1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! VecDeque is a double-ended queue, which is implemented with the help of a
12 //! growing ring buffer.
14 //! This queue has `O(1)` amortized inserts and removals from both ends of the
15 //! container. It also has `O(1)` indexing like a vector. The contained elements
16 //! are not required to be copyable, and the queue will be sendable if the
17 //! contained type is sendable.
19 #![stable(feature = "rust1", since = "1.0.0")]
21 use core::cmp::Ordering;
23 use core::iter::{repeat, FromIterator, FusedIterator};
25 use core::ops::{Index, IndexMut};
27 use core::ptr::Shared;
30 use core::hash::{Hash, Hasher};
33 use alloc::raw_vec::RawVec;
35 use super::range::RangeArgument;
36 use Bound::{Excluded, Included, Unbounded};
39 const INITIAL_CAPACITY: usize = 7; // 2^3 - 1
40 const MINIMUM_CAPACITY: usize = 1; // 2 - 1
41 #[cfg(target_pointer_width = "32")]
42 const MAXIMUM_ZST_CAPACITY: usize = 1 << (32 - 1); // Largest possible power of two
43 #[cfg(target_pointer_width = "64")]
44 const MAXIMUM_ZST_CAPACITY: usize = 1 << (64 - 1); // Largest possible power of two
46 /// `VecDeque` is a growable ring buffer, which can be used as a double-ended
47 /// queue efficiently.
49 /// The "default" usage of this type as a queue is to use `push_back` to add to
50 /// the queue, and `pop_front` to remove from the queue. `extend` and `append`
51 /// push onto the back in this manner, and iterating over `VecDeque` goes front
53 #[stable(feature = "rust1", since = "1.0.0")]
54 pub struct VecDeque<T> {
55 // tail and head are pointers into the buffer. Tail always points
56 // to the first element that could be read, Head always points
57 // to where data should be written.
58 // If tail == head the buffer is empty. The length of the ringbuffer
59 // is defined as the distance between the two.
65 #[stable(feature = "rust1", since = "1.0.0")]
66 impl<T: Clone> Clone for VecDeque<T> {
67 fn clone(&self) -> VecDeque<T> {
68 self.iter().cloned().collect()
72 #[stable(feature = "rust1", since = "1.0.0")]
73 unsafe impl<#[may_dangle] T> Drop for VecDeque<T> {
75 let (front, back) = self.as_mut_slices();
78 ptr::drop_in_place(front);
79 ptr::drop_in_place(back);
81 // RawVec handles deallocation
85 #[stable(feature = "rust1", since = "1.0.0")]
86 impl<T> Default for VecDeque<T> {
87 /// Creates an empty `VecDeque<T>`.
89 fn default() -> VecDeque<T> {
95 /// Marginally more convenient
97 fn ptr(&self) -> *mut T {
101 /// Marginally more convenient
103 fn cap(&self) -> usize {
104 if mem::size_of::<T>() == 0 {
105 // For zero sized types, we are always at maximum capacity
112 /// Turn ptr into a slice
114 unsafe fn buffer_as_slice(&self) -> &[T] {
115 slice::from_raw_parts(self.ptr(), self.cap())
118 /// Turn ptr into a mut slice
120 unsafe fn buffer_as_mut_slice(&mut self) -> &mut [T] {
121 slice::from_raw_parts_mut(self.ptr(), self.cap())
124 /// Moves an element out of the buffer
126 unsafe fn buffer_read(&mut self, off: usize) -> T {
127 ptr::read(self.ptr().offset(off as isize))
130 /// Writes an element into the buffer, moving it.
132 unsafe fn buffer_write(&mut self, off: usize, value: T) {
133 ptr::write(self.ptr().offset(off as isize), value);
136 /// Returns true if and only if the buffer is at capacity
138 fn is_full(&self) -> bool {
139 self.cap() - self.len() == 1
142 /// Returns the index in the underlying buffer for a given logical element
145 fn wrap_index(&self, idx: usize) -> usize {
146 wrap_index(idx, self.cap())
149 /// Returns the index in the underlying buffer for a given logical element
152 fn wrap_add(&self, idx: usize, addend: usize) -> usize {
153 wrap_index(idx.wrapping_add(addend), self.cap())
156 /// Returns the index in the underlying buffer for a given logical element
157 /// index - subtrahend.
159 fn wrap_sub(&self, idx: usize, subtrahend: usize) -> usize {
160 wrap_index(idx.wrapping_sub(subtrahend), self.cap())
163 /// Copies a contiguous block of memory len long from src to dst
165 unsafe fn copy(&self, dst: usize, src: usize, len: usize) {
166 debug_assert!(dst + len <= self.cap(),
167 "cpy dst={} src={} len={} cap={}",
172 debug_assert!(src + len <= self.cap(),
173 "cpy dst={} src={} len={} cap={}",
178 ptr::copy(self.ptr().offset(src as isize),
179 self.ptr().offset(dst as isize),
183 /// Copies a contiguous block of memory len long from src to dst
185 unsafe fn copy_nonoverlapping(&self, dst: usize, src: usize, len: usize) {
186 debug_assert!(dst + len <= self.cap(),
187 "cno dst={} src={} len={} cap={}",
192 debug_assert!(src + len <= self.cap(),
193 "cno dst={} src={} len={} cap={}",
198 ptr::copy_nonoverlapping(self.ptr().offset(src as isize),
199 self.ptr().offset(dst as isize),
203 /// Copies a potentially wrapping block of memory len long from src to dest.
204 /// (abs(dst - src) + len) must be no larger than cap() (There must be at
205 /// most one continuous overlapping region between src and dest).
206 unsafe fn wrap_copy(&self, dst: usize, src: usize, len: usize) {
208 fn diff(a: usize, b: usize) -> usize {
209 if a <= b { b - a } else { a - b }
211 debug_assert!(cmp::min(diff(dst, src), self.cap() - diff(dst, src)) + len <= self.cap(),
212 "wrc dst={} src={} len={} cap={}",
218 if src == dst || len == 0 {
222 let dst_after_src = self.wrap_sub(dst, src) < len;
224 let src_pre_wrap_len = self.cap() - src;
225 let dst_pre_wrap_len = self.cap() - dst;
226 let src_wraps = src_pre_wrap_len < len;
227 let dst_wraps = dst_pre_wrap_len < len;
229 match (dst_after_src, src_wraps, dst_wraps) {
230 (_, false, false) => {
231 // src doesn't wrap, dst doesn't wrap
234 // 1 [_ _ A A B B C C _]
235 // 2 [_ _ A A A A B B _]
238 self.copy(dst, src, len);
240 (false, false, true) => {
241 // dst before src, src doesn't wrap, dst wraps
244 // 1 [A A B B _ _ _ C C]
245 // 2 [A A B B _ _ _ A A]
246 // 3 [B B B B _ _ _ A A]
249 self.copy(dst, src, dst_pre_wrap_len);
250 self.copy(0, src + dst_pre_wrap_len, len - dst_pre_wrap_len);
252 (true, false, true) => {
253 // src before dst, src doesn't wrap, dst wraps
256 // 1 [C C _ _ _ A A B B]
257 // 2 [B B _ _ _ A A B B]
258 // 3 [B B _ _ _ A A A A]
261 self.copy(0, src + dst_pre_wrap_len, len - dst_pre_wrap_len);
262 self.copy(dst, src, dst_pre_wrap_len);
264 (false, true, false) => {
265 // dst before src, src wraps, dst doesn't wrap
268 // 1 [C C _ _ _ A A B B]
269 // 2 [C C _ _ _ B B B B]
270 // 3 [C C _ _ _ B B C C]
273 self.copy(dst, src, src_pre_wrap_len);
274 self.copy(dst + src_pre_wrap_len, 0, len - src_pre_wrap_len);
276 (true, true, false) => {
277 // src before dst, src wraps, dst doesn't wrap
280 // 1 [A A B B _ _ _ C C]
281 // 2 [A A A A _ _ _ C C]
282 // 3 [C C A A _ _ _ C C]
285 self.copy(dst + src_pre_wrap_len, 0, len - src_pre_wrap_len);
286 self.copy(dst, src, src_pre_wrap_len);
288 (false, true, true) => {
289 // dst before src, src wraps, dst wraps
292 // 1 [A B C D _ E F G H]
293 // 2 [A B C D _ E G H H]
294 // 3 [A B C D _ E G H A]
295 // 4 [B C C D _ E G H A]
298 debug_assert!(dst_pre_wrap_len > src_pre_wrap_len);
299 let delta = dst_pre_wrap_len - src_pre_wrap_len;
300 self.copy(dst, src, src_pre_wrap_len);
301 self.copy(dst + src_pre_wrap_len, 0, delta);
302 self.copy(0, delta, len - dst_pre_wrap_len);
304 (true, true, true) => {
305 // src before dst, src wraps, dst wraps
308 // 1 [A B C D _ E F G H]
309 // 2 [A A B D _ E F G H]
310 // 3 [H A B D _ E F G H]
311 // 4 [H A B D _ E F F G]
314 debug_assert!(src_pre_wrap_len > dst_pre_wrap_len);
315 let delta = src_pre_wrap_len - dst_pre_wrap_len;
316 self.copy(delta, 0, len - src_pre_wrap_len);
317 self.copy(0, self.cap() - delta, delta);
318 self.copy(dst, src, dst_pre_wrap_len);
323 /// Frobs the head and tail sections around to handle the fact that we
324 /// just reallocated. Unsafe because it trusts old_cap.
