1 // Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Slice management and manipulation
13 //! For more details see [`std::slice`].
15 //! [`std::slice`]: ../../std/slice/index.html
17 #![stable(feature = "rust1", since = "1.0.0")]
19 // How this module is organized.
21 // The library infrastructure for slices is fairly messy. There's
22 // a lot of stuff defined here. Let's keep it clean.
24 // The layout of this file is thus:
26 // * Inherent methods. This is where most of the slice API resides.
27 // * Implementations of a few common traits with important slice ops.
28 // * Definitions of a bunch of iterators.
30 // * The `raw` and `bytes` submodules.
31 // * Boilerplate trait implementations.
33 use cmp::Ordering::{self, Less, Equal, Greater};
36 use intrinsics::assume;
38 use ops::{FnMut, Try, self};
40 use option::Option::{None, Some};
42 use result::Result::{Ok, Err};
45 use marker::{Copy, Send, Sync, Sized, self};
46 use iter_private::TrustedRandomAccess;
48 #[unstable(feature = "slice_internals", issue = "0",
49 reason = "exposed from core to be reused in std; use the memchr crate")]
50 /// Pure rust memchr implementation, taken from rust-memchr
57 union Repr<'a, T: 'a> {
59 rust_mut: &'a mut [T],
76 /// Returns the number of elements in the slice.
81 /// let a = [1, 2, 3];
82 /// assert_eq!(a.len(), 3);
84 #[stable(feature = "rust1", since = "1.0.0")]
86 #[rustc_const_unstable(feature = "const_slice_len")]
87 pub const fn len(&self) -> usize {
89 Repr { rust: self }.raw.len
93 /// Returns `true` if the slice has a length of 0.
98 /// let a = [1, 2, 3];
99 /// assert!(!a.is_empty());
101 #[stable(feature = "rust1", since = "1.0.0")]
103 #[rustc_const_unstable(feature = "const_slice_len")]
104 pub const fn is_empty(&self) -> bool {
108 /// Returns the first element of the slice, or `None` if it is empty.
113 /// let v = [10, 40, 30];
114 /// assert_eq!(Some(&10), v.first());
116 /// let w: &[i32] = &[];
117 /// assert_eq!(None, w.first());
119 #[stable(feature = "rust1", since = "1.0.0")]
121 pub fn first(&self) -> Option<&T> {
122 if self.is_empty() { None } else { Some(&self[0]) }
125 /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
130 /// let x = &mut [0, 1, 2];
132 /// if let Some(first) = x.first_mut() {
135 /// assert_eq!(x, &[5, 1, 2]);
137 #[stable(feature = "rust1", since = "1.0.0")]
139 pub fn first_mut(&mut self) -> Option<&mut T> {
140 if self.is_empty() { None } else { Some(&mut self[0]) }
143 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
148 /// let x = &[0, 1, 2];
150 /// if let Some((first, elements)) = x.split_first() {
151 /// assert_eq!(first, &0);
152 /// assert_eq!(elements, &[1, 2]);
155 #[stable(feature = "slice_splits", since = "1.5.0")]
157 pub fn split_first(&self) -> Option<(&T, &[T])> {
158 if self.is_empty() { None } else { Some((&self[0], &self[1..])) }
161 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
166 /// let x = &mut [0, 1, 2];
168 /// if let Some((first, elements)) = x.split_first_mut() {
173 /// assert_eq!(x, &[3, 4, 5]);
175 #[stable(feature = "slice_splits", since = "1.5.0")]
177 pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
178 if self.is_empty() { None } else {
179 let split = self.split_at_mut(1);
180 Some((&mut split.0[0], split.1))
184 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
189 /// let x = &[0, 1, 2];
191 /// if let Some((last, elements)) = x.split_last() {
192 /// assert_eq!(last, &2);
193 /// assert_eq!(elements, &[0, 1]);
196 #[stable(feature = "slice_splits", since = "1.5.0")]
198 pub fn split_last(&self) -> Option<(&T, &[T])> {
199 let len = self.len();
200 if len == 0 { None } else { Some((&self[len - 1], &self[..(len - 1)])) }
203 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
208 /// let x = &mut [0, 1, 2];
210 /// if let Some((last, elements)) = x.split_last_mut() {
215 /// assert_eq!(x, &[4, 5, 3]);
217 #[stable(feature = "slice_splits", since = "1.5.0")]
219 pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
220 let len = self.len();
221 if len == 0 { None } else {
222 let split = self.split_at_mut(len - 1);
223 Some((&mut split.1[0], split.0))
228 /// Returns the last element of the slice, or `None` if it is empty.
233 /// let v = [10, 40, 30];
234 /// assert_eq!(Some(&30), v.last());
236 /// let w: &[i32] = &[];
237 /// assert_eq!(None, w.last());
239 #[stable(feature = "rust1", since = "1.0.0")]
241 pub fn last(&self) -> Option<&T> {
242 if self.is_empty() { None } else { Some(&self[self.len() - 1]) }
245 /// Returns a mutable pointer to the last item in the slice.
250 /// let x = &mut [0, 1, 2];
252 /// if let Some(last) = x.last_mut() {
255 /// assert_eq!(x, &[0, 1, 10]);
257 #[stable(feature = "rust1", since = "1.0.0")]
259 pub fn last_mut(&mut self) -> Option<&mut T> {
260 let len = self.len();
261 if len == 0 { return None; }
262 Some(&mut self[len - 1])
265 /// Returns a reference to an element or subslice depending on the type of
268 /// - If given a position, returns a reference to the element at that
269 /// position or `None` if out of bounds.
270 /// - If given a range, returns the subslice corresponding to that range,
271 /// or `None` if out of bounds.
276 /// let v = [10, 40, 30];
277 /// assert_eq!(Some(&40), v.get(1));
278 /// assert_eq!(Some(&[10, 40][..]), v.get(0..2));
279 /// assert_eq!(None, v.get(3));
280 /// assert_eq!(None, v.get(0..4));
282 #[stable(feature = "rust1", since = "1.0.0")]
284 pub fn get<I>(&self, index: I) -> Option<&I::Output>
285 where I: SliceIndex<Self>
290 /// Returns a mutable reference to an element or subslice depending on the
291 /// type of index (see [`get`]) or `None` if the index is out of bounds.
293 /// [`get`]: #method.get
298 /// let x = &mut [0, 1, 2];
300 /// if let Some(elem) = x.get_mut(1) {
303 /// assert_eq!(x, &[0, 42, 2]);
305 #[stable(feature = "rust1", since = "1.0.0")]
307 pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output>
308 where I: SliceIndex<Self>
313 /// Returns a reference to an element or subslice, without doing bounds
316 /// This is generally not recommended, use with caution! For a safe
317 /// alternative see [`get`].
319 /// [`get`]: #method.get
324 /// let x = &[1, 2, 4];
327 /// assert_eq!(x.get_unchecked(1), &2);
330 #[stable(feature = "rust1", since = "1.0.0")]
332 pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output
333 where I: SliceIndex<Self>
335 index.get_unchecked(self)
338 /// Returns a mutable reference to an element or subslice, without doing
341 /// This is generally not recommended, use with caution! For a safe
342 /// alternative see [`get_mut`].
344 /// [`get_mut`]: #method.get_mut
349 /// let x = &mut [1, 2, 4];
352 /// let elem = x.get_unchecked_mut(1);
355 /// assert_eq!(x, &[1, 13, 4]);
357 #[stable(feature = "rust1", since = "1.0.0")]
359 pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
360 where I: SliceIndex<Self>
362 index.get_unchecked_mut(self)
365 /// Returns a raw pointer to the slice's buffer.
367 /// The caller must ensure that the slice outlives the pointer this
368 /// function returns, or else it will end up pointing to garbage.
370 /// Modifying the container referenced by this slice may cause its buffer
371 /// to be reallocated, which would also make any pointers to it invalid.
376 /// let x = &[1, 2, 4];
377 /// let x_ptr = x.as_ptr();
380 /// for i in 0..x.len() {
381 /// assert_eq!(x.get_unchecked(i), &*x_ptr.add(i));
385 #[stable(feature = "rust1", since = "1.0.0")]
387 #[rustc_const_unstable(feature = "const_slice_as_ptr")]
388 pub const fn as_ptr(&self) -> *const T {
389 self as *const [T] as *const T
392 /// Returns an unsafe mutable pointer to the slice's buffer.
394 /// The caller must ensure that the slice outlives the pointer this
395 /// function returns, or else it will end up pointing to garbage.
397 /// Modifying the container referenced by this slice may cause its buffer
398 /// to be reallocated, which would also make any pointers to it invalid.
403 /// let x = &mut [1, 2, 4];
404 /// let x_ptr = x.as_mut_ptr();
407 /// for i in 0..x.len() {
408 /// *x_ptr.add(i) += 2;
411 /// assert_eq!(x, &[3, 4, 6]);
413 #[stable(feature = "rust1", since = "1.0.0")]
415 pub fn as_mut_ptr(&mut self) -> *mut T {
416 self as *mut [T] as *mut T
419 /// Swaps two elements in the slice.
423 /// * a - The index of the first element
424 /// * b - The index of the second element
428 /// Panics if `a` or `b` are out of bounds.
433 /// let mut v = ["a", "b", "c", "d"];
435 /// assert!(v == ["a", "d", "c", "b"]);
437 #[stable(feature = "rust1", since = "1.0.0")]
439 pub fn swap(&mut self, a: usize, b: usize) {
441 // Can't take two mutable loans from one vector, so instead just cast
442 // them to their raw pointers to do the swap
443 let pa: *mut T = &mut self[a];
444 let pb: *mut T = &mut self[b];
449 /// Reverses the order of elements in the slice, in place.
454 /// let mut v = [1, 2, 3];
456 /// assert!(v == [3, 2, 1]);
458 #[stable(feature = "rust1", since = "1.0.0")]
460 pub fn reverse(&mut self) {
461 let mut i: usize = 0;
464 // For very small types, all the individual reads in the normal
465 // path perform poorly. We can do better, given efficient unaligned
466 // load/store, by loading a larger chunk and reversing a register.
468 // Ideally LLVM would do this for us, as it knows better than we do
469 // whether unaligned reads are efficient (since that changes between
470 // different ARM versions, for example) and what the best chunk size
471 // would be. Unfortunately, as of LLVM 4.0 (2017-05) it only unrolls
472 // the loop, so we need to do this ourselves. (Hypothesis: reverse
473 // is troublesome because the sides can be aligned differently --
474 // will be, when the length is odd -- so there's no way of emitting
475 // pre- and postludes to use fully-aligned SIMD in the middle.)
478 cfg!(any(target_arch = "x86", target_arch = "x86_64"));
480 if fast_unaligned && mem::size_of::<T>() == 1 {
481 // Use the llvm.bswap intrinsic to reverse u8s in a usize
482 let chunk = mem::size_of::<usize>();
483 while i + chunk - 1 < ln / 2 {
485 let pa: *mut T = self.get_unchecked_mut(i);
486 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
487 let va = ptr::read_unaligned(pa as *mut usize);
488 let vb = ptr::read_unaligned(pb as *mut usize);
489 ptr::write_unaligned(pa as *mut usize, vb.swap_bytes());
490 ptr::write_unaligned(pb as *mut usize, va.swap_bytes());
496 if fast_unaligned && mem::size_of::<T>() == 2 {
497 // Use rotate-by-16 to reverse u16s in a u32
498 let chunk = mem::size_of::<u32>() / 2;
499 while i + chunk - 1 < ln / 2 {
501 let pa: *mut T = self.get_unchecked_mut(i);
502 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
503 let va = ptr::read_unaligned(pa as *mut u32);
504 let vb = ptr::read_unaligned(pb as *mut u32);
505 ptr::write_unaligned(pa as *mut u32, vb.rotate_left(16));
506 ptr::write_unaligned(pb as *mut u32, va.rotate_left(16));
513 // Unsafe swap to avoid the bounds check in safe swap.
515 let pa: *mut T = self.get_unchecked_mut(i);
516 let pb: *mut T = self.get_unchecked_mut(ln - i - 1);
523 /// Returns an iterator over the slice.
528 /// let x = &[1, 2, 4];
529 /// let mut iterator = x.iter();
531 /// assert_eq!(iterator.next(), Some(&1));
532 /// assert_eq!(iterator.next(), Some(&2));
533 /// assert_eq!(iterator.next(), Some(&4));
534 /// assert_eq!(iterator.next(), None);
536 #[stable(feature = "rust1", since = "1.0.0")]
538 pub fn iter(&self) -> Iter<T> {
540 let ptr = self.as_ptr();
541 assume(!ptr.is_null());
543 let end = if mem::size_of::<T>() == 0 {
544 (ptr as *const u8).wrapping_add(self.len()) as *const T
552 _marker: marker::PhantomData
557 /// Returns an iterator that allows modifying each value.
562 /// let x = &mut [1, 2, 4];
563 /// for elem in x.iter_mut() {
566 /// assert_eq!(x, &[3, 4, 6]);
568 #[stable(feature = "rust1", since = "1.0.0")]
570 pub fn iter_mut(&mut self) -> IterMut<T> {
572 let ptr = self.as_mut_ptr();
573 assume(!ptr.is_null());
575 let end = if mem::size_of::<T>() == 0 {
576 (ptr as *mut u8).wrapping_add(self.len()) as *mut T
584 _marker: marker::PhantomData
589 /// Returns an iterator over all contiguous windows of length
590 /// `size`. The windows overlap. If the slice is shorter than
591 /// `size`, the iterator returns no values.
