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rust/src/liballoc/vec_deque.rs
Aidan Hobson Sayers 9b5859aea1 Remove all unstable placement features 
Closes #22181, #27779
2018-04-03 11:02:34 +02:00

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// 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::Bound::{Excluded, Included, Unbounded};
use core::ops::{Index, IndexMut, RangeBounds};
use core::ptr;
use core::ptr::NonNull;
use core::slice;
use core::hash::{Hash, Hasher};
use core::cmp;
use raw_vec::RawVec;
use super::allocator::CollectionAllocErr;
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.
///
/// 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().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 > old_cap {
self.buf.reserve_exact(used_cap, new_cap - used_cap);
unsafe {
self.handle_cap_increase(old_cap);
}
}
}
/// Tries to reserves the minimum capacity for exactly `additional` more elements to
/// be inserted in the given `VecDeque<T>`. After calling `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, or the allocator reports a failure, then an error
/// is returned.
///
/// # Examples
///
/// ```
/// #![feature(try_reserve)]
/// use std::collections::CollectionAllocErr;
/// use std::collections::VecDeque;
///
/// fn process_data(data: &[u32]) -> Result<VecDeque<u32>, CollectionAllocErr> {
/// 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 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<(), CollectionAllocErr> {
self.try_reserve(additional)
}
/// Tries to reserve capacity for at least `additional` more elements to be inserted
/// in the given `VecDeque<T>`. The collection may reserve more space to avoid
/// frequent reallocations. After calling `reserve`, capacity will be
/// greater than or equal to `self.len() + additional`. Does nothing if
/// capacity is already sufficient.
///
/// # Errors
///
/// If the capacity overflows, or the allocator reports a failure, then an error
/// is returned.
///
/// # Examples
///
/// ```
/// #![feature(try_reserve)]
/// use std::collections::CollectionAllocErr;
/// use std::collections::VecDeque;
///
/// fn process_data(data: &[u32]) -> Result<VecDeque<u32>, CollectionAllocErr> {
/// 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<(), CollectionAllocErr> {
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(CollectionAllocErr::CapacityOverflow)?;
if new_cap > old_cap {
self.buf.try_reserve_exact(used_cap, new_cap - used_cap)?;
unsafe {
self.handle_cap_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="0")]
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`, 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: RangeBounds<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: NonNull::from(&mut *self),
after_tail: drain_head,
after_head: head,
iter: Iter {
tail: drain_tail,
head: drain_head,
ring: unsafe { self.buffer_as_mut_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.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 `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]
#[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());
}
}
}
impl<T: Clone> VecDeque<T> {
/// 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) {
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(#26925) 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)) }
}
fn rfold<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 = back.iter().rfold(accum, &mut f);
front.iter().rfold(accum, &mut f)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T> ExactSizeIterator for Iter<'a, T> {
fn is_empty(&self) -> bool {
self.head == self.tail
}
}
#[stable(feature = "fused", since = "1.26.0")]
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 _))
}
}
fn rfold<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 = back.iter_mut().rfold(accum, &mut f);
front.iter_mut().rfold(accum, &mut f)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T> ExactSizeIterator for IterMut<'a, T> {
fn is_empty(&self) -> bool {
self.head == self.tail
}
}
#[stable(feature = "fused", since = "1.26.0")]
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()
}
}
#[stable(feature = "fused", since = "1.26.0")]
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: NonNull<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> {}
#[stable(feature = "fused", since = "1.26.0")]
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 `VecDeque` 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(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,
}
}
}
}
#[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
}
}
}
#[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)
}
}
}
}
}
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