326 unsafe fn handle_cap_increase(&mut self, old_cap: usize) {
327 let new_cap = self.cap();
329 // Move the shortest contiguous section of the ring buffer
331 // [o o o o o o o . ]
333 // A [o o o o o o o . . . . . . . . . ]
335 // [o o . o o o o o ]
337 // B [. . . o o o o o o o . . . . . . ]
339 // [o o o o o . o o ]
341 // C [o o o o o . . . . . . . . . o o ]
343 if self.tail <= self.head {
346 } else if self.head < old_cap - self.tail {
348 self.copy_nonoverlapping(old_cap, 0, self.head);
349 self.head += old_cap;
350 debug_assert!(self.head > self.tail);
353 let new_tail = new_cap - (old_cap - self.tail);
354 self.copy_nonoverlapping(new_tail, self.tail, old_cap - self.tail);
355 self.tail = new_tail;
356 debug_assert!(self.head < self.tail);
358 debug_assert!(self.head < self.cap());
359 debug_assert!(self.tail < self.cap());
360 debug_assert!(self.cap().count_ones() == 1);
364 impl<T> VecDeque<T> {
365 /// Creates an empty `VecDeque`.
370 /// use std::collections::VecDeque;
372 /// let vector: VecDeque<u32> = VecDeque::new();
374 #[stable(feature = "rust1", since = "1.0.0")]
375 pub fn new() -> VecDeque<T> {
376 VecDeque::with_capacity(INITIAL_CAPACITY)
379 /// Creates an empty `VecDeque` with space for at least `n` elements.
384 /// use std::collections::VecDeque;
386 /// let vector: VecDeque<u32> = VecDeque::with_capacity(10);
388 #[stable(feature = "rust1", since = "1.0.0")]
389 pub fn with_capacity(n: usize) -> VecDeque<T> {
390 // +1 since the ringbuffer always leaves one space empty
391 let cap = cmp::max(n + 1, MINIMUM_CAPACITY + 1).next_power_of_two();
392 assert!(cap > n, "capacity overflow");
397 buf: RawVec::with_capacity(cap),
401 /// Retrieves an element in the `VecDeque` by index.
403 /// Element at index 0 is the front of the queue.
408 /// use std::collections::VecDeque;
410 /// let mut buf = VecDeque::new();
411 /// buf.push_back(3);
412 /// buf.push_back(4);
413 /// buf.push_back(5);
414 /// assert_eq!(buf.get(1), Some(&4));
416 #[stable(feature = "rust1", since = "1.0.0")]
417 pub fn get(&self, index: usize) -> Option<&T> {
418 if index < self.len() {
419 let idx = self.wrap_add(self.tail, index);
420 unsafe { Some(&*self.ptr().offset(idx as isize)) }
426 /// Retrieves an element in the `VecDeque` mutably by index.
428 /// Element at index 0 is the front of the queue.
433 /// use std::collections::VecDeque;
435 /// let mut buf = VecDeque::new();
436 /// buf.push_back(3);
437 /// buf.push_back(4);
438 /// buf.push_back(5);
439 /// if let Some(elem) = buf.get_mut(1) {
443 /// assert_eq!(buf[1], 7);
445 #[stable(feature = "rust1", since = "1.0.0")]
446 pub fn get_mut(&mut self, index: usize) -> Option<&mut T> {
447 if index < self.len() {
448 let idx = self.wrap_add(self.tail, index);
449 unsafe { Some(&mut *self.ptr().offset(idx as isize)) }
455 /// Swaps elements at indices `i` and `j`.
457 /// `i` and `j` may be equal.
459 /// Fails if there is no element with either index.
461 /// Element at index 0 is the front of the queue.
466 /// use std::collections::VecDeque;
468 /// let mut buf = VecDeque::new();
469 /// buf.push_back(3);
470 /// buf.push_back(4);
471 /// buf.push_back(5);
472 /// assert_eq!(buf, [3, 4, 5]);
474 /// assert_eq!(buf, [5, 4, 3]);
476 #[stable(feature = "rust1", since = "1.0.0")]
477 pub fn swap(&mut self, i: usize, j: usize) {
478 assert!(i < self.len());
479 assert!(j < self.len());
480 let ri = self.wrap_add(self.tail, i);
481 let rj = self.wrap_add(self.tail, j);
483 ptr::swap(self.ptr().offset(ri as isize),
484 self.ptr().offset(rj as isize))
488 /// Returns the number of elements the `VecDeque` can hold without
494 /// use std::collections::VecDeque;
496 /// let buf: VecDeque<i32> = VecDeque::with_capacity(10);
497 /// assert!(buf.capacity() >= 10);
500 #[stable(feature = "rust1", since = "1.0.0")]
501 pub fn capacity(&self) -> usize {
505 /// Reserves the minimum capacity for exactly `additional` more elements to be inserted in the
506 /// given `VecDeque`. Does nothing if the capacity is already sufficient.
508 /// Note that the allocator may give the collection more space than it requests. Therefore
509 /// capacity can not be relied upon to be precisely minimal. Prefer `reserve` if future
510 /// insertions are expected.
514 /// Panics if the new capacity overflows `usize`.
519 /// use std::collections::VecDeque;
521 /// let mut buf: VecDeque<i32> = vec![1].into_iter().collect();
522 /// buf.reserve_exact(10);
523 /// assert!(buf.capacity() >= 11);
525 #[stable(feature = "rust1", since = "1.0.0")]
526 pub fn reserve_exact(&mut self, additional: usize) {
527 self.reserve(additional);
530 /// Reserves capacity for at least `additional` more elements to be inserted in the given
531 /// `VecDeque`. The collection may reserve more space to avoid frequent reallocations.
535 /// Panics if the new capacity overflows `usize`.
540 /// use std::collections::VecDeque;
542 /// let mut buf: VecDeque<i32> = vec![1].into_iter().collect();
544 /// assert!(buf.capacity() >= 11);
546 #[stable(feature = "rust1", since = "1.0.0")]
547 pub fn reserve(&mut self, additional: usize) {
548 let old_cap = self.cap();
549 let used_cap = self.len() + 1;
550 let new_cap = used_cap.checked_add(additional)
551 .and_then(|needed_cap| needed_cap.checked_next_power_of_two())
552 .expect("capacity overflow");
554 if new_cap > self.capacity() {
555 self.buf.reserve_exact(used_cap, new_cap - used_cap);
557 self.handle_cap_increase(old_cap);
562 /// Shrinks the capacity of the `VecDeque` as much as possible.
564 /// It will drop down as close as possible to the length but the allocator may still inform the
565 /// `VecDeque` that there is space for a few more elements.
570 /// use std::collections::VecDeque;
572 /// let mut buf = VecDeque::with_capacity(15);
573 /// buf.extend(0..4);
574 /// assert_eq!(buf.capacity(), 15);
575 /// buf.shrink_to_fit();
576 /// assert!(buf.capacity() >= 4);
578 #[stable(feature = "deque_extras_15", since = "1.5.0")]
579 pub fn shrink_to_fit(&mut self) {
580 // +1 since the ringbuffer always leaves one space empty
581 // len + 1 can't overflow for an existing, well-formed ringbuffer.
582 let target_cap = cmp::max(self.len() + 1, MINIMUM_CAPACITY + 1).next_power_of_two();
583 if target_cap < self.cap() {
584 // There are three cases of interest:
585 // All elements are out of desired bounds
586 // Elements are contiguous, and head is out of desired bounds
587 // Elements are discontiguous, and tail is out of desired bounds
589 // At all other times, element positions are unaffected.
591 // Indicates that elements at the head should be moved.
592 let head_outside = self.head == 0 || self.head >= target_cap;
593 // Move elements from out of desired bounds (positions after target_cap)
594 if self.tail >= target_cap && head_outside {
596 // [. . . . . . . . o o o o o o o . ]
598 // [o o o o o o o . ]
600 self.copy_nonoverlapping(0, self.tail, self.len());
602 self.head = self.len();
604 } else if self.tail != 0 && self.tail < target_cap && head_outside {
606 // [. . . o o o o o o o . . . . . . ]
608 // [o o . o o o o o ]
609 let len = self.wrap_sub(self.head, target_cap);
611 self.copy_nonoverlapping(0, target_cap, len);
614 debug_assert!(self.head < self.tail);
615 } else if self.tail >= target_cap {
617 // [o o o o o . . . . . . . . . o o ]
619 // [o o o o o . o o ]
620 debug_assert!(self.wrap_sub(self.head, 1) < target_cap);
621 let len = self.cap() - self.tail;
622 let new_tail = target_cap - len;
624 self.copy_nonoverlapping(new_tail, self.tail, len);
626 self.tail = new_tail;
627 debug_assert!(self.head < self.tail);
630 self.buf.shrink_to_fit(target_cap);
632 debug_assert!(self.head < self.cap());
633 debug_assert!(self.tail < self.cap());
634 debug_assert!(self.cap().count_ones() == 1);
638 /// Shortens a `VecDeque`, dropping excess elements from the back.
640 /// If `len` is greater than the `VecDeque`'s current length, this has no
646 /// use std::collections::VecDeque;
648 /// let mut buf = VecDeque::new();
649 /// buf.push_back(5);
650 /// buf.push_back(10);
651 /// buf.push_back(15);
652 /// assert_eq!(buf, [5, 10, 15]);
654 /// assert_eq!(buf, [5]);
656 #[stable(feature = "deque_extras", since = "1.16.0")]
657 pub fn truncate(&mut self, len: usize) {
658 for _ in len..self.len() {
663 /// Returns a front-to-back iterator.
