From 75dfc711da035ab8cc29a2dc32644f47e9d16ed8 Mon Sep 17 00:00:00 2001 From: C Date: Fri, 13 Nov 2020 17:56:39 +0000 Subject: refactor: vec_deque ignore-tidy-filelength commit c547d5fabcd756515afa7263ee5304965bb4c497 Author: C Date: Sat Oct 31 11:22:23 2020 +0000 test: updating ui/hygiene/panic-location.rs expected commit 2af03769c4ffdbbbad75197a1ad0df8c599186be Author: C Date: Sat Oct 31 10:43:30 2020 +0000 fix: documentation unresolved link commit c4b0df361ce27d7392d8016229f2e0265af32086 Author: C Date: Sat Oct 31 02:58:31 2020 +0000 style: compiling with Rust's style guidelines commit bdd2de5f3c09b49a18e3293f2457fcab25557c96 Author: C Date: Sat Oct 31 02:56:31 2020 +0000 refactor: removing ignore-tidy-filelength commit fcc4b3bc41f57244c65ebb8e4efe4cbc9460b5a9 Author: C Date: Sat Oct 31 02:51:35 2020 +0000 refactor: moving trait RingSlices to ring_slices.rs commit 2f0cc539c06d8841baf7f675168f68ca7c21e68e Author: C Date: Sat Oct 31 02:46:09 2020 +0000 refactor: moving struct PairSlices to pair_slices.rs commit a55d3ef1dab4c3d85962b3a601ff8d1f7497faf2 Author: C Date: Sat Oct 31 02:31:45 2020 +0000 refactor: moving struct Iter to iter.rs commit 76ab33a12442a03726f36f606b4e0fe70f8f246b Author: C Date: Sat Oct 31 02:24:32 2020 +0000 refactor: moving struct IntoIter into into_iter.rs commit abe0d9eea2933881858c3b1bc09df67cedc5ada5 Author: C Date: Sat Oct 31 02:19:07 2020 +0000 refactor: moving struct IterMut into iter_mut.rs commit 70ebd6420335e1895e2afa2763a0148897963e24 Author: C Date: Sat Oct 31 01:49:15 2020 +0000 refactor: moved macros into macros.rs commit b08dd2add994b04ae851aa065800bd8bd6326134 Author: C Date: Sat Oct 31 01:05:36 2020 +0000 refactor: moving vec_deque.rs to vec_deque/mod.rs --- library/alloc/src/collections/vec_deque.rs | 3291 -------------------- .../alloc/src/collections/vec_deque/into_iter.rs | 57 + library/alloc/src/collections/vec_deque/iter.rs | 159 + .../alloc/src/collections/vec_deque/iter_mut.rs | 128 + library/alloc/src/collections/vec_deque/macros.rs | 19 + library/alloc/src/collections/vec_deque/mod.rs | 2848 +++++++++++++++++ .../alloc/src/collections/vec_deque/pair_slices.rs | 66 + .../alloc/src/collections/vec_deque/ring_slices.rs | 56 + 8 files changed, 3333 insertions(+), 3291 deletions(-) delete mode 100644 library/alloc/src/collections/vec_deque.rs create mode 100644 library/alloc/src/collections/vec_deque/into_iter.rs create mode 100644 library/alloc/src/collections/vec_deque/iter.rs create mode 100644 library/alloc/src/collections/vec_deque/iter_mut.rs create mode 100644 library/alloc/src/collections/vec_deque/macros.rs create mode 100644 library/alloc/src/collections/vec_deque/mod.rs create mode 100644 library/alloc/src/collections/vec_deque/pair_slices.rs create mode 100644 library/alloc/src/collections/vec_deque/ring_slices.rs (limited to 'library/alloc') diff --git a/library/alloc/src/collections/vec_deque.rs b/library/alloc/src/collections/vec_deque.rs deleted file mode 100644 index 22b02a4f849..00000000000 --- a/library/alloc/src/collections/vec_deque.rs +++ /dev/null @@ -1,3291 +0,0 @@ -//! A double-ended queue implemented with a growable ring buffer. -//! -//! This queue has *O*(1) amortized inserts and removals from both ends of the -//! container. It also has *O*(1) indexing like a vector. The contained elements -//! are not required to be copyable, and the queue will be sendable if the -//! contained type is sendable. - -#![stable(feature = "rust1", since = "1.0.0")] - -// ignore-tidy-filelength - -use core::array; -use core::cmp::{self, Ordering}; -use core::fmt; -use core::hash::{Hash, Hasher}; -use core::iter::{repeat_with, FromIterator, FusedIterator}; -use core::marker::PhantomData; -use core::mem::{self, replace, ManuallyDrop}; -use core::ops::{Index, IndexMut, Range, RangeBounds, Try}; -use core::ptr::{self, NonNull}; -use core::slice; - -use crate::collections::TryReserveError; -use crate::raw_vec::RawVec; -use crate::vec::Vec; - -#[stable(feature = "drain", since = "1.6.0")] -pub use self::drain::Drain; - -mod drain; - -#[cfg(test)] -mod tests; - -const INITIAL_CAPACITY: usize = 7; // 2^3 - 1 -const MINIMUM_CAPACITY: usize = 1; // 2 - 1 - -const MAXIMUM_ZST_CAPACITY: usize = 1 << (core::mem::size_of::() * 8 - 1); // Largest possible power of two - -/// A double-ended queue implemented with a growable ring buffer. -/// -/// The "default" usage of this type as a queue is to use [`push_back`] to add to -/// the queue, and [`pop_front`] to remove from the queue. [`extend`] and [`append`] -/// push onto the back in this manner, and iterating over `VecDeque` goes front -/// to back. -/// -/// Since `VecDeque` is a ring buffer, its elements are not necessarily contiguous -/// in memory. If you want to access the elements as a single slice, such as for -/// efficient sorting, you can use [`make_contiguous`]. It rotates the `VecDeque` -/// so that its elements do not wrap, and returns a mutable slice to the -/// now-contiguous element sequence. -/// -/// [`push_back`]: VecDeque::push_back -/// [`pop_front`]: VecDeque::pop_front -/// [`extend`]: VecDeque::extend -/// [`append`]: VecDeque::append -/// [`make_contiguous`]: VecDeque::make_contiguous -#[cfg_attr(not(test), rustc_diagnostic_item = "vecdeque_type")] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct VecDeque { - // tail and head are pointers into the buffer. Tail always points - // to the first element that could be read, Head always points - // to where data should be written. - // If tail == head the buffer is empty. The length of the ringbuffer - // is defined as the distance between the two. - tail: usize, - head: usize, - buf: RawVec, -} - -/// PairSlices pairs up equal length slice parts of two deques -/// -/// For example, given deques "A" and "B" with the following division into slices: -/// -/// A: [0 1 2] [3 4 5] -/// B: [a b] [c d e] -/// -/// It produces the following sequence of matching slices: -/// -/// ([0 1], [a b]) -/// (\[2\], \[c\]) -/// ([3 4], [d e]) -/// -/// and the uneven remainder of either A or B is skipped. -struct PairSlices<'a, 'b, T> { - a0: &'a mut [T], - a1: &'a mut [T], - b0: &'b [T], - b1: &'b [T], -} - -impl<'a, 'b, T> PairSlices<'a, 'b, T> { - fn from(to: &'a mut VecDeque, from: &'b VecDeque) -> Self { - let (a0, a1) = to.as_mut_slices(); - let (b0, b1) = from.as_slices(); - PairSlices { a0, a1, b0, b1 } - } - - fn has_remainder(&self) -> bool { - !self.b0.is_empty() - } - - fn remainder(self) -> impl Iterator { - array::IntoIter::new([self.b0, self.b1]) - } -} - -impl<'a, 'b, T> Iterator for PairSlices<'a, 'b, T> { - type Item = (&'a mut [T], &'b [T]); - fn next(&mut self) -> Option { - // Get next part length - let part = cmp::min(self.a0.len(), self.b0.len()); - if part == 0 { - return None; - } - let (p0, p1) = replace(&mut self.a0, &mut []).split_at_mut(part); - let (q0, q1) = self.b0.split_at(part); - - // Move a1 into a0, if it's empty (and b1, b0 the same way). - self.a0 = p1; - self.b0 = q1; - if self.a0.is_empty() { - self.a0 = replace(&mut self.a1, &mut []); - } - if self.b0.is_empty() { - self.b0 = replace(&mut self.b1, &[]); - } - Some((p0, q0)) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Clone for VecDeque { - fn clone(&self) -> VecDeque { - self.iter().cloned().collect() - } - - fn clone_from(&mut self, other: &Self) { - self.truncate(other.len()); - - let mut iter = PairSlices::from(self, other); - while let Some((dst, src)) = iter.next() { - dst.clone_from_slice(&src); - } - - if iter.has_remainder() { - for remainder in iter.remainder() { - self.extend(remainder.iter().cloned()); - } - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -unsafe impl<#[may_dangle] T> Drop for VecDeque { - fn drop(&mut self) { - /// Runs the destructor for all items in the slice when it gets dropped (normally or - /// during unwinding). - struct Dropper<'a, T>(&'a mut [T]); - - impl<'a, T> Drop for Dropper<'a, T> { - fn drop(&mut self) { - unsafe { - ptr::drop_in_place(self.0); - } - } - } - - let (front, back) = self.as_mut_slices(); - unsafe { - let _back_dropper = Dropper(back); - // use drop for [T] - ptr::drop_in_place(front); - } - // RawVec handles deallocation - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Default for VecDeque { - /// Creates an empty `VecDeque`. - #[inline] - fn default() -> VecDeque { - VecDeque::new() - } -} - -impl VecDeque { - /// Marginally more convenient - #[inline] - fn ptr(&self) -> *mut T { - self.buf.ptr() - } - - /// Marginally more convenient - #[inline] - fn cap(&self) -> usize { - if mem::size_of::() == 0 { - // For zero sized types, we are always at maximum capacity - MAXIMUM_ZST_CAPACITY - } else { - self.buf.capacity() - } - } - - /// Turn ptr into a slice - #[inline] - unsafe fn buffer_as_slice(&self) -> &[T] { - unsafe { slice::from_raw_parts(self.ptr(), self.cap()) } - } - - /// Turn ptr into a mut slice - #[inline] - unsafe fn buffer_as_mut_slice(&mut self) -> &mut [T] { - unsafe { slice::from_raw_parts_mut(self.ptr(), self.cap()) } - } - - /// Moves an element out of the buffer - #[inline] - unsafe fn buffer_read(&mut self, off: usize) -> T { - unsafe { ptr::read(self.ptr().add(off)) } - } - - /// Writes an element into the buffer, moving it. - #[inline] - unsafe fn buffer_write(&mut self, off: usize, value: T) { - unsafe { - ptr::write(self.ptr().add(off), value); - } - } - - /// Returns `true` if the buffer is at full capacity. - #[inline] - fn is_full(&self) -> bool { - self.cap() - self.len() == 1 - } - - /// Returns the index in the underlying buffer for a given logical element - /// index. - #[inline] - fn wrap_index(&self, idx: usize) -> usize { - wrap_index(idx, self.cap()) - } - - /// Returns the index in the underlying buffer for a given logical element - /// index + addend. - #[inline] - fn wrap_add(&self, idx: usize, addend: usize) -> usize { - wrap_index(idx.wrapping_add(addend), self.cap()) - } - - /// Returns the index in the underlying buffer for a given logical element - /// index - subtrahend. - #[inline] - fn wrap_sub(&self, idx: usize, subtrahend: usize) -> usize { - wrap_index(idx.wrapping_sub(subtrahend), self.cap()) - } - - /// Copies a contiguous block of memory len long from src to dst - #[inline] - unsafe fn copy(&self, dst: usize, src: usize, len: usize) { - debug_assert!( - dst + len <= self.cap(), - "cpy dst={} src={} len={} cap={}", - dst, - src, - len, - self.cap() - ); - debug_assert!( - src + len <= self.cap(), - "cpy dst={} src={} len={} cap={}", - dst, - src, - len, - self.cap() - ); - unsafe { - ptr::copy(self.ptr().add(src), self.ptr().add(dst), len); - } - } - - /// Copies a contiguous block of memory len long from src to dst - #[inline] - unsafe fn copy_nonoverlapping(&self, dst: usize, src: usize, len: usize) { - debug_assert!( - dst + len <= self.cap(), - "cno dst={} src={} len={} cap={}", - dst, - src, - len, - self.cap() - ); - debug_assert!( - src + len <= self.cap(), - "cno dst={} src={} len={} cap={}", - dst, - src, - len, - self.cap() - ); - unsafe { - ptr::copy_nonoverlapping(self.ptr().add(src), self.ptr().add(dst), len); - } - } - - /// Copies a potentially wrapping block of memory len long from src to dest. - /// (abs(dst - src) + len) must be no larger than cap() (There must be at - /// most one continuous overlapping region between src and dest). - unsafe fn wrap_copy(&self, dst: usize, src: usize, len: usize) { - #[allow(dead_code)] - fn diff(a: usize, b: usize) -> usize { - if a <= b { b - a } else { a - b } - } - debug_assert!( - cmp::min(diff(dst, src), self.cap() - diff(dst, src)) + len <= self.cap(), - "wrc dst={} src={} len={} cap={}", - dst, - src, - len, - self.cap() - ); - - if src == dst || len == 0 { - return; - } - - let dst_after_src = self.wrap_sub(dst, src) < len; - - let src_pre_wrap_len = self.cap() - src; - let dst_pre_wrap_len = self.cap() - dst; - let src_wraps = src_pre_wrap_len < len; - let dst_wraps = dst_pre_wrap_len < len; - - match (dst_after_src, src_wraps, dst_wraps) { - (_, false, false) => { - // src doesn't wrap, dst doesn't wrap - // - // S . . . - // 1 [_ _ A A B B C C _] - // 2 [_ _ A A A A B B _] - // D . . . - // - unsafe { - self.copy(dst, src, len); - } - } - (false, false, true) => { - // dst before src, src doesn't wrap, dst wraps - // - // S . . . - // 1 [A A B B _ _ _ C C] - // 2 [A A B B _ _ _ A A] - // 3 [B B B B _ _ _ A A] - // . . D . - // - unsafe { - self.copy(dst, src, dst_pre_wrap_len); - self.copy(0, src + dst_pre_wrap_len, len - dst_pre_wrap_len); - } - } - (true, false, true) => { - // src before dst, src doesn't wrap, dst wraps - // - // S . . . - // 1 [C C _ _ _ A A B B] - // 2 [B B _ _ _ A A B B] - // 3 [B B _ _ _ A A A A] - // . . D . - // - unsafe { - self.copy(0, src + dst_pre_wrap_len, len - dst_pre_wrap_len); - self.copy(dst, src, dst_pre_wrap_len); - } - } - (false, true, false) => { - // dst before src, src wraps, dst doesn't wrap - // - // . . S . - // 1 [C C _ _ _ A A B B] - // 2 [C C _ _ _ B B B B] - // 3 [C C _ _ _ B B C C] - // D . . . - // - unsafe { - self.copy(dst, src, src_pre_wrap_len); - self.copy(dst + src_pre_wrap_len, 0, len - src_pre_wrap_len); - } - } - (true, true, false) => { - // src before dst, src wraps, dst doesn't wrap - // - // . . S . - // 1 [A A B B _ _ _ C C] - // 2 [A A A A _ _ _ C C] - // 3 [C C A A _ _ _ C C] - // D . . . - // - unsafe { - self.copy(dst + src_pre_wrap_len, 0, len - src_pre_wrap_len); - self.copy(dst, src, src_pre_wrap_len); - } - } - (false, true, true) => { - // dst before src, src wraps, dst wraps - // - // . . . S . - // 1 [A B C D _ E F G H] - // 2 [A B C D _ E G H H] - // 3 [A B C D _ E G H A] - // 4 [B C C D _ E G H A] - // . . D . . - // - debug_assert!(dst_pre_wrap_len > src_pre_wrap_len); - let delta = dst_pre_wrap_len - src_pre_wrap_len; - unsafe { - self.copy(dst, src, src_pre_wrap_len); - self.copy(dst + src_pre_wrap_len, 0, delta); - self.copy(0, delta, len - dst_pre_wrap_len); - } - } - (true, true, true) => { - // src before dst, src wraps, dst wraps - // - // . . S . . - // 1 [A B C D _ E F G H] - // 2 [A A B D _ E F G H] - // 3 [H A B D _ E F G H] - // 4 [H A B D _ E F F G] - // . . . D . - // - debug_assert!(src_pre_wrap_len > dst_pre_wrap_len); - let delta = src_pre_wrap_len - dst_pre_wrap_len; - unsafe { - self.copy(delta, 0, len - src_pre_wrap_len); - self.copy(0, self.cap() - delta, delta); - self.copy(dst, src, dst_pre_wrap_len); - } - } - } - } - - /// Frobs the head and tail sections around to handle the fact that we - /// just reallocated. Unsafe because it trusts old_capacity. - #[inline] - unsafe fn handle_capacity_increase(&mut self, old_capacity: usize) { - let new_capacity = self.cap(); - - // Move the shortest contiguous section of the ring buffer - // T H - // [o o o o o o o . ] - // T H - // A [o o o o o o o . . . . . . . . . ] - // H T - // [o o . o o o o o ] - // T H - // B [. . . o o o o o o o . . . . . . ] - // H T - // [o o o o o . o o ] - // H T - // C [o o o o o . . . . . . . . . o o ] - - if self.tail <= self.head { - // A - // Nop - } else if self.head < old_capacity - self.tail { - // B - unsafe { - self.copy_nonoverlapping(old_capacity, 0, self.head); - } - self.head += old_capacity; - debug_assert!(self.head > self.tail); - } else { - // C - let new_tail = new_capacity - (old_capacity - self.tail); - unsafe { - self.copy_nonoverlapping(new_tail, self.tail, old_capacity - self.tail); - } - self.tail = new_tail; - debug_assert!(self.head < self.tail); - } - debug_assert!(self.head < self.cap()); - debug_assert!(self.tail < self.cap()); - debug_assert!(self.cap().count_ones() == 1); - } -} - -impl VecDeque { - /// Creates an empty `VecDeque`. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let vector: VecDeque = VecDeque::new(); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn new() -> VecDeque { - VecDeque::with_capacity(INITIAL_CAPACITY) - } - - /// Creates an empty `VecDeque` with space for at least `capacity` elements. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let vector: VecDeque = VecDeque::with_capacity(10); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn with_capacity(capacity: usize) -> VecDeque { - // +1 since the ringbuffer always leaves one space empty - let cap = cmp::max(capacity + 1, MINIMUM_CAPACITY + 1).next_power_of_two(); - assert!(cap > capacity, "capacity overflow"); - - VecDeque { tail: 0, head: 0, buf: RawVec::with_capacity(cap) } - } - - /// Provides a reference to the element at the given index. - /// - /// Element at index 0 is the front of the queue. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(3); - /// buf.push_back(4); - /// buf.push_back(5); - /// assert_eq!(buf.get(1), Some(&4)); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn get(&self, index: usize) -> Option<&T> { - if index < self.len() { - let idx = self.wrap_add(self.tail, index); - unsafe { Some(&*self.ptr().add(idx)) } - } else { - None - } - } - - /// Provides a mutable reference to the element at the given index. - /// - /// Element at index 0 is the front of the queue. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(3); - /// buf.push_back(4); - /// buf.push_back(5); - /// if let Some(elem) = buf.get_mut(1) { - /// *elem = 7; - /// } - /// - /// assert_eq!(buf[1], 7); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn get_mut(&mut self, index: usize) -> Option<&mut T> { - if index < self.len() { - let idx = self.wrap_add(self.tail, index); - unsafe { Some(&mut *self.ptr().add(idx)) } - } else { - None - } - } - - /// Swaps elements at indices `i` and `j`. - /// - /// `i` and `j` may be equal. - /// - /// Element at index 0 is the front of the queue. - /// - /// # Panics - /// - /// Panics if either index is out of bounds. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(3); - /// buf.push_back(4); - /// buf.push_back(5); - /// assert_eq!(buf, [3, 4, 5]); - /// buf.swap(0, 2); - /// assert_eq!(buf, [5, 4, 3]); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn swap(&mut self, i: usize, j: usize) { - assert!(i < self.len()); - assert!(j < self.len()); - let ri = self.wrap_add(self.tail, i); - let rj = self.wrap_add(self.tail, j); - unsafe { ptr::swap(self.ptr().add(ri), self.ptr().add(rj)) } - } - - /// Returns the number of elements the `VecDeque` can hold without - /// reallocating. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let buf: VecDeque = VecDeque::with_capacity(10); - /// assert!(buf.capacity() >= 10); - /// ``` - #[inline] - #[stable(feature = "rust1", since = "1.0.0")] - pub fn capacity(&self) -> usize { - self.cap() - 1 - } - - /// Reserves the minimum capacity for exactly `additional` more elements to be inserted in the - /// given `VecDeque`. Does nothing if the capacity is already sufficient. - /// - /// Note that the allocator may give the collection more space than it requests. Therefore - /// capacity can not be relied upon to be precisely minimal. Prefer [`reserve`] if future - /// insertions are expected. - /// - /// # Panics - /// - /// Panics if the new capacity overflows `usize`. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf: VecDeque = vec![1].into_iter().collect(); - /// buf.reserve_exact(10); - /// assert!(buf.capacity() >= 11); - /// ``` - /// - /// [`reserve`]: VecDeque::reserve - #[stable(feature = "rust1", since = "1.0.0")] - pub fn reserve_exact(&mut self, additional: usize) { - self.reserve(additional); - } - - /// Reserves capacity for at least `additional` more elements to be inserted in the given - /// `VecDeque`. The collection may reserve more space to avoid frequent reallocations. - /// - /// # Panics - /// - /// Panics if the new capacity overflows `usize`. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf: VecDeque = vec![1].into_iter().collect(); - /// buf.reserve(10); - /// assert!(buf.capacity() >= 11); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn reserve(&mut self, additional: usize) { - let old_cap = self.cap(); - let used_cap = self.len() + 1; - let new_cap = used_cap - .checked_add(additional) - .and_then(|needed_cap| needed_cap.checked_next_power_of_two()) - .expect("capacity overflow"); - - if new_cap > old_cap { - self.buf.reserve_exact(used_cap, new_cap - used_cap); - unsafe { - self.handle_capacity_increase(old_cap); - } - } - } - - /// Tries to reserve the minimum capacity for exactly `additional` more elements to - /// be inserted in the given `VecDeque`. After calling `try_reserve_exact`, - /// capacity will be greater than or equal to `self.len() + additional`. - /// Does nothing if the capacity is already sufficient. - /// - /// Note that the allocator may give the collection more space than it - /// requests. Therefore, capacity can not be relied upon to be precisely - /// minimal. Prefer `reserve` if future insertions are expected. - /// - /// # Errors - /// - /// If the capacity overflows `usize`, or the allocator reports a failure, then an error - /// is returned. - /// - /// # Examples - /// - /// ``` - /// #![feature(try_reserve)] - /// use std::collections::TryReserveError; - /// use std::collections::VecDeque; - /// - /// fn process_data(data: &[u32]) -> Result, TryReserveError> { - /// let mut output = VecDeque::new(); - /// - /// // Pre-reserve the memory, exiting if we can't - /// output.try_reserve_exact(data.len())?; - /// - /// // Now we know this can't OOM(Out-Of-Memory) in the middle of our complex work - /// output.extend(data.iter().map(|&val| { - /// val * 2 + 5 // very complicated - /// })); - /// - /// Ok(output) - /// } - /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); - /// ``` - #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] - pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { - self.try_reserve(additional) - } - - /// Tries to reserve capacity for at least `additional` more elements to be inserted - /// in the given `VecDeque`. The collection may reserve more space to avoid - /// frequent reallocations. After calling `try_reserve`, capacity will be - /// greater than or equal to `self.len() + additional`. Does nothing if - /// capacity is already sufficient. - /// - /// # Errors - /// - /// If the capacity overflows `usize`, or the allocator reports a failure, then an error - /// is returned. - /// - /// # Examples - /// - /// ``` - /// #![feature(try_reserve)] - /// use std::collections::TryReserveError; - /// use std::collections::VecDeque; - /// - /// fn process_data(data: &[u32]) -> Result, TryReserveError> { - /// let mut output = VecDeque::new(); - /// - /// // Pre-reserve the memory, exiting if we can't - /// output.try_reserve(data.len())?; - /// - /// // Now we know this can't OOM in the middle of our complex work - /// output.extend(data.iter().map(|&val| { - /// val * 2 + 5 // very complicated - /// })); - /// - /// Ok(output) - /// } - /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); - /// ``` - #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] - pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { - let old_cap = self.cap(); - let used_cap = self.len() + 1; - let new_cap = used_cap - .checked_add(additional) - .and_then(|needed_cap| needed_cap.checked_next_power_of_two()) - .ok_or(TryReserveError::CapacityOverflow)?; - - if new_cap > old_cap { - self.buf.try_reserve_exact(used_cap, new_cap - used_cap)?; - unsafe { - self.handle_capacity_increase(old_cap); - } - } - Ok(()) - } - - /// Shrinks the capacity of the `VecDeque` as much as possible. - /// - /// It will drop down as close as possible to the length but the allocator may still inform the - /// `VecDeque` that there is space for a few more elements. