iter.rs - source (original) (raw)
core/slice/
iter.rs
1//! Definitions of a bunch of iterators for `[T]`.
2
3#[macro_use] // import iterator! and forward_iterator!
4mod macros;
5
6use super::{from_raw_parts, from_raw_parts_mut};
7use crate::hint::assert_unchecked;
8use crate::iter::{
9 FusedIterator, TrustedLen, TrustedRandomAccess, TrustedRandomAccessNoCoerce, UncheckedIterator,
10};
11use crate:📑:PhantomData;
12use crate::mem::{self, SizedTypeProperties};
13use crate::num::NonZero;
14use crate::ptr::{NonNull, without_provenance, without_provenance_mut};
15use crate::{cmp, fmt};
16
17#[stable(feature = "boxed_slice_into_iter", since = "1.80.0")]
18impl<T> !Iterator for [T] {}
19
20#[stable(feature = "rust1", since = "1.0.0")]
21impl<'a, T> IntoIterator for &'a [T] {
22 type Item = &'a T;
23 type IntoIter = Iter<'a, T>;
24
25 fn into_iter(self) -> Iter<'a, T> {
26 self.iter()
27 }
28}
29
30#[stable(feature = "rust1", since = "1.0.0")]
31impl<'a, T> IntoIterator for &'a mut [T] {
32 type Item = &'a mut T;
33 type IntoIter = IterMut<'a, T>;
34
35 fn into_iter(self) -> IterMut<'a, T> {
36 self.iter_mut()
37 }
38}
39
40/// Immutable slice iterator
41///
42/// This struct is created by the [`iter`] method on [slices].
43///
44/// # Examples
45///
46/// Basic usage:
47///
48/// ```
49/// // First, we need a slice to call the `iter` method on:
50/// let slice = &[1, 2, 3];
51///
52/// // Then we call `iter` on the slice to get the `Iter` iterator,
53/// // and iterate over it:
54/// for element in slice.iter() {
55/// println!("{element}");
56/// }
57///
58/// // This for loop actually already works without calling `iter`:
59/// for element in slice {
60/// println!("{element}");
61/// }
62/// ```
63///
64/// [`iter`]: slice::iter
65/// [slices]: slice
66#[stable(feature = "rust1", since = "1.0.0")]
67#[must_use = "iterators are lazy and do nothing unless consumed"]
68#[rustc_diagnostic_item = "SliceIter"]
69pub struct Iter<'a, T: 'a> {
70 /// The pointer to the next element to return, or the past-the-end location
71 /// if the iterator is empty.
72 ///
73 /// This address will be used for all ZST elements, never changed.
74 ptr: NonNull<T>,
75 /// For non-ZSTs, the non-null pointer to the past-the-end element.
76 ///
77 /// For ZSTs, this is `ptr::without_provenance_mut(len)`.
78 end_or_len: *const T,
79 _marker: PhantomData<&'a T>,
80}
81
82#[stable(feature = "core_impl_debug", since = "1.9.0")]
83impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
84 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
85 f.debug_tuple("Iter").field(&self.as_slice()).finish()
86 }
87}
88
89#[stable(feature = "rust1", since = "1.0.0")]
90unsafe impl<T: Sync> Sync for Iter<'_, T> {}
91#[stable(feature = "rust1", since = "1.0.0")]
92unsafe impl<T: Sync> Send for Iter<'_, T> {}
93
94impl<'a, T> Iter<'a, T> {
95 #[inline]
96 pub(super) const fn new(slice: &'a [T]) -> Self {
97 let len = slice.len();
98 let ptr: NonNull<T> = NonNull::from_ref(slice).cast();
99 // SAFETY: Similar to `IterMut::new`.
100 unsafe {
101 let end_or_len =
102 if T::IS_ZST { without_provenance(len) } else { ptr.as_ptr().add(len) };
103
104 Self { ptr, end_or_len, _marker: PhantomData }
105 }
106 }
107
108 /// Views the underlying data as a subslice of the original data.
109 ///
110 /// # Examples
111 ///
112 /// Basic usage:
113 ///
114 /// ```
115 /// // First, we need a slice to call the `iter` method on:
116 /// let slice = &[1, 2, 3];
117 ///
118 /// // Then we call `iter` on the slice to get the `Iter` iterator:
119 /// let mut iter = slice.iter();
120 /// // Here `as_slice` still returns the whole slice, so this prints "[1, 2, 3]":
121 /// println!("{:?}", iter.as_slice());
122 ///
123 /// // Now, we call the `next` method to remove the first element from the iterator:
124 /// iter.next();
125 /// // Here the iterator does not contain the first element of the slice any more,
126 /// // so `as_slice` only returns the last two elements of the slice,
127 /// // and so this prints "[2, 3]":
128 /// println!("{:?}", iter.as_slice());
129 ///
130 /// // The underlying slice has not been modified and still contains three elements,
131 /// // so this prints "[1, 2, 3]":
132 /// println!("{:?}", slice);
133 /// ```
134 #[must_use]
135 #[stable(feature = "iter_to_slice", since = "1.4.0")]
136 #[inline]
137 pub fn as_slice(&self) -> &'a [T] {
138 self.make_slice()
139 }
140}
141
142iterator! {struct Iter -> *const T, &'a T, const, {/* no mut */}, as_ref, {
143 fn is_sorted_by<F>(self, mut compare: F) -> bool
144 where
145 Self: Sized,
146 F: FnMut(&Self::Item, &Self::Item) -> bool,
147 {
148 self.as_slice().is_sorted_by(|a, b| compare(&a, &b))
149 }
150}}
151
152#[stable(feature = "rust1", since = "1.0.0")]
153impl<T> Clone for Iter<'_, T> {
154 #[inline]
155 fn clone(&self) -> Self {
156 Iter { ptr: self.ptr, end_or_len: self.end_or_len, _marker: self._marker }
157 }
158}
159
160#[stable(feature = "slice_iter_as_ref", since = "1.13.0")]
161impl<T> AsRef<[T]> for Iter<'_, T> {
162 #[inline]
163 fn as_ref(&self) -> &[T] {
164 self.as_slice()
165 }
166}
167
168/// Mutable slice iterator.
169///
170/// This struct is created by the [`iter_mut`] method on [slices].
171///
172/// # Examples
173///
174/// Basic usage:
175///
176/// ```
177/// // First, we need a slice to call the `iter_mut` method on:
178/// let slice = &mut [1, 2, 3];
179///
180/// // Then we call `iter_mut` on the slice to get the `IterMut` iterator,
181/// // iterate over it and increment each element value:
182/// for element in slice.iter_mut() {
183/// *element += 1;
184/// }
185///
186/// // We now have "[2, 3, 4]":
187/// println!("{slice:?}");
188/// ```
189///
190/// [`iter_mut`]: slice::iter_mut
191/// [slices]: slice
192#[stable(feature = "rust1", since = "1.0.0")]
193#[must_use = "iterators are lazy and do nothing unless consumed"]
194pub struct IterMut<'a, T: 'a> {
195 /// The pointer to the next element to return, or the past-the-end location
196 /// if the iterator is empty.
197 ///
198 /// This address will be used for all ZST elements, never changed.
199 ptr: NonNull<T>,
200 /// For non-ZSTs, the non-null pointer to the past-the-end element.
201 ///
202 /// For ZSTs, this is `ptr::without_provenance_mut(len)`.
203 end_or_len: *mut T,
204 _marker: PhantomData<&'a mut T>,
205}
206
207#[stable(feature = "core_impl_debug", since = "1.9.0")]
208impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
209 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
210 f.debug_tuple("IterMut").field(&self.make_slice()).finish()
211 }
212}
213
214#[stable(feature = "rust1", since = "1.0.0")]
215unsafe impl<T: Sync> Sync for IterMut<'_, T> {}
216#[stable(feature = "rust1", since = "1.0.0")]
217unsafe impl<T: Send> Send for IterMut<'_, T> {}
218
219impl<'a, T> IterMut<'a, T> {
220 #[inline]
221 pub(super) const fn new(slice: &'a mut [T]) -> Self {
222 let len = slice.len();
223 let ptr: NonNull<T> = NonNull::from_mut(slice).cast();
224 // SAFETY: There are several things here:
225 //
226 // `ptr` has been obtained by `slice.as_ptr()` where `slice` is a valid
227 // reference thus it is non-NUL and safe to use and pass to
228 // `NonNull::new_unchecked` .
229 //
230 // Adding `slice.len()` to the starting pointer gives a pointer
231 // at the end of `slice`. `end` will never be dereferenced, only checked
232 // for direct pointer equality with `ptr` to check if the iterator is
233 // done.
234 //
235 // In the case of a ZST, the end pointer is just the length. It's never
236 // used as a pointer at all, and thus it's fine to have no provenance.
237 //
238 // See the `next_unchecked!` and `is_empty!` macros as well as the
239 // `post_inc_start` method for more information.
240 unsafe {
241 let end_or_len =
242 if T::IS_ZST { without_provenance_mut(len) } else { ptr.as_ptr().add(len) };
243
244 Self { ptr, end_or_len, _marker: PhantomData }
245 }
246 }
247
248 /// Views the underlying data as a subslice of the original data.
249 ///
250 /// To avoid creating `&mut` references that alias, this is forced
251 /// to consume the iterator.
252 ///
253 /// # Examples
254 ///
255 /// Basic usage:
256 ///
257 /// ```
258 /// // First, we need a slice to call the `iter_mut` method on:
259 /// let mut slice = &mut [1, 2, 3];
260 ///
261 /// // Then we call `iter_mut` on the slice to get the `IterMut` struct:
262 /// let mut iter = slice.iter_mut();
263 /// // Now, we call the `next` method to remove the first element of the iterator,
264 /// // unwrap and dereference what we get from `next` and increase its value by 1:
265 /// *iter.next().unwrap() += 1;
266 /// // Here the iterator does not contain the first element of the slice any more,
267 /// // so `into_slice` only returns the last two elements of the slice,
268 /// // and so this prints "[2, 3]":
269 /// println!("{:?}", iter.into_slice());
270 /// // The underlying slice still contains three elements, but its first element
271 /// // was increased by 1, so this prints "[2, 2, 3]":
272 /// println!("{:?}", slice);
273 /// ```
274 #[must_use = "`self` will be dropped if the result is not used"]
275 #[stable(feature = "iter_to_slice", since = "1.4.0")]
276 pub fn into_slice(self) -> &'a mut [T] {
277 // SAFETY: the iterator was created from a mutable slice with pointer
278 // `self.ptr` and length `len!(self)`. This guarantees that all the prerequisites
279 // for `from_raw_parts_mut` are fulfilled.
280 unsafe { from_raw_parts_mut(self.ptr.as_ptr(), len!(self)) }
281 }
282
283 /// Views the underlying data as a subslice of the original data.
284 ///
285 /// # Examples
286 ///
287 /// Basic usage:
288 ///
289 /// ```
290 /// // First, we need a slice to call the `iter_mut` method on:
291 /// let slice = &mut [1, 2, 3];
292 ///
293 /// // Then we call `iter_mut` on the slice to get the `IterMut` iterator:
294 /// let mut iter = slice.iter_mut();
295 /// // Here `as_slice` still returns the whole slice, so this prints "[1, 2, 3]":
296 /// println!("{:?}", iter.as_slice());
297 ///
298 /// // Now, we call the `next` method to remove the first element from the iterator
299 /// // and increment its value:
300 /// *iter.next().unwrap() += 1;
301 /// // Here the iterator does not contain the first element of the slice any more,
302 /// // so `as_slice` only returns the last two elements of the slice,
303 /// // and so this prints "[2, 3]":
304 /// println!("{:?}", iter.as_slice());
305 ///
306 /// // The underlying slice still contains three elements, but its first element
307 /// // was increased by 1, so this prints "[2, 2, 3]":
308 /// println!("{:?}", slice);
309 /// ```
310 #[must_use]
311 #[stable(feature = "slice_iter_mut_as_slice", since = "1.53.0")]
312 #[inline]
313 pub fn as_slice(&self) -> &[T] {
314 self.make_slice()
315 }
316
317 /// Views the underlying data as a mutable subslice of the original data.
318 ///
319 /// # Examples
320 ///
321 /// Basic usage:
322 ///
323 /// ```
324 /// #![feature(slice_iter_mut_as_mut_slice)]
325 ///
326 /// let mut slice: &mut [usize] = &mut [1, 2, 3];
327 ///
328 /// // First, we get the iterator:
329 /// let mut iter = slice.iter_mut();
330 /// // Then, we get a mutable slice from it:
331 /// let mut_slice = iter.as_mut_slice();
332 /// // So if we check what the `as_mut_slice` method returned, we have "[1, 2, 3]":
333 /// assert_eq!(mut_slice, &mut [1, 2, 3]);
334 ///
335 /// // We can use it to mutate the slice:
336 /// mut_slice[0] = 4;
337 /// mut_slice[2] = 5;
338 ///
339 /// // Next, we can move to the second element of the slice, checking that
340 /// // it yields the value we just wrote:
341 /// assert_eq!(iter.next(), Some(&mut 4));
342 /// // Now `as_mut_slice` returns "[2, 5]":
343 /// assert_eq!(iter.as_mut_slice(), &mut [2, 5]);
344 /// ```
345 #[must_use]
346 // FIXME: Uncomment the `AsMut<[T]>` impl when this gets stabilized.
347 #[unstable(feature = "slice_iter_mut_as_mut_slice", issue = "93079")]
348 pub fn as_mut_slice(&mut self) -> &mut [T] {
349 // SAFETY: the iterator was created from a mutable slice with pointer
350 // `self.ptr` and length `len!(self)`. This guarantees that all the prerequisites
351 // for `from_raw_parts_mut` are fulfilled.
352 unsafe { from_raw_parts_mut(self.ptr.as_ptr(), len!(self)) }
353 }
354}
355
356#[stable(feature = "slice_iter_mut_as_slice", since = "1.53.0")]
357impl<T> AsRef<[T]> for IterMut<'_, T> {
358 #[inline]
359 fn as_ref(&self) -> &[T] {
360 self.as_slice()
361 }
362}
363
364// #[stable(feature = "slice_iter_mut_as_mut_slice", since = "FIXME")]
365// impl<T> AsMut<[T]> for IterMut<'_, T> {
366// fn as_mut(&mut self) -> &mut [T] {
367// self.as_mut_slice()
368// }
369// }
370
371iterator! {struct IterMut -> *mut T, &'a mut T, mut, {mut}, as_mut, {}}
372
373/// An internal abstraction over the splitting iterators, so that
374/// splitn, splitn_mut etc can be implemented once.
375#[doc(hidden)]
376pub(super) trait SplitIter: DoubleEndedIterator {
377 /// Marks the underlying iterator as complete, extracting the remaining
378 /// portion of the slice.
379 fn finish(&mut self) -> Option<Self::Item>;
380}
381
382/// An iterator over subslices separated by elements that match a predicate
383/// function.
384///
385/// This struct is created by the [`split`] method on [slices].
386///
387/// # Example
388///
389/// ```
390/// let slice = [10, 40, 33, 20];
391/// let mut iter = slice.split(|num| num % 3 == 0);
392/// assert_eq!(iter.next(), Some(&[10, 40][..]));
393/// assert_eq!(iter.next(), Some(&[20][..]));
394/// assert_eq!(iter.next(), None);
395/// ```
396///
397/// [`split`]: slice::split
398/// [slices]: slice
399#[stable(feature = "rust1", since = "1.0.0")]
400#[must_use = "iterators are lazy and do nothing unless consumed"]
401pub struct Split<'a, T: 'a, P>
402where
403 P: FnMut(&T) -> bool,
404{
405 // Used for `SplitWhitespace` and `SplitAsciiWhitespace` `as_str` methods
406 pub(crate) v: &'a [T],
407 pred: P,
408 // Used for `SplitAsciiWhitespace` `as_str` method
409 pub(crate) finished: bool,
410}
411
412impl<'a, T: 'a, P: FnMut(&T) -> bool> Split<'a, T, P> {
413 #[inline]
414 pub(super) fn new(slice: &'a [T], pred: P) -> Self {
415 Self { v: slice, pred, finished: false }
416 }
417 /// Returns a slice which contains items not yet handled by split.
