!(self) {
3228 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
3235 fn rfold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
3236 where Fold: FnMut(Acc, Self::Item) -> Acc,
3238 // Let LLVM unroll this, rather than using the default
3239 // impl that would force the manual unrolling above
3240 let mut accum = init;
3241 while let Some(x) = self.next_back() {
3242 accum = f(accum, x);
3248 #[stable(feature = "fused", since = "1.26.0")]
3249 impl<T> FusedIterator for $name<'_, T> {}
3251 #[unstable(feature = "trusted_len", issue = "37572")]
3252 unsafe impl<T> TrustedLen for $name<'_, T> {}
3256 /// Immutable slice iterator
3258 /// This struct is created by the [`iter`] method on [slices].
3265 /// // First, we declare a type which has `iter` method to get the `Iter` struct (&[usize here]):
3266 /// let slice = &[1, 2, 3];
3268 /// // Then, we iterate over it:
3269 /// for element in slice.iter() {
3270 /// println!("{}", element);
3274 /// [`iter`]: ../../std/primitive.slice.html#method.iter
3275 /// [slices]: ../../std/primitive.slice.html
3276 #[stable(feature = "rust1", since = "1.0.0")]
3277 pub struct Iter<'a, T: 'a> {
3279 end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
3280 // ptr == end is a quick test for the Iterator being empty, that works
3281 // for both ZST and non-ZST.
3282 _marker: marker::PhantomData<&'a T>,
3285 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3286 impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
3287 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3288 f.debug_tuple("Iter")
3289 .field(&self.as_slice())
3294 #[stable(feature = "rust1", since = "1.0.0")]
3295 unsafe impl<T: Sync> Sync for Iter<'_, T> {}
3296 #[stable(feature = "rust1", since = "1.0.0")]
3297 unsafe impl<T: Sync> Send for Iter<'_, T> {}
3299 impl<'a, T> Iter<'a, T> {
3300 /// Views the underlying data as a subslice of the original data.
3302 /// This has the same lifetime as the original slice, and so the
3303 /// iterator can continue to be used while this exists.
3310 /// // First, we declare a type which has the `iter` method to get the `Iter`
3311 /// // struct (&[usize here]):
3312 /// let slice = &[1, 2, 3];
3314 /// // Then, we get the iterator:
3315 /// let mut iter = slice.iter();
3316 /// // So if we print what `as_slice` method returns here, we have "[1, 2, 3]":
3317 /// println!("{:?}", iter.as_slice());
3319 /// // Next, we move to the second element of the slice:
3321 /// // Now `as_slice` returns "[2, 3]":
3322 /// println!("{:?}", iter.as_slice());
3324 #[stable(feature = "iter_to_slice", since = "1.4.0")]
3325 pub fn as_slice(&self) -> &'a [T] {
3330 iterator!{struct Iter -> *const T, &'a T, const, {/* no mut */}, {
3331 fn is_sorted_by<F>(self, mut compare: F) -> bool
3334 F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
3336 self.as_slice().windows(2).all(|w| {
3337 compare(&&w[0], &&w[1]).map(|o| o != Ordering::Greater).unwrap_or(false)
3342 #[stable(feature = "rust1", since = "1.0.0")]
3343 impl<T> Clone for Iter<'_, T> {
3344 fn clone(&self) -> Self { Iter { ptr: self.ptr, end: self.end, _marker: self._marker } }
3347 #[stable(feature = "slice_iter_as_ref", since = "1.13.0")]
3348 impl<T> AsRef<[T]> for Iter<'_, T> {
3349 fn as_ref(&self) -> &[T] {
3354 /// Mutable slice iterator.
3356 /// This struct is created by the [`iter_mut`] method on [slices].
3363 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
3364 /// // struct (&[usize here]):
3365 /// let mut slice = &mut [1, 2, 3];
3367 /// // Then, we iterate over it and increment each element value:
3368 /// for element in slice.iter_mut() {
3372 /// // We now have "[2, 3, 4]":
3373 /// println!("{:?}", slice);
3376 /// [`iter_mut`]: ../../std/primitive.slice.html#method.iter_mut
3377 /// [slices]: ../../std/primitive.slice.html
3378 #[stable(feature = "rust1", since = "1.0.0")]
3379 pub struct IterMut<'a, T: 'a> {
3381 end: *mut T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
3382 // ptr == end is a quick test for the Iterator being empty, that works
3383 // for both ZST and non-ZST.
3384 _marker: marker::PhantomData<&'a mut T>,
3387 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3388 impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
3389 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3390 f.debug_tuple("IterMut")
3391 .field(&self.make_slice())
3396 #[stable(feature = "rust1", since = "1.0.0")]
3397 unsafe impl<T: Sync> Sync for IterMut<'_, T> {}
3398 #[stable(feature = "rust1", since = "1.0.0")]
3399 unsafe impl<T: Send> Send for IterMut<'_, T> {}
3401 impl<'a, T> IterMut<'a, T> {
3402 /// Views the underlying data as a subslice of the original data.
3404 /// To avoid creating `&mut` references that alias, this is forced
3405 /// to consume the iterator.
3412 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
3413 /// // struct (&[usize here]):
3414 /// let mut slice = &mut [1, 2, 3];
3417 /// // Then, we get the iterator:
3418 /// let mut iter = slice.iter_mut();
3419 /// // We move to next element:
3421 /// // So if we print what `into_slice` method returns here, we have "[2, 3]":
3422 /// println!("{:?}", iter.into_slice());
3425 /// // Now let's modify a value of the slice:
3427 /// // First we get back the iterator:
3428 /// let mut iter = slice.iter_mut();
3429 /// // We change the value of the first element of the slice returned by the `next` method:
3430 /// *iter.next().unwrap() += 1;
3432 /// // Now slice is "[2, 2, 3]":
3433 /// println!("{:?}", slice);
3435 #[stable(feature = "iter_to_slice", since = "1.4.0")]
3436 pub fn into_slice(self) -> &'a mut [T] {
3437 unsafe { from_raw_parts_mut(self.ptr, len!(self)) }
3440 /// Views the underlying data as a subslice of the original data.
3442 /// To avoid creating `&mut [T]` references that alias, the returned slice
3443 /// borrows its lifetime from the iterator the method is applied on.
3450 /// # #![feature(slice_iter_mut_as_slice)]
3451 /// let mut slice: &mut [usize] = &mut [1, 2, 3];
3453 /// // First, we get the iterator:
3454 /// let mut iter = slice.iter_mut();
3455 /// // So if we check what the `as_slice` method returns here, we have "[1, 2, 3]":
3456 /// assert_eq!(iter.as_slice(), &[1, 2, 3]);
3458 /// // Next, we move to the second element of the slice:
3460 /// // Now `as_slice` returns "[2, 3]":
3461 /// assert_eq!(iter.as_slice(), &[2, 3]);
3463 #[unstable(feature = "slice_iter_mut_as_slice", reason = "recently added", issue = "58957")]
3464 pub fn as_slice(&self) -> &[T] {
3469 iterator!{struct IterMut -> *mut T, &'a mut T, mut, {mut}, {}}
3471 /// An internal abstraction over the splitting iterators, so that
3472 /// splitn, splitn_mut etc can be implemented once.
3474 trait SplitIter: DoubleEndedIterator {
3475 /// Marks the underlying iterator as complete, extracting the remaining
3476 /// portion of the slice.
3477 fn finish(&mut self) -> Option<Self::Item>;
3480 /// An iterator over subslices separated by elements that match a predicate
3483 /// This struct is created by the [`split`] method on [slices].