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::with_capacity(15); - /// buf.extend(0..4); - /// assert_eq!(buf.capacity(), 15); - /// buf.shrink_to_fit(); - /// assert!(buf.capacity() >= 4); - /// ``` - #[stable(feature = "deque_extras_15", since = "1.5.0")] - pub fn shrink_to_fit(&mut self) { - self.shrink_to(0); - } - - /// Shrinks the capacity of the `VecDeque` with a lower bound. - /// - /// The capacity will remain at least as large as both the length - /// and the supplied value. - /// - /// Panics if the current capacity is smaller than the supplied - /// minimum capacity. - /// - /// # Examples - /// - /// ``` - /// #![feature(shrink_to)] - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::with_capacity(15); - /// buf.extend(0..4); - /// assert_eq!(buf.capacity(), 15); - /// buf.shrink_to(6); - /// assert!(buf.capacity() >= 6); - /// buf.shrink_to(0); - /// assert!(buf.capacity() >= 4); - /// ``` - #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")] - pub fn shrink_to(&mut self, min_capacity: usize) { - assert!(self.capacity() >= min_capacity, "Tried to shrink to a larger capacity"); - - // +1 since the ringbuffer always leaves one space empty - // len + 1 can't overflow for an existing, well-formed ringbuffer. - let target_cap = cmp::max(cmp::max(min_capacity, self.len()) + 1, MINIMUM_CAPACITY + 1) - .next_power_of_two(); - - if target_cap < self.cap() { - // There are three cases of interest: - // All elements are out of desired bounds - // Elements are contiguous, and head is out of desired bounds - // Elements are discontiguous, and tail is out of desired bounds - // - // At all other times, element positions are unaffected. - // - // Indicates that elements at the head should be moved. - let head_outside = self.head == 0 || self.head >= target_cap; - // Move elements from out of desired bounds (positions after target_cap) - if self.tail >= target_cap && head_outside { - // T H - // [. . . . . . . . o o o o o o o . ] - // T H - // [o o o o o o o . ] - unsafe { - self.copy_nonoverlapping(0, self.tail, self.len()); - } - self.head = self.len(); - self.tail = 0; - } else if self.tail != 0 && self.tail < target_cap && head_outside { - // T H - // [. . . o o o o o o o . . . . . . ] - // H T - // [o o . o o o o o ] - let len = self.wrap_sub(self.head, target_cap); - unsafe { - self.copy_nonoverlapping(0, target_cap, len); - } - self.head = len; - debug_assert!(self.head < self.tail); - } else if self.tail >= target_cap { - // H T - // [o o o o o . . . . . . . . . o o ] - // H T - // [o o o o o . o o ] - debug_assert!(self.wrap_sub(self.head, 1) < target_cap); - let len = self.cap() - self.tail; - let new_tail = target_cap - len; - unsafe { - self.copy_nonoverlapping(new_tail, self.tail, len); - } - self.tail = new_tail; - debug_assert!(self.head < self.tail); - } - - self.buf.shrink_to_fit(target_cap); - - debug_assert!(self.head < self.cap()); - debug_assert!(self.tail < self.cap()); - debug_assert!(self.cap().count_ones() == 1); - } - } - - /// Shortens the `VecDeque`, keeping the first `len` elements and dropping - /// the rest. - /// - /// If `len` is greater than the `VecDeque`'s current length, this has no - /// effect. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(5); - /// buf.push_back(10); - /// buf.push_back(15); - /// assert_eq!(buf, [5, 10, 15]); - /// buf.truncate(1); - /// assert_eq!(buf, [5]); - /// ``` - #[stable(feature = "deque_extras", since = "1.16.0")] - pub fn truncate(&mut self, len: usize) { - /// Runs the destructor for all items in the slice when it gets dropped (normally or - /// during unwinding). - struct Dropper<'a, T>(&'a mut [T]); - - impl<'a, T> Drop for Dropper<'a, T> { - fn drop(&mut self) { - unsafe { - ptr::drop_in_place(self.0); - } - } - } - - // Safe because: - // - // * Any slice passed to `drop_in_place` is valid; the second case has - // `len <= front.len()` and returning on `len > self.len()` ensures - // `begin <= back.len()` in the first case - // * The head of the VecDeque is moved before calling `drop_in_place`, - // so no value is dropped twice if `drop_in_place` panics - unsafe { - if len > self.len() { - return; - } - let num_dropped = self.len() - len; - let (front, back) = self.as_mut_slices(); - if len > front.len() { - let begin = len - front.len(); - let drop_back = back.get_unchecked_mut(begin..) as *mut _; - self.head = self.wrap_sub(self.head, num_dropped); - ptr::drop_in_place(drop_back); - } else { - let drop_back = back as *mut _; - let drop_front = front.get_unchecked_mut(len..) as *mut _; - self.head = self.wrap_sub(self.head, num_dropped); - - // Make sure the second half is dropped even when a destructor - // in the first one panics. - let _back_dropper = Dropper(&mut *drop_back); - ptr::drop_in_place(drop_front); - } - } - } - - /// Returns a front-to-back iterator. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(5); - /// buf.push_back(3); - /// buf.push_back(4); - /// let b: &[_] = &[&5, &3, &4]; - /// let c: Vec<&i32> = buf.iter().collect(); - /// assert_eq!(&c[..], b); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn iter(&self) -> Iter<'_, T> { - Iter { tail: self.tail, head: self.head, ring: unsafe { self.buffer_as_slice() } } - } - - /// Returns a front-to-back iterator that returns mutable references. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(5); - /// buf.push_back(3); - /// buf.push_back(4); - /// for num in buf.iter_mut() { - /// *num = *num - 2; - /// } - /// let b: &[_] = &[&mut 3, &mut 1, &mut 2]; - /// assert_eq!(&buf.iter_mut().collect::>()[..], b); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn iter_mut(&mut self) -> IterMut<'_, T> { - // SAFETY: The internal `IterMut` safety invariant is established because the - // `ring` we create is a dereferencable slice for lifetime '_. - IterMut { - tail: self.tail, - head: self.head, - ring: ptr::slice_from_raw_parts_mut(self.ptr(), self.cap()), - phantom: PhantomData, - } - } - - /// Returns a pair of slices which contain, in order, the contents of the - /// `VecDeque`. - /// - /// If [`make_contiguous`] was previously called, all elements of the - /// `VecDeque` will be in the first slice and the second slice will be empty. - /// - /// [`make_contiguous`]: VecDeque::make_contiguous - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut vector = VecDeque::new(); - /// - /// vector.push_back(0); - /// vector.push_back(1); - /// vector.push_back(2); - /// - /// assert_eq!(vector.as_slices(), (&[0, 1, 2][..], &[][..])); - /// - /// vector.push_front(10); - /// vector.push_front(9); - /// - /// assert_eq!(vector.as_slices(), (&[9, 10][..], &[0, 1, 2][..])); - /// ``` - #[inline] - #[stable(feature = "deque_extras_15", since = "1.5.0")] - pub fn as_slices(&self) -> (&[T], &[T]) { - unsafe { - let buf = self.buffer_as_slice(); - RingSlices::ring_slices(buf, self.head, self.tail) - } - } - - /// Returns a pair of slices which contain, in order, the contents of the - /// `VecDeque`. - /// - /// If [`make_contiguous`] was previously called, all elements of the - /// `VecDeque` will be in the first slice and the second slice will be empty. - /// - /// [`make_contiguous`]: VecDeque::make_contiguous - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut vector = VecDeque::new(); - /// - /// vector.push_back(0); - /// vector.push_back(1); - /// - /// vector.push_front(10); - /// vector.push_front(9); - /// - /// vector.as_mut_slices().0[0] = 42; - /// vector.as_mut_slices().1[0] = 24; - /// assert_eq!(vector.as_slices(), (&[42, 10][..], &[24, 1][..])); - /// ``` - #[inline] - #[stable(feature = "deque_extras_15", since = "1.5.0")] - pub fn as_mut_slices(&mut self) -> (&mut [T], &mut [T]) { - unsafe { - let head = self.head; - let tail = self.tail; - let buf = self.buffer_as_mut_slice(); - RingSlices::ring_slices(buf, head, tail) - } - } - - /// Returns the number of elements in the `VecDeque`. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut v = VecDeque::new(); - /// assert_eq!(v.len(), 0); - /// v.push_back(1); - /// assert_eq!(v.len(), 1); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn len(&self) -> usize { - count(self.tail, self.head, self.cap()) - } - - /// Returns `true` if the `VecDeque` is empty. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut v = VecDeque::new(); - /// assert!(v.is_empty()); - /// v.push_front(1); - /// assert!(!v.is_empty()); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn is_empty(&self) -> bool { - self.tail == self.head - } - - fn range_tail_head(&self, range: R) -> (usize, usize) - where - R: RangeBounds, - { - let Range { start, end } = range.assert_len(self.len()); - let tail = self.wrap_add(self.tail, start); - let head = self.wrap_add(self.tail, end); - (tail, head) - } - - /// Creates an iterator that covers the specified range in the `VecDeque`. - /// - /// # Panics - /// - /// Panics if the starting point is greater than the end point or if - /// the end point is greater than the length of the vector. - /// - /// # Examples - /// - /// ``` - /// #![feature(deque_range)] - /// - /// use std::collections::VecDeque; - /// - /// let v: VecDeque<_> = vec![1, 2, 3].into_iter().collect(); - /// let range = v.range(2..).copied().collect::>(); - /// assert_eq!(range, [3]); - /// - /// // A full range covers all contents - /// let all = v.range(..); - /// assert_eq!(all.len(), 3); - /// ``` - #[inline] - #[unstable(feature = "deque_range", issue = "74217")] - pub fn range(&self, range: R) -> Iter<'_, T> - where - R: RangeBounds, - { - let (tail, head) = self.range_tail_head(range); - Iter { - tail, - head, - // The shared reference we have in &self is maintained in the '_ of Iter. - ring: unsafe { self.buffer_as_slice() }, - } - } - - /// Creates an iterator that covers the specified mutable range in the `VecDeque`. - /// - /// # Panics - /// - /// Panics if the starting point is greater than the end point or if - /// the end point is greater than the length of the vector. - /// - /// # Examples - /// - /// ``` - /// #![feature(deque_range)] - /// - /// use std::collections::VecDeque; - /// - /// let mut v: VecDeque<_> = vec![1, 2, 3].into_iter().collect(); - /// for v in v.range_mut(2..) { - /// *v *= 2; - /// } - /// assert_eq!(v, vec![1, 2, 6]); - /// - /// // A full range covers all contents - /// for v in v.range_mut(..) { - /// *v *= 2; - /// } - /// assert_eq!(v, vec![2, 4, 12]); - /// ``` - #[inline] - #[unstable(feature = "deque_range", issue = "74217")] - pub fn range_mut(&mut self, range: R) -> IterMut<'_, T> - where - R: RangeBounds, - { - let (tail, head) = self.range_tail_head(range); - - // SAFETY: The internal `IterMut` safety invariant is established because the - // `ring` we create is a dereferencable slice for lifetime '_. - IterMut { - tail, - head, - ring: ptr::slice_from_raw_parts_mut(self.ptr(), self.cap()), - phantom: PhantomData, - } - } - - /// Creates a draining iterator that removes the specified range in the - /// `VecDeque` and yields the removed items. - /// - /// Note 1: The element range is removed even if the iterator is not - /// consumed until the end. - /// - /// Note 2: It is unspecified how many elements are removed from the deque, - /// if the `Drain` value is not dropped, but the borrow it holds expires - /// (e.g., due to `mem::forget`). - /// - /// # Panics - /// - /// Panics if the starting point is greater than the end point or if - /// the end point is greater than the length of the vector. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut v: VecDeque<_> = vec![1, 2, 3].into_iter().collect(); - /// let drained = v.drain(2..).collect::>(); - /// assert_eq!(drained, [3]); - /// assert_eq!(v, [1, 2]); - /// - /// // A full range clears all contents - /// v.drain(..); - /// assert!(v.is_empty()); - /// ``` - #[inline] - #[stable(feature = "drain", since = "1.6.0")] - pub fn drain(&mut self, range: R) -> Drain<'_, T> - where - R: RangeBounds, - { - // Memory safety - // - // When the Drain is first created, the source deque is shortened to - // make sure no uninitialized or moved-from elements are accessible at - // all if the Drain's destructor never gets to run. - // - // Drain will ptr::read out the values to remove. - // When finished, the remaining data will be copied back to cover the hole, - // and the head/tail values will be restored correctly. - // - let (drain_tail, drain_head) = self.range_tail_head(range); - - // The deque's elements are parted into three segments: - // * self.tail -> drain_tail - // * drain_tail -> drain_head - // * drain_head -> self.head - // - // T = self.tail; H = self.head; t = drain_tail; h = drain_head - // - // We store drain_tail as self.head, and drain_head and self.head as - // after_tail and after_head respectively on the Drain. This also - // truncates the effective array such that if the Drain is leaked, we - // have forgotten about the potentially moved values after the start of - // the drain. - // - // T t h H - // [. . . o o x x o o . . .] - // - let head = self.head; - - // "forget" about the values after the start of the drain until after - // the drain is complete and the Drain destructor is run. - self.head = drain_tail; - - Drain { - deque: NonNull::from(&mut *self), - after_tail: drain_head, - after_head: head, - iter: Iter { - tail: drain_tail, - head: drain_head, - // Crucially, we only create shared references from `self` here and read from - // it. We do not write to `self` nor reborrow to a mutable reference. - // Hence the raw pointer we created above, for `deque`, remains valid. - ring: unsafe { self.buffer_as_slice() }, - }, - } - } - - /// Clears the `VecDeque`, removing all values. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut v = VecDeque::new(); - /// v.push_back(1); - /// v.clear(); - /// assert!(v.is_empty()); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - #[inline] - pub fn clear(&mut self) { - self.truncate(0); - } - - /// Returns `true` if the `VecDeque` contains an element equal to the - /// given value. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut vector: VecDeque = VecDeque::new(); - /// - /// vector.push_back(0); - /// vector.push_back(1); - /// - /// assert_eq!(vector.contains(&1), true); - /// assert_eq!(vector.contains(&10), false); - /// ``` - #[stable(feature = "vec_deque_contains", since = "1.12.0")] - pub fn contains(&self, x: &T) -> bool - where - T: PartialEq, - { - let (a, b) = self.as_slices(); - a.contains(x) || b.contains(x) - } - - /// Provides a reference to the front element, or `None` if the `VecDeque` is - /// empty. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut d = VecDeque::new(); - /// assert_eq!(d.front(), None); - /// - /// d.push_back(1); - /// d.push_back(2); - /// assert_eq!(d.front(), Some(&1)); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn front(&self) -> Option<&T> { - if !self.is_empty() { Some(&self[0]) } else { None } - } - - /// Provides a mutable reference to the front element, or `None` if the - /// `VecDeque` is empty. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut d = VecDeque::new(); - /// assert_eq!(d.front_mut(), None); - /// - /// d.push_back(1); - /// d.push_back(2); - /// match d.front_mut() { - /// Some(x) => *x = 9, - /// None => (), - /// } - /// assert_eq!(d.front(), Some(&9)); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn front_mut(&mut self) -> Option<&mut T> { - if !self.is_empty() { Some(&mut self[0]) } else { None } - } - - /// Provides a reference to the back element, or `None` if the `VecDeque` is - /// empty. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut d = VecDeque::new(); - /// assert_eq!(d.back(), None); - /// - /// d.push_back(1); - /// d.push_back(2); - /// assert_eq!(d.back(), Some(&2)); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn back(&self) -> Option<&T> { - if !self.is_empty() { Some(&self[self.len() - 1]) } else { None } - } - - /// Provides a mutable reference to the back element, or `None` if the - /// `VecDeque` is empty. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut d = VecDeque::new(); - /// assert_eq!(d.back(), None); - /// - /// d.push_back(1); - /// d.push_back(2); - /// match d.back_mut() { - /// Some(x) => *x = 9, - /// None => (), - /// } - /// assert_eq!(d.back(), Some(&9)); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn back_mut(&mut self) -> Option<&mut T> { - let len = self.len(); - if !self.is_empty() { Some(&mut self[len - 1]) } else { None } - } - - /// Removes the first element and returns it, or `None` if the `VecDeque` is - /// empty. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut d = VecDeque::new(); - /// d.push_back(1); - /// d.push_back(2); - /// - /// assert_eq!(d.pop_front(), Some(1)); - /// assert_eq!(d.pop_front(), Some(2)); - /// assert_eq!(d.pop_front(), None); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn pop_front(&mut self) -> Option { - if self.is_empty() { - None - } else { - let tail = self.tail; - self.tail = self.wrap_add(self.tail, 1); - unsafe { Some(self.buffer_read(tail)) } - } - } - - /// Removes the last element from the `VecDeque` and returns it, or `None` if - /// it is empty. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// assert_eq!(buf.pop_back(), None); - /// buf.push_back(1); - /// buf.push_back(3); - /// assert_eq!(buf.pop_back(), Some(3)); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn pop_back(&mut self) -> Option { - if self.is_empty() { - None - } else { - self.head = self.wrap_sub(self.head, 1); - let head = self.head; - unsafe { Some(self.buffer_read(head)) } - } - } - - /// Prepends an element to the `VecDeque`. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut d = VecDeque::new(); - /// d.push_front(1); - /// d.push_front(2); - /// assert_eq!(d.front(), Some(&2)); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn push_front(&mut self, value: T) { - if self.is_full() { - self.grow(); - } - - self.tail = self.wrap_sub(self.tail, 1); - let tail = self.tail; - unsafe { - self.buffer_write(tail, value); - } - } - - /// Appends an element to the back of the `VecDeque`. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(1); - /// buf.push_back(3); - /// assert_eq!(3, *buf.back().unwrap()); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn push_back(&mut self, value: T) { - if self.is_full() { - self.grow(); - } - - let head = self.head; - self.head = self.wrap_add(self.head, 1); - unsafe { self.buffer_write(head, value) } - } - - #[inline] - fn is_contiguous(&self) -> bool { - self.tail <= self.head - } - - /// Removes an element from anywhere in the `VecDeque` and returns it, - /// replacing it with the first element. - /// - /// This does not preserve ordering, but is *O*(1). - /// - /// Returns `None` if `index` is out of bounds. - /// - /// Element at index 0 is the front of the queue. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// assert_eq!(buf.swap_remove_front(0), None); - /// buf.push_back(1); - /// buf.push_back(2); - /// buf.push_back(3); - /// assert_eq!(buf, [1, 2, 3]); - /// - /// assert_eq!(buf.swap_remove_front(2), Some(3)); - /// assert_eq!(buf, [2, 1]); - /// ``` - #[stable(feature = "deque_extras_15", since = "1.5.0")] - pub fn swap_remove_front(&mut self, index: usize) -> Option { - let length = self.len(); - if length > 0 && index < length && index != 0 { - self.swap(index, 0); - } else if index >= length { - return None; - } - self.pop_front() - } - - /// Removes an element from anywhere in the `VecDeque` and returns it, replacing it with the - /// last element. - /// - /// This does not preserve ordering, but is *O*(1). - /// - /// Returns `None` if `index` is out of bounds. - /// - /// Element at index 0 is the front of the queue. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// assert_eq!(buf.swap_remove_back(0), None); - /// buf.push_back(1); - /// buf.push_back(2); - /// buf.push_back(3); - /// assert_eq!(buf, [1, 2, 3]); - /// - /// assert_eq!(buf.swap_remove_back(0), Some(1)); - /// assert_eq!(buf, [3, 2]); - /// ``` - #[stable(feature = "deque_extras_15", since = "1.5.0")] - pub fn swap_remove_back(&mut self, index: usize) -> Option { - let length = self.len(); - if length > 0 && index < length - 1 { - self.swap(index, length - 1); - } else if index >= length { - return None; - } - self.pop_back() - } - - /// Inserts an element at `index` within the `VecDeque`, shifting all elements with indices - /// greater than or equal to `index` towards the back. - /// - /// Element at index 0 is the front of the queue. - /// - /// # Panics - /// - /// Panics if `index` is greater than `VecDeque`'s length - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut vec_deque = VecDeque::new(); - /// vec_deque.push_back('a'); - /// vec_deque.push_back('b'); - /// vec_deque.push_back('c'); - /// assert_eq!(vec_deque, &['a', 'b', 'c']); - /// - /// vec_deque.insert(1, 'd'); - /// assert_eq!(vec_deque, &['a', 'd', 'b', 'c']); - /// ``` - #[stable(feature = "deque_extras_15", since = "1.5.0")] - pub fn insert(&mut self, index: usize, value: T) { - assert!