595 /// Panics if `size` is 0.
600 /// let slice = ['r', 'u', 's', 't'];
601 /// let mut iter = slice.windows(2);
602 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
603 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
604 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
605 /// assert!(iter.next().is_none());
608 /// If the slice is shorter than `size`:
611 /// let slice = ['f', 'o', 'o'];
612 /// let mut iter = slice.windows(4);
613 /// assert!(iter.next().is_none());
615 #[stable(feature = "rust1", since = "1.0.0")]
617 pub fn windows(&self, size: usize) -> Windows<T> {
619 Windows { v: self, size }
622 /// Returns an iterator over `chunk_size` elements of the slice at a
623 /// time. The chunks are slices and do not overlap. If `chunk_size` does
624 /// not divide the length of the slice, then the last chunk will
625 /// not have length `chunk_size`.
627 /// See [`exact_chunks`] for a variant of this iterator that returns chunks
628 /// of always exactly `chunk_size` elements.
632 /// Panics if `chunk_size` is 0.
637 /// let slice = ['l', 'o', 'r', 'e', 'm'];
638 /// let mut iter = slice.chunks(2);
639 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
640 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
641 /// assert_eq!(iter.next().unwrap(), &['m']);
642 /// assert!(iter.next().is_none());
645 /// [`exact_chunks`]: #method.exact_chunks
646 #[stable(feature = "rust1", since = "1.0.0")]
648 pub fn chunks(&self, chunk_size: usize) -> Chunks<T> {
649 assert!(chunk_size != 0);
650 Chunks { v: self, chunk_size }
653 /// Returns an iterator over `chunk_size` elements of the slice at a time.
654 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
655 /// not divide the length of the slice, then the last chunk will not
656 /// have length `chunk_size`.
658 /// See [`exact_chunks_mut`] for a variant of this iterator that returns chunks
659 /// of always exactly `chunk_size` elements.
663 /// Panics if `chunk_size` is 0.
668 /// let v = &mut [0, 0, 0, 0, 0];
669 /// let mut count = 1;
671 /// for chunk in v.chunks_mut(2) {
672 /// for elem in chunk.iter_mut() {
677 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
680 /// [`exact_chunks_mut`]: #method.exact_chunks_mut
681 #[stable(feature = "rust1", since = "1.0.0")]
683 pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T> {
684 assert!(chunk_size != 0);
685 ChunksMut { v: self, chunk_size }
688 /// Returns an iterator over `chunk_size` elements of the slice at a
689 /// time. The chunks are slices and do not overlap. If `chunk_size` does
690 /// not divide the length of the slice, then the last up to `chunk_size-1`
691 /// elements will be omitted and can be retrieved from the `remainder`
692 /// function of the iterator.
694 /// Due to each chunk having exactly `chunk_size` elements, the compiler
695 /// can often optimize the resulting code better than in the case of
700 /// Panics if `chunk_size` is 0.
705 /// #![feature(exact_chunks)]
707 /// let slice = ['l', 'o', 'r', 'e', 'm'];
708 /// let mut iter = slice.exact_chunks(2);
709 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
710 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
711 /// assert!(iter.next().is_none());
714 /// [`chunks`]: #method.chunks
715 #[unstable(feature = "exact_chunks", issue = "47115")]
717 pub fn exact_chunks(&self, chunk_size: usize) -> ExactChunks<T> {
718 assert!(chunk_size != 0);
719 let rem = self.len() % chunk_size;
720 let len = self.len() - rem;
721 let (fst, snd) = self.split_at(len);
722 ExactChunks { v: fst, rem: snd, chunk_size }
725 /// Returns an iterator over `chunk_size` elements of the slice at a time.
726 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
727 /// not divide the length of the slice, then the last up to `chunk_size-1`
728 /// elements will be omitted and can be retrieved from the `into_remainder`
729 /// function of the iterator.
731 /// Due to each chunk having exactly `chunk_size` elements, the compiler
732 /// can often optimize the resulting code better than in the case of
737 /// Panics if `chunk_size` is 0.
742 /// #![feature(exact_chunks)]
744 /// let v = &mut [0, 0, 0, 0, 0];
745 /// let mut count = 1;
747 /// for chunk in v.exact_chunks_mut(2) {
748 /// for elem in chunk.iter_mut() {
753 /// assert_eq!(v, &[1, 1, 2, 2, 0]);
756 /// [`chunks_mut`]: #method.chunks_mut
757 #[unstable(feature = "exact_chunks", issue = "47115")]
759 pub fn exact_chunks_mut(&mut self, chunk_size: usize) -> ExactChunksMut<T> {
760 assert!(chunk_size != 0);
761 let rem = self.len() % chunk_size;
762 let len = self.len() - rem;
763 let (fst, snd) = self.split_at_mut(len);
764 ExactChunksMut { v: fst, rem: snd, chunk_size }
767 /// Divides one slice into two at an index.
769 /// The first will contain all indices from `[0, mid)` (excluding
770 /// the index `mid` itself) and the second will contain all
771 /// indices from `[mid, len)` (excluding the index `len` itself).
775 /// Panics if `mid > len`.
780 /// let v = [1, 2, 3, 4, 5, 6];
783 /// let (left, right) = v.split_at(0);
784 /// assert!(left == []);
785 /// assert!(right == [1, 2, 3, 4, 5, 6]);
789 /// let (left, right) = v.split_at(2);
790 /// assert!(left == [1, 2]);
791 /// assert!(right == [3, 4, 5, 6]);
795 /// let (left, right) = v.split_at(6);
796 /// assert!(left == [1, 2, 3, 4, 5, 6]);
797 /// assert!(right == []);
800 #[stable(feature = "rust1", since = "1.0.0")]
802 pub fn split_at(&self, mid: usize) -> (&[T], &[T]) {
803 (&self[..mid], &self[mid..])
806 /// Divides one mutable slice into two at an index.
808 /// The first will contain all indices from `[0, mid)` (excluding
809 /// the index `mid` itself) and the second will contain all
810 /// indices from `[mid, len)` (excluding the index `len` itself).
814 /// Panics if `mid > len`.
819 /// let mut v = [1, 0, 3, 0, 5, 6];
820 /// // scoped to restrict the lifetime of the borrows
822 /// let (left, right) = v.split_at_mut(2);
823 /// assert!(left == [1, 0]);
824 /// assert!(right == [3, 0, 5, 6]);
828 /// assert!(v == [1, 2, 3, 4, 5, 6]);
830 #[stable(feature = "rust1", since = "1.0.0")]
832 pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
833 let len = self.len();
834 let ptr = self.as_mut_ptr();
839 (from_raw_parts_mut(ptr, mid),
840 from_raw_parts_mut(ptr.add(mid), len - mid))
844 /// Returns an iterator over subslices separated by elements that match
845 /// `pred`. The matched element is not contained in the subslices.
850 /// let slice = [10, 40, 33, 20];
851 /// let mut iter = slice.split(|num| num % 3 == 0);
853 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
854 /// assert_eq!(iter.next().unwrap(), &[20]);
855 /// assert!(iter.next().is_none());
858 /// If the first element is matched, an empty slice will be the first item
859 /// returned by the iterator. Similarly, if the last element in the slice
860 /// is matched, an empty slice will be the last item returned by the
864 /// let slice = [10, 40, 33];
865 /// let mut iter = slice.split(|num| num % 3 == 0);
867 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
868 /// assert_eq!(iter.next().unwrap(), &[]);
869 /// assert!(iter.next().is_none());
872 /// If two matched elements are directly adjacent, an empty slice will be
873 /// present between them:
876 /// let slice = [10, 6, 33, 20];
877 /// let mut iter = slice.split(|num| num % 3 == 0);
879 /// assert_eq!(iter.next().unwrap(), &[10]);
880 /// assert_eq!(iter.next().unwrap(), &[]);
881 /// assert_eq!(iter.next().unwrap(), &[20]);
882 /// assert!(iter.next().is_none());
884 #[stable(feature = "rust1", since = "1.0.0")]
886 pub fn split<F>(&self, pred: F) -> Split<T, F>
887 where F: FnMut(&T) -> bool
896 /// Returns an iterator over mutable subslices separated by elements that
897 /// match `pred`. The matched element is not contained in the subslices.
902 /// let mut v = [10, 40, 30, 20, 60, 50];
904 /// for group in v.split_mut(|num| *num % 3 == 0) {
907 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
909 #[stable(feature = "rust1", since = "1.0.0")]
911 pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<T, F>
912 where F: FnMut(&T) -> bool
914 SplitMut { v: self, pred, finished: false }
917 /// Returns an iterator over subslices separated by elements that match
918 /// `pred`, starting at the end of the slice and working backwards.
919 /// The matched element is not contained in the subslices.
924 /// let slice = [11, 22, 33, 0, 44, 55];
925 /// let mut iter = slice.rsplit(|num| *num == 0);
927 /// assert_eq!(iter.next().unwrap(), &[44, 55]);
928 /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
929 /// assert_eq!(iter.next(), None);
932 /// As with `split()`, if the first or last element is matched, an empty
933 /// slice will be the first (or last) item returned by the iterator.
936 /// let v = &[0, 1, 1, 2, 3, 5, 8];
937 /// let mut it = v.rsplit(|n| *n % 2 == 0);
938 /// assert_eq!(it.next().unwrap(), &[]);
939 /// assert_eq!(it.next().unwrap(), &[3, 5]);
940 /// assert_eq!(it.next().unwrap(), &[1, 1]);
941 /// assert_eq!(it.next().unwrap(), &[]);
942 /// assert_eq!(it.next(), None);
944 #[stable(feature = "slice_rsplit", since = "1.27.0")]
946 pub fn rsplit<F>(&self, pred: F) -> RSplit<T, F>
947 where F: FnMut(&T) -> bool
949 RSplit { inner: self.split(pred) }
952 /// Returns an iterator over mutable subslices separated by elements that
953 /// match `pred`, starting at the end of the slice and working
954 /// backwards. The matched element is not contained in the subslices.
959 /// let mut v = [100, 400, 300, 200, 600, 500];
961 /// let mut count = 0;
962 /// for group in v.rsplit_mut(|num| *num % 3 == 0) {
964 /// group[0] = count;
966 /// assert_eq!(v, [3, 400, 300, 2, 600, 1]);
969 #[stable(feature = "slice_rsplit", since = "1.27.0")]
971 pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<T, F>
972 where F: FnMut(&T) -> bool
974 RSplitMut { inner: self.split_mut(pred) }
977 /// Returns an iterator over subslices separated by elements that match
978 /// `pred`, limited to returning at most `n` items. The matched element is
979 /// not contained in the subslices.
981 /// The last element returned, if any, will contain the remainder of the
986 /// Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`,
990 /// let v = [10, 40, 30, 20, 60, 50];
992 /// for group in v.splitn(2, |num| *num % 3 == 0) {
993 /// println!("{:?}", group);
996 #[stable(feature = "rust1", since = "1.0.0")]
998 pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F>
999 where F: FnMut(&T) -> bool
1002 inner: GenericSplitN {
1003 iter: self.split(pred),
1009 /// Returns an iterator over subslices separated by elements that match
1010 /// `pred`, limited to returning at most `n` items. The matched element is
1011 /// not contained in the subslices.
1013 /// The last element returned, if any, will contain the remainder of the
1019 /// let mut v = [10, 40, 30, 20, 60, 50];
1021 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
1024 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
1026 #[stable(feature = "rust1", since = "1.0.0")]
1028 pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<T, F>
1029 where F: FnMut(&T) -> bool
1032 inner: GenericSplitN {
1033 iter: self.split_mut(pred),
1039 /// Returns an iterator over subslices separated by elements that match
1040 /// `pred` limited to returning at most `n` items. This starts at the end of
1041 /// the slice and works backwards. The matched element is not contained in
1044 /// The last element returned, if any, will contain the remainder of the
1049 /// Print the slice split once, starting from the end, by numbers divisible
1050 /// by 3 (i.e. `[50]`, `[10, 40, 30, 20]`):
1053 /// let v = [10, 40, 30, 20, 60, 50];
1055 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
1056 /// println!("{:?}", group);
1059 #[stable(feature = "rust1", since = "1.0.0")]
1061 pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F>
1062 where F: FnMut(&T) -> bool
1065 inner: GenericSplitN {
1066 iter: self.rsplit(pred),
1072 /// Returns an iterator over subslices separated by elements that match
1073 /// `pred` limited to returning at most `n` items. This starts at the end of
1074 /// the slice and works backwards. The matched element is not contained in
1077 /// The last element returned, if any, will contain the remainder of the
1083 /// let mut s = [10, 40, 30, 20, 60, 50];
1085 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
1088 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
1090 #[stable(feature = "rust1", since = "1.0.0")]
1092 pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<T, F>
1093 where F: FnMut(&T) -> bool
1096 inner: GenericSplitN {
1097 iter: self.rsplit_mut(pred),
1103 /// Returns `true` if the slice contains an element with the given value.
