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 // Since slices don't support inherent methods; all operations
25 // on them are defined on traits, which are then re-exported from
26 // the prelude for convenience. So there are a lot of traits here.
28 // The layout of this file is thus:
30 // * Slice-specific 'extension' traits and their implementations. This
31 // is where most of the slice API resides.
32 // * Implementations of a few common traits with important slice ops.
33 // * Definitions of a bunch of iterators.
35 // * The `raw` and `bytes` submodules.
36 // * Boilerplate trait implementations.
38 use cmp::Ordering::{self, Less, Equal, Greater};
41 use intrinsics::assume;
43 use ops::{FnMut, Try, self};
45 use option::Option::{None, Some};
47 use result::Result::{Ok, Err};
50 use marker::{Copy, Send, Sync, Sized, self};
51 use iter_private::TrustedRandomAccess;
53 #[unstable(feature = "slice_internals", issue = "0",
54 reason = "exposed from core to be reused in std; use the memchr crate")]
55 /// Pure rust memchr implementation, taken from rust-memchr
62 union Repr<'a, T: 'a> {
64 rust_mut: &'a mut [T],
78 // Use macros to be generic over const/mut
79 macro_rules! slice_offset {
80 ($ptr:expr, $by:expr) => {{
82 if size_from_ptr(ptr) == 0 {
83 (ptr as *mut i8).wrapping_offset($by) as _
90 // make a &T from a *const T
91 macro_rules! make_ref {
94 if size_from_ptr(ptr) == 0 {
95 // Use a non-null pointer value
103 // make a &mut T from a *mut T
104 macro_rules! make_ref_mut {
107 if size_from_ptr(ptr) == 0 {
108 // Use a non-null pointer value
119 /// Returns the number of elements in the slice.
124 /// let a = [1, 2, 3];
125 /// assert_eq!(a.len(), 3);
127 #[stable(feature = "rust1", since = "1.0.0")]
129 #[rustc_const_unstable(feature = "const_slice_len")]
130 pub const fn len(&self) -> usize {
132 Repr { rust: self }.raw.len
136 /// Returns `true` if the slice has a length of 0.
141 /// let a = [1, 2, 3];
142 /// assert!(!a.is_empty());
144 #[stable(feature = "rust1", since = "1.0.0")]
146 #[rustc_const_unstable(feature = "const_slice_len")]
147 pub const fn is_empty(&self) -> bool {
151 /// Returns the first element of the slice, or `None` if it is empty.
156 /// let v = [10, 40, 30];
157 /// assert_eq!(Some(&10), v.first());
159 /// let w: &[i32] = &[];
160 /// assert_eq!(None, w.first());
162 #[stable(feature = "rust1", since = "1.0.0")]
164 pub fn first(&self) -> Option<&T> {
165 if self.is_empty() { None } else { Some(&self[0]) }
168 /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
173 /// let x = &mut [0, 1, 2];
175 /// if let Some(first) = x.first_mut() {
178 /// assert_eq!(x, &[5, 1, 2]);
180 #[stable(feature = "rust1", since = "1.0.0")]
182 pub fn first_mut(&mut self) -> Option<&mut T> {
183 if self.is_empty() { None } else { Some(&mut self[0]) }
186 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
191 /// let x = &[0, 1, 2];
193 /// if let Some((first, elements)) = x.split_first() {
194 /// assert_eq!(first, &0);
195 /// assert_eq!(elements, &[1, 2]);
198 #[stable(feature = "slice_splits", since = "1.5.0")]
200 pub fn split_first(&self) -> Option<(&T, &[T])> {
201 if self.is_empty() { None } else { Some((&self[0], &self[1..])) }
204 /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
209 /// let x = &mut [0, 1, 2];
211 /// if let Some((first, elements)) = x.split_first_mut() {
216 /// assert_eq!(x, &[3, 4, 5]);
218 #[stable(feature = "slice_splits", since = "1.5.0")]
220 pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
221 if self.is_empty() { None } else {
222 let split = self.split_at_mut(1);
223 Some((&mut split.0[0], split.1))
227 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
232 /// let x = &[0, 1, 2];
234 /// if let Some((last, elements)) = x.split_last() {
235 /// assert_eq!(last, &2);
236 /// assert_eq!(elements, &[0, 1]);
239 #[stable(feature = "slice_splits", since = "1.5.0")]
241 pub fn split_last(&self) -> Option<(&T, &[T])> {
242 let len = self.len();
243 if len == 0 { None } else { Some((&self[len - 1], &self[..(len - 1)])) }
246 /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
251 /// let x = &mut [0, 1, 2];
253 /// if let Some((last, elements)) = x.split_last_mut() {
258 /// assert_eq!(x, &[4, 5, 3]);
260 #[stable(feature = "slice_splits", since = "1.5.0")]
262 pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
263 let len = self.len();
264 if len == 0 { None } else {
265 let split = self.split_at_mut(len - 1);
266 Some((&mut split.1[0], split.0))
271 /// Returns the last element of the slice, or `None` if it is empty.
276 /// let v = [10, 40, 30];
277 /// assert_eq!(Some(&30), v.last());
279 /// let w: &[i32] = &[];
280 /// assert_eq!(None, w.last());
282 #[stable(feature = "rust1", since = "1.0.0")]
284 pub fn last(&self) -> Option<&T> {
285 if self.is_empty() { None } else { Some(&self[self.len() - 1]) }
288 /// Returns a mutable pointer to the last item in the slice.
293 /// let x = &mut [0, 1, 2];
295 /// if let Some(last) = x.last_mut() {
298 /// assert_eq!(x, &[0, 1, 10]);
300 #[stable(feature = "rust1", since = "1.0.0")]
302 pub fn last_mut(&mut self) -> Option<&mut T> {
303 let len = self.len();
304 if len == 0 { return None; }
305 Some(&mut self[len - 1])
308 /// Returns a reference to an element or subslice depending on the type of
311 /// - If given a position, returns a reference to the element at that
312 /// position or `None` if out of bounds.
313 /// - If given a range, returns the subslice corresponding to that range,
314 /// or `None` if out of bounds.
319 /// let v = [10, 40, 30];
320 /// assert_eq!(Some(&40), v.get(1));
321 /// assert_eq!(Some(&[10, 40][..]), v.get(0..2));
322 /// assert_eq!(None, v.get(3));
323 /// assert_eq!(None, v.get(0..4));
325 #[stable(feature = "rust1", since = "1.0.0")]
327 pub fn get<I>(&self, index: I) -> Option<&I::Output>
328 where I: SliceIndex<Self>
333 /// Returns a mutable reference to an element or subslice depending on the
334 /// type of index (see [`get`]) or `None` if the index is out of bounds.
336 /// [`get`]: #method.get
341 /// let x = &mut [0, 1, 2];
343 /// if let Some(elem) = x.get_mut(1) {
346 /// assert_eq!(x, &[0, 42, 2]);
348 #[stable(feature = "rust1", since = "1.0.0")]
350 pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output>
351 where I: SliceIndex<Self>
356 /// Returns a reference to an element or subslice, without doing bounds
359 /// This is generally not recommended, use with caution! For a safe
360 /// alternative see [`get`].
362 /// [`get`]: #method.get
367 /// let x = &[1, 2, 4];
370 /// assert_eq!(x.get_unchecked(1), &2);
373 #[stable(feature = "rust1", since = "1.0.0")]
375 pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output
376 where I: SliceIndex<Self>
378 index.get_unchecked(self)
381 /// Returns a mutable reference to an element or subslice, without doing
384 /// This is generally not recommended, use with caution! For a safe
385 /// alternative see [`get_mut`].
387 /// [`get_mut`]: #method.get_mut
392 /// let x = &mut [1, 2, 4];
395 /// let elem = x.get_unchecked_mut(1);
398 /// assert_eq!(x, &[1, 13, 4]);
400 #[stable(feature = "rust1", since = "1.0.0")]
402 pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
403 where I: SliceIndex<Self>
405 index.get_unchecked_mut(self)
408 /// Returns a raw pointer to the slice's buffer.
410 /// The caller must ensure that the slice outlives the pointer this
411 /// function returns, or else it will end up pointing to garbage.
413 /// Modifying the container referenced by this slice may cause its buffer
414 /// to be reallocated, which would also make any pointers to it invalid.
419 /// let x = &[1, 2, 4];
420 /// let x_ptr = x.as_ptr();
423 /// for i in 0..x.len() {
424 /// assert_eq!(x.get_unchecked(i), &*x_ptr.offset(i as isize));
428 #[stable(feature = "rust1", since = "1.0.0")]
430 #[rustc_const_unstable(feature = "const_slice_as_ptr")]
431 pub const fn as_ptr(&self) -> *const T {
432 self as *const [T] as *const T
435 /// Returns an unsafe mutable pointer to the slice's buffer.
437 /// The caller must ensure that the slice outlives the pointer this
438 /// function returns, or else it will end up pointing to garbage.
440 /// Modifying the container referenced by this slice may cause its buffer
441 /// to be reallocated, which would also make any pointers to it invalid.
446 /// let x = &mut [1, 2, 4];
447 /// let x_ptr = x.as_mut_ptr();
450 /// for i in 0..x.len() {
451 /// *x_ptr.offset(i as isize) += 2;
454 /// assert_eq!(x, &[3, 4, 6]);
456 #[stable(feature = "rust1", since = "1.0.0")]
458 pub fn as_mut_ptr(&mut self) -> *mut T {
459 self as *mut [T] as *mut T
462 /// Swaps two elements in the slice.
466 /// * a - The index of the first element
467 /// * b - The index of the second element
471 /// Panics if `a` or `b` are out of bounds.
476 /// let mut v = ["a", "b", "c", "d"];
478 /// assert!(v == ["a", "d", "c", "b"]);
480 #[stable(feature = "rust1", since = "1.0.0")]
482 pub fn swap(&mut self, a: usize, b: usize) {
484 // Can't take two mutable loans from one vector, so instead just cast
485 // them to their raw pointers to do the swap
486 let pa: *mut T = &mut self[a];
487 let pb: *mut T = &mut self[b];
492 /// Reverses the order of elements in the slice, in place.
497 /// let mut v = [1, 2, 3];
499 /// assert!(v == [3, 2, 1]);
501 #[stable(feature = "rust1", since = "1.0.0")]
503 pub fn reverse(&mut self) {
504 let mut i: usize = 0;
507 // For very small types, all the individual reads in the normal
508 // path perform poorly. We can do better, given efficient unaligned
509 // load/store, by loading a larger chunk and reversing a register.
511 // Ideally LLVM would do this for us, as it knows better than we do
512 // whether unaligned reads are efficient (since that changes between
513 // different ARM versions, for example) and what the best chunk size
514 // would be. Unfortunately, as of LLVM 4.0 (2017-05) it only unrolls
515 // the loop, so we need to do this ourselves. (Hypothesis: reverse
516 // is troublesome because the sides can be aligned differently --
517 // will be, when the length is odd -- so there's no way of emitting
518 // pre- and postludes to use fully-aligned SIMD in the middle.)
521 cfg!(any(target_arch = "x86", target_arch = "x86_64"));
523 if fast_unaligned && mem::size_of::<T>() == 1 {
524 // Use the llvm.bswap intrinsic to reverse u8s in a usize
525 let chunk = mem::size_of::<usize>();
526 while i + chunk - 1 < ln / 2 {
528 let pa: *mut T = self.get_unchecked_mut(i);
529 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
530 let va = ptr::read_unaligned(pa as *mut usize);
531 let vb = ptr::read_unaligned(pb as *mut usize);
532 ptr::write_unaligned(pa as *mut usize, vb.swap_bytes());
533 ptr::write_unaligned(pb as *mut usize, va.swap_bytes());
539 if fast_unaligned && mem::size_of::<T>() == 2 {
540 // Use rotate-by-16 to reverse u16s in a u32
541 let chunk = mem::size_of::<u32>() / 2;
542 while i + chunk - 1 < ln / 2 {
544 let pa: *mut T = self.get_unchecked_mut(i);
545 let pb: *mut T = self.get_unchecked_mut(ln - i - chunk);
546 let va = ptr::read_unaligned(pa as *mut u32);
547 let vb = ptr::read_unaligned(pb as *mut u32);
548 ptr::write_unaligned(pa as *mut u32, vb.rotate_left(16));
549 ptr::write_unaligned(pb as *mut u32, va.rotate_left(16));
556 // Unsafe swap to avoid the bounds check in safe swap.
558 let pa: *mut T = self.get_unchecked_mut(i);
559 let pb: *mut T = self.get_unchecked_mut(ln - i - 1);
566 /// Returns an iterator over the slice.
571 /// let x = &[1, 2, 4];
572 /// let mut iterator = x.iter();
574 /// assert_eq!(iterator.next(), Some(&1));
575 /// assert_eq!(iterator.next(), Some(&2));
576 /// assert_eq!(iterator.next(), Some(&4));
577 /// assert_eq!(iterator.next(), None);
579 #[stable(feature = "rust1", since = "1.0.0")]
581 pub fn iter(&self) -> Iter<T> {
583 let p = if mem::size_of::<T>() == 0 {
586 let p = self.as_ptr();
587 assume(!p.is_null());
593 end: slice_offset!(p, self.len() as isize),
594 _marker: marker::PhantomData
599 /// Returns an iterator that allows modifying each value.