418 /// # Example
419 ///
420 /// ```
421 /// #![feature(split_as_slice)]
422 /// let slice = [1,2,3,4,5];
423 /// let mut split = slice.split(|v| v % 2 == 0);
424 /// assert!(split.next().is_some());
425 /// assert_eq!(split.as_slice(), &[3,4,5]);
426 /// ```
427 #[unstable(feature = "split_as_slice", issue = "96137")]
428 pub fn as_slice(&self) -> &'a [T] {
429 if self.finished { &[] } else { &self.v }
430 }
431}
432
433#[stable(feature = "core_impl_debug", since = "1.9.0")]
434impl<T: fmt::Debug, P> fmt::Debug for Split<'_, T, P>
435where
436 P: FnMut(&T) -> bool,
437{
438 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
439 f.debug_struct("Split").field("v", &self.v).field("finished", &self.finished).finish()
440 }
441}
442
443// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
444#[stable(feature = "rust1", since = "1.0.0")]
445impl<T, P> Clone for Split<'_, T, P>
446where
447 P: Clone + FnMut(&T) -> bool,
448{
449 fn clone(&self) -> Self {
450 Split { v: self.v, pred: self.pred.clone(), finished: self.finished }
451 }
452}
453
454#[stable(feature = "rust1", since = "1.0.0")]
455impl<'a, T, P> Iterator for Split<'a, T, P>
456where
457 P: FnMut(&T) -> bool,
458{
459 type Item = &'a [T];
460
461 #[inline]
462 fn next(&mut self) -> Option<&'a [T]> {
463 if self.finished {
464 return None;
465 }
466
467 match self.v.iter().position(|x| (self.pred)(x)) {
468 None => self.finish(),
469 Some(idx) => {
470 let (left, right) =
471 // SAFETY: if v.iter().position returns Some(idx), that
472 // idx is definitely a valid index for v
473 unsafe { (self.v.get_unchecked(..idx), self.v.get_unchecked(idx + 1..)) };
474 let ret = Some(left);
475 self.v = right;
476 ret
477 }
478 }
479 }
480
481 #[inline]
482 fn size_hint(&self) -> (usize, Option<usize>) {
483 if self.finished {
484 (0, Some(0))
485 } else {
486 // If the predicate doesn't match anything, we yield one slice.
487 // If it matches every element, we yield `len() + 1` empty slices.
488 (1, Some(self.v.len() + 1))
489 }
490 }
491}
492
493#[stable(feature = "rust1", since = "1.0.0")]
494impl<'a, T, P> DoubleEndedIterator for Split<'a, T, P>
495where
496 P: FnMut(&T) -> bool,
497{
498 #[inline]
499 fn next_back(&mut self) -> Option<&'a [T]> {
500 if self.finished {
501 return None;
502 }
503
504 match self.v.iter().rposition(|x| (self.pred)(x)) {
505 None => self.finish(),
506 Some(idx) => {
507 let (left, right) =
508 // SAFETY: if v.iter().rposition returns Some(idx), then
509 // idx is definitely a valid index for v
510 unsafe { (self.v.get_unchecked(..idx), self.v.get_unchecked(idx + 1..)) };
511 let ret = Some(right);
512 self.v = left;
513 ret
514 }
515 }
516 }
517}
518
519impl<'a, T, P> SplitIter for Split<'a, T, P>
520where
521 P: FnMut(&T) -> bool,
522{
523 #[inline]
524 fn finish(&mut self) -> Option<&'a [T]> {
525 if self.finished {
526 None
527 } else {
528 self.finished = true;
529 Some(self.v)
530 }
531 }
532}
533
534#[stable(feature = "fused", since = "1.26.0")]
535impl<T, P> FusedIterator for Split<'_, T, P> where P: FnMut(&T) -> bool {}
536
537/// An iterator over subslices separated by elements that match a predicate
538/// function. Unlike `Split`, it contains the matched part as a terminator
539/// of the subslice.
540///
541/// This struct is created by the [`split_inclusive`] method on [slices].
542///
543/// # Example
544///
545/// ```
546/// let slice = [10, 40, 33, 20];
547/// let mut iter = slice.split_inclusive(|num| num % 3 == 0);
548/// assert_eq!(iter.next(), Some(&[10, 40, 33][..]));
549/// assert_eq!(iter.next(), Some(&[20][..]));
550/// assert_eq!(iter.next(), None);
551/// ```
552///
553/// [`split_inclusive`]: slice::split_inclusive
554/// [slices]: slice
555#[stable(feature = "split_inclusive", since = "1.51.0")]
556#[must_use = "iterators are lazy and do nothing unless consumed"]
557pub struct SplitInclusive<'a, T: 'a, P>
558where
559 P: FnMut(&T) -> bool,
560{
561 v: &'a [T],
562 pred: P,
563 finished: bool,
564}
565
566impl<'a, T: 'a, P: FnMut(&T) -> bool> SplitInclusive<'a, T, P> {
567 #[inline]
568 pub(super) fn new(slice: &'a [T], pred: P) -> Self {
569 let finished = slice.is_empty();
570 Self { v: slice, pred, finished }
571 }
572}
573
574#[stable(feature = "split_inclusive", since = "1.51.0")]
575impl<T: fmt::Debug, P> fmt::Debug for SplitInclusive<'_, T, P>
576where
577 P: FnMut(&T) -> bool,
578{
579 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
580 f.debug_struct("SplitInclusive")
581 .field("v", &self.v)
582 .field("finished", &self.finished)
583 .finish()
584 }
585}
586
587// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
588#[stable(feature = "split_inclusive", since = "1.51.0")]
589impl<T, P> Clone for SplitInclusive<'_, T, P>
590where
591 P: Clone + FnMut(&T) -> bool,
592{
593 fn clone(&self) -> Self {
594 SplitInclusive { v: self.v, pred: self.pred.clone(), finished: self.finished }
595 }
596}
597
598#[stable(feature = "split_inclusive", since = "1.51.0")]
599impl<'a, T, P> Iterator for SplitInclusive<'a, T, P>
600where
601 P: FnMut(&T) -> bool,
602{
603 type Item = &'a [T];
604
605 #[inline]
606 fn next(&mut self) -> Option<&'a [T]> {
607 if self.finished {
608 return None;
609 }
610
611 let idx =
612 self.v.iter().position(|x| (self.pred)(x)).map(|idx| idx + 1).unwrap_or(self.v.len());
613 if idx == self.v.len() {
614 self.finished = true;
615 }
616 let ret = Some(&self.v[..idx]);
617 self.v = &self.v[idx..];
618 ret
619 }
620
621 #[inline]
622 fn size_hint(&self) -> (usize, Option<usize>) {
623 if self.finished {
624 (0, Some(0))
625 } else {
626 // If the predicate doesn't match anything, we yield one slice.
627 // If it matches every element, we yield `len()` one-element slices,
628 // or a single empty slice.
629 (1, Some(cmp::max(1, self.v.len())))
630 }
631 }
632}
633
634#[stable(feature = "split_inclusive", since = "1.51.0")]
635impl<'a, T, P> DoubleEndedIterator for SplitInclusive<'a, T, P>
636where
637 P: FnMut(&T) -> bool,
638{
639 #[inline]
640 fn next_back(&mut self) -> Option<&'a [T]> {
641 if self.finished {
642 return None;
643 }
644
645 // The last index of self.v is already checked and found to match
646 // by the last iteration, so we start searching a new match
647 // one index to the left.
648 let remainder = if self.v.is_empty() { &[] } else { &self.v[..(self.v.len() - 1)] };
649 let idx = remainder.iter().rposition(|x| (self.pred)(x)).map(|idx| idx + 1).unwrap_or(0);
650 if idx == 0 {
651 self.finished = true;
652 }
653 let ret = Some(&self.v[idx..]);
654 self.v = &self.v[..idx];
655 ret
656 }
657}
658
659#[stable(feature = "split_inclusive", since = "1.51.0")]
660impl<T, P> FusedIterator for SplitInclusive<'_, T, P> where P: FnMut(&T) -> bool {}
661
662/// An iterator over the mutable subslices of the vector which are separated
663/// by elements that match `pred`.
664///
665/// This struct is created by the [`split_mut`] method on [slices].
666///
667/// # Example
668///
669/// ```
670/// let mut v = [10, 40, 30, 20, 60, 50];
671/// let iter = v.split_mut(|num| *num % 3 == 0);
672/// ```
673///
674/// [`split_mut`]: slice::split_mut
675/// [slices]: slice
676#[stable(feature = "rust1", since = "1.0.0")]
677#[must_use = "iterators are lazy and do nothing unless consumed"]
678pub struct SplitMut<'a, T: 'a, P>
679where
680 P: FnMut(&T) -> bool,
681{
682 v: &'a mut [T],
683 pred: P,
684 finished: bool,
685}
686
687impl<'a, T: 'a, P: FnMut(&T) -> bool> SplitMut<'a, T, P> {
688 #[inline]
689 pub(super) fn new(slice: &'a mut [T], pred: P) -> Self {
690 Self { v: slice, pred, finished: false }
691 }
692}
693
694#[stable(feature = "core_impl_debug", since = "1.9.0")]
695impl<T: fmt::Debug, P> fmt::Debug for SplitMut<'_, T, P>
696where
697 P: FnMut(&T) -> bool,
698{
699 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
700 f.debug_struct("SplitMut").field("v", &self.v).field("finished", &self.finished).finish()
701 }
702}
703
704impl<'a, T, P> SplitIter for SplitMut<'a, T, P>
705where
706 P: FnMut(&T) -> bool,
707{
708 #[inline]
709 fn finish(&mut self) -> Option<&'a mut [T]> {
710 if self.finished {
711 None
712 } else {
713 self.finished = true;
714 Some(mem::take(&mut self.v))
715 }
716 }
717}
718
719#[stable(feature = "rust1", since = "1.0.0")]
720impl<'a, T, P> Iterator for SplitMut<'a, T, P>
721where
722 P: FnMut(&T) -> bool,
723{
724 type Item = &'a mut [T];
725
726 #[inline]
727 fn next(&mut self) -> Option<&'a mut [T]> {
728 if self.finished {
729 return None;
730 }
731
732 match self.v.iter().position(|x| (self.pred)(x)) {
733 None => self.finish(),
734 Some(idx) => {
735 let tmp = mem::take(&mut self.v);
736 // idx is the index of the element we are splitting on. We want to set self to the
737 // region after idx, and return the subslice before and not including idx.
738 // So first we split after idx
739 let (head, tail) = tmp.split_at_mut(idx + 1);
740 self.v = tail;
741 // Then return the subslice up to but not including the found element
742 Some(&mut head[..idx])
743 }
744 }
745 }
746
747 #[inline]
748 fn size_hint(&self) -> (usize, Option<usize>) {
749 if self.finished {
750 (0, Some(0))
751 } else {
752 // If the predicate doesn't match anything, we yield one slice.
753 // If it matches every element, we yield `len() + 1` empty slices.
754 (1, Some(self.v.len() + 1))
755 }
756 }
757}
758
759#[stable(feature = "rust1", since = "1.0.0")]
760impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P>
761where
762 P: FnMut(&T) -> bool,
763{
764 #[inline]
765 fn next_back(&mut self) -> Option<&'a mut [T]> {
766 if self.finished {
767 return None;
768 }
769
770 let idx_opt = {
771 // work around borrowck limitations
772 let pred = &mut self.pred;
773 self.v.iter().rposition(|x| (*pred)(x))
774 };
775 match idx_opt {
776 None => self.finish(),
777 Some(idx) => {
778 let tmp = mem::take(&mut self.v);
779 let (head, tail) = tmp.split_at_mut(idx);
780 self.v = head;
781 Some(&mut tail[1..])
782 }
783 }
784 }
785}
786
787#[stable(feature = "fused", since = "1.26.0")]
788impl<T, P> FusedIterator for SplitMut<'_, T, P> where P: FnMut(&T) -> bool {}
789
790/// An iterator over the mutable subslices of the vector which are separated
791/// by elements that match `pred`. Unlike `SplitMut`, it contains the matched
792/// parts in the ends of the subslices.
793///
794/// This struct is created by the [`split_inclusive_mut`] method on [slices].
795///
796/// # Example
797///
798/// ```
799/// let mut v = [10, 40, 30, 20, 60, 50];
800/// let iter = v.split_inclusive_mut(|num| *num % 3 == 0);
801/// ```
802///
803/// [`split_inclusive_mut`]: slice::split_inclusive_mut
804/// [slices]: slice
805#[stable(feature = "split_inclusive", since = "1.51.0")]
806#[must_use = "iterators are lazy and do nothing unless consumed"]
807pub struct SplitInclusiveMut<'a, T: 'a, P>
808where
809 P: FnMut(&T) -> bool,
810{
811 v: &'a mut [T],
812 pred: P,
813 finished: bool,
814}
815
816impl<'a, T: 'a, P: FnMut(&T) -> bool> SplitInclusiveMut<'a, T, P> {
817 #[inline]
818 pub(super) fn new(slice: &'a mut [T], pred: P) -> Self {
819 let finished = slice.is_empty();
820 Self { v: slice, pred, finished }
821 }
822}
823
824#[stable(feature = "split_inclusive", since = "1.51.0")]
825impl<T: fmt::Debug, P> fmt::Debug for SplitInclusiveMut<'_, T, P>
826where
827 P: FnMut(&T) -> bool,
828{
829 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
830 f.debug_struct("SplitInclusiveMut")
831 .field("v", &self.v)
832 .field("finished", &self.finished)
833 .finish()
834 }
835}
836
837#[stable(feature = "split_inclusive", since = "1.51.0")]
838impl<'a, T, P> Iterator for SplitInclusiveMut<'a, T, P>
839where
840 P: FnMut(&T) -> bool,
841{
842 type Item = &'a mut [T];
843
844 #[inline]
845 fn next(&mut self) -> Option<&'a mut [T]> {
846 if self.finished {
847 return None;
848 }
849
850 let idx_opt = {
851 // work around borrowck limitations
852 let pred = &mut self.pred;
853 self.v.iter().position(|x| (*pred)(x))
854 };
855 let idx = idx_opt.map(|idx| idx + 1).unwrap_or(self.v.len());
856 if idx == self.v.len() {
857 self.finished = true;
858 }
859 let tmp = mem::take(&mut self.v);
860 let (head, tail) = tmp.split_at_mut(idx);
861 self.v = tail;
862 Some(head)
863 }
864
865 #[inline]
866 fn size_hint(&self) -> (usize, Option<usize>) {
867 if self.finished {
868 (0, Some(0))
869 } else {
870 // If the predicate doesn't match anything, we yield one slice.
871 // If it matches every element, we yield `len()` one-element slices,
872 // or a single empty slice.
873 (1, Some(cmp::max(1, self.v.len())))
874 }
875 }
876}
877
878#[stable(feature = "split_inclusive", since = "1.51.0")]
879impl<'a, T, P> DoubleEndedIterator for SplitInclusiveMut<'a, T, P>
880where
881 P: FnMut(&T) -> bool,
882{
883 #[inline]
884 fn next_back(&mut self) -> Option<&'a mut [T]> {
885 if self.finished {
886 return None;
887 }
888
889 let idx_opt = if self.v.is_empty() {
890 None
891 } else {
892 // work around borrowck limitations
893 let pred = &mut self.pred;
894
895 // The last index of self.v is already checked and found to match
896 // by the last iteration, so we start searching a new match
897 // one index to the left.
898 let remainder = &self.v[..(self.v.len() - 1)];
899 remainder.iter().rposition(|x| (*pred)(x))
900 };
901 let idx = idx_opt.map(|idx| idx + 1).unwrap_or(0);
902 if idx == 0 {
903 self.finished = true;
904 }
905 let tmp = mem::take(&mut self.v);
906 let (head, tail) = tmp.split_at_mut(idx);
907 self.v = head;
908 Some(tail)
909 }
910}
911
912#[stable(feature = "split_inclusive", since = "1.51.0")]
913impl<T, P> FusedIterator for SplitInclusiveMut<'_, T, P> where P: FnMut(&T) -> bool {}
914
915/// An iterator over subslices separated by elements that match a predicate
916/// function, starting from the end of the slice.
917///
918/// This struct is created by the [`rsplit`] method on [slices].