3485 /// [`split`]: ../../std/primitive.slice.html#method.split
3486 /// [slices]: ../../std/primitive.slice.html
3487 #[stable(feature = "rust1", since = "1.0.0")]
3488 pub struct Split<'a, T:'a, P> where P: FnMut(&T) -> bool {
3494 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3495 impl<T: fmt::Debug, P> fmt::Debug for Split<'_, T, P> where P: FnMut(&T) -> bool {
3496 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3497 f.debug_struct("Split")
3498 .field("v", &self.v)
3499 .field("finished", &self.finished)
3504 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3505 #[stable(feature = "rust1", since = "1.0.0")]
3506 impl<T, P> Clone for Split<'_, T, P> where P: Clone + FnMut(&T) -> bool {
3507 fn clone(&self) -> Self {
3510 pred: self.pred.clone(),
3511 finished: self.finished,
3516 #[stable(feature = "rust1", since = "1.0.0")]
3517 impl<'a, T, P> Iterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
3518 type Item = &'a [T];
3521 fn next(&mut self) -> Option<&'a [T]> {
3522 if self.finished { return None; }
3524 match self.v.iter().position(|x| (self.pred)(x)) {
3525 None => self.finish(),
3527 let ret = Some(&self.v[..idx]);
3528 self.v = &self.v[idx + 1..];
3535 fn size_hint(&self) -> (usize, Option<usize>) {
3539 (1, Some(self.v.len() + 1))
3544 #[stable(feature = "rust1", since = "1.0.0")]
3545 impl<'a, T, P> DoubleEndedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
3547 fn next_back(&mut self) -> Option<&'a [T]> {
3548 if self.finished { return None; }
3550 match self.v.iter().rposition(|x| (self.pred)(x)) {
3551 None => self.finish(),
3553 let ret = Some(&self.v[idx + 1..]);
3554 self.v = &self.v[..idx];
3561 impl<'a, T, P> SplitIter for Split<'a, T, P> where P: FnMut(&T) -> bool {
3563 fn finish(&mut self) -> Option<&'a [T]> {
3564 if self.finished { None } else { self.finished = true; Some(self.v) }
3568 #[stable(feature = "fused", since = "1.26.0")]
3569 impl<T, P> FusedIterator for Split<'_, T, P> where P: FnMut(&T) -> bool {}
3571 /// An iterator over the subslices of the vector which are separated
3572 /// by elements that match `pred`.
3574 /// This struct is created by the [`split_mut`] method on [slices].
3576 /// [`split_mut`]: ../../std/primitive.slice.html#method.split_mut
3577 /// [slices]: ../../std/primitive.slice.html
3578 #[stable(feature = "rust1", since = "1.0.0")]
3579 pub struct SplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
3585 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3586 impl<T: fmt::Debug, P> fmt::Debug for SplitMut<'_, T, P> where P: FnMut(&T) -> bool {
3587 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3588 f.debug_struct("SplitMut")
3589 .field("v", &self.v)
3590 .field("finished", &self.finished)
3595 impl<'a, T, P> SplitIter for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3597 fn finish(&mut self) -> Option<&'a mut [T]> {
3601 self.finished = true;
3602 Some(mem::replace(&mut self.v, &mut []))
3607 #[stable(feature = "rust1", since = "1.0.0")]
3608 impl<'a, T, P> Iterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3609 type Item = &'a mut [T];
3612 fn next(&mut self) -> Option<&'a mut [T]> {
3613 if self.finished { return None; }
3615 let idx_opt = { // work around borrowck limitations
3616 let pred = &mut self.pred;
3617 self.v.iter().position(|x| (*pred)(x))
3620 None => self.finish(),
3622 let tmp = mem::replace(&mut self.v, &mut []);
3623 let (head, tail) = tmp.split_at_mut(idx);
3624 self.v = &mut tail[1..];
3631 fn size_hint(&self) -> (usize, Option<usize>) {
3635 // if the predicate doesn't match anything, we yield one slice
3636 // if it matches every element, we yield len+1 empty slices.
3637 (1, Some(self.v.len() + 1))
3642 #[stable(feature = "rust1", since = "1.0.0")]
3643 impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> where
3644 P: FnMut(&T) -> bool,
3647 fn next_back(&mut self) -> Option<&'a mut [T]> {
3648 if self.finished { return None; }
3650 let idx_opt = { // work around borrowck limitations
3651 let pred = &mut self.pred;
3652 self.v.iter().rposition(|x| (*pred)(x))
3655 None => self.finish(),
3657 let tmp = mem::replace(&mut self.v, &mut []);
3658 let (head, tail) = tmp.split_at_mut(idx);
3660 Some(&mut tail[1..])
3666 #[stable(feature = "fused", since = "1.26.0")]
3667 impl<T, P> FusedIterator for SplitMut<'_, T, P> where P: FnMut(&T) -> bool {}
3669 /// An iterator over subslices separated by elements that match a predicate
3670 /// function, starting from the end of the slice.
3672 /// This struct is created by the [`rsplit`] method on [slices].
3674 /// [`rsplit`]: ../../std/primitive.slice.html#method.rsplit
3675 /// [slices]: ../../std/primitive.slice.html
3676 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3677 #[derive(Clone)] // Is this correct, or does it incorrectly require `T: Clone`?
3678 pub struct RSplit<'a, T:'a, P> where P: FnMut(&T) -> bool {
3679 inner: Split<'a, T, P>
3682 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3683 impl<T: fmt::Debug, P> fmt::Debug for RSplit<'_, T, P> where P: FnMut(&T) -> bool {
3684 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3685 f.debug_struct("RSplit")
3686 .field("v", &self.inner.v)
3687 .field("finished", &self.inner.finished)
3692 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3693 impl<'a, T, P> Iterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3694 type Item = &'a [T];
3697 fn next(&mut self) -> Option<&'a [T]> {
3698 self.inner.next_back()
3702 fn size_hint(&self) -> (usize, Option<usize>) {
3703 self.inner.size_hint()
3707 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3708 impl<'a, T, P> DoubleEndedIterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3710 fn next_back(&mut self) -> Option<&'a [T]> {
3715 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3716 impl<'a, T, P> SplitIter for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3718 fn finish(&mut self) -> Option<&'a [T]> {
3723 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3724 impl<T, P> FusedIterator for RSplit<'_, T, P> where P: FnMut(&T) -> bool {}
3726 /// An iterator over the subslices of the vector which are separated
3727 /// by elements that match `pred`, starting from the end of the slice.
3729 /// This struct is created by the [`rsplit_mut`] method on [slices].