1108 /// let v = [10, 40, 30];
1109 /// assert!(v.contains(&30));
1110 /// assert!(!v.contains(&50));
1112 #[stable(feature = "rust1", since = "1.0.0")]
1113 pub fn contains(&self, x: &T) -> bool
1116 x.slice_contains(self)
1119 /// Returns `true` if `needle` is a prefix of the slice.
1124 /// let v = [10, 40, 30];
1125 /// assert!(v.starts_with(&[10]));
1126 /// assert!(v.starts_with(&[10, 40]));
1127 /// assert!(!v.starts_with(&[50]));
1128 /// assert!(!v.starts_with(&[10, 50]));
1131 /// Always returns `true` if `needle` is an empty slice:
1134 /// let v = &[10, 40, 30];
1135 /// assert!(v.starts_with(&[]));
1136 /// let v: &[u8] = &[];
1137 /// assert!(v.starts_with(&[]));
1139 #[stable(feature = "rust1", since = "1.0.0")]
1140 pub fn starts_with(&self, needle: &[T]) -> bool
1143 let n = needle.len();
1144 self.len() >= n && needle == &self[..n]
1147 /// Returns `true` if `needle` is a suffix of the slice.
1152 /// let v = [10, 40, 30];
1153 /// assert!(v.ends_with(&[30]));
1154 /// assert!(v.ends_with(&[40, 30]));
1155 /// assert!(!v.ends_with(&[50]));
1156 /// assert!(!v.ends_with(&[50, 30]));
1159 /// Always returns `true` if `needle` is an empty slice:
1162 /// let v = &[10, 40, 30];
1163 /// assert!(v.ends_with(&[]));
1164 /// let v: &[u8] = &[];
1165 /// assert!(v.ends_with(&[]));
1167 #[stable(feature = "rust1", since = "1.0.0")]
1168 pub fn ends_with(&self, needle: &[T]) -> bool
1171 let (m, n) = (self.len(), needle.len());
1172 m >= n && needle == &self[m-n..]
1175 /// Binary searches this sorted slice for a given element.
1177 /// If the value is found then `Ok` is returned, containing the
1178 /// index of the matching element; if the value is not found then
1179 /// `Err` is returned, containing the index where a matching
1180 /// element could be inserted while maintaining sorted order.
1184 /// Looks up a series of four elements. The first is found, with a
1185 /// uniquely determined position; the second and third are not
1186 /// found; the fourth could match any position in `[1, 4]`.
1189 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1191 /// assert_eq!(s.binary_search(&13), Ok(9));
1192 /// assert_eq!(s.binary_search(&4), Err(7));
1193 /// assert_eq!(s.binary_search(&100), Err(13));
1194 /// let r = s.binary_search(&1);
1195 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1197 #[stable(feature = "rust1", since = "1.0.0")]
1198 pub fn binary_search(&self, x: &T) -> Result<usize, usize>
1201 self.binary_search_by(|p| p.cmp(x))
1204 /// Binary searches this sorted slice with a comparator function.
1206 /// The comparator function should implement an order consistent
1207 /// with the sort order of the underlying slice, returning an
1208 /// order code that indicates whether its argument is `Less`,
1209 /// `Equal` or `Greater` the desired target.
1211 /// If a matching value is found then returns `Ok`, containing
1212 /// the index for the matched element; if no match is found then
1213 /// `Err` is returned, containing the index where a matching
1214 /// element could be inserted while maintaining sorted order.
1218 /// Looks up a series of four elements. The first is found, with a
1219 /// uniquely determined position; the second and third are not
1220 /// found; the fourth could match any position in `[1, 4]`.
1223 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1226 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
1228 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
1230 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
1232 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
1233 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1235 #[stable(feature = "rust1", since = "1.0.0")]
1237 pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
1238 where F: FnMut(&'a T) -> Ordering
1241 let mut size = s.len();
1245 let mut base = 0usize;
1247 let half = size / 2;
1248 let mid = base + half;
1249 // mid is always in [0, size), that means mid is >= 0 and < size.
1250 // mid >= 0: by definition
1251 // mid < size: mid = size / 2 + size / 4 + size / 8 ...
1252 let cmp = f(unsafe { s.get_unchecked(mid) });
1253 base = if cmp == Greater { base } else { mid };
1256 // base is always in [0, size) because base <= mid.
1257 let cmp = f(unsafe { s.get_unchecked(base) });
1258 if cmp == Equal { Ok(base) } else { Err(base + (cmp == Less) as usize) }
1262 /// Binary searches this sorted slice with a key extraction function.
1264 /// Assumes that the slice is sorted by the key, for instance with
1265 /// [`sort_by_key`] using the same key extraction function.
1267 /// If a matching value is found then returns `Ok`, containing the
1268 /// index for the matched element; if no match is found then `Err`
1269 /// is returned, containing the index where a matching element could
1270 /// be inserted while maintaining sorted order.
1272 /// [`sort_by_key`]: #method.sort_by_key
1276 /// Looks up a series of four elements in a slice of pairs sorted by
1277 /// their second elements. The first is found, with a uniquely
1278 /// determined position; the second and third are not found; the
1279 /// fourth could match any position in `[1, 4]`.
1282 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
1283 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
1284 /// (1, 21), (2, 34), (4, 55)];
1286 /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9));
1287 /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7));
1288 /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
1289 /// let r = s.binary_search_by_key(&1, |&(a,b)| b);
1290 /// assert!(match r { Ok(1..=4) => true, _ => false, });
1292 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
1294 pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
1295 where F: FnMut(&'a T) -> B,
1298 self.binary_search_by(|k| f(k).cmp(b))
1301 /// Sorts the slice, but may not preserve the order of equal elements.
1303 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1304 /// and `O(n log n)` worst-case.
1306 /// # Current implementation
1308 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1309 /// which combines the fast average case of randomized quicksort with the fast worst case of
1310 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1311 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1312 /// deterministic behavior.
1314 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1315 /// slice consists of several concatenated sorted sequences.
1320 /// let mut v = [-5, 4, 1, -3, 2];
1322 /// v.sort_unstable();
1323 /// assert!(v == [-5, -3, 1, 2, 4]);
1326 /// [pdqsort]: https://github.com/orlp/pdqsort
1327 #[stable(feature = "sort_unstable", since = "1.20.0")]
1329 pub fn sort_unstable(&mut self)
1332 sort::quicksort(self, |a, b| a.lt(b));
1335 /// Sorts the slice with a comparator function, but may not preserve the order of equal
1338 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1339 /// and `O(n log n)` worst-case.
1341 /// # Current implementation
1343 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1344 /// which combines the fast average case of randomized quicksort with the fast worst case of
1345 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1346 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1347 /// deterministic behavior.
1349 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1350 /// slice consists of several concatenated sorted sequences.
1355 /// let mut v = [5, 4, 1, 3, 2];
1356 /// v.sort_unstable_by(|a, b| a.cmp(b));
1357 /// assert!(v == [1, 2, 3, 4, 5]);
1359 /// // reverse sorting
1360 /// v.sort_unstable_by(|a, b| b.cmp(a));
1361 /// assert!(v == [5, 4, 3, 2, 1]);
1364 /// [pdqsort]: https://github.com/orlp/pdqsort
1365 #[stable(feature = "sort_unstable", since = "1.20.0")]
1367 pub fn sort_unstable_by<F>(&mut self, mut compare: F)
1368 where F: FnMut(&T, &T) -> Ordering
1370 sort::quicksort(self, |a, b| compare(a, b) == Ordering::Less);
1373 /// Sorts the slice with a key extraction function, but may not preserve the order of equal
1376 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1377 /// and `O(m n log(m n))` worst-case, where the key function is `O(m)`.
1379 /// # Current implementation
1381 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1382 /// which combines the fast average case of randomized quicksort with the fast worst case of
1383 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1384 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1385 /// deterministic behavior.
1390 /// let mut v = [-5i32, 4, 1, -3, 2];
1392 /// v.sort_unstable_by_key(|k| k.abs());
1393 /// assert!(v == [1, 2, -3, 4, -5]);
1396 /// [pdqsort]: https://github.com/orlp/pdqsort
1397 #[stable(feature = "sort_unstable", since = "1.20.0")]
1399 pub fn sort_unstable_by_key<K, F>(&mut self, mut f: F)
1400 where F: FnMut(&T) -> K, K: Ord
1402 sort::quicksort(self, |a, b| f(a).lt(&f(b)));
1405 /// Rotates the slice in-place such that the first `mid` elements of the
1406 /// slice move to the end while the last `self.len() - mid` elements move to
1407 /// the front. After calling `rotate_left`, the element previously at index
1408 /// `mid` will become the first element in the slice.
1412 /// This function will panic if `mid` is greater than the length of the
1413 /// slice. Note that `mid == self.len()` does _not_ panic and is a no-op
1418 /// Takes linear (in `self.len()`) time.
1423 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1424 /// a.rotate_left(2);
1425 /// assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
1428 /// Rotating a subslice:
1431 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1432 /// a[1..5].rotate_left(1);
1433 /// assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']);
1435 #[stable(feature = "slice_rotate", since = "1.26.0")]
1436 pub fn rotate_left(&mut self, mid: usize) {
1437 assert!(mid <= self.len());
1438 let k = self.len() - mid;
1441 let p = self.as_mut_ptr();
1442 rotate::ptr_rotate(mid, p.add(mid), k);
1446 /// Rotates the slice in-place such that the first `self.len() - k`
1447 /// elements of the slice move to the end while the last `k` elements move
1448 /// to the front. After calling `rotate_right`, the element previously at
1449 /// index `self.len() - k` will become the first element in the slice.
1453 /// This function will panic if `k` is greater than the length of the
1454 /// slice. Note that `k == self.len()` does _not_ panic and is a no-op
1459 /// Takes linear (in `self.len()`) time.
1464 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1465 /// a.rotate_right(2);
1466 /// assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);
1469 /// Rotate a subslice:
1472 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1473 /// a[1..5].rotate_right(1);
1474 /// assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']);
1476 #[stable(feature = "slice_rotate", since = "1.26.0")]
1477 pub fn rotate_right(&mut self, k: usize) {
1478 assert!(k <= self.len());
1479 let mid = self.len() - k;
1482 let p = self.as_mut_ptr();
1483 rotate::ptr_rotate(mid, p.add(mid), k);
1487 /// Copies the elements from `src` into `self`.
1489 /// The length of `src` must be the same as `self`.
1491 /// If `src` implements `Copy`, it can be more performant to use
1492 /// [`copy_from_slice`].
1496 /// This function will panic if the two slices have different lengths.
1500 /// Cloning two elements from a slice into another:
1503 /// let src = [1, 2, 3, 4];
1504 /// let mut dst = [0, 0];
1506 /// // Because the slices have to be the same length,
1507 /// // we slice the source slice from four elements
1508 /// // to two. It will panic if we don't do this.
1509 /// dst.clone_from_slice(&src[2..]);
1511 /// assert_eq!(src, [1, 2, 3, 4]);
1512 /// assert_eq!(dst, [3, 4]);
1515 /// Rust enforces that there can only be one mutable reference with no
1516 /// immutable references to a particular piece of data in a particular
1517 /// scope. Because of this, attempting to use `clone_from_slice` on a
1518 /// single slice will result in a compile failure:
1521 /// let mut slice = [1, 2, 3, 4, 5];
1523 /// slice[..2].clone_from_slice(&slice[3..]); // compile fail!
1526 /// To work around this, we can use [`split_at_mut`] to create two distinct
1527 /// sub-slices from a slice:
1530 /// let mut slice = [1, 2, 3, 4, 5];
1533 /// let (left, right) = slice.split_at_mut(2);
1534 /// left.clone_from_slice(&right[1..]);
1537 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
1540 /// [`copy_from_slice`]: #method.copy_from_slice
1541 /// [`split_at_mut`]: #method.split_at_mut
1542 #[stable(feature = "clone_from_slice", since = "1.7.0")]
1543 pub fn clone_from_slice(&mut self, src: &[T]) where T: Clone {
1544 assert!(self.len() == src.len(),
1545 "destination and source slices have different lengths");
1546 // NOTE: We need to explicitly slice them to the same length
1547 // for bounds checking to be elided, and the optimizer will
1548 // generate memcpy for simple cases (for example T = u8).
1549 let len = self.len();
1550 let src = &src[..len];
1552 self[i].clone_from(&src[i]);
1557 /// Copies all elements from `src` into `self`, using a memcpy.
1559 /// The length of `src` must be the same as `self`.
1561 /// If `src` does not implement `Copy`, use [`clone_from_slice`].
1565 /// This function will panic if the two slices have different lengths.
1569 /// Copying two elements from a slice into another:
1572 /// let src = [1, 2, 3, 4];
1573 /// let mut dst = [0, 0];
1575 /// // Because the slices have to be the same length,
1576 /// // we slice the source slice from four elements
1577 /// // to two. It will panic if we don't do this.
1578 /// dst.copy_from_slice(&src[2..]);
1580 /// assert_eq!(src, [1, 2, 3, 4]);
1581 /// assert_eq!(dst, [3, 4]);
1584 /// Rust enforces that there can only be one mutable reference with no
1585 /// immutable references to a particular piece of data in a particular
1586 /// scope. Because of this, attempting to use `copy_from_slice` on a
1587 /// single slice will result in a compile failure:
1590 /// let mut slice = [1, 2, 3, 4, 5];
1592 /// slice[..2].copy_from_slice(&slice[3..]); // compile fail!