(index <= self.len(), "index out of bounds"); - if self.is_full() { - self.grow(); - } - - // Move the least number of elements in the ring buffer and insert - // the given object - // - // At most len/2 - 1 elements will be moved. O(min(n, n-i)) - // - // There are three main cases: - // Elements are contiguous - // - special case when tail is 0 - // Elements are discontiguous and the insert is in the tail section - // Elements are discontiguous and the insert is in the head section - // - // For each of those there are two more cases: - // Insert is closer to tail - // Insert is closer to head - // - // Key: H - self.head - // T - self.tail - // o - Valid element - // I - Insertion element - // A - The element that should be after the insertion point - // M - Indicates element was moved - - let idx = self.wrap_add(self.tail, index); - - let distance_to_tail = index; - let distance_to_head = self.len() - index; - - let contiguous = self.is_contiguous(); - - match (contiguous, distance_to_tail <= distance_to_head, idx >= self.tail) { - (true, true, _) if index == 0 => { - // push_front - // - // T - // I H - // [A o o o o o o . . . . . . . . .] - // - // H T - // [A o o o o o o o . . . . . I] - // - - self.tail = self.wrap_sub(self.tail, 1); - } - (true, true, _) => { - unsafe { - // contiguous, insert closer to tail: - // - // T I H - // [. . . o o A o o o o . . . . . .] - // - // T H - // [. . o o I A o o o o . . . . . .] - // M M - // - // contiguous, insert closer to tail and tail is 0: - // - // - // T I H - // [o o A o o o o . . . . . . . . .] - // - // H T - // [o I A o o o o o . . . . . . . o] - // M M - - let new_tail = self.wrap_sub(self.tail, 1); - - self.copy(new_tail, self.tail, 1); - // Already moved the tail, so we only copy `index - 1` elements. - self.copy(self.tail, self.tail + 1, index - 1); - - self.tail = new_tail; - } - } - (true, false, _) => { - unsafe { - // contiguous, insert closer to head: - // - // T I H - // [. . . o o o o A o o . . . . . .] - // - // T H - // [. . . o o o o I A o o . . . . .] - // M M M - - self.copy(idx + 1, idx, self.head - idx); - self.head = self.wrap_add(self.head, 1); - } - } - (false, true, true) => { - unsafe { - // discontiguous, insert closer to tail, tail section: - // - // H T I - // [o o o o o o . . . . . o o A o o] - // - // H T - // [o o o o o o . . . . o o I A o o] - // M M - - self.copy(self.tail - 1, self.tail, index); - self.tail -= 1; - } - } - (false, false, true) => { - unsafe { - // discontiguous, insert closer to head, tail section: - // - // H T I - // [o o . . . . . . . o o o o o A o] - // - // H T - // [o o o . . . . . . o o o o o I A] - // M M M M - - // copy elements up to new head - self.copy(1, 0, self.head); - - // copy last element into empty spot at bottom of buffer - self.copy(0, self.cap() - 1, 1); - - // move elements from idx to end forward not including ^ element - self.copy(idx + 1, idx, self.cap() - 1 - idx); - - self.head += 1; - } - } - (false, true, false) if idx == 0 => { - unsafe { - // discontiguous, insert is closer to tail, head section, - // and is at index zero in the internal buffer: - // - // I H T - // [A o o o o o o o o o . . . o o o] - // - // H T - // [A o o o o o o o o o . . o o o I] - // M M M - - // copy elements up to new tail - self.copy(self.tail - 1, self.tail, self.cap() - self.tail); - - // copy last element into empty spot at bottom of buffer - self.copy(self.cap() - 1, 0, 1); - - self.tail -= 1; - } - } - (false, true, false) => { - unsafe { - // discontiguous, insert closer to tail, head section: - // - // I H T - // [o o o A o o o o o o . . . o o o] - // - // H T - // [o o I A o o o o o o . . o o o o] - // M M M M M M - - // copy elements up to new tail - self.copy(self.tail - 1, self.tail, self.cap() - self.tail); - - // copy last element into empty spot at bottom of buffer - self.copy(self.cap() - 1, 0, 1); - - // move elements from idx-1 to end forward not including ^ element - self.copy(0, 1, idx - 1); - - self.tail -= 1; - } - } - (false, false, false) => { - unsafe { - // discontiguous, insert closer to head, head section: - // - // I H T - // [o o o o A o o . . . . . . o o o] - // - // H T - // [o o o o I A o o . . . . . o o o] - // M M M - - self.copy(idx + 1, idx, self.head - idx); - self.head += 1; - } - } - } - - // tail might've been changed so we need to recalculate - let new_idx = self.wrap_add(self.tail, index); - unsafe { - self.buffer_write(new_idx, value); - } - } - - /// Removes and returns the element at `index` from the `VecDeque`. - /// Whichever end is closer to the removal point will be moved to make - /// room, and all the affected elements will be moved to new positions. - /// Returns `None` if `index` is out of bounds. - /// - /// Element at index 0 is the front of the queue. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(1); - /// buf.push_back(2); - /// buf.push_back(3); - /// assert_eq!(buf, [1, 2, 3]); - /// - /// assert_eq!(buf.remove(1), Some(2)); - /// assert_eq!(buf, [1, 3]); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn remove(&mut self, index: usize) -> Option { - if self.is_empty() || self.len() <= index { - return None; - } - - // There are three main cases: - // Elements are contiguous - // Elements are discontiguous and the removal is in the tail section - // Elements are discontiguous and the removal is in the head section - // - special case when elements are technically contiguous, - // but self.head = 0 - // - // For each of those there are two more cases: - // Insert is closer to tail - // Insert is closer to head - // - // Key: H - self.head - // T - self.tail - // o - Valid element - // x - Element marked for removal - // R - Indicates element that is being removed - // M - Indicates element was moved - - let idx = self.wrap_add(self.tail, index); - - let elem = unsafe { Some(self.buffer_read(idx)) }; - - let distance_to_tail = index; - let distance_to_head = self.len() - index; - - let contiguous = self.is_contiguous(); - - match (contiguous, distance_to_tail <= distance_to_head, idx >= self.tail) { - (true, true, _) => { - unsafe { - // contiguous, remove closer to tail: - // - // T R H - // [. . . o o x o o o o . . . . . .] - // - // T H - // [. . . . o o o o o o . . . . . .] - // M M - - self.copy(self.tail + 1, self.tail, index); - self.tail += 1; - } - } - (true, false, _) => { - unsafe { - // contiguous, remove closer to head: - // - // T R H - // [. . . o o o o x o o . . . . . .] - // - // T H - // [. . . o o o o o o . . . . . . .] - // M M - - self.copy(idx, idx + 1, self.head - idx - 1); - self.head -= 1; - } - } - (false, true, true) => { - unsafe { - // discontiguous, remove closer to tail, tail section: - // - // H T R - // [o o o o o o . . . . . o o x o o] - // - // H T - // [o o o o o o . . . . . . o o o o] - // M M - - self.copy(self.tail + 1, self.tail, index); - self.tail = self.wrap_add(self.tail, 1); - } - } - (false, false, false) => { - unsafe { - // discontiguous, remove closer to head, head section: - // - // R H T - // [o o o o x o o . . . . . . o o o] - // - // H T - // [o o o o o o . . . . . . . o o o] - // M M - - self.copy(idx, idx + 1, self.head - idx - 1); - self.head -= 1; - } - } - (false, false, true) => { - unsafe { - // discontiguous, remove closer to head, tail section: - // - // H T R - // [o o o . . . . . . o o o o o x o] - // - // H T - // [o o . . . . . . . o o o o o o o] - // M M M M - // - // or quasi-discontiguous, remove next to head, tail section: - // - // H T R - // [. . . . . . . . . o o o o o x o] - // - // T H - // [. . . . . . . . . o o o o o o .] - // M - - // draw in elements in the tail section - self.copy(idx, idx + 1, self.cap() - idx - 1); - - // Prevents underflow. - if self.head != 0 { - // copy first element into empty spot - self.copy(self.cap() - 1, 0, 1); - - // move elements in the head section backwards - self.copy(0, 1, self.head - 1); - } - - self.head = self.wrap_sub(self.head, 1); - } - } - (false, true, false) => { - unsafe { - // discontiguous, remove closer to tail, head section: - // - // R H T - // [o o x o o o o o o o . . . o o o] - // - // H T - // [o o o o o o o o o o . . . . o o] - // M M M M M - - // draw in elements up to idx - self.copy(1, 0, idx); - - // copy last element into empty spot - self.copy(0, self.cap() - 1, 1); - - // move elements from tail to end forward, excluding the last one - self.copy(self.tail + 1, self.tail, self.cap() - self.tail - 1); - - self.tail = self.wrap_add(self.tail, 1); - } - } - } - - elem - } - - /// Splits the `VecDeque` into two at the given index. - /// - /// Returns a newly allocated `VecDeque`. `self` contains elements `[0, at)`, - /// and the returned `VecDeque` contains elements `[at, len)`. - /// - /// Note that the capacity of `self` does not change. - /// - /// Element at index 0 is the front of the queue. - /// - /// # Panics - /// - /// Panics if `at > len`. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf: VecDeque<_> = vec![1,2,3].into_iter().collect(); - /// let buf2 = buf.split_off(1); - /// assert_eq!(buf, [1]); - /// assert_eq!(buf2, [2, 3]); - /// ``` - #[inline] - #[must_use = "use `.truncate()` if you don't need the other half"] - #[stable(feature = "split_off", since = "1.4.0")] - pub fn split_off(&mut self, at: usize) -> Self { - let len = self.len(); - assert!(at <= len, "`at` out of bounds"); - - let other_len = len - at; - let mut other = VecDeque::with_capacity(other_len); - - unsafe { - let (first_half, second_half) = self.as_slices(); - - let first_len = first_half.len(); - let second_len = second_half.len(); - if at < first_len { - // `at` lies in the first half. - let amount_in_first = first_len - at; - - ptr::copy_nonoverlapping(first_half.as_ptr().add(at), other.ptr(), amount_in_first); - - // just take all of the second half. - ptr::copy_nonoverlapping( - second_half.as_ptr(), - other.ptr().add(amount_in_first), - second_len, - ); - } else { - // `at` lies in the second half, need to factor in the elements we skipped - // in the first half. - let offset = at - first_len; - let amount_in_second = second_len - offset; - ptr::copy_nonoverlapping( - second_half.as_ptr().add(offset), - other.ptr(), - amount_in_second, - ); - } - } - - // Cleanup where the ends of the buffers are - self.head = self.wrap_sub(self.head, other_len); - other.head = other.wrap_index(other_len); - - other - } - - /// Moves all the elements of `other` into `self`, leaving `other` empty. - /// - /// # Panics - /// - /// Panics if the new number of elements in self overflows a `usize`. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf: VecDeque<_> = vec![1, 2].into_iter().collect(); - /// let mut buf2: VecDeque<_> = vec![3, 4].into_iter().collect(); - /// buf.append(&mut buf2); - /// assert_eq!(buf, [1, 2, 3, 4]); - /// assert_eq!(buf2, []); - /// ``` - #[inline] - #[stable(feature = "append", since = "1.4.0")] - pub fn append(&mut self, other: &mut Self) { - // naive impl - self.extend(other.drain(..)); - } - - /// Retains only the elements specified by the predicate. - /// - /// In other words, remove all elements `e` such that `f(&e)` returns false. - /// This method operates in place, visiting each element exactly once in the - /// original order, and preserves the order of the retained elements. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.extend(1..5); - /// buf.retain(|&x| x % 2 == 0); - /// assert_eq!(buf, [2, 4]); - /// ``` - /// - /// The exact order may be useful for tracking external state, like an index. - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.extend(1..6); - /// - /// let keep = [false, true, true, false, true]; - /// let mut i = 0; - /// buf.retain(|_| (keep[i], i += 1).0); - /// assert_eq!(buf, [2, 3, 5]); - /// ``` - #[stable(feature = "vec_deque_retain", since = "1.4.0")] - pub fn retain(&mut self, mut f: F) - where - F: FnMut(&T) -> bool, - { - let len = self.len(); - let mut del = 0; - for i in 0..len { - if !f(&self[i]) { - del += 1; - } else if del > 0 { - self.swap(i - del, i); - } - } - if del > 0 { - self.truncate(len - del); - } - } - - // This may panic or abort - #[inline(never)] - fn grow(&mut self) { - if self.is_full() { - let old_cap = self.cap(); - // Double the buffer size. - self.buf.reserve_exact(old_cap, old_cap); - assert!(self.cap() == old_cap * 2); - unsafe { - self.handle_capacity_increase(old_cap); - } - debug_assert!(!self.is_full()); - } - } - - /// Modifies the `VecDeque` in-place so that `len()` is equal to `new_len`, - /// either by removing excess elements from the back or by appending - /// elements generated by calling `generator` to the back. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(5); - /// buf.push_back(10); - /// buf.push_back(15); - /// assert_eq!(buf, [5, 10, 15]); - /// - /// buf.resize_with(5, Default::default); - /// assert_eq!(buf, [5, 10, 15, 0, 0]); - /// - /// buf.resize_with(2, || unreachable!()); - /// assert_eq!(buf, [5, 10]); - /// - /// let mut state = 100; - /// buf.resize_with(5, || { state += 1; state }); - /// assert_eq!(buf, [5, 10, 101, 102, 103]); - /// ``` - #[stable(feature = "vec_resize_with", since = "1.33.0")] - pub fn resize_with(&mut self, new_len: usize, generator: impl FnMut() -> T) { - let len = self.len(); - - if new_len > len { - self.extend(repeat_with(generator).take(new_len - len)) - } else { - self.truncate(new_len); - } - } - - /// Rearranges the internal storage of this deque so it is one contiguous - /// slice, which is then returned. - /// - /// This method does not allocate and does not change the order of the - /// inserted elements. As it returns a mutable slice, this can be used to - /// sort a deque. - /// - /// Once the internal storage is contiguous, the [`as_slices`] and - /// [`as_mut_slices`] methods will return the entire contents of the - /// `VecDeque` in a single slice. - /// - /// [`as_slices`]: VecDeque::as_slices - /// [`as_mut_slices`]: VecDeque::as_mut_slices - /// - /// # Examples - /// - /// Sorting the content of a deque. - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::with_capacity(15); - /// - /// buf.push_back(2); - /// buf.push_back(1); - /// buf.push_front(3); - /// - /// // sorting the deque - /// buf.make_contiguous().sort(); - /// assert_eq!(buf.as_slices(), (&[1, 2, 3] as &[_], &[] as &[_])); - /// - /// // sorting it in reverse order - /// buf.make_contiguous().sort_by(|a, b| b.cmp(a)); - /// assert_eq!(buf.as_slices(), (&[3, 2, 1] as &[_], &[] as &[_])); - /// ``` - /// - /// Getting immutable access to the contiguous slice. - /// - /// ```rust - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// - /// buf.push_back(2); - /// buf.push_back(1); - /// buf.push_front(3); - /// - /// buf.make_contiguous(); - /// if let (slice, &[]) = buf.as_slices() { - /// // we can now be sure that `slice` contains all elements of the deque, - /// // while still having immutable access to `buf`. - /// assert_eq!(buf.len(), slice.len()); - /// assert_eq!(slice, &[3, 2, 1] as &[_]); - /// } - /// ``` - #[stable(feature = "deque_make_contiguous", since = "1.48.0")] - pub fn make_contiguous(&mut self) -> &mut [T] { - if self.is_contiguous() { - let tail = self.tail; - let head = self.head; - return unsafe { &mut self.buffer_as_mut_slice()[tail..head] }; - } - - let buf = self.buf.ptr(); - let cap = self.cap(); - let len = self.len(); - - let free = self.tail - self.head; - let tail_len = cap - self.tail; - - if free >= tail_len { - // there is enough free space to copy the tail in one go, - // this means that we first shift the head backwards, and then - // copy the tail to the correct position. - // - // from: DEFGH....ABC - // to: ABCDEFGH.... - unsafe { - ptr::copy(buf, buf.add(tail_len), self.head); - // ...DEFGH.ABC - ptr::copy_nonoverlapping(buf.add(self.tail), buf, tail_len); - // ABCDEFGH.... - - self.tail = 0; - self.head = len; - } - } else if free >= self.head { - // there is enough free space to copy the head in one go, - // this means that we first shift the tail forwards, and then - // copy the head to the correct position. - // - // from: FGH....ABCDE - // to: ...ABCDEFGH. - unsafe { - ptr::copy(buf.add(self.tail), buf.add(self.head), tail_len); - // FGHABCDE.... - ptr::copy_nonoverlapping(buf, buf.add(self.head + tail_len), self.head); - // ...ABCDEFGH. - - self.tail = self.head; - self.head = self.tail + len; - } - } else { - // free is smaller than both head and tail, - // this means we have to slowly "swap" the tail and the head. - // - // from: EFGHI...ABCD or HIJK.ABCDEFG - // to: ABCDEFGHI... or ABCDEFGHIJK. - let mut left_edge: usize = 0; - let mut right_edge: usize = self.tail; - unsafe { - // The general problem looks like this - // GHIJKLM...ABCDEF - before any swaps - // ABCDEFM...GHIJKL - after 1 pass of swaps - // ABCDEFGHIJM...KL - swap until the left edge reaches the temp store - // - then restart the algorithm with a new (smaller) store - // Sometimes the temp store is reached when the right edge is at the end - // of the buffer - this means we've hit the right order with fewer swaps! - // E.g - // EF..ABCD - // ABCDEF.. - after four only swaps we've finished - while left_edge < len && right_edge != cap { - let mut right_offset = 0; - for i in left_edge..right_edge { - right_offset = (i - left_edge) % (cap - right_edge); - let src: isize = (right_edge + right_offset) as isize; - ptr::swap(buf.add(i), buf.offset(src)); - } - let n_ops = right_edge - left_edge; - left_edge += n_ops; - right_edge += right_offset + 1; - } - - self.tail = 0; - self.head = len; - } - } - - let tail = self.tail; - let head = self.head; - unsafe { &mut self.buffer_as_mut_slice()[tail..head] } - } - - /// Rotates the double-ended queue `mid` places to the left. - /// - /// Equivalently, - /// - Rotates item `mid` into the first position. - /// - Pops the first `mid` items and pushes them to the end. - /// - Rotates `len() - mid` places to the right. - /// - /// # Panics - /// - /// If `mid` is greater than `len()`. Note that `mid == len()` - /// does _not_ panic and is a no-op rotation. - /// - /// # Complexity - /// - /// Takes `*O*(min(mid, len() - mid))` time and no extra space. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf: VecDeque<_> = (0..10).collect(); - /// - /// buf.rotate_left(3); - /// assert_eq!(buf, [3, 4, 5, 6, 7, 8, 9, 0, 1, 2]); - /// - /// for i in 1..10 { - /// assert_eq!(i * 3 % 10, buf[0]); - /// buf.rotate_left(3); - /// } - /// assert_eq!(buf, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]); - /// ``` - #[stable(feature = "vecdeque_rotate", since = "1.36.0")] - pub fn rotate_left(&mut self, mid: usize) { - assert!(mid <= self.len()); - let k = self.len() - mid; - if mid <= k { - unsafe { self.rotate_left_inner(mid) } - } else { - unsafe { self.rotate_right_inner(k) } - } - } - - /// Rotates the double-ended queue `k` places to the right. - /// - /// Equivalently, - /// - Rotates the first item into position `k`. - /// - Pops the last `k` items and pushes them to the front. - /// - Rotates `len() - k` places to the left. - /// - /// # Panics - /// - /// If `k` is greater than `len()`. Note that `k == len()` - /// does _not_ panic and is a no-op rotation. - /// - /// # Complexity - /// - /// Takes `*O*(min(k, len() - k))` time and no extra space. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf: VecDeque<_> = (0..10).collect(); - /// - /// buf.rotate_right(3); - /// assert_eq!(buf, [7, 8, 9, 0, 1, 2, 3, 4, 5, 6]); - /// - /// for i in 1..10 { - /// assert_eq!(0, buf[i * 3 % 10]); - /// buf.rotate_right(3); - /// } - /// assert_eq!(buf, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]); - /// ``` - #[stable(feature = "vecdeque_rotate", since = "1.36.0")] - pub fn rotate_right(&mut self, k: usize) { - assert!(k <= self.len()); - let mid = self.len() - k; - if k <= mid { - unsafe { self.rotate_right_inner(k) } - } else { - unsafe { self.rotate_left_inner(mid) } - } - } - - // SAFETY: the following two methods require that the rotation amount - // be less than half the length of the deque. - // - // `wrap_copy` requires that `min(x, cap() - x) + copy_len <= cap()`, - // but than `min` is never more than half the capacity, regardless of x, - // so it's sound to call here because we're calling with something - // less than half the length, which is never above half the capacity. - - unsafe fn rotate_left_inner(&mut self, mid: usize) { - debug_assert!(mid * 2 <= self.len()); - unsafe { - self.wrap_copy(self.head, self.tail, mid); - } - self.head = self.wrap_add(self.head, mid); - self.tail = self.wrap_add(self.tail, mid); - } - - unsafe fn rotate_right_inner(&mut self, k: usize) { - debug_assert!(k * 2 <= self.len()); - self.head = self.wrap_sub(self.head, k); - self.tail = self.wrap_sub(self.tail, k); - unsafe { - self.wrap_copy(self.tail, self.head, k); - } - } - - /// Binary searches this sorted `VecDeque` for a given element. - /// - /// If the value is found then [`Result::Ok`] is returned, containing the - /// index of the matching element. If there are multiple matches, then any - /// one of the matches could be returned. If the value is not found then - /// [`Result::Err`] is returned, containing the index where a matching - /// element could be inserted while maintaining sorted order. - /// - /// # Examples - /// - /// Looks up a series of four elements. The first is found, with a - /// uniquely determined position; the second and third are not - /// found; the fourth could match any position in `[1, 4]`. - /// - /// ``` - /// #![feature(vecdeque_binary_search)] - /// use std::collections::VecDeque; - /// - /// let deque: VecDeque<_> = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into(); - /// - /// assert_eq!(deque.binary_search(&13), Ok(9)); - /// assert_eq!(deque.binary_search(&4), Err(7)); - /// assert_eq!(deque.binary_search(&100), Err(13)); - /// let r = deque.binary_search(&1); - /// assert!(matches!(r, Ok(1..=4))); - /// ``` - /// - /// If you want to insert an item to a sorted `VecDeque`, while maintaining - /// sort order: - /// - /// ``` - /// #![feature(vecdeque_binary_search)] - /// use std::collections::VecDeque; - /// - /// let mut deque: VecDeque<_> = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into(); - /// let num = 42; - /// let idx = deque.binary_search(&num).unwrap_or_else(|x| x); - /// deque.insert(idx, num); - /// assert_eq!