604 /// let x = &mut [1, 2, 4];
605 /// for elem in x.iter_mut() {
608 /// assert_eq!(x, &[3, 4, 6]);
610 #[stable(feature = "rust1", since = "1.0.0")]
612 pub fn iter_mut(&mut self) -> IterMut<T> {
614 let p = if mem::size_of::<T>() == 0 {
617 let p = self.as_mut_ptr();
618 assume(!p.is_null());
624 end: slice_offset!(p, self.len() as isize),
625 _marker: marker::PhantomData
630 /// Returns an iterator over all contiguous windows of length
631 /// `size`. The windows overlap. If the slice is shorter than
632 /// `size`, the iterator returns no values.
636 /// Panics if `size` is 0.
641 /// let slice = ['r', 'u', 's', 't'];
642 /// let mut iter = slice.windows(2);
643 /// assert_eq!(iter.next().unwrap(), &['r', 'u']);
644 /// assert_eq!(iter.next().unwrap(), &['u', 's']);
645 /// assert_eq!(iter.next().unwrap(), &['s', 't']);
646 /// assert!(iter.next().is_none());
649 /// If the slice is shorter than `size`:
652 /// let slice = ['f', 'o', 'o'];
653 /// let mut iter = slice.windows(4);
654 /// assert!(iter.next().is_none());
656 #[stable(feature = "rust1", since = "1.0.0")]
658 pub fn windows(&self, size: usize) -> Windows<T> {
660 Windows { v: self, size: size }
663 /// Returns an iterator over `chunk_size` elements of the slice at a
664 /// time. The chunks are slices and do not overlap. If `chunk_size` does
665 /// not divide the length of the slice, then the last chunk will
666 /// not have length `chunk_size`.
668 /// See [`exact_chunks`] for a variant of this iterator that returns chunks
669 /// of always exactly `chunk_size` elements.
673 /// Panics if `chunk_size` is 0.
678 /// let slice = ['l', 'o', 'r', 'e', 'm'];
679 /// let mut iter = slice.chunks(2);
680 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
681 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
682 /// assert_eq!(iter.next().unwrap(), &['m']);
683 /// assert!(iter.next().is_none());
686 /// [`exact_chunks`]: #method.exact_chunks
687 #[stable(feature = "rust1", since = "1.0.0")]
689 pub fn chunks(&self, chunk_size: usize) -> Chunks<T> {
690 assert!(chunk_size != 0);
691 Chunks { v: self, chunk_size: chunk_size }
694 /// Returns an iterator over `chunk_size` elements of the slice at a
695 /// time. The chunks are slices and do not overlap. If `chunk_size` does
696 /// not divide the length of the slice, then the last up to `chunk_size-1`
697 /// elements will be omitted.
699 /// Due to each chunk having exactly `chunk_size` elements, the compiler
700 /// can often optimize the resulting code better than in the case of
705 /// Panics if `chunk_size` is 0.
710 /// #![feature(exact_chunks)]
712 /// let slice = ['l', 'o', 'r', 'e', 'm'];
713 /// let mut iter = slice.exact_chunks(2);
714 /// assert_eq!(iter.next().unwrap(), &['l', 'o']);
715 /// assert_eq!(iter.next().unwrap(), &['r', 'e']);
716 /// assert!(iter.next().is_none());
719 /// [`chunks`]: #method.chunks
720 #[unstable(feature = "exact_chunks", issue = "47115")]
722 pub fn exact_chunks(&self, chunk_size: usize) -> ExactChunks<T> {
723 assert!(chunk_size != 0);
724 let rem = self.len() % chunk_size;
725 let len = self.len() - rem;
726 ExactChunks { v: &self[..len], chunk_size: chunk_size}
729 /// Returns an iterator over `chunk_size` elements of the slice at a time.
730 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
731 /// not divide the length of the slice, then the last chunk will not
732 /// have length `chunk_size`.
734 /// See [`exact_chunks_mut`] for a variant of this iterator that returns chunks
735 /// of always exactly `chunk_size` elements.
739 /// Panics if `chunk_size` is 0.
744 /// let v = &mut [0, 0, 0, 0, 0];
745 /// let mut count = 1;
747 /// for chunk in v.chunks_mut(2) {
748 /// for elem in chunk.iter_mut() {
753 /// assert_eq!(v, &[1, 1, 2, 2, 3]);
756 /// [`exact_chunks_mut`]: #method.exact_chunks_mut
757 #[stable(feature = "rust1", since = "1.0.0")]
759 pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T> {
760 assert!(chunk_size != 0);
761 ChunksMut { v: self, chunk_size: chunk_size }
764 /// Returns an iterator over `chunk_size` elements of the slice at a time.
765 /// The chunks are mutable slices, and do not overlap. If `chunk_size` does
766 /// not divide the length of the slice, then the last up to `chunk_size-1`
767 /// elements will be omitted.
770 /// Due to each chunk having exactly `chunk_size` elements, the compiler
771 /// can often optimize the resulting code better than in the case of
776 /// Panics if `chunk_size` is 0.
781 /// #![feature(exact_chunks)]
783 /// let v = &mut [0, 0, 0, 0, 0];
784 /// let mut count = 1;
786 /// for chunk in v.exact_chunks_mut(2) {
787 /// for elem in chunk.iter_mut() {
792 /// assert_eq!(v, &[1, 1, 2, 2, 0]);
795 /// [`chunks_mut`]: #method.chunks_mut
796 #[unstable(feature = "exact_chunks", issue = "47115")]
798 pub fn exact_chunks_mut(&mut self, chunk_size: usize) -> ExactChunksMut<T> {
799 assert!(chunk_size != 0);
800 let rem = self.len() % chunk_size;
801 let len = self.len() - rem;
802 ExactChunksMut { v: &mut self[..len], chunk_size: chunk_size}
805 /// Divides one slice into two at an index.
807 /// The first will contain all indices from `[0, mid)` (excluding
808 /// the index `mid` itself) and the second will contain all
809 /// indices from `[mid, len)` (excluding the index `len` itself).
813 /// Panics if `mid > len`.
818 /// let v = [1, 2, 3, 4, 5, 6];
821 /// let (left, right) = v.split_at(0);
822 /// assert!(left == []);
823 /// assert!(right == [1, 2, 3, 4, 5, 6]);
827 /// let (left, right) = v.split_at(2);
828 /// assert!(left == [1, 2]);
829 /// assert!(right == [3, 4, 5, 6]);
833 /// let (left, right) = v.split_at(6);
834 /// assert!(left == [1, 2, 3, 4, 5, 6]);
835 /// assert!(right == []);
838 #[stable(feature = "rust1", since = "1.0.0")]
840 pub fn split_at(&self, mid: usize) -> (&[T], &[T]) {
841 (&self[..mid], &self[mid..])
844 /// Divides one mutable slice into two at an index.
846 /// The first will contain all indices from `[0, mid)` (excluding
847 /// the index `mid` itself) and the second will contain all
848 /// indices from `[mid, len)` (excluding the index `len` itself).
852 /// Panics if `mid > len`.
857 /// let mut v = [1, 0, 3, 0, 5, 6];
858 /// // scoped to restrict the lifetime of the borrows
860 /// let (left, right) = v.split_at_mut(2);
861 /// assert!(left == [1, 0]);
862 /// assert!(right == [3, 0, 5, 6]);
866 /// assert!(v == [1, 2, 3, 4, 5, 6]);
868 #[stable(feature = "rust1", since = "1.0.0")]
870 pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
871 let len = self.len();
872 let ptr = self.as_mut_ptr();
877 (from_raw_parts_mut(ptr, mid),
878 from_raw_parts_mut(ptr.offset(mid as isize), len - mid))
882 /// Returns an iterator over subslices separated by elements that match
883 /// `pred`. The matched element is not contained in the subslices.
888 /// let slice = [10, 40, 33, 20];
889 /// let mut iter = slice.split(|num| num % 3 == 0);
891 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
892 /// assert_eq!(iter.next().unwrap(), &[20]);
893 /// assert!(iter.next().is_none());
896 /// If the first element is matched, an empty slice will be the first item
897 /// returned by the iterator. Similarly, if the last element in the slice
898 /// is matched, an empty slice will be the last item returned by the
902 /// let slice = [10, 40, 33];
903 /// let mut iter = slice.split(|num| num % 3 == 0);
905 /// assert_eq!(iter.next().unwrap(), &[10, 40]);
906 /// assert_eq!(iter.next().unwrap(), &[]);
907 /// assert!(iter.next().is_none());
910 /// If two matched elements are directly adjacent, an empty slice will be
911 /// present between them:
914 /// let slice = [10, 6, 33, 20];
915 /// let mut iter = slice.split(|num| num % 3 == 0);
917 /// assert_eq!(iter.next().unwrap(), &[10]);
918 /// assert_eq!(iter.next().unwrap(), &[]);
919 /// assert_eq!(iter.next().unwrap(), &[20]);
920 /// assert!(iter.next().is_none());
922 #[stable(feature = "rust1", since = "1.0.0")]
924 pub fn split<F>(&self, pred: F) -> Split<T, F>
925 where F: FnMut(&T) -> bool
934 /// Returns an iterator over mutable subslices separated by elements that
935 /// match `pred`. The matched element is not contained in the subslices.
940 /// let mut v = [10, 40, 30, 20, 60, 50];
942 /// for group in v.split_mut(|num| *num % 3 == 0) {
945 /// assert_eq!(v, [1, 40, 30, 1, 60, 1]);
947 #[stable(feature = "rust1", since = "1.0.0")]
949 pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<T, F>
950 where F: FnMut(&T) -> bool
952 SplitMut { v: self, pred: pred, finished: false }
955 /// Returns an iterator over subslices separated by elements that match
956 /// `pred`, starting at the end of the slice and working backwards.
957 /// The matched element is not contained in the subslices.
962 /// let slice = [11, 22, 33, 0, 44, 55];
963 /// let mut iter = slice.rsplit(|num| *num == 0);
965 /// assert_eq!(iter.next().unwrap(), &[44, 55]);
966 /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
967 /// assert_eq!(iter.next(), None);
970 /// As with `split()`, if the first or last element is matched, an empty
971 /// slice will be the first (or last) item returned by the iterator.
974 /// let v = &[0, 1, 1, 2, 3, 5, 8];
975 /// let mut it = v.rsplit(|n| *n % 2 == 0);
976 /// assert_eq!(it.next().unwrap(), &[]);
977 /// assert_eq!(it.next().unwrap(), &[3, 5]);
978 /// assert_eq!(it.next().unwrap(), &[1, 1]);
979 /// assert_eq!(it.next().unwrap(), &[]);
980 /// assert_eq!(it.next(), None);
982 #[stable(feature = "slice_rsplit", since = "1.27.0")]
984 pub fn rsplit<F>(&self, pred: F) -> RSplit<T, F>
985 where F: FnMut(&T) -> bool
987 RSplit { inner: self.split(pred) }
990 /// Returns an iterator over mutable subslices separated by elements that
991 /// match `pred`, starting at the end of the slice and working
992 /// backwards. The matched element is not contained in the subslices.
997 /// let mut v = [100, 400, 300, 200, 600, 500];
999 /// let mut count = 0;
1000 /// for group in v.rsplit_mut(|num| *num % 3 == 0) {
1002 /// group[0] = count;
1004 /// assert_eq!(v, [3, 400, 300, 2, 600, 1]);
1007 #[stable(feature = "slice_rsplit", since = "1.27.0")]
1009 pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<T, F>
1010 where F: FnMut(&T) -> bool
1012 RSplitMut { inner: self.split_mut(pred) }
1015 /// Returns an iterator over subslices separated by elements that match
1016 /// `pred`, limited to returning at most `n` items. The matched element is
1017 /// not contained in the subslices.
1019 /// The last element returned, if any, will contain the remainder of the
1024 /// Print the slice split once by numbers divisible by 3 (i.e. `[10, 40]`,
1025 /// `[20, 60, 50]`):
1028 /// let v = [10, 40, 30, 20, 60, 50];
1030 /// for group in v.splitn(2, |num| *num % 3 == 0) {
1031 /// println!("{:?}", group);
1034 #[stable(feature = "rust1", since = "1.0.0")]
1036 pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<T, F>
1037 where F: FnMut(&T) -> bool
1040 inner: GenericSplitN {
1041 iter: self.split(pred),
1047 /// Returns an iterator over subslices separated by elements that match
1048 /// `pred`, limited to returning at most `n` items. The matched element is
1049 /// not contained in the subslices.
1051 /// The last element returned, if any, will contain the remainder of the
1057 /// let mut v = [10, 40, 30, 20, 60, 50];
1059 /// for group in v.splitn_mut(2, |num| *num % 3 == 0) {
1062 /// assert_eq!(v, [1, 40, 30, 1, 60, 50]);
1064 #[stable(feature = "rust1", since = "1.0.0")]
1066 pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<T, F>
1067 where F: FnMut(&T) -> bool
1070 inner: GenericSplitN {
1071 iter: self.split_mut(pred),
1077 /// Returns an iterator over subslices separated by elements that match
1078 /// `pred` limited to returning at most `n` items. This starts at the end of
1079 /// the slice and works backwards. The matched element is not contained in
1082 /// The last element returned, if any, will contain the remainder of the
1087 /// Print the slice split once, starting from the end, by numbers divisible
1088 /// by 3 (i.e. `[50]`, `[10, 40, 30, 20]`):
1091 /// let v = [10, 40, 30, 20, 60, 50];
1093 /// for group in v.rsplitn(2, |num| *num % 3 == 0) {
1094 /// println!("{:?}", group);
1097 #[stable(feature = "rust1", since = "1.0.0")]
1099 pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<T, F>
1100 where F: FnMut(&T) -> bool
1103 inner: GenericSplitN {
1104 iter: self.rsplit(pred),
1110 /// Returns an iterator over subslices separated by elements that match
1111 /// `pred` limited to returning at most `n` items. This starts at the end of
1112 /// the slice and works backwards. The matched element is not contained in
1115 /// The last element returned, if any, will contain the remainder of the
1121 /// let mut s = [10, 40, 30, 20, 60, 50];
1123 /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) {
1126 /// assert_eq!(s, [1, 40, 30, 20, 60, 1]);
1128 #[stable(feature = "rust1", since = "1.0.0")]
1130 pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<T, F>
1131 where F: FnMut(&T) -> bool
1134 inner: GenericSplitN {
1135 iter: self.rsplit_mut(pred),
1141 /// Returns `true` if the slice contains an element with the given value.
