1use core::iter::{FusedIterator, TrustedLen, TrustedRandomAccess, TrustedRandomAccessNoCoerce};
2use core::num::NonZero;
3use core::ops::Try;
4use core::{fmt, mem, slice};
5
6/// A mutable iterator over the elements of a `VecDeque`.
7///
8/// This `struct` is created by the [`iter_mut`] method on [`super::VecDeque`]. See its
9/// documentation for more.
10///
11/// [`iter_mut`]: super::VecDeque::iter_mut
12#[stable(feature = "rust1", since = "1.0.0")]
13pub struct IterMut<'a, T: 'a> {
14 i1: slice::IterMut<'a, T>,
15 i2: slice::IterMut<'a, T>,
16}
17
18impl<'a, T> IterMut<'a, T> {
19 pub(super) fn new(i1: slice::IterMut<'a, T>, i2: slice::IterMut<'a, T>) -> Self {
20 Self { i1, i2 }
21 }
22
23 /// Views the underlying data as a pair of subslices of the original data.
24 ///
25 /// The slices contain, in order, the contents of the deque not yet yielded
26 /// by the iterator.
27 ///
28 /// To avoid creating `&mut` references that alias, this is forced to
29 /// consume the iterator.
30 ///
31 /// # Examples
32 ///
33 /// ```
34 /// #![feature(vec_deque_iter_as_slices)]
35 ///
36 /// use std::collections::VecDeque;
37 ///
38 /// let mut deque = VecDeque::new();
39 /// deque.push_back(0);
40 /// deque.push_back(1);
41 /// deque.push_back(2);
42 /// deque.push_front(10);
43 /// deque.push_front(9);
44 /// deque.push_front(8);
45 ///
46 /// let mut iter = deque.iter_mut();
47 /// iter.next();
48 /// iter.next_back();
49 ///
50 /// let slices = iter.into_slices();
51 /// slices.0[0] = 42;
52 /// slices.1[0] = 24;
53 /// assert_eq!(deque.as_slices(), (&[8, 42, 10][..], &[24, 1, 2][..]));
54 /// ```
55 #[unstable(feature = "vec_deque_iter_as_slices", issue = "123947")]
56 pub fn into_slices(self) -> (&'a mut [T], &'a mut [T]) {
57 (self.i1.into_slice(), self.i2.into_slice())
58 }
59
60 /// Views the underlying data as a pair of subslices of the original data.
61 ///
62 /// The slices contain, in order, the contents of the deque not yet yielded
63 /// by the iterator.
64 ///
65 /// To avoid creating `&mut [T]` references that alias, the returned slices
66 /// borrow their lifetimes from the iterator the method is applied on.
67 ///
68 /// # Examples
69 ///
70 /// ```
71 /// #![feature(vec_deque_iter_as_slices)]
72 ///
73 /// use std::collections::VecDeque;
74 ///
75 /// let mut deque = VecDeque::new();
76 /// deque.push_back(0);
77 /// deque.push_back(1);
78 /// deque.push_back(2);
79 /// deque.push_front(10);
80 /// deque.push_front(9);
81 /// deque.push_front(8);
82 ///
83 /// let mut iter = deque.iter_mut();
84 /// iter.next();
85 /// iter.next_back();
86 ///
87 /// assert_eq!(iter.as_slices(), (&[9, 10][..], &[0, 1][..]));
88 /// ```
89 #[unstable(feature = "vec_deque_iter_as_slices", issue = "123947")]
90 pub fn as_slices(&self) -> (&[T], &[T]) {
91 (self.i1.as_slice(), self.i2.as_slice())
92 }
93
94 /// Views the underlying data as a pair of subslices of the original data.
95 ///
96 /// The slices contain, in order, the contents of the deque not yet yielded
97 /// by the iterator.
98 ///
99 /// To avoid creating `&mut [T]` references that alias, the returned slices
100 /// borrow their lifetimes from the iterator the method is applied on.
101 ///
102 /// # Examples
103 ///
104 /// ```
105 /// #![feature(vec_deque_iter_as_slices)]
106 ///
107 /// use std::collections::VecDeque;
108 ///
109 /// let mut deque = VecDeque::new();
110 /// deque.push_back(0);
111 /// deque.push_back(1);
112 /// deque.push_back(2);
113 /// deque.push_front(10);
114 /// deque.push_front(9);
115 /// deque.push_front(8);
116 ///
117 /// let mut iter = deque.iter_mut();
118 /// iter.next();
119 /// iter.next_back();
120 ///
121 /// iter.as_mut_slices().0[0] = 42;
122 /// iter.as_mut_slices().1[0] = 24;
123 /// assert_eq!(deque.as_slices(), (&[8, 42, 10][..], &[24, 1, 2][..]));
124 /// ```
125 #[unstable(feature = "vec_deque_iter_as_slices", issue = "123947")]
126 pub fn as_mut_slices(&mut self) -> (&mut [T], &mut [T]) {
127 (self.i1.as_mut_slice(), self.i2.as_mut_slice())
128 }
129}
130
131#[stable(feature = "collection_debug", since = "1.17.0")]
132impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
133 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
134 f.debug_tuple(name:"IterMut").field(&self.i1.as_slice()).field(&self.i2.as_slice()).finish()
135 }
136}
137
138#[stable(feature = "default_iters_sequel", since = "1.82.0")]
139impl<T> Default for IterMut<'_, T> {
140 /// Creates an empty `vec_deque::IterMut`.