(deque, &[0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]); - /// ``` - #[unstable(feature = "vecdeque_binary_search", issue = "78021")] - #[inline] - pub fn binary_search(&self, x: &T) -> Result - where - T: Ord, - { - self.binary_search_by(|e| e.cmp(x)) - } - - /// Binary searches this sorted `VecDeque` with a comparator function. - /// - /// The comparator function should implement an order consistent - /// with the sort order of the underlying `VecDeque`, returning an - /// order code that indicates whether its argument is `Less`, - /// `Equal` or `Greater` than the desired target. - /// - /// If the value is found then [`Result::Ok`] is returned, containing the - /// index of the matching element. If there are multiple matches, then any - /// one of the matches could be returned. If the value is not found then - /// [`Result::Err`] is returned, containing the index where a matching - /// element could be inserted while maintaining sorted order. - /// - /// # Examples - /// - /// Looks up a series of four elements. The first is found, with a - /// uniquely determined position; the second and third are not - /// found; the fourth could match any position in `[1, 4]`. - /// - /// ``` - /// #![feature(vecdeque_binary_search)] - /// use std::collections::VecDeque; - /// - /// let deque: VecDeque<_> = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into(); - /// - /// assert_eq!(deque.binary_search_by(|x| x.cmp(&13)), Ok(9)); - /// assert_eq!(deque.binary_search_by(|x| x.cmp(&4)), Err(7)); - /// assert_eq!(deque.binary_search_by(|x| x.cmp(&100)), Err(13)); - /// let r = deque.binary_search_by(|x| x.cmp(&1)); - /// assert!(matches!(r, Ok(1..=4))); - /// ``` - #[unstable(feature = "vecdeque_binary_search", issue = "78021")] - pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result - where - F: FnMut(&'a T) -> Ordering, - { - let (front, back) = self.as_slices(); - - if let Some(Ordering::Less | Ordering::Equal) = back.first().map(|elem| f(elem)) { - back.binary_search_by(f).map(|idx| idx + front.len()).map_err(|idx| idx + front.len()) - } else { - front.binary_search_by(f) - } - } - - /// Binary searches this sorted `VecDeque` with a key extraction function. - /// - /// Assumes that the `VecDeque` is sorted by the key, for instance with - /// [`make_contiguous().sort_by_key()`](#method.make_contiguous) using the same - /// key extraction function. - /// - /// If the value is found then [`Result::Ok`] is returned, containing the - /// index of the matching element. If there are multiple matches, then any - /// one of the matches could be returned. If the value is not found then - /// [`Result::Err`] is returned, containing the index where a matching - /// element could be inserted while maintaining sorted order. - /// - /// # Examples - /// - /// Looks up a series of four elements in a slice of pairs sorted by - /// their second elements. The first is found, with a uniquely - /// determined position; the second and third are not found; the - /// fourth could match any position in `[1, 4]`. - /// - /// ``` - /// #![feature(vecdeque_binary_search)] - /// use std::collections::VecDeque; - /// - /// let deque: VecDeque<_> = vec![(0, 0), (2, 1), (4, 1), (5, 1), - /// (3, 1), (1, 2), (2, 3), (4, 5), (5, 8), (3, 13), - /// (1, 21), (2, 34), (4, 55)].into(); - /// - /// assert_eq!(deque.binary_search_by_key(&13, |&(a,b)| b), Ok(9)); - /// assert_eq!(deque.binary_search_by_key(&4, |&(a,b)| b), Err(7)); - /// assert_eq!(deque.binary_search_by_key(&100, |&(a,b)| b), Err(13)); - /// let r = deque.binary_search_by_key(&1, |&(a,b)| b); - /// assert!(matches!(r, Ok(1..=4))); - /// ``` - #[unstable(feature = "vecdeque_binary_search", issue = "78021")] - #[inline] - pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result - where - F: FnMut(&'a T) -> B, - B: Ord, - { - self.binary_search_by(|k| f(k).cmp(b)) - } -} - -impl VecDeque { - /// Modifies the `VecDeque` in-place so that `len()` is equal to new_len, - /// either by removing excess elements from the back or by appending clones of `value` - /// to the back. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// let mut buf = VecDeque::new(); - /// buf.push_back(5); - /// buf.push_back(10); - /// buf.push_back(15); - /// assert_eq!(buf, [5, 10, 15]); - /// - /// buf.resize(2, 0); - /// assert_eq!(buf, [5, 10]); - /// - /// buf.resize(5, 20); - /// assert_eq!(buf, [5, 10, 20, 20, 20]); - /// ``` - #[stable(feature = "deque_extras", since = "1.16.0")] - pub fn resize(&mut self, new_len: usize, value: T) { - self.resize_with(new_len, || value.clone()); - } -} - -/// Returns the index in the underlying buffer for a given logical element index. -#[inline] -fn wrap_index(index: usize, size: usize) -> usize { - // size is always a power of 2 - debug_assert!(size.is_power_of_two()); - index & (size - 1) -} - -/// Returns the two slices that cover the `VecDeque`'s valid range -trait RingSlices: Sized { - fn slice(self, from: usize, to: usize) -> Self; - fn split_at(self, i: usize) -> (Self, Self); - - fn ring_slices(buf: Self, head: usize, tail: usize) -> (Self, Self) { - let contiguous = tail <= head; - if contiguous { - let (empty, buf) = buf.split_at(0); - (buf.slice(tail, head), empty) - } else { - let (mid, right) = buf.split_at(tail); - let (left, _) = mid.split_at(head); - (right, left) - } - } -} - -impl RingSlices for &[T] { - fn slice(self, from: usize, to: usize) -> Self { - &self[from..to] - } - fn split_at(self, i: usize) -> (Self, Self) { - (*self).split_at(i) - } -} - -impl RingSlices for &mut [T] { - fn slice(self, from: usize, to: usize) -> Self { - &mut self[from..to] - } - fn split_at(self, i: usize) -> (Self, Self) { - (*self).split_at_mut(i) - } -} - -impl RingSlices for *mut [T] { - fn slice(self, from: usize, to: usize) -> Self { - assert!(from <= to && to < self.len()); - // Not using `get_unchecked_mut` to keep this a safe operation. - let len = to - from; - ptr::slice_from_raw_parts_mut(self.as_mut_ptr().wrapping_add(from), len) - } - - fn split_at(self, mid: usize) -> (Self, Self) { - let len = self.len(); - let ptr = self.as_mut_ptr(); - assert!(mid <= len); - ( - ptr::slice_from_raw_parts_mut(ptr, mid), - ptr::slice_from_raw_parts_mut(ptr.wrapping_add(mid), len - mid), - ) - } -} - -/// Calculate the number of elements left to be read in the buffer -#[inline] -fn count(tail: usize, head: usize, size: usize) -> usize { - // size is always a power of 2 - (head.wrapping_sub(tail)) & (size - 1) -} - -/// An iterator over the elements of a `VecDeque`. -/// -/// This `struct` is created by the [`iter`] method on [`VecDeque`]. See its -/// documentation for more. -/// -/// [`iter`]: VecDeque::iter -#[stable(feature = "rust1", since = "1.0.0")] -pub struct Iter<'a, T: 'a> { - ring: &'a [T], - tail: usize, - head: usize, -} - -#[stable(feature = "collection_debug", since = "1.17.0")] -impl fmt::Debug for Iter<'_, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); - f.debug_tuple("Iter").field(&front).field(&back).finish() - } -} - -// FIXME(#26925) Remove in favor of `#[derive(Clone)]` -#[stable(feature = "rust1", since = "1.0.0")] -impl Clone for Iter<'_, T> { - fn clone(&self) -> Self { - Iter { ring: self.ring, tail: self.tail, head: self.head } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> Iterator for Iter<'a, T> { - type Item = &'a T; - - #[inline] - fn next(&mut self) -> Option<&'a T> { - if self.tail == self.head { - return None; - } - let tail = self.tail; - self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len()); - unsafe { Some(self.ring.get_unchecked(tail)) } - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let len = count(self.tail, self.head, self.ring.len()); - (len, Some(len)) - } - - fn fold(self, mut accum: Acc, mut f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); - accum = front.iter().fold(accum, &mut f); - back.iter().fold(accum, &mut f) - } - - fn try_fold(&mut self, init: B, mut f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - let (mut iter, final_res); - if self.tail <= self.head { - // single slice self.ring[self.tail..self.head] - iter = self.ring[self.tail..self.head].iter(); - final_res = iter.try_fold(init, &mut f); - } else { - // two slices: self.ring[self.tail..], self.ring[..self.head] - let (front, back) = self.ring.split_at(self.tail); - let mut back_iter = back.iter(); - let res = back_iter.try_fold(init, &mut f); - let len = self.ring.len(); - self.tail = (self.ring.len() - back_iter.len()) & (len - 1); - iter = front[..self.head].iter(); - final_res = iter.try_fold(res?, &mut f); - } - self.tail = self.head - iter.len(); - final_res - } - - fn nth(&mut self, n: usize) -> Option { - if n >= count(self.tail, self.head, self.ring.len()) { - self.tail = self.head; - None - } else { - self.tail = wrap_index(self.tail.wrapping_add(n), self.ring.len()); - self.next() - } - } - - #[inline] - fn last(mut self) -> Option<&'a T> { - self.next_back() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> DoubleEndedIterator for Iter<'a, T> { - #[inline] - fn next_back(&mut self) -> Option<&'a T> { - if self.tail == self.head { - return None; - } - self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len()); - unsafe { Some(self.ring.get_unchecked(self.head)) } - } - - fn rfold(self, mut accum: Acc, mut f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); - accum = back.iter().rfold(accum, &mut f); - front.iter().rfold(accum, &mut f) - } - - fn try_rfold(&mut self, init: B, mut f: F) -> R - where - Self: Sized, - F: FnMut(B, Self::Item) -> R, - R: Try, - { - let (mut iter, final_res); - if self.tail <= self.head { - // single slice self.ring[self.tail..self.head] - iter = self.ring[self.tail..self.head].iter(); - final_res = iter.try_rfold(init, &mut f); - } else { - // two slices: self.ring[self.tail..], self.ring[..self.head] - let (front, back) = self.ring.split_at(self.tail); - let mut front_iter = front[..self.head].iter(); - let res = front_iter.try_rfold(init, &mut f); - self.head = front_iter.len(); - iter = back.iter(); - final_res = iter.try_rfold(res?, &mut f); - } - self.head = self.tail + iter.len(); - final_res - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for Iter<'_, T> { - fn is_empty(&self) -> bool { - self.head == self.tail - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for Iter<'_, T> {} - -/// A mutable iterator over the elements of a `VecDeque`. -/// -/// This `struct` is created by the [`iter_mut`] method on [`VecDeque`]. See its -/// documentation for more. -/// -/// [`iter_mut`]: VecDeque::iter_mut -#[stable(feature = "rust1", since = "1.0.0")] -pub struct IterMut<'a, T: 'a> { - // Internal safety invariant: the entire slice is dereferencable. - ring: *mut [T], - tail: usize, - head: usize, - phantom: PhantomData<&'a mut [T]>, -} - -// SAFETY: we do nothing thread-local and there is no interior mutability, -// so the usual structural `Send`/`Sync` apply. -#[stable(feature = "rust1", since = "1.0.0")] -unsafe impl Send for IterMut<'_, T> {} -#[stable(feature = "rust1", since = "1.0.0")] -unsafe impl Sync for IterMut<'_, T> {} - -#[stable(feature = "collection_debug", since = "1.17.0")] -impl fmt::Debug for IterMut<'_, T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); - // SAFETY: these are the elements we have not handed out yet, so aliasing is fine. - // The `IterMut` invariant also ensures everything is dereferencable. - let (front, back) = unsafe { (&*front, &*back) }; - f.debug_tuple("IterMut").field(&front).field(&back).finish() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> Iterator for IterMut<'a, T> { - type Item = &'a mut T; - - #[inline] - fn next(&mut self) -> Option<&'a mut T> { - if self.tail == self.head { - return None; - } - let tail = self.tail; - self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len()); - - unsafe { - let elem = self.ring.get_unchecked_mut(tail); - Some(&mut *elem) - } - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let len = count(self.tail, self.head, self.ring.len()); - (len, Some(len)) - } - - fn fold(self, mut accum: Acc, mut f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); - // SAFETY: these are the elements we have not handed out yet, so aliasing is fine. - // The `IterMut` invariant also ensures everything is dereferencable. - let (front, back) = unsafe { (&mut *front, &mut *back) }; - accum = front.iter_mut().fold(accum, &mut f); - back.iter_mut().fold(accum, &mut f) - } - - fn nth(&mut self, n: usize) -> Option { - if n >= count(self.tail, self.head, self.ring.len()) { - self.tail = self.head; - None - } else { - self.tail = wrap_index(self.tail.wrapping_add(n), self.ring.len()); - self.next() - } - } - - #[inline] - fn last(mut self) -> Option<&'a mut T> { - self.next_back() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> DoubleEndedIterator for IterMut<'a, T> { - #[inline] - fn next_back(&mut self) -> Option<&'a mut T> { - if self.tail == self.head { - return None; - } - self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len()); - - unsafe { - let elem = self.ring.get_unchecked_mut(self.head); - Some(&mut *elem) - } - } - - fn rfold(self, mut accum: Acc, mut f: F) -> Acc - where - F: FnMut(Acc, Self::Item) -> Acc, - { - let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); - // SAFETY: these are the elements we have not handed out yet, so aliasing is fine. - // The `IterMut` invariant also ensures everything is dereferencable. - let (front, back) = unsafe { (&mut *front, &mut *back) }; - accum = back.iter_mut().rfold(accum, &mut f); - front.iter_mut().rfold(accum, &mut f) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for IterMut<'_, T> { - fn is_empty(&self) -> bool { - self.head == self.tail - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for IterMut<'_, T> {} - -/// An owning iterator over the elements of a `VecDeque`. -/// -/// This `struct` is created by the [`into_iter`] method on [`VecDeque`] -/// (provided by the `IntoIterator` trait). See its documentation for more. -/// -/// [`into_iter`]: VecDeque::into_iter -#[derive(Clone)] -#[stable(feature = "rust1", since = "1.0.0")] -pub struct IntoIter { - inner: VecDeque, -} - -#[stable(feature = "collection_debug", since = "1.17.0")] -impl fmt::Debug for IntoIter { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_tuple("IntoIter").field(&self.inner).finish() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Iterator for IntoIter { - type Item = T; - - #[inline] - fn next(&mut self) -> Option { - self.inner.pop_front() - } - - #[inline] - fn size_hint(&self) -> (usize, Option) { - let len = self.inner.len(); - (len, Some(len)) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl DoubleEndedIterator for IntoIter { - #[inline] - fn next_back(&mut self) -> Option { - self.inner.pop_back() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl ExactSizeIterator for IntoIter { - fn is_empty(&self) -> bool { - self.inner.is_empty() - } -} - -#[stable(feature = "fused", since = "1.26.0")] -impl FusedIterator for IntoIter {} - -#[stable(feature = "rust1", since = "1.0.0")] -impl PartialEq for VecDeque { - fn eq(&self, other: &VecDeque) -> bool { - if self.len() != other.len() { - return false; - } - let (sa, sb) = self.as_slices(); - let (oa, ob) = other.as_slices(); - if sa.len() == oa.len() { - sa == oa && sb == ob - } else if sa.len() < oa.len() { - // Always divisible in three sections, for example: - // self: [a b c|d e f] - // other: [0 1 2 3|4 5] - // front = 3, mid = 1, - // [a b c] == [0 1 2] && [d] == [3] && [e f] == [4 5] - let front = sa.len(); - let mid = oa.len() - front; - - let (oa_front, oa_mid) = oa.split_at(front); - let (sb_mid, sb_back) = sb.split_at(mid); - debug_assert_eq!(sa.len(), oa_front.len()); - debug_assert_eq!(sb_mid.len(), oa_mid.len()); - debug_assert_eq!(sb_back.len(), ob.len()); - sa == oa_front && sb_mid == oa_mid && sb_back == ob - } else { - let front = oa.len(); - let mid = sa.len() - front; - - let (sa_front, sa_mid) = sa.split_at(front); - let (ob_mid, ob_back) = ob.split_at(mid); - debug_assert_eq!(sa_front.len(), oa.len()); - debug_assert_eq!(sa_mid.len(), ob_mid.len()); - debug_assert_eq!(sb.len(), ob_back.len()); - sa_front == oa && sa_mid == ob_mid && sb == ob_back - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Eq for VecDeque {} - -macro_rules! __impl_slice_eq1 { - ([$($vars:tt)*] $lhs:ty, $rhs:ty, $($constraints:tt)*) => { - #[stable(feature = "vec_deque_partial_eq_slice", since = "1.17.0")] - impl PartialEq<$rhs> for $lhs - where - A: PartialEq, - $($constraints)* - { - fn eq(&self, other: &$rhs) -> bool { - if self.len() != other.len() { - return false; - } - let (sa, sb) = self.as_slices(); - let (oa, ob) = other[..].split_at(sa.len()); - sa == oa && sb == ob - } - } - } -} - -__impl_slice_eq1! { [] VecDeque, Vec, } -__impl_slice_eq1! { [] VecDeque, &[B], } -__impl_slice_eq1! { [] VecDeque, &mut [B], } -__impl_slice_eq1! { [const N: usize] VecDeque, [B; N], } -__impl_slice_eq1! { [const N: usize] VecDeque, &[B; N], } -__impl_slice_eq1! { [const N: usize] VecDeque, &mut [B; N], } - -#[stable(feature = "rust1", since = "1.0.0")] -impl PartialOrd for VecDeque { - fn partial_cmp(&self, other: &VecDeque) -> Option { - self.iter().partial_cmp(other.iter()) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Ord for VecDeque { - #[inline] - fn cmp(&self, other: &VecDeque) -> Ordering { - self.iter().cmp(other.iter()) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Hash for VecDeque { - fn hash(&self, state: &mut H) { - self.len().hash(state); - let (a, b) = self.as_slices(); - Hash::hash_slice(a, state); - Hash::hash_slice(b, state); - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Index for VecDeque { - type Output = A; - - #[inline] - fn index(&self, index: usize) -> &A { - self.get(index).expect("Out of bounds access") - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl IndexMut for VecDeque { - #[inline] - fn index_mut(&mut self, index: usize) -> &mut A { - self.get_mut(index).expect("Out of bounds access") - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl FromIterator for VecDeque { - fn from_iter>(iter: T) -> VecDeque { - let iterator = iter.into_iter(); - let (lower, _) = iterator.size_hint(); - let mut deq = VecDeque::with_capacity(lower); - deq.extend(iterator); - deq - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl IntoIterator for VecDeque { - type Item = T; - type IntoIter = IntoIter; - - /// Consumes the `VecDeque` into a front-to-back iterator yielding elements by - /// value. - fn into_iter(self) -> IntoIter { - IntoIter { inner: self } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> IntoIterator for &'a VecDeque { - type Item = &'a T; - type IntoIter = Iter<'a, T>; - - fn into_iter(self) -> Iter<'a, T> { - self.iter() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, T> IntoIterator for &'a mut VecDeque { - type Item = &'a mut T; - type IntoIter = IterMut<'a, T>; - - fn into_iter(self) -> IterMut<'a, T> { - self.iter_mut() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl Extend for VecDeque { - fn extend>(&mut self, iter: T) { - // This function should be the moral equivalent of: - // - // for item in iter.into_iter() { - // self.push_back(item); - // } - let mut iter = iter.into_iter(); - while let Some(element) = iter.next() { - if self.len() == self.capacity() { - let (lower, _) = iter.size_hint(); - self.reserve(lower.saturating_add(1)); - } - - let head = self.head; - self.head = self.wrap_add(self.head, 1); - unsafe { - self.buffer_write(head, element); - } - } - } - - #[inline] - fn extend_one(&mut self, elem: A) { - self.push_back(elem); - } - - #[inline] - fn extend_reserve(&mut self, additional: usize) { - self.reserve(additional); - } -} - -#[stable(feature = "extend_ref", since = "1.2.0")] -impl<'a, T: 'a + Copy> Extend<&'a T> for VecDeque { - fn extend>(&mut self, iter: I) { - self.extend(iter.into_iter().cloned()); - } - - #[inline] - fn extend_one(&mut self, &elem: &T) { - self.push_back(elem); - } - - #[inline] - fn extend_reserve(&mut self, additional: usize) { - self.reserve(additional); - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl fmt::Debug for VecDeque { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_list().entries(self).finish() - } -} - -#[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")] -impl From> for VecDeque { - /// Turn a [`Vec`] into a [`VecDeque`]. - /// - /// [`Vec`]: crate::vec::Vec - /// [`VecDeque`]: crate::collections::VecDeque - /// - /// This avoids reallocating where possible, but the conditions for that are - /// strict, and subject to change, and so shouldn't be relied upon unless the - /// `Vec` came from `From>` and hasn't been reallocated. - fn from(other: Vec) -> Self { - unsafe { - let mut other = ManuallyDrop::new(other); - let other_buf = other.as_mut_ptr(); - let mut buf = RawVec::from_raw_parts(other_buf, other.capacity()); - let len = other.len(); - - // We need to extend the buf if it's not a power of two, too small - // or doesn't have at least one free space - if !buf.capacity().is_power_of_two() - || (buf.capacity() < (MINIMUM_CAPACITY + 1)) - || (buf.capacity() == len) - { - let cap = cmp::max(buf.capacity() + 1, MINIMUM_CAPACITY + 1).next_power_of_two(); - buf.reserve_exact(len, cap - len); - } - - VecDeque { tail: 0, head: len, buf } - } - } -} - -#[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")] -impl From> for Vec { - /// Turn a [`VecDeque`] into a [`Vec`]. - /// - /// [`Vec`]: crate::vec::Vec - /// [`VecDeque`]: crate::collections::VecDeque - /// - /// This never needs to re-allocate, but does need to do *O*(*n*) data movement if - /// the circular buffer doesn't happen to be at the beginning of the allocation. - /// - /// # Examples - /// - /// ``` - /// use std::collections::VecDeque; - /// - /// // This one is *O*(1). - /// let deque: VecDeque<_> = (1..5).collect(); - /// let ptr = deque.as_slices().0.as_ptr(); - /// let vec = Vec::from(deque); - /// assert_eq!(vec, [1, 2, 3, 4]); - /// assert_eq!(vec.as_ptr(), ptr); - /// - /// // This one needs data rearranging. - /// let mut deque: VecDeque<_> = (1..5).collect(); - /// deque.push_front(9); - /// deque.push_front(8); - /// let ptr = deque.as_slices().1.as_ptr(); - /// let vec = Vec::from(deque); - /// assert_eq!(vec, [8, 9, 1, 2, 3, 4]); - /// assert_eq!