919///
920/// # Example
921///
922/// ```
923/// let slice = [11, 22, 33, 0, 44, 55];
924/// let mut iter = slice.rsplit(|num| *num == 0);
925/// assert_eq!(iter.next(), Some(&[44, 55][..]));
926/// assert_eq!(iter.next(), Some(&[11, 22, 33][..]));
927/// assert_eq!(iter.next(), None);
928/// ```
929///
930/// [`rsplit`]: slice::rsplit
931/// [slices]: slice
932#[stable(feature = "slice_rsplit", since = "1.27.0")]
933#[must_use = "iterators are lazy and do nothing unless consumed"]
934pub struct RSplit<'a, T: 'a, P>
935where
936 P: FnMut(&T) -> bool,
937{
938 inner: Split<'a, T, P>,
939}
940
941impl<'a, T: 'a, P: FnMut(&T) -> bool> RSplit<'a, T, P> {
942 #[inline]
943 pub(super) fn new(slice: &'a [T], pred: P) -> Self {
944 Self { inner: Split::new(slice, pred) }
945 }
946}
947
948#[stable(feature = "slice_rsplit", since = "1.27.0")]
949impl<T: fmt::Debug, P> fmt::Debug for RSplit<'_, T, P>
950where
951 P: FnMut(&T) -> bool,
952{
953 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
954 f.debug_struct("RSplit")
955 .field("v", &self.inner.v)
956 .field("finished", &self.inner.finished)
957 .finish()
958 }
959}
960
961// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
962#[stable(feature = "slice_rsplit", since = "1.27.0")]
963impl<T, P> Clone for RSplit<'_, T, P>
964where
965 P: Clone + FnMut(&T) -> bool,
966{
967 fn clone(&self) -> Self {
968 RSplit { inner: self.inner.clone() }
969 }
970}
971
972#[stable(feature = "slice_rsplit", since = "1.27.0")]
973impl<'a, T, P> Iterator for RSplit<'a, T, P>
974where
975 P: FnMut(&T) -> bool,
976{
977 type Item = &'a [T];
978
979 #[inline]
980 fn next(&mut self) -> Option<&'a [T]> {
981 self.inner.next_back()
982 }
983
984 #[inline]
985 fn size_hint(&self) -> (usize, Option<usize>) {
986 self.inner.size_hint()
987 }
988}
989
990#[stable(feature = "slice_rsplit", since = "1.27.0")]
991impl<'a, T, P> DoubleEndedIterator for RSplit<'a, T, P>
992where
993 P: FnMut(&T) -> bool,
994{
995 #[inline]
996 fn next_back(&mut self) -> Option<&'a [T]> {
997 self.inner.next()
998 }
999}
1000
1001#[stable(feature = "slice_rsplit", since = "1.27.0")]
1002impl<'a, T, P> SplitIter for RSplit<'a, T, P>
1003where
1004 P: FnMut(&T) -> bool,
1005{
1006 #[inline]
1007 fn finish(&mut self) -> Option<&'a [T]> {
1008 self.inner.finish()
1009 }
1010}
1011
1012#[stable(feature = "slice_rsplit", since = "1.27.0")]
1013impl<T, P> FusedIterator for RSplit<'_, T, P> where P: FnMut(&T) -> bool {}
1014
1015/// An iterator over the subslices of the vector which are separated
1016/// by elements that match `pred`, starting from the end of the slice.
1017///
1018/// This struct is created by the [`rsplit_mut`] method on [slices].
1019///
1020/// # Example
1021///
1022/// ```
1023/// let mut slice = [11, 22, 33, 0, 44, 55];
1024/// let iter = slice.rsplit_mut(|num| *num == 0);
1025/// ```
1026///
1027/// [`rsplit_mut`]: slice::rsplit_mut
1028/// [slices]: slice
1029#[stable(feature = "slice_rsplit", since = "1.27.0")]
1030#[must_use = "iterators are lazy and do nothing unless consumed"]
1031pub struct RSplitMut<'a, T: 'a, P>
1032where
1033 P: FnMut(&T) -> bool,
1034{
1035 inner: SplitMut<'a, T, P>,
1036}
1037
1038impl<'a, T: 'a, P: FnMut(&T) -> bool> RSplitMut<'a, T, P> {
1039 #[inline]
1040 pub(super) fn new(slice: &'a mut [T], pred: P) -> Self {
1041 Self { inner: SplitMut::new(slice, pred) }
1042 }
1043}
1044
1045#[stable(feature = "slice_rsplit", since = "1.27.0")]
1046impl<T: fmt::Debug, P> fmt::Debug for RSplitMut<'_, T, P>
1047where
1048 P: FnMut(&T) -> bool,
1049{
1050 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1051 f.debug_struct("RSplitMut")
1052 .field("v", &self.inner.v)
1053 .field("finished", &self.inner.finished)
1054 .finish()
1055 }
1056}
1057
1058#[stable(feature = "slice_rsplit", since = "1.27.0")]
1059impl<'a, T, P> SplitIter for RSplitMut<'a, T, P>
1060where
1061 P: FnMut(&T) -> bool,
1062{
1063 #[inline]
1064 fn finish(&mut self) -> Option<&'a mut [T]> {
1065 self.inner.finish()
1066 }
1067}
1068
1069#[stable(feature = "slice_rsplit", since = "1.27.0")]
1070impl<'a, T, P> Iterator for RSplitMut<'a, T, P>
1071where
1072 P: FnMut(&T) -> bool,
1073{
1074 type Item = &'a mut [T];
1075
1076 #[inline]
1077 fn next(&mut self) -> Option<&'a mut [T]> {
1078 self.inner.next_back()
1079 }
1080
1081 #[inline]
1082 fn size_hint(&self) -> (usize, Option<usize>) {
1083 self.inner.size_hint()
1084 }
1085}
1086
1087#[stable(feature = "slice_rsplit", since = "1.27.0")]
1088impl<'a, T, P> DoubleEndedIterator for RSplitMut<'a, T, P>
1089where
1090 P: FnMut(&T) -> bool,
1091{
1092 #[inline]
1093 fn next_back(&mut self) -> Option<&'a mut [T]> {
1094 self.inner.next()
1095 }
1096}
1097
1098#[stable(feature = "slice_rsplit", since = "1.27.0")]
1099impl<T, P> FusedIterator for RSplitMut<'_, T, P> where P: FnMut(&T) -> bool {}
1100
1101/// An private iterator over subslices separated by elements that
1102/// match a predicate function, splitting at most a fixed number of
1103/// times.
1104#[derive(Debug)]
1105struct GenericSplitN<I> {
1106 iter: I,
1107 count: usize,
1108}
1109
1110impl<T, I: SplitIter<Item = T>> Iterator for GenericSplitN<I> {
1111 type Item = T;
1112
1113 #[inline]
1114 fn next(&mut self) -> Option<T> {
1115 match self.count {
1116 0 => None,
1117 1 => {
1118 self.count -= 1;
1119 self.iter.finish()
1120 }
1121 _ => {
1122 self.count -= 1;
1123 self.iter.next()
1124 }
1125 }
1126 }
1127
1128 #[inline]
1129 fn size_hint(&self) -> (usize, Option<usize>) {
1130 let (lower, upper_opt) = self.iter.size_hint();
1131 (
1132 cmp::min(self.count, lower),
1133 Some(upper_opt.map_or(self.count, |upper| cmp::min(self.count, upper))),
1134 )
1135 }
1136}
1137
1138/// An iterator over subslices separated by elements that match a predicate
1139/// function, limited to a given number of splits.
1140///
1141/// This struct is created by the [`splitn`] method on [slices].
1142///
1143/// # Example
1144///
1145/// ```
1146/// let slice = [10, 40, 30, 20, 60, 50];
1147/// let mut iter = slice.splitn(2, |num| *num % 3 == 0);
1148/// assert_eq!(iter.next(), Some(&[10, 40][..]));
1149/// assert_eq!(iter.next(), Some(&[20, 60, 50][..]));
1150/// assert_eq!(iter.next(), None);
1151/// ```
1152///
1153/// [`splitn`]: slice::splitn
1154/// [slices]: slice
1155#[stable(feature = "rust1", since = "1.0.0")]
1156#[must_use = "iterators are lazy and do nothing unless consumed"]
1157pub struct SplitN<'a, T: 'a, P>
1158where
1159 P: FnMut(&T) -> bool,
1160{
1161 inner: GenericSplitN<Split<'a, T, P>>,
1162}
1163
1164impl<'a, T: 'a, P: FnMut(&T) -> bool> SplitN<'a, T, P> {
1165 #[inline]
1166 pub(super) fn new(s: Split<'a, T, P>, n: usize) -> Self {
1167 Self { inner: GenericSplitN { iter: s, count: n } }
1168 }
1169}
1170
1171#[stable(feature = "core_impl_debug", since = "1.9.0")]
1172impl<T: fmt::Debug, P> fmt::Debug for SplitN<'_, T, P>
1173where
1174 P: FnMut(&T) -> bool,
1175{
1176 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1177 f.debug_struct("SplitN").field("inner", &self.inner).finish()
1178 }
1179}
1180
1181/// An iterator over subslices separated by elements that match a
1182/// predicate function, limited to a given number of splits, starting
1183/// from the end of the slice.
1184///
1185/// This struct is created by the [`rsplitn`] method on [slices].
1186///
1187/// # Example
1188///
1189/// ```
1190/// let slice = [10, 40, 30, 20, 60, 50];
1191/// let mut iter = slice.rsplitn(2, |num| *num % 3 == 0);
1192/// assert_eq!(iter.next(), Some(&[50][..]));
1193/// assert_eq!(iter.next(), Some(&[10, 40, 30, 20][..]));
1194/// assert_eq!(iter.next(), None);
1195/// ```
1196///
1197/// [`rsplitn`]: slice::rsplitn
1198/// [slices]: slice
1199#[stable(feature = "rust1", since = "1.0.0")]
1200#[must_use = "iterators are lazy and do nothing unless consumed"]
1201pub struct RSplitN<'a, T: 'a, P>
1202where
1203 P: FnMut(&T) -> bool,
1204{
1205 inner: GenericSplitN<RSplit<'a, T, P>>,
1206}
1207
1208impl<'a, T: 'a, P: FnMut(&T) -> bool> RSplitN<'a, T, P> {
1209 #[inline]
1210 pub(super) fn new(s: RSplit<'a, T, P>, n: usize) -> Self {
1211 Self { inner: GenericSplitN { iter: s, count: n } }
1212 }
1213}
1214
1215#[stable(feature = "core_impl_debug", since = "1.9.0")]
1216impl<T: fmt::Debug, P> fmt::Debug for RSplitN<'_, T, P>
1217where
1218 P: FnMut(&T) -> bool,
1219{
1220 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1221 f.debug_struct("RSplitN").field("inner", &self.inner).finish()
1222 }
1223}
1224
1225/// An iterator over subslices separated by elements that match a predicate
1226/// function, limited to a given number of splits.
1227///
1228/// This struct is created by the [`splitn_mut`] method on [slices].
1229///
1230/// # Example
1231///
1232/// ```
1233/// let mut slice = [10, 40, 30, 20, 60, 50];
1234/// let iter = slice.splitn_mut(2, |num| *num % 3 == 0);
1235/// ```
1236///
1237/// [`splitn_mut`]: slice::splitn_mut
1238/// [slices]: slice
1239#[stable(feature = "rust1", since = "1.0.0")]
1240#[must_use = "iterators are lazy and do nothing unless consumed"]
1241pub struct SplitNMut<'a, T: 'a, P>
1242where
1243 P: FnMut(&T) -> bool,
1244{
1245 inner: GenericSplitN<SplitMut<'a, T, P>>,
1246}
1247
1248impl<'a, T: 'a, P: FnMut(&T) -> bool> SplitNMut<'a, T, P> {
1249 #[inline]
1250 pub(super) fn new(s: SplitMut<'a, T, P>, n: usize) -> Self {
1251 Self { inner: GenericSplitN { iter: s, count: n } }
1252 }
1253}
1254
1255#[stable(feature = "core_impl_debug", since = "1.9.0")]
1256impl<T: fmt::Debug, P> fmt::Debug for SplitNMut<'_, T, P>
1257where
1258 P: FnMut(&T) -> bool,
1259{
1260 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1261 f.debug_struct("SplitNMut").field("inner", &self.inner).finish()
1262 }
1263}
1264
1265/// An iterator over subslices separated by elements that match a
1266/// predicate function, limited to a given number of splits, starting
1267/// from the end of the slice.
1268///
1269/// This struct is created by the [`rsplitn_mut`] method on [slices].
1270///
1271/// # Example
1272///
1273/// ```
1274/// let mut slice = [10, 40, 30, 20, 60, 50];
1275/// let iter = slice.rsplitn_mut(2, |num| *num % 3 == 0);
1276/// ```
1277///
1278/// [`rsplitn_mut`]: slice::rsplitn_mut
1279/// [slices]: slice
1280#[stable(feature = "rust1", since = "1.0.0")]
1281#[must_use = "iterators are lazy and do nothing unless consumed"]
1282pub struct RSplitNMut<'a, T: 'a, P>
1283where
1284 P: FnMut(&T) -> bool,
1285{
1286 inner: GenericSplitN<RSplitMut<'a, T, P>>,
1287}
1288
1289impl<'a, T: 'a, P: FnMut(&T) -> bool> RSplitNMut<'a, T, P> {
1290 #[inline]
1291 pub(super) fn new(s: RSplitMut<'a, T, P>, n: usize) -> Self {
1292 Self { inner: GenericSplitN { iter: s, count: n } }
1293 }
1294}
1295
1296#[stable(feature = "core_impl_debug", since = "1.9.0")]
1297impl<T: fmt::Debug, P> fmt::Debug for RSplitNMut<'_, T, P>
1298where
1299 P: FnMut(&T) -> bool,
1300{
1301 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1302 f.debug_struct("RSplitNMut").field("inner", &self.inner).finish()
1303 }
1304}
1305
1306forward_iterator! { SplitN: T, &'a [T] }
1307forward_iterator! { RSplitN: T, &'a [T] }
1308forward_iterator! { SplitNMut: T, &'a mut [T] }
1309forward_iterator! { RSplitNMut: T, &'a mut [T] }
1310
1311/// An iterator over overlapping subslices of length `size`.
1312///
1313/// This struct is created by the [`windows`] method on [slices].
1314///
1315/// # Example
1316///
1317/// ```
1318/// let slice = ['r', 'u', 's', 't'];
1319/// let mut iter = slice.windows(2);
1320/// assert_eq!(iter.next(), Some(&['r', 'u'][..]));
1321/// assert_eq!(iter.next(), Some(&['u', 's'][..]));
1322/// assert_eq!(iter.next(), Some(&['s', 't'][..]));
1323/// assert_eq!(iter.next(), None);
1324/// ```
1325///
1326/// [`windows`]: slice::windows
1327/// [slices]: slice
1328#[derive(Debug)]
1329#[stable(feature = "rust1", since = "1.0.0")]
1330#[must_use = "iterators are lazy and do nothing unless consumed"]
1331pub struct Windows<'a, T: 'a> {
1332 v: &'a [T],
1333 size: NonZero<usize>,
1334}
1335
1336impl<'a, T: 'a> Windows<'a, T> {
1337 #[inline]
1338 pub(super) const fn new(slice: &'a [T], size: NonZero<usize>) -> Self {
1339 Self { v: slice, size }
1340 }
1341}
1342
1343// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1344#[stable(feature = "rust1", since = "1.0.0")]
1345impl<T> Clone for Windows<'_, T> {
1346 fn clone(&self) -> Self {
1347 Windows { v: self.v, size: self.size }
1348 }
1349}
1350
1351#[stable(feature = "rust1", since = "1.0.0")]
1352impl<'a, T> Iterator for Windows<'a, T> {
1353 type Item = &'a [T];
1354
1355 #[inline]
1356 fn next(&mut self) -> Option<&'a [T]> {
1357 if self.size.get() > self.v.len() {
1358 None
1359 } else {
1360 let ret = Some(&self.v[..self.size.get()]);
1361 self.v = &self.v[1..];
1362 ret
1363 }
1364 }
1365
1366 #[inline]
1367 fn size_hint(&self) -> (usize, Option<usize>) {
1368 if self.size.get() > self.v.len() {
1369 (0, Some(0))
1370 } else {
1371 let size = self.v.len() - self.size.get() + 1;
1372 (size, Some(size))
1373 }
1374 }
1375
1376 #[inline]
1377 fn count(self) -> usize {
1378 self.len()
1379 }
1380
1381 #[inline]
1382 fn nth(&mut self, n: usize) -> Option<Self::Item> {
1383 let size = self.size.get();
1384 if let Some(rest) = self.v.get(n..)