1595 /// To work around this, we can use [`split_at_mut`] to create two distinct
1596 /// sub-slices from a slice:
1599 /// let mut slice = [1, 2, 3, 4, 5];
1602 /// let (left, right) = slice.split_at_mut(2);
1603 /// left.copy_from_slice(&right[1..]);
1606 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
1609 /// [`clone_from_slice`]: #method.clone_from_slice
1610 /// [`split_at_mut`]: #method.split_at_mut
1611 #[stable(feature = "copy_from_slice", since = "1.9.0")]
1612 pub fn copy_from_slice(&mut self, src: &[T]) where T: Copy {
1613 assert_eq!(self.len(), src.len(),
1614 "destination and source slices have different lengths");
1616 ptr::copy_nonoverlapping(
1617 src.as_ptr(), self.as_mut_ptr(), self.len());
1621 /// Swaps all elements in `self` with those in `other`.
1623 /// The length of `other` must be the same as `self`.
1627 /// This function will panic if the two slices have different lengths.
1631 /// Swapping two elements across slices:
1634 /// let mut slice1 = [0, 0];
1635 /// let mut slice2 = [1, 2, 3, 4];
1637 /// slice1.swap_with_slice(&mut slice2[2..]);
1639 /// assert_eq!(slice1, [3, 4]);
1640 /// assert_eq!(slice2, [1, 2, 0, 0]);
1643 /// Rust enforces that there can only be one mutable reference to a
1644 /// particular piece of data in a particular scope. Because of this,
1645 /// attempting to use `swap_with_slice` on a single slice will result in
1646 /// a compile failure:
1649 /// let mut slice = [1, 2, 3, 4, 5];
1650 /// slice[..2].swap_with_slice(&mut slice[3..]); // compile fail!
1653 /// To work around this, we can use [`split_at_mut`] to create two distinct
1654 /// mutable sub-slices from a slice:
1657 /// let mut slice = [1, 2, 3, 4, 5];
1660 /// let (left, right) = slice.split_at_mut(2);
1661 /// left.swap_with_slice(&mut right[1..]);
1664 /// assert_eq!(slice, [4, 5, 3, 1, 2]);
1667 /// [`split_at_mut`]: #method.split_at_mut
1668 #[stable(feature = "swap_with_slice", since = "1.27.0")]
1669 pub fn swap_with_slice(&mut self, other: &mut [T]) {
1670 assert!(self.len() == other.len(),
1671 "destination and source slices have different lengths");
1673 ptr::swap_nonoverlapping(
1674 self.as_mut_ptr(), other.as_mut_ptr(), self.len());
1678 /// Function to calculate lengths of the middle and trailing slice for `align_to{,_mut}`.
1679 fn align_to_offsets<U>(&self) -> (usize, usize) {
1680 // What we gonna do about `rest` is figure out what multiple of `U`s we can put in a
1681 // lowest number of `T`s. And how many `T`s we need for each such "multiple".
1683 // Consider for example T=u8 U=u16. Then we can put 1 U in 2 Ts. Simple. Now, consider
1684 // for example a case where size_of::<T> = 16, size_of::<U> = 24. We can put 2 Us in
1685 // place of every 3 Ts in the `rest` slice. A bit more complicated.
1687 // Formula to calculate this is:
1689 // Us = lcm(size_of::<T>, size_of::<U>) / size_of::<U>
1690 // Ts = lcm(size_of::<T>, size_of::<U>) / size_of::<T>
1692 // Expanded and simplified:
1694 // Us = size_of::<T> / gcd(size_of::<T>, size_of::<U>)
1695 // Ts = size_of::<U> / gcd(size_of::<T>, size_of::<U>)
1697 // Luckily since all this is constant-evaluated... performance here matters not!
1699 fn gcd(a: usize, b: usize) -> usize {
1700 // iterative stein’s algorithm
1701 // We should still make this `const fn` (and revert to recursive algorithm if we do)
1702 // because relying on llvm to consteval all this is… well, it makes me
1703 let (ctz_a, mut ctz_b) = unsafe {
1704 if a == 0 { return b; }
1705 if b == 0 { return a; }
1706 (::intrinsics::cttz_nonzero(a), ::intrinsics::cttz_nonzero(b))
1708 let k = ctz_a.min(ctz_b);
1709 let mut a = a >> ctz_a;
1712 // remove all factors of 2 from b
1715 ::mem::swap(&mut a, &mut b);
1722 ctz_b = ::intrinsics::cttz_nonzero(b);
1727 let gcd: usize = gcd(::mem::size_of::<T>(), ::mem::size_of::<U>());
1728 let ts: usize = ::mem::size_of::<U>() / gcd;
1729 let us: usize = ::mem::size_of::<T>() / gcd;
1731 // Armed with this knowledge, we can find how many `U`s we can fit!
1732 let us_len = self.len() / ts * us;
1733 // And how many `T`s will be in the trailing slice!
1734 let ts_len = self.len() % ts;
1738 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
1741 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
1742 /// slice of a new type, and the suffix slice. The middle slice will have the greatest length
1743 /// possible for a given type and input slice.
1745 /// This method has no purpose when either input element `T` or output element `U` are
1746 /// zero-sized and will return the original slice without splitting anything.
1750 /// This method is essentially a `transmute` with respect to the elements in the returned
1751 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
1758 /// # #![feature(slice_align_to)]
1760 /// let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
1761 /// let (prefix, shorts, suffix) = bytes.align_to::<u16>();
1762 /// // less_efficient_algorithm_for_bytes(prefix);
1763 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
1764 /// // less_efficient_algorithm_for_bytes(suffix);
1767 #[unstable(feature = "slice_align_to", issue = "44488")]
1768 pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T]) {
1769 // Note that most of this function will be constant-evaluated,
1770 if ::mem::size_of::<U>() == 0 || ::mem::size_of::<T>() == 0 {
1771 // handle ZSTs specially, which is – don't handle them at all.
1772 return (self, &[], &[]);
1775 // First, find at what point do we split between the first and 2nd slice. Easy with
1776 // ptr.align_offset.
1777 let ptr = self.as_ptr();
1778 let offset = ::ptr::align_offset(ptr, ::mem::align_of::<U>());
1779 if offset > self.len() {
1782 let (left, rest) = self.split_at(offset);
1783 // now `rest` is definitely aligned, so `from_raw_parts_mut` below is okay
1784 let (us_len, ts_len) = rest.align_to_offsets::<U>();
1786 from_raw_parts(rest.as_ptr() as *const U, us_len),
1787 from_raw_parts(rest.as_ptr().add(rest.len() - ts_len), ts_len))
1791 /// Transmute the slice to a slice of another type, ensuring alignment of the types is
1794 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
1795 /// slice of a new type, and the suffix slice. The middle slice will have the greatest length
1796 /// possible for a given type and input slice.
1798 /// This method has no purpose when either input element `T` or output element `U` are
1799 /// zero-sized and will return the original slice without splitting anything.
1803 /// This method is essentially a `transmute` with respect to the elements in the returned
1804 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
1811 /// # #![feature(slice_align_to)]
1813 /// let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
1814 /// let (prefix, shorts, suffix) = bytes.align_to_mut::<u16>();
1815 /// // less_efficient_algorithm_for_bytes(prefix);
1816 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
1817 /// // less_efficient_algorithm_for_bytes(suffix);
1820 #[unstable(feature = "slice_align_to", issue = "44488")]
1821 pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T]) {
1822 // Note that most of this function will be constant-evaluated,
1823 if ::mem::size_of::<U>() == 0 || ::mem::size_of::<T>() == 0 {
1824 // handle ZSTs specially, which is – don't handle them at all.
1825 return (self, &mut [], &mut []);
1828 // First, find at what point do we split between the first and 2nd slice. Easy with
1829 // ptr.align_offset.
1830 let ptr = self.as_ptr();
1831 let offset = ::ptr::align_offset(ptr, ::mem::align_of::<U>());
1832 if offset > self.len() {
1833 (self, &mut [], &mut [])
1835 let (left, rest) = self.split_at_mut(offset);
1836 // now `rest` is definitely aligned, so `from_raw_parts_mut` below is okay
1837 let (us_len, ts_len) = rest.align_to_offsets::<U>();
1838 let mut_ptr = rest.as_mut_ptr();
1840 from_raw_parts_mut(mut_ptr as *mut U, us_len),
1841 from_raw_parts_mut(mut_ptr.add(rest.len() - ts_len), ts_len))
1846 #[lang = "slice_u8"]
1849 /// Checks if all bytes in this slice are within the ASCII range.
1850 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
1852 pub fn is_ascii(&self) -> bool {
1853 self.iter().all(|b| b.is_ascii())
1856 /// Checks that two slices are an ASCII case-insensitive match.
1858 /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
1859 /// but without allocating and copying temporaries.
1860 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
1862 pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool {
1863 self.len() == other.len() &&
1864 self.iter().zip(other).all(|(a, b)| {
1865 a.eq_ignore_ascii_case(b)
1869 /// Converts this slice to its ASCII upper case equivalent in-place.
1871 /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
1872 /// but non-ASCII letters are unchanged.
1874 /// To return a new uppercased value without modifying the existing one, use
1875 /// [`to_ascii_uppercase`].
1877 /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
1878 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
1880 pub fn make_ascii_uppercase(&mut self) {
1882 byte.make_ascii_uppercase();
1886 /// Converts this slice to its ASCII lower case equivalent in-place.
1888 /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
1889 /// but non-ASCII letters are unchanged.
1891 /// To return a new lowercased value without modifying the existing one, use
1892 /// [`to_ascii_lowercase`].
1894 /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
1895 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
1897 pub fn make_ascii_lowercase(&mut self) {
1899 byte.make_ascii_lowercase();
1905 #[stable(feature = "rust1", since = "1.0.0")]
1906 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
1907 impl<T, I> ops::Index<I> for [T]
1908 where I: SliceIndex<[T]>
1910 type Output = I::Output;
1913 fn index(&self, index: I) -> &I::Output {
1918 #[stable(feature = "rust1", since = "1.0.0")]
1919 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
1920 impl<T, I> ops::IndexMut<I> for [T]
1921 where I: SliceIndex<[T]>
1924 fn index_mut(&mut self, index: I) -> &mut I::Output {
1925 index.index_mut(self)
1931 fn slice_index_len_fail(index: usize, len: usize) -> ! {
1932 panic!("index {} out of range for slice of length {}", index, len);
1937 fn slice_index_order_fail(index: usize, end: usize) -> ! {
1938 panic!("slice index starts at {} but ends at {}", index, end);
1943 fn slice_index_overflow_fail() -> ! {
1944 panic!("attempted to index slice up to maximum usize");
1947 mod private_slice_index {
1949 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1952 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1953 impl Sealed for usize {}
1954 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1955 impl Sealed for ops::Range<usize> {}
1956 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1957 impl Sealed for ops::RangeTo<usize> {}
1958 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1959 impl Sealed for ops::RangeFrom<usize> {}
1960 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1961 impl Sealed for ops::RangeFull {}
1962 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1963 impl Sealed for ops::RangeInclusive<usize> {}
1964 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1965 impl Sealed for ops::RangeToInclusive<usize> {}
1968 /// A helper trait used for indexing operations.
1969 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1970 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
1971 pub trait SliceIndex<T: ?Sized>: private_slice_index::Sealed {
1972 /// The output type returned by methods.
1973 #[stable(feature = "slice_get_slice", since = "1.28.0")]
1974 type Output: ?Sized;
1976 /// Returns a shared reference to the output at this location, if in
1978 #[unstable(feature = "slice_index_methods", issue = "0")]
1979 fn get(self, slice: &T) -> Option<&Self::Output>;
1981 /// Returns a mutable reference to the output at this location, if in
1983 #[unstable(feature = "slice_index_methods", issue = "0")]
1984 fn get_mut(self, slice: &mut T) -> Option<&mut Self::Output>;
1986 /// Returns a shared reference to the output at this location, without
1987 /// performing any bounds checking.
1988 #[unstable(feature = "slice_index_methods", issue = "0")]
1989 unsafe fn get_unchecked(self, slice: &T) -> &Self::Output;
1991 /// Returns a mutable reference to the output at this location, without
1992 /// performing any bounds checking.
1993 #[unstable(feature = "slice_index_methods", issue = "0")]
1994 unsafe fn get_unchecked_mut(self, slice: &mut T) -> &mut Self::Output;
1996 /// Returns a shared reference to the output at this location, panicking
1997 /// if out of bounds.
1998 #[unstable(feature = "slice_index_methods", issue = "0")]
1999 fn index(self, slice: &T) -> &Self::Output;
2001 /// Returns a mutable reference to the output at this location, panicking
2002 /// if out of bounds.