1146 /// let v = [10, 40, 30];
1147 /// assert!(v.contains(&30));
1148 /// assert!(!v.contains(&50));
1150 #[stable(feature = "rust1", since = "1.0.0")]
1151 pub fn contains(&self, x: &T) -> bool
1154 x.slice_contains(self)
1157 /// Returns `true` if `needle` is a prefix of the slice.
1162 /// let v = [10, 40, 30];
1163 /// assert!(v.starts_with(&[10]));
1164 /// assert!(v.starts_with(&[10, 40]));
1165 /// assert!(!v.starts_with(&[50]));
1166 /// assert!(!v.starts_with(&[10, 50]));
1169 /// Always returns `true` if `needle` is an empty slice:
1172 /// let v = &[10, 40, 30];
1173 /// assert!(v.starts_with(&[]));
1174 /// let v: &[u8] = &[];
1175 /// assert!(v.starts_with(&[]));
1177 #[stable(feature = "rust1", since = "1.0.0")]
1178 pub fn starts_with(&self, needle: &[T]) -> bool
1181 let n = needle.len();
1182 self.len() >= n && needle == &self[..n]
1185 /// Returns `true` if `needle` is a suffix of the slice.
1190 /// let v = [10, 40, 30];
1191 /// assert!(v.ends_with(&[30]));
1192 /// assert!(v.ends_with(&[40, 30]));
1193 /// assert!(!v.ends_with(&[50]));
1194 /// assert!(!v.ends_with(&[50, 30]));
1197 /// Always returns `true` if `needle` is an empty slice:
1200 /// let v = &[10, 40, 30];
1201 /// assert!(v.ends_with(&[]));
1202 /// let v: &[u8] = &[];
1203 /// assert!(v.ends_with(&[]));
1205 #[stable(feature = "rust1", since = "1.0.0")]
1206 pub fn ends_with(&self, needle: &[T]) -> bool
1209 let (m, n) = (self.len(), needle.len());
1210 m >= n && needle == &self[m-n..]
1213 /// Binary searches this sorted slice for a given element.
1215 /// If the value is found then `Ok` is returned, containing the
1216 /// index of the matching element; if the value is not found then
1217 /// `Err` is returned, containing the index where a matching
1218 /// element could be inserted while maintaining sorted order.
1222 /// Looks up a series of four elements. The first is found, with a
1223 /// uniquely determined position; the second and third are not
1224 /// found; the fourth could match any position in `[1, 4]`.
1227 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1229 /// assert_eq!(s.binary_search(&13), Ok(9));
1230 /// assert_eq!(s.binary_search(&4), Err(7));
1231 /// assert_eq!(s.binary_search(&100), Err(13));
1232 /// let r = s.binary_search(&1);
1233 /// assert!(match r { Ok(1...4) => true, _ => false, });
1235 #[stable(feature = "rust1", since = "1.0.0")]
1236 pub fn binary_search(&self, x: &T) -> Result<usize, usize>
1239 self.binary_search_by(|p| p.cmp(x))
1242 /// Binary searches this sorted slice with a comparator function.
1244 /// The comparator function should implement an order consistent
1245 /// with the sort order of the underlying slice, returning an
1246 /// order code that indicates whether its argument is `Less`,
1247 /// `Equal` or `Greater` the desired target.
1249 /// If a matching value is found then returns `Ok`, containing
1250 /// the index for the matched element; if no match is found then
1251 /// `Err` is returned, containing the index where a matching
1252 /// element could be inserted while maintaining sorted order.
1256 /// Looks up a series of four elements. The first is found, with a
1257 /// uniquely determined position; the second and third are not
1258 /// found; the fourth could match any position in `[1, 4]`.
1261 /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
1264 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
1266 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
1268 /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
1270 /// let r = s.binary_search_by(|probe| probe.cmp(&seek));
1271 /// assert!(match r { Ok(1...4) => true, _ => false, });
1273 #[stable(feature = "rust1", since = "1.0.0")]
1275 pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
1276 where F: FnMut(&'a T) -> Ordering
1279 let mut size = s.len();
1283 let mut base = 0usize;
1285 let half = size / 2;
1286 let mid = base + half;
1287 // mid is always in [0, size), that means mid is >= 0 and < size.
1288 // mid >= 0: by definition
1289 // mid < size: mid = size / 2 + size / 4 + size / 8 ...
1290 let cmp = f(unsafe { s.get_unchecked(mid) });
1291 base = if cmp == Greater { base } else { mid };
1294 // base is always in [0, size) because base <= mid.
1295 let cmp = f(unsafe { s.get_unchecked(base) });
1296 if cmp == Equal { Ok(base) } else { Err(base + (cmp == Less) as usize) }
1300 /// Binary searches this sorted slice with a key extraction function.
1302 /// Assumes that the slice is sorted by the key, for instance with
1303 /// [`sort_by_key`] using the same key extraction function.
1305 /// If a matching value is found then returns `Ok`, containing the
1306 /// index for the matched element; if no match is found then `Err`
1307 /// is returned, containing the index where a matching element could
1308 /// be inserted while maintaining sorted order.
1310 /// [`sort_by_key`]: #method.sort_by_key
1314 /// Looks up a series of four elements in a slice of pairs sorted by
1315 /// their second elements. The first is found, with a uniquely
1316 /// determined position; the second and third are not found; the
1317 /// fourth could match any position in `[1, 4]`.
1320 /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1),
1321 /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
1322 /// (1, 21), (2, 34), (4, 55)];
1324 /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9));
1325 /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7));
1326 /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13));
1327 /// let r = s.binary_search_by_key(&1, |&(a,b)| b);
1328 /// assert!(match r { Ok(1...4) => true, _ => false, });
1330 #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
1332 pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
1333 where F: FnMut(&'a T) -> B,
1336 self.binary_search_by(|k| f(k).cmp(b))
1339 /// Sorts the slice, but may not preserve the order of equal elements.
1341 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1342 /// and `O(n log n)` worst-case.
1344 /// # Current implementation
1346 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1347 /// which combines the fast average case of randomized quicksort with the fast worst case of
1348 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1349 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1350 /// deterministic behavior.
1352 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1353 /// slice consists of several concatenated sorted sequences.
1358 /// let mut v = [-5, 4, 1, -3, 2];
1360 /// v.sort_unstable();
1361 /// assert!(v == [-5, -3, 1, 2, 4]);
1364 /// [pdqsort]: https://github.com/orlp/pdqsort
1365 #[stable(feature = "sort_unstable", since = "1.20.0")]
1367 pub fn sort_unstable(&mut self)
1370 sort::quicksort(self, |a, b| a.lt(b));
1373 /// Sorts the slice with a comparator 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(n log n)` worst-case.
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.
1387 /// It is typically faster than stable sorting, except in a few special cases, e.g. when the
1388 /// slice consists of several concatenated sorted sequences.
1393 /// let mut v = [5, 4, 1, 3, 2];
1394 /// v.sort_unstable_by(|a, b| a.cmp(b));
1395 /// assert!(v == [1, 2, 3, 4, 5]);
1397 /// // reverse sorting
1398 /// v.sort_unstable_by(|a, b| b.cmp(a));
1399 /// assert!(v == [5, 4, 3, 2, 1]);
1402 /// [pdqsort]: https://github.com/orlp/pdqsort
1403 #[stable(feature = "sort_unstable", since = "1.20.0")]
1405 pub fn sort_unstable_by<F>(&mut self, mut compare: F)
1406 where F: FnMut(&T, &T) -> Ordering
1408 sort::quicksort(self, |a, b| compare(a, b) == Ordering::Less);
1411 /// Sorts the slice with a key extraction function, but may not preserve the order of equal
1414 /// This sort is unstable (i.e. may reorder equal elements), in-place (i.e. does not allocate),
1415 /// and `O(m n log(m n))` worst-case, where the key function is `O(m)`.
1417 /// # Current implementation
1419 /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,
1420 /// which combines the fast average case of randomized quicksort with the fast worst case of
1421 /// heapsort, while achieving linear time on slices with certain patterns. It uses some
1422 /// randomization to avoid degenerate cases, but with a fixed seed to always provide
1423 /// deterministic behavior.
1428 /// let mut v = [-5i32, 4, 1, -3, 2];
1430 /// v.sort_unstable_by_key(|k| k.abs());
1431 /// assert!(v == [1, 2, -3, 4, -5]);
1434 /// [pdqsort]: https://github.com/orlp/pdqsort
1435 #[stable(feature = "sort_unstable", since = "1.20.0")]
1437 pub fn sort_unstable_by_key<K, F>(&mut self, mut f: F)
1438 where F: FnMut(&T) -> K, K: Ord
1440 sort::quicksort(self, |a, b| f(a).lt(&f(b)));
1443 /// Rotates the slice in-place such that the first `mid` elements of the
1444 /// slice move to the end while the last `self.len() - mid` elements move to
1445 /// the front. After calling `rotate_left`, the element previously at index
1446 /// `mid` will become the first element in the slice.
1450 /// This function will panic if `mid` is greater than the length of the
1451 /// slice. Note that `mid == self.len()` does _not_ panic and is a no-op
1456 /// Takes linear (in `self.len()`) time.
1461 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1462 /// a.rotate_left(2);
1463 /// assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']);
1466 /// Rotating a subslice:
1469 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1470 /// a[1..5].rotate_left(1);
1471 /// assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']);
1473 #[stable(feature = "slice_rotate", since = "1.26.0")]
1474 pub fn rotate_left(&mut self, mid: usize) {
1475 assert!(mid <= self.len());
1476 let k = self.len() - mid;
1479 let p = self.as_mut_ptr();
1480 rotate::ptr_rotate(mid, p.offset(mid as isize), k);
1484 /// Rotates the slice in-place such that the first `self.len() - k`
1485 /// elements of the slice move to the end while the last `k` elements move
1486 /// to the front. After calling `rotate_right`, the element previously at
1487 /// index `self.len() - k` will become the first element in the slice.
1491 /// This function will panic if `k` is greater than the length of the
1492 /// slice. Note that `k == self.len()` does _not_ panic and is a no-op
1497 /// Takes linear (in `self.len()`) time.
1502 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1503 /// a.rotate_right(2);
1504 /// assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']);
1507 /// Rotate a subslice:
1510 /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f'];
1511 /// a[1..5].rotate_right(1);
1512 /// assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']);
1514 #[stable(feature = "slice_rotate", since = "1.26.0")]
1515 pub fn rotate_right(&mut self, k: usize) {
1516 assert!(k <= self.len());
1517 let mid = self.len() - k;
1520 let p = self.as_mut_ptr();
1521 rotate::ptr_rotate(mid, p.offset(mid as isize), k);
1525 /// Copies the elements from `src` into `self`.
1527 /// The length of `src` must be the same as `self`.
1529 /// If `src` implements `Copy`, it can be more performant to use
1530 /// [`copy_from_slice`].
1534 /// This function will panic if the two slices have different lengths.
1538 /// Cloning two elements from a slice into another:
1541 /// let src = [1, 2, 3, 4];
1542 /// let mut dst = [0, 0];
1544 /// dst.clone_from_slice(&src[2..]);
1546 /// assert_eq!(src, [1, 2, 3, 4]);
1547 /// assert_eq!(dst, [3, 4]);
1550 /// Rust enforces that there can only be one mutable reference with no
1551 /// immutable references to a particular piece of data in a particular
1552 /// scope. Because of this, attempting to use `clone_from_slice` on a
1553 /// single slice will result in a compile failure:
1556 /// let mut slice = [1, 2, 3, 4, 5];
1558 /// slice[..2].clone_from_slice(&slice[3..]); // compile fail!
1561 /// To work around this, we can use [`split_at_mut`] to create two distinct
1562 /// sub-slices from a slice:
1565 /// let mut slice = [1, 2, 3, 4, 5];
1568 /// let (left, right) = slice.split_at_mut(2);
1569 /// left.clone_from_slice(&right[1..]);
1572 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
1575 /// [`copy_from_slice`]: #method.copy_from_slice
1576 /// [`split_at_mut`]: #method.split_at_mut
1577 #[stable(feature = "clone_from_slice", since = "1.7.0")]
1578 pub fn clone_from_slice(&mut self, src: &[T]) where T: Clone {
1579 assert!(self.len() == src.len(),
1580 "destination and source slices have different lengths");
1581 // NOTE: We need to explicitly slice them to the same length
1582 // for bounds checking to be elided, and the optimizer will
1583 // generate memcpy for simple cases (for example T = u8).