3731 /// [`rsplit_mut`]: ../../std/primitive.slice.html#method.rsplit_mut
3732 /// [slices]: ../../std/primitive.slice.html
3733 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3734 pub struct RSplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
3735 inner: SplitMut<'a, T, P>
3738 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3739 impl<T: fmt::Debug, P> fmt::Debug for RSplitMut<'_, T, P> where P: FnMut(&T) -> bool {
3740 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3741 f.debug_struct("RSplitMut")
3742 .field("v", &self.inner.v)
3743 .field("finished", &self.inner.finished)
3748 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3749 impl<'a, T, P> SplitIter for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3751 fn finish(&mut self) -> Option<&'a mut [T]> {
3756 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3757 impl<'a, T, P> Iterator for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3758 type Item = &'a mut [T];
3761 fn next(&mut self) -> Option<&'a mut [T]> {
3762 self.inner.next_back()
3766 fn size_hint(&self) -> (usize, Option<usize>) {
3767 self.inner.size_hint()
3771 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3772 impl<'a, T, P> DoubleEndedIterator for RSplitMut<'a, T, P> where
3773 P: FnMut(&T) -> bool,
3776 fn next_back(&mut self) -> Option<&'a mut [T]> {
3781 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3782 impl<T, P> FusedIterator for RSplitMut<'_, T, P> where P: FnMut(&T) -> bool {}
3784 /// An private iterator over subslices separated by elements that
3785 /// match a predicate function, splitting at most a fixed number of
3788 struct GenericSplitN<I> {
3793 impl<T, I: SplitIter<Item=T>> Iterator for GenericSplitN<I> {
3797 fn next(&mut self) -> Option<T> {
3800 1 => { self.count -= 1; self.iter.finish() }
3801 _ => { self.count -= 1; self.iter.next() }
3806 fn size_hint(&self) -> (usize, Option<usize>) {
3807 let (lower, upper_opt) = self.iter.size_hint();
3808 (lower, upper_opt.map(|upper| cmp::min(self.count, upper)))
3812 /// An iterator over subslices separated by elements that match a predicate
3813 /// function, limited to a given number of splits.
3815 /// This struct is created by the [`splitn`] method on [slices].
3817 /// [`splitn`]: ../../std/primitive.slice.html#method.splitn
3818 /// [slices]: ../../std/primitive.slice.html
3819 #[stable(feature = "rust1", since = "1.0.0")]
3820 pub struct SplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3821 inner: GenericSplitN<Split<'a, T, P>>
3824 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3825 impl<T: fmt::Debug, P> fmt::Debug for SplitN<'_, T, P> where P: FnMut(&T) -> bool {
3826 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3827 f.debug_struct("SplitN")
3828 .field("inner", &self.inner)
3833 /// An iterator over subslices separated by elements that match a
3834 /// predicate function, limited to a given number of splits, starting
3835 /// from the end of the slice.
3837 /// This struct is created by the [`rsplitn`] method on [slices].
3839 /// [`rsplitn`]: ../../std/primitive.slice.html#method.rsplitn
3840 /// [slices]: ../../std/primitive.slice.html
3841 #[stable(feature = "rust1", since = "1.0.0")]
3842 pub struct RSplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3843 inner: GenericSplitN<RSplit<'a, T, P>>
3846 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3847 impl<T: fmt::Debug, P> fmt::Debug for RSplitN<'_, T, P> where P: FnMut(&T) -> bool {
3848 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3849 f.debug_struct("RSplitN")
3850 .field("inner", &self.inner)
3855 /// An iterator over subslices separated by elements that match a predicate
3856 /// function, limited to a given number of splits.
3858 /// This struct is created by the [`splitn_mut`] method on [slices].
3860 /// [`splitn_mut`]: ../../std/primitive.slice.html#method.splitn_mut
3861 /// [slices]: ../../std/primitive.slice.html
3862 #[stable(feature = "rust1", since = "1.0.0")]
3863 pub struct SplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3864 inner: GenericSplitN<SplitMut<'a, T, P>>
3867 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3868 impl<T: fmt::Debug, P> fmt::Debug for SplitNMut<'_, T, P> where P: FnMut(&T) -> bool {
3869 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3870 f.debug_struct("SplitNMut")
3871 .field("inner", &self.inner)
3876 /// An iterator over subslices separated by elements that match a
3877 /// predicate function, limited to a given number of splits, starting
3878 /// from the end of the slice.
3880 /// This struct is created by the [`rsplitn_mut`] method on [slices].
3882 /// [`rsplitn_mut`]: ../../std/primitive.slice.html#method.rsplitn_mut
3883 /// [slices]: ../../std/primitive.slice.html
3884 #[stable(feature = "rust1", since = "1.0.0")]
3885 pub struct RSplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3886 inner: GenericSplitN<RSplitMut<'a, T, P>>
3889 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3890 impl<T: fmt::Debug, P> fmt::Debug for RSplitNMut<'_, T, P> where P: FnMut(&T) -> bool {
3891 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3892 f.debug_struct("RSplitNMut")
3893 .field("inner", &self.inner)
3898 macro_rules! forward_iterator {
3899 ($name:ident: $elem:ident, $iter_of:ty) => {
3900 #[stable(feature = "rust1", since = "1.0.0")]
3901 impl<'a, $elem, P> Iterator for $name<'a, $elem, P> where
3902 P: FnMut(&T) -> bool
3904 type Item = $iter_of;
3907 fn next(&mut self) -> Option<$iter_of> {
3912 fn size_hint(&self) -> (usize, Option<usize>) {
3913 self.inner.size_hint()
3917 #[stable(feature = "fused", since = "1.26.0")]
3918 impl<'a, $elem, P> FusedIterator for $name<'a, $elem, P>
3919 where P: FnMut(&T) -> bool {}
3923 forward_iterator! { SplitN: T, &'a [T] }
3924 forward_iterator! { RSplitN: T, &'a [T] }
3925 forward_iterator! { SplitNMut: T, &'a mut [T] }
3926 forward_iterator! { RSplitNMut: T, &'a mut [T] }
3928 /// An iterator over overlapping subslices of length `size`.
3930 /// This struct is created by the [`windows`] method on [slices].
3932 /// [`windows`]: ../../std/primitive.slice.html#method.windows
3933 /// [slices]: ../../std/primitive.slice.html
3935 #[stable(feature = "rust1", since = "1.0.0")]
3936 pub struct Windows<'a, T:'a> {
3941 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3942 #[stable(feature = "rust1", since = "1.0.0")]
3943 impl<T> Clone for Windows<'_, T> {
3944 fn clone(&self) -> Self {
3952 #[stable(feature = "rust1", since = "1.0.0")]
3953 impl<'a, T> Iterator for Windows<'a, T> {
3954 type Item = &'a [T];
3957 fn next(&mut self) -> Option<&'a [T]> {
3958 if self.size > self.v.len() {
3961 let ret = Some(&self.v[..self.size]);
3962 self.v = &self.v[1..];
3968 fn size_hint(&self) -> (usize, Option<usize>) {
3969 if self.size > self.v.len() {
3972 let size = self.v.len() - self.size + 1;
3978 fn count(self) -> usize {
3983 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3984 let (end, overflow) = self.size.overflowing_add(n);
3985 if end > self.v.len() || overflow {
3989 let nth = &self.v[n..end];
3990 self.v = &self.v[n+1..];
3996 fn last(self) -> Option<Self::Item> {
3997 if self.size > self.v.len() {
4000 let start = self.v.len() - self.size;
4001 Some(&self.v[start..])
4006 #[stable(feature = "rust1", since = "1.0.0")]
4007 impl<'a, T> DoubleEndedIterator for Windows<'a, T> {
4009 fn next_back(&mut self) -> Option<&'a [T]> {
4010 if self.size > self.v.len() {
4013 let ret = Some(&self.v[self.v.len()-self.size..]);
4014 self.v = &self.v[..self.v.len()-1];
4020 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
4021 let (end, overflow) = self.v.len().overflowing_sub(n);
4022 if end < self.size || overflow {
4026 let ret = &self.v[end-self.size..end];
4027 self.v = &self.v[..end-1];
4033 #[stable(feature = "rust1", since = "1.0.0")]
4034 impl<T> ExactSizeIterator for Windows<'_, T> {}
4036 #[unstable(feature = "trusted_len", issue = "37572")]
4037 unsafe impl<T> TrustedLen for Windows<'_, T> {}
4039 #[stable(feature = "fused", since = "1.26.0")]
4040 impl<T> FusedIterator for Windows<'_, T> {}
4043 unsafe impl<'a, T> TrustedRandomAccess for Windows<'a, T> {
4044 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
4045 from_raw_parts(self.v.as_ptr().add(i), self.size)
4047 fn may_have_side_effect() -> bool { false }
4050 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
4051 /// time), starting at the beginning of the slice.