(vec.as_ptr(), ptr); - /// ``` - fn from(mut other: VecDeque) -> Self { - other.make_contiguous(); - - unsafe { - let other = ManuallyDrop::new(other); - let buf = other.buf.ptr(); - let len = other.len(); - let cap = other.cap(); - - if other.head != 0 { - ptr::copy(buf.add(other.tail), buf, len); - } - Vec::from_raw_parts(buf, len, cap) - } - } -} diff --git a/library/alloc/src/collections/vec_deque/into_iter.rs b/library/alloc/src/collections/vec_deque/into_iter.rs new file mode 100644 index 00000000000..465b058cd98 --- /dev/null +++ b/library/alloc/src/collections/vec_deque/into_iter.rs @@ -0,0 +1,57 @@ +use core::fmt; +use core::iter::FusedIterator; + +use super::VecDeque; + +/// An owning iterator over the elements of a `VecDeque`. +/// +/// This `struct` is created by the [`into_iter`] method on [`VecDeque`] +/// (provided by the `IntoIterator` trait). See its documentation for more. +/// +/// [`into_iter`]: VecDeque::into_iter +#[derive(Clone)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct IntoIter { + pub(crate) inner: VecDeque, +} + +#[stable(feature = "collection_debug", since = "1.17.0")] +impl fmt::Debug for IntoIter { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_tuple("IntoIter").field(&self.inner).finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Iterator for IntoIter { + type Item = T; + + #[inline] + fn next(&mut self) -> Option { + self.inner.pop_front() + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let len = self.inner.len(); + (len, Some(len)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl DoubleEndedIterator for IntoIter { + #[inline] + fn next_back(&mut self) -> Option { + self.inner.pop_back() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for IntoIter { + fn is_empty(&self) -> bool { + self.inner.is_empty() + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for IntoIter {} diff --git a/library/alloc/src/collections/vec_deque/iter.rs b/library/alloc/src/collections/vec_deque/iter.rs new file mode 100644 index 00000000000..ad31b991cb6 --- /dev/null +++ b/library/alloc/src/collections/vec_deque/iter.rs @@ -0,0 +1,159 @@ +use core::fmt; +use core::iter::FusedIterator; +use core::ops::Try; + +use super::{count, wrap_index, RingSlices}; + +/// An iterator over the elements of a `VecDeque`. +/// +/// This `struct` is created by the [`iter`] method on [`super::VecDeque`]. See its +/// documentation for more. +/// +/// [`iter`]: super::VecDeque::iter +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Iter<'a, T: 'a> { + pub(crate) ring: &'a [T], + pub(crate) tail: usize, + pub(crate) head: usize, +} + +#[stable(feature = "collection_debug", since = "1.17.0")] +impl fmt::Debug for Iter<'_, T> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); + f.debug_tuple("Iter").field(&front).field(&back).finish() + } +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[stable(feature = "rust1", since = "1.0.0")] +impl Clone for Iter<'_, T> { + fn clone(&self) -> Self { + Iter { ring: self.ring, tail: self.tail, head: self.head } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> Iterator for Iter<'a, T> { + type Item = &'a T; + + #[inline] + fn next(&mut self) -> Option<&'a T> { + if self.tail == self.head { + return None; + } + let tail = self.tail; + self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len()); + unsafe { Some(self.ring.get_unchecked(tail)) } + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let len = count(self.tail, self.head, self.ring.len()); + (len, Some(len)) + } + + fn fold(self, mut accum: Acc, mut f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); + accum = front.iter().fold(accum, &mut f); + back.iter().fold(accum, &mut f) + } + + fn try_fold(&mut self, init: B, mut f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + let (mut iter, final_res); + if self.tail <= self.head { + // single slice self.ring[self.tail..self.head] + iter = self.ring[self.tail..self.head].iter(); + final_res = iter.try_fold(init, &mut f); + } else { + // two slices: self.ring[self.tail..], self.ring[..self.head] + let (front, back) = self.ring.split_at(self.tail); + let mut back_iter = back.iter(); + let res = back_iter.try_fold(init, &mut f); + let len = self.ring.len(); + self.tail = (self.ring.len() - back_iter.len()) & (len - 1); + iter = front[..self.head].iter(); + final_res = iter.try_fold(res?, &mut f); + } + self.tail = self.head - iter.len(); + final_res + } + + fn nth(&mut self, n: usize) -> Option { + if n >= count(self.tail, self.head, self.ring.len()) { + self.tail = self.head; + None + } else { + self.tail = wrap_index(self.tail.wrapping_add(n), self.ring.len()); + self.next() + } + } + + #[inline] + fn last(mut self) -> Option<&'a T> { + self.next_back() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> DoubleEndedIterator for Iter<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a T> { + if self.tail == self.head { + return None; + } + self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len()); + unsafe { Some(self.ring.get_unchecked(self.head)) } + } + + fn rfold(self, mut accum: Acc, mut f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); + accum = back.iter().rfold(accum, &mut f); + front.iter().rfold(accum, &mut f) + } + + fn try_rfold(&mut self, init: B, mut f: F) -> R + where + Self: Sized, + F: FnMut(B, Self::Item) -> R, + R: Try, + { + let (mut iter, final_res); + if self.tail <= self.head { + // single slice self.ring[self.tail..self.head] + iter = self.ring[self.tail..self.head].iter(); + final_res = iter.try_rfold(init, &mut f); + } else { + // two slices: self.ring[self.tail..], self.ring[..self.head] + let (front, back) = self.ring.split_at(self.tail); + let mut front_iter = front[..self.head].iter(); + let res = front_iter.try_rfold(init, &mut f); + self.head = front_iter.len(); + iter = back.iter(); + final_res = iter.try_rfold(res?, &mut f); + } + self.head = self.tail + iter.len(); + final_res + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for Iter<'_, T> { + fn is_empty(&self) -> bool { + self.head == self.tail + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for Iter<'_, T> {} diff --git a/library/alloc/src/collections/vec_deque/iter_mut.rs b/library/alloc/src/collections/vec_deque/iter_mut.rs new file mode 100644 index 00000000000..3d0c3094e26 --- /dev/null +++ b/library/alloc/src/collections/vec_deque/iter_mut.rs @@ -0,0 +1,128 @@ +use core::fmt; +use core::iter::FusedIterator; +use core::marker::PhantomData; + +use super::{count, wrap_index, RingSlices}; + +/// A mutable iterator over the elements of a `VecDeque`. +/// +/// This `struct` is created by the [`iter_mut`] method on [`super::VecDeque`]. See its +/// documentation for more. +/// +/// [`iter_mut`]: super::VecDeque::iter_mut +#[stable(feature = "rust1", since = "1.0.0")] +pub struct IterMut<'a, T: 'a> { + // Internal safety invariant: the entire slice is dereferencable. + pub(crate) ring: *mut [T], + pub(crate) tail: usize, + pub(crate) head: usize, + pub(crate) phantom: PhantomData<&'a mut [T]>, +} + +// SAFETY: we do nothing thread-local and there is no interior mutability, +// so the usual structural `Send`/`Sync` apply. +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl Send for IterMut<'_, T> {} +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl Sync for IterMut<'_, T> {} + +#[stable(feature = "collection_debug", since = "1.17.0")] +impl fmt::Debug for IterMut<'_, T> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); + // SAFETY: these are the elements we have not handed out yet, so aliasing is fine. + // The `IterMut` invariant also ensures everything is dereferencable. + let (front, back) = unsafe { (&*front, &*back) }; + f.debug_tuple("IterMut").field(&front).field(&back).finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> Iterator for IterMut<'a, T> { + type Item = &'a mut T; + + #[inline] + fn next(&mut self) -> Option<&'a mut T> { + if self.tail == self.head { + return None; + } + let tail = self.tail; + self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len()); + + unsafe { + let elem = self.ring.get_unchecked_mut(tail); + Some(&mut *elem) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let len = count(self.tail, self.head, self.ring.len()); + (len, Some(len)) + } + + fn fold(self, mut accum: Acc, mut f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); + // SAFETY: these are the elements we have not handed out yet, so aliasing is fine. + // The `IterMut` invariant also ensures everything is dereferencable. + let (front, back) = unsafe { (&mut *front, &mut *back) }; + accum = front.iter_mut().fold(accum, &mut f); + back.iter_mut().fold(accum, &mut f) + } + + fn nth(&mut self, n: usize) -> Option { + if n >= count(self.tail, self.head, self.ring.len()) { + self.tail = self.head; + None + } else { + self.tail = wrap_index(self.tail.wrapping_add(n), self.ring.len()); + self.next() + } + } + + #[inline] + fn last(mut self) -> Option<&'a mut T> { + self.next_back() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> DoubleEndedIterator for IterMut<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a mut T> { + if self.tail == self.head { + return None; + } + self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len()); + + unsafe { + let elem = self.ring.get_unchecked_mut(self.head); + Some(&mut *elem) + } + } + + fn rfold(self, mut accum: Acc, mut f: F) -> Acc + where + F: FnMut(Acc, Self::Item) -> Acc, + { + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); + // SAFETY: these are the elements we have not handed out yet, so aliasing is fine. + // The `IterMut` invariant also ensures everything is dereferencable. + let (front, back) = unsafe { (&mut *front, &mut *back) }; + accum = back.iter_mut().rfold(accum, &mut f); + front.iter_mut().rfold(accum, &mut f) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl ExactSizeIterator for IterMut<'_, T> { + fn is_empty(&self) -> bool { + self.head == self.tail + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl FusedIterator for IterMut<'_, T> {} diff --git a/library/alloc/src/collections/vec_deque/macros.rs b/library/alloc/src/collections/vec_deque/macros.rs new file mode 100644 index 00000000000..0d59d312cf4 --- /dev/null +++ b/library/alloc/src/collections/vec_deque/macros.rs @@ -0,0 +1,19 @@ +macro_rules! __impl_slice_eq1 { + ([$($vars:tt)*] $lhs:ty, $rhs:ty, $($constraints:tt)*) => { + #[stable(feature = "vec_deque_partial_eq_slice", since = "1.17.0")] + impl PartialEq<$rhs> for $lhs + where + A: PartialEq, + $($constraints)* + { + fn eq(&self, other: &$rhs) -> bool { + if self.len() != other.len() { + return false; + } + let (sa, sb) = self.as_slices(); + let (oa, ob) = other[..].split_at(sa.len()); + sa == oa && sb == ob + } + } + } +} diff --git a/library/alloc/src/collections/vec_deque/mod.rs b/library/alloc/src/collections/vec_deque/mod.rs new file mode 100644 index 00000000000..1c183858e7a --- /dev/null +++ b/library/alloc/src/collections/vec_deque/mod.rs @@ -0,0 +1,2848 @@ +//! A double-ended queue implemented with a growable ring buffer. +//! +//! This queue has *O*(1) amortized inserts and removals from both ends of the +//! container. It also has *O*(1) indexing like a vector. The contained elements +//! are not required to be copyable, and the queue will be sendable if the +//! contained type is sendable. + +#![stable(feature = "rust1", since = "1.0.0")] + +use core::cmp::{self, Ordering}; +use core::fmt; +use core::hash::{Hash, Hasher}; +use core::iter::{repeat_with, FromIterator}; +use core::marker::PhantomData; +use core::mem::{self, ManuallyDrop}; +use core::ops::{Index, IndexMut, Range, RangeBounds}; +use core::ptr::{self, NonNull}; +use core::slice; + +use crate::collections::TryReserveError; +use crate::raw_vec::RawVec; +use crate::vec::Vec; + +#[macro_use] +mod macros; + +#[stable(feature = "drain", since = "1.6.0")] +pub use self::drain::Drain; + +mod drain; + +#[stable(feature = "rust1", since = "1.0.0")] +pub use self::iter_mut::IterMut; + +mod iter_mut; + +#[stable(feature = "rust1", since = "1.0.0")] +pub use self::into_iter::IntoIter; + +mod into_iter; + +#[stable(feature = "rust1", since = "1.0.0")] +pub use self::iter::Iter; + +mod iter; + +use self::pair_slices::PairSlices; + +mod pair_slices; + +use self::ring_slices::RingSlices; + +mod ring_slices; + +#[cfg(test)] +mod tests; + +const INITIAL_CAPACITY: usize = 7; // 2^3 - 1 +const MINIMUM_CAPACITY: usize = 1; // 2 - 1 + +const MAXIMUM_ZST_CAPACITY: usize = 1 << (core::mem::size_of::() * 8 - 1); // Largest possible power of two + +/// A double-ended queue implemented with a growable ring buffer. +/// +/// The "default" usage of this type as a queue is to use [`push_back`] to add to +/// the queue, and [`pop_front`] to remove from the queue. [`extend`] and [`append`] +/// push onto the back in this manner, and iterating over `VecDeque` goes front +/// to back. +/// +/// Since `VecDeque` is a ring buffer, its elements are not necessarily contiguous +/// in memory. If you want to access the elements as a single slice, such as for +/// efficient sorting, you can use [`make_contiguous`]. It rotates the `VecDeque` +/// so that its elements do not wrap, and returns a mutable slice to the +/// now-contiguous element sequence. +/// +/// [`push_back`]: VecDeque::push_back +/// [`pop_front`]: VecDeque::pop_front +/// [`extend`]: VecDeque::extend +/// [`append`]: VecDeque::append +/// [`make_contiguous`]: VecDeque::make_contiguous +#[cfg_attr(not(test), rustc_diagnostic_item = "vecdeque_type")] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct VecDeque { + // tail and head are pointers into the buffer. Tail always points + // to the first element that could be read, Head always points + // to where data should be written. + // If tail == head the buffer is empty. The length of the ringbuffer + // is defined as the distance between the two. + tail: usize, + head: usize, + buf: RawVec, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Clone for VecDeque { + fn clone(&self) -> VecDeque { + self.iter().cloned().collect() + } + + fn clone_from(&mut self, other: &Self) { + self.truncate(other.len()); + + let mut iter = PairSlices::from(self, other); + while let Some((dst, src)) = iter.next() { + dst.clone_from_slice(&src); + } + + if iter.has_remainder() { + for remainder in iter.remainder() { + self.extend(remainder.iter().cloned()); + } + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<#[may_dangle] T> Drop for VecDeque { + fn drop(&mut self) { + /// Runs the destructor for all items in the slice when it gets dropped (normally or + /// during unwinding). + struct Dropper<'a, T>(&'a mut [T]); + + impl<'a, T> Drop for Dropper<'a, T> { + fn drop(&mut self) { + unsafe { + ptr::drop_in_place(self.0); + } + } + } + + let (front, back) = self.as_mut_slices(); + unsafe { + let _back_dropper = Dropper(back); + // use drop for [T] + ptr::drop_in_place(front); + } + // RawVec handles deallocation + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Default for VecDeque { + /// Creates an empty `VecDeque`. + #[inline] + fn default() -> VecDeque { + VecDeque::new() + } +} + +impl VecDeque { + /// Marginally more convenient + #[inline] + fn ptr(&self) -> *mut T { + self.buf.ptr() + } + + /// Marginally more convenient + #[inline] + fn cap(&self) -> usize { + if mem::size_of::() == 0 { + // For zero sized types, we are always at maximum capacity + MAXIMUM_ZST_CAPACITY + } else { + self.buf.capacity() + } + } + + /// Turn ptr into a slice + #[inline] + unsafe fn buffer_as_slice(&self) -> &[T] { + unsafe { slice::from_raw_parts(self.ptr(), self.cap()) } + } + + /// Turn ptr into a mut slice + #[inline] + unsafe fn buffer_as_mut_slice(&mut self) -> &mut [T] { + unsafe { slice::from_raw_parts_mut(self.ptr(), self.cap()) } + } + + /// Moves an element out of the buffer + #[inline] + unsafe fn buffer_read(&mut self, off: usize) -> T { + unsafe { ptr::read(self.ptr().add(off)) } + } + + /// Writes an element into the buffer, moving it. + #[inline] + unsafe fn buffer_write(&mut self, off: usize, value: T) { + unsafe { + ptr::write(self.ptr().add(off), value); + } + } + + /// Returns `true` if the buffer is at full capacity. + #[inline] + fn is_full(&self) -> bool { + self.cap() - self.len() == 1 + } + + /// Returns the index in the underlying buffer for a given logical element + /// index. + #[inline] + fn wrap_index(&self, idx: usize) -> usize { + wrap_index(idx, self.cap()) + } + + /// Returns the index in the underlying buffer for a given logical element + /// index + addend. + #[inline] + fn wrap_add(&self, idx: usize, addend: usize) -> usize { + wrap_index(idx.wrapping_add(addend), self.cap()) + } + + /// Returns the index in the underlying buffer for a given logical element + /// index - subtrahend. + #[inline] + fn wrap_sub(&self, idx: usize, subtrahend: usize) -> usize { + wrap_index(idx.wrapping_sub(subtrahend), self.cap()) + } + + /// Copies a contiguous block of memory len long from src to dst + #[inline] + unsafe fn copy(&self, dst: usize, src: usize, len: usize) { + debug_assert!( + dst + len <= self.cap(), + "cpy dst={} src={} len={} cap={}", + dst, + src, + len, + self.cap() + ); + debug_assert!( + src + len <= self.cap(), + "cpy dst={} src={} len={} cap={}", + dst, + src, + len, + self.cap() + ); + unsafe { + ptr::copy(self.ptr().add(src), self.ptr().add(dst), len); + } + } + + /// Copies a contiguous block of memory len long from src to dst + #[inline] + unsafe fn copy_nonoverlapping(&self, dst: usize, src: usize, len: usize) { + debug_assert!( + dst + len <= self.cap(), + "cno dst={} src={} len={} cap={}", + dst, + src, + len, + self.cap() + ); + debug_assert!( + src + len <= self.cap(), + "cno dst={} src={} len={} cap={}", + dst, + src, + len, + self.cap() + ); + unsafe { + ptr::copy_nonoverlapping(self.ptr().add(src), self.ptr().add(dst), len); + } + } + + /// Copies a potentially wrapping block of memory len long from src to dest. + /// (abs(dst - src) + len) must be no larger than cap() (There must be at + /// most one continuous overlapping region between src and dest). + unsafe fn wrap_copy(&self, dst: usize, src: usize, len: usize) { + #[allow(dead_code)] + fn diff(a: usize, b: usize) -> usize { + if a <= b { b - a } else { a - b } + } + debug_assert!( + cmp::min(diff(dst, src), self.cap() - diff(dst, src)) + len <= self.cap(), + "wrc dst={} src={} len={} cap={}", + dst, + src, + len, + self.cap() + ); + + if src == dst || len == 0 { + return; + } + + let dst_after_src = self.wrap_sub(dst, src) < len; + + let src_pre_wrap_len = self.cap() - src; + let dst_pre_wrap_len = self.cap() - dst; + let src_wraps = src_pre_wrap_len < len; + let dst_wraps = dst_pre_wrap_len < len; + + match (dst_after_src, src_wraps, dst_wraps) { + (_, false, false) => { + // src doesn't wrap, dst doesn't wrap + // + // S . . . + // 1 [_ _ A A B B C C _] + // 2 [_ _ A A A A B B _] + // D . . . + // + unsafe { + self.copy(dst, src, len); + } + } + (false, false, true) => { + // dst before src, src doesn't wrap, dst wraps + // + // S . . . + // 1 [A A B B _ _ _ C C] + // 2 [A A B B _ _ _ A A] + // 3 [B B B B _ _ _ A A] + // . . D . + // + unsafe { + self.copy(dst, src, dst_pre_wrap_len); + self.copy(0, src + dst_pre_wrap_len, len - dst_pre_wrap_len); + } + } + (true, false, true) => { + // src before dst, src doesn't wrap, dst wraps + // + // S . . . + // 1 [C C _ _ _ A A B B] + // 2 [B B _ _ _ A A B B] + // 3 [B B _ _ _ A A A A] + // . . D . + // + unsafe { + self.copy(0, src + dst_pre_wrap_len, len - dst_pre_wrap_len); + self.copy(dst, src, dst_pre_wrap_len); + } + } + (false, true, false) => { + // dst before src, src wraps, dst doesn't wrap + // + // . . S . + // 1 [C C _ _ _ A A B B] + // 2 [C C _ _ _ B B B B] + // 3 [C C _ _ _ B B C C] + // D . . . + // + unsafe { + self.copy(dst, src, src_pre_wrap_len); + self.copy(dst + src_pre_wrap_len, 0, len - src_pre_wrap_len); + } + } + (true, true, false) => { + // src before dst, src wraps, dst doesn't wrap + // + // . . S . + // 1 [A A B B _ _ _ C C] + // 2 [A A A A _ _ _ C C] + // 3 [C C A A _ _ _ C C] + // D . . . + // + unsafe { + self.copy(dst + src_pre_wrap_len, 0, len - src_pre_wrap_len); + self.copy(dst, src, src_pre_wrap_len); + } + } + (false, true, true) => { + // dst before src, src wraps, dst wraps + // + // . . . S . + // 1 [A B C D _ E F G H] + // 2 [A B C D _ E G H H] + // 3 [A B C D _ E G H A] + // 4 [B C C D _ E G H A] + // . . D . . + // + debug_assert!(dst_pre_wrap_len > src_pre_wrap_len); + let delta = dst_pre_wrap_len - src_pre_wrap_len; + unsafe { + self.copy(dst, src, src_pre_wrap_len); + self.copy(dst + src_pre_wrap_len, 0, delta); + self.copy(0, delta, len - dst_pre_wrap_len); + } + } + (true, true, true) => { + // src before dst, src wraps, dst wraps + // + // . . S . . + // 1 [A B C D _ E F G H] + // 2 [A A B D _ E F G H] + // 3 [H A B D _ E F G H] + // 4 [H A B D _ E F F G] + // . . . D . + // + debug_assert!(src_pre_wrap_len > dst_pre_wrap_len); + let delta = src_pre_wrap_len - dst_pre_wrap_len; + unsafe { + self.copy(delta, 0, len - src_pre_wrap_len); + self.copy(0, self.cap() - delta, delta); + self.copy(dst, src, dst_pre_wrap_len); + } + } + } + } + + /// Frobs the head and tail sections around to handle the fact that we + /// just reallocated. Unsafe because it trusts old_capacity. + #[inline] + unsafe fn handle_capacity_increase(&mut self, old_capacity: usize) { + let new_capacity = self.cap(); + + // Move the shortest contiguous section of the ring buffer + // T H + // [o o o o o o o . ] + // T H + // A [o o o o o o o . . . . . . . . . ] + // H T + // [o o . o o o o o ] + // T H + // B [. . . o o o o o o o . . . . . . ] + // H T + // [o o o o o . o o ] + // H T + // C [o o o o o . . . . . . . . . o o ] + + if self.tail <= self.head { + // A + // Nop + } else if self.head < old_capacity - self.tail { + // B + unsafe { + self.copy_nonoverlapping(old_capacity, 0, self.head); + } + self.head += old_capacity; + debug_assert!(self.head > self.tail); + } else { + // C + let new_tail = new_capacity - (old_capacity - self.tail); + unsafe { + self.copy_nonoverlapping(new_tail, self.tail, old_capacity - self.tail); + } + self.tail = new_tail; + debug_assert!(self.head < self.tail); + } + debug_assert!(self.head < self.cap()); + debug_assert!(self.tail < self.cap()); + debug_assert!