1584 let len = self.len();
1585 let src = &src[..len];
1587 self[i].clone_from(&src[i]);
1592 /// Copies all elements from `src` into `self`, using a memcpy.
1594 /// The length of `src` must be the same as `self`.
1596 /// If `src` does not implement `Copy`, use [`clone_from_slice`].
1600 /// This function will panic if the two slices have different lengths.
1604 /// Copying two elements from a slice into another:
1607 /// let src = [1, 2, 3, 4];
1608 /// let mut dst = [0, 0];
1610 /// dst.copy_from_slice(&src[2..]);
1612 /// assert_eq!(src, [1, 2, 3, 4]);
1613 /// assert_eq!(dst, [3, 4]);
1616 /// Rust enforces that there can only be one mutable reference with no
1617 /// immutable references to a particular piece of data in a particular
1618 /// scope. Because of this, attempting to use `copy_from_slice` on a
1619 /// single slice will result in a compile failure:
1622 /// let mut slice = [1, 2, 3, 4, 5];
1624 /// slice[..2].copy_from_slice(&slice[3..]); // compile fail!
1627 /// To work around this, we can use [`split_at_mut`] to create two distinct
1628 /// sub-slices from a slice:
1631 /// let mut slice = [1, 2, 3, 4, 5];
1634 /// let (left, right) = slice.split_at_mut(2);
1635 /// left.copy_from_slice(&right[1..]);
1638 /// assert_eq!(slice, [4, 5, 3, 4, 5]);
1641 /// [`clone_from_slice`]: #method.clone_from_slice
1642 /// [`split_at_mut`]: #method.split_at_mut
1643 #[stable(feature = "copy_from_slice", since = "1.9.0")]
1644 pub fn copy_from_slice(&mut self, src: &[T]) where T: Copy {
1645 assert!(self.len() == src.len(),
1646 "destination and source slices have different lengths");
1648 ptr::copy_nonoverlapping(
1649 src.as_ptr(), self.as_mut_ptr(), self.len());
1653 /// Swaps all elements in `self` with those in `other`.
1655 /// The length of `other` must be the same as `self`.
1659 /// This function will panic if the two slices have different lengths.
1663 /// Swapping two elements across slices:
1666 /// let mut slice1 = [0, 0];
1667 /// let mut slice2 = [1, 2, 3, 4];
1669 /// slice1.swap_with_slice(&mut slice2[2..]);
1671 /// assert_eq!(slice1, [3, 4]);
1672 /// assert_eq!(slice2, [1, 2, 0, 0]);
1675 /// Rust enforces that there can only be one mutable reference to a
1676 /// particular piece of data in a particular scope. Because of this,
1677 /// attempting to use `swap_with_slice` on a single slice will result in
1678 /// a compile failure:
1681 /// let mut slice = [1, 2, 3, 4, 5];
1682 /// slice[..2].swap_with_slice(&mut slice[3..]); // compile fail!
1685 /// To work around this, we can use [`split_at_mut`] to create two distinct
1686 /// mutable sub-slices from a slice:
1689 /// let mut slice = [1, 2, 3, 4, 5];
1692 /// let (left, right) = slice.split_at_mut(2);
1693 /// left.swap_with_slice(&mut right[1..]);
1696 /// assert_eq!(slice, [4, 5, 3, 1, 2]);
1699 /// [`split_at_mut`]: #method.split_at_mut
1700 #[stable(feature = "swap_with_slice", since = "1.27.0")]
1701 pub fn swap_with_slice(&mut self, other: &mut [T]) {
1702 assert!(self.len() == other.len(),
1703 "destination and source slices have different lengths");
1705 ptr::swap_nonoverlapping(
1706 self.as_mut_ptr(), other.as_mut_ptr(), self.len());
1710 /// Function to calculate lenghts of the middle and trailing slice for `align_to{,_mut}`.
1712 fn align_to_offsets<U>(&self) -> (usize, usize) {
1713 // What we gonna do about `rest` is figure out what multiple of `U`s we can put in a
1714 // lowest number of `T`s. And how many `T`s we need for each such "multiple".
1716 // Consider for example T=u8 U=u16. Then we can put 1 U in 2 Ts. Simple. Now, consider
1717 // for example a case where size_of::<T> = 16, size_of::<U> = 24. We can put 2 Us in
1718 // place of every 3 Ts in the `rest` slice. A bit more complicated.
1720 // Formula to calculate this is:
1722 // Us = lcm(size_of::<T>, size_of::<U>) / size_of::<U>
1723 // Ts = lcm(size_of::<T>, size_of::<U>) / size_of::<T>
1725 // Expanded and simplified:
1727 // Us = size_of::<T> / gcd(size_of::<T>, size_of::<U>)
1728 // Ts = size_of::<U> / gcd(size_of::<T>, size_of::<U>)
1730 // Luckily since all this is constant-evaluated... performance here matters not!
1732 fn gcd(a: usize, b: usize) -> usize {
1733 // iterative stein’s algorithm
1734 // We should still make this `const fn` (and revert to recursive algorithm if we do)
1735 // because relying on llvm to consteval all this is… well, it makes me
1736 let (ctz_a, mut ctz_b) = unsafe {
1737 if a == 0 { return b; }
1738 if b == 0 { return a; }
1739 (::intrinsics::cttz_nonzero(a), ::intrinsics::cttz_nonzero(b))
1741 let k = ctz_a.min(ctz_b);
1742 let mut a = a >> ctz_a;
1745 // remove all factors of 2 from b
1748 ::mem::swap(&mut a, &mut b);
1755 ctz_b = ::intrinsics::cttz_nonzero(b);
1760 let gcd: usize = gcd(::mem::size_of::<T>(), ::mem::size_of::<U>());
1761 let ts: usize = ::mem::size_of::<U>() / gcd;
1762 let us: usize = ::mem::size_of::<T>() / gcd;
1764 // Armed with this knowledge, we can find how many `U`s we can fit!
1765 let us_len = self.len() / ts * us;
1766 // And how many `T`s will be in the trailing slice!
1767 let ts_len = self.len() % ts;
1768 return (us_len, ts_len);
1771 /// Transmute the slice to a slice of another type, ensuring aligment of the types is
1774 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
1775 /// slice of a new type, and the suffix slice. The middle slice will have the greatest length
1776 /// possible for a given type and input slice.
1778 /// This method has no purpose when either input element `T` or output element `U` are
1779 /// zero-sized and will return the original slice without splitting anything.
1783 /// This method is essentially a `transmute` with respect to the elements in the returned
1784 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
1791 /// # #![feature(slice_align_to)]
1793 /// let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
1794 /// let (prefix, shorts, suffix) = bytes.align_to::<u16>();
1795 /// // less_efficient_algorithm_for_bytes(prefix);
1796 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
1797 /// // less_efficient_algorithm_for_bytes(suffix);
1800 #[unstable(feature = "slice_align_to", issue = "44488")]
1802 pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T]) {
1803 // Note that most of this function will be constant-evaluated,
1804 if ::mem::size_of::<U>() == 0 || ::mem::size_of::<T>() == 0 {
1805 // handle ZSTs specially, which is – don't handle them at all.
1806 return (self, &[], &[]);
1809 // First, find at what point do we split between the first and 2nd slice. Easy with
1810 // ptr.align_offset.
1811 let ptr = self.as_ptr();
1812 let offset = ::ptr::align_offset(ptr, ::mem::align_of::<U>());
1813 if offset > self.len() {
1814 return (self, &[], &[]);
1816 let (left, rest) = self.split_at(offset);
1817 let (us_len, ts_len) = rest.align_to_offsets::<U>();
1819 from_raw_parts(rest.as_ptr() as *const U, us_len),
1820 from_raw_parts(rest.as_ptr().offset((rest.len() - ts_len) as isize), ts_len))
1824 /// Transmute the slice to a slice of another type, ensuring aligment of the types is
1827 /// This method splits the slice into three distinct slices: prefix, correctly aligned middle
1828 /// slice of a new type, and the suffix slice. The middle slice will have the greatest length
1829 /// possible for a given type and input slice.
1831 /// This method has no purpose when either input element `T` or output element `U` are
1832 /// zero-sized and will return the original slice without splitting anything.
1836 /// This method is essentially a `transmute` with respect to the elements in the returned
1837 /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here.
1844 /// # #![feature(slice_align_to)]
1846 /// let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7];
1847 /// let (prefix, shorts, suffix) = bytes.align_to_mut::<u16>();
1848 /// // less_efficient_algorithm_for_bytes(prefix);
1849 /// // more_efficient_algorithm_for_aligned_shorts(shorts);
1850 /// // less_efficient_algorithm_for_bytes(suffix);
1853 #[unstable(feature = "slice_align_to", issue = "44488")]
1855 pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T]) {
1856 // Note that most of this function will be constant-evaluated,
1857 if ::mem::size_of::<U>() == 0 || ::mem::size_of::<T>() == 0 {
1858 // handle ZSTs specially, which is – don't handle them at all.
1859 return (self, &mut [], &mut []);
1862 // First, find at what point do we split between the first and 2nd slice. Easy with
1863 // ptr.align_offset.
1864 let ptr = self.as_ptr();
1865 let offset = ::ptr::align_offset(ptr, ::mem::align_of::<U>());
1866 if offset > self.len() {
1867 return (self, &mut [], &mut []);
1869 let (left, rest) = self.split_at_mut(offset);
1870 let (us_len, ts_len) = rest.align_to_offsets::<U>();
1871 let mut_ptr = rest.as_mut_ptr();
1873 from_raw_parts_mut(mut_ptr as *mut U, us_len),
1874 from_raw_parts_mut(mut_ptr.offset((rest.len() - ts_len) as isize), ts_len))
1879 #[lang = "slice_u8"]
1882 /// Checks if all bytes in this slice are within the ASCII range.
1883 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
1885 pub fn is_ascii(&self) -> bool {
1886 self.iter().all(|b| b.is_ascii())
1889 /// Checks that two slices are an ASCII case-insensitive match.
1891 /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
1892 /// but without allocating and copying temporaries.
1893 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
1895 pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool {
1896 self.len() == other.len() &&
1897 self.iter().zip(other).all(|(a, b)| {
1898 a.eq_ignore_ascii_case(b)
1902 /// Converts this slice to its ASCII upper case equivalent in-place.
1904 /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
1905 /// but non-ASCII letters are unchanged.
1907 /// To return a new uppercased value without modifying the existing one, use
1908 /// [`to_ascii_uppercase`].
1910 /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase
1911 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
1913 pub fn make_ascii_uppercase(&mut self) {
1915 byte.make_ascii_uppercase();
1919 /// Converts this slice to its ASCII lower case equivalent in-place.
1921 /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
1922 /// but non-ASCII letters are unchanged.
1924 /// To return a new lowercased value without modifying the existing one, use
1925 /// [`to_ascii_lowercase`].
1927 /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase
1928 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
1930 pub fn make_ascii_lowercase(&mut self) {
1932 byte.make_ascii_lowercase();
1938 #[stable(feature = "rust1", since = "1.0.0")]
1939 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
1940 impl<T, I> ops::Index<I> for [T]
1941 where I: SliceIndex<[T]>
1943 type Output = I::Output;
1946 fn index(&self, index: I) -> &I::Output {
1951 #[stable(feature = "rust1", since = "1.0.0")]
1952 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
1953 impl<T, I> ops::IndexMut<I> for [T]
1954 where I: SliceIndex<[T]>
1957 fn index_mut(&mut self, index: I) -> &mut I::Output {
1958 index.index_mut(self)
1964 fn slice_index_len_fail(index: usize, len: usize) -> ! {
1965 panic!("index {} out of range for slice of length {}", index, len);
1970 fn slice_index_order_fail(index: usize, end: usize) -> ! {
1971 panic!("slice index starts at {} but ends at {}", index, end);
1976 fn slice_index_overflow_fail() -> ! {
1977 panic!("attempted to index slice up to maximum usize");
1980 /// A helper trait used for indexing operations.
1981 #[unstable(feature = "slice_get_slice", issue = "35729")]
1982 #[rustc_on_unimplemented = "slice indices are of type `usize` or ranges of `usize`"]
1983 pub trait SliceIndex<T: ?Sized> {
1984 /// The output type returned by methods.
1985 type Output: ?Sized;
1987 /// Returns a shared reference to the output at this location, if in
1989 fn get(self, slice: &T) -> Option<&Self::Output>;
1991 /// Returns a mutable reference to the output at this location, if in
1993 fn get_mut(self, slice: &mut T) -> Option<&mut Self::Output>;
1995 /// Returns a shared reference to the output at this location, without
1996 /// performing any bounds checking.
1997 unsafe fn get_unchecked(self, slice: &T) -> &Self::Output;
1999 /// Returns a mutable reference to the output at this location, without
2000 /// performing any bounds checking.
2001 unsafe fn get_unchecked_mut(self, slice: &mut T) -> &mut Self::Output;
2003 /// Returns a shared reference to the output at this location, panicking
2004 /// if out of bounds.
2005 fn index(self, slice: &T) -> &Self::Output;
2007 /// Returns a mutable reference to the output at this location, panicking
2008 /// if out of bounds.