2003 #[unstable(feature = "slice_index_methods", issue = "0")]
2004 fn index_mut(self, slice: &mut T) -> &mut Self::Output;
2007 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2008 impl<T> SliceIndex<[T]> for usize {
2012 fn get(self, slice: &[T]) -> Option<&T> {
2013 if self < slice.len() {
2015 Some(self.get_unchecked(slice))
2023 fn get_mut(self, slice: &mut [T]) -> Option<&mut T> {
2024 if self < slice.len() {
2026 Some(self.get_unchecked_mut(slice))
2034 unsafe fn get_unchecked(self, slice: &[T]) -> &T {
2035 &*slice.as_ptr().add(self)
2039 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut T {
2040 &mut *slice.as_mut_ptr().add(self)
2044 fn index(self, slice: &[T]) -> &T {
2045 // NB: use intrinsic indexing
2050 fn index_mut(self, slice: &mut [T]) -> &mut T {
2051 // NB: use intrinsic indexing
2056 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2057 impl<T> SliceIndex<[T]> for ops::Range<usize> {
2061 fn get(self, slice: &[T]) -> Option<&[T]> {
2062 if self.start > self.end || self.end > slice.len() {
2066 Some(self.get_unchecked(slice))
2072 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2073 if self.start > self.end || self.end > slice.len() {
2077 Some(self.get_unchecked_mut(slice))
2083 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2084 from_raw_parts(slice.as_ptr().add(self.start), self.end - self.start)
2088 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2089 from_raw_parts_mut(slice.as_mut_ptr().add(self.start), self.end - self.start)
2093 fn index(self, slice: &[T]) -> &[T] {
2094 if self.start > self.end {
2095 slice_index_order_fail(self.start, self.end);
2096 } else if self.end > slice.len() {
2097 slice_index_len_fail(self.end, slice.len());
2100 self.get_unchecked(slice)
2105 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2106 if self.start > self.end {
2107 slice_index_order_fail(self.start, self.end);
2108 } else if self.end > slice.len() {
2109 slice_index_len_fail(self.end, slice.len());
2112 self.get_unchecked_mut(slice)
2117 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2118 impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {
2122 fn get(self, slice: &[T]) -> Option<&[T]> {
2123 (0..self.end).get(slice)
2127 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2128 (0..self.end).get_mut(slice)
2132 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2133 (0..self.end).get_unchecked(slice)
2137 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2138 (0..self.end).get_unchecked_mut(slice)
2142 fn index(self, slice: &[T]) -> &[T] {
2143 (0..self.end).index(slice)
2147 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2148 (0..self.end).index_mut(slice)
2152 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2153 impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {
2157 fn get(self, slice: &[T]) -> Option<&[T]> {
2158 (self.start..slice.len()).get(slice)
2162 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2163 (self.start..slice.len()).get_mut(slice)
2167 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2168 (self.start..slice.len()).get_unchecked(slice)
2172 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2173 (self.start..slice.len()).get_unchecked_mut(slice)
2177 fn index(self, slice: &[T]) -> &[T] {
2178 (self.start..slice.len()).index(slice)
2182 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2183 (self.start..slice.len()).index_mut(slice)
2187 #[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
2188 impl<T> SliceIndex<[T]> for ops::RangeFull {
2192 fn get(self, slice: &[T]) -> Option<&[T]> {
2197 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2202 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2207 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2212 fn index(self, slice: &[T]) -> &[T] {
2217 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2223 #[stable(feature = "inclusive_range", since = "1.26.0")]
2224 impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> {
2228 fn get(self, slice: &[T]) -> Option<&[T]> {
2229 if *self.end() == usize::max_value() { None }
2230 else { (*self.start()..self.end() + 1).get(slice) }
2234 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2235 if *self.end() == usize::max_value() { None }
2236 else { (*self.start()..self.end() + 1).get_mut(slice) }
2240 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2241 (*self.start()..self.end() + 1).get_unchecked(slice)
2245 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2246 (*self.start()..self.end() + 1).get_unchecked_mut(slice)
2250 fn index(self, slice: &[T]) -> &[T] {
2251 if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
2252 (*self.start()..self.end() + 1).index(slice)
2256 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2257 if *self.end() == usize::max_value() { slice_index_overflow_fail(); }
2258 (*self.start()..self.end() + 1).index_mut(slice)
2262 #[stable(feature = "inclusive_range", since = "1.26.0")]
2263 impl<T> SliceIndex<[T]> for ops::RangeToInclusive<usize> {
2267 fn get(self, slice: &[T]) -> Option<&[T]> {
2268 (0..=self.end).get(slice)
2272 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2273 (0..=self.end).get_mut(slice)
2277 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2278 (0..=self.end).get_unchecked(slice)
2282 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2283 (0..=self.end).get_unchecked_mut(slice)
2287 fn index(self, slice: &[T]) -> &[T] {
2288 (0..=self.end).index(slice)
2292 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2293 (0..=self.end).index_mut(slice)
2297 ////////////////////////////////////////////////////////////////////////////////
2299 ////////////////////////////////////////////////////////////////////////////////
2301 #[stable(feature = "rust1", since = "1.0.0")]
2302 impl<'a, T> Default for &'a [T] {
2303 /// Creates an empty slice.
2304 fn default() -> &'a [T] { &[] }
2307 #[stable(feature = "mut_slice_default", since = "1.5.0")]
2308 impl<'a, T> Default for &'a mut [T] {
2309 /// Creates a mutable empty slice.
2310 fn default() -> &'a mut [T] { &mut [] }
2317 #[stable(feature = "rust1", since = "1.0.0")]
2318 impl<'a, T> IntoIterator for &'a [T] {
2320 type IntoIter = Iter<'a, T>;
2322 fn into_iter(self) -> Iter<'a, T> {
2327 #[stable(feature = "rust1", since = "1.0.0")]
2328 impl<'a, T> IntoIterator for &'a mut [T] {
2329 type Item = &'a mut T;
2330 type IntoIter = IterMut<'a, T>;
2332 fn into_iter(self) -> IterMut<'a, T> {
2337 // Macro helper functions
2339 fn size_from_ptr<T>(_: *const T) -> usize {
2343 // Inlining is_empty and len makes a huge performance difference
2344 macro_rules! is_empty {
2345 // The way we encode the length of a ZST iterator, this works both for ZST
2347 ($self: ident) => {$self.ptr == $self.end}
2349 // To get rid of some bounds checks (see `position`), we compute the length in a somewhat
2350 // unexpected way. (Tested by `codegen/slice-position-bounds-check`.)
2352 ($self: ident) => {{
2353 let start = $self.ptr;
2354 let diff = ($self.end as usize).wrapping_sub(start as usize);
2355 let size = size_from_ptr(start);
2359 // Using division instead of `offset_from` helps LLVM remove bounds checks
2365 // The shared definition of the `Iter` and `IterMut` iterators
2366 macro_rules! iterator {
2367 (struct $name:ident -> $ptr:ty, $elem:ty, $raw_mut:tt, $( $mut_:tt )*) => {
2368 impl<'a, T> $name<'a, T> {
2369 // Helper function for creating a slice from the iterator.
2371 fn make_slice(&self) -> &'a [T] {
2372 unsafe { from_raw_parts(self.ptr, len!(self)) }
2375 // Helper function for moving the start of the iterator forwards by `offset` elements,
2376 // returning the old start.
2377 // Unsafe because the offset must be in-bounds or one-past-the-end.
2379 unsafe fn post_inc_start(&mut self, offset: isize) -> * $raw_mut T {
2380 if mem::size_of::<T>() == 0 {
2381 // This is *reducing* the length. `ptr` never changes with ZST.
2382 self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
2386 self.ptr = self.ptr.offset(offset);
2391 // Helper function for moving the end of the iterator backwards by `offset` elements,
2392 // returning the new end.
2393 // Unsafe because the offset must be in-bounds or one-past-the-end.
2395 unsafe fn pre_dec_end(&mut self, offset: isize) -> * $raw_mut T {
2396 if mem::size_of::<T>() == 0 {
2397 self.end = (self.end as * $raw_mut u8).wrapping_offset(-offset) as * $raw_mut T;
2400 self.end = self.end.offset(-offset);
2406 #[stable(feature = "rust1", since = "1.0.0")]
2407 impl<'a, T> ExactSizeIterator for $name<'a, T> {
2409 fn len(&self) -> usize {
2414 fn is_empty(&self) -> bool {
2419 #[stable(feature = "rust1", since = "1.0.0")]
2420 impl<'a, T> Iterator for $name<'a, T> {
2424 fn next(&mut self) -> Option<$elem> {
2425 // could be implemented with slices, but this avoids bounds checks
2427 assume(!self.ptr.is_null());
2428 if mem::size_of::<T>() != 0 {
2429 assume(!self.end.is_null());
2431 if is_empty!(self) {
2434 Some(& $( $mut_ )* *self.post_inc_start(1))
2440 fn size_hint(&self) -> (usize, Option<usize>) {
2441 let exact = len!(self);
2442 (exact, Some(exact))
2446 fn count(self) -> usize {
2451 fn nth(&mut self, n: usize) -> Option<$elem> {
2452 if n >= len!(self) {
2453 // This iterator is now empty.
2454 if mem::size_of::<T>() == 0 {
2455 // We have to do it this way as `ptr` may never be 0, but `end`
2456 // could be (due to wrapping).
2457 self.end = self.ptr;
2459 self.ptr = self.end;
2463 // We are in bounds. `offset` does the right thing even for ZSTs.
2465 let elem = Some(& $( $mut_ )* *self.ptr.add(n));
2466 self.post_inc_start((n as isize).wrapping_add(1));
2472 fn last(mut self) -> Option<$elem> {
2477 fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where
2478 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
2480 // manual unrolling is needed when there are conditional exits from the loop
2481 let mut accum = init;
2483 while len!(self) >= 4 {
2484 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2485 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2486 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2487 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2489 while !is_empty!(self) {
2490 accum = f(accum, & $( $mut_ )* *self.post_inc_start(1))?;
2497 fn fold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
2498 where Fold: FnMut(Acc, Self::Item) -> Acc,
2500 // Let LLVM unroll this, rather than using the default
2501 // impl that would force the manual unrolling above
2502 let mut accum = init;
2503 while let Some(x) = self.next() {
2504 accum = f(accum, x);
2510 #[rustc_inherit_overflow_checks]
2511 fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
2513 P: FnMut(Self::Item) -> bool,
2515 // The addition might panic on overflow.
2517 self.try_fold(0, move |i, x| {
2518 if predicate(x) { Err(i) }
2522 unsafe { assume(i < n) };
2528 fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where
2529 P: FnMut(Self::Item) -> bool,
2530 Self: Sized + ExactSizeIterator + DoubleEndedIterator
2532 // No need for an overflow check here, because `ExactSizeIterator`
2534 self.try_rfold(n, move |i, x| {
2536 if predicate(x) { Err(i) }
2540 unsafe { assume(i < n) };
2546 #[stable(feature = "rust1", since = "1.0.0")]
2547 impl<'a, T> DoubleEndedIterator for $name<'a, T> {
2549 fn next_back(&mut self) -> Option<$elem> {
2550 // could be implemented with slices, but this avoids bounds checks
2552 assume(!self.ptr.is_null());
2553 if mem::size_of::<T>() != 0 {
2554 assume(!self.end.is_null());
2556 if is_empty!(self) {
2559 Some(& $( $mut_ )* *self.pre_dec_end(1))
2565 fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where
2566 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
2568 // manual unrolling is needed when there are conditional exits from the loop
2569 let mut accum = init;
2571 while len!(self) >= 4 {
2572 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2573 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2574 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2575 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2577 // inlining is_empty everywhere makes a huge performance difference
2578 while !is_empty!(self) {
2579 accum = f(accum, & $( $mut_ )* *self.pre_dec_end(1))?;
2586 fn rfold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
2587 where Fold: FnMut(Acc, Self::Item) -> Acc,
2589 // Let LLVM unroll this, rather than using the default
2590 // impl that would force the manual unrolling above
2591 let mut accum = init;
2592 while let Some(x) = self.next_back() {
2593 accum = f(accum, x);
2599 #[stable(feature = "fused", since = "1.26.0")]
2600 impl<'a, T> FusedIterator for $name<'a, T> {}
2602 #[unstable(feature = "trusted_len", issue = "37572")]
2603 unsafe impl<'a, T> TrustedLen for $name<'a, T> {}
2607 /// Immutable slice iterator
2609 /// This struct is created by the [`iter`] method on [slices].
2616 /// // First, we declare a type which has `iter` method to get the `Iter` struct (&[usize here]):
2617 /// let slice = &[1, 2, 3];
2619 /// // Then, we iterate over it:
2620 /// for element in slice.iter() {
2621 /// println!("{}", element);
2625 /// [`iter`]: ../../std/primitive.slice.html#method.iter
2626 /// [slices]: ../../std/primitive.slice.html
2627 #[stable(feature = "rust1", since = "1.0.0")]
2628 pub struct Iter<'a, T: 'a> {
2630 end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
2631 // ptr == end is a quick test for the Iterator being empty, that works
2632 // for both ZST and non-ZST.
2633 _marker: marker::PhantomData<&'a T>,
2636 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2637 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
2638 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2639 f.debug_tuple("Iter")
2640 .field(&self.as_slice())
2645 #[stable(feature = "rust1", since = "1.0.0")]
2646 unsafe impl<'a, T: Sync> Sync for Iter<'a, T> {}
2647 #[stable(feature = "rust1", since = "1.0.0")]
2648 unsafe impl<'a, T: Sync> Send for Iter<'a, T> {}
2650 impl<'a, T> Iter<'a, T> {
2651 /// View the underlying data as a subslice of the original data.
2653 /// This has the same lifetime as the original slice, and so the
2654 /// iterator can continue to be used while this exists.
