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| author | Murarth <murarth@gmail.com> | 2017-06-13 15:52:59 -0700 |
|---|---|---|
| committer | Murarth <murarth@gmail.com> | 2017-06-13 23:37:34 -0700 |
| commit | eadda7665eb31b1e7cb94a503b4d5cf5c75474c0 (patch) | |
| tree | 406691dc732c762e1424f5110fcbfca97f0b1302 /src/liballoc/vec_deque.rs | |
| parent | e40ef964fe491b19c22dfb8dd36d1eab14223c36 (diff) | |
| download | rust-eadda7665eb31b1e7cb94a503b4d5cf5c75474c0.tar.gz rust-eadda7665eb31b1e7cb94a503b4d5cf5c75474c0.zip | |
Merge crate `collections` into `alloc`
Diffstat (limited to 'src/liballoc/vec_deque.rs')
| -rw-r--r-- | src/liballoc/vec_deque.rs | 2970 |
1 files changed, 2970 insertions, 0 deletions
diff --git a/src/liballoc/vec_deque.rs b/src/liballoc/vec_deque.rs new file mode 100644 index 00000000000..18175a5d01b --- /dev/null +++ b/src/liballoc/vec_deque.rs @@ -0,0 +1,2970 @@ +// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +//! 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::Ordering; +use core::fmt; +use core::iter::{repeat, FromIterator, FusedIterator}; +use core::mem; +use core::ops::{Index, IndexMut, Place, Placer, InPlace}; +use core::ptr; +use core::ptr::Shared; +use core::slice; + +use core::hash::{Hash, Hasher}; +use core::cmp; + +use raw_vec::RawVec; + +use super::range::RangeArgument; +use Bound::{Excluded, Included, Unbounded}; +use super::vec::Vec; + +const INITIAL_CAPACITY: usize = 7; // 2^3 - 1 +const MINIMUM_CAPACITY: usize = 1; // 2 - 1 +#[cfg(target_pointer_width = "32")] +const MAXIMUM_ZST_CAPACITY: usize = 1 << (32 - 1); // Largest possible power of two +#[cfg(target_pointer_width = "64")] +const MAXIMUM_ZST_CAPACITY: usize = 1 << (64 - 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. +/// +/// [`push_back`]: #method.push_back +/// [`pop_front`]: #method.pop_front +/// [`extend`]: #method.extend +/// [`append`]: #method.append +#[stable(feature = "rust1", since = "1.0.0")] +pub struct VecDeque<T> { + // 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<T>, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: Clone> Clone for VecDeque<T> { + fn clone(&self) -> VecDeque<T> { + self.iter().cloned().collect() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<#[may_dangle] T> Drop for VecDeque<T> { + fn drop(&mut self) { + let (front, back) = self.as_mut_slices(); + unsafe { + // use drop for [T] + ptr::drop_in_place(front); + ptr::drop_in_place(back); + } + // RawVec handles deallocation + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> Default for VecDeque<T> { + /// Creates an empty `VecDeque<T>`. + #[inline] + fn default() -> VecDeque<T> { + VecDeque::new() + } +} + +impl<T> VecDeque<T> { + /// Marginally more convenient + #[inline] + fn ptr(&self) -> *mut T { + self.buf.ptr() + } + + /// Marginally more convenient + #[inline] + fn cap(&self) -> usize { + if mem::size_of::<T>() == 0 { + // For zero sized types, we are always at maximum capacity + MAXIMUM_ZST_CAPACITY + } else { + self.buf.cap() + } + } + + /// Turn ptr into a slice + #[inline] + unsafe fn buffer_as_slice(&self) -> &[T] { + 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] { + 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 { + ptr::read(self.ptr().offset(off as isize)) + } + + /// Writes an element into the buffer, moving it. + #[inline] + unsafe fn buffer_write(&mut self, off: usize, value: T) { + ptr::write(self.ptr().offset(off as isize), value); + } + + /// Returns `true` if and only 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()); + ptr::copy(self.ptr().offset(src as isize), + self.ptr().offset(dst as isize), + 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()); + ptr::copy_nonoverlapping(self.ptr().offset(src as isize), + self.ptr().offset(dst as isize), + 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 . . . + // + 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 . + // + 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 . + // + 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 . . . + // + 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 . . . + // + 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; + 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; + 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_cap. + #[inline] + unsafe fn handle_cap_increase(&mut self, old_cap: usize) { + let new_cap = 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_cap - self.tail { + // B + self.copy_nonoverlapping(old_cap, 0, self.head); + self.head += old_cap; + debug_assert!(self.head > self.tail); + } else { + // C + let new_tail = new_cap - (old_cap - self.tail); + self.copy_nonoverlapping(new_tail, self.tail, old_cap - 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<T> VecDeque<T> { + /// Creates an empty `VecDeque`. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let vector: VecDeque<u32> = VecDeque::new(); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn new() -> VecDeque<T> { + VecDeque::with_capacity(INITIAL_CAPACITY) + } + + /// Creates an empty `VecDeque` with space for at least `n` elements. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let vector: VecDeque<u32> = VecDeque::with_capacity(10); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn with_capacity(n: usize) -> VecDeque<T> { + // +1 since the ringbuffer always leaves one space empty + let cap = cmp::max(n + 1, MINIMUM_CAPACITY + 1).next_power_of_two(); + assert!(cap > n, "capacity overflow"); + + VecDeque { + tail: 0, + head: 0, + buf: RawVec::with_capacity(cap), + } + } + + /// Retrieves an element in the `VecDeque` by 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().offset(idx as isize)) } + } else { + None + } + } + + /// Retrieves an element in the `VecDeque` mutably by 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().offset(idx as isize)) } + } else { + None + } + } + + /// Swaps elements at indices `i` and `j`. + /// + /// `i` and `j` may be equal. + /// + /// Fails if there is no element with either 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, [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().offset(ri as isize), + self.ptr().offset(rj as isize)) + } + } + + /// Returns the number of elements the `VecDeque` can hold without + /// reallocating. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let buf: VecDeque<i32> = 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<i32> = vec![1].into_iter().collect(); + /// buf.reserve_exact(10); + /// assert!(buf.capacity() >= 11); + /// ``` + /// + /// [`reserve`]: #method.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<i32> = 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 > self.capacity() { + self.buf.reserve_exact(used_cap, new_cap - used_cap); + unsafe { + self.handle_cap_increase(old_cap); + } + } + } + + /// 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) { + // +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(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`, dropping excess elements from the back. + /// + /// 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) { + for _ in len..self.len() { + self.pop_back(); + } + } + + /// 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::<Vec<&mut i32>>()[..], b); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn iter_mut(&mut self) -> IterMut<T> { + IterMut { + tail: self.tail, + head: self.head, + ring: unsafe { self.buffer_as_mut_slice() }, + } + } + + /// Returns a pair of slices which contain, in order, the contents of the + /// `VecDeque`. + /// + /// # 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`. + /// + /// # 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 + } + + /// Create 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 + /// (eg. 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::<VecDeque<_>>(); + /// 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<R>(&mut self, range: R) -> Drain<T> + where R: RangeArgument<usize> + { + // 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 len = self.len(); + let start = match range.start() { + Included(&n) => n, + Excluded(&n) => n + 1, + Unbounded => 0, + }; + let end = match range.end() { + Included(&n) => n + 1, + Excluded(&n) => n, + Unbounded => len, + }; + assert!(start <= end, "drain lower bound was too large"); + assert!(end <= len, "drain upper bound was too large"); + + // 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 drain_tail = self.wrap_add(self.tail, start); + let drain_head = self.wrap_add(self.tail, end); + 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: unsafe { Shared::new(self as *mut _) }, + after_tail: drain_head, + after_head: head, + iter: Iter { + tail: drain_tail, + head: drain_head, + ring: unsafe { self.buffer_as_mut_slice() }, + }, + } + } + + /// Clears the buffer, 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.drain(..); + } + + /// Returns `true` if the `VecDeque` contains an element equal to the + /// given value. + /// + /// # Examples + /// + /// ``` + /// use std::collections::VecDeque; + /// + /// let mut vector: VecDeque<u32> = 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<T> + { + 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<T> { + if self.is_empty() { + None + } else { + let tail = self.tail; + self.tail = self.wrap_add(self.tail, 1); + unsafe { Some(self.buffer_read(tail)) } + } + } + + /// 