2009 fn index_mut(self, slice: &mut T) -> &mut Self::Output;
2012 #[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
2013 impl<T> SliceIndex<[T]> for usize {
2017 fn get(self, slice: &[T]) -> Option<&T> {
2018 if self < slice.len() {
2020 Some(self.get_unchecked(slice))
2028 fn get_mut(self, slice: &mut [T]) -> Option<&mut T> {
2029 if self < slice.len() {
2031 Some(self.get_unchecked_mut(slice))
2039 unsafe fn get_unchecked(self, slice: &[T]) -> &T {
2040 &*slice.as_ptr().offset(self as isize)
2044 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut T {
2045 &mut *slice.as_mut_ptr().offset(self as isize)
2049 fn index(self, slice: &[T]) -> &T {
2050 // NB: use intrinsic indexing
2055 fn index_mut(self, slice: &mut [T]) -> &mut T {
2056 // NB: use intrinsic indexing
2061 #[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
2062 impl<T> SliceIndex<[T]> for ops::Range<usize> {
2066 fn get(self, slice: &[T]) -> Option<&[T]> {
2067 if self.start > self.end || self.end > slice.len() {
2071 Some(self.get_unchecked(slice))
2077 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2078 if self.start > self.end || self.end > slice.len() {
2082 Some(self.get_unchecked_mut(slice))
2088 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2089 from_raw_parts(slice.as_ptr().offset(self.start as isize), self.end - self.start)
2093 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2094 from_raw_parts_mut(slice.as_mut_ptr().offset(self.start as isize), self.end - self.start)
2098 fn index(self, slice: &[T]) -> &[T] {
2099 if self.start > self.end {
2100 slice_index_order_fail(self.start, self.end);
2101 } else if self.end > slice.len() {
2102 slice_index_len_fail(self.end, slice.len());
2105 self.get_unchecked(slice)
2110 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2111 if self.start > self.end {
2112 slice_index_order_fail(self.start, self.end);
2113 } else if self.end > slice.len() {
2114 slice_index_len_fail(self.end, slice.len());
2117 self.get_unchecked_mut(slice)
2122 #[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
2123 impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {
2127 fn get(self, slice: &[T]) -> Option<&[T]> {
2128 (0..self.end).get(slice)
2132 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2133 (0..self.end).get_mut(slice)
2137 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2138 (0..self.end).get_unchecked(slice)
2142 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2143 (0..self.end).get_unchecked_mut(slice)
2147 fn index(self, slice: &[T]) -> &[T] {
2148 (0..self.end).index(slice)
2152 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2153 (0..self.end).index_mut(slice)
2157 #[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
2158 impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {
2162 fn get(self, slice: &[T]) -> Option<&[T]> {
2163 (self.start..slice.len()).get(slice)
2167 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2168 (self.start..slice.len()).get_mut(slice)
2172 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2173 (self.start..slice.len()).get_unchecked(slice)
2177 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2178 (self.start..slice.len()).get_unchecked_mut(slice)
2182 fn index(self, slice: &[T]) -> &[T] {
2183 (self.start..slice.len()).index(slice)
2187 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2188 (self.start..slice.len()).index_mut(slice)
2192 #[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
2193 impl<T> SliceIndex<[T]> for ops::RangeFull {
2197 fn get(self, slice: &[T]) -> Option<&[T]> {
2202 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2207 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2212 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2217 fn index(self, slice: &[T]) -> &[T] {
2222 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2228 #[stable(feature = "inclusive_range", since = "1.26.0")]
2229 impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> {
2233 fn get(self, slice: &[T]) -> Option<&[T]> {
2234 if self.end == usize::max_value() { None }
2235 else { (self.start..self.end + 1).get(slice) }
2239 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2240 if self.end == usize::max_value() { None }
2241 else { (self.start..self.end + 1).get_mut(slice) }
2245 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2246 (self.start..self.end + 1).get_unchecked(slice)
2250 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2251 (self.start..self.end + 1).get_unchecked_mut(slice)
2255 fn index(self, slice: &[T]) -> &[T] {
2256 if self.end == usize::max_value() { slice_index_overflow_fail(); }
2257 (self.start..self.end + 1).index(slice)
2261 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2262 if self.end == usize::max_value() { slice_index_overflow_fail(); }
2263 (self.start..self.end + 1).index_mut(slice)
2267 #[stable(feature = "inclusive_range", since = "1.26.0")]
2268 impl<T> SliceIndex<[T]> for ops::RangeToInclusive<usize> {
2272 fn get(self, slice: &[T]) -> Option<&[T]> {
2273 (0..=self.end).get(slice)
2277 fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
2278 (0..=self.end).get_mut(slice)
2282 unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
2283 (0..=self.end).get_unchecked(slice)
2287 unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
2288 (0..=self.end).get_unchecked_mut(slice)
2292 fn index(self, slice: &[T]) -> &[T] {
2293 (0..=self.end).index(slice)
2297 fn index_mut(self, slice: &mut [T]) -> &mut [T] {
2298 (0..=self.end).index_mut(slice)
2302 ////////////////////////////////////////////////////////////////////////////////
2304 ////////////////////////////////////////////////////////////////////////////////
2306 #[stable(feature = "rust1", since = "1.0.0")]
2307 impl<'a, T> Default for &'a [T] {
2308 /// Creates an empty slice.
2309 fn default() -> &'a [T] { &[] }
2312 #[stable(feature = "mut_slice_default", since = "1.5.0")]
2313 impl<'a, T> Default for &'a mut [T] {
2314 /// Creates a mutable empty slice.
2315 fn default() -> &'a mut [T] { &mut [] }
2322 #[stable(feature = "rust1", since = "1.0.0")]
2323 impl<'a, T> IntoIterator for &'a [T] {
2325 type IntoIter = Iter<'a, T>;
2327 fn into_iter(self) -> Iter<'a, T> {
2332 #[stable(feature = "rust1", since = "1.0.0")]
2333 impl<'a, T> IntoIterator for &'a mut [T] {
2334 type Item = &'a mut T;
2335 type IntoIter = IterMut<'a, T>;
2337 fn into_iter(self) -> IterMut<'a, T> {
2343 fn size_from_ptr<T>(_: *const T) -> usize {
2347 // The shared definition of the `Iter` and `IterMut` iterators
2348 macro_rules! iterator {
2349 (struct $name:ident -> $ptr:ty, $elem:ty, $mkref:ident) => {
2350 #[stable(feature = "rust1", since = "1.0.0")]
2351 impl<'a, T> Iterator for $name<'a, T> {
2355 fn next(&mut self) -> Option<$elem> {
2356 // could be implemented with slices, but this avoids bounds checks
2358 if mem::size_of::<T>() != 0 {
2359 assume(!self.ptr.is_null());
2360 assume(!self.end.is_null());
2362 if self.ptr == self.end {
2365 Some($mkref!(self.ptr.post_inc()))
2371 fn size_hint(&self) -> (usize, Option<usize>) {
2372 let exact = unsafe { ptrdistance(self.ptr, self.end) };
2373 (exact, Some(exact))
2377 fn count(self) -> usize {
2382 fn nth(&mut self, n: usize) -> Option<$elem> {
2383 // Call helper method. Can't put the definition here because mut versus const.
2388 fn last(mut self) -> Option<$elem> {
2393 fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where
2394 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
2396 // manual unrolling is needed when there are conditional exits from the loop
2397 let mut accum = init;
2399 while ptrdistance(self.ptr, self.end) >= 4 {
2400 accum = f(accum, $mkref!(self.ptr.post_inc()))?;
2401 accum = f(accum, $mkref!(self.ptr.post_inc()))?;
2402 accum = f(accum, $mkref!(self.ptr.post_inc()))?;
2403 accum = f(accum, $mkref!(self.ptr.post_inc()))?;
2405 while self.ptr != self.end {
2406 accum = f(accum, $mkref!(self.ptr.post_inc()))?;
2413 fn fold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
2414 where Fold: FnMut(Acc, Self::Item) -> Acc,
2416 // Let LLVM unroll this, rather than using the default
2417 // impl that would force the manual unrolling above
2418 let mut accum = init;
2419 while let Some(x) = self.next() {
2420 accum = f(accum, x);
2426 #[rustc_inherit_overflow_checks]
2427 fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
2429 P: FnMut(Self::Item) -> bool,
2431 // The addition might panic on overflow
2432 // Use the len of the slice to hint optimizer to remove result index bounds check.
2433 let n = make_slice!(self.ptr, self.end).len();
2434 self.try_fold(0, move |i, x| {
2435 if predicate(x) { Err(i) }
2439 unsafe { assume(i < n) };
2445 fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where
2446 P: FnMut(Self::Item) -> bool,
2447 Self: Sized + ExactSizeIterator + DoubleEndedIterator
2449 // No need for an overflow check here, because `ExactSizeIterator`
2450 // implies that the number of elements fits into a `usize`.
2451 // Use the len of the slice to hint optimizer to remove result index bounds check.
2452 let n = make_slice!(self.ptr, self.end).len();
2453 self.try_rfold(n, move |i, x| {
2455 if predicate(x) { Err(i) }
2459 unsafe { assume(i < n) };
2465 #[stable(feature = "rust1", since = "1.0.0")]
2466 impl<'a, T> DoubleEndedIterator for $name<'a, T> {
2468 fn next_back(&mut self) -> Option<$elem> {
2469 // could be implemented with slices, but this avoids bounds checks
2471 if mem::size_of::<T>() != 0 {
2472 assume(!self.ptr.is_null());
2473 assume(!self.end.is_null());
2475 if self.end == self.ptr {
2478 Some($mkref!(self.end.pre_dec()))
2484 fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R where
2485 Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
2487 // manual unrolling is needed when there are conditional exits from the loop
2488 let mut accum = init;
2490 while ptrdistance(self.ptr, self.end) >= 4 {
2491 accum = f(accum, $mkref!(self.end.pre_dec()))?;
2492 accum = f(accum, $mkref!(self.end.pre_dec()))?;
2493 accum = f(accum, $mkref!(self.end.pre_dec()))?;
2494 accum = f(accum, $mkref!(self.end.pre_dec()))?;
2496 while self.ptr != self.end {
2497 accum = f(accum, $mkref!(self.end.pre_dec()))?;
2504 fn rfold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
2505 where Fold: FnMut(Acc, Self::Item) -> Acc,
2507 // Let LLVM unroll this, rather than using the default
2508 // impl that would force the manual unrolling above
2509 let mut accum = init;
2510 while let Some(x) = self.next_back() {
2511 accum = f(accum, x);
2519 macro_rules! make_slice {
2520 ($start: expr, $end: expr) => {{
2522 let diff = ($end as usize).wrapping_sub(start as usize);
2523 if size_from_ptr(start) == 0 {
2524 // use a non-null pointer value
2525 unsafe { from_raw_parts(1 as *const _, diff) }
2527 let len = diff / size_from_ptr(start);
2528 unsafe { from_raw_parts(start, len) }
2533 macro_rules! make_mut_slice {
2534 ($start: expr, $end: expr) => {{
2536 let diff = ($end as usize).wrapping_sub(start as usize);
2537 if size_from_ptr(start) == 0 {
2538 // use a non-null pointer value
2539 unsafe { from_raw_parts_mut(1 as *mut _, diff) }
2541 let len = diff / size_from_ptr(start);
2542 unsafe { from_raw_parts_mut(start, len) }
2547 /// Immutable slice iterator
2549 /// This struct is created by the [`iter`] method on [slices].
2556 /// // First, we declare a type which has `iter` method to get the `Iter` struct (&[usize here]):
2557 /// let slice = &[1, 2, 3];
2559 /// // Then, we iterate over it:
2560 /// for element in slice.iter() {
2561 /// println!("{}", element);
2565 /// [`iter`]: ../../std/primitive.slice.html#method.iter
2566 /// [slices]: ../../std/primitive.slice.html
2567 #[stable(feature = "rust1", since = "1.0.0")]
2568 pub struct Iter<'a, T: 'a> {
2571 _marker: marker::PhantomData<&'a T>,
2574 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2575 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
2576 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2577 f.debug_tuple("Iter")
2578 .field(&self.as_slice())
2583 #[stable(feature = "rust1", since = "1.0.0")]
2584 unsafe impl<'a, T: Sync> Sync for Iter<'a, T> {}
2585 #[stable(feature = "rust1", since = "1.0.0")]
2586 unsafe impl<'a, T: Sync> Send for Iter<'a, T> {}
2588 impl<'a, T> Iter<'a, T> {
2589 /// View the underlying data as a subslice of the original data.
2591 /// This has the same lifetime as the original slice, and so the
2592 /// iterator can continue to be used while this exists.
2599 /// // First, we declare a type which has the `iter` method to get the `Iter`
2600 /// // struct (&[usize here]):
2601 /// let slice = &[1, 2, 3];
2603 /// // Then, we get the iterator:
2604 /// let mut iter = slice.iter();
2605 /// // So if we print what `as_slice` method returns here, we have "[1, 2, 3]":
2606 /// println!("{:?}", iter.as_slice());
2608 /// // Next, we move to the second element of the slice:
2610 /// // Now `as_slice` returns "[2, 3]":
2611 /// println!("{:?}", iter.as_slice());
2613 #[stable(feature = "iter_to_slice", since = "1.4.0")]
2614 pub fn as_slice(&self) -> &'a [T] {
2615 make_slice!(self.ptr, self.end)
2618 // Helper function for Iter::nth
2619 fn iter_nth(&mut self, n: usize) -> Option<&'a T> {
2620 match self.as_slice().get(n) {
2621 Some(elem_ref) => unsafe {
2622 self.ptr = slice_offset!(self.ptr, (n as isize).wrapping_add(1));
2626 self.ptr = self.end;
2633 iterator!{struct Iter -> *const T, &'a T, make_ref}
2635 #[stable(feature = "rust1", since = "1.0.0")]
2636 impl<'a, T> ExactSizeIterator for Iter<'a, T> {
2637 fn is_empty(&self) -> bool {
2638 self.ptr == self.end
2642 #[stable(feature = "fused", since = "1.26.0")]
2643 impl<'a, T> FusedIterator for Iter<'a, T> {}
2645 #[unstable(feature = "trusted_len", issue = "37572")]
2646 unsafe impl<'a, T> TrustedLen for Iter<'a, T> {}
2648 #[stable(feature = "rust1", since = "1.0.0")]
2649 impl<'a, T> Clone for Iter<'a, T> {
2650 fn clone(&self) -> Iter<'a, T> { Iter { ptr: self.ptr, end: self.end, _marker: self._marker } }
2653 #[stable(feature = "slice_iter_as_ref", since = "1.13.0")]
2654 impl<'a, T> AsRef<[T]> for Iter<'a, T> {
2655 fn as_ref(&self) -> &[T] {
2660 /// Mutable slice iterator.