4053 /// When the slice len is not evenly divided by the chunk size, the last slice
4054 /// of the iteration will be the remainder.
4056 /// This struct is created by the [`chunks`] method on [slices].
4058 /// [`chunks`]: ../../std/primitive.slice.html#method.chunks
4059 /// [slices]: ../../std/primitive.slice.html
4061 #[stable(feature = "rust1", since = "1.0.0")]
4062 pub struct Chunks<'a, T:'a> {
4067 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
4068 #[stable(feature = "rust1", since = "1.0.0")]
4069 impl<T> Clone for Chunks<'_, T> {
4070 fn clone(&self) -> Self {
4073 chunk_size: self.chunk_size,
4078 #[stable(feature = "rust1", since = "1.0.0")]
4079 impl<'a, T> Iterator for Chunks<'a, T> {
4080 type Item = &'a [T];
4083 fn next(&mut self) -> Option<&'a [T]> {
4084 if self.v.is_empty() {
4087 let chunksz = cmp::min(self.v.len(), self.chunk_size);
4088 let (fst, snd) = self.v.split_at(chunksz);
4095 fn size_hint(&self) -> (usize, Option<usize>) {
4096 if self.v.is_empty() {
4099 let n = self.v.len() / self.chunk_size;
4100 let rem = self.v.len() % self.chunk_size;
4101 let n = if rem > 0 { n+1 } else { n };
4107 fn count(self) -> usize {
4112 fn nth(&mut self, n: usize) -> Option<Self::Item> {
4113 let (start, overflow) = n.overflowing_mul(self.chunk_size);
4114 if start >= self.v.len() || overflow {
4118 let end = match start.checked_add(self.chunk_size) {
4119 Some(sum) => cmp::min(self.v.len(), sum),
4120 None => self.v.len(),
4122 let nth = &self.v[start..end];
4123 self.v = &self.v[end..];
4129 fn last(self) -> Option<Self::Item> {
4130 if self.v.is_empty() {
4133 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
4134 Some(&self.v[start..])
4139 #[stable(feature = "rust1", since = "1.0.0")]
4140 impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
4142 fn next_back(&mut self) -> Option<&'a [T]> {
4143 if self.v.is_empty() {
4146 let remainder = self.v.len() % self.chunk_size;
4147 let chunksz = if remainder != 0 { remainder } else { self.chunk_size };
4148 let (fst, snd) = self.v.split_at(self.v.len() - chunksz);
4155 #[stable(feature = "rust1", since = "1.0.0")]
4156 impl<T> ExactSizeIterator for Chunks<'_, T> {}
4158 #[unstable(feature = "trusted_len", issue = "37572")]
4159 unsafe impl<T> TrustedLen for Chunks<'_, T> {}
4161 #[stable(feature = "fused", since = "1.26.0")]
4162 impl<T> FusedIterator for Chunks<'_, T> {}
4165 unsafe impl<'a, T> TrustedRandomAccess for Chunks<'a, T> {
4166 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
4167 let start = i * self.chunk_size;
4168 let end = match start.checked_add(self.chunk_size) {
4169 None => self.v.len(),
4170 Some(end) => cmp::min(end, self.v.len()),
4172 from_raw_parts(self.v.as_ptr().add(start), end - start)
4174 fn may_have_side_effect() -> bool { false }
4177 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
4178 /// elements at a time), starting at the beginning of the slice.
4180 /// When the slice len is not evenly divided by the chunk size, the last slice
4181 /// of the iteration will be the remainder.
4183 /// This struct is created by the [`chunks_mut`] method on [slices].
4185 /// [`chunks_mut`]: ../../std/primitive.slice.html#method.chunks_mut
4186 /// [slices]: ../../std/primitive.slice.html
4188 #[stable(feature = "rust1", since = "1.0.0")]
4189 pub struct ChunksMut<'a, T:'a> {
4194 #[stable(feature = "rust1", since = "1.0.0")]
4195 impl<'a, T> Iterator for ChunksMut<'a, T> {
4196 type Item = &'a mut [T];
4199 fn next(&mut self) -> Option<&'a mut [T]> {
4200 if self.v.is_empty() {
4203 let sz = cmp::min(self.v.len(), self.chunk_size);
4204 let tmp = mem::replace(&mut self.v, &mut []);
4205 let (head, tail) = tmp.split_at_mut(sz);
4212 fn size_hint(&self) -> (usize, Option<usize>) {
4213 if self.v.is_empty() {
4216 let n = self.v.len() / self.chunk_size;
4217 let rem = self.v.len() % self.chunk_size;
4218 let n = if rem > 0 { n + 1 } else { n };
4224 fn count(self) -> usize {
4229 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
4230 let (start, overflow) = n.overflowing_mul(self.chunk_size);
4231 if start >= self.v.len() || overflow {
4235 let end = match start.checked_add(self.chunk_size) {
4236 Some(sum) => cmp::min(self.v.len(), sum),
4237 None => self.v.len(),
4239 let tmp = mem::replace(&mut self.v, &mut []);
4240 let (head, tail) = tmp.split_at_mut(end);
4241 let (_, nth) = head.split_at_mut(start);
4248 fn last(self) -> Option<Self::Item> {
4249 if self.v.is_empty() {
4252 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
4253 Some(&mut self.v[start..])
4258 #[stable(feature = "rust1", since = "1.0.0")]
4259 impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
4261 fn next_back(&mut self) -> Option<&'a mut [T]> {
4262 if self.v.is_empty() {
4265 let remainder = self.v.len() % self.chunk_size;
4266 let sz = if remainder != 0 { remainder } else { self.chunk_size };
4267 let tmp = mem::replace(&mut self.v, &mut []);
4268 let tmp_len = tmp.len();
4269 let (head, tail) = tmp.split_at_mut(tmp_len - sz);
4276 #[stable(feature = "rust1", since = "1.0.0")]
4277 impl<T> ExactSizeIterator for ChunksMut<'_, T> {}
4279 #[unstable(feature = "trusted_len", issue = "37572")]
4280 unsafe impl<T> TrustedLen for ChunksMut<'_, T> {}
4282 #[stable(feature = "fused", since = "1.26.0")]
4283 impl<T> FusedIterator for ChunksMut<'_, T> {}
4286 unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> {
4287 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
4288 let start = i * self.chunk_size;
4289 let end = match start.checked_add(self.chunk_size) {
4290 None => self.v.len(),
4291 Some(end) => cmp::min(end, self.v.len()),
4293 from_raw_parts_mut(self.v.as_mut_ptr().add(start), end - start)
4295 fn may_have_side_effect() -> bool { false }
4298 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
4299 /// time), starting at the beginning of the slice.
4301 /// When the slice len is not evenly divided by the chunk size, the last
4302 /// up to `chunk_size-1` elements will be omitted but can be retrieved from
4303 /// the [`remainder`] function from the iterator.
4305 /// This struct is created by the [`chunks_exact`] method on [slices].