668 /// use std::collections::VecDeque;
670 /// let mut buf = VecDeque::new();
671 /// buf.push_back(5);
672 /// buf.push_back(3);
673 /// buf.push_back(4);
674 /// let b: &[_] = &[&5, &3, &4];
675 /// let c: Vec<&i32> = buf.iter().collect();
676 /// assert_eq!(&c[..], b);
678 #[stable(feature = "rust1", since = "1.0.0")]
679 pub fn iter(&self) -> Iter<T> {
683 ring: unsafe { self.buffer_as_slice() },
687 /// Returns a front-to-back iterator that returns mutable references.
692 /// use std::collections::VecDeque;
694 /// let mut buf = VecDeque::new();
695 /// buf.push_back(5);
696 /// buf.push_back(3);
697 /// buf.push_back(4);
698 /// for num in buf.iter_mut() {
701 /// let b: &[_] = &[&mut 3, &mut 1, &mut 2];
702 /// assert_eq!(&buf.iter_mut().collect::<Vec<&mut i32>>()[..], b);
704 #[stable(feature = "rust1", since = "1.0.0")]
705 pub fn iter_mut(&mut self) -> IterMut<T> {
709 ring: unsafe { self.buffer_as_mut_slice() },
713 /// Returns a pair of slices which contain, in order, the contents of the
719 /// use std::collections::VecDeque;
721 /// let mut vector = VecDeque::new();
723 /// vector.push_back(0);
724 /// vector.push_back(1);
725 /// vector.push_back(2);
727 /// assert_eq!(vector.as_slices(), (&[0, 1, 2][..], &[][..]));
729 /// vector.push_front(10);
730 /// vector.push_front(9);
732 /// assert_eq!(vector.as_slices(), (&[9, 10][..], &[0, 1, 2][..]));
735 #[stable(feature = "deque_extras_15", since = "1.5.0")]
736 pub fn as_slices(&self) -> (&[T], &[T]) {
738 let buf = self.buffer_as_slice();
739 RingSlices::ring_slices(buf, self.head, self.tail)
743 /// Returns a pair of slices which contain, in order, the contents of the
749 /// use std::collections::VecDeque;
751 /// let mut vector = VecDeque::new();
753 /// vector.push_back(0);
754 /// vector.push_back(1);
756 /// vector.push_front(10);
757 /// vector.push_front(9);
759 /// vector.as_mut_slices().0[0] = 42;
760 /// vector.as_mut_slices().1[0] = 24;
761 /// assert_eq!(vector.as_slices(), (&[42, 10][..], &[24, 1][..]));
764 #[stable(feature = "deque_extras_15", since = "1.5.0")]
765 pub fn as_mut_slices(&mut self) -> (&mut [T], &mut [T]) {
767 let head = self.head;
768 let tail = self.tail;
769 let buf = self.buffer_as_mut_slice();
770 RingSlices::ring_slices(buf, head, tail)
774 /// Returns the number of elements in the `VecDeque`.
779 /// use std::collections::VecDeque;
781 /// let mut v = VecDeque::new();
782 /// assert_eq!(v.len(), 0);
784 /// assert_eq!(v.len(), 1);
786 #[stable(feature = "rust1", since = "1.0.0")]
787 pub fn len(&self) -> usize {
788 count(self.tail, self.head, self.cap())
791 /// Returns true if the buffer contains no elements
796 /// use std::collections::VecDeque;
798 /// let mut v = VecDeque::new();
799 /// assert!(v.is_empty());
801 /// assert!(!v.is_empty());
803 #[stable(feature = "rust1", since = "1.0.0")]
804 pub fn is_empty(&self) -> bool {
805 self.tail == self.head
808 /// Create a draining iterator that removes the specified range in the
809 /// `VecDeque` and yields the removed items.
811 /// Note 1: The element range is removed even if the iterator is not
812 /// consumed until the end.
814 /// Note 2: It is unspecified how many elements are removed from the deque,
815 /// if the `Drain` value is not dropped, but the borrow it holds expires
816 /// (eg. due to mem::forget).
820 /// Panics if the starting point is greater than the end point or if
821 /// the end point is greater than the length of the vector.
826 /// use std::collections::VecDeque;
828 /// let mut v: VecDeque<_> = vec![1, 2, 3].into_iter().collect();
829 /// let drained = v.drain(2..).collect::<VecDeque<_>>();
830 /// assert_eq!(drained, [3]);
831 /// assert_eq!(v, [1, 2]);
833 /// // A full range clears all contents
835 /// assert!(v.is_empty());
838 #[stable(feature = "drain", since = "1.6.0")]
839 pub fn drain<R>(&mut self, range: R) -> Drain<T>
840 where R: RangeArgument<usize>
844 // When the Drain is first created, the source deque is shortened to
845 // make sure no uninitialized or moved-from elements are accessible at
846 // all if the Drain's destructor never gets to run.
848 // Drain will ptr::read out the values to remove.
849 // When finished, the remaining data will be copied back to cover the hole,
850 // and the head/tail values will be restored correctly.
852 let len = self.len();
853 let start = match range.start() {
855 Excluded(&n) => n + 1,
858 let end = match range.end() {
859 Included(&n) => n + 1,
863 assert!(start <= end, "drain lower bound was too large");
864 assert!(end <= len, "drain upper bound was too large");
866 // The deque's elements are parted into three segments:
867 // * self.tail -> drain_tail
868 // * drain_tail -> drain_head
869 // * drain_head -> self.head
871 // T = self.tail; H = self.head; t = drain_tail; h = drain_head
873 // We store drain_tail as self.head, and drain_head and self.head as
874 // after_tail and after_head respectively on the Drain. This also
875 // truncates the effective array such that if the Drain is leaked, we
876 // have forgotten about the potentially moved values after the start of
880 // [. . . o o x x o o . . .]
882 let drain_tail = self.wrap_add(self.tail, start);
883 let drain_head = self.wrap_add(self.tail, end);
884 let head = self.head;
886 // "forget" about the values after the start of the drain until after
887 // the drain is complete and the Drain destructor is run.
888 self.head = drain_tail;
891 deque: unsafe { Shared::new(self as *mut _) },
892 after_tail: drain_head,
897 ring: unsafe { self.buffer_as_mut_slice() },
902 /// Clears the buffer, removing all values.
907 /// use std::collections::VecDeque;
909 /// let mut v = VecDeque::new();
912 /// assert!(v.is_empty());
914 #[stable(feature = "rust1", since = "1.0.0")]
916 pub fn clear(&mut self) {
920 /// Returns `true` if the `VecDeque` contains an element equal to the
926 /// use std::collections::VecDeque;
928 /// let mut vector: VecDeque<u32> = VecDeque::new();
930 /// vector.push_back(0);
931 /// vector.push_back(1);
933 /// assert_eq!(vector.contains(&1), true);
934 /// assert_eq!(vector.contains(&10), false);
936 #[stable(feature = "vec_deque_contains", since = "1.12.0")]
937 pub fn contains(&self, x: &T) -> bool
938 where T: PartialEq<T>
940 let (a, b) = self.as_slices();
941 a.contains(x) || b.contains(x)
944 /// Provides a reference to the front element, or `None` if the sequence is
950 /// use std::collections::VecDeque;
952 /// let mut d = VecDeque::new();
953 /// assert_eq!(d.front(), None);
957 /// assert_eq!(d.front(), Some(&1));
959 #[stable(feature = "rust1", since = "1.0.0")]
960 pub fn front(&self) -> Option<&T> {
961 if !self.is_empty() {
968 /// Provides a mutable reference to the front element, or `None` if the
969 /// sequence is empty.
974 /// use std::collections::VecDeque;
976 /// let mut d = VecDeque::new();
977 /// assert_eq!(d.front_mut(), None);
981 /// match d.front_mut() {
982 /// Some(x) => *x = 9,
985 /// assert_eq!(d.front(), Some(&9));
987 #[stable(feature = "rust1", since = "1.0.0")]
988 pub fn front_mut(&mut self) -> Option<&mut T> {
989 if !self.is_empty() {
996 /// Provides a reference to the back element, or `None` if the sequence is
1002 /// use std::collections::VecDeque;
1004 /// let mut d = VecDeque::new();
1005 /// assert_eq!(d.back(), None);
1009 /// assert_eq!(d.back(), Some(&2));
1011 #[stable(feature = "rust1", since = "1.0.0")]
1012 pub fn back(&self) -> Option<&T> {
1013 if !self.is_empty() {
1014 Some(&self[self.len() - 1])
1020 /// Provides a mutable reference to the back element, or `None` if the
1021 /// sequence is empty.
1026 /// use std::collections::VecDeque;
1028 /// let mut d = VecDeque::new();
1029 /// assert_eq!(d.back(), None);
1033 /// match d.back_mut() {
1034 /// Some(x) => *x = 9,
1037 /// assert_eq!(d.back(), Some(&9));
1039 #[stable(feature = "rust1", since = "1.0.0")]
1040 pub fn back_mut(&mut self) -> Option<&mut T> {
1041 let len = self.len();
1042 if !self.is_empty() {
1043 Some(&mut self[len - 1])
1049 /// Removes the first element and returns it, or `None` if the sequence is
1055 /// use std::collections::VecDeque;
1057 /// let mut d = VecDeque::new();
1061 /// assert_eq!(d.pop_front(), Some(1));
1062 /// assert_eq!(d.pop_front(), Some(2));
1063 /// assert_eq!(d.pop_front(), None);
1065 #[stable(feature = "rust1", since = "1.0.0")]
1066 pub fn pop_front(&mut self) -> Option<T> {
1067 if self.is_empty() {
1070 let tail = self.tail;
1071 self.tail = self.wrap_add(self.tail, 1);
1072 unsafe { Some(self.buffer_read(tail)) }
1076 /// Inserts an element first in the sequence.