2662 /// This struct is created by the [`iter_mut`] method on [slices].
2669 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
2670 /// // struct (&[usize here]):
2671 /// let mut slice = &mut [1, 2, 3];
2673 /// // Then, we iterate over it and increment each element value:
2674 /// for element in slice.iter_mut() {
2678 /// // We now have "[2, 3, 4]":
2679 /// println!("{:?}", slice);
2682 /// [`iter_mut`]: ../../std/primitive.slice.html#method.iter_mut
2683 /// [slices]: ../../std/primitive.slice.html
2684 #[stable(feature = "rust1", since = "1.0.0")]
2685 pub struct IterMut<'a, T: 'a> {
2688 _marker: marker::PhantomData<&'a mut T>,
2691 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2692 impl<'a, T: 'a + fmt::Debug> fmt::Debug for IterMut<'a, T> {
2693 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2694 f.debug_tuple("IterMut")
2695 .field(&make_slice!(self.ptr, self.end))
2700 #[stable(feature = "rust1", since = "1.0.0")]
2701 unsafe impl<'a, T: Sync> Sync for IterMut<'a, T> {}
2702 #[stable(feature = "rust1", since = "1.0.0")]
2703 unsafe impl<'a, T: Send> Send for IterMut<'a, T> {}
2705 impl<'a, T> IterMut<'a, T> {
2706 /// View the underlying data as a subslice of the original data.
2708 /// To avoid creating `&mut` references that alias, this is forced
2709 /// to consume the iterator. Consider using the `Slice` and
2710 /// `SliceMut` implementations for obtaining slices with more
2711 /// restricted lifetimes that do not consume the iterator.
2718 /// // First, we declare a type which has `iter_mut` method to get the `IterMut`
2719 /// // struct (&[usize here]):
2720 /// let mut slice = &mut [1, 2, 3];
2723 /// // Then, we get the iterator:
2724 /// let mut iter = slice.iter_mut();
2725 /// // We move to next element:
2727 /// // So if we print what `into_slice` method returns here, we have "[2, 3]":
2728 /// println!("{:?}", iter.into_slice());
2731 /// // Now let's modify a value of the slice:
2733 /// // First we get back the iterator:
2734 /// let mut iter = slice.iter_mut();
2735 /// // We change the value of the first element of the slice returned by the `next` method:
2736 /// *iter.next().unwrap() += 1;
2738 /// // Now slice is "[2, 2, 3]":
2739 /// println!("{:?}", slice);
2741 #[stable(feature = "iter_to_slice", since = "1.4.0")]
2742 pub fn into_slice(self) -> &'a mut [T] {
2743 make_mut_slice!(self.ptr, self.end)
2746 // Helper function for IterMut::nth
2747 fn iter_nth(&mut self, n: usize) -> Option<&'a mut T> {
2748 match make_mut_slice!(self.ptr, self.end).get_mut(n) {
2749 Some(elem_ref) => unsafe {
2750 self.ptr = slice_offset!(self.ptr, (n as isize).wrapping_add(1));
2754 self.ptr = self.end;
2761 iterator!{struct IterMut -> *mut T, &'a mut T, make_ref_mut}
2763 #[stable(feature = "rust1", since = "1.0.0")]
2764 impl<'a, T> ExactSizeIterator for IterMut<'a, T> {
2765 fn is_empty(&self) -> bool {
2766 self.ptr == self.end
2770 #[stable(feature = "fused", since = "1.26.0")]
2771 impl<'a, T> FusedIterator for IterMut<'a, T> {}
2773 #[unstable(feature = "trusted_len", issue = "37572")]
2774 unsafe impl<'a, T> TrustedLen for IterMut<'a, T> {}
2777 // Return the number of elements of `T` from `start` to `end`.
2778 // Return the arithmetic difference if `T` is zero size.
2780 unsafe fn ptrdistance<T>(start: *const T, end: *const T) -> usize {
2781 if mem::size_of::<T>() == 0 {
2782 (end as usize).wrapping_sub(start as usize)
2784 end.offset_from(start) as usize
2788 // Extension methods for raw pointers, used by the iterators
2789 trait PointerExt : Copy {
2790 unsafe fn slice_offset(self, i: isize) -> Self;
2792 /// Increments `self` by 1, but returns the old value.
2794 unsafe fn post_inc(&mut self) -> Self {
2795 let current = *self;
2796 *self = self.slice_offset(1);
2800 /// Decrements `self` by 1, and returns the new value.
2802 unsafe fn pre_dec(&mut self) -> Self {
2803 *self = self.slice_offset(-1);
2808 impl<T> PointerExt for *const T {
2810 unsafe fn slice_offset(self, i: isize) -> Self {
2811 slice_offset!(self, i)
2815 impl<T> PointerExt for *mut T {
2817 unsafe fn slice_offset(self, i: isize) -> Self {
2818 slice_offset!(self, i)
2822 /// An internal abstraction over the splitting iterators, so that
2823 /// splitn, splitn_mut etc can be implemented once.
2825 trait SplitIter: DoubleEndedIterator {
2826 /// Marks the underlying iterator as complete, extracting the remaining
2827 /// portion of the slice.
2828 fn finish(&mut self) -> Option<Self::Item>;
2831 /// An iterator over subslices separated by elements that match a predicate
2834 /// This struct is created by the [`split`] method on [slices].
2836 /// [`split`]: ../../std/primitive.slice.html#method.split
2837 /// [slices]: ../../std/primitive.slice.html
2838 #[stable(feature = "rust1", since = "1.0.0")]
2839 pub struct Split<'a, T:'a, P> where P: FnMut(&T) -> bool {
2845 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2846 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for Split<'a, T, P> where P: FnMut(&T) -> bool {
2847 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2848 f.debug_struct("Split")
2849 .field("v", &self.v)
2850 .field("finished", &self.finished)
2855 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
2856 #[stable(feature = "rust1", since = "1.0.0")]
2857 impl<'a, T, P> Clone for Split<'a, T, P> where P: Clone + FnMut(&T) -> bool {
2858 fn clone(&self) -> Split<'a, T, P> {
2861 pred: self.pred.clone(),
2862 finished: self.finished,
2867 #[stable(feature = "rust1", since = "1.0.0")]
2868 impl<'a, T, P> Iterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
2869 type Item = &'a [T];
2872 fn next(&mut self) -> Option<&'a [T]> {
2873 if self.finished { return None; }
2875 match self.v.iter().position(|x| (self.pred)(x)) {
2876 None => self.finish(),
2878 let ret = Some(&self.v[..idx]);
2879 self.v = &self.v[idx + 1..];
2886 fn size_hint(&self) -> (usize, Option<usize>) {
2890 (1, Some(self.v.len() + 1))
2895 #[stable(feature = "rust1", since = "1.0.0")]
2896 impl<'a, T, P> DoubleEndedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
2898 fn next_back(&mut self) -> Option<&'a [T]> {
2899 if self.finished { return None; }
2901 match self.v.iter().rposition(|x| (self.pred)(x)) {
2902 None => self.finish(),
2904 let ret = Some(&self.v[idx + 1..]);
2905 self.v = &self.v[..idx];
2912 impl<'a, T, P> SplitIter for Split<'a, T, P> where P: FnMut(&T) -> bool {
2914 fn finish(&mut self) -> Option<&'a [T]> {
2915 if self.finished { None } else { self.finished = true; Some(self.v) }
2919 #[stable(feature = "fused", since = "1.26.0")]
2920 impl<'a, T, P> FusedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {}
2922 /// An iterator over the subslices of the vector which are separated
2923 /// by elements that match `pred`.
2925 /// This struct is created by the [`split_mut`] method on [slices].
2927 /// [`split_mut`]: ../../std/primitive.slice.html#method.split_mut
2928 /// [slices]: ../../std/primitive.slice.html
2929 #[stable(feature = "rust1", since = "1.0.0")]
2930 pub struct SplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
2936 #[stable(feature = "core_impl_debug", since = "1.9.0")]
2937 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
2938 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2939 f.debug_struct("SplitMut")
2940 .field("v", &self.v)
2941 .field("finished", &self.finished)
2946 impl<'a, T, P> SplitIter for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
2948 fn finish(&mut self) -> Option<&'a mut [T]> {
2952 self.finished = true;
2953 Some(mem::replace(&mut self.v, &mut []))
2958 #[stable(feature = "rust1", since = "1.0.0")]
2959 impl<'a, T, P> Iterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
2960 type Item = &'a mut [T];
2963 fn next(&mut self) -> Option<&'a mut [T]> {
2964 if self.finished { return None; }
2966 let idx_opt = { // work around borrowck limitations
2967 let pred = &mut self.pred;
2968 self.v.iter().position(|x| (*pred)(x))
2971 None => self.finish(),
2973 let tmp = mem::replace(&mut self.v, &mut []);
2974 let (head, tail) = tmp.split_at_mut(idx);
2975 self.v = &mut tail[1..];
2982 fn size_hint(&self) -> (usize, Option<usize>) {
2986 // if the predicate doesn't match anything, we yield one slice
2987 // if it matches every element, we yield len+1 empty slices.
2988 (1, Some(self.v.len() + 1))
2993 #[stable(feature = "rust1", since = "1.0.0")]
2994 impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> where
2995 P: FnMut(&T) -> bool,
2998 fn next_back(&mut self) -> Option<&'a mut [T]> {
2999 if self.finished { return None; }
3001 let idx_opt = { // work around borrowck limitations
3002 let pred = &mut self.pred;
3003 self.v.iter().rposition(|x| (*pred)(x))
3006 None => self.finish(),
3008 let tmp = mem::replace(&mut self.v, &mut []);
3009 let (head, tail) = tmp.split_at_mut(idx);
3011 Some(&mut tail[1..])
3017 #[stable(feature = "fused", since = "1.26.0")]
3018 impl<'a, T, P> FusedIterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {}
3020 /// An iterator over subslices separated by elements that match a predicate
3021 /// function, starting from the end of the slice.
3023 /// This struct is created by the [`rsplit`] method on [slices].
3025 /// [`rsplit`]: ../../std/primitive.slice.html#method.rsplit
3026 /// [slices]: ../../std/primitive.slice.html
3027 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3028 #[derive(Clone)] // Is this correct, or does it incorrectly require `T: Clone`?
3029 pub struct RSplit<'a, T:'a, P> where P: FnMut(&T) -> bool {
3030 inner: Split<'a, T, P>
3033 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3034 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3035 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3036 f.debug_struct("RSplit")
3037 .field("v", &self.inner.v)
3038 .field("finished", &self.inner.finished)
3043 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3044 impl<'a, T, P> Iterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3045 type Item = &'a [T];
3048 fn next(&mut self) -> Option<&'a [T]> {
3049 self.inner.next_back()
3053 fn size_hint(&self) -> (usize, Option<usize>) {
3054 self.inner.size_hint()
3058 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3059 impl<'a, T, P> DoubleEndedIterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3061 fn next_back(&mut self) -> Option<&'a [T]> {
3066 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3067 impl<'a, T, P> SplitIter for RSplit<'a, T, P> where P: FnMut(&T) -> bool {
3069 fn finish(&mut self) -> Option<&'a [T]> {
3074 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3075 impl<'a, T, P> FusedIterator for RSplit<'a, T, P> where P: FnMut(&T) -> bool {}
3077 /// An iterator over the subslices of the vector which are separated
3078 /// by elements that match `pred`, starting from the end of the slice.
3080 /// This struct is created by the [`rsplit_mut`] method on [slices].