2661 /// // First, we declare a type which has the `iter` method to get the `Iter`
2662 /// // struct (&[usize here]):
2663 /// let slice = &[1, 2, 3];
2665 /// // Then, we get the iterator:
2666 /// let mut iter = slice.iter();
2667 /// // So if we print what `as_slice` method returns here, we have "[1, 2, 3]":
2668 /// println!("{:?}", iter.as_slice());
2670 /// // Next, we move to the second element of the slice:
2672 /// // Now `as_slice` returns "[2, 3]":
2673 /// println!("{:?}", iter.as_slice());
2675 #[stable(feature = "iter_to_slice", since = "1.4.0")]
2676 pub fn as_slice(&self) -> &'a [T] {
2681 iterator!{struct Iter -> *const T, &'a T, const, /* no mut */}
2683 #[stable(feature = "rust1", since = "1.0.0")]
2684 impl<'a, T> Clone for Iter<'a, T> {
2685 fn clone(&self) -> Iter<'a, T> { Iter { ptr: self.ptr, end: self.end, _marker: self._marker } }
2688 #[stable(feature = "slice_iter_as_ref", since = "1.13.0")]
2689 impl<'a, T> AsRef<[T]> for Iter<'a, T> {
2690 fn as_ref(&self) -> &[T] {
2695 /// Mutable slice iterator.
2697 /// This struct is created by the [`iter_mut`] method on [slices].
2704 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
2705 /// // struct (&[usize here]):
2706 /// let mut slice = &mut [1, 2, 3];
2708 /// // Then, we iterate over it and increment each element value:
2709 /// for element in slice.iter_mut() {
2713 /// // We now have "[2, 3, 4]":
2714 /// println!("{:?}", slice);
2717 /// [`iter_mut`]: ../../std/primitive.slice.html#method.iter_mut
2718 /// [slices]: ../../std/primitive.slice.html
2719 #[stable(feature = "rust1", since = "1.0.0")]
2720 pub struct IterMut<'a, T: 'a> {
2722 end: *mut T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
2723 // ptr == end is a quick test for the Iterator being empty, that works
2724 // for both ZST and non-ZST.
2725 _marker: marker::PhantomData<&'a mut T>,
2728 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2729 impl<'a, T: 'a + fmt::Debug> fmt::Debug for IterMut<'a, T> {
2730 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2731 f.debug_tuple("IterMut")
2732 .field(&self.make_slice())
2737 #[stable(feature = "rust1", since = "1.0.0")]
2738 unsafe impl<'a, T: Sync> Sync for IterMut<'a, T> {}
2739 #[stable(feature = "rust1", since = "1.0.0")]
2740 unsafe impl<'a, T: Send> Send for IterMut<'a, T> {}
2742 impl<'a, T> IterMut<'a, T> {
2743 /// View the underlying data as a subslice of the original data.
2745 /// To avoid creating `&mut` references that alias, this is forced
2746 /// to consume the iterator.
2753 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
2754 /// // struct (&[usize here]):
2755 /// let mut slice = &mut [1, 2, 3];
2758 /// // Then, we get the iterator:
2759 /// let mut iter = slice.iter_mut();
2760 /// // We move to next element:
2762 /// // So if we print what `into_slice` method returns here, we have "[2, 3]":
2763 /// println!("{:?}", iter.into_slice());
2766 /// // Now let's modify a value of the slice:
2768 /// // First we get back the iterator:
2769 /// let mut iter = slice.iter_mut();
2770 /// // We change the value of the first element of the slice returned by the `next` method:
2771 /// *iter.next().unwrap() += 1;
2773 /// // Now slice is "[2, 2, 3]":
2774 /// println!("{:?}", slice);
2776 #[stable(feature = "iter_to_slice", since = "1.4.0")]
2777 pub fn into_slice(self) -> &'a mut [T] {
2778 unsafe { from_raw_parts_mut(self.ptr, len!(self)) }
2782 iterator!{struct IterMut -> *mut T, &'a mut T, mut, mut}
2784 /// An internal abstraction over the splitting iterators, so that
2785 /// splitn, splitn_mut etc can be implemented once.
2787 trait SplitIter: DoubleEndedIterator {
2788 /// Marks the underlying iterator as complete, extracting the remaining
2789 /// portion of the slice.
2790 fn finish(&mut self) -> Option<Self::Item>;
2793 /// An iterator over subslices separated by elements that match a predicate
2796 /// This struct is created by the [`split`] method on [slices].
2798 /// [`split`]: ../../std/primitive.slice.html#method.split
2799 /// [slices]: ../../std/primitive.slice.html
2800 #[stable(feature = "rust1", since = "1.0.0")]
2801 pub struct Split<'a, T:'a, P> where P: FnMut(&T) -> bool {
2807 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2808 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for Split<'a, T, P> where P: FnMut(&T) -> bool {
2809 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2810 f.debug_struct("Split")
2811 .field("v", &self.v)
2812 .field("finished", &self.finished)
2817 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
2818 #[stable(feature = "rust1", since = "1.0.0")]
2819 impl<'a, T, P> Clone for Split<'a, T, P> where P: Clone + FnMut(&T) -> bool {
2820 fn clone(&self) -> Split<'a, T, P> {
2823 pred: self.pred.clone(),
2824 finished: self.finished,
2829 #[stable(feature = "rust1", since = "1.0.0")]
2830 impl<'a, T, P> Iterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
2831 type Item = &'a [T];
2834 fn next(&mut self) -> Option<&'a [T]> {
2835 if self.finished { return None; }
2837 match self.v.iter().position(|x| (self.pred)(x)) {
2838 None => self.finish(),
2840 let ret = Some(&self.v[..idx]);
2841 self.v = &self.v[idx + 1..];
2848 fn size_hint(&self) -> (usize, Option<usize>) {
2852 (1, Some(self.v.len() + 1))
2857 #[stable(feature = "rust1", since = "1.0.0")]
2858 impl<'a, T, P> DoubleEndedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
2860 fn next_back(&mut self) -> Option<&'a [T]> {
2861 if self.finished { return None; }
2863 match self.v.iter().rposition(|x| (self.pred)(x)) {
2864 None => self.finish(),
2866 let ret = Some(&self.v[idx + 1..]);
2867 self.v = &self.v[..idx];
2874 impl<'a, T, P> SplitIter for Split<'a, T, P> where P: FnMut(&T) -> bool {
2876 fn finish(&mut self) -> Option<&'a [T]> {
2877 if self.finished { None } else { self.finished = true; Some(self.v) }
2881 #[stable(feature = "fused", since = "1.26.0")]
2882 impl<'a, T, P> FusedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {}
2884 /// An iterator over the subslices of the vector which are separated
2885 /// by elements that match `pred`.
2887 /// This struct is created by the [`split_mut`] method on [slices].
2889 /// [`split_mut`]: ../../std/primitive.slice.html#method.split_mut
2890 /// [slices]: ../../std/primitive.slice.html
2891 #[stable(feature = "rust1", since = "1.0.0")]
2892 pub struct SplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
2898 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2899 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
2900 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2901 f.debug_struct("SplitMut")
2902 .field("v", &self.v)
2903 .field("finished", &self.finished)
2908 impl<'a, T, P> SplitIter for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
2910 fn finish(&mut self) -> Option<&'a mut [T]> {
2914 self.finished = true;
2915 Some(mem::replace(&mut self.v, &mut []))
2920 #[stable(feature = "rust1", since = "1.0.0")]
2921 impl<'a, T, P> Iterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
2922 type Item = &'a mut [T];
2925 fn next(&mut self) -> Option<&'a mut [T]> {
2926 if self.finished { return None; }
2928 let idx_opt = { // work around borrowck limitations
2929 let pred = &mut self.pred;
2930 self.v.iter().position(|x| (*pred)(x))
2933 None => self.finish(),
2935 let tmp = mem::replace(&mut self.v, &mut []);
2936 let (head, tail) = tmp.split_at_mut(idx);
2937 self.v = &mut tail[1..];
2944 fn size_hint(&self) -> (usize, Option<usize>) {
2948 // if the predicate doesn't match anything, we yield one slice
2949 // if it matches every element, we yield len+1 empty slices.
2950 (1, Some(self.v.len() + 1))
2955 #[stable(feature = "rust1", since = "1.0.0")]
2956 impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> where
2957 P: FnMut(&T) -> bool,
2960 fn next_back(&mut self) -> Option<&'a mut [T]> {
2961 if self.finished { return None; }
2963 let idx_opt = { // work around borrowck limitations
2964 let pred = &mut self.pred;
2965 self.v.iter().rposition(|x| (*pred)(x))
2968 None => self.finish(),
2970 let tmp = mem::replace(&mut self.v, &mut []);
2971 let (head, tail) = tmp.split_at_mut(idx);
2973 Some(&mut tail[1..])
2979 #[stable(feature = "fused", since = "1.26.0")]
2980 impl<'a, T, P> FusedIterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {}
2982 /// An iterator over subslices separated by elements that match a predicate
2983 /// function, starting from the end of the slice.
2985 /// This struct is created by the [`rsplit`] method on [slices].
2987 /// [`rsplit`]: ../../std/primitive.slice.html#method.rsplit
2988 /// [slices]: ../../std/primitive.slice.html
2989 #[stable(feature = "slice_rsplit", since = "1.27.0")]
2990 #[derive(Clone)] // Is this correct, or does it incorrectly require `T: Clone`?
2991 pub struct RSplit<'a, T:'a, P> where P: FnMut(&T) -> bool {
2992 inner: Split<'a, T, P>
2995 #[stable(feature = "slice_rsplit", since = "1.27.0")]
2996 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
2997 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2998 f.debug_struct("RSplit")
2999 .field("v", &self.inner.v)
3000 .field("finished", &self.inner.finished)
3005 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3006 impl<'a, T, P> Iterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3007 type Item = &'a [T];
3010 fn next(&mut self) -> Option<&'a [T]> {
3011 self.inner.next_back()
3015 fn size_hint(&self) -> (usize, Option<usize>) {
3016 self.inner.size_hint()
3020 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3021 impl<'a, T, P> DoubleEndedIterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3023 fn next_back(&mut self) -> Option<&'a [T]> {
3028 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3029 impl<'a, T, P> SplitIter for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3031 fn finish(&mut self) -> Option<&'a [T]> {
3036 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3037 impl<'a, T, P> FusedIterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {}
3039 /// An iterator over the subslices of the vector which are separated
3040 /// by elements that match `pred`, starting from the end of the slice.
3042 /// This struct is created by the [`rsplit_mut`] method on [slices].
3044 /// [`rsplit_mut`]: ../../std/primitive.slice.html#method.rsplit_mut
3045 /// [slices]: ../../std/primitive.slice.html
3046 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3047 pub struct RSplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
3048 inner: SplitMut<'a, T, P>
3051 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3052 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3053 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3054 f.debug_struct("RSplitMut")
3055 .field("v", &self.inner.v)
3056 .field("finished", &self.inner.finished)
3061 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3062 impl<'a, T, P> SplitIter for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3064 fn finish(&mut self) -> Option<&'a mut [T]> {
3069 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3070 impl<'a, T, P> Iterator for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3071 type Item = &'a mut [T];
3074 fn next(&mut self) -> Option<&'a mut [T]> {
3075 self.inner.next_back()
3079 fn size_hint(&self) -> (usize, Option<usize>) {
3080 self.inner.size_hint()
3084 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3085 impl<'a, T, P> DoubleEndedIterator for RSplitMut<'a, T, P> where
3086 P: FnMut(&T) -> bool,
3089 fn next_back(&mut self) -> Option<&'a mut [T]> {
3094 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3095 impl<'a, T, P> FusedIterator for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {}
3097 /// An private iterator over subslices separated by elements that
3098 /// match a predicate function, splitting at most a fixed number of
3101 struct GenericSplitN<I> {
3106 impl<T, I: SplitIter<Item=T>> Iterator for GenericSplitN<I> {
3110 fn next(&mut self) -> Option<T> {
3113 1 => { self.count -= 1; self.iter.finish() }
3114 _ => { self.count -= 1; self.iter.next() }
3119 fn size_hint(&self) -> (usize, Option<usize>) {
3120 let (lower, upper_opt) = self.iter.size_hint();
3121 (lower, upper_opt.map(|upper| cmp::min(self.count, upper)))
3125 /// An iterator over subslices separated by elements that match a predicate
3126 /// function, limited to a given number of splits.
3128 /// This struct is created by the [`splitn`] method on [slices].
3130 /// [`splitn`]: ../../std/primitive.slice.html#method.splitn
3131 /// [slices]: ../../std/primitive.slice.html
3132 #[stable(feature = "rust1", since = "1.0.0")]
3133 pub struct SplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3134 inner: GenericSplitN<Split<'a, T, P>>
3137 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3138 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitN<'a, T, P> where P: FnMut(&T) -> bool {
3139 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3140 f.debug_struct("SplitN")
3141 .field("inner", &self.inner)
3146 /// An iterator over subslices separated by elements that match a
3147 /// predicate function, limited to a given number of splits, starting
3148 /// from the end of the slice.
3150 /// This struct is created by the [`rsplitn`] method on [slices].