1081 /// use std::collections::VecDeque;
1083 /// let mut d = VecDeque::new();
1084 /// d.push_front(1);
1085 /// d.push_front(2);
1086 /// assert_eq!(d.front(), Some(&2));
1088 #[stable(feature = "rust1", since = "1.0.0")]
1089 pub fn push_front(&mut self, value: T) {
1091 let old_cap = self.cap();
1094 self.handle_cap_increase(old_cap);
1096 debug_assert!(!self.is_full());
1099 self.tail = self.wrap_sub(self.tail, 1);
1100 let tail = self.tail;
1102 self.buffer_write(tail, value);
1106 /// Appends an element to the back of a buffer
1111 /// use std::collections::VecDeque;
1113 /// let mut buf = VecDeque::new();
1114 /// buf.push_back(1);
1115 /// buf.push_back(3);
1116 /// assert_eq!(3, *buf.back().unwrap());
1118 #[stable(feature = "rust1", since = "1.0.0")]
1119 pub fn push_back(&mut self, value: T) {
1121 let old_cap = self.cap();
1124 self.handle_cap_increase(old_cap);
1126 debug_assert!(!self.is_full());
1129 let head = self.head;
1130 self.head = self.wrap_add(self.head, 1);
1131 unsafe { self.buffer_write(head, value) }
1134 /// Removes the last element from a buffer and returns it, or `None` if
1140 /// use std::collections::VecDeque;
1142 /// let mut buf = VecDeque::new();
1143 /// assert_eq!(buf.pop_back(), None);
1144 /// buf.push_back(1);
1145 /// buf.push_back(3);
1146 /// assert_eq!(buf.pop_back(), Some(3));
1148 #[stable(feature = "rust1", since = "1.0.0")]
1149 pub fn pop_back(&mut self) -> Option<T> {
1150 if self.is_empty() {
1153 self.head = self.wrap_sub(self.head, 1);
1154 let head = self.head;
1155 unsafe { Some(self.buffer_read(head)) }
1160 fn is_contiguous(&self) -> bool {
1161 self.tail <= self.head
1164 /// Removes an element from anywhere in the `VecDeque` and returns it, replacing it with the
1167 /// This does not preserve ordering, but is O(1).
1169 /// Returns `None` if `index` is out of bounds.
1171 /// Element at index 0 is the front of the queue.
1176 /// use std::collections::VecDeque;
1178 /// let mut buf = VecDeque::new();
1179 /// assert_eq!(buf.swap_remove_back(0), None);
1180 /// buf.push_back(1);
1181 /// buf.push_back(2);
1182 /// buf.push_back(3);
1183 /// assert_eq!(buf, [1, 2, 3]);
1185 /// assert_eq!(buf.swap_remove_back(0), Some(1));
1186 /// assert_eq!(buf, [3, 2]);
1188 #[stable(feature = "deque_extras_15", since = "1.5.0")]
1189 pub fn swap_remove_back(&mut self, index: usize) -> Option<T> {
1190 let length = self.len();
1191 if length > 0 && index < length - 1 {
1192 self.swap(index, length - 1);
1193 } else if index >= length {
1199 /// Removes an element from anywhere in the `VecDeque` and returns it,
1200 /// replacing it with the first element.
1202 /// This does not preserve ordering, but is O(1).
1204 /// Returns `None` if `index` is out of bounds.
1206 /// Element at index 0 is the front of the queue.
1211 /// use std::collections::VecDeque;
1213 /// let mut buf = VecDeque::new();
1214 /// assert_eq!(buf.swap_remove_front(0), None);
1215 /// buf.push_back(1);
1216 /// buf.push_back(2);
1217 /// buf.push_back(3);
1218 /// assert_eq!(buf, [1, 2, 3]);
1220 /// assert_eq!(buf.swap_remove_front(2), Some(3));
1221 /// assert_eq!(buf, [2, 1]);
1223 #[stable(feature = "deque_extras_15", since = "1.5.0")]
1224 pub fn swap_remove_front(&mut self, index: usize) -> Option<T> {
1225 let length = self.len();
1226 if length > 0 && index < length && index != 0 {
1227 self.swap(index, 0);
1228 } else if index >= length {
1234 /// Inserts an element at `index` within the `VecDeque`, shifting all elements with indices
1235 /// greater than or equal to `index` towards the back.
1237 /// Element at index 0 is the front of the queue.
1241 /// Panics if `index` is greater than `VecDeque`'s length
1246 /// use std::collections::VecDeque;
1248 /// let mut vec_deque = VecDeque::new();
1249 /// vec_deque.push_back('a');
1250 /// vec_deque.push_back('b');
1251 /// vec_deque.push_back('c');
1252 /// assert_eq!(vec_deque, &['a', 'b', 'c']);
1254 /// vec_deque.insert(1, 'd');
1255 /// assert_eq!(vec_deque, &['a', 'd', 'b', 'c']);
1257 #[stable(feature = "deque_extras_15", since = "1.5.0")]
1258 pub fn insert(&mut self, index: usize, value: T) {
1259 assert!(index <= self.len(), "index out of bounds");
1261 let old_cap = self.cap();
1264 self.handle_cap_increase(old_cap);
1266 debug_assert!(!self.is_full());
1269 // Move the least number of elements in the ring buffer and insert
1272 // At most len/2 - 1 elements will be moved. O(min(n, n-i))
1274 // There are three main cases:
1275 // Elements are contiguous
1276 // - special case when tail is 0
1277 // Elements are discontiguous and the insert is in the tail section
1278 // Elements are discontiguous and the insert is in the head section
1280 // For each of those there are two more cases:
1281 // Insert is closer to tail
1282 // Insert is closer to head
1284 // Key: H - self.head
1286 // o - Valid element
1287 // I - Insertion element
1288 // A - The element that should be after the insertion point
1289 // M - Indicates element was moved
1291 let idx = self.wrap_add(self.tail, index);
1293 let distance_to_tail = index;
1294 let distance_to_head = self.len() - index;
1296 let contiguous = self.is_contiguous();
1298 match (contiguous, distance_to_tail <= distance_to_head, idx >= self.tail) {
1299 (true, true, _) if index == 0 => {
1304 // [A o o o o o o . . . . . . . . .]
1307 // [A o o o o o o o . . . . . I]
1310 self.tail = self.wrap_sub(self.tail, 1);
1312 (true, true, _) => {
1314 // contiguous, insert closer to tail:
1317 // [. . . o o A o o o o . . . . . .]
1320 // [. . o o I A o o o o . . . . . .]
1323 // contiguous, insert closer to tail and tail is 0:
1327 // [o o A o o o o . . . . . . . . .]
1330 // [o I A o o o o o . . . . . . . o]
1333 let new_tail = self.wrap_sub(self.tail, 1);
1335 self.copy(new_tail, self.tail, 1);
1336 // Already moved the tail, so we only copy `index - 1` elements.
1337 self.copy(self.tail, self.tail + 1, index - 1);
1339 self.tail = new_tail;
1342 (true, false, _) => {
1344 // contiguous, insert closer to head:
1347 // [. . . o o o o A o o . . . . . .]
1350 // [. . . o o o o I A o o . . . . .]
1353 self.copy(idx + 1, idx, self.head - idx);
1354 self.head = self.wrap_add(self.head, 1);
1357 (false, true, true) => {
1359 // discontiguous, insert closer to tail, tail section:
1362 // [o o o o o o . . . . . o o A o o]
1365 // [o o o o o o . . . . o o I A o o]
1368 self.copy(self.tail - 1, self.tail, index);
1372 (false, false, true) => {
1374 // discontiguous, insert closer to head, tail section:
1377 // [o o . . . . . . . o o o o o A o]
1380 // [o o o . . . . . . o o o o o I A]
1383 // copy elements up to new head
1384 self.copy(1, 0, self.head);
1386 // copy last element into empty spot at bottom of buffer
1387 self.copy(0, self.cap() - 1, 1);
1389 // move elements from idx to end forward not including ^ element
1390 self.copy(idx + 1, idx, self.cap() - 1 - idx);
1395 (false, true, false) if idx == 0 => {
1397 // discontiguous, insert is closer to tail, head section,
1398 // and is at index zero in the internal buffer:
1401 // [A o o o o o o o o o . . . o o o]
1404 // [A o o o o o o o o o . . o o o I]
1407 // copy elements up to new tail
1408 self.copy(self.tail - 1, self.tail, self.cap() - self.tail);
1410 // copy last element into empty spot at bottom of buffer
1411 self.copy(self.cap() - 1, 0, 1);
1416 (false, true, false) => {
1418 // discontiguous, insert closer to tail, head section:
1421 // [o o o A o o o o o o . . . o o o]
1424 // [o o I A o o o o o o . . o o o o]
1427 // copy elements up to new tail
1428 self.copy(self.tail - 1, self.tail, self.cap() - self.tail);
1430 // copy last element into empty spot at bottom of buffer
1431 self.copy(self.cap() - 1, 0, 1);
1433 // move elements from idx-1 to end forward not including ^ element
1434 self.copy(0, 1, idx - 1);
1439 (false, false, false) => {
1441 // discontiguous, insert closer to head, head section:
1444 // [o o o o A o o . . . . . . o o o]
1447 // [o o o o I A o o . . . . . o o o]
1450 self.copy(idx + 1, idx, self.head - idx);
1456 // tail might've been changed so we need to recalculate
1457 let new_idx = self.wrap_add(self.tail, index);
1459 self.buffer_write(new_idx, value);
1463 /// Removes and returns the element at `index` from the `VecDeque`.