3082 /// [`rsplit_mut`]: ../../std/primitive.slice.html#method.rsplit_mut
3083 /// [slices]: ../../std/primitive.slice.html
3084 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3085 pub struct RSplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
3086 inner: SplitMut<'a, T, P>
3089 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3090 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3091 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3092 f.debug_struct("RSplitMut")
3093 .field("v", &self.inner.v)
3094 .field("finished", &self.inner.finished)
3099 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3100 impl<'a, T, P> SplitIter for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3102 fn finish(&mut self) -> Option<&'a mut [T]> {
3107 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3108 impl<'a, T, P> Iterator for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {
3109 type Item = &'a mut [T];
3112 fn next(&mut self) -> Option<&'a mut [T]> {
3113 self.inner.next_back()
3117 fn size_hint(&self) -> (usize, Option<usize>) {
3118 self.inner.size_hint()
3122 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3123 impl<'a, T, P> DoubleEndedIterator for RSplitMut<'a, T, P> where
3124 P: FnMut(&T) -> bool,
3127 fn next_back(&mut self) -> Option<&'a mut [T]> {
3132 #[stable(feature = "slice_rsplit", since = "1.27.0")]
3133 impl<'a, T, P> FusedIterator for RSplitMut<'a, T, P> where P: FnMut(&T) -> bool {}
3135 /// An private iterator over subslices separated by elements that
3136 /// match a predicate function, splitting at most a fixed number of
3139 struct GenericSplitN<I> {
3144 impl<T, I: SplitIter<Item=T>> Iterator for GenericSplitN<I> {
3148 fn next(&mut self) -> Option<T> {
3151 1 => { self.count -= 1; self.iter.finish() }
3152 _ => { self.count -= 1; self.iter.next() }
3157 fn size_hint(&self) -> (usize, Option<usize>) {
3158 let (lower, upper_opt) = self.iter.size_hint();
3159 (lower, upper_opt.map(|upper| cmp::min(self.count, upper)))
3163 /// An iterator over subslices separated by elements that match a predicate
3164 /// function, limited to a given number of splits.
3166 /// This struct is created by the [`splitn`] method on [slices].
3168 /// [`splitn`]: ../../std/primitive.slice.html#method.splitn
3169 /// [slices]: ../../std/primitive.slice.html
3170 #[stable(feature = "rust1", since = "1.0.0")]
3171 pub struct SplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3172 inner: GenericSplitN<Split<'a, T, P>>
3175 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3176 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitN<'a, T, P> where P: FnMut(&T) -> bool {
3177 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3178 f.debug_struct("SplitN")
3179 .field("inner", &self.inner)
3184 /// An iterator over subslices separated by elements that match a
3185 /// predicate function, limited to a given number of splits, starting
3186 /// from the end of the slice.
3188 /// This struct is created by the [`rsplitn`] method on [slices].
3190 /// [`rsplitn`]: ../../std/primitive.slice.html#method.rsplitn
3191 /// [slices]: ../../std/primitive.slice.html
3192 #[stable(feature = "rust1", since = "1.0.0")]
3193 pub struct RSplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3194 inner: GenericSplitN<RSplit<'a, T, P>>
3197 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3198 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitN<'a, T, P> where P: FnMut(&T) -> bool {
3199 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3200 f.debug_struct("RSplitN")
3201 .field("inner", &self.inner)
3206 /// An iterator over subslices separated by elements that match a predicate
3207 /// function, limited to a given number of splits.
3209 /// This struct is created by the [`splitn_mut`] method on [slices].
3211 /// [`splitn_mut`]: ../../std/primitive.slice.html#method.splitn_mut
3212 /// [slices]: ../../std/primitive.slice.html
3213 #[stable(feature = "rust1", since = "1.0.0")]
3214 pub struct SplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3215 inner: GenericSplitN<SplitMut<'a, T, P>>
3218 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3219 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitNMut<'a, T, P> where P: FnMut(&T) -> bool {
3220 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3221 f.debug_struct("SplitNMut")
3222 .field("inner", &self.inner)
3227 /// An iterator over subslices separated by elements that match a
3228 /// predicate function, limited to a given number of splits, starting
3229 /// from the end of the slice.
3231 /// This struct is created by the [`rsplitn_mut`] method on [slices].
3233 /// [`rsplitn_mut`]: ../../std/primitive.slice.html#method.rsplitn_mut
3234 /// [slices]: ../../std/primitive.slice.html
3235 #[stable(feature = "rust1", since = "1.0.0")]
3236 pub struct RSplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
3237 inner: GenericSplitN<RSplitMut<'a, T, P>>
3240 #[stable(feature = "core_impl_debug", since = "1.9.0")]
3241 impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitNMut<'a, T, P> where P: FnMut(&T) -> bool {
3242 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
3243 f.debug_struct("RSplitNMut")
3244 .field("inner", &self.inner)
3249 macro_rules! forward_iterator {
3250 ($name:ident: $elem:ident, $iter_of:ty) => {
3251 #[stable(feature = "rust1", since = "1.0.0")]
3252 impl<'a, $elem, P> Iterator for $name<'a, $elem, P> where
3253 P: FnMut(&T) -> bool
3255 type Item = $iter_of;
3258 fn next(&mut self) -> Option<$iter_of> {
3263 fn size_hint(&self) -> (usize, Option<usize>) {
3264 self.inner.size_hint()
3268 #[stable(feature = "fused", since = "1.26.0")]
3269 impl<'a, $elem, P> FusedIterator for $name<'a, $elem, P>
3270 where P: FnMut(&T) -> bool {}
3274 forward_iterator! { SplitN: T, &'a [T] }
3275 forward_iterator! { RSplitN: T, &'a [T] }
3276 forward_iterator! { SplitNMut: T, &'a mut [T] }
3277 forward_iterator! { RSplitNMut: T, &'a mut [T] }
3279 /// An iterator over overlapping subslices of length `size`.
3281 /// This struct is created by the [`windows`] method on [slices].
3283 /// [`windows`]: ../../std/primitive.slice.html#method.windows
3284 /// [slices]: ../../std/primitive.slice.html
3286 #[stable(feature = "rust1", since = "1.0.0")]
3287 pub struct Windows<'a, T:'a> {
3292 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3293 #[stable(feature = "rust1", since = "1.0.0")]
3294 impl<'a, T> Clone for Windows<'a, T> {
3295 fn clone(&self) -> Windows<'a, T> {
3303 #[stable(feature = "rust1", since = "1.0.0")]
3304 impl<'a, T> Iterator for Windows<'a, T> {
3305 type Item = &'a [T];
3308 fn next(&mut self) -> Option<&'a [T]> {
3309 if self.size > self.v.len() {
3312 let ret = Some(&self.v[..self.size]);
3313 self.v = &self.v[1..];
3319 fn size_hint(&self) -> (usize, Option<usize>) {
3320 if self.size > self.v.len() {
3323 let size = self.v.len() - self.size + 1;
3329 fn count(self) -> usize {
3334 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3335 let (end, overflow) = self.size.overflowing_add(n);
3336 if end > self.v.len() || overflow {
3340 let nth = &self.v[n..end];
3341 self.v = &self.v[n+1..];
3347 fn last(self) -> Option<Self::Item> {
3348 if self.size > self.v.len() {
3351 let start = self.v.len() - self.size;
3352 Some(&self.v[start..])
3357 #[stable(feature = "rust1", since = "1.0.0")]
3358 impl<'a, T> DoubleEndedIterator for Windows<'a, T> {
3360 fn next_back(&mut self) -> Option<&'a [T]> {
3361 if self.size > self.v.len() {
3364 let ret = Some(&self.v[self.v.len()-self.size..]);
3365 self.v = &self.v[..self.v.len()-1];
3371 #[stable(feature = "rust1", since = "1.0.0")]
3372 impl<'a, T> ExactSizeIterator for Windows<'a, T> {}
3374 #[stable(feature = "fused", since = "1.26.0")]
3375 impl<'a, T> FusedIterator for Windows<'a, T> {}
3378 unsafe impl<'a, T> TrustedRandomAccess for Windows<'a, T> {
3379 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3380 from_raw_parts(self.v.as_ptr().offset(i as isize), self.size)
3382 fn may_have_side_effect() -> bool { false }
3385 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
3388 /// When the slice len is not evenly divided by the chunk size, the last slice
3389 /// of the iteration will be the remainder.
3391 /// This struct is created by the [`chunks`] method on [slices].
3393 /// [`chunks`]: ../../std/primitive.slice.html#method.chunks
3394 /// [slices]: ../../std/primitive.slice.html
3396 #[stable(feature = "rust1", since = "1.0.0")]
3397 pub struct Chunks<'a, T:'a> {
3402 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3403 #[stable(feature = "rust1", since = "1.0.0")]
3404 impl<'a, T> Clone for Chunks<'a, T> {
3405 fn clone(&self) -> Chunks<'a, T> {
3408 chunk_size: self.chunk_size,
3413 #[stable(feature = "rust1", since = "1.0.0")]
3414 impl<'a, T> Iterator for Chunks<'a, T> {
3415 type Item = &'a [T];
3418 fn next(&mut self) -> Option<&'a [T]> {
3419 if self.v.is_empty() {
3422 let chunksz = cmp::min(self.v.len(), self.chunk_size);
3423 let (fst, snd) = self.v.split_at(chunksz);
3430 fn size_hint(&self) -> (usize, Option<usize>) {
3431 if self.v.is_empty() {
3434 let n = self.v.len() / self.chunk_size;
3435 let rem = self.v.len() % self.chunk_size;
3436 let n = if rem > 0 { n+1 } else { n };
3442 fn count(self) -> usize {
3447 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3448 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3449 if start >= self.v.len() || overflow {
3453 let end = match start.checked_add(self.chunk_size) {
3454 Some(sum) => cmp::min(self.v.len(), sum),
3455 None => self.v.len(),
3457 let nth = &self.v[start..end];
3458 self.v = &self.v[end..];
3464 fn last(self) -> Option<Self::Item> {
3465 if self.v.is_empty() {
3468 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
3469 Some(&self.v[start..])
3474 #[stable(feature = "rust1", since = "1.0.0")]
3475 impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
3477 fn next_back(&mut self) -> Option<&'a [T]> {
3478 if self.v.is_empty() {
3481 let remainder = self.v.len() % self.chunk_size;
3482 let chunksz = if remainder != 0 { remainder } else { self.chunk_size };
3483 let (fst, snd) = self.v.split_at(self.v.len() - chunksz);
3490 #[stable(feature = "rust1", since = "1.0.0")]
3491 impl<'a, T> ExactSizeIterator for Chunks<'a, T> {}
3493 #[stable(feature = "fused", since = "1.26.0")]
3494 impl<'a, T> FusedIterator for Chunks<'a, T> {}
3497 unsafe impl<'a, T> TrustedRandomAccess for Chunks<'a, T> {
3498 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3499 let start = i * self.chunk_size;
3500 let end = match start.checked_add(self.chunk_size) {
3501 None => self.v.len(),
3502 Some(end) => cmp::min(end, self.v.len()),
3504 from_raw_parts(self.v.as_ptr().offset(start as isize), end - start)
3506 fn may_have_side_effect() -> bool { false }
3509 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3510 /// elements at a time). When the slice len is not evenly divided by the chunk
3511 /// size, the last slice of the iteration will be the remainder.
3513 /// This struct is created by the [`chunks_mut`] method on [slices].
3515 /// [`chunks_mut`]: ../../std/primitive.slice.html#method.chunks_mut
3516 /// [slices]: ../../std/primitive.slice.html
3518 #[stable(feature = "rust1", since = "1.0.0")]
3519 pub struct ChunksMut<'a, T:'a> {
3524 #[stable(feature = "rust1", since = "1.0.0")]
3525 impl<'a, T> Iterator for ChunksMut<'a, T> {
3526 type Item = &'a mut [T];
3529 fn next(&mut self) -> Option<&'a mut [T]> {
3530 if self.v.is_empty() {
3533 let sz = cmp::min(self.v.len(), self.chunk_size);
3534 let tmp = mem::replace(&mut self.v, &mut []);
3535 let (head, tail) = tmp.split_at_mut(sz);
3542 fn size_hint(&self) -> (usize, Option<usize>) {
3543 if self.v.is_empty() {
3546 let n = self.v.len() / self.chunk_size;
3547 let rem = self.v.len() % self.chunk_size;
3548 let n = if rem > 0 { n + 1 } else { n };
3554 fn count(self) -> usize {
3559 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
3560 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3561 if start >= self.v.len() || overflow {
3565 let end = match start.checked_add(self.chunk_size) {
3566 Some(sum) => cmp::min(self.v.len(), sum),
3567 None => self.v.len(),
3569 let tmp = mem::replace(&mut self.v, &mut []);
3570 let (head, tail) = tmp.split_at_mut(end);
3571 let (_, nth) = head.split_at_mut(start);
3578 fn last(self) -> Option<Self::Item> {
3579 if self.v.is_empty() {
3582 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
3583 Some(&mut self.v[start..])
3588 #[stable(feature = "rust1", since = "1.0.0")]
3589 impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
3591 fn next_back(&mut self) -> Option<&'a mut [T]> {
3592 if self.v.is_empty() {
3595 let remainder = self.v.len() % self.chunk_size;
3596 let sz = if remainder != 0 { remainder } else { self.chunk_size };
3597 let tmp = mem::replace(&mut self.v, &mut []);
3598 let tmp_len = tmp.len();
3599 let (head, tail) = tmp.split_at_mut(tmp_len - sz);
3606 #[stable(feature = "rust1", since = "1.0.0")]
3607 impl<'a, T> ExactSizeIterator for ChunksMut<'a, T> {}
3609 #[stable(feature = "fused", since = "1.26.0")]
3610 impl<'a, T> FusedIterator for ChunksMut<'a, T> {}
3613 unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> {
3614 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
3615 let start = i * self.chunk_size;
3616 let end = match start.checked_add(self.chunk_size) {
3617 None => self.v.len(),
3618 Some(end) => cmp::min(end, self.v.len()),
3620 from_raw_parts_mut(self.v.as_mut_ptr().offset(start as isize), end - start)
3622 fn may_have_side_effect() -> bool { false }
3625 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
3628 /// When the slice len is not evenly divided by the chunk size, the last
3629 /// up to `chunk_size-1` elements will be omitted.