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) { + self.grow_if_necessary(); + + 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) { + self.grow_if_necessary(); + + let head = self.head; + self.head = self.wrap_add(self.head, 1); + unsafe { self.buffer_write(head, value) } + } + + /// 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<T> { + if self.is_empty() { + None + } else { + self.head = self.wrap_sub(self.head, 1); + let head = self.head; + unsafe { Some(self.buffer_read(head)) } + } + } + + #[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 + /// 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<T> { + let length = self.len(); + if length > 0 && index < length - 1 { + self.swap(index, length - 1); + } else if index >= length { + return None; + } + self.pop_back() + } + + /// 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<T> { + let length = self.len(); + if length > 0 && index < length && index != 0 { + self.swap(index, 0); + } else if index >= length { + return None; + } + self.pop_front() + } + + /// 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"); + self.grow_if_necessary(); + + // 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<T> { + 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); + } + } + } + + return elem; + } + + /// Splits the collection into two at the given index. + /// + /// Returns a newly allocated `Self`. `self` contains elements `[0, at)`, + /// and the returned `Self` 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] + #[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().offset(at as isize), + other.ptr(), + amount_in_first); + + // just take all of the second half. + ptr::copy_nonoverlapping(second_half.as_ptr(), + other.ptr().offset(amount_in_first as isize), + 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().offset(offset as isize), + 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 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]); + /// ``` + #[stable(feature = "vec_deque_retain", since = "1.4.0")] + pub fn retain<F>(&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] + fn grow_if_necessary(&mut self) { + if self.is_full() { + let old_cap = self.cap(); + self.buf.double(); + unsafe { + self.handle_cap_increase(old_cap); + } + debug_assert!(!self.is_full()); + } + } + + /// Returns a place for insertion at the back of the `VecDeque`. + /// + /// Using this method with placement syntax is equivalent to [`push_back`](#method.push_back), + /// but may be more efficient. + /// + /// # Examples + /// + /// ``` + /// #![feature(collection_placement)] + /// #![feature(placement_in_syntax)] + /// + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.place_back() <- 3; + /// buf.place_back() <- 4; + /// assert_eq!(&buf, &[3, 4]); + /// ``` + #[unstable(feature = "collection_placement", + reason = "placement protocol is subject to change", + issue = "30172")] + pub fn place_back(&mut self) -> PlaceBack<T> { + PlaceBack { vec_deque: self } + } + + /// Returns a place for insertion at the front of the `VecDeque`. + /// + /// Using this method with placement syntax is equivalent to [`push_front`](#method.push_front), + /// but may be more efficient. + /// + /// # Examples + /// + /// ``` + /// #![feature(collection_placement)] + /// #![feature(placement_in_syntax)] + /// + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::new(); + /// buf.place_front() <- 3; + /// buf.place_front() <- 4; + /// assert_eq!(&buf, &[4, 3]); + /// ``` + #[unstable(feature = "collection_placement", + reason = "placement protocol is subject to change", + issue = "30172")] + pub fn place_front(&mut self) -> PlaceFront<T> { + PlaceFront { vec_deque: self } + } +} + +impl<T: Clone> VecDeque<T> { + /// Modifies the `VecDeque` in-place so that `len()` is equal to new_len, + /// either by removing excess elements 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) { + let len = self.len(); + + if new_len > len { + self.extend(repeat(value).take(new_len - len)) + } else { + self.truncate(new_len); + } + } +} + +/// 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<'a, T> RingSlices for &'a [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<'a, T> RingSlices for &'a 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) + } +} + +/// 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`]: struct.VecDeque.html#method.iter +/// [`VecDeque`]: struct.VecDeque.html +#[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<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + f.debug_tuple("Iter") + .field(&self.ring) + .field(&self.tail) + .field(&self.head) + .finish() + } +} + +// FIXME(#19839) Remove