1385 && let Some(nth) = rest.get(..size)
1386 {
1387 self.v = &rest[1..];
1388 Some(nth)
1389 } else {
1390 // setting length to 0 is cheaper than overwriting the pointer when assigning &[]
1391 self.v = &self.v[..0]; // cheaper than &[]
1392 None
1393 }
1394 }
1395
1396 #[inline]
1397 fn last(self) -> Option<Self::Item> {
1398 if self.size.get() > self.v.len() {
1399 None
1400 } else {
1401 let start = self.v.len() - self.size.get();
1402 Some(&self.v[start..])
1403 }
1404 }
1405
1406 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
1407 // SAFETY: since the caller guarantees that `i` is in bounds,
1408 // which means that `i` cannot overflow an `isize`, and the
1409 // slice created by `from_raw_parts` is a subslice of `self.v`
1410 // thus is guaranteed to be valid for the lifetime `'a` of `self.v`.
1411 unsafe { from_raw_parts(self.v.as_ptr().add(idx), self.size.get()) }
1412 }
1413}
1414
1415#[stable(feature = "rust1", since = "1.0.0")]
1416impl<'a, T> DoubleEndedIterator for Windows<'a, T> {
1417 #[inline]
1418 fn next_back(&mut self) -> Option<&'a [T]> {
1419 if self.size.get() > self.v.len() {
1420 None
1421 } else {
1422 let ret = Some(&self.v[self.v.len() - self.size.get()..]);
1423 self.v = &self.v[..self.v.len() - 1];
1424 ret
1425 }
1426 }
1427
1428 #[inline]
1429 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
1430 let (end, overflow) = self.v.len().overflowing_sub(n);
1431 if end < self.size.get() || overflow {
1432 self.v = &self.v[..0]; // cheaper than &[]
1433 None
1434 } else {
1435 let ret = &self.v[end - self.size.get()..end];
1436 self.v = &self.v[..end - 1];
1437 Some(ret)
1438 }
1439 }
1440}
1441
1442#[stable(feature = "rust1", since = "1.0.0")]
1443impl<T> ExactSizeIterator for Windows<'_, T> {}
1444
1445#[unstable(feature = "trusted_len", issue = "37572")]
1446unsafe impl<T> TrustedLen for Windows<'_, T> {}
1447
1448#[stable(feature = "fused", since = "1.26.0")]
1449impl<T> FusedIterator for Windows<'_, T> {}
1450
1451#[doc(hidden)]
1452#[unstable(feature = "trusted_random_access", issue = "none")]
1453unsafe impl<'a, T> TrustedRandomAccess for Windows<'a, T> {}
1454
1455#[doc(hidden)]
1456#[unstable(feature = "trusted_random_access", issue = "none")]
1457unsafe impl<'a, T> TrustedRandomAccessNoCoerce for Windows<'a, T> {
1458 const MAY_HAVE_SIDE_EFFECT: bool = false;
1459}
1460
1461/// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
1462/// time), starting at the beginning of the slice.
1463///
1464/// When the slice len is not evenly divided by the chunk size, the last slice
1465/// of the iteration will be the remainder.
1466///
1467/// This struct is created by the [`chunks`] method on [slices].
1468///
1469/// # Example
1470///
1471/// ```
1472/// let slice = ['l', 'o', 'r', 'e', 'm'];
1473/// let mut iter = slice.chunks(2);
1474/// assert_eq!(iter.next(), Some(&['l', 'o'][..]));
1475/// assert_eq!(iter.next(), Some(&['r', 'e'][..]));
1476/// assert_eq!(iter.next(), Some(&['m'][..]));
1477/// assert_eq!(iter.next(), None);
1478/// ```
1479///
1480/// [`chunks`]: slice::chunks
1481/// [slices]: slice
1482#[derive(Debug)]
1483#[stable(feature = "rust1", since = "1.0.0")]
1484#[must_use = "iterators are lazy and do nothing unless consumed"]
1485pub struct Chunks<'a, T: 'a> {
1486 v: &'a [T],
1487 chunk_size: usize,
1488}
1489
1490impl<'a, T: 'a> Chunks<'a, T> {
1491 #[inline]
1492 pub(super) const fn new(slice: &'a [T], size: usize) -> Self {
1493 Self { v: slice, chunk_size: size }
1494 }
1495}
1496
1497// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1498#[stable(feature = "rust1", since = "1.0.0")]
1499impl<T> Clone for Chunks<'_, T> {
1500 fn clone(&self) -> Self {
1501 Chunks { v: self.v, chunk_size: self.chunk_size }
1502 }
1503}
1504
1505#[stable(feature = "rust1", since = "1.0.0")]
1506impl<'a, T> Iterator for Chunks<'a, T> {
1507 type Item = &'a [T];
1508
1509 #[inline]
1510 fn next(&mut self) -> Option<&'a [T]> {
1511 if self.v.is_empty() {
1512 None
1513 } else {
1514 let chunksz = cmp::min(self.v.len(), self.chunk_size);
1515 let (fst, snd) = self.v.split_at(chunksz);
1516 self.v = snd;
1517 Some(fst)
1518 }
1519 }
1520
1521 #[inline]
1522 fn size_hint(&self) -> (usize, Option<usize>) {
1523 if self.v.is_empty() {
1524 (0, Some(0))
1525 } else {
1526 let n = self.v.len() / self.chunk_size;
1527 let rem = self.v.len() % self.chunk_size;
1528 let n = if rem > 0 { n + 1 } else { n };
1529 (n, Some(n))
1530 }
1531 }
1532
1533 #[inline]
1534 fn count(self) -> usize {
1535 self.len()
1536 }
1537
1538 #[inline]
1539 fn nth(&mut self, n: usize) -> Option<Self::Item> {
1540 let (start, overflow) = n.overflowing_mul(self.chunk_size);
1541 // min(len) makes a wrong start harmless, but enables optimizing this to brachless code
1542 let chunk_start = &self.v[start.min(self.v.len())..];
1543 let (nth, remainder) = chunk_start.split_at(self.chunk_size.min(chunk_start.len()));
1544 if !overflow && start < self.v.len() {
1545 self.v = remainder;
1546 Some(nth)
1547 } else {
1548 self.v = &self.v[..0]; // cheaper than &[]
1549 None
1550 }
1551 }
1552
1553 #[inline]
1554 fn last(self) -> Option<Self::Item> {
1555 if self.v.is_empty() {
1556 None
1557 } else {
1558 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
1559 Some(&self.v[start..])
1560 }
1561 }
1562
1563 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
1564 let start = idx * self.chunk_size;
1565 // SAFETY: the caller guarantees that `i` is in bounds,
1566 // which means that `start` must be in bounds of the
1567 // underlying `self.v` slice, and we made sure that `len`
1568 // is also in bounds of `self.v`. Thus, `start` cannot overflow
1569 // an `isize`, and the slice constructed by `from_raw_parts`
1570 // is a subslice of `self.v` which is guaranteed to be valid
1571 // for the lifetime `'a` of `self.v`.
1572 unsafe {
1573 let len = cmp::min(self.v.len().unchecked_sub(start), self.chunk_size);
1574 from_raw_parts(self.v.as_ptr().add(start), len)
1575 }
1576 }
1577}
1578
1579#[stable(feature = "rust1", since = "1.0.0")]
1580impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
1581 #[inline]
1582 fn next_back(&mut self) -> Option<&'a [T]> {
1583 if self.v.is_empty() {
1584 None
1585 } else {
1586 let remainder = self.v.len() % self.chunk_size;
1587 let chunksz = if remainder != 0 { remainder } else { self.chunk_size };
1588 // SAFETY: split_at_unchecked requires the argument be less than or
1589 // equal to the length. This is guaranteed, but subtle: `chunksz`
1590 // will always either be `self.v.len() % self.chunk_size`, which
1591 // will always evaluate to strictly less than `self.v.len()` (or
1592 // panic, in the case that `self.chunk_size` is zero), or it can be
1593 // `self.chunk_size`, in the case that the length is exactly
1594 // divisible by the chunk size.
1595 //
1596 // While it seems like using `self.chunk_size` in this case could
1597 // lead to a value greater than `self.v.len()`, it cannot: if
1598 // `self.chunk_size` were greater than `self.v.len()`, then
1599 // `self.v.len() % self.chunk_size` would return nonzero (note that
1600 // in this branch of the `if`, we already know that `self.v` is
1601 // non-empty).
1602 let (fst, snd) = unsafe { self.v.split_at_unchecked(self.v.len() - chunksz) };
1603 self.v = fst;
1604 Some(snd)
1605 }
1606 }
1607
1608 #[inline]
1609 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
1610 let len = self.len();
1611 if n >= len {
1612 self.v = &self.v[..0]; // cheaper than &[]
1613 None
1614 } else {
1615 let start = (len - 1 - n) * self.chunk_size;
1616 let end = match start.checked_add(self.chunk_size) {
1617 Some(res) => cmp::min(self.v.len(), res),
1618 None => self.v.len(),
1619 };
1620 let nth_back = &self.v[start..end];
1621 self.v = &self.v[..start];
1622 Some(nth_back)
1623 }
1624 }
1625}
1626
1627#[stable(feature = "rust1", since = "1.0.0")]
1628impl<T> ExactSizeIterator for Chunks<'_, T> {}
1629
1630#[unstable(feature = "trusted_len", issue = "37572")]
1631unsafe impl<T> TrustedLen for Chunks<'_, T> {}
1632
1633#[stable(feature = "fused", since = "1.26.0")]
1634impl<T> FusedIterator for Chunks<'_, T> {}
1635
1636#[doc(hidden)]
1637#[unstable(feature = "trusted_random_access", issue = "none")]
1638unsafe impl<'a, T> TrustedRandomAccess for Chunks<'a, T> {}
1639
1640#[doc(hidden)]
1641#[unstable(feature = "trusted_random_access", issue = "none")]
1642unsafe impl<'a, T> TrustedRandomAccessNoCoerce for Chunks<'a, T> {
1643 const MAY_HAVE_SIDE_EFFECT: bool = false;
1644}
1645
1646/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
1647/// elements at a time), starting at the beginning of the slice.
1648///
1649/// When the slice len is not evenly divided by the chunk size, the last slice
1650/// of the iteration will be the remainder.
1651///
1652/// This struct is created by the [`chunks_mut`] method on [slices].
1653///
1654/// # Example
1655///
1656/// ```
1657/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
1658/// let iter = slice.chunks_mut(2);
1659/// ```
1660///
1661/// [`chunks_mut`]: slice::chunks_mut
1662/// [slices]: slice
1663#[derive(Debug)]
1664#[stable(feature = "rust1", since = "1.0.0")]
1665#[must_use = "iterators are lazy and do nothing unless consumed"]
1666pub struct ChunksMut<'a, T: 'a> {
1667 /// # Safety
1668 /// This slice pointer must point at a valid region of `T` with at least length `v.len()`. Normally,
1669 /// those requirements would mean that we could instead use a `&mut [T]` here, but we cannot
1670 /// because `__iterator_get_unchecked` needs to return `&mut [T]`, which guarantees certain aliasing
1671 /// properties that we cannot uphold if we hold on to the full original `&mut [T]`. Wrapping a raw
1672 /// slice instead lets us hand out non-overlapping `&mut [T]` subslices of the slice we wrap.
1673 v: *mut [T],
1674 chunk_size: usize,
1675 _marker: PhantomData<&'a mut T>,
1676}
1677
1678impl<'a, T: 'a> ChunksMut<'a, T> {
1679 #[inline]
1680 pub(super) const fn new(slice: &'a mut [T], size: usize) -> Self {
1681 Self { v: slice, chunk_size: size, _marker: PhantomData }
1682 }
1683}
1684
1685#[stable(feature = "rust1", since = "1.0.0")]
1686impl<'a, T> Iterator for ChunksMut<'a, T> {
1687 type Item = &'a mut [T];
1688
1689 #[inline]
1690 fn next(&mut self) -> Option<&'a mut [T]> {
1691 if self.v.is_empty() {
1692 None
1693 } else {
1694 let sz = cmp::min(self.v.len(), self.chunk_size);
1695 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
1696 let (head, tail) = unsafe { self.v.split_at_mut(sz) };
1697 self.v = tail;
1698 // SAFETY: Nothing else points to or will point to the contents of this slice.
1699 Some(unsafe { &mut *head })
1700 }
1701 }
1702
1703 #[inline]
1704 fn size_hint(&self) -> (usize, Option<usize>) {
1705 if self.v.is_empty() {
1706 (0, Some(0))
1707 } else {
1708 let n = self.v.len() / self.chunk_size;
1709 let rem = self.v.len() % self.chunk_size;
1710 let n = if rem > 0 { n + 1 } else { n };
1711 (n, Some(n))
1712 }
1713 }
1714
1715 #[inline]
1716 fn count(self) -> usize {
1717 self.len()
1718 }
1719
1720 #[inline]
1721 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
1722 let (start, overflow) = n.overflowing_mul(self.chunk_size);
1723 if start >= self.v.len() || overflow {
1724 self.v = &mut [];
1725 None
1726 } else {
1727 let end = match start.checked_add(self.chunk_size) {
1728 Some(sum) => cmp::min(self.v.len(), sum),
1729 None => self.v.len(),
1730 };
1731 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
1732 let (head, tail) = unsafe { self.v.split_at_mut(end) };
1733 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
1734 let (_, nth) = unsafe { head.split_at_mut(start) };
1735 self.v = tail;
1736 // SAFETY: Nothing else points to or will point to the contents of this slice.
1737 Some(unsafe { &mut *nth })
1738 }
1739 }
1740
1741 #[inline]
1742 fn last(self) -> Option<Self::Item> {
1743 if self.v.is_empty() {
1744 None
1745 } else {
1746 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
1747 // SAFETY: Nothing else points to or will point to the contents of this slice.
1748 Some(unsafe { &mut *self.v.get_unchecked_mut(start..) })
1749 }
1750 }
1751
1752 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
1753 let start = idx * self.chunk_size;
1754 // SAFETY: see comments for `Chunks::__iterator_get_unchecked` and `self.v`.
1755 //
1756 // Also note that the caller also guarantees that we're never called
1757 // with the same index again, and that no other methods that will
1758 // access this subslice are called, so it is valid for the returned
1759 // slice to be mutable.
1760 unsafe {
1761 let len = cmp::min(self.v.len().unchecked_sub(start), self.chunk_size);
1762 from_raw_parts_mut(self.v.as_mut_ptr().add(start), len)
1763 }
1764 }
1765}
1766
1767#[stable(feature = "rust1", since = "1.0.0")]
1768impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
1769 #[inline]
1770 fn next_back(&mut self) -> Option<&'a mut [T]> {
1771 if self.v.is_empty() {
1772 None
1773 } else {
1774 let remainder = self.v.len() % self.chunk_size;
1775 let sz = if remainder != 0 { remainder } else { self.chunk_size };
1776 let len = self.v.len();
1777 // SAFETY: Similar to `Chunks::next_back`
1778 let (head, tail) = unsafe { self.v.split_at_mut_unchecked(len - sz) };
1779 self.v = head;
1780 // SAFETY: Nothing else points to or will point to the contents of this slice.
1781 Some(unsafe { &mut *tail })
1782 }
1783 }
1784
1785 #[inline]
1786 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
1787 let len = self.len();
1788 if n >= len {
1789 self.v = &mut [];
1790 None
1791 } else {
1792 let start = (len - 1 - n) * self.chunk_size;
1793 let end = match start.checked_add(self.chunk_size) {
1794 Some(res) => cmp::min(self.v.len(), res),
1795 None => self.v.len(),
1796 };
1797 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
1798 let (temp, _tail) = unsafe { self.v.split_at_mut(end) };
1799 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
1800 let (head, nth_back) = unsafe { temp.split_at_mut(start) };
1801 self.v = head;
1802 // SAFETY: Nothing else points to or will point to the contents of this slice.