1464 /// Whichever end is closer to the removal point will be moved to make
1465 /// room, and all the affected elements will be moved to new positions.
1466 /// Returns `None` if `index` is out of bounds.
1468 /// Element at index 0 is the front of the queue.
1473 /// use std::collections::VecDeque;
1475 /// let mut buf = VecDeque::new();
1476 /// buf.push_back(1);
1477 /// buf.push_back(2);
1478 /// buf.push_back(3);
1479 /// assert_eq!(buf, [1, 2, 3]);
1481 /// assert_eq!(buf.remove(1), Some(2));
1482 /// assert_eq!(buf, [1, 3]);
1484 #[stable(feature = "rust1", since = "1.0.0")]
1485 pub fn remove(&mut self, index: usize) -> Option<T> {
1486 if self.is_empty() || self.len() <= index {
1490 // There are three main cases:
1491 // Elements are contiguous
1492 // Elements are discontiguous and the removal is in the tail section
1493 // Elements are discontiguous and the removal is in the head section
1494 // - special case when elements are technically contiguous,
1495 // but self.head = 0
1497 // For each of those there are two more cases:
1498 // Insert is closer to tail
1499 // Insert is closer to head
1501 // Key: H - self.head
1503 // o - Valid element
1504 // x - Element marked for removal
1505 // R - Indicates element that is being removed
1506 // M - Indicates element was moved
1508 let idx = self.wrap_add(self.tail, index);
1510 let elem = unsafe { Some(self.buffer_read(idx)) };
1512 let distance_to_tail = index;
1513 let distance_to_head = self.len() - index;
1515 let contiguous = self.is_contiguous();
1517 match (contiguous, distance_to_tail <= distance_to_head, idx >= self.tail) {
1518 (true, true, _) => {
1520 // contiguous, remove closer to tail:
1523 // [. . . o o x o o o o . . . . . .]
1526 // [. . . . o o o o o o . . . . . .]
1529 self.copy(self.tail + 1, self.tail, index);
1533 (true, false, _) => {
1535 // contiguous, remove closer to head:
1538 // [. . . o o o o x o o . . . . . .]
1541 // [. . . o o o o o o . . . . . . .]
1544 self.copy(idx, idx + 1, self.head - idx - 1);
1548 (false, true, true) => {
1550 // discontiguous, remove closer to tail, tail section:
1553 // [o o o o o o . . . . . o o x o o]
1556 // [o o o o o o . . . . . . o o o o]
1559 self.copy(self.tail + 1, self.tail, index);
1560 self.tail = self.wrap_add(self.tail, 1);
1563 (false, false, false) => {
1565 // discontiguous, remove closer to head, head section:
1568 // [o o o o x o o . . . . . . o o o]
1571 // [o o o o o o . . . . . . . o o o]
1574 self.copy(idx, idx + 1, self.head - idx - 1);
1578 (false, false, true) => {
1580 // discontiguous, remove closer to head, tail section:
1583 // [o o o . . . . . . o o o o o x o]
1586 // [o o . . . . . . . o o o o o o o]
1589 // or quasi-discontiguous, remove next to head, tail section:
1592 // [. . . . . . . . . o o o o o x o]
1595 // [. . . . . . . . . o o o o o o .]
1598 // draw in elements in the tail section
1599 self.copy(idx, idx + 1, self.cap() - idx - 1);
1601 // Prevents underflow.
1603 // copy first element into empty spot
1604 self.copy(self.cap() - 1, 0, 1);
1606 // move elements in the head section backwards
1607 self.copy(0, 1, self.head - 1);
1610 self.head = self.wrap_sub(self.head, 1);
1613 (false, true, false) => {
1615 // discontiguous, remove closer to tail, head section:
1618 // [o o x o o o o o o o . . . o o o]
1621 // [o o o o o o o o o o . . . . o o]
1624 // draw in elements up to idx
1625 self.copy(1, 0, idx);
1627 // copy last element into empty spot
1628 self.copy(0, self.cap() - 1, 1);
1630 // move elements from tail to end forward, excluding the last one
1631 self.copy(self.tail + 1, self.tail, self.cap() - self.tail - 1);
1633 self.tail = self.wrap_add(self.tail, 1);
1641 /// Splits the collection into two at the given index.
1643 /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`,
1644 /// and the returned `Self` contains elements `[at, len)`.
1646 /// Note that the capacity of `self` does not change.
1648 /// Element at index 0 is the front of the queue.
1652 /// Panics if `at > len`
1657 /// use std::collections::VecDeque;
1659 /// let mut buf: VecDeque<_> = vec![1,2,3].into_iter().collect();
1660 /// let buf2 = buf.split_off(1);
1661 /// assert_eq!(buf, [1]);
1662 /// assert_eq!(buf2, [2, 3]);
1665 #[stable(feature = "split_off", since = "1.4.0")]
1666 pub fn split_off(&mut self, at: usize) -> Self {
1667 let len = self.len();
1668 assert!(at <= len, "`at` out of bounds");
1670 let other_len = len - at;
1671 let mut other = VecDeque::with_capacity(other_len);
1674 let (first_half, second_half) = self.as_slices();
1676 let first_len = first_half.len();
1677 let second_len = second_half.len();
1679 // `at` lies in the first half.
1680 let amount_in_first = first_len - at;
1682 ptr::copy_nonoverlapping(first_half.as_ptr().offset(at as isize),
1686 // just take all of the second half.
1687 ptr::copy_nonoverlapping(second_half.as_ptr(),
1688 other.ptr().offset(amount_in_first as isize),
1691 // `at` lies in the second half, need to factor in the elements we skipped
1692 // in the first half.
1693 let offset = at - first_len;
1694 let amount_in_second = second_len - offset;
1695 ptr::copy_nonoverlapping(second_half.as_ptr().offset(offset as isize),
1701 // Cleanup where the ends of the buffers are
1702 self.head = self.wrap_sub(self.head, other_len);
1703 other.head = other.wrap_index(other_len);
1708 /// Moves all the elements of `other` into `Self`, leaving `other` empty.
1712 /// Panics if the new number of elements in self overflows a `usize`.
1717 /// use std::collections::VecDeque;
1719 /// let mut buf: VecDeque<_> = vec![1, 2].into_iter().collect();
1720 /// let mut buf2: VecDeque<_> = vec![3, 4].into_iter().collect();
1721 /// buf.append(&mut buf2);
1722 /// assert_eq!(buf, [1, 2, 3, 4]);
1723 /// assert_eq!(buf2, []);
1726 #[stable(feature = "append", since = "1.4.0")]
1727 pub fn append(&mut self, other: &mut Self) {
1729 self.extend(other.drain(..));
1732 /// Retains only the elements specified by the predicate.
1734 /// In other words, remove all elements `e` such that `f(&e)` returns false.
1735 /// This method operates in place and preserves the order of the retained
1741 /// use std::collections::VecDeque;
1743 /// let mut buf = VecDeque::new();
1744 /// buf.extend(1..5);
1745 /// buf.retain(|&x| x%2 == 0);
1746 /// assert_eq!(buf, [2, 4]);
1748 #[stable(feature = "vec_deque_retain", since = "1.4.0")]
1749 pub fn retain<F>(&mut self, mut f: F)
1750 where F: FnMut(&T) -> bool
1752 let len = self.len();
1758 self.swap(i - del, i);
1762 self.truncate(len - del);
1767 impl<T: Clone> VecDeque<T> {
1768 /// Modifies the `VecDeque` in-place so that `len()` is equal to new_len,
1769 /// either by removing excess elements or by appending clones of `value` to the back.
1774 /// use std::collections::VecDeque;
1776 /// let mut buf = VecDeque::new();
1777 /// buf.push_back(5);
1778 /// buf.push_back(10);
1779 /// buf.push_back(15);
1780 /// assert_eq!(buf, [5, 10, 15]);
1782 /// buf.resize(2, 0);
1783 /// assert_eq!(buf, [5, 10]);
1785 /// buf.resize(5, 20);
1786 /// assert_eq!(buf, [5, 10, 20, 20, 20]);
1788 #[stable(feature = "deque_extras", since = "1.16.0")]
1789 pub fn resize(&mut self, new_len: usize, value: T) {
1790 let len = self.len();
1793 self.extend(repeat(value).take(new_len - len))
1795 self.truncate(new_len);
1800 /// Returns the index in the underlying buffer for a given logical element index.