4307 /// [`chunks_exact`]: ../../std/primitive.slice.html#method.chunks_exact
4308 /// [`remainder`]: ../../std/slice/struct.ChunksExact.html#method.remainder
4309 /// [slices]: ../../std/primitive.slice.html
4311 #[stable(feature = "chunks_exact", since = "1.31.0")]
4312 pub struct ChunksExact<'a, T:'a> {
4318 impl<'a, T> ChunksExact<'a, T> {
4319 /// Returns the remainder of the original slice that is not going to be
4320 /// returned by the iterator. The returned slice has at most `chunk_size-1`
4322 #[stable(feature = "chunks_exact", since = "1.31.0")]
4323 pub fn remainder(&self) -> &'a [T] {
4328 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
4329 #[stable(feature = "chunks_exact", since = "1.31.0")]
4330 impl<T> Clone for ChunksExact<'_, T> {
4331 fn clone(&self) -> Self {
4335 chunk_size: self.chunk_size,
4340 #[stable(feature = "chunks_exact", since = "1.31.0")]
4341 impl<'a, T> Iterator for ChunksExact<'a, T> {
4342 type Item = &'a [T];
4345 fn next(&mut self) -> Option<&'a [T]> {
4346 if self.v.len() < self.chunk_size {
4349 let (fst, snd) = self.v.split_at(self.chunk_size);
4356 fn size_hint(&self) -> (usize, Option<usize>) {
4357 let n = self.v.len() / self.chunk_size;
4362 fn count(self) -> usize {
4367 fn nth(&mut self, n: usize) -> Option<Self::Item> {
4368 let (start, overflow) = n.overflowing_mul(self.chunk_size);
4369 if start >= self.v.len() || overflow {
4373 let (_, snd) = self.v.split_at(start);
4380 fn last(mut self) -> Option<Self::Item> {
4385 #[stable(feature = "chunks_exact", since = "1.31.0")]
4386 impl<'a, T> DoubleEndedIterator for ChunksExact<'a, T> {
4388 fn next_back(&mut self) -> Option<&'a [T]> {
4389 if self.v.len() < self.chunk_size {
4392 let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size);
4399 #[stable(feature = "chunks_exact", since = "1.31.0")]
4400 impl<T> ExactSizeIterator for ChunksExact<'_, T> {
4401 fn is_empty(&self) -> bool {
4406 #[unstable(feature = "trusted_len", issue = "37572")]
4407 unsafe impl<T> TrustedLen for ChunksExact<'_, T> {}
4409 #[stable(feature = "chunks_exact", since = "1.31.0")]
4410 impl<T> FusedIterator for ChunksExact<'_, T> {}
4413 #[stable(feature = "chunks_exact", since = "1.31.0")]
4414 unsafe impl<'a, T> TrustedRandomAccess for ChunksExact<'a, T> {
4415 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
4416 let start = i * self.chunk_size;
4417 from_raw_parts(self.v.as_ptr().add(start), self.chunk_size)
4419 fn may_have_side_effect() -> bool { false }
4422 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
4423 /// elements at a time), starting at the beginning of the slice.
4425 /// When the slice len is not evenly divided by the chunk size, the last up to
4426 /// `chunk_size-1` elements will be omitted but can be retrieved from the
4427 /// [`into_remainder`] function from the iterator.
4429 /// This struct is created by the [`chunks_exact_mut`] method on [slices].
4431 /// [`chunks_exact_mut`]: ../../std/primitive.slice.html#method.chunks_exact_mut
4432 /// [`into_remainder`]: ../../std/slice/struct.ChunksExactMut.html#method.into_remainder
4433 /// [slices]: ../../std/primitive.slice.html
4435 #[stable(feature = "chunks_exact", since = "1.31.0")]
4436 pub struct ChunksExactMut<'a, T:'a> {
4442 impl<'a, T> ChunksExactMut<'a, T> {
4443 /// Returns the remainder of the original slice that is not going to be
4444 /// returned by the iterator. The returned slice has at most `chunk_size-1`
4446 #[stable(feature = "chunks_exact", since = "1.31.0")]
4447 pub fn into_remainder(self) -> &'a mut [T] {
4452 #[stable(feature = "chunks_exact", since = "1.31.0")]
4453 impl<'a, T> Iterator for ChunksExactMut<'a, T> {
4454 type Item = &'a mut [T];
4457 fn next(&mut self) -> Option<&'a mut [T]> {
4458 if self.v.len() < self.chunk_size {
4461 let tmp = mem::replace(&mut self.v, &mut []);
4462 let (head, tail) = tmp.split_at_mut(self.chunk_size);
4469 fn size_hint(&self) -> (usize, Option<usize>) {
4470 let n = self.v.len() / self.chunk_size;
4475 fn count(self) -> usize {
4480 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
4481 let (start, overflow) = n.overflowing_mul(self.chunk_size);
4482 if start >= self.v.len() || overflow {
4486 let tmp = mem::replace(&mut self.v, &mut []);
4487 let (_, snd) = tmp.split_at_mut(start);
4494 fn last(mut self) -> Option<Self::Item> {
4499 #[stable(feature = "chunks_exact", since = "1.31.0")]
4500 impl<'a, T> DoubleEndedIterator for ChunksExactMut<'a, T> {
4502 fn next_back(&mut self) -> Option<&'a mut [T]> {
4503 if self.v.len() < self.chunk_size {
4506 let tmp = mem::replace(&mut self.v, &mut []);
4507 let tmp_len = tmp.len();
4508 let (head, tail) = tmp.split_at_mut(tmp_len - self.chunk_size);
4515 #[stable(feature = "chunks_exact", since = "1.31.0")]
4516 impl<T> ExactSizeIterator for ChunksExactMut<'_, T> {
4517 fn is_empty(&self) -> bool {
4522 #[unstable(feature = "trusted_len", issue = "37572")]
4523 unsafe impl<T> TrustedLen for ChunksExactMut<'_, T> {}
4525 #[stable(feature = "chunks_exact", since = "1.31.0")]
4526 impl<T> FusedIterator for ChunksExactMut<'_, T> {}
4529 #[stable(feature = "chunks_exact", since = "1.31.0")]
4530 unsafe impl<'a, T> TrustedRandomAccess for ChunksExactMut<'a, T> {
4531 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
4532 let start = i * self.chunk_size;
4533 from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size)
4535 fn may_have_side_effect() -> bool { false }
4538 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
4539 /// time), starting at the end of the slice.
4541 /// When the slice len is not evenly divided by the chunk size, the last slice
4542 /// of the iteration will be the remainder.
4544 /// This struct is created by the [`rchunks`] method on [slices].