1803 Some(unsafe { &mut *nth_back })
1804 }
1805 }
1806}
1807
1808#[stable(feature = "rust1", since = "1.0.0")]
1809impl<T> ExactSizeIterator for ChunksMut<'_, T> {}
1810
1811#[unstable(feature = "trusted_len", issue = "37572")]
1812unsafe impl<T> TrustedLen for ChunksMut<'_, T> {}
1813
1814#[stable(feature = "fused", since = "1.26.0")]
1815impl<T> FusedIterator for ChunksMut<'_, T> {}
1816
1817#[doc(hidden)]
1818#[unstable(feature = "trusted_random_access", issue = "none")]
1819unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> {}
1820
1821#[doc(hidden)]
1822#[unstable(feature = "trusted_random_access", issue = "none")]
1823unsafe impl<'a, T> TrustedRandomAccessNoCoerce for ChunksMut<'a, T> {
1824 const MAY_HAVE_SIDE_EFFECT: bool = false;
1825}
1826
1827#[stable(feature = "rust1", since = "1.0.0")]
1828unsafe impl<T> Send for ChunksMut<'_, T> where T: Send {}
1829
1830#[stable(feature = "rust1", since = "1.0.0")]
1831unsafe impl<T> Sync for ChunksMut<'_, T> where T: Sync {}
1832
1833/// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
1834/// time), starting at the beginning of the slice.
1835///
1836/// When the slice len is not evenly divided by the chunk size, the last
1837/// up to `chunk_size-1` elements will be omitted but can be retrieved from
1838/// the [`remainder`] function from the iterator.
1839///
1840/// This struct is created by the [`chunks_exact`] method on [slices].
1841///
1842/// # Example
1843///
1844/// ```
1845/// let slice = ['l', 'o', 'r', 'e', 'm'];
1846/// let mut iter = slice.chunks_exact(2);
1847/// assert_eq!(iter.next(), Some(&['l', 'o'][..]));
1848/// assert_eq!(iter.next(), Some(&['r', 'e'][..]));
1849/// assert_eq!(iter.next(), None);
1850/// ```
1851///
1852/// [`chunks_exact`]: slice::chunks_exact
1853/// [`remainder`]: ChunksExact::remainder
1854/// [slices]: slice
1855#[derive(Debug)]
1856#[stable(feature = "chunks_exact", since = "1.31.0")]
1857#[must_use = "iterators are lazy and do nothing unless consumed"]
1858pub struct ChunksExact<'a, T: 'a> {
1859 v: &'a [T],
1860 rem: &'a [T],
1861 chunk_size: usize,
1862}
1863
1864impl<'a, T> ChunksExact<'a, T> {
1865 #[inline]
1866 pub(super) const fn new(slice: &'a [T], chunk_size: usize) -> Self {
1867 let rem = slice.len() % chunk_size;
1868 let fst_len = slice.len() - rem;
1869 // SAFETY: 0 <= fst_len <= slice.len() by construction above
1870 let (fst, snd) = unsafe { slice.split_at_unchecked(fst_len) };
1871 Self { v: fst, rem: snd, chunk_size }
1872 }
1873
1874 /// Returns the remainder of the original slice that is not going to be
1875 /// returned by the iterator. The returned slice has at most `chunk_size-1`
1876 /// elements.
1877 ///
1878 /// # Example
1879 ///
1880 /// ```
1881 /// let slice = ['l', 'o', 'r', 'e', 'm'];
1882 /// let mut iter = slice.chunks_exact(2);
1883 /// assert_eq!(iter.remainder(), &['m'][..]);
1884 /// assert_eq!(iter.next(), Some(&['l', 'o'][..]));
1885 /// assert_eq!(iter.remainder(), &['m'][..]);
1886 /// assert_eq!(iter.next(), Some(&['r', 'e'][..]));
1887 /// assert_eq!(iter.remainder(), &['m'][..]);
1888 /// assert_eq!(iter.next(), None);
1889 /// assert_eq!(iter.remainder(), &['m'][..]);
1890 /// ```
1891 #[must_use]
1892 #[stable(feature = "chunks_exact", since = "1.31.0")]
1893 pub fn remainder(&self) -> &'a [T] {
1894 self.rem
1895 }
1896}
1897
1898// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1899#[stable(feature = "chunks_exact", since = "1.31.0")]
1900impl<T> Clone for ChunksExact<'_, T> {
1901 fn clone(&self) -> Self {
1902 ChunksExact { v: self.v, rem: self.rem, chunk_size: self.chunk_size }
1903 }
1904}
1905
1906#[stable(feature = "chunks_exact", since = "1.31.0")]
1907impl<'a, T> Iterator for ChunksExact<'a, T> {
1908 type Item = &'a [T];
1909
1910 #[inline]
1911 fn next(&mut self) -> Option<&'a [T]> {
1912 if self.v.len() < self.chunk_size {
1913 None
1914 } else {
1915 let (fst, snd) = self.v.split_at(self.chunk_size);
1916 self.v = snd;
1917 Some(fst)
1918 }
1919 }
1920
1921 #[inline]
1922 fn size_hint(&self) -> (usize, Option<usize>) {
1923 let n = self.v.len() / self.chunk_size;
1924 (n, Some(n))
1925 }
1926
1927 #[inline]
1928 fn count(self) -> usize {
1929 self.len()
1930 }
1931
1932 #[inline]
1933 fn nth(&mut self, n: usize) -> Option<Self::Item> {
1934 let (start, overflow) = n.overflowing_mul(self.chunk_size);
1935 if start >= self.v.len() || overflow {
1936 self.v = &self.v[..0]; // cheaper than &[]
1937 None
1938 } else {
1939 let (_, snd) = self.v.split_at(start);
1940 self.v = snd;
1941 self.next()
1942 }
1943 }
1944
1945 #[inline]
1946 fn last(mut self) -> Option<Self::Item> {
1947 self.next_back()
1948 }
1949
1950 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
1951 let start = idx * self.chunk_size;
1952 // SAFETY: mostly identical to `Chunks::__iterator_get_unchecked`.
1953 unsafe { from_raw_parts(self.v.as_ptr().add(start), self.chunk_size) }
1954 }
1955}
1956
1957#[stable(feature = "chunks_exact", since = "1.31.0")]
1958impl<'a, T> DoubleEndedIterator for ChunksExact<'a, T> {
1959 #[inline]
1960 fn next_back(&mut self) -> Option<&'a [T]> {
1961 if self.v.len() < self.chunk_size {
1962 None
1963 } else {
1964 let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size);
1965 self.v = fst;
1966 Some(snd)
1967 }
1968 }
1969
1970 #[inline]
1971 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
1972 let len = self.len();
1973 if n >= len {
1974 self.v = &self.v[..0]; // cheaper than &[]
1975 None
1976 } else {
1977 let start = (len - 1 - n) * self.chunk_size;
1978 let end = start + self.chunk_size;
1979 let nth_back = &self.v[start..end];
1980 self.v = &self.v[..start];
1981 Some(nth_back)
1982 }
1983 }
1984}
1985
1986#[stable(feature = "chunks_exact", since = "1.31.0")]
1987impl<T> ExactSizeIterator for ChunksExact<'_, T> {
1988 fn is_empty(&self) -> bool {
1989 self.v.is_empty()
1990 }
1991}
1992
1993#[unstable(feature = "trusted_len", issue = "37572")]
1994unsafe impl<T> TrustedLen for ChunksExact<'_, T> {}
1995
1996#[stable(feature = "chunks_exact", since = "1.31.0")]
1997impl<T> FusedIterator for ChunksExact<'_, T> {}
1998
1999#[doc(hidden)]
2000#[unstable(feature = "trusted_random_access", issue = "none")]
2001unsafe impl<'a, T> TrustedRandomAccess for ChunksExact<'a, T> {}
2002
2003#[doc(hidden)]
2004#[unstable(feature = "trusted_random_access", issue = "none")]
2005unsafe impl<'a, T> TrustedRandomAccessNoCoerce for ChunksExact<'a, T> {
2006 const MAY_HAVE_SIDE_EFFECT: bool = false;
2007}
2008
2009/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
2010/// elements at a time), starting at the beginning of the slice.
2011///
2012/// When the slice len is not evenly divided by the chunk size, the last up to
2013/// `chunk_size-1` elements will be omitted but can be retrieved from the
2014/// [`into_remainder`] function from the iterator.
2015///
2016/// This struct is created by the [`chunks_exact_mut`] method on [slices].
2017///
2018/// # Example
2019///
2020/// ```
2021/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
2022/// let iter = slice.chunks_exact_mut(2);
2023/// ```
2024///
2025/// [`chunks_exact_mut`]: slice::chunks_exact_mut
2026/// [`into_remainder`]: ChunksExactMut::into_remainder
2027/// [slices]: slice
2028#[derive(Debug)]
2029#[stable(feature = "chunks_exact", since = "1.31.0")]
2030#[must_use = "iterators are lazy and do nothing unless consumed"]
2031pub struct ChunksExactMut<'a, T: 'a> {
2032 /// # Safety
2033 /// This slice pointer must point at a valid region of `T` with at least length `v.len()`. Normally,
2034 /// those requirements would mean that we could instead use a `&mut [T]` here, but we cannot
2035 /// because `__iterator_get_unchecked` needs to return `&mut [T]`, which guarantees certain aliasing
2036 /// properties that we cannot uphold if we hold on to the full original `&mut [T]`. Wrapping a raw
2037 /// slice instead lets us hand out non-overlapping `&mut [T]` subslices of the slice we wrap.
2038 v: *mut [T],
2039 rem: &'a mut [T], // The iterator never yields from here, so this can be unique
2040 chunk_size: usize,
2041 _marker: PhantomData<&'a mut T>,
2042}
2043
2044impl<'a, T> ChunksExactMut<'a, T> {
2045 #[inline]
2046 pub(super) const fn new(slice: &'a mut [T], chunk_size: usize) -> Self {
2047 let rem = slice.len() % chunk_size;
2048 let fst_len = slice.len() - rem;
2049 // SAFETY: 0 <= fst_len <= slice.len() by construction above
2050 let (fst, snd) = unsafe { slice.split_at_mut_unchecked(fst_len) };
2051 Self { v: fst, rem: snd, chunk_size, _marker: PhantomData }
2052 }
2053
2054 /// Returns the remainder of the original slice that is not going to be
2055 /// returned by the iterator. The returned slice has at most `chunk_size-1`
2056 /// elements.
2057 #[must_use = "`self` will be dropped if the result is not used"]
2058 #[stable(feature = "chunks_exact", since = "1.31.0")]
2059 pub fn into_remainder(self) -> &'a mut [T] {
2060 self.rem
2061 }
2062}
2063
2064#[stable(feature = "chunks_exact", since = "1.31.0")]
2065impl<'a, T> Iterator for ChunksExactMut<'a, T> {
2066 type Item = &'a mut [T];
2067
2068 #[inline]
2069 fn next(&mut self) -> Option<&'a mut [T]> {
2070 if self.v.len() < self.chunk_size {
2071 None
2072 } else {
2073 // SAFETY: self.chunk_size is inbounds because we compared above against self.v.len()
2074 let (head, tail) = unsafe { self.v.split_at_mut(self.chunk_size) };
2075 self.v = tail;
2076 // SAFETY: Nothing else points to or will point to the contents of this slice.
2077 Some(unsafe { &mut *head })
2078 }
2079 }
2080
2081 #[inline]
2082 fn size_hint(&self) -> (usize, Option<usize>) {
2083 let n = self.v.len() / self.chunk_size;
2084 (n, Some(n))
2085 }
2086
2087 #[inline]
2088 fn count(self) -> usize {
2089 self.len()
2090 }
2091
2092 #[inline]
2093 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
2094 let (start, overflow) = n.overflowing_mul(self.chunk_size);
2095 if start >= self.v.len() || overflow {
2096 self.v = &mut [];
2097 None
2098 } else {
2099 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
2100 let (_, snd) = unsafe { self.v.split_at_mut(start) };
2101 self.v = snd;
2102 self.next()
2103 }
2104 }
2105
2106 #[inline]
2107 fn last(mut self) -> Option<Self::Item> {
2108 self.next_back()
2109 }
2110
2111 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
2112 let start = idx * self.chunk_size;
2113 // SAFETY: see comments for `Chunks::__iterator_get_unchecked` and `self.v`.
2114 unsafe { from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size) }
2115 }
2116}
2117
2118#[stable(feature = "chunks_exact", since = "1.31.0")]
2119impl<'a, T> DoubleEndedIterator for ChunksExactMut<'a, T> {
2120 #[inline]
2121 fn next_back(&mut self) -> Option<&'a mut [T]> {
2122 if self.v.len() < self.chunk_size {
2123 None
2124 } else {
2125 // SAFETY: This subtraction is inbounds because of the check above
2126 let (head, tail) = unsafe { self.v.split_at_mut(self.v.len() - self.chunk_size) };
2127 self.v = head;
2128 // SAFETY: Nothing else points to or will point to the contents of this slice.
2129 Some(unsafe { &mut *tail })
2130 }
2131 }
2132
2133 #[inline]
2134 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
2135 let len = self.len();
2136 if n >= len {
2137 self.v = &mut [];
2138 None
2139 } else {
2140 let start = (len - 1 - n) * self.chunk_size;
2141 let end = start + self.chunk_size;
2142 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
2143 let (temp, _tail) = unsafe { mem::replace(&mut self.v, &mut []).split_at_mut(end) };
2144 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
2145 let (head, nth_back) = unsafe { temp.split_at_mut(start) };
2146 self.v = head;
2147 // SAFETY: Nothing else points to or will point to the contents of this slice.
2148 Some(unsafe { &mut *nth_back })
2149 }
2150 }
2151}
2152
2153#[stable(feature = "chunks_exact", since = "1.31.0")]
2154impl<T> ExactSizeIterator for ChunksExactMut<'_, T> {
2155 fn is_empty(&self) -> bool {
2156 self.v.is_empty()
2157 }
2158}
2159
2160#[unstable(feature = "trusted_len", issue = "37572")]
2161unsafe impl<T> TrustedLen for ChunksExactMut<'_, T> {}
2162
2163#[stable(feature = "chunks_exact", since = "1.31.0")]
2164impl<T> FusedIterator for ChunksExactMut<'_, T> {}
2165
2166#[doc(hidden)]
2167#[unstable(feature = "trusted_random_access", issue = "none")]
2168unsafe impl<'a, T> TrustedRandomAccess for ChunksExactMut<'a, T> {}
2169
2170#[doc(hidden)]
2171#[unstable(feature = "trusted_random_access", issue = "none")]
2172unsafe impl<'a, T> TrustedRandomAccessNoCoerce for ChunksExactMut<'a, T> {
2173 const MAY_HAVE_SIDE_EFFECT: bool = false;
2174}
2175
2176#[stable(feature = "chunks_exact", since = "1.31.0")]
2177unsafe impl<T> Send for ChunksExactMut<'_, T> where T: Send {}
2178
2179#[stable(feature = "chunks_exact", since = "1.31.0")]
2180unsafe impl<T> Sync for ChunksExactMut<'_, T> where T: Sync {}
2181
2182/// A windowed iterator over a slice in overlapping chunks (`N` elements at a
2183/// time), starting at the beginning of the slice
2184///
2185/// This struct is created by the [`array_windows`] method on [slices].
2186///
2187/// # Example
2188///
2189/// ```
2190/// #![feature(array_windows)]
2191///
2192/// let slice = [0, 1, 2, 3];
2193/// let mut iter = slice.array_windows::<2>();
2194/// assert_eq!(iter.next(), Some(&[0, 1]));
2195/// assert_eq!(iter.next(), Some(&[1, 2]));
2196/// assert_eq!(iter.next(), Some(&[2, 3]));
2197/// assert_eq!(iter.next(), None);
2198/// ```
2199///
2200/// [`array_windows`]: slice::array_windows
2201/// [slices]: slice
2202#[derive(Debug, Clone, Copy)]
2203#[unstable(feature = "array_windows", issue = "75027")]
2204#[must_use = "iterators are lazy and do nothing unless consumed"]
2205pub struct ArrayWindows<'a, T: 'a, const N: usize> {
2206 slice_head: *const T,
2207 num: usize,
2208 marker: PhantomData<&'a [T; N]>,
2209}
2210
2211impl<'a, T: 'a, const N: usize> ArrayWindows<'a, T, N> {
2212 #[inline]
2213 pub(super) const fn new(slice: &'a [T]) -> Self {
2214 let num_windows = slice.len().saturating_sub(N - 1);
2215 Self { slice_head: slice.as_ptr(), num: num_windows, marker: PhantomData }
2216 }
2217}
2218
2219#[unstable(feature = "array_windows", issue = "75027")]
2220impl<'a, T, const N: usize> Iterator for ArrayWindows<'a, T, N> {
2221 type Item = &'a [T; N];
2222
2223 #[inline]
2224 fn next(&mut self) -> Option<Self::Item> {
2225 if self.num == 0 {
2226 return None;
2227 }
2228 // SAFETY:
2229 // This is safe because it's indexing into a slice guaranteed to be length > N.