1802 fn wrap_index(index: usize, size: usize) -> usize {
1803 // size is always a power of 2
1804 debug_assert!(size.is_power_of_two());
1808 /// Returns the two slices that cover the VecDeque's valid range
1809 trait RingSlices: Sized {
1810 fn slice(self, from: usize, to: usize) -> Self;
1811 fn split_at(self, i: usize) -> (Self, Self);
1813 fn ring_slices(buf: Self, head: usize, tail: usize) -> (Self, Self) {
1814 let contiguous = tail <= head;
1816 let (empty, buf) = buf.split_at(0);
1817 (buf.slice(tail, head), empty)
1819 let (mid, right) = buf.split_at(tail);
1820 let (left, _) = mid.split_at(head);
1826 impl<'a, T> RingSlices for &'a [T] {
1827 fn slice(self, from: usize, to: usize) -> Self {
1830 fn split_at(self, i: usize) -> (Self, Self) {
1835 impl<'a, T> RingSlices for &'a mut [T] {
1836 fn slice(self, from: usize, to: usize) -> Self {
1839 fn split_at(self, i: usize) -> (Self, Self) {
1840 (*self).split_at_mut(i)
1844 /// Calculate the number of elements left to be read in the buffer
1846 fn count(tail: usize, head: usize, size: usize) -> usize {
1847 // size is always a power of 2
1848 (head.wrapping_sub(tail)) & (size - 1)
1851 /// `VecDeque` iterator.
1852 #[stable(feature = "rust1", since = "1.0.0")]
1853 pub struct Iter<'a, T: 'a> {
1859 #[stable(feature = "collection_debug", since = "1.17.0")]
1860 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
1861 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1862 f.debug_tuple("Iter")
1863 .field(&self.clone())
1868 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1869 #[stable(feature = "rust1", since = "1.0.0")]
1870 impl<'a, T> Clone for Iter<'a, T> {
1871 fn clone(&self) -> Iter<'a, T> {
1880 #[stable(feature = "rust1", since = "1.0.0")]
1881 impl<'a, T> Iterator for Iter<'a, T> {
1885 fn next(&mut self) -> Option<&'a T> {
1886 if self.tail == self.head {
1889 let tail = self.tail;
1890 self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len());
1891 unsafe { Some(self.ring.get_unchecked(tail)) }
1895 fn size_hint(&self) -> (usize, Option<usize>) {
1896 let len = count(self.tail, self.head, self.ring.len());
1900 fn fold<Acc, F>(self, mut accum: Acc, mut f: F) -> Acc
1901 where F: FnMut(Acc, Self::Item) -> Acc
1903 let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail);
1904 accum = front.iter().fold(accum, &mut f);
1905 back.iter().fold(accum, &mut f)
1909 #[stable(feature = "rust1", since = "1.0.0")]
1910 impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
1912 fn next_back(&mut self) -> Option<&'a T> {
1913 if self.tail == self.head {
1916 self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len());
1917 unsafe { Some(self.ring.get_unchecked(self.head)) }
1921 #[stable(feature = "rust1", since = "1.0.0")]
1922 impl<'a, T> ExactSizeIterator for Iter<'a, T> {
1923 fn is_empty(&self) -> bool {
1924 self.head == self.tail
1928 #[unstable(feature = "fused", issue = "35602")]
1929 impl<'a, T> FusedIterator for Iter<'a, T> {}
1932 /// `VecDeque` mutable iterator.
1933 #[stable(feature = "rust1", since = "1.0.0")]
1934 pub struct IterMut<'a, T: 'a> {
1940 #[stable(feature = "collection_debug", since = "1.17.0")]
1941 impl<'a, T: 'a + fmt::Debug> fmt::Debug for IterMut<'a, T> {
1942 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1943 f.debug_tuple("IterMut")
1944 .field(&self.clone())
1949 #[stable(feature = "rust1", since = "1.0.0")]
1950 impl<'a, T> Iterator for IterMut<'a, T> {
1951 type Item = &'a mut T;
1954 fn next(&mut self) -> Option<&'a mut T> {
1955 if self.tail == self.head {
1958 let tail = self.tail;
1959 self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len());
1962 let elem = self.ring.get_unchecked_mut(tail);
1963 Some(&mut *(elem as *mut _))
1968 fn size_hint(&self) -> (usize, Option<usize>) {
1969 let len = count(self.tail, self.head, self.ring.len());
1973 fn fold<Acc, F>(self, mut accum: Acc, mut f: F) -> Acc
1974 where F: FnMut(Acc, Self::Item) -> Acc
1976 let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail);
1977 accum = front.iter_mut().fold(accum, &mut f);
1978 back.iter_mut().fold(accum, &mut f)
1982 #[stable(feature = "rust1", since = "1.0.0")]
1983 impl<'a, T> DoubleEndedIterator for IterMut<'a, T> {
1985 fn next_back(&mut self) -> Option<&'a mut T> {
1986 if self.tail == self.head {
1989 self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len());
1992 let elem = self.ring.get_unchecked_mut(self.head);
1993 Some(&mut *(elem as *mut _))
1998 #[stable(feature = "rust1", since = "1.0.0")]
1999 impl<'a, T> ExactSizeIterator for IterMut<'a, T> {
2000 fn is_empty(&self) -> bool {
2001 self.head == self.tail
2005 #[unstable(feature = "fused", issue = "35602")]
2006 impl<'a, T> FusedIterator for IterMut<'a, T> {}
2008 /// A by-value VecDeque iterator
2010 #[stable(feature = "rust1", since = "1.0.0")]
2011 pub struct IntoIter<T> {
2015 #[stable(feature = "collection_debug", since = "1.17.0")]
2016 impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
2017 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2018 f.debug_tuple("IntoIter")
2019 .field(&self.clone())
2024 #[stable(feature = "rust1", since = "1.0.0")]
2025 impl<T> Iterator for IntoIter<T> {
2029 fn next(&mut self) -> Option<T> {
2030 self.inner.pop_front()
2034 fn size_hint(&self) -> (usize, Option<usize>) {
2035 let len = self.inner.len();
2040 #[stable(feature = "rust1", since = "1.0.0")]
2041 impl<T> DoubleEndedIterator for IntoIter<T> {
2043 fn next_back(&mut self) -> Option<T> {
2044 self.inner.pop_back()
2048 #[stable(feature = "rust1", since = "1.0.0")]
2049 impl<T> ExactSizeIterator for IntoIter<T> {
2050 fn is_empty(&self) -> bool {
2051 self.inner.is_empty()
2055 #[unstable(feature = "fused", issue = "35602")]
2056 impl<T> FusedIterator for IntoIter<T> {}
2058 /// A draining VecDeque iterator
2059 #[stable(feature = "drain", since = "1.6.0")]
2060 pub struct Drain<'a, T: 'a> {
2064 deque: Shared<VecDeque<T>>,
2067 #[stable(feature = "collection_debug", since = "1.17.0")]
2068 impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> {
2069 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2070 f.debug_tuple("Drain")
2071 .field(&self.clone())
2076 #[stable(feature = "drain", since = "1.6.0")]
2077 unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
2078 #[stable(feature = "drain", since = "1.6.0")]
2079 unsafe impl<'a, T: Send> Send for Drain<'a, T> {}
2081 #[stable(feature = "drain", since = "1.6.0")]
2082 impl<'a, T: 'a> Drop for Drain<'a, T> {
2083 fn drop(&mut self) {
2084 for _ in self.by_ref() {}
2086 let source_deque = unsafe { &mut **self.deque };
2088 // T = source_deque_tail; H = source_deque_head; t = drain_tail; h = drain_head
2091 // [. . . o o x x o o . . .]