in favor of `#[derive(Clone)]` +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> Clone for Iter<'a, T> { + fn clone(&self) -> Iter<'a, T> { + 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<usize>) { + let len = count(self.tail, self.head, self.ring.len()); + (len, Some(len)) + } + + fn fold<Acc, F>(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) + } +} + +#[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)) } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> ExactSizeIterator for Iter<'a, T> { + fn is_empty(&self) -> bool { + self.head == self.tail + } +} + +#[unstable(feature = "fused", issue = "35602")] +impl<'a, T> FusedIterator for Iter<'a, 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`]: struct.VecDeque.html#method.iter_mut +/// [`VecDeque`]: struct.VecDeque.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct IterMut<'a, T: 'a> { + ring: &'a mut [T], + tail: usize, + head: usize, +} + +#[stable(feature = "collection_debug", since = "1.17.0")] +impl<'a, T: 'a + fmt::Debug> fmt::Debug for IterMut<'a, T> { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + f.debug_tuple("IterMut") + .field(&self.ring) + .field(&self.tail) + .field(&self.head) + .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 as *mut _)) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + let len = count(self.tail, self.head, self.ring.len()); + (len, Some(len)) + } + + fn fold<Acc, F>(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_mut().fold(accum, &mut f); + back.iter_mut().fold(accum, &mut f) + } +} + +#[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 as *mut _)) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> ExactSizeIterator for IterMut<'a, T> { + fn is_empty(&self) -> bool { + self.head == self.tail + } +} + +#[unstable(feature = "fused", issue = "35602")] +impl<'a, T> FusedIterator for IterMut<'a, T> {} + +/// An owning iterator over the elements of a `VecDeque`. +/// +/// This `struct` is created by the [`into_iter`] method on [`VecDeque`][`VecDeque`] +/// (provided by the `IntoIterator` trait). See its documentation for more. +/// +/// [`into_iter`]: struct.VecDeque.html#method.into_iter +/// [`VecDeque`]: struct.VecDeque.html +#[derive(Clone)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct IntoIter<T> { + inner: VecDeque<T>, +} + +#[stable(feature = "collection_debug", since = "1.17.0")] +impl<T: fmt::Debug> fmt::Debug for IntoIter<T> { + 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<T> Iterator for IntoIter<T> { + type Item = T; + + #[inline] + fn next(&mut self) -> Option<T> { + self.inner.pop_front() + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + let len = self.inner.len(); + (len, Some(len)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> DoubleEndedIterator for IntoIter<T> { + #[inline] + fn next_back(&mut self) -> Option<T> { + self.inner.pop_back() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> ExactSizeIterator for IntoIter<T> { + fn is_empty(&self) -> bool { + self.inner.is_empty() + } +} + +#[unstable(feature = "fused", issue = "35602")] +impl<T> FusedIterator for IntoIter<T> {} + +/// A draining iterator over the elements of a `VecDeque`. +/// +/// This `struct` is created by the [`drain`] method on [`VecDeque`]. See its +/// documentation for more. +/// +/// [`drain`]: struct.VecDeque.html#method.drain +/// [`VecDeque`]: struct.VecDeque.html +#[stable(feature = "drain", since = "1.6.0")] +pub struct Drain<'a, T: 'a> { + after_tail: usize, + after_head: usize, + iter: Iter<'a, T>, + deque: Shared<VecDeque<T>>, +} + +#[stable(feature = "collection_debug", since = "1.17.0")] +impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + f.debug_tuple("Drain") + .field(&self.after_tail) + .field(&self.after_head) + .field(&self.iter) + .finish() + } +} + +#[stable(feature = "drain", since = "1.6.0")] +unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {} +#[stable(feature = "drain", since = "1.6.0")] +unsafe impl<'a, T: Send> Send for Drain<'a, T> {} + +#[stable(feature = "drain", since = "1.6.0")] +impl<'a, T: 'a> Drop for Drain<'a, T> { + fn drop(&mut self) { + for _ in self.by_ref() {} + + let source_deque = unsafe { self.deque.as_mut() }; + + // T = source_deque_tail; H = source_deque_head; t = drain_tail; h = drain_head + // + // T t h H + // [. . . o o x x o o . . .] + // + let orig_tail = source_deque.tail; + let drain_tail = source_deque.head; + let drain_head = self.after_tail; + let orig_head = self.after_head; + + let tail_len = count(orig_tail, drain_tail, source_deque.cap()); + let head_len = count(drain_head, orig_head, source_deque.cap()); + + // Restore the original head value + source_deque.head = orig_head; + + match (tail_len, head_len) { + (0, 0) => { + source_deque.head = 0; + source_deque.tail = 0; + } + (0, _) => { + source_deque.tail = drain_head; + } + (_, 0) => { + source_deque.head = drain_tail; + } + _ => unsafe { + if tail_len <= head_len { + source_deque.tail = source_deque.wrap_sub(drain_head, tail_len); + source_deque.wrap_copy(source_deque.tail, orig_tail, tail_len); + } else { + source_deque.head = source_deque.wrap_add(drain_tail, head_len); + source_deque.wrap_copy(drain_tail, drain_head, head_len); + } + }, + } + } +} + +#[stable(feature = "drain", since = "1.6.0")] +impl<'a, T: 'a> Iterator for Drain<'a, T> { + type Item = T; + + #[inline] + fn next(&mut self) -> Option<T> { + self.iter.next().map(|elt| unsafe { ptr::read(elt) }) + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.iter.size_hint() + } +} + +#[stable(feature = "drain", since = "1.6.0")] +impl<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<T> { + self.iter.next_back().map(|elt| unsafe { ptr::read(elt) }) + } +} + +#[stable(feature = "drain", since = "1.6.0")] +impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {} + +#[unstable(feature = "fused", issue = "35602")] +impl<'a, T: 'a> FusedIterator for Drain<'a, T> {} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<A: PartialEq> PartialEq for VecDeque<A> { + fn eq(&self, other: &VecDeque<A>) -> 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<A: Eq> Eq for VecDeque<A> {} + +macro_rules! __impl_slice_eq1 { + ($Lhs: ty, $Rhs: ty) => { + __impl_slice_eq1! { $Lhs, $Rhs, Sized } + }; + ($Lhs: ty, $Rhs: ty, $Bound: ident) => { + #[stable(feature = "vec-deque-partial-eq-slice", since = "1.17.0")] + impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> { + fn eq(&self, other: &$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<A>, Vec<B> } +__impl_slice_eq1! { VecDeque<A>, &'b [B] } +__impl_slice_eq1! { VecDeque<A>, &'b mut [B] } + +macro_rules! array_impls { + ($($N: expr)+) => { + $( + __impl_slice_eq1! { VecDeque<A>, [B; $N] } + __impl_slice_eq1! { VecDeque<A>, &'b [B; $N] } + __impl_slice_eq1! { VecDeque<A>, &'b mut [B; $N] } + )+ + } +} + +array_impls! { + 0 1 2 3 4 5 6 7 8 9 + 10 11 12 13 14 15 16 17 18 19 + 20 21 22 23 24 25 26 27 28 29 + 30 31 32 +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<A: PartialOrd> PartialOrd for VecDeque<A> { + fn partial_cmp(&self, other: &VecDeque<A>) -> Option<Ordering> { + self.iter().partial_cmp(other.iter()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<A: Ord> Ord for VecDeque<A> { + #[inline] + fn cmp(&self, other: &VecDeque<A>) -> Ordering { + self.iter().cmp(other.iter()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<A: Hash> Hash for VecDeque<A> { + fn hash<H: Hasher>(&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<A> Index<usize> for VecDeque<A> { + 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<A> IndexMut<usize> for VecDeque<A> { + #[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<A> FromIterator<A> for VecDeque<A> { + fn from_iter<T: IntoIterator<Item = A>>(iter: T) -> VecDeque<A> { + 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<T> IntoIterator for VecDeque<T> { + type Item = T; + type IntoIter = IntoIter<T>; + + /// Consumes the list into a front-to-back iterator yielding elements by + /// value. + fn into_iter(self) -> IntoIter<T> { + IntoIter { inner: self } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> IntoIterator for &'a VecDeque<T> { + 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<T> { + type Item = &'a mut T; + type IntoIter = IterMut<'a, T>; + + fn into_iter(mut self) -> IterMut<'a, T> { + self.iter_mut() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<A> Extend<A> for VecDeque<A> { + fn extend<T: IntoIterator<Item = A>>(&mut self, iter: T) { + for elt in iter { + self.push_back(elt); + } + } +} + +#[stable(feature = "extend_ref", since = "1.2.0")] +impl<'a, T: 'a + Copy> Extend<&'a T> for VecDeque<T> { + fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { + self.extend(iter.into_iter().cloned()); + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: fmt::Debug> fmt::Debug for VecDeque<T> { + 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<T> From<Vec<T>> for VecDeque<T> { + fn from(mut other: Vec<T>) -> Self { + unsafe { + let other_buf = other.as_mut_ptr(); + let mut buf = RawVec::from_raw_parts(other_buf, other.capacity()); + let len = other.len(); + mem::forget(other); + + // 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.cap().is_power_of_two() || (buf.cap() < (MINIMUM_CAPACITY + 1)) || + (buf.cap() == len) { + let cap = cmp::max(buf.cap() + 1, MINIMUM_CAPACITY + 