(self.cap().count_ones() == 1); + } +} + +impl VecDeque { + /// Creates an empty `VecDeque`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let vector: VecDeque = VecDeque::new(); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn new() -> VecDeque { + VecDeque::with_capacity(INITIAL_CAPACITY) + } + + /// Creates an empty `VecDeque` with space for at least `capacity` elements. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let vector: VecDeque = VecDeque::with_capacity(10); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn with_capacity(capacity: usize) -> VecDeque { + // +1 since the ringbuffer always leaves one space empty + let cap = cmp::max(capacity + 1, MINIMUM_CAPACITY + 1).next_power_of_two(); + assert!(cap > capacity, "capacity overflow"); + + VecDeque { tail: 0, head: 0, buf: RawVec::with_capacity(cap) } + } + + /// Provides a reference to the element at the given index. + /// + /// Element at index 0 is the front of the queue. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(3); + /// buf.push_back(4); + /// buf.push_back(5); + /// assert_eq!(buf.get(1), Some(&4)); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn get(&self, index: usize) -> Option<&T> { + if index < self.len() { + let idx = self.wrap_add(self.tail, index); + unsafe { Some(&*self.ptr().add(idx)) } + } else { + None + } + } + + /// Provides a mutable reference to the element at the given index. + /// + /// Element at index 0 is the front of the queue. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(3); + /// buf.push_back(4); + /// buf.push_back(5); + /// if let Some(elem) = buf.get_mut(1) { + /// *elem = 7; + /// } + /// + /// assert_eq!(buf[1], 7); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn get_mut(&mut self, index: usize) -> Option<&mut T> { + if index < self.len() { + let idx = self.wrap_add(self.tail, index); + unsafe { Some(&mut *self.ptr().add(idx)) } + } else { + None + } + } + + /// Swaps elements at indices `i` and `j`. + /// + /// `i` and `j` may be equal. + /// + /// Element at index 0 is the front of the queue. + /// + /// # Panics + /// + /// Panics if either index is out of bounds. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(3); + /// buf.push_back(4); + /// buf.push_back(5); + /// assert_eq!(buf, [3, 4, 5]); + /// buf.swap(0, 2); + /// assert_eq!(buf, [5, 4, 3]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn swap(&mut self, i: usize, j: usize) { + assert!(i < self.len()); + assert!(j < self.len()); + let ri = self.wrap_add(self.tail, i); + let rj = self.wrap_add(self.tail, j); + unsafe { ptr::swap(self.ptr().add(ri), self.ptr().add(rj)) } + } + + /// Returns the number of elements the `VecDeque` can hold without + /// reallocating. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let buf: VecDeque = VecDeque::with_capacity(10); + /// assert!(buf.capacity() >= 10); + /// ``` + #[inline] + #[stable(feature = "rust1", since = "1.0.0")] + pub fn capacity(&self) -> usize { + self.cap() - 1 + } + + /// Reserves the minimum capacity for exactly `additional` more elements to be inserted in the + /// given `VecDeque`. Does nothing if the capacity is already sufficient. + /// + /// Note that the allocator may give the collection more space than it requests. Therefore + /// capacity can not be relied upon to be precisely minimal. Prefer [`reserve`] if future + /// insertions are expected. + /// + /// # Panics + /// + /// Panics if the new capacity overflows `usize`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf: VecDeque = vec![1].into_iter().collect(); + /// buf.reserve_exact(10); + /// assert!(buf.capacity() >= 11); + /// ``` + /// + /// [`reserve`]: VecDeque::reserve + #[stable(feature = "rust1", since = "1.0.0")] + pub fn reserve_exact(&mut self, additional: usize) { + self.reserve(additional); + } + + /// Reserves capacity for at least `additional` more elements to be inserted in the given + /// `VecDeque`. The collection may reserve more space to avoid frequent reallocations. + /// + /// # Panics + /// + /// Panics if the new capacity overflows `usize`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf: VecDeque = vec![1].into_iter().collect(); + /// buf.reserve(10); + /// assert!(buf.capacity() >= 11); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn reserve(&mut self, additional: usize) { + let old_cap = self.cap(); + let used_cap = self.len() + 1; + let new_cap = used_cap + .checked_add(additional) + .and_then(|needed_cap| needed_cap.checked_next_power_of_two()) + .expect("capacity overflow"); + + if new_cap > old_cap { + self.buf.reserve_exact(used_cap, new_cap - used_cap); + unsafe { + self.handle_capacity_increase(old_cap); + } + } + } + + /// Tries to reserve the minimum capacity for exactly `additional` more elements to + /// be inserted in the given `VecDeque`. After calling `try_reserve_exact`, + /// capacity will be greater than or equal to `self.len() + additional`. + /// Does nothing if the capacity is already sufficient. + /// + /// Note that the allocator may give the collection more space than it + /// requests. Therefore, capacity can not be relied upon to be precisely + /// minimal. Prefer `reserve` if future insertions are expected. + /// + /// # Errors + /// + /// If the capacity overflows `usize`, or the allocator reports a failure, then an error + /// is returned. + /// + /// # Examples + /// + /// ``` + /// #![feature(try_reserve)] + /// use std::collections::TryReserveError; + /// use std::collections::VecDeque; + /// + /// fn process_data(data: &[u32]) -> Result, TryReserveError> { + /// let mut output = VecDeque::new(); + /// + /// // Pre-reserve the memory, exiting if we can't + /// output.try_reserve_exact(data.len())?; + /// + /// // Now we know this can't OOM(Out-Of-Memory) in the middle of our complex work + /// output.extend(data.iter().map(|&val| { + /// val * 2 + 5 // very complicated + /// })); + /// + /// Ok(output) + /// } + /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); + /// ``` + #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] + pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { + self.try_reserve(additional) + } + + /// Tries to reserve capacity for at least `additional` more elements to be inserted + /// in the given `VecDeque`. The collection may reserve more space to avoid + /// frequent reallocations. After calling `try_reserve`, capacity will be + /// greater than or equal to `self.len() + additional`. Does nothing if + /// capacity is already sufficient. + /// + /// # Errors + /// + /// If the capacity overflows `usize`, or the allocator reports a failure, then an error + /// is returned. + /// + /// # Examples + /// + /// ``` + /// #![feature(try_reserve)] + /// use std::collections::TryReserveError; + /// use std::collections::VecDeque; + /// + /// fn process_data(data: &[u32]) -> Result, TryReserveError> { + /// let mut output = VecDeque::new(); + /// + /// // Pre-reserve the memory, exiting if we can't + /// output.try_reserve(data.len())?; + /// + /// // Now we know this can't OOM in the middle of our complex work + /// output.extend(data.iter().map(|&val| { + /// val * 2 + 5 // very complicated + /// })); + /// + /// Ok(output) + /// } + /// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); + /// ``` + #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] + pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { + let old_cap = self.cap(); + let used_cap = self.len() + 1; + let new_cap = used_cap + .checked_add(additional) + .and_then(|needed_cap| needed_cap.checked_next_power_of_two()) + .ok_or(TryReserveError::CapacityOverflow)?; + + if new_cap > old_cap { + self.buf.try_reserve_exact(used_cap, new_cap - used_cap)?; + unsafe { + self.handle_capacity_increase(old_cap); + } + } + Ok(()) + } + + /// Shrinks the capacity of the `VecDeque` as much as possible. + /// + /// It will drop down as close as possible to the length but the allocator may still inform the + /// `VecDeque` that there is space for a few more elements. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::with_capacity(15); + /// buf.extend(0..4); + /// assert_eq!(buf.capacity(), 15); + /// buf.shrink_to_fit(); + /// assert!(buf.capacity() >= 4); + /// ``` + #[stable(feature = "deque_extras_15", since = "1.5.0")] + pub fn shrink_to_fit(&mut self) { + self.shrink_to(0); + } + + /// Shrinks the capacity of the `VecDeque` with a lower bound. + /// + /// The capacity will remain at least as large as both the length + /// and the supplied value. + /// + /// Panics if the current capacity is smaller than the supplied + /// minimum capacity. + /// + /// # Examples + /// + /// ``` + /// #![feature(shrink_to)] + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::with_capacity(15); + /// buf.extend(0..4); + /// assert_eq!(buf.capacity(), 15); + /// buf.shrink_to(6); + /// assert!(buf.capacity() >= 6); + /// buf.shrink_to(0); + /// assert!(buf.capacity() >= 4); + /// ``` + #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")] + pub fn shrink_to(&mut self, min_capacity: usize) { + assert!(self.capacity() >= min_capacity, "Tried to shrink to a larger capacity"); + + // +1 since the ringbuffer always leaves one space empty + // len + 1 can't overflow for an existing, well-formed ringbuffer. + let target_cap = cmp::max(cmp::max(min_capacity, self.len()) + 1, MINIMUM_CAPACITY + 1) + .next_power_of_two(); + + if target_cap < self.cap() { + // There are three cases of interest: + // All elements are out of desired bounds + // Elements are contiguous, and head is out of desired bounds + // Elements are discontiguous, and tail is out of desired bounds + // + // At all other times, element positions are unaffected. + // + // Indicates that elements at the head should be moved. + let head_outside = self.head == 0 || self.head >= target_cap; + // Move elements from out of desired bounds (positions after target_cap) + if self.tail >= target_cap && head_outside { + // T H + // [. . . . . . . . o o o o o o o . ] + // T H + // [o o o o o o o . ] + unsafe { + self.copy_nonoverlapping(0, self.tail, self.len()); + } + self.head = self.len(); + self.tail = 0; + } else if self.tail != 0 && self.tail < target_cap && head_outside { + // T H + // [. . . o o o o o o o . . . . . . ] + // H T + // [o o . o o o o o ] + let len = self.wrap_sub(self.head, target_cap); + unsafe { + self.copy_nonoverlapping(0, target_cap, len); + } + self.head = len; + debug_assert!(self.head < self.tail); + } else if self.tail >= target_cap { + // H T + // [o o o o o . . . . . . . . . o o ] + // H T + // [o o o o o . o o ] + debug_assert!(self.wrap_sub(self.head, 1) < target_cap); + let len = self.cap() - self.tail; + let new_tail = target_cap - len; + unsafe { + self.copy_nonoverlapping(new_tail, self.tail, len); + } + self.tail = new_tail; + debug_assert!(self.head < self.tail); + } + + self.buf.shrink_to_fit(target_cap); + + debug_assert!(self.head < self.cap()); + debug_assert!(self.tail < self.cap()); + debug_assert!(self.cap().count_ones() == 1); + } + } + + /// Shortens the `VecDeque`, keeping the first `len` elements and dropping + /// the rest. + /// + /// If `len` is greater than the `VecDeque`'s current length, this has no + /// effect. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(5); + /// buf.push_back(10); + /// buf.push_back(15); + /// assert_eq!(buf, [5, 10, 15]); + /// buf.truncate(1); + /// assert_eq!(buf, [5]); + /// ``` + #[stable(feature = "deque_extras", since = "1.16.0")] + pub fn truncate(&mut self, len: usize) { + /// Runs the destructor for all items in the slice when it gets dropped (normally or + /// during unwinding). + struct Dropper<'a, T>(&'a mut [T]); + + impl<'a, T> Drop for Dropper<'a, T> { + fn drop(&mut self) { + unsafe { + ptr::drop_in_place(self.0); + } + } + } + + // Safe because: + // + // * Any slice passed to `drop_in_place` is valid; the second case has + // `len <= front.len()` and returning on `len > self.len()` ensures + // `begin <= back.len()` in the first case + // * The head of the VecDeque is moved before calling `drop_in_place`, + // so no value is dropped twice if `drop_in_place` panics + unsafe { + if len > self.len() { + return; + } + let num_dropped = self.len() - len; + let (front, back) = self.as_mut_slices(); + if len > front.len() { + let begin = len - front.len(); + let drop_back = back.get_unchecked_mut(begin..) as *mut _; + self.head = self.wrap_sub(self.head, num_dropped); + ptr::drop_in_place(drop_back); + } else { + let drop_back = back as *mut _; + let drop_front = front.get_unchecked_mut(len..) as *mut _; + self.head = self.wrap_sub(self.head, num_dropped); + + // Make sure the second half is dropped even when a destructor + // in the first one panics. + let _back_dropper = Dropper(&mut *drop_back); + ptr::drop_in_place(drop_front); + } + } + } + + /// Returns a front-to-back iterator. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(5); + /// buf.push_back(3); + /// buf.push_back(4); + /// let b: &[_] = &[&5, &3, &4]; + /// let c: Vec<&i32> = buf.iter().collect(); + /// assert_eq!(&c[..], b); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn iter(&self) -> Iter<'_, T> { + Iter { tail: self.tail, head: self.head, ring: unsafe { self.buffer_as_slice() } } + } + + /// Returns a front-to-back iterator that returns mutable references. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(5); + /// buf.push_back(3); + /// buf.push_back(4); + /// for num in buf.iter_mut() { + /// *num = *num - 2; + /// } + /// let b: &[_] = &[&mut 3, &mut 1, &mut 2]; + /// assert_eq!(&buf.iter_mut().collect::>()[..], b); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn iter_mut(&mut self) -> IterMut<'_, T> { + // SAFETY: The internal `IterMut` safety invariant is established because the + // `ring` we create is a dereferencable slice for lifetime '_. + IterMut { + tail: self.tail, + head: self.head, + ring: ptr::slice_from_raw_parts_mut(self.ptr(), self.cap()), + phantom: PhantomData, + } + } + + /// Returns a pair of slices which contain, in order, the contents of the + /// `VecDeque`. + /// + /// If [`make_contiguous`] was previously called, all elements of the + /// `VecDeque` will be in the first slice and the second slice will be empty. + /// + /// [`make_contiguous`]: VecDeque::make_contiguous + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut vector = VecDeque::new(); + /// + /// vector.push_back(0); + /// vector.push_back(1); + /// vector.push_back(2); + /// + /// assert_eq!(vector.as_slices(), (&[0, 1, 2][..], &[][..])); + /// + /// vector.push_front(10); + /// vector.push_front(9); + /// + /// assert_eq!(vector.as_slices(), (&[9, 10][..], &[0, 1, 2][..])); + /// ``` + #[inline] + #[stable(feature = "deque_extras_15", since = "1.5.0")] + pub fn as_slices(&self) -> (&[T], &[T]) { + unsafe { + let buf = self.buffer_as_slice(); + RingSlices::ring_slices(buf, self.head, self.tail) + } + } + + /// Returns a pair of slices which contain, in order, the contents of the + /// `VecDeque`. + /// + /// If [`make_contiguous`] was previously called, all elements of the + /// `VecDeque` will be in the first slice and the second slice will be empty. + /// + /// [`make_contiguous`]: VecDeque::make_contiguous + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut vector = VecDeque::new(); + /// + /// vector.push_back(0); + /// vector.push_back(1); + /// + /// vector.push_front(10); + /// vector.push_front(9); + /// + /// vector.as_mut_slices().0[0] = 42; + /// vector.as_mut_slices().1[0] = 24; + /// assert_eq!(vector.as_slices(), (&[42, 10][..], &[24, 1][..])); + /// ``` + #[inline] + #[stable(feature = "deque_extras_15", since = "1.5.0")] + pub fn as_mut_slices(&mut self) -> (&mut [T], &mut [T]) { + unsafe { + let head = self.head; + let tail = self.tail; + let buf = self.buffer_as_mut_slice(); + RingSlices::ring_slices(buf, head, tail) + } + } + + /// Returns the number of elements in the `VecDeque`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut v = VecDeque::new(); + /// assert_eq!(v.len(), 0); + /// v.push_back(1); + /// assert_eq!(v.len(), 1); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn len(&self) -> usize { + count(self.tail, self.head, self.cap()) + } + + /// Returns `true` if the `VecDeque` is empty. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut v = VecDeque::new(); + /// assert!(v.is_empty()); + /// v.push_front(1); + /// assert!(!v.is_empty()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn is_empty(&self) -> bool { + self.tail == self.head + } + + fn range_tail_head(&self, range: R) -> (usize, usize) + where + R: RangeBounds, + { + let Range { start, end } = range.assert_len(self.len()); + let tail = self.wrap_add(self.tail, start); + let head = self.wrap_add(self.tail, end); + (tail, head) + } + + /// Creates an iterator that covers the specified range in the `VecDeque`. + /// + /// # Panics + /// + /// Panics if the starting point is greater than the end point or if + /// the end point is greater than the length of the vector. + /// + /// # Examples + /// + /// ``` + /// #![feature(deque_range)] + /// + /// use std::collections::VecDeque; + /// + /// let v: VecDeque<_> = vec![1, 2, 3].into_iter().collect(); + /// let range = v.range(2..).copied().collect::>(); + /// assert_eq!(range, [3]); + /// + /// // A full range covers all contents + /// let all = v.range(..); + /// assert_eq!(all.len(), 3); + /// ``` + #[inline] + #[unstable(feature = "deque_range", issue = "74217")] + pub fn range(&self, range: R) -> Iter<'_, T> + where + R: RangeBounds, + { + let (tail, head) = self.range_tail_head(range); + Iter { + tail, + head, + // The shared reference we have in &self is maintained in the '_ of Iter. + ring: unsafe { self.buffer_as_slice() }, + } + } + + /// Creates an iterator that covers the specified mutable range in the `VecDeque`. + /// + /// # Panics + /// + /// Panics if the starting point is greater than the end point or if + /// the end point is greater than the length of the vector. + /// + /// # Examples + /// + /// ``` + /// #![feature(deque_range)] + /// + /// use std::collections::VecDeque; + /// + /// let mut v: VecDeque<_> = vec![1, 2, 3].into_iter().collect(); + /// for v in v.range_mut(2..) { + /// *v *= 2; + /// } + /// assert_eq!(v, vec![1, 2, 6]); + /// + /// // A full range covers all contents + /// for v in v.range_mut(..) { + /// *v *= 2; + /// } + /// assert_eq!(v, vec![2, 4, 12]); + /// ``` + #[inline] + #[unstable(feature = "deque_range", issue = "74217")] + pub fn range_mut(&mut self, range: R) -> IterMut<'_, T> + where + R: RangeBounds, + { + let (tail, head) = self.range_tail_head(range); + + // SAFETY: The internal `IterMut` safety invariant is established because the + // `ring` we create is a dereferencable slice for lifetime '_. + IterMut { + tail, + head, + ring: ptr::slice_from_raw_parts_mut(self.ptr(), self.cap()), + phantom: PhantomData, + } + } + + /// Creates a draining iterator that removes the specified range in the + /// `VecDeque` and yields the removed items. + /// + /// Note 1: The element range is removed even if the iterator is not + /// consumed until the end. + /// + /// Note 2: It is unspecified how many elements are removed from the deque, + /// if the `Drain` value is not dropped, but the borrow it holds expires + /// (e.g., due to `mem::forget`). + /// + /// # Panics + /// + /// Panics if the starting point is greater than the end point or if + /// the end point is greater than the length of the vector. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut v: VecDeque<_> = vec![1, 2, 3].into_iter().collect(); + /// let drained = v.drain(2..).collect::>(); + /// assert_eq!(drained, [3]); + /// assert_eq!(v, [1, 2]); + /// + /// // A full range clears all contents + /// v.drain(..); + /// assert!(v.is_empty()); + /// ``` + #[inline] + #[stable(feature = "drain", since = "1.6.0")] + pub fn drain(&mut self, range: R) -> Drain<'_, T> + where + R: RangeBounds, + { + // Memory safety + // + // When the Drain is first created, the source deque is shortened to + // make sure no uninitialized or moved-from elements are accessible at + // all if the Drain's destructor never gets to run. + // + // Drain will ptr::read out the values to remove. + // When finished, the remaining data will be copied back to cover the hole, + // and the head/tail values will be restored correctly. + // + let (drain_tail, drain_head) = self.range_tail_head(range); + + // The deque's elements are parted into three segments: + // * self.tail -> drain_tail + // * drain_tail -> drain_head + // * drain_head -> self.head + // + // T = self.tail; H = self.head; t = drain_tail; h = drain_head + // + // We store drain_tail as self.head, and drain_head and self.head as + // after_tail and after_head respectively on the Drain. This also + // truncates the effective array such that if the Drain is leaked, we + // have forgotten about the potentially moved values after the start of + // the drain. + // + // T t h H + // [. . . o o x x o o . . .] + // + let head = self.head; + + // "forget" about the values after the start of the drain until after + // the drain is complete and the Drain destructor is run. + self.head = drain_tail; + + Drain { + deque: NonNull::from(&mut *self), + after_tail: drain_head, + after_head: head, + iter: Iter { + tail: drain_tail, + head: drain_head, + // Crucially, we only create shared references from `self` here and read from + // it. We do not write to `self` nor reborrow to a mutable reference. + // Hence the raw pointer we created above, for `deque`, remains valid. + ring: unsafe { self.buffer_as_slice() }, + }, + } + } + + /// Clears the `VecDeque`, removing all values. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut v = VecDeque::new(); + /// v.push_back(1); + /// v.clear(); + /// assert!(v.is_empty()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn clear(&mut self) { + self.truncate(0); + } + + /// Returns `true` if the `VecDeque` contains an element equal to the + /// given value. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut vector: VecDeque = VecDeque::new(); + /// + /// vector.push_back(0); + /// vector.push_back(1); + /// + /// assert_eq!(vector.contains(&1), true); + /// assert_eq!(vector.contains(&10), false); + /// ``` + #[stable(feature = "vec_deque_contains", since = "1.12.0")] + pub fn contains(&self, x: &T) -> bool + where + T: PartialEq, + { + let (a, b) = self.as_slices(); + a.contains(x) || b.contains(x) + } + + /// Provides a reference to the front element, or `None` if the `VecDeque` is + /// empty. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut d = VecDeque::new(); + /// assert_eq!(d.front(), None); + /// + /// d.push_back(1); + /// d.push_back(2); + /// assert_eq!(d.front(), Some(&1)); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn front(&self) -> Option<&T> { + if !self.is_empty() { Some(&self[0]) } else { None } + } + + /// Provides a mutable reference to the front element, or `None` if the + /// `VecDeque` is empty. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut d = VecDeque::new(); + /// assert_eq!(d.front_mut(), None); + /// + /// d.push_back(1); + /// d.push_back(2); + /// match d.front_mut() { + /// Some(x) => *x = 9, + /// None => (), + /// } + /// assert_eq!(d.front(), Some(&9)); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn front_mut(&mut self) -> Option<&mut T> { + if !self.is_empty() { Some(&mut self[0]) } else { None } + } + + /// Provides a reference to the back element, or `None` if the `VecDeque` is + /// empty. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut d = VecDeque::new(); + /// assert_eq!(d.back(), None); + /// + /// d.push_back(1); + /// d.push_back(2); + /// assert_eq!(d.back(), Some(&2)); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn back(&self) -> Option<&T> { + if !self.is_empty() { Some(&self[self.len() - 1]) } else { None } + } + + /// Provides a mutable reference to the back element, or `None` if the + /// `VecDeque` is empty. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut d = VecDeque::new(); + /// assert_eq!(d.back(), None); + /// + /// d.push_back(1); + /// d.push_back(2); + /// match d.back_mut() { + /// Some(x) => *x = 9, + /// None => (), + /// } + /// assert_eq!(d.back(), Some(&9)); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn back_mut(&mut self) -> Option<&mut T> { + let len = self.len(); + if !self.is_empty() { Some(&mut self[len - 1]) } else { None } + } + + /// Removes the first element and returns it, or `None` if the `VecDeque` is + /// empty. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut d = VecDeque::new(); + /// d.push_back(1); + /// d.push_back(2); + /// + /// assert_eq!(d.pop_front(), Some(1)); + /// assert_eq!(d.pop_front(), Some(2)); + /// assert_eq!(d.pop_front(), None); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn pop_front(&mut self) -> Option { + if self.is_empty() { + None + } else { + let tail = self.tail; + self.tail = self.wrap_add(self.tail, 1); + unsafe { Some(self.buffer_read(tail)) } + } + } + + /// Removes the last element from the `VecDeque` and returns it, or `None` if + /// it is empty. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// assert_eq!(buf.pop_back(), None); + /// buf.push_back(1); + /// buf.push_back(3); + /// assert_eq!(buf.pop_back(), Some(3)); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn pop_back(&mut self) -> Option { + if self.is_empty() { + None + } else { + self.head = self.wrap_sub(self.head, 1); + let head = self.head; + unsafe { Some(self.buffer_read(head)) } + } + } + + /// Prepends an element to the `VecDeque`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut d = VecDeque::new(); + /// d.push_front(1); + /// d.push_front(2); + /// assert_eq!(d.front(), Some(&2)); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn push_front(&mut self, value: T) { + if self.is_full() { + self.grow(); + } + + self.tail = self.wrap_sub(self.tail, 1); + let tail = self.tail; + unsafe { + self.buffer_write(tail, value); + } + } + + /// Appends an element to the back of the `VecDeque`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(1); + /// buf.push_back(3); + /// assert_eq!(3, *buf.back().unwrap()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn push_back(&mut self, value: T) { + if self.is_full() { + self.grow(); + } + + let head = self.head; + self.head = self.wrap_add(self.head, 1); + unsafe { self.buffer_write(head, value) } + } + + #[inline] + fn is_contiguous(&self) -> bool { + self.tail <= self.head + } + + /// Removes an element from anywhere in the `VecDeque` and returns it, + /// replacing it with the first element. + /// + /// This does not preserve ordering, but is *O*(1). + /// + /// Returns `None` if `index` is out of bounds. + /// + /// Element at index 0 is the front of the queue. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// assert_eq!(buf.swap_remove_front(0), None); + /// buf.push_back(1); + /// buf.push_back(2); + /// buf.push_back(3); + /// assert_eq!(buf, [1, 2, 3]); + /// + /// assert_eq!(buf.swap_remove_front(2), Some(3)); + /// assert_eq!(buf, [2, 1]); + /// ``` + #[stable(feature = "deque_extras_15", since = "1.5.0")] + pub fn swap_remove_front(&mut self, index: usize) -> Option { + let length = self.len(); + if length > 0 && index < length && index != 0 { + self.swap(index, 0); + } else if index >= length { + return None; + } + self.pop_front() + } + + /// Removes an element from anywhere in the `VecDeque` and returns it, replacing it with the + /// last element. + /// + /// This does not preserve ordering, but is *O*(1). + /// + /// Returns `None` if `index` is out of bounds. + /// + /// Element at index 0 is the front of the queue. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// assert_eq!(buf.swap_remove_back(0), None); + /// buf.push_back(1); + /// buf.push_back(2); + /// buf.push_back(3); + /// assert_eq!(buf, [1, 2, 3]); + /// + /// assert_eq!(buf.swap_remove_back(0), Some(1)); + /// assert_eq!(buf, [3, 2]); + /// ``` + #[stable(feature = "deque_extras_15", since = "1.5.0")] + pub fn swap_remove_back(&mut self, index: usize) -> Option { + let length = self.len(); + if length > 0 && index < length - 1 { + self.swap(index, length - 1); + } else if index >= length { + return None; + } + self.pop_back() + } + + /// Inserts an element at `index` within the `VecDeque`, shifting all elements with indices + /// greater than or equal to `index` towards the back. + /// + /// Element at index 0 is the front of the queue. + /// + /// # Panics + /// + /// Panics if `index` is greater than `VecDeque`'s length + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut vec_deque = VecDeque::new(); + /// vec_deque.push_back('a'); + /// vec_deque.push_back('b'); + /// vec_deque.push_back('c'); + /// assert_eq!(vec_deque, &['a', 'b', 'c']); + /// + /// vec_deque.insert(1, 'd'); + /// assert_eq!(vec_deque, &['a', 'd', 'b', 'c']); + /// ``` + #[stable(feature = "deque_extras_15", since = "1.5.0")] + pub fn insert(&mut self, index: usize, value: T) { + assert!(index <= self.len(), "index out of bounds"); + if self.is_full() { + self.grow(); + } + + // Move the least number of elements in the ring buffer and insert + // the given object + // + // At most len/2 - 1 elements will be moved. O(min(n, n-i)) + // + // There are three main cases: + // Elements are contiguous + // - special case when tail is 0 + // Elements are discontiguous and the insert is in the tail section + // Elements are discontiguous and the insert is in the head section + // + // For each of those there are two more cases: + // Insert is closer to tail + // Insert is closer to head + // + // Key: H - self.head + // T - self.tail + // o - Valid element + // I - Insertion element + // A - The element that should be after the insertion point + // M - Indicates element was moved + + let idx = self.wrap_add(self.tail, index); + + let distance_to_tail = index; + let distance_to_head = self.len() - index; + + let contiguous = self.is_contiguous(); + + match (contiguous, distance_to_tail <= distance_to_head, idx >= self.tail) { + (true, true, _) if index == 0 => { + // push_front + // + // T + // I H + // [A o o o o o o . . . . . . . . .] + // + // H T + // [A o o o o o o o . . . . . I] + // + + self.tail = self.wrap_sub(self.tail, 1); + } + (true, true, _) => { + unsafe { + // contiguous, insert closer to tail: + // + // T I H + // [. . . o o A o o o o . . . . . .] + // + // T H + // [. . o o I A o o o o . . . . . .] + // M M + // + // contiguous, insert closer to tail and tail is 0: + // + // + // T I H + // [o o A o o o o . . . . . . . . .] + // + // H T + // [o I A o o o o o . . . . . . . o] + // M M + + let new_tail = self.wrap_sub(self.tail, 1); + + self.copy(new_tail, self.tail, 1); + // Already moved the tail, so we only copy `index - 1` elements. + self.copy(self.tail, self.tail + 1, index - 1); + + self.tail = new_tail; + } + } + (true, false, _) => { + unsafe { + // contiguous, insert closer to head: + // + // T I H + // [. . . o o o o A o o . . . . . .] + // + // T H + // [. . . o o o o I A o o . . . . .] + // M M M + + self.copy(idx + 1, idx, self.head - idx); + self.head = self.wrap_add(self.head, 1); + } + } + (false, true, true) => { + unsafe { + // discontiguous, insert closer to tail, tail section: + // + // H T I + // [o o o o o o . . . . . o o A o o] + // + // H T + // [o o o o o o . . . . o o I A o o] + // M M + + self.copy(self.tail - 1, self.tail, index); + self.tail -= 1; + } + } + (false, false, true) => { + unsafe { + // discontiguous, insert closer to head, tail section: + // + // H T I + // [o o . . . . . . . o o o o o A o] + // + // H T + // [o o o . . . . . . o o o o o I A] + // M M M M + + // copy elements up to new head + self.copy(1, 0, self.head); + + // copy last element into empty spot at bottom of buffer + self.copy(0, self.cap() - 1, 1); + + // move elements from idx to end forward not including ^ element + self.copy(idx + 1, idx, self.cap() - 1 - idx); + + self.head += 1; + } + } + (false, true, false) if idx == 0 => { + unsafe { + // discontiguous, insert is closer to tail, head section, + // and is at index zero in the internal buffer: + // + // I H T + // [A o o o o o o o o o . . . o o o] + // + // H T + // [A o o o o o o o o o . . o o o I] + // M M M + + // copy elements up to new tail + self.copy(self.tail - 1, self.tail, self.cap() - self.tail); + + // copy last element into empty spot at bottom of buffer + self.copy(self.cap() - 1, 0, 1); + + self.tail -= 1; + } + } + (false, true, false) => { + unsafe { + // discontiguous, insert closer to tail, head section: + // + // I H T + // [o o o A o o o o o o . . . o o o] + // + // H T + // [o o I A o o o o o o . . o o o o] + // M M M M M M + + // copy elements up to new tail + self.copy(self.tail - 1, self.tail, self.cap() - self.tail); + + // copy last element into empty spot at bottom of buffer + self.copy(self.cap() - 1, 0, 1); + + // move elements from idx-1 to end forward not including ^ element + self.copy(0, 1, idx - 1); + + self.tail -= 1; + } + } + (false, false, false) => { + unsafe { + // discontiguous, insert closer to head, head section: + // + // I H T + // [o o o o A o o . . . . . . o o o] + // + // H T + // [o o o o I A o o . . . . . o o o] + // M M M + + self.copy(idx + 1, idx, self.head - idx); + self.head += 1; + } + } + } + + // tail might've been changed so we need to recalculate + let new_idx = self.wrap_add(self.tail, index); + unsafe { + self.buffer_write(new_idx, value); + } + } + + /// Removes and returns the element at `index` from the `VecDeque`. + /// Whichever end is closer to the removal point will be moved to make + /// room, and all the affected elements will be moved to new positions. + /// Returns `None` if `index` is out of bounds. + /// + /// Element at index 0 is the front of the queue. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(1); + /// buf.push_back(2); + /// buf.push_back(3); + /// assert_eq!(buf, [1, 2, 3]); + /// + /// assert_eq!(buf.remove(1), Some(2)); + /// assert_eq!(buf, [1, 3]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn remove(&mut self, index: usize) -> Option { + if self.is_empty() || self.len() <= index { + return None; + } + + // There are three main cases: + // Elements are contiguous + // Elements are discontiguous and the removal is in the tail section + // Elements are discontiguous and the removal is in the head section + // - special case when elements are technically contiguous, + // but self.head = 0 + // + // For each of those there are two more cases: + // Insert is closer to tail + // Insert is closer to head + // + // Key: H - self.head + // T - self.tail + // o - Valid element + // x - Element marked for removal + // R - Indicates element that is being removed + // M - Indicates element was moved + + let idx = self.wrap_add(self.tail, index); + + let elem = unsafe { Some(self.buffer_read(idx)) }; + + let distance_to_tail = index; + let distance_to_head = self.len() - index; + + let contiguous = self.is_contiguous(); + + match (contiguous, distance_to_tail <= distance_to_head, idx >= self.tail) { + (true, true, _) => { + unsafe { + // contiguous, remove closer to tail: + // + // T R H + // [. . . o o x o o o o . . . . . .] + // + // T H + // [. . . . o o o o o o . . . . . .] + // M M + + self.copy(self.tail + 1, self.tail, index); + self.tail += 1; + } + } + (true, false, _) => { + unsafe { + // contiguous, remove closer to head: + // + // T R H + // [. . . o o o o x o o . . . . . .] + // + // T H + // [. . . o o o o o o . . . . . . .] + // M M + + self.copy(idx, idx + 1, self.head - idx - 1); + self.head -= 1; + } + } + (false, true, true) => { + unsafe { + // discontiguous, remove closer to tail, tail section: + // + // H T R + // [o o o o o o . . . . . o o x o o] + // + // H T + // [o o o o o o . . . . . . o o o o] + // M M + + self.copy(self.tail + 1, self.tail, index); + self.tail = self.wrap_add(self.tail, 1); + } + } + (false, false, false) => { + unsafe { + // discontiguous, remove closer to head, head section: + // + // R H T + // [o o o o x o o . . . . . . o o o] + // + // H T + // [o o o o o o . . . . . . . o o o] + // M M + + self.copy(idx, idx + 1, self.head - idx - 1); + self.head -= 1; + } + } + (false, false, true) => { + unsafe { + // discontiguous, remove closer to head, tail section: + // + // H T R + // [o o o . . . . . . o o o o o x o] + // + // H T + // [o o . . . . . . . o o o o o o o] + // M M M M + // + // or quasi-discontiguous, remove next to head, tail section: + // + // H T R + // [. . . . . . . . . o o o o o x o] + // + // T H + // [. . . . . . . . . o o o o o o .] + // M + + // draw in elements in the tail section + self.copy(idx, idx + 1, self.cap() - idx - 1); + + // Prevents underflow. + if self.head != 0 { + // copy first element into empty spot + self.copy(self.cap() - 1, 0, 1); + + // move elements in the head section backwards + self.copy(0, 1, self.head - 1); + } + + self.head = self.wrap_sub(self.head, 1); + } + } + (false, true, false) => { + unsafe { + // discontiguous, remove closer to tail, head section: + // + // R H T + // [o o x o o o o o o o . . . o o o] + // + // H T + // [o o o o o o o o o o . . . . o o] + // M M M M M + + // draw in elements up to idx + self.copy(1, 0, idx); + + // copy last element into empty spot + self.copy(0, self.cap() - 1, 1); + + // move elements from tail to end forward, excluding the last one + self.copy(self.tail + 1, self.tail, self.cap() - self.tail - 1); + + self.tail = self.wrap_add(self.tail, 1); + } + } + } + + elem + } + + /// Splits the `VecDeque` into two at the given index. + /// + /// Returns a newly allocated `VecDeque`. `self` contains elements `[0, at)`, + /// and the returned `VecDeque` contains elements `[at, len)`. + /// + /// Note that the capacity of `self` does not change. + /// + /// Element at index 0 is the front of the queue. + /// + /// # Panics + /// + /// Panics if `at > len`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf: VecDeque<_> = vec![1,2,3].into_iter().collect(); + /// let buf2 = buf.split_off(1); + /// assert_eq!(buf, [1]); + /// assert_eq!(buf2, [2, 3]); + /// ``` + #[inline] + #[must_use = "use `.truncate()` if you don't need the other half"] + #[stable(feature = "split_off", since = "1.4.0")] + pub fn split_off(&mut self, at: usize) -> Self { + let len = self.len(); + assert!(at <= len, "`at` out of bounds"); + + let other_len = len - at; + let mut other = VecDeque::with_capacity(other_len); + + unsafe { + let (first_half, second_half) = self.as_slices(); + + let first_len = first_half.len(); + let second_len = second_half.len(); + if at < first_len { + // `at` lies in the first half. + let amount_in_first = first_len - at; + + ptr::copy_nonoverlapping(first_half.as_ptr().add(at), other.ptr(), amount_in_first); + + // just take all of the second half. + ptr::copy_nonoverlapping( + second_half.as_ptr(), + other.ptr().add(amount_in_first), + second_len, + ); + } else { + // `at` lies in the second half, need to factor in the elements we skipped + // in the first half. + let offset = at - first_len; + let amount_in_second = second_len - offset; + ptr::copy_nonoverlapping( + second_half.as_ptr().add(offset), + other.ptr(), + amount_in_second, + ); + } + } + + // Cleanup where the ends of the buffers are + self.head = self.wrap_sub(self.head, other_len); + other.head = other.wrap_index(other_len); + + other + } + + /// Moves all the elements of `other` into `self`, leaving `other` empty. + /// + /// # Panics + /// + /// Panics if the new number of elements in self overflows a `usize`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf: VecDeque<_> = vec![1, 2].into_iter().collect(); + /// let mut buf2: VecDeque<_> = vec![3, 4].into_iter().collect(); + /// buf.append(&mut buf2); + /// assert_eq!(buf, [1, 2, 3, 4]); + /// assert_eq!(buf2, []); + /// ``` + #[inline] + #[stable(feature = "append", since = "1.4.0")] + pub fn append(&mut self, other: &mut Self) { + // naive impl + self.extend(other.drain(..)); + } + + /// Retains only the elements specified by the predicate. + /// + /// In other words, remove all elements `e` such that `f(&e)` returns false. + /// This method operates in place, visiting each element exactly once in the + /// original order, and preserves the order of the retained elements. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.extend(1..5); + /// buf.retain(|&x| x % 2 == 0); + /// assert_eq!(buf, [2, 4]); + /// ``` + /// + /// The exact order may be useful for tracking external state, like an index. + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.extend(1..6); + /// + /// let keep = [false, true, true, false, true]; + /// let mut i = 0; + /// buf.retain(|_| (keep[i], i += 1).0); + /// assert_eq!(buf, [2, 3, 5]); + /// ``` + #[stable(feature = "vec_deque_retain", since = "1.4.0")] + pub fn retain(&mut self, mut f: F) + where + F: FnMut(&T) -> bool, + { + let len = self.len(); + let mut del = 0; + for i in 0..len { + if !f(&self[i]) { + del += 1; + } else if del > 0 { + self.swap(i - del, i); + } + } + if del > 0 { + self.truncate(len - del); + } + } + + // This may panic or abort + #[inline(never)] + fn grow(&mut self) { + if self.is_full() { + let old_cap = self.cap(); + // Double the buffer size. + self.buf.reserve_exact(old_cap, old_cap); + assert!(self.cap() == old_cap * 2); + unsafe { + self.handle_capacity_increase(old_cap); + } + debug_assert!(!self.is_full()); + } + } + + /// Modifies the `VecDeque` in-place so that `len()` is equal to `new_len`, + /// either by removing excess elements from the back or by appending + /// elements generated by calling `generator` to the back. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(5); + /// buf.push_back(10); + /// buf.push_back(15); + /// assert_eq!(buf, [5, 10, 15]); + /// + /// buf.resize_with(5, Default::default); + /// assert_eq!(buf, [5, 10, 15, 0, 0]); + /// + /// buf.resize_with(2, || unreachable!()); + /// assert_eq!(buf, [5, 10]); + /// + /// let mut state = 100; + /// buf.resize_with(5, || { state += 1; state }); + /// assert_eq!(buf, [5, 10, 101, 102, 103]); + /// ``` + #[stable(feature = "vec_resize_with", since = "1.33.0")] + pub fn resize_with(&mut self, new_len: usize, generator: impl FnMut() -> T) { + let len = self.len(); + + if new_len > len { + self.extend(repeat_with(generator).take(new_len - len)) + } else { + self.truncate(new_len); + } + } + + /// Rearranges the internal storage of this deque so it is one contiguous + /// slice, which is then returned. + /// + /// This method does not allocate and does not change the order of the + /// inserted elements. As it returns a mutable slice, this can be used to + /// sort a deque. + /// + /// Once the internal storage is contiguous, the [`as_slices`] and + /// [`as_mut_slices`] methods will return the entire contents of the + /// `VecDeque` in a single slice. + /// + /// [`as_slices`]: VecDeque::as_slices + /// [`as_mut_slices`]: VecDeque::as_mut_slices + /// + /// # Examples + /// + /// Sorting the content of a deque. + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::with_capacity(15); + /// + /// buf.push_back(2); + /// buf.push_back(1); + /// buf.push_front(3); + /// + /// // sorting the deque + /// buf.make_contiguous().sort(); + /// assert_eq!(buf.as_slices(), (&[1, 2, 3] as &[_], &[] as &[_])); + /// + /// // sorting it in reverse order + /// buf.make_contiguous().sort_by(|a, b| b.cmp(a)); + /// assert_eq!(buf.as_slices(), (&[3, 2, 1] as &[_], &[] as &[_])); + /// ``` + /// + /// Getting immutable access to the contiguous slice. + /// + /// ```rust + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// + /// buf.push_back(2); + /// buf.push_back(1); + /// buf.push_front(3); + /// + /// buf.make_contiguous(); + /// if let (slice, &[]) = buf.as_slices() { + /// // we can now be sure that `slice` contains all elements of the deque, + /// // while still having immutable access to `buf`. + /// assert_eq!(buf.len(), slice.len()); + /// assert_eq!