3152 /// [`rsplitn`]: ../../std/primitive.slice.html#method.rsplitn
3153 /// [slices]: ../../std/primitive.slice.html
3154 #[stable(feature = "rust1", since = "1.0.0")]
3155 pub struct RSplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3156 inner: GenericSplitN<RSplit<'a, T, P>>
3159 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3160 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitN<'a, T, P> where P: FnMut(&T) -> bool {
3161 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3162 f.debug_struct("RSplitN")
3163 .field("inner", &self.inner)
3168 /// An iterator over subslices separated by elements that match a predicate
3169 /// function, limited to a given number of splits.
3171 /// This struct is created by the [`splitn_mut`] method on [slices].
3173 /// [`splitn_mut`]: ../../std/primitive.slice.html#method.splitn_mut
3174 /// [slices]: ../../std/primitive.slice.html
3175 #[stable(feature = "rust1", since = "1.0.0")]
3176 pub struct SplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3177 inner: GenericSplitN<SplitMut<'a, T, P>>
3180 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3181 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitNMut<'a, T, P> where P: FnMut(&T) -> bool {
3182 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3183 f.debug_struct("SplitNMut")
3184 .field("inner", &self.inner)
3189 /// An iterator over subslices separated by elements that match a
3190 /// predicate function, limited to a given number of splits, starting
3191 /// from the end of the slice.
3193 /// This struct is created by the [`rsplitn_mut`] method on [slices].
3195 /// [`rsplitn_mut`]: ../../std/primitive.slice.html#method.rsplitn_mut
3196 /// [slices]: ../../std/primitive.slice.html
3197 #[stable(feature = "rust1", since = "1.0.0")]
3198 pub struct RSplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3199 inner: GenericSplitN<RSplitMut<'a, T, P>>
3202 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3203 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitNMut<'a, T, P> where P: FnMut(&T) -> bool {
3204 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3205 f.debug_struct("RSplitNMut")
3206 .field("inner", &self.inner)
3211 macro_rules! forward_iterator {
3212 ($name:ident: $elem:ident, $iter_of:ty) => {
3213 #[stable(feature = "rust1", since = "1.0.0")]
3214 impl<'a, $elem, P> Iterator for $name<'a, $elem, P> where
3215 P: FnMut(&T) -> bool
3217 type Item = $iter_of;
3220 fn next(&mut self) -> Option<$iter_of> {
3225 fn size_hint(&self) -> (usize, Option<usize>) {
3226 self.inner.size_hint()
3230 #[stable(feature = "fused", since = "1.26.0")]
3231 impl<'a, $elem, P> FusedIterator for $name<'a, $elem, P>
3232 where P: FnMut(&T) -> bool {}
3236 forward_iterator! { SplitN: T, &'a [T] }
3237 forward_iterator! { RSplitN: T, &'a [T] }
3238 forward_iterator! { SplitNMut: T, &'a mut [T] }
3239 forward_iterator! { RSplitNMut: T, &'a mut [T] }
3241 /// An iterator over overlapping subslices of length `size`.
3243 /// This struct is created by the [`windows`] method on [slices].
3245 /// [`windows`]: ../../std/primitive.slice.html#method.windows
3246 /// [slices]: ../../std/primitive.slice.html
3248 #[stable(feature = "rust1", since = "1.0.0")]
3249 pub struct Windows<'a, T:'a> {
3254 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3255 #[stable(feature = "rust1", since = "1.0.0")]
3256 impl<'a, T> Clone for Windows<'a, T> {
3257 fn clone(&self) -> Windows<'a, T> {
3265 #[stable(feature = "rust1", since = "1.0.0")]
3266 impl<'a, T> Iterator for Windows<'a, T> {
3267 type Item = &'a [T];
3270 fn next(&mut self) -> Option<&'a [T]> {
3271 if self.size > self.v.len() {
3274 let ret = Some(&self.v[..self.size]);
3275 self.v = &self.v[1..];
3281 fn size_hint(&self) -> (usize, Option<usize>) {
3282 if self.size > self.v.len() {
3285 let size = self.v.len() - self.size + 1;
3291 fn count(self) -> usize {
3296 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3297 let (end, overflow) = self.size.overflowing_add(n);
3298 if end > self.v.len() || overflow {
3302 let nth = &self.v[n..end];
3303 self.v = &self.v[n+1..];
3309 fn last(self) -> Option<Self::Item> {
3310 if self.size > self.v.len() {
3313 let start = self.v.len() - self.size;
3314 Some(&self.v[start..])
3319 #[stable(feature = "rust1", since = "1.0.0")]
3320 impl<'a, T> DoubleEndedIterator for Windows<'a, T> {
3322 fn next_back(&mut self) -> Option<&'a [T]> {
3323 if self.size > self.v.len() {
3326 let ret = Some(&self.v[self.v.len()-self.size..]);
3327 self.v = &self.v[..self.v.len()-1];
3333 #[stable(feature = "rust1", since = "1.0.0")]
3334 impl<'a, T> ExactSizeIterator for Windows<'a, T> {}
3336 #[unstable(feature = "trusted_len", issue = "37572")]
3337 unsafe impl<'a, T> TrustedLen for Windows<'a, T> {}
3339 #[stable(feature = "fused", since = "1.26.0")]
3340 impl<'a, T> FusedIterator for Windows<'a, T> {}
3343 unsafe impl<'a, T> TrustedRandomAccess for Windows<'a, T> {
3344 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3345 from_raw_parts(self.v.as_ptr().add(i), self.size)
3347 fn may_have_side_effect() -> bool { false }
3350 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
3353 /// When the slice len is not evenly divided by the chunk size, the last slice
3354 /// of the iteration will be the remainder.
3356 /// This struct is created by the [`chunks`] method on [slices].
3358 /// [`chunks`]: ../../std/primitive.slice.html#method.chunks
3359 /// [slices]: ../../std/primitive.slice.html
3361 #[stable(feature = "rust1", since = "1.0.0")]
3362 pub struct Chunks<'a, T:'a> {
3367 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3368 #[stable(feature = "rust1", since = "1.0.0")]
3369 impl<'a, T> Clone for Chunks<'a, T> {
3370 fn clone(&self) -> Chunks<'a, T> {
3373 chunk_size: self.chunk_size,
3378 #[stable(feature = "rust1", since = "1.0.0")]
3379 impl<'a, T> Iterator for Chunks<'a, T> {
3380 type Item = &'a [T];
3383 fn next(&mut self) -> Option<&'a [T]> {
3384 if self.v.is_empty() {
3387 let chunksz = cmp::min(self.v.len(), self.chunk_size);
3388 let (fst, snd) = self.v.split_at(chunksz);
3395 fn size_hint(&self) -> (usize, Option<usize>) {
3396 if self.v.is_empty() {
3399 let n = self.v.len() / self.chunk_size;
3400 let rem = self.v.len() % self.chunk_size;
3401 let n = if rem > 0 { n+1 } else { n };
3407 fn count(self) -> usize {
3412 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3413 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3414 if start >= self.v.len() || overflow {
3418 let end = match start.checked_add(self.chunk_size) {
3419 Some(sum) => cmp::min(self.v.len(), sum),
3420 None => self.v.len(),
3422 let nth = &self.v[start..end];
3423 self.v = &self.v[end..];
3429 fn last(self) -> Option<Self::Item> {
3430 if self.v.is_empty() {
3433 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
3434 Some(&self.v[start..])
3439 #[stable(feature = "rust1", since = "1.0.0")]
3440 impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
3442 fn next_back(&mut self) -> Option<&'a [T]> {
3443 if self.v.is_empty() {
3446 let remainder = self.v.len() % self.chunk_size;
3447 let chunksz = if remainder != 0 { remainder } else { self.chunk_size };
3448 let (fst, snd) = self.v.split_at(self.v.len() - chunksz);
3455 #[stable(feature = "rust1", since = "1.0.0")]
3456 impl<'a, T> ExactSizeIterator for Chunks<'a, T> {}
3458 #[unstable(feature = "trusted_len", issue = "37572")]
3459 unsafe impl<'a, T> TrustedLen for Chunks<'a, T> {}
3461 #[stable(feature = "fused", since = "1.26.0")]
3462 impl<'a, T> FusedIterator for Chunks<'a, T> {}
3465 unsafe impl<'a, T> TrustedRandomAccess for Chunks<'a, T> {
3466 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3467 let start = i * self.chunk_size;
3468 let end = match start.checked_add(self.chunk_size) {
3469 None => self.v.len(),
3470 Some(end) => cmp::min(end, self.v.len()),
3472 from_raw_parts(self.v.as_ptr().add(start), end - start)
3474 fn may_have_side_effect() -> bool { false }
3477 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3478 /// elements at a time). When the slice len is not evenly divided by the chunk
3479 /// size, the last slice of the iteration will be the remainder.
3481 /// This struct is created by the [`chunks_mut`] method on [slices].
3483 /// [`chunks_mut`]: ../../std/primitive.slice.html#method.chunks_mut
3484 /// [slices]: ../../std/primitive.slice.html
3486 #[stable(feature = "rust1", since = "1.0.0")]
3487 pub struct ChunksMut<'a, T:'a> {
3492 #[stable(feature = "rust1", since = "1.0.0")]
3493 impl<'a, T> Iterator for ChunksMut<'a, T> {
3494 type Item = &'a mut [T];
3497 fn next(&mut self) -> Option<&'a mut [T]> {
3498 if self.v.is_empty() {
3501 let sz = cmp::min(self.v.len(), self.chunk_size);
3502 let tmp = mem::replace(&mut self.v, &mut []);
3503 let (head, tail) = tmp.split_at_mut(sz);
3510 fn size_hint(&self) -> (usize, Option<usize>) {
3511 if self.v.is_empty() {
3514 let n = self.v.len() / self.chunk_size;
3515 let rem = self.v.len() % self.chunk_size;
3516 let n = if rem > 0 { n + 1 } else { n };
3522 fn count(self) -> usize {
3527 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
3528 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3529 if start >= self.v.len() || overflow {
3533 let end = match start.checked_add(self.chunk_size) {
3534 Some(sum) => cmp::min(self.v.len(), sum),
3535 None => self.v.len(),
3537 let tmp = mem::replace(&mut self.v, &mut []);
3538 let (head, tail) = tmp.split_at_mut(end);
3539 let (_, nth) = head.split_at_mut(start);
3546 fn last(self) -> Option<Self::Item> {
3547 if self.v.is_empty() {
3550 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
3551 Some(&mut self.v[start..])
3556 #[stable(feature = "rust1", since = "1.0.0")]
3557 impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
3559 fn next_back(&mut self) -> Option<&'a mut [T]> {
3560 if self.v.is_empty() {
3563 let remainder = self.v.len() % self.chunk_size;
3564 let sz = if remainder != 0 { remainder } else { self.chunk_size };
3565 let tmp = mem::replace(&mut self.v, &mut []);
3566 let tmp_len = tmp.len();
3567 let (head, tail) = tmp.split_at_mut(tmp_len - sz);
3574 #[stable(feature = "rust1", since = "1.0.0")]
3575 impl<'a, T> ExactSizeIterator for ChunksMut<'a, T> {}
3577 #[unstable(feature = "trusted_len", issue = "37572")]
3578 unsafe impl<'a, T> TrustedLen for ChunksMut<'a, T> {}
3580 #[stable(feature = "fused", since = "1.26.0")]
3581 impl<'a, T> FusedIterator for ChunksMut<'a, T> {}
3584 unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> {
3585 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
3586 let start = i * self.chunk_size;
3587 let end = match start.checked_add(self.chunk_size) {
3588 None => self.v.len(),
3589 Some(end) => cmp::min(end, self.v.len()),
3591 from_raw_parts_mut(self.v.as_mut_ptr().add(start), end - start)
3593 fn may_have_side_effect() -> bool { false }
3596 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
3599 /// When the slice len is not evenly divided by the chunk size, the last
3600 /// up to `chunk_size-1` elements will be omitted but can be retrieved from
3601 /// the [`remainder`] function from the iterator.
3603 /// This struct is created by the [`exact_chunks`] method on [slices].
3605 /// [`exact_chunks`]: ../../std/primitive.slice.html#method.exact_chunks
3606 /// [`remainder`]: ../../std/slice/struct.ExactChunks.html#method.remainder
3607 /// [slices]: ../../std/primitive.slice.html
3609 #[unstable(feature = "exact_chunks", issue = "47115")]
3610 pub struct ExactChunks<'a, T:'a> {
3616 #[unstable(feature = "exact_chunks", issue = "47115")]
3617 impl<'a, T> ExactChunks<'a, T> {
3618 /// Return the remainder of the original slice that is not going to be
3619 /// returned by the iterator. The returned slice has at most `chunk_size-1`
3621 pub fn remainder(&self) -> &'a [T] {
3626 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3627 #[unstable(feature = "exact_chunks", issue = "47115")]
3628 impl<'a, T> Clone for ExactChunks<'a, T> {
3629 fn clone(&self) -> ExactChunks<'a, T> {
3633 chunk_size: self.chunk_size,
3638 #[unstable(feature = "exact_chunks", issue = "47115")]
3639 impl<'a, T> Iterator for ExactChunks<'a, T> {
3640 type Item = &'a [T];
3643 fn next(&mut self) -> Option<&'a [T]> {
3644 if self.v.len() < self.chunk_size {
3647 let (fst, snd) = self.v.split_at(self.chunk_size);
3654 fn size_hint(&self) -> (usize, Option<usize>) {
3655 let n = self.v.len() / self.chunk_size;
3660 fn count(self) -> usize {
3665 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3666 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3667 if start >= self.v.len() || overflow {
3671 let (_, snd) = self.v.split_at(start);
3678 fn last(mut self) -> Option<Self::Item> {
3683 #[unstable(feature = "exact_chunks", issue = "47115")]
3684 impl<'a, T> DoubleEndedIterator for ExactChunks<'a, T> {
3686 fn next_back(&mut self) -> Option<&'a [T]> {
3687 if self.v.len() < self.chunk_size {
3690 let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size);
3697 #[unstable(feature = "exact_chunks", issue = "47115")]
3698 impl<'a, T> ExactSizeIterator for ExactChunks<'a, T> {
3699 fn is_empty(&self) -> bool {
3704 #[unstable(feature = "trusted_len", issue = "37572")]
3705 unsafe impl<'a, T> TrustedLen for ExactChunks<'a, T> {}
3707 #[unstable(feature = "exact_chunks", issue = "47115")]
3708 impl<'a, T> FusedIterator for ExactChunks<'a, T> {}
3711 unsafe impl<'a, T> TrustedRandomAccess for ExactChunks<'a, T> {
3712 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3713 let start = i * self.chunk_size;
3714 from_raw_parts(self.v.as_ptr().add(start), self.chunk_size)
3716 fn may_have_side_effect() -> bool { false }
3719 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3720 /// elements at a time).