1).next_power_of_two(); + buf.reserve_exact(len, cap - len); + } + + VecDeque { + tail: 0, + head: len, + buf: buf, + } + } + } +} + +#[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")] +impl<T> From<VecDeque<T>> for Vec<T> { + fn from(other: VecDeque<T>) -> Self { + unsafe { + let buf = other.buf.ptr(); + let len = other.len(); + let tail = other.tail; + let head = other.head; + let cap = other.cap(); + + // Need to move the ring to the front of the buffer, as vec will expect this. + if other.is_contiguous() { + ptr::copy(buf.offset(tail as isize), buf, len); + } else { + if (tail - head) >= cmp::min((cap - tail), head) { + // There is enough free space in the centre for the shortest block so we can + // do this in at most three copy moves. + if (cap - tail) > head { + // right hand block is the long one; move that enough for the left + ptr::copy(buf.offset(tail as isize), + buf.offset((tail - head) as isize), + cap - tail); + // copy left in the end + ptr::copy(buf, buf.offset((cap - head) as isize), head); + // shift the new thing to the start + ptr::copy(buf.offset((tail - head) as isize), buf, len); + } else { + // left hand block is the long one, we can do it in two! + ptr::copy(buf, buf.offset((cap - tail) as isize), head); + ptr::copy(buf.offset(tail as isize), buf, cap - tail); + } + } else { + // Need to use N swaps to move the ring + // We can use the space at the end of the ring as a temp store + + let mut left_edge: usize = 0; + let mut right_edge: usize = tail; + + // 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.offset(i as isize), buf.offset(src)); + } + let n_ops = right_edge - left_edge; + left_edge += n_ops; + right_edge += right_offset + 1; + + } + } + + } + let out = Vec::from_raw_parts(buf, len, cap); + mem::forget(other); + out + } + } +} + +/// A place for insertion at the back of a `VecDeque`. +/// +/// See [`VecDeque::place_back`](struct.VecDeque.html#method.place_back) for details. +#[must_use = "places do nothing unless written to with `<-` syntax"] +#[unstable(feature = "collection_placement", + reason = "struct name and placement protocol are subject to change", + issue = "30172")] +#[derive(Debug)] +pub struct PlaceBack<'a, T: 'a> { + vec_deque: &'a mut VecDeque<T>, +} + +#[unstable(feature = "collection_placement", + reason = "placement protocol is subject to change", + issue = "30172")] +impl<'a, T> Placer<T> for PlaceBack<'a, T> { + type Place = PlaceBack<'a, T>; + + fn make_place(self) -> Self { + self.vec_deque.grow_if_necessary(); + self + } +} + +#[unstable(feature = "collection_placement", + reason = "placement protocol is subject to change", + issue = "30172")] +impl<'a, T> Place<T> for PlaceBack<'a, T> { + fn pointer(&mut self) -> *mut T { + unsafe { self.vec_deque.ptr().offset(self.vec_deque.head as isize) } + } +} + +#[unstable(feature = "collection_placement", + reason = "placement protocol is subject to change", + issue = "30172")] +impl<'a, T> InPlace<T> for PlaceBack<'a, T> { + type Owner = &'a mut T; + + unsafe fn finalize(mut self) -> &'a mut T { + let head = self.vec_deque.head; + self.vec_deque.head = self.vec_deque.wrap_add(head, 1); + &mut *(self.vec_deque.ptr().offset(head as isize)) + } +} + +/// A place for insertion at the front of a `VecDeque`. +/// +/// See [`VecDeque::place_front`](struct.VecDeque.html#method.place_front) for details. +#[must_use = "places do nothing unless written to with `<-` syntax"] +#[unstable(feature = "collection_placement", + reason = "struct name and placement protocol are subject to change", + issue = "30172")] +#[derive(Debug)] +pub struct PlaceFront<'a, T: 'a> { + vec_deque: &'a mut VecDeque<T>, +} + +#[unstable(feature = "collection_placement", + reason = "placement protocol is subject to change", + issue = "30172")] +impl<'a, T> Placer<T> for PlaceFront<'a, T> { + type Place = PlaceFront<'a, T>; + + fn make_place(self) -> Self { + self.vec_deque.grow_if_necessary(); + self + } +} + +#[unstable(feature = "collection_placement", + reason = "placement protocol is subject to change", + issue = "30172")] +impl<'a, T> Place<T> for PlaceFront<'a, T> { + fn pointer(&mut self) -> *mut T { + let tail = self.vec_deque.wrap_sub(self.vec_deque.tail, 1); + unsafe { self.vec_deque.ptr().offset(tail as isize) } + } +} + +#[unstable(feature = "collection_placement", + reason = "placement protocol is subject to change", + issue = "30172")] +impl<'a, T> InPlace<T> for PlaceFront<'a, T> { + type Owner = &'a mut T; + + unsafe fn finalize(mut self) -> &'a mut T { + self.vec_deque.tail = self.vec_deque.wrap_sub(self.vec_deque.tail, 1); + &mut *(self.vec_deque.ptr().offset(self.vec_deque.tail as isize)) + } +} + +#[cfg(test)] +mod