4546 /// [`rchunks`]: ../../std/primitive.slice.html#method.rchunks
4547 /// [slices]: ../../std/primitive.slice.html
4549 #[stable(feature = "rchunks", since = "1.31.0")]
4550 pub struct RChunks<'a, T:'a> {
4555 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
4556 #[stable(feature = "rchunks", since = "1.31.0")]
4557 impl<T> Clone for RChunks<'_, T> {
4558 fn clone(&self) -> Self {
4561 chunk_size: self.chunk_size,
4566 #[stable(feature = "rchunks", since = "1.31.0")]
4567 impl<'a, T> Iterator for RChunks<'a, T> {
4568 type Item = &'a [T];
4571 fn next(&mut self) -> Option<&'a [T]> {
4572 if self.v.is_empty() {
4575 let chunksz = cmp::min(self.v.len(), self.chunk_size);
4576 let (fst, snd) = self.v.split_at(self.v.len() - chunksz);
4583 fn size_hint(&self) -> (usize, Option<usize>) {
4584 if self.v.is_empty() {
4587 let n = self.v.len() / self.chunk_size;
4588 let rem = self.v.len() % self.chunk_size;
4589 let n = if rem > 0 { n+1 } else { n };
4595 fn count(self) -> usize {
4600 fn nth(&mut self, n: usize) -> Option<Self::Item> {
4601 let (end, overflow) = n.overflowing_mul(self.chunk_size);
4602 if end >= self.v.len() || overflow {
4606 // Can't underflow because of the check above
4607 let end = self.v.len() - end;
4608 let start = match end.checked_sub(self.chunk_size) {
4612 let nth = &self.v[start..end];
4613 self.v = &self.v[0..start];
4619 fn last(self) -> Option<Self::Item> {
4620 if self.v.is_empty() {
4623 let rem = self.v.len() % self.chunk_size;
4624 let end = if rem == 0 { self.chunk_size } else { rem };
4625 Some(&self.v[0..end])
4630 #[stable(feature = "rchunks", since = "1.31.0")]
4631 impl<'a, T> DoubleEndedIterator for RChunks<'a, T> {
4633 fn next_back(&mut self) -> Option<&'a [T]> {
4634 if self.v.is_empty() {
4637 let remainder = self.v.len() % self.chunk_size;
4638 let chunksz = if remainder != 0 { remainder } else { self.chunk_size };
4639 let (fst, snd) = self.v.split_at(chunksz);
4646 #[stable(feature = "rchunks", since = "1.31.0")]
4647 impl<T> ExactSizeIterator for RChunks<'_, T> {}
4649 #[unstable(feature = "trusted_len", issue = "37572")]
4650 unsafe impl<T> TrustedLen for RChunks<'_, T> {}
4652 #[stable(feature = "rchunks", since = "1.31.0")]
4653 impl<T> FusedIterator for RChunks<'_, T> {}
4656 #[stable(feature = "rchunks", since = "1.31.0")]
4657 unsafe impl<'a, T> TrustedRandomAccess for RChunks<'a, T> {
4658 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
4659 let end = self.v.len() - i * self.chunk_size;
4660 let start = match end.checked_sub(self.chunk_size) {
4662 Some(start) => start,
4664 from_raw_parts(self.v.as_ptr().add(start), end - start)
4666 fn may_have_side_effect() -> bool { false }
4669 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
4670 /// elements at a time), starting at the end of the slice.
4672 /// When the slice len is not evenly divided by the chunk size, the last slice
4673 /// of the iteration will be the remainder.
4675 /// This struct is created by the [`rchunks_mut`] method on [slices].
4677 /// [`rchunks_mut`]: ../../std/primitive.slice.html#method.rchunks_mut
4678 /// [slices]: ../../std/primitive.slice.html
4680 #[stable(feature = "rchunks", since = "1.31.0")]
4681 pub struct RChunksMut<'a, T:'a> {
4686 #[stable(feature = "rchunks", since = "1.31.0")]
4687 impl<'a, T> Iterator for RChunksMut<'a, T> {
4688 type Item = &'a mut [T];
4691 fn next(&mut self) -> Option<&'a mut [T]> {
4692 if self.v.is_empty() {
4695 let sz = cmp::min(self.v.len(), self.chunk_size);
4696 let tmp = mem::replace(&mut self.v, &mut []);
4697 let tmp_len = tmp.len();
4698 let (head, tail) = tmp.split_at_mut(tmp_len - sz);
4705 fn size_hint(&self) -> (usize, Option<usize>) {
4706 if self.v.is_empty() {
4709 let n = self.v.len() / self.chunk_size;
4710 let rem = self.v.len() % self.chunk_size;
4711 let n = if rem > 0 { n + 1 } else { n };
4717 fn count(self) -> usize {
4722 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
4723 let (end, overflow) = n.overflowing_mul(self.chunk_size);
4724 if end >= self.v.len() || overflow {
4728 // Can't underflow because of the check above
4729 let end = self.v.len() - end;
4730 let start = match end.checked_sub(self.chunk_size) {
4734 let tmp = mem::replace(&mut self.v, &mut []);
4735 let (head, tail) = tmp.split_at_mut(start);
4736 let (nth, _) = tail.split_at_mut(end - start);
4743 fn last(self) -> Option<Self::Item> {
4744 if self.v.is_empty() {
4747 let rem = self.v.len() % self.chunk_size;
4748 let end = if rem == 0 { self.chunk_size } else { rem };
4749 Some(&mut self.v[0..end])
4754 #[stable(feature = "rchunks", since = "1.31.0")]
4755 impl<'a, T> DoubleEndedIterator for RChunksMut<'a, T> {
4757 fn next_back(&mut self) -> Option<&'a mut [T]> {
4758 if self.v.is_empty() {
4761 let remainder = self.v.len() % self.chunk_size;
4762 let sz = if remainder != 0 { remainder } else { self.chunk_size };
4763 let tmp = mem::replace(&mut self.v, &mut []);
4764 let (head, tail) = tmp.split_at_mut(sz);
4771 #[stable(feature = "rchunks", since = "1.31.0")]
4772 impl<T> ExactSizeIterator for RChunksMut<'_, T> {}
4774 #[unstable(feature = "trusted_len", issue = "37572")]
4775 unsafe impl<T> TrustedLen for RChunksMut<'_, T> {}
4777 #[stable(feature = "rchunks", since = "1.31.0")]
4778 impl<T> FusedIterator for RChunksMut<'_, T> {}
4781 #[stable(feature = "rchunks", since = "1.31.0")]
4782 unsafe impl<'a, T> TrustedRandomAccess for RChunksMut<'a, T> {
4783 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
4784 let end = self.v.len() - i * self.chunk_size;
4785 let start = match end.checked_sub(self.chunk_size) {
4787 Some(start) => start,
4789 from_raw_parts_mut(self.v.as_mut_ptr().add(start), end - start)
4791 fn may_have_side_effect() -> bool { false }
4794 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
4795 /// time), starting at the end of the slice.
4797 /// When the slice len is not evenly divided by the chunk size, the last
4798 /// up to `chunk_size-1` elements will be omitted but can be retrieved from
4799 /// the [`remainder`] function from the iterator.
4801 /// This struct is created by the [`rchunks_exact`] method on [slices].