2093 let orig_tail = source_deque.tail;
2094 let drain_tail = source_deque.head;
2095 let drain_head = self.after_tail;
2096 let orig_head = self.after_head;
2098 let tail_len = count(orig_tail, drain_tail, source_deque.cap());
2099 let head_len = count(drain_head, orig_head, source_deque.cap());
2101 // Restore the original head value
2102 source_deque.head = orig_head;
2104 match (tail_len, head_len) {
2106 source_deque.head = 0;
2107 source_deque.tail = 0;
2110 source_deque.tail = drain_head;
2113 source_deque.head = drain_tail;
2116 if tail_len <= head_len {
2117 source_deque.tail = source_deque.wrap_sub(drain_head, tail_len);
2118 source_deque.wrap_copy(source_deque.tail, orig_tail, tail_len);
2120 source_deque.head = source_deque.wrap_add(drain_tail, head_len);
2121 source_deque.wrap_copy(drain_tail, drain_head, head_len);
2128 #[stable(feature = "drain", since = "1.6.0")]
2129 impl<'a, T: 'a> Iterator for Drain<'a, T> {
2133 fn next(&mut self) -> Option<T> {
2134 self.iter.next().map(|elt| unsafe { ptr::read(elt) })
2138 fn size_hint(&self) -> (usize, Option<usize>) {
2139 self.iter.size_hint()
2143 #[stable(feature = "drain", since = "1.6.0")]
2144 impl<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> {
2146 fn next_back(&mut self) -> Option<T> {
2147 self.iter.next_back().map(|elt| unsafe { ptr::read(elt) })
2151 #[stable(feature = "drain", since = "1.6.0")]
2152 impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {}
2154 #[unstable(feature = "fused", issue = "35602")]
2155 impl<'a, T: 'a> FusedIterator for Drain<'a, T> {}
2157 #[stable(feature = "rust1", since = "1.0.0")]
2158 impl<A: PartialEq> PartialEq for VecDeque<A> {
2159 fn eq(&self, other: &VecDeque<A>) -> bool {
2160 if self.len() != other.len() {
2163 let (sa, sb) = self.as_slices();
2164 let (oa, ob) = other.as_slices();
2165 if sa.len() == oa.len() {
2166 sa == oa && sb == ob
2167 } else if sa.len() < oa.len() {
2168 // Always divisible in three sections, for example:
2169 // self: [a b c|d e f]
2170 // other: [0 1 2 3|4 5]
2171 // front = 3, mid = 1,
2172 // [a b c] == [0 1 2] && [d] == [3] && [e f] == [4 5]
2173 let front = sa.len();
2174 let mid = oa.len() - front;
2176 let (oa_front, oa_mid) = oa.split_at(front);
2177 let (sb_mid, sb_back) = sb.split_at(mid);
2178 debug_assert_eq!(sa.len(), oa_front.len());
2179 debug_assert_eq!(sb_mid.len(), oa_mid.len());
2180 debug_assert_eq!(sb_back.len(), ob.len());
2181 sa == oa_front && sb_mid == oa_mid && sb_back == ob
2183 let front = oa.len();
2184 let mid = sa.len() - front;
2186 let (sa_front, sa_mid) = sa.split_at(front);
2187 let (ob_mid, ob_back) = ob.split_at(mid);
2188 debug_assert_eq!(sa_front.len(), oa.len());
2189 debug_assert_eq!(sa_mid.len(), ob_mid.len());
2190 debug_assert_eq!(sb.len(), ob_back.len());
2191 sa_front == oa && sa_mid == ob_mid && sb == ob_back
2196 #[stable(feature = "rust1", since = "1.0.0")]
2197 impl<A: Eq> Eq for VecDeque<A> {}
2199 macro_rules! __impl_slice_eq1 {
2200 ($Lhs: ty, $Rhs: ty) => {
2201 __impl_slice_eq1! { $Lhs, $Rhs, Sized }
2203 ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
2204 #[stable(feature = "vec-deque-partial-eq-slice", since = "1.16.0")]
2205 impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
2206 fn eq(&self, other: &$Rhs) -> bool {
2207 if self.len() != other.len() {
2210 let (sa, sb) = self.as_slices();
2211 let (oa, ob) = other[..].split_at(sa.len());
2212 sa == oa && sb == ob
2218 __impl_slice_eq1! { VecDeque<A>, Vec<B> }
2219 __impl_slice_eq1! { VecDeque<A>, &'b [B] }
2220 __impl_slice_eq1! { VecDeque<A>, &'b mut [B] }
2222 macro_rules! array_impls {
2225 __impl_slice_eq1! { VecDeque<A>, [B; $N] }
2226 __impl_slice_eq1! { VecDeque<A>, &'b [B; $N] }
2227 __impl_slice_eq1! { VecDeque<A>, &'b mut [B; $N] }
2234 10 11 12 13 14 15 16 17 18 19
2235 20 21 22 23 24 25 26 27 28 29
2239 #[stable(feature = "rust1", since = "1.0.0")]
2240 impl<A: PartialOrd> PartialOrd for VecDeque<A> {
2241 fn partial_cmp(&self, other: &VecDeque<A>) -> Option<Ordering> {
2242 self.iter().partial_cmp(other.iter())
2246 #[stable(feature = "rust1", since = "1.0.0")]
2247 impl<A: Ord> Ord for VecDeque<A> {
2249 fn cmp(&self, other: &VecDeque<A>) -> Ordering {
2250 self.iter().cmp(other.iter())
2254 #[stable(feature = "rust1", since = "1.0.0")]
2255 impl<A: Hash> Hash for VecDeque<A> {
2256 fn hash<H: Hasher>(&self, state: &mut H) {
2257 self.len().hash(state);
2258 let (a, b) = self.as_slices();
2259 Hash::hash_slice(a, state);
2260 Hash::hash_slice(b, state);
2264 #[stable(feature = "rust1", since = "1.0.0")]
2265 impl<A> Index<usize> for VecDeque<A> {
2269 fn index(&self, index: usize) -> &A {
2270 self.get(index).expect("Out of bounds access")
2274 #[stable(feature = "rust1", since = "1.0.0")]
2275 impl<A> IndexMut<usize> for VecDeque<A> {
2277 fn index_mut(&mut self, index: usize) -> &mut A {
2278 self.get_mut(index).expect("Out of bounds access")
2282 #[stable(feature = "rust1", since = "1.0.0")]
2283 impl<A> FromIterator<A> for VecDeque<A> {
2284 fn from_iter<T: IntoIterator<Item = A>>(iter: T) -> VecDeque<A> {
2285 let iterator = iter.into_iter();
2286 let (lower, _) = iterator.size_hint();
2287 let mut deq = VecDeque::with_capacity(lower);
2288 deq.extend(iterator);
2293 #[stable(feature = "rust1", since = "1.0.0")]
2294 impl<T> IntoIterator for VecDeque<T> {
2296 type IntoIter = IntoIter<T>;
2298 /// Consumes the list into a front-to-back iterator yielding elements by
2300 fn into_iter(self) -> IntoIter<T> {
2301 IntoIter { inner: self }
2305 #[stable(feature = "rust1", since = "1.0.0")]
2306 impl<'a, T> IntoIterator for &'a VecDeque<T> {
2308 type IntoIter = Iter<'a, T>;
2310 fn into_iter(self) -> Iter<'a, T> {
2315 #[stable(feature = "rust1", since = "1.0.0")]
2316 impl<'a, T> IntoIterator for &'a mut VecDeque<T> {
2317 type Item = &'a mut T;
2318 type IntoIter = IterMut<'a, T>;
2320 fn into_iter(mut self) -> IterMut<'a, T> {
2325 #[stable(feature = "rust1", since = "1.0.0")]
2326 impl<A> Extend<A> for VecDeque<A> {
2327 fn extend<T: IntoIterator<Item = A>>(&mut self, iter: T) {
2329 self.push_back(elt);
2334 #[stable(feature = "extend_ref", since = "1.2.0")]
2335 impl<'a, T: 'a + Copy> Extend<&'a T> for VecDeque<T> {
2336 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
2337 self.extend(iter.into_iter().cloned());
2341 #[stable(feature = "rust1", since = "1.0.0")]
2342 impl<T: fmt::Debug> fmt::Debug for VecDeque<T> {
2343 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
2344 f.debug_list().entries(self).finish()
2348 #[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")]
2349 impl<T> From<Vec<T>> for VecDeque<T> {
2350 fn from(mut other: Vec<T>) -> Self {
2352 let other_buf = other.as_mut_ptr();
2353 let mut buf = RawVec::from_raw_parts(other_buf, other.capacity());
2354 let len = other.len();
2357 // We need to extend the buf if it's not a power of two, too small
2358 // or doesn't have at least one free space
2359 if !buf.cap().is_power_of_two() || (buf.cap() < (MINIMUM_CAPACITY + 1)) ||
2360 (buf.cap() == len) {
2361 let cap = cmp::max(buf.cap() + 1, MINIMUM_CAPACITY + 1).next_power_of_two();
2362 buf.reserve_exact(len, cap - len);
2374 #[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")]
2375 impl<T> From<VecDeque<T>> for Vec<T> {
2376 fn from(other: VecDeque<T>) -> Self {
2378 let buf = other.buf.ptr();
2379 let len = other.len();
2380 let tail = other.tail;
2381 let head = other.head;
2382 let cap = other.cap();
2384 // Need to move the ring to the front of the buffer, as vec will expect this.
2385 if other.is_contiguous() {
2386 ptr::copy(buf.offset(tail as isize), buf, len);
2388 if (tail - head) >= cmp::min((cap - tail), head) {
2389 // There is enough free space in the centre for the shortest block so we can
2390 // do this in at most three copy moves.
2391 if (cap - tail) > head {
2392 // right hand block is the long one; move that enough for the left
2393 ptr::copy(buf.offset(tail as isize),
2394 buf.offset((tail - head) as isize),
2396 // copy left in the end
2397 ptr::copy(buf, buf.offset((cap - head) as isize), head);
2398 // shift the new thing to the start
2399 ptr::copy(buf.offset((tail - head) as isize), buf, len);
2401 // left hand block is the long one, we can do it in two!
2402 ptr::copy(buf, buf.offset((cap - tail) as isize), head);
2403 ptr::copy(buf.offset(tail as isize), buf, cap - tail);
2406 // Need to use N swaps to move the ring
2407 // We can use the space at the end of the ring as a temp store
2409 let mut left_edge: usize = 0;
2410 let mut right_edge: usize = tail;
2412 // The general problem looks like this
2413 // GHIJKLM...ABCDEF - before any swaps
2414 // ABCDEFM...GHIJKL - after 1 pass of swaps
2415 // ABCDEFGHIJM...KL - swap until the left edge reaches the temp store
2416 // - then restart the algorithm with a new (smaller) store
2417 // Sometimes the temp store is reached when the right edge is at the end
2418 // of the buffer - this means we've hit the right order with fewer swaps!