tests { + use test; + + use super::VecDeque; + + #[bench] + fn bench_push_back_100(b: &mut test::Bencher) { + let mut deq = VecDeque::with_capacity(101); + b.iter(|| { + for i in 0..100 { + deq.push_back(i); + } + deq.head = 0; + deq.tail = 0; + }) + } + + #[bench] + fn bench_push_front_100(b: &mut test::Bencher) { + let mut deq = VecDeque::with_capacity(101); + b.iter(|| { + for i in 0..100 { + deq.push_front(i); + } + deq.head = 0; + deq.tail = 0; + }) + } + + #[bench] + fn bench_pop_back_100(b: &mut test::Bencher) { + let mut deq = VecDeque::<i32>::with_capacity(101); + + b.iter(|| { + deq.head = 100; + deq.tail = 0; + while !deq.is_empty() { + test::black_box(deq.pop_back()); + } + }) + } + + #[bench] + fn bench_pop_front_100(b: &mut test::Bencher) { + let mut deq = VecDeque::<i32>::with_capacity(101); + + b.iter(|| { + deq.head = 100; + deq.tail = 0; + while !deq.is_empty() { + test::black_box(deq.pop_front()); + } + }) + } + + #[test] + fn test_swap_front_back_remove() { + fn test(back: bool) { + // This test checks that every single combination of tail position and length is tested. + // Capacity 15 should be large enough to cover every case. + let mut tester = VecDeque::with_capacity(15); + let usable_cap = tester.capacity(); + let final_len = usable_cap / 2; + + for len in 0..final_len { + let expected: VecDeque<_> = if back { + (0..len).collect() + } else { + (0..len).rev().collect() + }; + for tail_pos in 0..usable_cap { + tester.tail = tail_pos; + tester.head = tail_pos; + if back { + for i in 0..len * 2 { + tester.push_front(i); + } + for i in 0..len { + assert_eq!(tester.swap_remove_back(i), Some(len * 2 - 1 - i)); + } + } else { + for i in 0..len * 2 { + tester.push_back(i); + } + for i in 0..len { + let idx = tester.len() - 1 - i; + assert_eq!(tester.swap_remove_front(idx), Some(len * 2 - 1 - i)); + } + } + assert!(tester.tail < tester.cap()); + assert!(tester.head < tester.cap()); + assert_eq!(tester, expected); + } + } + } + test(true); + test(false); + } + + #[test] + fn test_insert() { + // This test checks that every single combination of tail position, length, and + // insertion position is tested. Capacity 15 should be large enough to cover every case. + + let mut tester = VecDeque::with_capacity(15); + // can't guarantee we got 15, so have to get what we got. + // 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else + // this test isn't covering what it wants to + let cap = tester.capacity(); + + + // len is the length *after* insertion + for len in 1..cap { + // 0, 1, 2, .., len - 1 + let expected = (0..).take(len).collect::<VecDeque<_>>(); + for tail_pos in 0..cap { + for to_insert in 0..len { + tester.tail = tail_pos; + tester.head = tail_pos; + for i in 0..len { + if i != to_insert { + tester.push_back(i); + } + } + tester.insert(to_insert, to_insert); + assert!(tester.tail < tester.cap()); + assert!(tester.head < tester.cap()); + assert_eq!(tester, expected); + } + } + } + } + + #[test] + fn test_remove() { + // This test checks that every single combination of tail position, length, and + // removal position is tested. Capacity 15 should be large enough to cover every case. + + let mut tester = VecDeque::with_capacity(15); + // can't guarantee we got 15, so have to get what we got. + // 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else + // this test isn't covering what it wants to + let cap = tester.capacity(); + + // len is the length *after* removal + for len in 0..cap - 1 { + // 0, 1, 2, .., len - 1 + let expected = (0..).take(len).collect::<VecDeque<_>>(); + for tail_pos in 0..cap { + for to_remove in 0..len + 1 { + tester.tail = tail_pos; + tester.head = tail_pos; + for i in 0..len { + if i == to_remove { + tester.push_back(1234); + } + tester.push_back(i); + } + if to_remove == len { + tester.push_back(1234); + } + tester.remove(to_remove); + assert!(tester.tail < tester.cap()); + assert!(tester.head < tester.cap()); + assert_eq!(tester, expected); + } + } + } + } + + #[test] + fn test_drain() { + let mut tester: VecDeque<usize> = VecDeque::with_capacity(7); + + let cap = tester.capacity(); + for len in 0..cap + 1 { + for tail in 0..cap + 1 { + for drain_start in 0..len + 1 { + for drain_end in drain_start..len + 1 { + tester.tail = tail; + tester.head = tail; + for i in 0..len { + tester.push_back(i); + } + + // Check that we drain the correct values + let drained: VecDeque<_> = tester.drain(drain_start..drain_end).collect(); + let drained_expected: VecDeque<_> = (drain_start..drain_end).collect(); + assert_eq!(drained, drained_expected); + + // We shouldn't have changed the capacity or made the + // head or tail out of bounds + assert_eq!