4803 /// [`rchunks_exact`]: ../../std/primitive.slice.html#method.rchunks_exact
4804 /// [`remainder`]: ../../std/slice/struct.ChunksExact.html#method.remainder
4805 /// [slices]: ../../std/primitive.slice.html
4807 #[stable(feature = "rchunks", since = "1.31.0")]
4808 pub struct RChunksExact<'a, T:'a> {
4814 impl<'a, T> RChunksExact<'a, T> {
4815 /// Returns the remainder of the original slice that is not going to be
4816 /// returned by the iterator. The returned slice has at most `chunk_size-1`
4818 #[stable(feature = "rchunks", since = "1.31.0")]
4819 pub fn remainder(&self) -> &'a [T] {
4824 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
4825 #[stable(feature = "rchunks", since = "1.31.0")]
4826 impl<'a, T> Clone for RChunksExact<'a, T> {
4827 fn clone(&self) -> RChunksExact<'a, T> {
4831 chunk_size: self.chunk_size,
4836 #[stable(feature = "rchunks", since = "1.31.0")]
4837 impl<'a, T> Iterator for RChunksExact<'a, T> {
4838 type Item = &'a [T];
4841 fn next(&mut self) -> Option<&'a [T]> {
4842 if self.v.len() < self.chunk_size {
4845 let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size);
4852 fn size_hint(&self) -> (usize, Option<usize>) {
4853 let n = self.v.len() / self.chunk_size;
4858 fn count(self) -> usize {
4863 fn nth(&mut self, n: usize) -> Option<Self::Item> {
4864 let (end, overflow) = n.overflowing_mul(self.chunk_size);
4865 if end >= self.v.len() || overflow {
4869 let (fst, _) = self.v.split_at(self.v.len() - end);
4876 fn last(mut self) -> Option<Self::Item> {
4881 #[stable(feature = "rchunks", since = "1.31.0")]
4882 impl<'a, T> DoubleEndedIterator for RChunksExact<'a, T> {
4884 fn next_back(&mut self) -> Option<&'a [T]> {
4885 if self.v.len() < self.chunk_size {
4888 let (fst, snd) = self.v.split_at(self.chunk_size);
4895 #[stable(feature = "rchunks", since = "1.31.0")]
4896 impl<'a, T> ExactSizeIterator for RChunksExact<'a, T> {
4897 fn is_empty(&self) -> bool {
4902 #[unstable(feature = "trusted_len", issue = "37572")]
4903 unsafe impl<T> TrustedLen for RChunksExact<'_, T> {}
4905 #[stable(feature = "rchunks", since = "1.31.0")]
4906 impl<T> FusedIterator for RChunksExact<'_, T> {}
4909 #[stable(feature = "rchunks", since = "1.31.0")]
4910 unsafe impl<'a, T> TrustedRandomAccess for RChunksExact<'a, T> {
4911 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
4912 let end = self.v.len() - i * self.chunk_size;
4913 let start = end - self.chunk_size;
4914 from_raw_parts(self.v.as_ptr().add(start), self.chunk_size)
4916 fn may_have_side_effect() -> bool { false }
4919 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
4920 /// elements at a time), starting at the end of the slice.
4922 /// When the slice len is not evenly divided by the chunk size, the last up to
4923 /// `chunk_size-1` elements will be omitted but can be retrieved from the
4924 /// [`into_remainder`] function from the iterator.
4926 /// This struct is created by the [`rchunks_exact_mut`] method on [slices].
4928 /// [`rchunks_exact_mut`]: ../../std/primitive.slice.html#method.rchunks_exact_mut
4929 /// [`into_remainder`]: ../../std/slice/struct.ChunksExactMut.html#method.into_remainder
4930 /// [slices]: ../../std/primitive.slice.html
4932 #[stable(feature = "rchunks", since = "1.31.0")]
4933 pub struct RChunksExactMut<'a, T:'a> {
4939 impl<'a, T> RChunksExactMut<'a, T> {
4940 /// Returns the remainder of the original slice that is not going to be
4941 /// returned by the iterator. The returned slice has at most `chunk_size-1`
4943 #[stable(feature = "rchunks", since = "1.31.0")]
4944 pub fn into_remainder(self) -> &'a mut [T] {
4949 #[stable(feature = "rchunks", since = "1.31.0")]
4950 impl<'a, T> Iterator for RChunksExactMut<'a, T> {
4951 type Item = &'a mut [T];
4954 fn next(&mut self) -> Option<&'a mut [T]> {
4955 if self.v.len() < self.chunk_size {
4958 let tmp = mem::replace(&mut self.v, &mut []);
4959 let tmp_len = tmp.len();
4960 let (head, tail) = tmp.split_at_mut(tmp_len - self.chunk_size);
4967 fn size_hint(&self) -> (usize, Option<usize>) {
4968 let n = self.v.len() / self.chunk_size;
4973 fn count(self) -> usize {
4978 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
4979 let (end, overflow) = n.overflowing_mul(self.chunk_size);
4980 if end >= self.v.len() || overflow {
4984 let tmp = mem::replace(&mut self.v, &mut []);
4985 let tmp_len = tmp.len();
4986 let (fst, _) = tmp.split_at_mut(tmp_len - end);
4993 fn last(mut self) -> Option<Self::Item> {
4998 #[stable(feature = "rchunks", since = "1.31.0")]
4999 impl<'a, T> DoubleEndedIterator for RChunksExactMut<'a, T> {
5001 fn next_back(&mut self) -> Option<&'a mut [T]> {
5002 if self.v.len() < self.chunk_size {
5005 let tmp = mem::replace(&mut self.v, &mut []);
5006 let (head, tail) = tmp.split_at_mut(self.chunk_size);
5013 #[stable(feature = "rchunks", since = "1.31.0")]
5014 impl<T> ExactSizeIterator for RChunksExactMut<'_, T> {
5015 fn is_empty(&self) -> bool {
5020 #[unstable(feature = "trusted_len", issue = "37572")]
5021 unsafe impl<T> TrustedLen for RChunksExactMut<'_, T> {}
5023 #[stable(feature = "rchunks", since = "1.31.0")]
5024 impl<T> FusedIterator for RChunksExactMut<'_, T> {}
5027 #[stable(feature = "rchunks", since = "1.31.0")]
5028 unsafe impl<'a, T> TrustedRandomAccess for RChunksExactMut<'a, T> {
5029 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
5030 let end = self.v.len() - i * self.chunk_size;
5031 let start = end - self.chunk_size;
5032 from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size)
5034 fn may_have_side_effect() -> bool { false }
5041 /// Forms a slice from a pointer and a length.
5043 /// The `len` argument is the number of **elements**, not the number of bytes.
5047 /// This function is unsafe as there is no guarantee that the given pointer is
5048 /// valid for `len` elements, nor whether the lifetime inferred is a suitable
5049 /// lifetime for the returned slice.
5051 /// `data` must be non-null and aligned, even for zero-length slices. One
5052 /// reason for this is that enum layout optimizations may rely on references
5053 /// (including slices of any length) being aligned and non-null to distinguish
5054 /// them from other data. You can obtain a pointer that is usable as `data`
5055 /// for zero-length slices using [`NonNull::dangling()`].
5057 /// The total size of the slice must be no larger than `isize::MAX` **bytes**
5058 /// in memory. See the safety documentation of [`pointer::offset`].
5062 /// The lifetime for the returned slice is inferred from its usage. To
5063 /// prevent accidental misuse, it's suggested to tie the lifetime to whichever
5064 /// source lifetime is safe in the context, such as by providing a helper
5065 /// function taking the lifetime of a host value for the slice, or by explicit
5073 /// // manifest a slice for a single element
5075 /// let ptr = &x as *const _;
5076 /// let slice = unsafe { slice::from_raw_parts(ptr, 1) };
5077 /// assert_eq!(slice[0], 42);
5080 /// [`NonNull::dangling()`]: ../../std/ptr/struct.NonNull.html#method.dangling
5081 /// [`pointer::offset`]: ../../std/primitive.pointer.html#method.offset
5083 #[stable(feature = "rust1", since = "1.0.0")]
5084 pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
5085 debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
5086 debug_assert!(mem::size_of::<T>().saturating_mul(len) <= isize::MAX as usize,
5087 "attempt to create slice covering half the address space");
5088 Repr { raw: FatPtr { data, len } }.rust
5091 /// Performs the same functionality as [`from_raw_parts`], except that a
5092 /// mutable slice is returned.