3631 /// This struct is created by the [`exact_chunks`] method on [slices].
3633 /// [`exact_chunks`]: ../../std/primitive.slice.html#method.exact_chunks
3634 /// [slices]: ../../std/primitive.slice.html
3636 #[unstable(feature = "exact_chunks", issue = "47115")]
3637 pub struct ExactChunks<'a, T:'a> {
3642 // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
3643 #[unstable(feature = "exact_chunks", issue = "47115")]
3644 impl<'a, T> Clone for ExactChunks<'a, T> {
3645 fn clone(&self) -> ExactChunks<'a, T> {
3648 chunk_size: self.chunk_size,
3653 #[unstable(feature = "exact_chunks", issue = "47115")]
3654 impl<'a, T> Iterator for ExactChunks<'a, T> {
3655 type Item = &'a [T];
3658 fn next(&mut self) -> Option<&'a [T]> {
3659 if self.v.len() < self.chunk_size {
3662 let (fst, snd) = self.v.split_at(self.chunk_size);
3669 fn size_hint(&self) -> (usize, Option<usize>) {
3670 let n = self.v.len() / self.chunk_size;
3675 fn count(self) -> usize {
3680 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3681 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3682 if start >= self.v.len() || overflow {
3686 let (_, snd) = self.v.split_at(start);
3693 fn last(mut self) -> Option<Self::Item> {
3698 #[unstable(feature = "exact_chunks", issue = "47115")]
3699 impl<'a, T> DoubleEndedIterator for ExactChunks<'a, T> {
3701 fn next_back(&mut self) -> Option<&'a [T]> {
3702 if self.v.len() < self.chunk_size {
3705 let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size);
3712 #[unstable(feature = "exact_chunks", issue = "47115")]
3713 impl<'a, T> ExactSizeIterator for ExactChunks<'a, T> {
3714 fn is_empty(&self) -> bool {
3719 #[unstable(feature = "exact_chunks", issue = "47115")]
3720 impl<'a, T> FusedIterator for ExactChunks<'a, T> {}
3723 unsafe impl<'a, T> TrustedRandomAccess for ExactChunks<'a, T> {
3724 unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] {
3725 let start = i * self.chunk_size;
3726 from_raw_parts(self.v.as_ptr().offset(start as isize), self.chunk_size)
3728 fn may_have_side_effect() -> bool { false }
3731 /// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3732 /// elements at a time). When the slice len is not evenly divided by the chunk
3733 /// size, the last up to `chunk_size-1` elements will be omitted.
3735 /// This struct is created by the [`exact_chunks_mut`] method on [slices].
3737 /// [`exact_chunks_mut`]: ../../std/primitive.slice.html#method.exact_chunks_mut
3738 /// [slices]: ../../std/primitive.slice.html
3740 #[unstable(feature = "exact_chunks", issue = "47115")]
3741 pub struct ExactChunksMut<'a, T:'a> {
3746 #[unstable(feature = "exact_chunks", issue = "47115")]
3747 impl<'a, T> Iterator for ExactChunksMut<'a, T> {
3748 type Item = &'a mut [T];
3751 fn next(&mut self) -> Option<&'a mut [T]> {
3752 if self.v.len() < self.chunk_size {
3755 let tmp = mem::replace(&mut self.v, &mut []);
3756 let (head, tail) = tmp.split_at_mut(self.chunk_size);
3763 fn size_hint(&self) -> (usize, Option<usize>) {
3764 let n = self.v.len() / self.chunk_size;
3769 fn count(self) -> usize {
3774 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
3775 let (start, overflow) = n.overflowing_mul(self.chunk_size);
3776 if start >= self.v.len() || overflow {
3780 let tmp = mem::replace(&mut self.v, &mut []);
3781 let (_, snd) = tmp.split_at_mut(start);
3788 fn last(mut self) -> Option<Self::Item> {
3793 #[unstable(feature = "exact_chunks", issue = "47115")]
3794 impl<'a, T> DoubleEndedIterator for ExactChunksMut<'a, T> {
3796 fn next_back(&mut self) -> Option<&'a mut [T]> {
3797 if self.v.len() < self.chunk_size {
3800 let tmp = mem::replace(&mut self.v, &mut []);
3801 let tmp_len = tmp.len();
3802 let (head, tail) = tmp.split_at_mut(tmp_len - self.chunk_size);
3809 #[unstable(feature = "exact_chunks", issue = "47115")]
3810 impl<'a, T> ExactSizeIterator for ExactChunksMut<'a, T> {
3811 fn is_empty(&self) -> bool {
3816 #[unstable(feature = "exact_chunks", issue = "47115")]
3817 impl<'a, T> FusedIterator for ExactChunksMut<'a, T> {}
3820 unsafe impl<'a, T> TrustedRandomAccess for ExactChunksMut<'a, T> {
3821 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] {
3822 let start = i * self.chunk_size;
3823 from_raw_parts_mut(self.v.as_mut_ptr().offset(start as isize), self.chunk_size)
3825 fn may_have_side_effect() -> bool { false }
3832 /// Forms a slice from a pointer and a length.
3834 /// The `len` argument is the number of **elements**, not the number of bytes.
3838 /// This function is unsafe as there is no guarantee that the given pointer is
3839 /// valid for `len` elements, nor whether the lifetime inferred is a suitable
3840 /// lifetime for the returned slice.
3842 /// `p` must be non-null and aligned, even for zero-length slices, as is
3843 /// required for all references. However, for zero-length slices, `p` can be
3844 /// a bogus non-dereferencable pointer such as [`NonNull::dangling()`].
3848 /// The lifetime for the returned slice is inferred from its usage. To
3849 /// prevent accidental misuse, it's suggested to tie the lifetime to whichever
3850 /// source lifetime is safe in the context, such as by providing a helper
3851 /// function taking the lifetime of a host value for the slice, or by explicit
3859 /// // manifest a slice out of thin air!
3860 /// let ptr = 0x1234 as *const usize;
3863 /// let slice = slice::from_raw_parts(ptr, amt);
3867 /// [`NonNull::dangling()`]: ../../std/ptr/struct.NonNull.html#method.dangling
3869 #[stable(feature = "rust1", since = "1.0.0")]
3870 pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
3871 Repr { raw: FatPtr { data, len } }.rust
3874 /// Performs the same functionality as `from_raw_parts`, except that a mutable
3875 /// slice is returned.
3877 /// This function is unsafe for the same reasons as `from_raw_parts`, as well
3878 /// as not being able to provide a non-aliasing guarantee of the returned
3879 /// mutable slice. `p` must be non-null and aligned even for zero-length slices as with
3880 /// `from_raw_parts`.
3882 #[stable(feature = "rust1", since = "1.0.0")]
3883 pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] {
3884 Repr { raw: FatPtr { data, len} }.rust_mut
3887 /// Converts a reference to T into a slice of length 1 (without copying).
3888 #[stable(feature = "from_ref", since = "1.28.0")]
3889 pub fn from_ref<T>(s: &T) -> &[T] {
3891 from_raw_parts(s, 1)
3895 /// Converts a reference to T into a slice of length 1 (without copying).
3896 #[stable(feature = "from_ref", since = "1.28.0")]
3897 pub fn from_mut<T>(s: &mut T) -> &mut [T] {
3899 from_raw_parts_mut(s, 1)
3903 // This function is public only because there is no other way to unit test heapsort.
3904 #[unstable(feature = "sort_internals", reason = "internal to sort module", issue = "0")]
3906 pub fn heapsort<T, F>(v: &mut [T], mut is_less: F)
3907 where F: FnMut(&T, &T) -> bool
3909 sort::heapsort(v, &mut is_less);
3913 // Comparison traits
3917 /// Calls implementation provided memcmp.
3919 /// Interprets the data as u8.
3921 /// Returns 0 for equal, < 0 for less than and > 0 for greater
3923 // FIXME(#32610): Return type should be c_int
3924 fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32;
3927 #[stable(feature = "rust1", since = "1.0.0")]
3928 impl<A, B> PartialEq<[B]> for [A] where A: PartialEq<B> {
3929 fn eq(&self, other: &[B]) -> bool {
3930 SlicePartialEq::equal(self, other)
3933 fn ne(&self, other: &[B]) -> bool {
3934 SlicePartialEq::not_equal(self, other)
3938 #[stable(feature = "rust1", since = "1.0.0")]
3939 impl<T: Eq> Eq for [T] {}
3941 /// Implements comparison of vectors lexicographically.
3942 #[stable(feature = "rust1", since = "1.0.0")]
3943 impl<T: Ord> Ord for [T] {
3944 fn cmp(&self, other: &[T]) -> Ordering {
3945 SliceOrd::compare(self, other)
3949 /// Implements comparison of vectors lexicographically.
3950 #[stable(feature = "rust1", since = "1.0.0")]
3951 impl<T: PartialOrd> PartialOrd for [T] {
3952 fn partial_cmp(&self, other: &[T]) -> Option<Ordering> {
3953 SlicePartialOrd::partial_compare(self, other)
3958 // intermediate trait for specialization of slice's PartialEq
3959 trait SlicePartialEq<B> {
3960 fn equal(&self, other: &[B]) -> bool;
3962 fn not_equal(&self, other: &[B]) -> bool { !self.equal(other) }
3965 // Generic slice equality
3966 impl<A, B> SlicePartialEq<B> for [A]
3967 where A: PartialEq<B>
3969 default fn equal(&self, other: &[B]) -> bool {
3970 if self.len() != other.len() {
3974 for i in 0..self.len() {
3975 if !self[i].eq(&other[i]) {
3984 // Use memcmp for bytewise equality when the types allow
3985 impl<A> SlicePartialEq<A> for [A]
3986 where A: PartialEq<A> + BytewiseEquality
3988 fn equal(&self, other: &[A]) -> bool {
3989 if self.len() != other.len() {
3992 if self.as_ptr() == other.as_ptr() {
3996 let size = mem::size_of_val(self);
3997 memcmp(self.as_ptr() as *const u8,
3998 other.as_ptr() as *const u8, size) == 0
4004 // intermediate trait for specialization of slice's PartialOrd
4005 trait SlicePartialOrd<B> {
4006 fn partial_compare(&self, other: &[B]) -> Option<Ordering>;
4009 impl<A> SlicePartialOrd<A> for [A]
4012 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
4013 let l = cmp::min(self.len(), other.len());
4015 // Slice to the loop iteration range to enable bound check
4016 // elimination in the compiler
4017 let lhs = &self[..l];
4018 let rhs = &other[..l];
4021 match lhs[i].partial_cmp(&rhs[i]) {
4022 Some(Ordering::Equal) => (),
4023 non_eq => return non_eq,
4027 self.len().partial_cmp(&other.len())
4031 impl<A> SlicePartialOrd<A> for [A]
4034 default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
4035 Some(SliceOrd::compare(self, other))
4040 // intermediate trait for specialization of slice's Ord
4042 fn compare(&self, other: &[B]) -> Ordering;
4045 impl<A> SliceOrd<A> for [A]
4048 default fn compare(&self, other: &[A]) -> Ordering {
4049 let l = cmp::min(self.len(), other.len());
4051 // Slice to the loop iteration range to enable bound check
4052 // elimination in the compiler
4053 let lhs = &self[..l];
4054 let rhs = &other[..l];
4057 match lhs[i].cmp(&rhs[i]) {
4058 Ordering::Equal => (),
4059 non_eq => return non_eq,
4063 self.len().cmp(&other.len())
4067 // memcmp compares a sequence of unsigned bytes lexicographically.
4068 // this matches the order we want for [u8], but no others (not even [i8]).
4069 impl SliceOrd<u8> for [u8] {
4071 fn compare(&self, other: &[u8]) -> Ordering {
4072 let order = unsafe {
4073 memcmp(self.as_ptr(), other.as_ptr(),
4074 cmp::min(self.len(), other.len()))
4077 self.len().cmp(&other.len())
4078 } else if order < 0 {
4087 /// Trait implemented for types that can be compared for equality using
4088 /// their bytewise representation
4089 trait BytewiseEquality { }
4091 macro_rules! impl_marker_for {
4092 ($traitname:ident, $($ty:ty)*) => {
4094 impl $traitname for $ty { }
4099 impl_marker_for!(BytewiseEquality,
4100 u8 i8 u16 i16 u32 i32 u64 i64 usize isize char bool);
4103 unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {
4104 unsafe fn get_unchecked(&mut self, i: usize) -> &'a T {
4105 &*self.ptr.offset(i as isize)
4107 fn may_have_side_effect() -> bool { false }
4111 unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> {
4112 unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut T {
4113 &mut *self.ptr.offset(i as isize)
4115 fn may_have_side_effect() -> bool { false }
4118 trait SliceContains: Sized {
4119 fn slice_contains(&self, x: &[Self]) -> bool;
4122 impl<T> SliceContains for T where T: PartialEq {
4123 default fn slice_contains(&self, x: &[Self]) -> bool {
4124 x.iter().any(|y| *y == *self)
4128 impl SliceContains for u8 {
4129 fn slice_contains(&self, x: &[Self]) -> bool {
4130 memchr::memchr(*self, x).is_some()
4134 impl SliceContains for i8 {
4135 fn slice_contains(&self, x: &[Self]) -> bool {
4136 let byte = *self as u8;
4137 let bytes: &[u8] = unsafe { from_raw_parts(x.as_ptr() as *const u8, x.len()) };
4138 memchr::memchr(byte, bytes).is_some()