(slice, &[3, 2, 1] as &[_]); + /// } + /// ``` + #[stable(feature = "deque_make_contiguous", since = "1.48.0")] + pub fn make_contiguous(&mut self) -> &mut [T] { + if self.is_contiguous() { + let tail = self.tail; + let head = self.head; + return unsafe { &mut self.buffer_as_mut_slice()[tail..head] }; + } + + let buf = self.buf.ptr(); + let cap = self.cap(); + let len = self.len(); + + let free = self.tail - self.head; + let tail_len = cap - self.tail; + + if free >= tail_len { + // there is enough free space to copy the tail in one go, + // this means that we first shift the head backwards, and then + // copy the tail to the correct position. + // + // from: DEFGH....ABC + // to: ABCDEFGH.... + unsafe { + ptr::copy(buf, buf.add(tail_len), self.head); + // ...DEFGH.ABC + ptr::copy_nonoverlapping(buf.add(self.tail), buf, tail_len); + // ABCDEFGH.... + + self.tail = 0; + self.head = len; + } + } else if free >= self.head { + // there is enough free space to copy the head in one go, + // this means that we first shift the tail forwards, and then + // copy the head to the correct position. + // + // from: FGH....ABCDE + // to: ...ABCDEFGH. + unsafe { + ptr::copy(buf.add(self.tail), buf.add(self.head), tail_len); + // FGHABCDE.... + ptr::copy_nonoverlapping(buf, buf.add(self.head + tail_len), self.head); + // ...ABCDEFGH. + + self.tail = self.head; + self.head = self.tail + len; + } + } else { + // free is smaller than both head and tail, + // this means we have to slowly "swap" the tail and the head. + // + // from: EFGHI...ABCD or HIJK.ABCDEFG + // to: ABCDEFGHI... or ABCDEFGHIJK. + let mut left_edge: usize = 0; + let mut right_edge: usize = self.tail; + unsafe { + // The general problem looks like this + // GHIJKLM...ABCDEF - before any swaps + // ABCDEFM...GHIJKL - after 1 pass of swaps + // ABCDEFGHIJM...KL - swap until the left edge reaches the temp store + // - then restart the algorithm with a new (smaller) store + // Sometimes the temp store is reached when the right edge is at the end + // of the buffer - this means we've hit the right order with fewer swaps! + // E.g + // EF..ABCD + // ABCDEF.. - after four only swaps we've finished + while left_edge < len && right_edge != cap { + let mut right_offset = 0; + for i in left_edge..right_edge { + right_offset = (i - left_edge) % (cap - right_edge); + let src: isize = (right_edge + right_offset) as isize; + ptr::swap(buf.add(i), buf.offset(src)); + } + let n_ops = right_edge - left_edge; + left_edge += n_ops; + right_edge += right_offset + 1; + } + + self.tail = 0; + self.head = len; + } + } + + let tail = self.tail; + let head = self.head; + unsafe { &mut self.buffer_as_mut_slice()[tail..head] } + } + + /// Rotates the double-ended queue `mid` places to the left. + /// + /// Equivalently, + /// - Rotates item `mid` into the first position. + /// - Pops the first `mid` items and pushes them to the end. + /// - Rotates `len() - mid` places to the right. + /// + /// # Panics + /// + /// If `mid` is greater than `len()`. Note that `mid == len()` + /// does _not_ panic and is a no-op rotation. + /// + /// # Complexity + /// + /// Takes `*O*(min(mid, len() - mid))` time and no extra space. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf: VecDeque<_> = (0..10).collect(); + /// + /// buf.rotate_left(3); + /// assert_eq!(buf, [3, 4, 5, 6, 7, 8, 9, 0, 1, 2]); + /// + /// for i in 1..10 { + /// assert_eq!(i * 3 % 10, buf[0]); + /// buf.rotate_left(3); + /// } + /// assert_eq!(buf, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]); + /// ``` + #[stable(feature = "vecdeque_rotate", since = "1.36.0")] + pub fn rotate_left(&mut self, mid: usize) { + assert!(mid <= self.len()); + let k = self.len() - mid; + if mid <= k { + unsafe { self.rotate_left_inner(mid) } + } else { + unsafe { self.rotate_right_inner(k) } + } + } + + /// Rotates the double-ended queue `k` places to the right. + /// + /// Equivalently, + /// - Rotates the first item into position `k`. + /// - Pops the last `k` items and pushes them to the front. + /// - Rotates `len() - k` places to the left. + /// + /// # Panics + /// + /// If `k` is greater than `len()`. Note that `k == len()` + /// does _not_ panic and is a no-op rotation. + /// + /// # Complexity + /// + /// Takes `*O*(min(k, len() - k))` time and no extra space. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf: VecDeque<_> = (0..10).collect(); + /// + /// buf.rotate_right(3); + /// assert_eq!(buf, [7, 8, 9, 0, 1, 2, 3, 4, 5, 6]); + /// + /// for i in 1..10 { + /// assert_eq!(0, buf[i * 3 % 10]); + /// buf.rotate_right(3); + /// } + /// assert_eq!(buf, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]); + /// ``` + #[stable(feature = "vecdeque_rotate", since = "1.36.0")] + pub fn rotate_right(&mut self, k: usize) { + assert!(k <= self.len()); + let mid = self.len() - k; + if k <= mid { + unsafe { self.rotate_right_inner(k) } + } else { + unsafe { self.rotate_left_inner(mid) } + } + } + + // SAFETY: the following two methods require that the rotation amount + // be less than half the length of the deque. + // + // `wrap_copy` requires that `min(x, cap() - x) + copy_len <= cap()`, + // but than `min` is never more than half the capacity, regardless of x, + // so it's sound to call here because we're calling with something + // less than half the length, which is never above half the capacity. + + unsafe fn rotate_left_inner(&mut self, mid: usize) { + debug_assert!(mid * 2 <= self.len()); + unsafe { + self.wrap_copy(self.head, self.tail, mid); + } + self.head = self.wrap_add(self.head, mid); + self.tail = self.wrap_add(self.tail, mid); + } + + unsafe fn rotate_right_inner(&mut self, k: usize) { + debug_assert!(k * 2 <= self.len()); + self.head = self.wrap_sub(self.head, k); + self.tail = self.wrap_sub(self.tail, k); + unsafe { + self.wrap_copy(self.tail, self.head, k); + } + } + + /// Binary searches this sorted `VecDeque` for a given element. + /// + /// If the value is found then [`Result::Ok`] is returned, containing the + /// index of the matching element. If there are multiple matches, then any + /// one of the matches could be returned. If the value is not found then + /// [`Result::Err`] is returned, containing the index where a matching + /// element could be inserted while maintaining sorted order. + /// + /// # Examples + /// + /// Looks up a series of four elements. The first is found, with a + /// uniquely determined position; the second and third are not + /// found; the fourth could match any position in `[1, 4]`. + /// + /// ``` + /// #![feature(vecdeque_binary_search)] + /// use std::collections::VecDeque; + /// + /// let deque: VecDeque<_> = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into(); + /// + /// assert_eq!(deque.binary_search(&13), Ok(9)); + /// assert_eq!(deque.binary_search(&4), Err(7)); + /// assert_eq!(deque.binary_search(&100), Err(13)); + /// let r = deque.binary_search(&1); + /// assert!(matches!(r, Ok(1..=4))); + /// ``` + /// + /// If you want to insert an item to a sorted `VecDeque`, while maintaining + /// sort order: + /// + /// ``` + /// #![feature(vecdeque_binary_search)] + /// use std::collections::VecDeque; + /// + /// let mut deque: VecDeque<_> = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into(); + /// let num = 42; + /// let idx = deque.binary_search(&num).unwrap_or_else(|x| x); + /// deque.insert(idx, num); + /// assert_eq!(deque, &[0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]); + /// ``` + #[unstable(feature = "vecdeque_binary_search", issue = "78021")] + #[inline] + pub fn binary_search(&self, x: &T) -> Result + where + T: Ord, + { + self.binary_search_by(|e| e.cmp(x)) + } + + /// Binary searches this sorted `VecDeque` with a comparator function. + /// + /// The comparator function should implement an order consistent + /// with the sort order of the underlying `VecDeque`, returning an + /// order code that indicates whether its argument is `Less`, + /// `Equal` or `Greater` than the desired target. + /// + /// If the value is found then [`Result::Ok`] is returned, containing the + /// index of the matching element. If there are multiple matches, then any + /// one of the matches could be returned. If the value is not found then + /// [`Result::Err`] is returned, containing the index where a matching + /// element could be inserted while maintaining sorted order. + /// + /// # Examples + /// + /// Looks up a series of four elements. The first is found, with a + /// uniquely determined position; the second and third are not + /// found; the fourth could match any position in `[1, 4]`. + /// + /// ``` + /// #![feature(vecdeque_binary_search)] + /// use std::collections::VecDeque; + /// + /// let deque: VecDeque<_> = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into(); + /// + /// assert_eq!(deque.binary_search_by(|x| x.cmp(&13)), Ok(9)); + /// assert_eq!(deque.binary_search_by(|x| x.cmp(&4)), Err(7)); + /// assert_eq!(deque.binary_search_by(|x| x.cmp(&100)), Err(13)); + /// let r = deque.binary_search_by(|x| x.cmp(&1)); + /// assert!(matches!(r, Ok(1..=4))); + /// ``` + #[unstable(feature = "vecdeque_binary_search", issue = "78021")] + pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result + where + F: FnMut(&'a T) -> Ordering, + { + let (front, back) = self.as_slices(); + + if let Some(Ordering::Less | Ordering::Equal) = back.first().map(|elem| f(elem)) { + back.binary_search_by(f).map(|idx| idx + front.len()).map_err(|idx| idx + front.len()) + } else { + front.binary_search_by(f) + } + } + + /// Binary searches this sorted `VecDeque` with a key extraction function. + /// + /// Assumes that the `VecDeque` is sorted by the key, for instance with + /// [`make_contiguous().sort_by_key()`](#method.make_contiguous) using the same + /// key extraction function. + /// + /// If the value is found then [`Result::Ok`] is returned, containing the + /// index of the matching element. If there are multiple matches, then any + /// one of the matches could be returned. If the value is not found then + /// [`Result::Err`] is returned, containing the index where a matching + /// element could be inserted while maintaining sorted order. + /// + /// # Examples + /// + /// Looks up a series of four elements in a slice of pairs sorted by + /// their second elements. The first is found, with a uniquely + /// determined position; the second and third are not found; the + /// fourth could match any position in `[1, 4]`. + /// + /// ``` + /// #![feature(vecdeque_binary_search)] + /// use std::collections::VecDeque; + /// + /// let deque: VecDeque<_> = vec![(0, 0), (2, 1), (4, 1), (5, 1), + /// (3, 1), (1, 2), (2, 3), (4, 5), (5, 8), (3, 13), + /// (1, 21), (2, 34), (4, 55)].into(); + /// + /// assert_eq!(deque.binary_search_by_key(&13, |&(a,b)| b), Ok(9)); + /// assert_eq!(deque.binary_search_by_key(&4, |&(a,b)| b), Err(7)); + /// assert_eq!(deque.binary_search_by_key(&100, |&(a,b)| b), Err(13)); + /// let r = deque.binary_search_by_key(&1, |&(a,b)| b); + /// assert!(matches!(r, Ok(1..=4))); + /// ``` + #[unstable(feature = "vecdeque_binary_search", issue = "78021")] + #[inline] + pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result + where + F: FnMut(&'a T) -> B, + B: Ord, + { + self.binary_search_by(|k| f(k).cmp(b)) + } +} + +impl VecDeque { + /// Modifies the `VecDeque` in-place so that `len()` is equal to new_len, + /// either by removing excess elements from the back or by appending clones of `value` + /// to the back. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.push_back(5); + /// buf.push_back(10); + /// buf.push_back(15); + /// assert_eq!(buf, [5, 10, 15]); + /// + /// buf.resize(2, 0); + /// assert_eq!(buf, [5, 10]); + /// + /// buf.resize(5, 20); + /// assert_eq!(buf, [5, 10, 20, 20, 20]); + /// ``` + #[stable(feature = "deque_extras", since = "1.16.0")] + pub fn resize(&mut self, new_len: usize, value: T) { + self.resize_with(new_len, || value.clone()); + } +} + +/// Returns the index in the underlying buffer for a given logical element index. +#[inline] +fn wrap_index(index: usize, size: usize) -> usize { + // size is always a power of 2 + debug_assert!(size.is_power_of_two()); + index & (size - 1) +} + +/// Calculate the number of elements left to be read in the buffer +#[inline] +fn count(tail: usize, head: usize, size: usize) -> usize { + // size is always a power of 2 + (head.wrapping_sub(tail)) & (size - 1) +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl PartialEq for VecDeque { + fn eq(&self, other: &VecDeque) -> bool { + if self.len() != other.len() { + return false; + } + let (sa, sb) = self.as_slices(); + let (oa, ob) = other.as_slices(); + if sa.len() == oa.len() { + sa == oa && sb == ob + } else if sa.len() < oa.len() { + // Always divisible in three sections, for example: + // self: [a b c|d e f] + // other: [0 1 2 3|4 5] + // front = 3, mid = 1, + // [a b c] == [0 1 2] && [d] == [3] && [e f] == [4 5] + let front = sa.len(); + let mid = oa.len() - front; + + let (oa_front, oa_mid) = oa.split_at(front); + let (sb_mid, sb_back) = sb.split_at(mid); + debug_assert_eq!(sa.len(), oa_front.len()); + debug_assert_eq!(sb_mid.len(), oa_mid.len()); + debug_assert_eq!(sb_back.len(), ob.len()); + sa == oa_front && sb_mid == oa_mid && sb_back == ob + } else { + let front = oa.len(); + let mid = sa.len() - front; + + let (sa_front, sa_mid) = sa.split_at(front); + let (ob_mid, ob_back) = ob.split_at(mid); + debug_assert_eq!(sa_front.len(), oa.len()); + debug_assert_eq!(sa_mid.len(), ob_mid.len()); + debug_assert_eq!(sb.len(), ob_back.len()); + sa_front == oa && sa_mid == ob_mid && sb == ob_back + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Eq for VecDeque {} + +__impl_slice_eq1! { [] VecDeque, Vec, } +__impl_slice_eq1! { [] VecDeque, &[B], } +__impl_slice_eq1! { [] VecDeque, &mut [B], } +__impl_slice_eq1! { [const N: usize] VecDeque, [B; N], } +__impl_slice_eq1! { [const N: usize] VecDeque, &[B; N], } +__impl_slice_eq1! { [const N: usize] VecDeque, &mut [B; N], } + +#[stable(feature = "rust1", since = "1.0.0")] +impl PartialOrd for VecDeque { + fn partial_cmp(&self, other: &VecDeque) -> Option { + self.iter().partial_cmp(other.iter()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Ord for VecDeque { + #[inline] + fn cmp(&self, other: &VecDeque) -> Ordering { + self.iter().cmp(other.iter()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Hash for VecDeque { + fn hash(&self, state: &mut H) { + self.len().hash(state); + let (a, b) = self.as_slices(); + Hash::hash_slice(a, state); + Hash::hash_slice(b, state); + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Index for VecDeque { + type Output = A; + + #[inline] + fn index(&self, index: usize) -> &A { + self.get(index).expect("Out of bounds access") + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl IndexMut for VecDeque { + #[inline] + fn index_mut(&mut self, index: usize) -> &mut A { + self.get_mut(index).expect("Out of bounds access") + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl FromIterator for VecDeque { + fn from_iter>(iter: T) -> VecDeque { + let iterator = iter.into_iter(); + let (lower, _) = iterator.size_hint(); + let mut deq = VecDeque::with_capacity(lower); + deq.extend(iterator); + deq + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl IntoIterator for VecDeque { + type Item = T; + type IntoIter = IntoIter; + + /// Consumes the `VecDeque` into a front-to-back iterator yielding elements by + /// value. + fn into_iter(self) -> IntoIter { + IntoIter { inner: self } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> IntoIterator for &'a VecDeque { + type Item = &'a T; + type IntoIter = Iter<'a, T>; + + fn into_iter(self) -> Iter<'a, T> { + self.iter() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> IntoIterator for &'a mut VecDeque { + type Item = &'a mut T; + type IntoIter = IterMut<'a, T>; + + fn into_iter(self) -> IterMut<'a, T> { + self.iter_mut() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Extend for VecDeque { + fn extend>(&mut self, iter: T) { + // This function should be the moral equivalent of: + // + // for item in iter.into_iter() { + // self.push_back(item); + // } + let mut iter = iter.into_iter(); + while let Some(element) = iter.next() { + if self.len() == self.capacity() { + let (lower, _) = iter.size_hint(); + self.reserve(lower.saturating_add(1)); + } + + let head = self.head; + self.head = self.wrap_add(self.head, 1); + unsafe { + self.buffer_write(head, element); + } + } + } + + #[inline] + fn extend_one(&mut self, elem: A) { + self.push_back(elem); + } + + #[inline] + fn extend_reserve(&mut self, additional: usize) { + self.reserve(additional); + } +} + +#[stable(feature = "extend_ref", since = "1.2.0")] +impl<'a, T: 'a + Copy> Extend<&'a T> for VecDeque { + fn extend>(&mut self, iter: I) { + self.extend(iter.into_iter().cloned()); + } + + #[inline] + fn extend_one(&mut self, &elem: &T) { + self.push_back(elem); + } + + #[inline] + fn extend_reserve(&mut self, additional: usize) { + self.reserve(additional); + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl fmt::Debug for VecDeque { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_list().entries(self).finish() + } +} + +#[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")] +impl From> for VecDeque { + /// Turn a [`Vec`] into a [`VecDeque`]. + /// + /// [`Vec`]: crate::vec::Vec + /// [`VecDeque`]: crate::collections::VecDeque + /// + /// This avoids reallocating where possible, but the conditions for that are + /// strict, and subject to change, and so shouldn't be relied upon unless the + /// `Vec` came from `From>` and hasn't been reallocated. + fn from(other: Vec) -> Self { + unsafe { + let mut other = ManuallyDrop::new(other); + let other_buf = other.as_mut_ptr(); + let mut buf = RawVec::from_raw_parts(other_buf, other.capacity()); + let len = other.len(); + + // We need to extend the buf if it's not a power of two, too small + // or doesn't have at least one free space + if !buf.capacity().is_power_of_two() + || (buf.capacity() < (MINIMUM_CAPACITY + 1)) + || (buf.capacity() == len) + { + let cap = cmp::max(buf.capacity() + 1, MINIMUM_CAPACITY + 1).next_power_of_two(); + buf.reserve_exact(len, cap - len); + } + + VecDeque { tail: 0, head: len, buf } + } + } +} + +#[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")] +impl From> for Vec { + /// Turn a [`VecDeque`] into a [`Vec`]. + /// + /// [`Vec`]: crate::vec::Vec + /// [`VecDeque`]: crate::collections::VecDeque + /// + /// This never needs to re-allocate, but does need to do *O*(*n*) data movement if + /// the circular buffer doesn't happen to be at the beginning of the allocation. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// // This one is *O*(1). + /// let deque: VecDeque<_> = (1..5).collect(); + /// let ptr = deque.as_slices().0.as_ptr(); + /// let vec = Vec::from(deque); + /// assert_eq!(vec, [1, 2, 3, 4]); + /// assert_eq!(vec.as_ptr(), ptr); + /// + /// // This one needs data rearranging. + /// let mut deque: VecDeque<_> = (1..5).collect(); + /// deque.push_front(9); + /// deque.push_front(8); + /// let ptr = deque.as_slices().1.as_ptr(); + /// let vec = Vec::from(deque); + /// assert_eq!(vec, [8, 9, 1, 2, 3, 4]); + /// assert_eq!(vec.as_ptr(), ptr); + /// ``` + fn from(mut other: VecDeque) -> Self { + other.make_contiguous(); + + unsafe { + let other = ManuallyDrop::new(other); + let buf = other.buf.ptr(); + let len = other.len(); + let cap = other.cap(); + + if other.head != 0 { + ptr::copy(buf.add(other.tail), buf, len); + } + Vec::from_raw_parts(buf, len, cap) + } + } +} diff --git a/library/alloc/src/collections/vec_deque/pair_slices.rs b/library/alloc/src/collections/vec_deque/pair_slices.rs new file mode 100644 index 00000000000..812765d0b0d --- /dev/null +++ b/library/alloc/src/collections/vec_deque/pair_slices.rs @@ -0,0 +1,66 @@ +use core::array; +use core::cmp::{self}; +use core::mem::replace; + +use super::VecDeque; + +/// PairSlices pairs up equal length slice parts of two deques +/// +/// For example, given deques "A" and "B" with the following division into slices: +/// +/// A: [0 1 2] [3 4 5] +/// B: [a b] [c d e] +/// +/// It produces the following sequence of matching slices: +/// +/// ([0 1], [a b]) +/// (\[2\], \[c\]) +/// ([3 4], [d e]) +/// +/// and the uneven remainder of either A or B is skipped. +pub struct PairSlices<'a, 'b, T> { + pub(crate) a0: &'a mut [T], + pub(crate) a1: &'a mut [T], + pub(crate) b0: &'b [T], + pub(crate) b1: &'b [T], +} + +impl<'a, 'b, T> PairSlices<'a, 'b, T> { + pub fn from(to: &'a mut VecDeque, from: &'b VecDeque) -> Self { + let (a0, a1) = to.as_mut_slices(); + let (b0, b1) = from.as_slices(); + PairSlices { a0, a1, b0, b1 } + } + + pub fn has_remainder(&self) -> bool { + !self.b0.is_empty() + } + + pub fn remainder(self) -> impl Iterator { + array::IntoIter::new([self.b0, self.b1]) + } +} + +impl<'a, 'b, T> Iterator for PairSlices<'a, 'b, T> { + type Item = (&'a mut [T], &'b [T]); + fn next(&mut self) -> Option { + // Get next part length + let part = cmp::min(self.a0.len(), self.b0.len()); + if part == 0 { + return None; + } + let (p0, p1) = replace(&mut self.a0, &mut []).split_at_mut(part); + let (q0, q1) = self.b0.split_at(part); + + // Move a1 into a0, if it's empty (and b1, b0 the same way). + self.a0 = p1; + self.b0 = q1; + if self.a0.is_empty() { + self.a0 = replace(&mut self.a1, &mut []); + } + if self.b0.is_empty() { + self.b0 = replace(&mut self.b1, &[]); + } + Some((p0, q0)) + } +} diff --git a/library/alloc/src/collections/vec_deque/ring_slices.rs b/library/alloc/src/collections/vec_deque/ring_slices.rs new file mode 100644 index 00000000000..dd0fa7d6074 --- /dev/null +++ b/library/alloc/src/collections/vec_deque/ring_slices.rs @@ -0,0 +1,56 @@ +use core::ptr::{self}; + +/// Returns the two slices that cover the `VecDeque`'s valid range +pub trait RingSlices: Sized { + fn slice(self, from: usize, to: usize) -> Self; + fn split_at(self, i: usize) -> (Self, Self); + + fn ring_slices(buf: Self, head: usize, tail: usize) -> (Self, Self) { + let contiguous = tail <= head; + if contiguous { + let (empty, buf) = buf.split_at(0); + (buf.slice(tail, head), empty) + } else { + let (mid, right) = buf.split_at(tail); + let (left, _) = mid.split_at(head); + (right, left) + } + } +} + +impl RingSlices for &[T] { + fn slice(self, from: usize, to: usize) -> Self { + &self[from..to] + } + fn split_at(self, i: usize) -> (Self, Self) { + (*self).split_at(i) + } +} + +impl RingSlices for &mut [T] { + fn slice(self, from: usize, to: usize) -> Self { + &mut self[from..to] + } + fn split_at(self, i: usize) -> (Self, Self) { + (*self).split_at_mut(i) + } +} + +impl RingSlices for *mut [T] { + fn slice(self, from: usize, to: usize) -> Self { + assert!(from <= to && to < self.len()); + // Not using `get_unchecked_mut` to keep this a safe operation. + let len = to - from; + ptr::slice_from_raw_parts_mut(self.as_mut_ptr().wrapping_add(from), len) + } + + fn split_at(self, mid: usize) -> (Self, Self) { + let len = self.len(); + let ptr = self.as_mut_ptr(); + assert!(mid <= len); + ( + ptr::slice_from_raw_parts_mut(ptr, mid), + ptr::slice_from_raw_parts_mut(ptr.wrapping_add(mid), len - mid), + ) + } +} -- cgit 1.4.1-3-g733a5