5094 /// This function is unsafe for the same reasons as [`from_raw_parts`], as well
5095 /// as not being able to provide a non-aliasing guarantee of the returned
5096 /// mutable slice. `data` must be non-null and aligned even for zero-length
5097 /// slices as with [`from_raw_parts`]. The total size of the slice must be no
5098 /// larger than `isize::MAX` **bytes** in memory.
5100 /// See the documentation of [`from_raw_parts`] for more details.
5102 /// [`from_raw_parts`]: ../../std/slice/fn.from_raw_parts.html
5104 #[stable(feature = "rust1", since = "1.0.0")]
5105 pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] {
5106 debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
5107 debug_assert!(mem::size_of::<T>().saturating_mul(len) <= isize::MAX as usize,
5108 "attempt to create slice covering half the address space");
5109 Repr { raw: FatPtr { data, len } }.rust_mut
5112 /// Converts a reference to T into a slice of length 1 (without copying).
5113 #[stable(feature = "from_ref", since = "1.28.0")]
5114 pub fn from_ref<T>(s: &T) -> &[T] {
5116 from_raw_parts(s, 1)
5120 /// Converts a reference to T into a slice of length 1 (without copying).
5121 #[stable(feature = "from_ref", since = "1.28.0")]
5122 pub fn from_mut<T>(s: &mut T) -> &mut [T] {
5124 from_raw_parts_mut(s, 1)
5128 // This function is public only because there is no other way to unit test heapsort.
5129 #[unstable(feature = "sort_internals", reason = "internal to sort module", issue = "0")]
5131 pub fn heapsort<T, F>(v: &mut [T], mut is_less: F)
5132 where F: FnMut(&T, &T) -> bool
5134 sort::heapsort(v, &mut is_less);
5138 // Comparison traits
5142 /// Calls implementation provided memcmp.
5144 /// Interprets the data as u8.
5146 /// Returns 0 for equal, < 0 for less than and > 0 for greater
5148 // FIXME(#32610): Return type should be c_int
5149 fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32;
5152 #[stable(feature = "rust1", since = "1.0.0")]
5153 impl<A, B> PartialEq<[B]> for [A] where A: PartialEq<B> {
5154 fn eq(&self, other: &[B]) -> bool {
5155 SlicePartialEq::equal(self, other)
5158 fn ne(&self, other: &[B]) -> bool {
5159 SlicePartialEq::not_equal(self, other)
5163 #[stable(feature = "rust1", since = "1.0.0")]
5164 impl<T: Eq> Eq for [T] {}
5166 /// Implements comparison of vectors lexicographically.
5167 #[stable(feature = "rust1", since = "1.0.0")]
5168 impl<T: Ord> Ord for [T] {
5169 fn cmp(&self, other: &[T]) -> Ordering {
5170 SliceOrd::compare(self, other)
5174 /// Implements comparison of vectors lexicographically.
5175 #[stable(feature = "rust1", since = "1.0.0")]
5176 impl<T: PartialOrd> PartialOrd for [T] {
5177 fn partial_cmp(&self, other: &[T]) -> Option<Ordering> {
5178 SlicePartialOrd::partial_compare(self, other)
5183 // intermediate trait for specialization of slice's PartialEq
5184 trait SlicePartialEq<B> {
5185 fn equal(&self, other: &[B]) -> bool;
5187 fn not_equal(&self, other: &[B]) -> bool { !self.equal(other) }
5190 // Generic slice equality
5191 impl<A, B> SlicePartialEq<B> for [A]
5192 where A: PartialEq<B>
5194 default fn equal(&self, other: &[B]) -> bool {
5195 if self.len() != other.len() {
5199 for i in 0..self.len() {
5200 if !self[i].eq(&other[i]) {
5209 // Use memcmp for bytewise equality when the types allow
5210 impl<A> SlicePartialEq<A> for [A]
5211 where A: PartialEq<A> + BytewiseEquality
5213 fn equal(&self, other: &[A]) -> bool {
5214 if self.len() != other.len() {
5217 if self.as_ptr() == other.as_ptr() {
5221 let size = mem::size_of_val(self);
5222 memcmp(self.as_ptr() as *const u8,
5223 other.as_ptr() as *const u8, size) == 0
5229 // intermediate trait for specialization of slice's PartialOrd
5230 trait SlicePartialOrd<B> {
5231 fn partial_compare(&self, other: &[B]) -> Option<Ordering>;
5234 impl<A> SlicePartialOrd<A> for [A]
5237 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
5238 let l = cmp::min(self.len(), other.len());
5240 // Slice to the loop iteration range to enable bound check
5241 // elimination in the compiler
5242 let lhs = &self[..l];
5243 let rhs = &other[..l];
5246 match lhs[i].partial_cmp(&rhs[i]) {
5247 Some(Ordering::Equal) => (),
5248 non_eq => return non_eq,
5252 self.len().partial_cmp(&other.len())
5256 impl<A> SlicePartialOrd<A> for [A]
5259 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
5260 Some(SliceOrd::compare(self, other))
5265 // intermediate trait for specialization of slice's Ord
5267 fn compare(&self, other: &[B]) -> Ordering;
5270 impl<A> SliceOrd<A> for [A]
5273 default fn compare(&self, other: &[A]) -> Ordering {
5274 let l = cmp::min(self.len(), other.len());
5276 // Slice to the loop iteration range to enable bound check
5277 // elimination in the compiler
5278 let lhs = &self[..l];
5279 let rhs = &other[..l];
5282 match lhs[i].cmp(&rhs[i]) {
5283 Ordering::Equal => (),
5284 non_eq => return non_eq,
5288 self.len().cmp(&other.len())
5292 // memcmp compares a sequence of unsigned bytes lexicographically.
5293 // this matches the order we want for [u8], but no others (not even [i8]).
5294 impl SliceOrd<u8> for [u8] {
5296 fn compare(&self, other: &[u8]) -> Ordering {
5297 let order = unsafe {
5298 memcmp(self.as_ptr(), other.as_ptr(),
5299 cmp::min(self.len(), other.len()))
5302 self.len().cmp(&other.len())
5303 } else if order < 0 {
5312 /// Trait implemented for types that can be compared for equality using
5313 /// their bytewise representation
5314 trait BytewiseEquality { }
5316 macro_rules! impl_marker_for {
5317 ($traitname:ident, $($ty:ty)*) => {
5319 impl $traitname for $ty { }
5324 impl_marker_for!(BytewiseEquality,
5325 u8 i8 u16 i16 u32 i32 u64 i64 usize isize char bool);
5328 unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {
5329 unsafe fn get_unchecked(&mut self, i: usize) -> &'a T {
5332 fn may_have_side_effect() -> bool { false }
5336 unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> {
5337 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut T {
5338 &mut *self.ptr.add(i)
5340 fn may_have_side_effect() -> bool { false }
5343 trait SliceContains: Sized {
5344 fn slice_contains(&self, x: &[Self]) -> bool;
5347 impl<T> SliceContains for T where T: PartialEq {
5348 default fn slice_contains(&self, x: &[Self]) -> bool {
5349 x.iter().any(|y| *y == *self)
5353 impl SliceContains for u8 {
5354 fn slice_contains(&self, x: &[Self]) -> bool {
5355 memchr::memchr(*self, x).is_some()
5359 impl SliceContains for i8 {
5360 fn slice_contains(&self, x: &[Self]) -> bool {
5361 let byte = *self as u8;
5362 let bytes: &[u8] = unsafe { from_raw_parts(x.as_ptr() as *const u8, x.len()) };
5363 memchr::memchr(byte, bytes).is_some()