141 ///
142 /// ```
143 /// # use std::collections::vec_deque;
144 /// let iter: vec_deque::IterMut<'_, u8> = Default::default();
145 /// assert_eq!(iter.len(), 0);
146 /// ```
147 fn default() -> Self {
148 IterMut { i1: Default::default(), i2: Default::default() }
149 }
150}
151
152#[stable(feature = "rust1", since = "1.0.0")]
153impl<'a, T> Iterator for IterMut<'a, T> {
154 type Item = &'a mut T;
155
156 #[inline]
157 fn next(&mut self) -> Option<&'a mut T> {
158 match self.i1.next() {
159 Some(val) => Some(val),
160 None => {
161 // most of the time, the iterator will either always
162 // call next(), or always call next_back(). By swapping
163 // the iterators once the first one is empty, we ensure
164 // that the first branch is taken as often as possible,
165 // without sacrificing correctness, as i1 is empty anyways
166 mem::swap(&mut self.i1, &mut self.i2);
167 self.i1.next()
168 }
169 }
170 }
171
172 fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
173 match self.i1.advance_by(n) {
174 Ok(()) => Ok(()),
175 Err(remaining) => {
176 mem::swap(&mut self.i1, &mut self.i2);
177 self.i1.advance_by(remaining.get())
178 }
179 }
180 }
181
182 #[inline]
183 fn size_hint(&self) -> (usize, Option<usize>) {
184 let len = self.len();
185 (len, Some(len))
186 }
187
188 fn fold<Acc, F>(self, accum: Acc, mut f: F) -> Acc
189 where
190 F: FnMut(Acc, Self::Item) -> Acc,
191 {
192 let accum = self.i1.fold(accum, &mut f);
193 self.i2.fold(accum, &mut f)
194 }
195
196 fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R
197 where
198 F: FnMut(B, Self::Item) -> R,
199 R: Try<Output = B>,
200 {
201 let acc = self.i1.try_fold(init, &mut f)?;
202 self.i2.try_fold(acc, &mut f)
203 }
204
205 #[inline]
206 fn last(mut self) -> Option<&'a mut T> {
207 self.next_back()
208 }
209
210 #[inline]
211 unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item {
212 // Safety: The TrustedRandomAccess contract requires that callers only pass an index
213 // that is in bounds.
214 unsafe {
215 let i1_len = self.i1.len();
216 if idx < i1_len {
217 self.i1.__iterator_get_unchecked(idx)
218 } else {
219 self.i2.__iterator_get_unchecked(idx - i1_len)
220 }
221 }
222 }
223}
224
225#[stable(feature = "rust1", since = "1.0.0")]
226impl<'a, T> DoubleEndedIterator for IterMut<'a, T> {
227 #[inline]
228 fn next_back(&mut self) -> Option<&'a mut T> {
229 match self.i2.next_back() {
230 Some(val) => Some(val),
231 None => {
232 // most of the time, the iterator will either always
233 // call next(), or always call next_back(). By swapping
234 // the iterators once the first one is empty, we ensure
235 // that the first branch is taken as often as possible,
236 // without sacrificing correctness, as i2 is empty anyways
237 mem::swap(&mut self.i1, &mut self.i2);
238 self.i2.next_back()
239 }
240 }
241 }
242
243 fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
244 match self.i2.advance_back_by(n) {
245 Ok(()) => Ok(()),
246 Err(remaining) => {
247 mem::swap(&mut self.i1, &mut self.i2);
248 self.i2.advance_back_by(remaining.get())
249 }
250 }
251 }
252
253 fn rfold<Acc, F>(self, accum: Acc, mut f: F) -> Acc
254 where
255 F: FnMut(Acc, Self::Item) -> Acc,
256 {
257 let accum = self.i2.rfold(accum, &mut f);
258 self.i1.rfold(accum, &mut f)
259 }
260
261 fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R
262 where
263 F: FnMut(B, Self::Item) -> R,
264 R: Try<Output = B>,
265 {
266 let acc = self.i2.try_rfold(init, &mut f)?;
267 self.i1.try_rfold(acc, &mut f)
268 }
269}
270
271#[stable(feature = "rust1", since = "1.0.0")]
272impl<T> ExactSizeIterator for IterMut<'_, T> {
273 fn len(&self) -> usize {
274 self.i1.len() + self.i2.len()
275 }
276
277 fn is_empty(&self) -> bool {
278 self.i1.is_empty() && self.i2.is_empty()
279 }
280}
281
282#[stable(feature = "fused", since = "1.26.0")]
283impl<T> FusedIterator for IterMut<'_, T> {}
284
285#[unstable(feature = "trusted_len", issue = "37572")]
286unsafe impl<T> TrustedLen for IterMut<'_, T> {}
287
288#[doc(hidden)]
289#[unstable(feature = "trusted_random_access", issue = "none")]
290unsafe impl<T> TrustedRandomAccess for IterMut<'_, T> {}
291
292#[doc(hidden)]
293#[unstable(feature = "trusted_random_access", issue = "none")]
294unsafe impl<T> TrustedRandomAccessNoCoerce for IterMut<'_, T> {
295 const MAY_HAVE_SIDE_EFFECT: bool = false;
296}
297