3722 /// When the slice len is not evenly divided by the chunk size, the last up to
3723 /// `chunk_size-1` elements will be omitted but can be retrieved from the
3724 /// [`into_remainder`] function from the iterator.
3726 /// This struct is created by the [`exact_chunks_mut`] method on [slices].
3728 /// [`exact_chunks_mut`]: ../../std/primitive.slice.html#method.exact_chunks_mut
3729 /// [`into_remainder`]: ../../std/slice/struct.ExactChunksMut.html#method.into_remainder
3730 /// [slices]: ../../std/primitive.slice.html
3732 #[unstable(feature = "exact_chunks", issue = "47115")]
3733 pub struct ExactChunksMut<'a, T:'a> {
3739 #[unstable(feature = "exact_chunks", issue = "47115")]
3740 impl<'a, T> ExactChunksMut<'a, T> {
3741 /// Return the remainder of the original slice that is not going to be
3742 /// returned by the iterator. The returned slice has at most `chunk_size-1`
3744 pub fn into_remainder(self) -> &'a mut [T] {
3749 #[unstable(feature = "exact_chunks", issue = "47115")]
3750 impl<'a, T> Iterator for ExactChunksMut<'a, T> {
3751 type Item = &'a mut [T];
3754 fn next(&mut self) -> Option<&'a mut [T]> {
3755 if self.v.len() < self.chunk_size {
3758 let tmp = mem::replace(&mut self.v, &mut []);
3759 let (head, tail) = tmp.split_at_mut(self.chunk_size);
3766 fn size_hint(&self) -> (usize, Option<usize>) {
3767 let n = self.v.len() / self.chunk_size;
3772 fn count(self) -> usize {
3777 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
3778 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3779 if start >= self.v.len() || overflow {
3783 let tmp = mem::replace(&mut self.v, &mut []);
3784 let (_, snd) = tmp.split_at_mut(start);
3791 fn last(mut self) -> Option<Self::Item> {
3796 #[unstable(feature = "exact_chunks", issue = "47115")]
3797 impl<'a, T> DoubleEndedIterator for ExactChunksMut<'a, T> {
3799 fn next_back(&mut self) -> Option<&'a mut [T]> {
3800 if self.v.len() < self.chunk_size {
3803 let tmp = mem::replace(&mut self.v, &mut []);
3804 let tmp_len = tmp.len();
3805 let (head, tail) = tmp.split_at_mut(tmp_len - self.chunk_size);
3812 #[unstable(feature = "exact_chunks", issue = "47115")]
3813 impl<'a, T> ExactSizeIterator for ExactChunksMut<'a, T> {
3814 fn is_empty(&self) -> bool {
3819 #[unstable(feature = "trusted_len", issue = "37572")]
3820 unsafe impl<'a, T> TrustedLen for ExactChunksMut<'a, T> {}
3822 #[unstable(feature = "exact_chunks", issue = "47115")]
3823 impl<'a, T> FusedIterator for ExactChunksMut<'a, T> {}
3826 unsafe impl<'a, T> TrustedRandomAccess for ExactChunksMut<'a, T> {
3827 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
3828 let start = i * self.chunk_size;
3829 from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size)
3831 fn may_have_side_effect() -> bool { false }
3838 /// Forms a slice from a pointer and a length.
3840 /// The `len` argument is the number of **elements**, not the number of bytes.
3844 /// This function is unsafe as there is no guarantee that the given pointer is
3845 /// valid for `len` elements, nor whether the lifetime inferred is a suitable
3846 /// lifetime for the returned slice.
3848 /// `data` must be non-null and aligned, even for zero-length slices. One
3849 /// reason for this is that enum layout optimizations may rely on references
3850 /// (including slices of any length) being aligned and non-null to distinguish
3851 /// them from other data. You can obtain a pointer that is usable as `data`
3852 /// for zero-length slices using [`NonNull::dangling()`].
3856 /// The lifetime for the returned slice is inferred from its usage. To
3857 /// prevent accidental misuse, it's suggested to tie the lifetime to whichever
3858 /// source lifetime is safe in the context, such as by providing a helper
3859 /// function taking the lifetime of a host value for the slice, or by explicit
3867 /// // manifest a slice for a single element
3869 /// let ptr = &x as *const _;
3870 /// let slice = unsafe { slice::from_raw_parts(ptr, 1) };
3871 /// assert_eq!(slice[0], 42);
3874 /// [`NonNull::dangling()`]: ../../std/ptr/struct.NonNull.html#method.dangling
3876 #[stable(feature = "rust1", since = "1.0.0")]
3877 pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
3878 debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
3879 Repr { raw: FatPtr { data, len } }.rust
3882 /// Performs the same functionality as [`from_raw_parts`], except that a
3883 /// mutable slice is returned.
3885 /// This function is unsafe for the same reasons as [`from_raw_parts`], as well
3886 /// as not being able to provide a non-aliasing guarantee of the returned
3887 /// mutable slice. `data` must be non-null and aligned even for zero-length
3888 /// slices as with [`from_raw_parts`]. See the documentation of
3889 /// [`from_raw_parts`] for more details.
3891 /// [`from_raw_parts`]: ../../std/slice/fn.from_raw_parts.html
3893 #[stable(feature = "rust1", since = "1.0.0")]
3894 pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] {
3895 debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
3896 Repr { raw: FatPtr { data, len} }.rust_mut
3899 /// Converts a reference to T into a slice of length 1 (without copying).
3900 #[stable(feature = "from_ref", since = "1.28.0")]
3901 pub fn from_ref<T>(s: &T) -> &[T] {
3903 from_raw_parts(s, 1)
3907 /// Converts a reference to T into a slice of length 1 (without copying).
3908 #[stable(feature = "from_ref", since = "1.28.0")]
3909 pub fn from_mut<T>(s: &mut T) -> &mut [T] {
3911 from_raw_parts_mut(s, 1)
3915 // This function is public only because there is no other way to unit test heapsort.
3916 #[unstable(feature = "sort_internals", reason = "internal to sort module", issue = "0")]
3918 pub fn heapsort<T, F>(v: &mut [T], mut is_less: F)
3919 where F: FnMut(&T, &T) -> bool
3921 sort::heapsort(v, &mut is_less);
3925 // Comparison traits
3929 /// Calls implementation provided memcmp.
3931 /// Interprets the data as u8.
3933 /// Returns 0 for equal, < 0 for less than and > 0 for greater
3935 // FIXME(#32610): Return type should be c_int
3936 fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32;
3939 #[stable(feature = "rust1", since = "1.0.0")]
3940 impl<A, B> PartialEq<[B]> for [A] where A: PartialEq<B> {
3941 fn eq(&self, other: &[B]) -> bool {
3942 SlicePartialEq::equal(self, other)
3945 fn ne(&self, other: &[B]) -> bool {
3946 SlicePartialEq::not_equal(self, other)
3950 #[stable(feature = "rust1", since = "1.0.0")]
3951 impl<T: Eq> Eq for [T] {}
3953 /// Implements comparison of vectors lexicographically.
3954 #[stable(feature = "rust1", since = "1.0.0")]
3955 impl<T: Ord> Ord for [T] {
3956 fn cmp(&self, other: &[T]) -> Ordering {
3957 SliceOrd::compare(self, other)
3961 /// Implements comparison of vectors lexicographically.
3962 #[stable(feature = "rust1", since = "1.0.0")]
3963 impl<T: PartialOrd> PartialOrd for [T] {
3964 fn partial_cmp(&self, other: &[T]) -> Option<Ordering> {
3965 SlicePartialOrd::partial_compare(self, other)
3970 // intermediate trait for specialization of slice's PartialEq
3971 trait SlicePartialEq<B> {
3972 fn equal(&self, other: &[B]) -> bool;
3974 fn not_equal(&self, other: &[B]) -> bool { !self.equal(other) }
3977 // Generic slice equality
3978 impl<A, B> SlicePartialEq<B> for [A]
3979 where A: PartialEq<B>
3981 default fn equal(&self, other: &[B]) -> bool {
3982 if self.len() != other.len() {
3986 for i in 0..self.len() {
3987 if !self[i].eq(&other[i]) {
3996 // Use memcmp for bytewise equality when the types allow
3997 impl<A> SlicePartialEq<A> for [A]
3998 where A: PartialEq<A> + BytewiseEquality
4000 fn equal(&self, other: &[A]) -> bool {
4001 if self.len() != other.len() {
4004 if self.as_ptr() == other.as_ptr() {
4008 let size = mem::size_of_val(self);
4009 memcmp(self.as_ptr() as *const u8,
4010 other.as_ptr() as *const u8, size) == 0
4016 // intermediate trait for specialization of slice's PartialOrd
4017 trait SlicePartialOrd<B> {
4018 fn partial_compare(&self, other: &[B]) -> Option<Ordering>;
4021 impl<A> SlicePartialOrd<A> for [A]
4024 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
4025 let l = cmp::min(self.len(), other.len());
4027 // Slice to the loop iteration range to enable bound check
4028 // elimination in the compiler
4029 let lhs = &self[..l];
4030 let rhs = &other[..l];
4033 match lhs[i].partial_cmp(&rhs[i]) {
4034 Some(Ordering::Equal) => (),
4035 non_eq => return non_eq,
4039 self.len().partial_cmp(&other.len())
4043 impl<A> SlicePartialOrd<A> for [A]
4046 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
4047 Some(SliceOrd::compare(self, other))
4052 // intermediate trait for specialization of slice's Ord
4054 fn compare(&self, other: &[B]) -> Ordering;
4057 impl<A> SliceOrd<A> for [A]
4060 default fn compare(&self, other: &[A]) -> Ordering {
4061 let l = cmp::min(self.len(), other.len());
4063 // Slice to the loop iteration range to enable bound check
4064 // elimination in the compiler
4065 let lhs = &self[..l];
4066 let rhs = &other[..l];
4069 match lhs[i].cmp(&rhs[i]) {
4070 Ordering::Equal => (),
4071 non_eq => return non_eq,
4075 self.len().cmp(&other.len())
4079 // memcmp compares a sequence of unsigned bytes lexicographically.
4080 // this matches the order we want for [u8], but no others (not even [i8]).
4081 impl SliceOrd<u8> for [u8] {
4083 fn compare(&self, other: &[u8]) -> Ordering {
4084 let order = unsafe {
4085 memcmp(self.as_ptr(), other.as_ptr(),
4086 cmp::min(self.len(), other.len()))
4089 self.len().cmp(&other.len())
4090 } else if order < 0 {
4099 /// Trait implemented for types that can be compared for equality using
4100 /// their bytewise representation
4101 trait BytewiseEquality { }
4103 macro_rules! impl_marker_for {
4104 ($traitname:ident, $($ty:ty)*) => {
4106 impl $traitname for $ty { }
4111 impl_marker_for!(BytewiseEquality,
4112 u8 i8 u16 i16 u32 i32 u64 i64 usize isize char bool);
4115 unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {
4116 unsafe fn get_unchecked(&mut self, i: usize) -> &'a T {
4119 fn may_have_side_effect() -> bool { false }
4123 unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> {
4124 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut T {
4125 &mut *self.ptr.add(i)
4127 fn may_have_side_effect() -> bool { false }
4130 trait SliceContains: Sized {
4131 fn slice_contains(&self, x: &[Self]) -> bool;
4134 impl<T> SliceContains for T where T: PartialEq {
4135 default fn slice_contains(&self, x: &[Self]) -> bool {
4136 x.iter().any(|y| *y == *self)
4140 impl SliceContains for u8 {
4141 fn slice_contains(&self, x: &[Self]) -> bool {
4142 memchr::memchr(*self, x).is_some()
4146 impl SliceContains for i8 {
4147 fn slice_contains(&self, x: &[Self]) -> bool {
4148 let byte = *self as u8;
4149 let bytes: &[u8] = unsafe { from_raw_parts(x.as_ptr() as *const u8, x.len()) };
4150 memchr::memchr(byte, bytes).is_some()