2230 let ret = unsafe { &*self.slice_head.cast::<[T; N]>() };
2231 // SAFETY: Guaranteed that there are at least 1 item remaining otherwise
2232 // earlier branch would've been hit
2233 self.slice_head = unsafe { self.slice_head.add(1) };
2234
2235 self.num -= 1;
2236 Some(ret)
2237 }
2238
2239 #[inline]
2240 fn size_hint(&self) -> (usize, Option<usize>) {
2241 (self.num, Some(self.num))
2242 }
2243
2244 #[inline]
2245 fn count(self) -> usize {
2246 self.num
2247 }
2248
2249 #[inline]
2250 fn nth(&mut self, n: usize) -> Option<Self::Item> {
2251 if self.num <= n {
2252 self.num = 0;
2253 return None;
2254 }
2255 // SAFETY:
2256 // This is safe because it's indexing into a slice guaranteed to be length > N.
2257 let ret = unsafe { &*self.slice_head.add(n).cast::<[T; N]>() };
2258 // SAFETY: Guaranteed that there are at least n items remaining
2259 self.slice_head = unsafe { self.slice_head.add(n + 1) };
2260
2261 self.num -= n + 1;
2262 Some(ret)
2263 }
2264
2265 #[inline]
2266 fn last(mut self) -> Option<Self::Item> {
2267 self.nth(self.num.checked_sub(1)?)
2268 }
2269}
2270
2271#[unstable(feature = "array_windows", issue = "75027")]
2272impl<'a, T, const N: usize> DoubleEndedIterator for ArrayWindows<'a, T, N> {
2273 #[inline]
2274 fn next_back(&mut self) -> Option<&'a [T; N]> {
2275 if self.num == 0 {
2276 return None;
2277 }
2278 // SAFETY: Guaranteed that there are n items remaining, n-1 for 0-indexing.
2279 let ret = unsafe { &*self.slice_head.add(self.num - 1).cast::<[T; N]>() };
2280 self.num -= 1;
2281 Some(ret)
2282 }
2283
2284 #[inline]
2285 fn nth_back(&mut self, n: usize) -> Option<&'a [T; N]> {
2286 if self.num <= n {
2287 self.num = 0;
2288 return None;
2289 }
2290 // SAFETY: Guaranteed that there are n items remaining, n-1 for 0-indexing.
2291 let ret = unsafe { &*self.slice_head.add(self.num - (n + 1)).cast::<[T; N]>() };
2292 self.num -= n + 1;
2293 Some(ret)
2294 }
2295}
2296
2297#[unstable(feature = "array_windows", issue = "75027")]
2298impl<T, const N: usize> ExactSizeIterator for ArrayWindows<'_, T, N> {
2299 fn is_empty(&self) -> bool {
2300 self.num == 0
2301 }
2302}
2303
2304/// An iterator over a slice in (non-overlapping) chunks (`N` elements at a
2305/// time), starting at the beginning of the slice.
2306///
2307/// When the slice len is not evenly divided by the chunk size, the last
2308/// up to `N-1` elements will be omitted but can be retrieved from
2309/// the [`remainder`] function from the iterator.
2310///
2311/// This struct is created by the [`array_chunks`] method on [slices].
2312///
2313/// # Example
2314///
2315/// ```
2316/// #![feature(array_chunks)]
2317///
2318/// let slice = ['l', 'o', 'r', 'e', 'm'];
2319/// let mut iter = slice.array_chunks::<2>();
2320/// assert_eq!(iter.next(), Some(&['l', 'o']));
2321/// assert_eq!(iter.next(), Some(&['r', 'e']));
2322/// assert_eq!(iter.next(), None);
2323/// ```
2324///
2325/// [`array_chunks`]: slice::array_chunks
2326/// [`remainder`]: ArrayChunks::remainder
2327/// [slices]: slice
2328#[derive(Debug)]
2329#[unstable(feature = "array_chunks", issue = "74985")]
2330#[must_use = "iterators are lazy and do nothing unless consumed"]
2331pub struct ArrayChunks<'a, T: 'a, const N: usize> {
2332 iter: Iter<'a, [T; N]>,
2333 rem: &'a [T],
2334}
2335
2336impl<'a, T, const N: usize> ArrayChunks<'a, T, N> {
2337 #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
2338 #[inline]
2339 pub(super) const fn new(slice: &'a [T]) -> Self {
2340 let (array_slice, rem) = slice.as_chunks();
2341 Self { iter: array_slice.iter(), rem }
2342 }
2343
2344 /// Returns the remainder of the original slice that is not going to be
2345 /// returned by the iterator. The returned slice has at most `N-1`
2346 /// elements.
2347 #[must_use]
2348 #[unstable(feature = "array_chunks", issue = "74985")]
2349 pub fn remainder(&self) -> &'a [T] {
2350 self.rem
2351 }
2352}
2353
2354// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
2355#[unstable(feature = "array_chunks", issue = "74985")]
2356impl<T, const N: usize> Clone for ArrayChunks<'_, T, N> {
2357 fn clone(&self) -> Self {
2358 ArrayChunks { iter: self.iter.clone(), rem: self.rem }
2359 }
2360}
2361
2362#[unstable(feature = "array_chunks", issue = "74985")]
2363impl<'a, T, const N: usize> Iterator for ArrayChunks<'a, T, N> {
2364 type Item = &'a [T; N];
2365
2366 #[inline]
2367 fn next(&mut self) -> Option<&'a [T; N]> {
2368 self.iter.next()
2369 }
2370
2371 #[inline]
2372 fn size_hint(&self) -> (usize, Option<usize>) {
2373 self.iter.size_hint()
2374 }
2375
2376 #[inline]
2377 fn count(self) -> usize {
2378 self.iter.count()
2379 }
2380
2381 #[inline]
2382 fn nth(&mut self, n: usize) -> Option<Self::Item> {
2383 self.iter.nth(n)
2384 }
2385
2386 #[inline]
2387 fn last(self) -> Option<Self::Item> {
2388 self.iter.last()
2389 }
2390
2391 unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> &'a [T; N] {
2392 // SAFETY: The safety guarantees of `__iterator_get_unchecked` are
2393 // transferred to the caller.
2394 unsafe { self.iter.__iterator_get_unchecked(i) }
2395 }
2396}
2397
2398#[unstable(feature = "array_chunks", issue = "74985")]
2399impl<'a, T, const N: usize> DoubleEndedIterator for ArrayChunks<'a, T, N> {
2400 #[inline]
2401 fn next_back(&mut self) -> Option<&'a [T; N]> {
2402 self.iter.next_back()
2403 }
2404
2405 #[inline]
2406 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
2407 self.iter.nth_back(n)
2408 }
2409}
2410
2411#[unstable(feature = "array_chunks", issue = "74985")]
2412impl<T, const N: usize> ExactSizeIterator for ArrayChunks<'_, T, N> {
2413 fn is_empty(&self) -> bool {
2414 self.iter.is_empty()
2415 }
2416}
2417
2418#[unstable(feature = "trusted_len", issue = "37572")]
2419unsafe impl<T, const N: usize> TrustedLen for ArrayChunks<'_, T, N> {}
2420
2421#[unstable(feature = "array_chunks", issue = "74985")]
2422impl<T, const N: usize> FusedIterator for ArrayChunks<'_, T, N> {}
2423
2424#[doc(hidden)]
2425#[unstable(feature = "array_chunks", issue = "74985")]
2426unsafe impl<'a, T, const N: usize> TrustedRandomAccess for ArrayChunks<'a, T, N> {}
2427
2428#[doc(hidden)]
2429#[unstable(feature = "array_chunks", issue = "74985")]
2430unsafe impl<'a, T, const N: usize> TrustedRandomAccessNoCoerce for ArrayChunks<'a, T, N> {
2431 const MAY_HAVE_SIDE_EFFECT: bool = false;
2432}
2433
2434/// An iterator over a slice in (non-overlapping) mutable chunks (`N` elements
2435/// at a time), starting at the beginning of the slice.
2436///
2437/// When the slice len is not evenly divided by the chunk size, the last
2438/// up to `N-1` elements will be omitted but can be retrieved from
2439/// the [`into_remainder`] function from the iterator.
2440///
2441/// This struct is created by the [`array_chunks_mut`] method on [slices].
2442///
2443/// # Example
2444///
2445/// ```
2446/// #![feature(array_chunks)]
2447///
2448/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
2449/// let iter = slice.array_chunks_mut::<2>();
2450/// ```
2451///
2452/// [`array_chunks_mut`]: slice::array_chunks_mut
2453/// [`into_remainder`]: ../../std/slice/struct.ArrayChunksMut.html#method.into_remainder
2454/// [slices]: slice
2455#[derive(Debug)]
2456#[unstable(feature = "array_chunks", issue = "74985")]
2457#[must_use = "iterators are lazy and do nothing unless consumed"]
2458pub struct ArrayChunksMut<'a, T: 'a, const N: usize> {
2459 iter: IterMut<'a, [T; N]>,
2460 rem: &'a mut [T],
2461}
2462
2463impl<'a, T, const N: usize> ArrayChunksMut<'a, T, N> {
2464 #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
2465 #[inline]
2466 pub(super) const fn new(slice: &'a mut [T]) -> Self {
2467 let (array_slice, rem) = slice.as_chunks_mut();
2468 Self { iter: array_slice.iter_mut(), rem }
2469 }
2470
2471 /// Returns the remainder of the original slice that is not going to be
2472 /// returned by the iterator. The returned slice has at most `N-1`
2473 /// elements.
2474 #[must_use = "`self` will be dropped if the result is not used"]
2475 #[unstable(feature = "array_chunks", issue = "74985")]
2476 pub fn into_remainder(self) -> &'a mut [T] {
2477 self.rem
2478 }
2479}
2480
2481#[unstable(feature = "array_chunks", issue = "74985")]
2482impl<'a, T, const N: usize> Iterator for ArrayChunksMut<'a, T, N> {
2483 type Item = &'a mut [T; N];
2484
2485 #[inline]
2486 fn next(&mut self) -> Option<&'a mut [T; N]> {
2487 self.iter.next()
2488 }
2489
2490 #[inline]
2491 fn size_hint(&self) -> (usize, Option<usize>) {
2492 self.iter.size_hint()
2493 }
2494
2495 #[inline]
2496 fn count(self) -> usize {
2497 self.iter.count()
2498 }
2499
2500 #[inline]
2501 fn nth(&mut self, n: usize) -> Option<Self::Item> {
2502 self.iter.nth(n)
2503 }
2504
2505 #[inline]
2506 fn last(self) -> Option<Self::Item> {
2507 self.iter.last()
2508 }
2509
2510 unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> &'a mut [T; N] {
2511 // SAFETY: The safety guarantees of `__iterator_get_unchecked` are transferred to
2512 // the caller.
2513 unsafe { self.iter.__iterator_get_unchecked(i) }
2514 }
2515}
2516
2517#[unstable(feature = "array_chunks", issue = "74985")]
2518impl<'a, T, const N: usize> DoubleEndedIterator for ArrayChunksMut<'a, T, N> {
2519 #[inline]
2520 fn next_back(&mut self) -> Option<&'a mut [T; N]> {
2521 self.iter.next_back()
2522 }
2523
2524 #[inline]
2525 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
2526 self.iter.nth_back(n)
2527 }
2528}
2529
2530#[unstable(feature = "array_chunks", issue = "74985")]
2531impl<T, const N: usize> ExactSizeIterator for ArrayChunksMut<'_, T, N> {
2532 fn is_empty(&self) -> bool {
2533 self.iter.is_empty()
2534 }
2535}
2536
2537#[unstable(feature = "trusted_len", issue = "37572")]
2538unsafe impl<T, const N: usize> TrustedLen for ArrayChunksMut<'_, T, N> {}
2539
2540#[unstable(feature = "array_chunks", issue = "74985")]
2541impl<T, const N: usize> FusedIterator for ArrayChunksMut<'_, T, N> {}
2542
2543#[doc(hidden)]
2544#[unstable(feature = "array_chunks", issue = "74985")]
2545unsafe impl<'a, T, const N: usize> TrustedRandomAccess for ArrayChunksMut<'a, T, N> {}
2546
2547#[doc(hidden)]
2548#[unstable(feature = "array_chunks", issue = "74985")]
2549unsafe impl<'a, T, const N: usize> TrustedRandomAccessNoCoerce for ArrayChunksMut<'a, T, N> {
2550 const MAY_HAVE_SIDE_EFFECT: bool = false;
2551}
2552
2553/// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
2554/// time), starting at the end of the slice.
2555///
2556/// When the slice len is not evenly divided by the chunk size, the last slice
2557/// of the iteration will be the remainder.
2558///
2559/// This struct is created by the [`rchunks`] method on [slices].
2560///
2561/// # Example
2562///
2563/// ```
2564/// let slice = ['l', 'o', 'r', 'e', 'm'];
2565/// let mut iter = slice.rchunks(2);
2566/// assert_eq!(iter.next(), Some(&['e', 'm'][..]));
2567/// assert_eq!(iter.next(), Some(&['o', 'r'][..]));
2568/// assert_eq!(iter.next(), Some(&['l'][..]));
2569/// assert_eq!(iter.next(), None);
2570/// ```
2571///
2572/// [`rchunks`]: slice::rchunks
2573/// [slices]: slice
2574#[derive(Debug)]
2575#[stable(feature = "rchunks", since = "1.31.0")]
2576#[must_use = "iterators are lazy and do nothing unless consumed"]
2577pub struct RChunks<'a, T: 'a> {
2578 v: &'a [T],
2579 chunk_size: usize,
2580}
2581
2582impl<'a, T: 'a> RChunks<'a, T> {
2583 #[inline]
2584 pub(super) const fn new(slice: &'a [T], size: usize) -> Self {
2585 Self { v: slice, chunk_size: size }
2586 }
2587}
2588
2589// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
2590#[stable(feature = "rchunks", since = "1.31.0")]
2591impl<T> Clone for RChunks<'_, T> {
2592 fn clone(&self) -> Self {
2593 RChunks { v: self.v, chunk_size: self.chunk_size }
2594 }
2595}
2596
2597#[stable(feature = "rchunks", since = "1.31.0")]
2598impl<'a, T> Iterator for RChunks<'a, T> {
2599 type Item = &'a [T];
2600
2601 #[inline]
2602 fn next(&mut self) -> Option<&'a [T]> {
2603 if self.v.is_empty() {
2604 None
2605 } else {
2606 let len = self.v.len();
2607 let chunksz = cmp::min(len, self.chunk_size);
2608 // SAFETY: split_at_unchecked just requires the argument be less
2609 // than the length. This could only happen if the expression `len -
2610 // chunksz` overflows. This could only happen if `chunksz > len`,
2611 // which is impossible as we initialize it as the `min` of `len` and
2612 // `self.chunk_size`.
2613 let (fst, snd) = unsafe { self.v.split_at_unchecked(len - chunksz) };
2614 self.v = fst;
2615 Some(snd)
2616 }
2617 }
2618
2619 #[inline]
2620 fn size_hint(&self) -> (usize, Option<usize>) {
2621 if self.v.is_empty() {
2622 (0, Some(0))
2623 } else {
2624 let n = self.v.len() / self.chunk_size;
2625 let rem = self.v.len() % self.chunk_size;
2626 let n = if rem > 0 { n + 1 } else { n };
2627 (n, Some(n))
2628 }
2629 }
2630
2631 #[inline]
2632 fn count(self) -> usize {
2633 self.len()
2634 }
2635
2636 #[inline]
2637 fn nth(&mut self, n: usize) -> Option<Self::Item> {
2638 let (end, overflow) = n.overflowing_mul(self.chunk_size);
2639 if end >= self.v.len() || overflow {
2640 self.v = &self.v[..0]; // cheaper than &[]
2641 None
2642 } else {
2643 // Can't underflow because of the check above
2644 let end = self.v.len() - end;
2645 let start = match end.checked_sub(self.chunk_size) {
2646 Some(sum) => sum,
2647 None => 0,
2648 };
2649 let nth = &self.v[start..end];
2650 self.v = &self.v[0..start];
2651 Some(nth)
2652 }
2653 }
2654
2655 #[inline]
2656 fn last(self) -> Option<Self::Item> {
2657 if self.v.is_empty() {
2658 None
2659 } else {
2660 let rem = self.v.len() % self.chunk_size;
2661 let end = if rem == 0 { self.chunk_size } else { rem };
2662 Some(&self.v[0..end])
2663 }
2664 }
2665
2666 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
2667 let end = self.v.len() - idx * self.chunk_size;
2668 let start = match end.checked_sub(self.chunk_size) {
2669 None => 0,
2670 Some(start) => start,
2671 };
2672 // SAFETY: mostly identical to `Chunks::__iterator_get_unchecked`.