(tester.capacity(), cap); + assert!(tester.tail < tester.cap()); + assert!(tester.head < tester.cap()); + + // We should see the correct values in the VecDeque + let expected: VecDeque<_> = (0..drain_start) + .chain(drain_end..len) + .collect(); + assert_eq!(expected, tester); + } + } + } + } + } + + #[test] + fn test_shrink_to_fit() { + // This test checks that every single combination of head and tail position, + // is tested. Capacity 15 should be large enough to cover every case. + + let mut tester = VecDeque::with_capacity(15); + // can't guarantee we got 15, so have to get what we got. + // 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else + // this test isn't covering what it wants to + let cap = tester.capacity(); + tester.reserve(63); + let max_cap = tester.capacity(); + + for len in 0..cap + 1 { + // 0, 1, 2, .., len - 1 + let expected = (0..).take(len).collect::<VecDeque<_>>(); + for tail_pos in 0..max_cap + 1 { + tester.tail = tail_pos; + tester.head = tail_pos; + tester.reserve(63); + for i in 0..len { + tester.push_back(i); + } + tester.shrink_to_fit(); + assert!(tester.capacity() <= cap); + assert!(tester.tail < tester.cap()); + assert!(tester.head < tester.cap()); + assert_eq!(tester, expected); + } + } + } + + #[test] + fn test_split_off() { + // This test checks that every single combination of tail position, length, and + // split position is tested. Capacity 15 should be large enough to cover every case. + + let mut tester = VecDeque::with_capacity(15); + // can't guarantee we got 15, so have to get what we got. + // 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else + // this test isn't covering what it wants to + let cap = tester.capacity(); + + // len is the length *before* splitting + for len in 0..cap { + // index to split at + for at in 0..len + 1 { + // 0, 1, 2, .., at - 1 (may be empty) + let expected_self = (0..).take(at).collect::<VecDeque<_>>(); + // at, at + 1, .., len - 1 (may be empty) + let expected_other = (at..).take(len - at).collect::<VecDeque<_>>(); + + for tail_pos in 0..cap { + tester.tail = tail_pos; + tester.head = tail_pos; + for i in 0..len { + tester.push_back(i); + } + let result = tester.split_off(at); + assert!(tester.tail < tester.cap()); + assert!(tester.head < tester.cap()); + assert!(result.tail < result.cap()); + assert!(result.head < result.cap()); + assert_eq!(tester, expected_self); + assert_eq!(result, expected_other); + } + } + } + } + + #[test] + fn test_from_vec() { + use super::super::vec::Vec; + for cap in 0..35 { + for len in 0..cap + 1 { + let mut vec = Vec::with_capacity(cap); + vec.extend(0..len); + + let vd = VecDeque::from(vec.clone()); + assert!(vd.cap().is_power_of_two()); + assert_eq!(vd.len(), vec.len()); + assert!(vd.into_iter().eq(vec)); + } + } + } + + #[test] + fn test_vec_from_vecdeque() { + use super::super::vec::Vec; + + fn create_vec_and_test_convert(cap: usize, offset: usize, len: usize) { + let mut vd = VecDeque::with_capacity(cap); + for _ in 0..offset { + vd.push_back(0); + vd.pop_front(); + } + vd.extend(0..len); + + let vec: Vec<_> = Vec::from(vd.clone()); + assert_eq!(vec.len(), vd.len()); + assert!(vec.into_iter().eq(vd)); + } + + for cap_pwr in 0..7 { + // Make capacity as a (2^x)-1, so that the ring size is 2^x + let cap = (2i32.pow(cap_pwr) - 1) as usize; + + // In these cases there is enough free space to solve it with copies + for len in 0..((cap + 1) / 2) { + // Test contiguous cases + for offset in 0..(cap - len) { + create_vec_and_test_convert(cap, offset, len) + } + + // Test cases where block at end of buffer is bigger than block at start + for offset in (cap - len)..(cap - (len / 2)) { + create_vec_and_test_convert(cap, offset, len) + } + + // Test cases where block at start of buffer is bigger than block at end + for offset in (cap - (len / 2))..cap { + create_vec_and_test_convert(cap, offset, len) + } + } + + // Now there's not (necessarily) space to straighten the ring with simple copies, + // the ring will use swapping when: + // (cap + 1 - offset) > (cap + 1 - len) && (len - (cap + 1 - offset)) > (cap + 1 - len)) + // right block size > free space && left block size > free space + for len in ((cap + 1) / 2)..cap { + // Test contiguous cases + for offset in 0..(cap - len) { + create_vec_and_test_convert(cap, offset, len) + } + + // Test cases where block at end of buffer is bigger than block at start + for offset in (cap - len)..(cap - (len / 2)) { + create_vec_and_test_convert(cap, offset, len) + } + + // Test cases where block at start of buffer is bigger than block at end + for offset in (cap - (len / 2))..cap { + create_vec_and_test_convert(cap, offset, len) + } + } + } + } + +} |