2421 // ABCDEF.. - after four only swaps we've finished
2423 while left_edge < len && right_edge != cap {
2424 let mut right_offset = 0;
2425 for i in left_edge..right_edge {
2426 right_offset = (i - left_edge) % (cap - right_edge);
2427 let src: isize = (right_edge + right_offset) as isize;
2428 ptr::swap(buf.offset(i as isize), buf.offset(src));
2430 let n_ops = right_edge - left_edge;
2432 right_edge += right_offset + 1;
2438 let out = Vec::from_raw_parts(buf, len, cap);
2449 use super::VecDeque;
2452 fn bench_push_back_100(b: &mut test::Bencher) {
2453 let mut deq = VecDeque::with_capacity(101);
2464 fn bench_push_front_100(b: &mut test::Bencher) {
2465 let mut deq = VecDeque::with_capacity(101);
2476 fn bench_pop_back_100(b: &mut test::Bencher) {
2477 let mut deq = VecDeque::<i32>::with_capacity(101);
2482 while !deq.is_empty() {
2483 test::black_box(deq.pop_back());
2489 fn bench_pop_front_100(b: &mut test::Bencher) {
2490 let mut deq = VecDeque::<i32>::with_capacity(101);
2495 while !deq.is_empty() {
2496 test::black_box(deq.pop_front());
2502 fn test_swap_front_back_remove() {
2503 fn test(back: bool) {
2504 // This test checks that every single combination of tail position and length is tested.
2505 // Capacity 15 should be large enough to cover every case.
2506 let mut tester = VecDeque::with_capacity(15);
2507 let usable_cap = tester.capacity();
2508 let final_len = usable_cap / 2;
2510 for len in 0..final_len {
2511 let expected: VecDeque<_> = if back {
2514 (0..len).rev().collect()
2516 for tail_pos in 0..usable_cap {
2517 tester.tail = tail_pos;
2518 tester.head = tail_pos;
2520 for i in 0..len * 2 {
2521 tester.push_front(i);
2524 assert_eq!(tester.swap_remove_back(i), Some(len * 2 - 1 - i));
2527 for i in 0..len * 2 {
2528 tester.push_back(i);
2531 let idx = tester.len() - 1 - i;
2532 assert_eq!(tester.swap_remove_front(idx), Some(len * 2 - 1 - i));
2535 assert!(tester.tail < tester.cap());
2536 assert!(tester.head < tester.cap());
2537 assert_eq!(tester, expected);
2547 // This test checks that every single combination of tail position, length, and
2548 // insertion position is tested. Capacity 15 should be large enough to cover every case.
2550 let mut tester = VecDeque::with_capacity(15);
2551 // can't guarantee we got 15, so have to get what we got.
2552 // 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else
2553 // this test isn't covering what it wants to
2554 let cap = tester.capacity();
2557 // len is the length *after* insertion
2559 // 0, 1, 2, .., len - 1
2560 let expected = (0..).take(len).collect::<VecDeque<_>>();
2561 for tail_pos in 0..cap {
2562 for to_insert in 0..len {
2563 tester.tail = tail_pos;
2564 tester.head = tail_pos;
2567 tester.push_back(i);
2570 tester.insert(to_insert, to_insert);
2571 assert!(tester.tail < tester.cap());
2572 assert!(tester.head < tester.cap());
2573 assert_eq!(tester, expected);
2581 // This test checks that every single combination of tail position, length, and
2582 // removal position is tested. Capacity 15 should be large enough to cover every case.
2584 let mut tester = VecDeque::with_capacity(15);
2585 // can't guarantee we got 15, so have to get what we got.
2586 // 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else
2587 // this test isn't covering what it wants to
2588 let cap = tester.capacity();
2590 // len is the length *after* removal
2591 for len in 0..cap - 1 {
2592 // 0, 1, 2, .., len - 1
2593 let expected = (0..).take(len).collect::<VecDeque<_>>();
2594 for tail_pos in 0..cap {
2595 for to_remove in 0..len + 1 {
2596 tester.tail = tail_pos;
2597 tester.head = tail_pos;
2600 tester.push_back(1234);
2602 tester.push_back(i);
2604 if to_remove == len {
2605 tester.push_back(1234);
2607 tester.remove(to_remove);
2608 assert!(tester.tail < tester.cap());
2609 assert!(tester.head < tester.cap());
2610 assert_eq!(tester, expected);
2618 let mut tester: VecDeque<usize> = VecDeque::with_capacity(7);
2620 let cap = tester.capacity();
2621 for len in 0..cap + 1 {
2622 for tail in 0..cap + 1 {
2623 for drain_start in 0..len + 1 {
2624 for drain_end in drain_start..len + 1 {
2628 tester.push_back(i);
2631 // Check that we drain the correct values
2632 let drained: VecDeque<_> = tester.drain(drain_start..drain_end).collect();
2633 let drained_expected: VecDeque<_> = (drain_start..drain_end).collect();
2634 assert_eq!(drained, drained_expected);
2636 // We shouldn't have changed the capacity or made the
2637 // head or tail out of bounds
2638 assert_eq!(tester.capacity(), cap);
2639 assert!(tester.tail < tester.cap());
2640 assert!(tester.head < tester.cap());
2642 // We should see the correct values in the VecDeque
2643 let expected: VecDeque<_> = (0..drain_start)
2644 .chain(drain_end..len)
2646 assert_eq!(expected, tester);
2654 fn test_shrink_to_fit() {
2655 // This test checks that every single combination of head and tail position,
2656 // is tested. Capacity 15 should be large enough to cover every case.
2658 let mut tester = VecDeque::with_capacity(15);
2659 // can't guarantee we got 15, so have to get what we got.
2660 // 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else
2661 // this test isn't covering what it wants to
2662 let cap = tester.capacity();
2664 let max_cap = tester.capacity();
2666 for len in 0..cap + 1 {
2667 // 0, 1, 2, .., len - 1
2668 let expected = (0..).take(len).collect::<VecDeque<_>>();
2669 for tail_pos in 0..max_cap + 1 {
2670 tester.tail = tail_pos;
2671 tester.head = tail_pos;
2674 tester.push_back(i);
2676 tester.shrink_to_fit();
2677 assert!(tester.capacity() <= cap);
2678 assert!(tester.tail < tester.cap());
2679 assert!(tester.head < tester.cap());
2680 assert_eq!(tester, expected);
2686 fn test_split_off() {
2687 // This test checks that every single combination of tail position, length, and
2688 // split position is tested. Capacity 15 should be large enough to cover every case.
2690 let mut tester = VecDeque::with_capacity(15);
2691 // can't guarantee we got 15, so have to get what we got.
2692 // 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else
2693 // this test isn't covering what it wants to
2694 let cap = tester.capacity();
2696 // len is the length *before* splitting
2698 // index to split at
2699 for at in 0..len + 1 {
2700 // 0, 1, 2, .., at - 1 (may be empty)
2701 let expected_self = (0..).take(at).collect::<VecDeque<_>>();
2702 // at, at + 1, .., len - 1 (may be empty)
2703 let expected_other = (at..).take(len - at).collect::<VecDeque<_>>();
2705 for tail_pos in 0..cap {
2706 tester.tail = tail_pos;
2707 tester.head = tail_pos;
2709 tester.push_back(i);
2711 let result = tester.split_off(at);
2712 assert!(tester.tail < tester.cap());
2713 assert!(tester.head < tester.cap());
2714 assert!(result.tail < result.cap());
2715 assert!(result.head < result.cap());
2716 assert_eq!(tester, expected_self);
2717 assert_eq!(result, expected_other);
2724 fn test_from_vec() {
2725 use super::super::vec::Vec;
2727 for len in 0..cap + 1 {
2728 let mut vec = Vec::with_capacity(cap);
2731 let vd = VecDeque::from(vec.clone());
2732 assert!(vd.cap().is_power_of_two());
2733 assert_eq!(vd.len(), vec.len());
2734 assert!(vd.into_iter().eq(vec));
2740 fn test_vec_from_vecdeque() {
2741 use super::super::vec::Vec;
2743 fn create_vec_and_test_convert(cap: usize, offset: usize, len: usize) {
2744 let mut vd = VecDeque::with_capacity(cap);
2745 for _ in 0..offset {
2751 let vec: Vec<_> = Vec::from(vd.clone());
2752 assert_eq!(vec.len(), vd.len());
2753 assert!(vec.into_iter().eq(vd));
2756 for cap_pwr in 0..7 {
2757 // Make capacity as a (2^x)-1, so that the ring size is 2^x
2758 let cap = (2i32.pow(cap_pwr) - 1) as usize;
2760 // In these cases there is enough free space to solve it with copies
2761 for len in 0..((cap + 1) / 2) {
2762 // Test contiguous cases
2763 for offset in 0..(cap - len) {
2764 create_vec_and_test_convert(cap, offset, len)
2767 // Test cases where block at end of buffer is bigger than block at start
2768 for offset in (cap - len)..(cap - (len / 2)) {
2769 create_vec_and_test_convert(cap, offset, len)
2772 // Test cases where block at start of buffer is bigger than block at end
2773 for offset in (cap - (len / 2))..cap {
2774 create_vec_and_test_convert(cap, offset, len)
2778 // Now there's not (necessarily) space to straighten the ring with simple copies,
2779 // the ring will use swapping when:
2780 // (cap + 1 - offset) > (cap + 1 - len) && (len - (cap + 1 - offset)) > (cap + 1 - len))
2781 // right block size > free space && left block size > free space
2782 for len in ((cap + 1) / 2)..cap {
2783 // Test contiguous cases
2784 for offset in 0..(cap - len) {
2785 create_vec_and_test_convert(cap, offset, len)
2788 // Test cases where block at end of buffer is bigger than block at start
2789 for offset in (cap - len)..(cap - (len / 2)) {
2790 create_vec_and_test_convert(cap, offset, len)
2793 // Test cases where block at start of buffer is bigger than block at end
2794 for offset in (cap - (len / 2))..cap {
2795 create_vec_and_test_convert(cap, offset, len)