2673 unsafe { from_raw_parts(self.v.as_ptr().add(start), end - start) }
2674 }
2675}
2676
2677#[stable(feature = "rchunks", since = "1.31.0")]
2678impl<'a, T> DoubleEndedIterator for RChunks<'a, T> {
2679 #[inline]
2680 fn next_back(&mut self) -> Option<&'a [T]> {
2681 if self.v.is_empty() {
2682 None
2683 } else {
2684 let remainder = self.v.len() % self.chunk_size;
2685 let chunksz = if remainder != 0 { remainder } else { self.chunk_size };
2686 // SAFETY: similar to Chunks::next_back
2687 let (fst, snd) = unsafe { self.v.split_at_unchecked(chunksz) };
2688 self.v = snd;
2689 Some(fst)
2690 }
2691 }
2692
2693 #[inline]
2694 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
2695 let len = self.len();
2696 if n >= len {
2697 self.v = &self.v[..0]; // cheaper than &[]
2698 None
2699 } else {
2700 // can't underflow because `n < len`
2701 let offset_from_end = (len - 1 - n) * self.chunk_size;
2702 let end = self.v.len() - offset_from_end;
2703 let start = end.saturating_sub(self.chunk_size);
2704 let nth_back = &self.v[start..end];
2705 self.v = &self.v[end..];
2706 Some(nth_back)
2707 }
2708 }
2709}
2710
2711#[stable(feature = "rchunks", since = "1.31.0")]
2712impl<T> ExactSizeIterator for RChunks<'_, T> {}
2713
2714#[unstable(feature = "trusted_len", issue = "37572")]
2715unsafe impl<T> TrustedLen for RChunks<'_, T> {}
2716
2717#[stable(feature = "rchunks", since = "1.31.0")]
2718impl<T> FusedIterator for RChunks<'_, T> {}
2719
2720#[doc(hidden)]
2721#[unstable(feature = "trusted_random_access", issue = "none")]
2722unsafe impl<'a, T> TrustedRandomAccess for RChunks<'a, T> {}
2723
2724#[doc(hidden)]
2725#[unstable(feature = "trusted_random_access", issue = "none")]
2726unsafe impl<'a, T> TrustedRandomAccessNoCoerce for RChunks<'a, T> {
2727 const MAY_HAVE_SIDE_EFFECT: bool = false;
2728}
2729
2730/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
2731/// elements at a time), starting at the end of the slice.
2732///
2733/// When the slice len is not evenly divided by the chunk size, the last slice
2734/// of the iteration will be the remainder.
2735///
2736/// This struct is created by the [`rchunks_mut`] method on [slices].
2737///
2738/// # Example
2739///
2740/// ```
2741/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
2742/// let iter = slice.rchunks_mut(2);
2743/// ```
2744///
2745/// [`rchunks_mut`]: slice::rchunks_mut
2746/// [slices]: slice
2747#[derive(Debug)]
2748#[stable(feature = "rchunks", since = "1.31.0")]
2749#[must_use = "iterators are lazy and do nothing unless consumed"]
2750pub struct RChunksMut<'a, T: 'a> {
2751 /// # Safety
2752 /// This slice pointer must point at a valid region of `T` with at least length `v.len()`. Normally,
2753 /// those requirements would mean that we could instead use a `&mut [T]` here, but we cannot
2754 /// because `__iterator_get_unchecked` needs to return `&mut [T]`, which guarantees certain aliasing
2755 /// properties that we cannot uphold if we hold on to the full original `&mut [T]`. Wrapping a raw
2756 /// slice instead lets us hand out non-overlapping `&mut [T]` subslices of the slice we wrap.
2757 v: *mut [T],
2758 chunk_size: usize,
2759 _marker: PhantomData<&'a mut T>,
2760}
2761
2762impl<'a, T: 'a> RChunksMut<'a, T> {
2763 #[inline]
2764 pub(super) const fn new(slice: &'a mut [T], size: usize) -> Self {
2765 Self { v: slice, chunk_size: size, _marker: PhantomData }
2766 }
2767}
2768
2769#[stable(feature = "rchunks", since = "1.31.0")]
2770impl<'a, T> Iterator for RChunksMut<'a, T> {
2771 type Item = &'a mut [T];
2772
2773 #[inline]
2774 fn next(&mut self) -> Option<&'a mut [T]> {
2775 if self.v.is_empty() {
2776 None
2777 } else {
2778 let sz = cmp::min(self.v.len(), self.chunk_size);
2779 let len = self.v.len();
2780 // SAFETY: split_at_mut_unchecked just requires the argument be less
2781 // than the length. This could only happen if the expression
2782 // `len - sz` overflows. This could only happen if `sz >
2783 // len`, which is impossible as we initialize it as the `min` of
2784 // `self.v.len()` (e.g. `len`) and `self.chunk_size`.
2785 let (head, tail) = unsafe { self.v.split_at_mut_unchecked(len - sz) };
2786 self.v = head;
2787 // SAFETY: Nothing else points to or will point to the contents of this slice.
2788 Some(unsafe { &mut *tail })
2789 }
2790 }
2791
2792 #[inline]
2793 fn size_hint(&self) -> (usize, Option<usize>) {
2794 if self.v.is_empty() {
2795 (0, Some(0))
2796 } else {
2797 let n = self.v.len() / self.chunk_size;
2798 let rem = self.v.len() % self.chunk_size;
2799 let n = if rem > 0 { n + 1 } else { n };
2800 (n, Some(n))
2801 }
2802 }
2803
2804 #[inline]
2805 fn count(self) -> usize {
2806 self.len()
2807 }
2808
2809 #[inline]
2810 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
2811 let (end, overflow) = n.overflowing_mul(self.chunk_size);
2812 if end >= self.v.len() || overflow {
2813 self.v = &mut [];
2814 None
2815 } else {
2816 // Can't underflow because of the check above
2817 let end = self.v.len() - end;
2818 let start = match end.checked_sub(self.chunk_size) {
2819 Some(sum) => sum,
2820 None => 0,
2821 };
2822 // SAFETY: This type ensures that self.v is a valid pointer with a correct len.
2823 // Therefore the bounds check in split_at_mut guarantees the split point is inbounds.
2824 let (head, tail) = unsafe { self.v.split_at_mut(start) };
2825 // SAFETY: This type ensures that self.v is a valid pointer with a correct len.
2826 // Therefore the bounds check in split_at_mut guarantees the split point is inbounds.
2827 let (nth, _) = unsafe { tail.split_at_mut(end - start) };
2828 self.v = head;
2829 // SAFETY: Nothing else points to or will point to the contents of this slice.
2830 Some(unsafe { &mut *nth })
2831 }
2832 }
2833
2834 #[inline]
2835 fn last(self) -> Option<Self::Item> {
2836 if self.v.is_empty() {
2837 None
2838 } else {
2839 let rem = self.v.len() % self.chunk_size;
2840 let end = if rem == 0 { self.chunk_size } else { rem };
2841 // SAFETY: Nothing else points to or will point to the contents of this slice.
2842 Some(unsafe { &mut *self.v.get_unchecked_mut(0..end) })
2843 }
2844 }
2845
2846 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
2847 let end = self.v.len() - idx * self.chunk_size;
2848 let start = match end.checked_sub(self.chunk_size) {
2849 None => 0,
2850 Some(start) => start,
2851 };
2852 // SAFETY: see comments for `RChunks::__iterator_get_unchecked` and
2853 // `ChunksMut::__iterator_get_unchecked`, `self.v`.
2854 unsafe { from_raw_parts_mut(self.v.as_mut_ptr().add(start), end - start) }
2855 }
2856}
2857
2858#[stable(feature = "rchunks", since = "1.31.0")]
2859impl<'a, T> DoubleEndedIterator for RChunksMut<'a, T> {
2860 #[inline]
2861 fn next_back(&mut self) -> Option<&'a mut [T]> {
2862 if self.v.is_empty() {
2863 None
2864 } else {
2865 let remainder = self.v.len() % self.chunk_size;
2866 let sz = if remainder != 0 { remainder } else { self.chunk_size };
2867 // SAFETY: Similar to `Chunks::next_back`
2868 let (head, tail) = unsafe { self.v.split_at_mut_unchecked(sz) };
2869 self.v = tail;
2870 // SAFETY: Nothing else points to or will point to the contents of this slice.
2871 Some(unsafe { &mut *head })
2872 }
2873 }
2874
2875 #[inline]
2876 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
2877 let len = self.len();
2878 if n >= len {
2879 self.v = &mut [];
2880 None
2881 } else {
2882 // can't underflow because `n < len`
2883 let offset_from_end = (len - 1 - n) * self.chunk_size;
2884 let end = self.v.len() - offset_from_end;
2885 let start = end.saturating_sub(self.chunk_size);
2886 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
2887 let (tmp, tail) = unsafe { self.v.split_at_mut(end) };
2888 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
2889 let (_, nth_back) = unsafe { tmp.split_at_mut(start) };
2890 self.v = tail;
2891 // SAFETY: Nothing else points to or will point to the contents of this slice.
2892 Some(unsafe { &mut *nth_back })
2893 }
2894 }
2895}
2896
2897#[stable(feature = "rchunks", since = "1.31.0")]
2898impl<T> ExactSizeIterator for RChunksMut<'_, T> {}
2899
2900#[unstable(feature = "trusted_len", issue = "37572")]
2901unsafe impl<T> TrustedLen for RChunksMut<'_, T> {}
2902
2903#[stable(feature = "rchunks", since = "1.31.0")]
2904impl<T> FusedIterator for RChunksMut<'_, T> {}
2905
2906#[doc(hidden)]
2907#[unstable(feature = "trusted_random_access", issue = "none")]
2908unsafe impl<'a, T> TrustedRandomAccess for RChunksMut<'a, T> {}
2909
2910#[doc(hidden)]
2911#[unstable(feature = "trusted_random_access", issue = "none")]
2912unsafe impl<'a, T> TrustedRandomAccessNoCoerce for RChunksMut<'a, T> {
2913 const MAY_HAVE_SIDE_EFFECT: bool = false;
2914}
2915
2916#[stable(feature = "rchunks", since = "1.31.0")]
2917unsafe impl<T> Send for RChunksMut<'_, T> where T: Send {}
2918
2919#[stable(feature = "rchunks", since = "1.31.0")]
2920unsafe impl<T> Sync for RChunksMut<'_, T> where T: Sync {}
2921
2922/// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
2923/// time), starting at the end of the slice.
2924///
2925/// When the slice len is not evenly divided by the chunk size, the last
2926/// up to `chunk_size-1` elements will be omitted but can be retrieved from
2927/// the [`remainder`] function from the iterator.
2928///
2929/// This struct is created by the [`rchunks_exact`] method on [slices].
2930///
2931/// # Example
2932///
2933/// ```
2934/// let slice = ['l', 'o', 'r', 'e', 'm'];
2935/// let mut iter = slice.rchunks_exact(2);
2936/// assert_eq!(iter.next(), Some(&['e', 'm'][..]));
2937/// assert_eq!(iter.next(), Some(&['o', 'r'][..]));
2938/// assert_eq!(iter.next(), None);
2939/// ```
2940///
2941/// [`rchunks_exact`]: slice::rchunks_exact
2942/// [`remainder`]: RChunksExact::remainder
2943/// [slices]: slice
2944#[derive(Debug)]
2945#[stable(feature = "rchunks", since = "1.31.0")]
2946#[must_use = "iterators are lazy and do nothing unless consumed"]
2947pub struct RChunksExact<'a, T: 'a> {
2948 v: &'a [T],
2949 rem: &'a [T],
2950 chunk_size: usize,
2951}
2952
2953impl<'a, T> RChunksExact<'a, T> {
2954 #[inline]
2955 pub(super) const fn new(slice: &'a [T], chunk_size: usize) -> Self {
2956 let rem = slice.len() % chunk_size;
2957 // SAFETY: 0 <= rem <= slice.len() by construction above
2958 let (fst, snd) = unsafe { slice.split_at_unchecked(rem) };
2959 Self { v: snd, rem: fst, chunk_size }
2960 }
2961
2962 /// Returns the remainder of the original slice that is not going to be
2963 /// returned by the iterator. The returned slice has at most `chunk_size-1`
2964 /// elements.
2965 ///
2966 /// # Example
2967 ///
2968 /// ```
2969 /// let slice = ['l', 'o', 'r', 'e', 'm'];
2970 /// let mut iter = slice.rchunks_exact(2);
2971 /// assert_eq!(iter.remainder(), &['l'][..]);
2972 /// assert_eq!(iter.next(), Some(&['e', 'm'][..]));
2973 /// assert_eq!(iter.remainder(), &['l'][..]);
2974 /// assert_eq!(iter.next(), Some(&['o', 'r'][..]));
2975 /// assert_eq!(iter.remainder(), &['l'][..]);
2976 /// assert_eq!(iter.next(), None);
2977 /// assert_eq!(iter.remainder(), &['l'][..]);
2978 /// ```
2979 #[must_use]
2980 #[stable(feature = "rchunks", since = "1.31.0")]
2981 #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
2982 pub const fn remainder(&self) -> &'a [T] {
2983 self.rem
2984 }
2985}
2986
2987// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
2988#[stable(feature = "rchunks", since = "1.31.0")]
2989impl<'a, T> Clone for RChunksExact<'a, T> {
2990 fn clone(&self) -> RChunksExact<'a, T> {
2991 RChunksExact { v: self.v, rem: self.rem, chunk_size: self.chunk_size }
2992 }
2993}
2994
2995#[stable(feature = "rchunks", since = "1.31.0")]
2996impl<'a, T> Iterator for RChunksExact<'a, T> {
2997 type Item = &'a [T];
2998
2999 #[inline]
3000 fn next(&mut self) -> Option<&'a [T]> {
3001 if self.v.len() < self.chunk_size {
3002 None
3003 } else {
3004 let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size);
3005 self.v = fst;
3006 Some(snd)
3007 }
3008 }
3009
3010 #[inline]
3011 fn size_hint(&self) -> (usize, Option<usize>) {
3012 let n = self.v.len() / self.chunk_size;
3013 (n, Some(n))
3014 }
3015
3016 #[inline]
3017 fn count(self) -> usize {
3018 self.len()
3019 }
3020
3021 #[inline]
3022 fn nth(&mut self, n: usize) -> Option<Self::Item> {
3023 let (end, overflow) = n.overflowing_mul(self.chunk_size);
3024 if end >= self.v.len() || overflow {
3025 self.v = &self.v[..0]; // cheaper than &[]
3026 None
3027 } else {
3028 let (fst, _) = self.v.split_at(self.v.len() - end);
3029 self.v = fst;
3030 self.next()
3031 }
3032 }
3033
3034 #[inline]
3035 fn last(mut self) -> Option<Self::Item> {
3036 self.next_back()
3037 }
3038
3039 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
3040 let end = self.v.len() - idx * self.chunk_size;
3041 let start = end - self.chunk_size;
3042 // SAFETY: mostly identical to `Chunks::__iterator_get_unchecked`.
3043 unsafe { from_raw_parts(self.v.as_ptr().add(start), self.chunk_size) }
3044 }
3045}
3046
3047#[stable(feature = "rchunks", since = "1.31.0")]
3048impl<'a, T> DoubleEndedIterator for RChunksExact<'a, T> {
3049 #[inline]
3050 fn next_back(&mut self) -> Option<&'a [T]> {
3051 if self.v.len() < self.chunk_size {
3052 None
3053 } else {
3054 let (fst, snd) = self.v.split_at(self.chunk_size);
3055 self.v = snd;
3056 Some(fst)
3057 }
3058 }
3059
3060 #[inline]
3061 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
3062 let len = self.len();
3063 if n >= len {
3064 self.v = &self.v[..0]; // cheaper than &[]
3065 None
3066 } else {
3067 // now that we know that `n` corresponds to a chunk,
3068 // none of these operations can underflow/overflow
3069 let offset = (len - n) * self.chunk_size;
3070 let start = self.v.len() - offset;
3071 let end = start + self.chunk_size;
3072 let nth_back = &self.v[start..end];
3073 self.v = &self.v[end..];
3074 Some(nth_back)
3075 }
3076 }
3077}
3078
3079#[stable(feature = "rchunks", since = "1.31.0")]
3080impl<'a, T> ExactSizeIterator for RChunksExact<'a, T> {
3081 fn is_empty(&self) -> bool {
3082 self.v.is_empty()
3083 }
3084}
3085
3086#[unstable(feature = "trusted_len", issue = "37572")]
3087unsafe impl<T> TrustedLen for RChunksExact<'_, T> {}
3088
3089#[stable(feature = "rchunks", since = "1.31.0")]
3090impl<T> FusedIterator for RChunksExact<'_, T> {}
3091
3092#[doc(hidden)]
3093#[unstable(feature = "trusted_random_access", issue = "none")]
3094unsafe impl<'a, T> TrustedRandomAccess for RChunksExact<'a, T> {}
3095
3096#[doc(hidden)]
3097#[unstable(feature = "trusted_random_access", issue = "none")]
3098unsafe impl<'a, T> TrustedRandomAccessNoCoerce for RChunksExact<'a, T> {
3099 const MAY_HAVE_SIDE_EFFECT: bool = false;
3100}
3101
3102/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size`
3103/// elements at a time), starting at the end of the slice.
3104///
3105/// When the slice len is not evenly divided by the chunk size, the last up to
3106/// `chunk_size-1` elements will be omitted but can be retrieved from the
3107/// [`into_remainder`] function from the iterator.
3108///
3109/// This struct is created by the [`rchunks_exact_mut`] method on [slices].
3110///
3111/// # Example
3112///
3113/// ```
3114/// let mut slice = ['l', 'o', 'r', 'e', 'm'];
3115/// let iter = slice.rchunks_exact_mut(2);
3116/// ```
3117///
3118/// [`rchunks_exact_mut`]: slice::rchunks_exact_mut
3119/// [`into_remainder`]: RChunksExactMut::into_remainder
3120/// [slices]: slice
3121#[derive(Debug)]
3122#[stable(feature = "rchunks", since = "1.31.0")]
3123#[must_use = "iterators are lazy and do nothing unless consumed"]
3124pub struct RChunksExactMut<'a, T: 'a> {
3125 /// # Safety
3126 /// This slice pointer must point at a valid region of `T` with at least length `v.len()`. Normally,
3127 /// those requirements would mean that we could instead use a `&mut [T]` here, but we cannot
3128 /// because `__iterator_get_unchecked` needs to return `&mut [T]`, which guarantees certain aliasing
3129 /// properties that we cannot uphold if we hold on to the full original `&mut [T]`. Wrapping a raw
3130 /// slice instead lets us hand out non-overlapping `&mut [T]` subslices of the slice we wrap.
3131 v: *mut [T],
3132 rem: &'a mut [T],
3133 chunk_size: usize,
3134}
3135
3136impl<'a, T> RChunksExactMut<'a, T> {
3137 #[inline]
3138 pub(super) const fn new(slice: &'a mut [T], chunk_size: usize) -> Self {
3139 let rem = slice.len() % chunk_size;
3140 // SAFETY: 0 <= rem <= slice.len() by construction above
3141 let (fst, snd) = unsafe { slice.split_at_mut_unchecked(rem) };
3142 Self { v: snd, rem: fst, chunk_size }
3143 }
3144
3145 /// Returns the remainder of the original slice that is not going to be
3146 /// returned by the iterator. The returned slice has at most `chunk_size-1`
3147 /// elements.
3148 #[must_use = "`self` will be dropped if the result is not used"]
3149 #[stable(feature = "rchunks", since = "1.31.0")]
3150 #[rustc_const_unstable(feature = "const_slice_make_iter", issue = "137737")]
3151 pub const fn into_remainder(self) -> &'a mut [T] {
3152 self.rem
3153 }
3154}
3155
3156#[stable(feature = "rchunks", since = "1.31.0")]
3157impl<'a, T> Iterator for RChunksExactMut<'a, T> {
3158 type Item = &'a mut [T];
3159
3160 #[inline]
3161 fn next(&mut self) -> Option<&'a mut [T]> {
3162 if self.v.len() < self.chunk_size {
3163 None
3164 } else {
3165 let len = self.v.len();
3166 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
3167 let (head, tail) = unsafe { self.v.split_at_mut(len - self.chunk_size) };
3168 self.v = head;
3169 // SAFETY: Nothing else points to or will point to the contents of this slice.
3170 Some(unsafe { &mut *tail })
3171 }
3172 }
3173
3174 #[inline]
3175 fn size_hint(&self) -> (usize, Option<usize>) {
3176 let n = self.v.len() / self.chunk_size;
3177 (n, Some(n))
3178 }
3179
3180 #[inline]
3181 fn count(self) -> usize {
3182 self.len()
3183 }
3184
3185 #[inline]
3186 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
3187 let (end, overflow) = n.overflowing_mul(self.chunk_size);
3188 if end >= self.v.len() || overflow {
3189 self.v = &mut [];
3190 None
3191 } else {
3192 let len = self.v.len();
3193 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
3194 let (fst, _) = unsafe { self.v.split_at_mut(len - end) };
3195 self.v = fst;
3196 self.next()
3197 }
3198 }
3199
3200 #[inline]
3201 fn last(mut self) -> Option<Self::Item> {
3202 self.next_back()
3203 }
3204
3205 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
3206 let end = self.v.len() - idx * self.chunk_size;
3207 let start = end - self.chunk_size;
3208 // SAFETY: see comments for `RChunksMut::__iterator_get_unchecked` and `self.v`.
3209 unsafe { from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size) }
3210 }
3211}
3212
3213#[stable(feature = "rchunks", since = "1.31.0")]
3214impl<'a, T> DoubleEndedIterator for RChunksExactMut<'a, T> {
3215 #[inline]
3216 fn next_back(&mut self) -> Option<&'a mut [T]> {
3217 if self.v.len() < self.chunk_size {
3218 None
3219 } else {
3220 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
3221 let (head, tail) = unsafe { self.v.split_at_mut(self.chunk_size) };
3222 self.v = tail;
3223 // SAFETY: Nothing else points to or will point to the contents of this slice.
3224 Some(unsafe { &mut *head })
3225 }
3226 }
3227
3228 #[inline]
3229 fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
3230 let len = self.len();
3231 if n >= len {
3232 self.v = &mut [];
3233 None
3234 } else {
3235 // now that we know that `n` corresponds to a chunk,
3236 // none of these operations can underflow/overflow
3237 let offset = (len - n) * self.chunk_size;
3238 let start = self.v.len() - offset;
3239 let end = start + self.chunk_size;
3240 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
3241 let (tmp, tail) = unsafe { self.v.split_at_mut(end) };
3242 // SAFETY: The self.v contract ensures that any split_at_mut is valid.
3243 let (_, nth_back) = unsafe { tmp.split_at_mut(start) };
3244 self.v = tail;
3245 // SAFETY: Nothing else points to or will point to the contents of this slice.
3246 Some(unsafe { &mut *nth_back })
3247 }
3248 }
3249}
3250
3251#[stable(feature = "rchunks", since = "1.31.0")]
3252impl<T> ExactSizeIterator for RChunksExactMut<'_, T> {
3253 fn is_empty(&self) -> bool {
3254 self.v.is_empty()
3255 }
3256}
3257
3258#[unstable(feature = "trusted_len", issue = "37572")]
3259unsafe impl<T> TrustedLen for RChunksExactMut<'_, T> {}
3260
3261#[stable(feature = "rchunks", since = "1.31.0")]
3262impl<T> FusedIterator for RChunksExactMut<'_, T> {}
3263
3264#[doc(hidden)]
3265#[unstable(feature = "trusted_random_access", issue = "none")]
3266unsafe impl<'a, T> TrustedRandomAccess for RChunksExactMut<'a, T> {}
3267
3268#[doc(hidden)]
3269#[unstable(feature = "trusted_random_access", issue = "none")]
3270unsafe impl<'a, T> TrustedRandomAccessNoCoerce for RChunksExactMut<'a, T> {
3271 const MAY_HAVE_SIDE_EFFECT: bool = false;
3272}
3273
3274#[stable(feature = "rchunks", since = "1.31.0")]
3275unsafe impl<T> Send for RChunksExactMut<'_, T> where T: Send {}
3276
3277#[stable(feature = "rchunks", since = "1.31.0")]
3278unsafe impl<T> Sync for RChunksExactMut<'_, T> where T: Sync {}
3279
3280#[doc(hidden)]
3281#[unstable(feature = "trusted_random_access", issue = "none")]
3282unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {}
3283
3284#[doc(hidden)]
3285#[unstable(feature = "trusted_random_access", issue = "none")]
3286unsafe impl<'a, T> TrustedRandomAccessNoCoerce for Iter<'a, T> {
3287 const MAY_HAVE_SIDE_EFFECT: bool = false;
3288}
3289
3290#[doc(hidden)]
3291#[unstable(feature = "trusted_random_access", issue = "none")]
3292unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> {}
3293
3294#[doc(hidden)]
3295#[unstable(feature = "trusted_random_access", issue = "none")]
3296unsafe impl<'a, T> TrustedRandomAccessNoCoerce for IterMut<'a, T> {
3297 const MAY_HAVE_SIDE_EFFECT: bool = false;
3298}
3299
3300/// An iterator over slice in (non-overlapping) chunks separated by a predicate.
3301///
3302/// This struct is created by the [`chunk_by`] method on [slices].
3303///
3304/// [`chunk_by`]: slice::chunk_by
3305/// [slices]: slice
3306#[stable(feature = "slice_group_by", since = "1.77.0")]
3307#[must_use = "iterators are lazy and do nothing unless consumed"]
3308pub struct ChunkBy<'a, T: 'a, P> {
3309 slice: &'a [T],
3310 predicate: P,
3311}
3312
3313#[stable(feature = "slice_group_by", since = "1.77.0")]
3314impl<'a, T: 'a, P> ChunkBy<'a, T, P> {
3315 pub(super) const fn new(slice: &'a [T], predicate: P) -> Self {
3316 ChunkBy { slice, predicate }
3317 }
3318}
3319
3320#[stable(feature = "slice_group_by", since = "1.77.0")]
3321impl<'a, T: 'a, P> Iterator for ChunkBy<'a, T, P>
3322where
3323 P: FnMut(&T, &T) -> bool,
3324{
3325 type Item = &'a [T];
3326
3327 #[inline]
3328 fn next(&mut self) -> Option<Self::Item> {
3329 if self.slice.is_empty() {
3330 None
3331 } else {
3332 let mut len = 1;
3333 let mut iter = self.slice.windows(2);
3334 while let Some([l, r]) = iter.next() {
3335 if (self.predicate)(l, r) { len += 1 } else { break }
3336 }
3337 let (head, tail) = self.slice.split_at(len);
3338 self.slice = tail;
3339 Some(head)
3340 }
3341 }
3342
3343 #[inline]
3344 fn size_hint(&self) -> (usize, Option<usize>) {
3345 if self.slice.is_empty() { (0, Some(0)) } else { (1, Some(self.slice.len())) }
3346 }
3347
3348 #[inline]
3349 fn last(mut self) -> Option<Self::Item> {
3350 self.next_back()
3351 }
3352}
3353
3354#[stable(feature = "slice_group_by", since = "1.77.0")]
3355impl<'a, T: 'a, P> DoubleEndedIterator for ChunkBy<'a, T, P>
3356where
3357 P: FnMut(&T, &T) -> bool,
3358{
3359 #[inline]
3360 fn next_back(&mut self) -> Option<Self::Item> {
3361 if self.slice.is_empty() {
3362 None
3363 } else {
3364 let mut len = 1;
3365 let mut iter = self.slice.windows(2);
3366 while let Some([l, r]) = iter.next_back() {
3367 if (self.predicate)(l, r) { len += 1 } else { break }
3368 }
3369 let (head, tail) = self.slice.split_at(self.slice.len() - len);
3370 self.slice = head;
3371 Some(tail)
3372 }
3373 }
3374}
3375
3376#[stable(feature = "slice_group_by", since = "1.77.0")]
3377impl<'a, T: 'a, P> FusedIterator for ChunkBy<'a, T, P> where P: FnMut(&T, &T) -> bool {}
3378
3379#[stable(feature = "slice_group_by", since = "1.77.0")]
3380impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for ChunkBy<'a, T, P> {
3381 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3382 f.debug_struct("ChunkBy").field("slice", &self.slice).finish()
3383 }
3384}
3385
3386/// An iterator over slice in (non-overlapping) mutable chunks separated
3387/// by a predicate.
3388///
3389/// This struct is created by the [`chunk_by_mut`] method on [slices].
3390///
3391/// [`chunk_by_mut`]: slice::chunk_by_mut
3392/// [slices]: slice
3393#[stable(feature = "slice_group_by", since = "1.77.0")]
3394#[must_use = "iterators are lazy and do nothing unless consumed"]
3395pub struct ChunkByMut<'a, T: 'a, P> {
3396 slice: &'a mut [T],
3397 predicate: P,
3398}
3399
3400#[stable(feature = "slice_group_by", since = "1.77.0")]
3401impl<'a, T: 'a, P> ChunkByMut<'a, T, P> {
3402 pub(super) const fn new(slice: &'a mut [T], predicate: P) -> Self {
3403 ChunkByMut { slice, predicate }
3404 }
3405}
3406
3407#[stable(feature = "slice_group_by", since = "1.77.0")]
3408impl<'a, T: 'a, P> Iterator for ChunkByMut<'a, T, P>
3409where
3410 P: FnMut(&T, &T) -> bool,
3411{
3412 type Item = &'a mut [T];
3413
3414 #[inline]
3415 fn next(&mut self) -> Option<Self::Item> {
3416 if self.slice.is_empty() {
3417 None
3418 } else {
3419 let mut len = 1;
3420 let mut iter = self.slice.windows(2);
3421 while let Some([l, r]) = iter.next() {
3422 if (self.predicate)(l, r) { len += 1 } else { break }
3423 }
3424 let slice = mem::take(&mut self.slice);
3425 let (head, tail) = slice.split_at_mut(len);
3426 self.slice = tail;
3427 Some(head)
3428 }
3429 }
3430
3431 #[inline]
3432 fn size_hint(&self) -> (usize, Option<usize>) {
3433 if self.slice.is_empty() { (0, Some(0)) } else { (1, Some(self.slice.len())) }
3434 }
3435
3436 #[inline]
3437 fn last(mut self) -> Option<Self::Item> {
3438 self.next_back()
3439 }
3440}
3441
3442#[stable(feature = "slice_group_by", since = "1.77.0")]
3443impl<'a, T: 'a, P> DoubleEndedIterator for ChunkByMut<'a, T, P>
3444where
3445 P: FnMut(&T, &T) -> bool,
3446{
3447 #[inline]
3448 fn next_back(&mut self) -> Option<Self::Item> {
3449 if self.slice.is_empty() {
3450 None
3451 } else {
3452 let mut len = 1;
3453 let mut iter = self.slice.windows(2);
3454 while let Some([l, r]) = iter.next_back() {
3455 if (self.predicate)(l, r) { len += 1 } else { break }
3456 }
3457 let slice = mem::take(&mut self.slice);
3458 let (head, tail) = slice.split_at_mut(slice.len() - len);
3459 self.slice = head;
3460 Some(tail)
3461 }
3462 }
3463}
3464
3465#[stable(feature = "slice_group_by", since = "1.77.0")]
3466impl<'a, T: 'a, P> FusedIterator for ChunkByMut<'a, T, P> where P: FnMut(&T, &T) -> bool {}
3467
3468#[stable(feature = "slice_group_by", since = "1.77.0")]
3469impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for ChunkByMut<'a, T, P> {
3470 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3471 f.debug_struct("ChunkByMut").field("slice", &self.slice).finish()
3472 }
3473}