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lib.rs
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//! Crate that implements a semi-doubly linked list via a vector.
//!
//! See [`VecList`] for more information.
//!
//! # Features
//!
//! By default, this crate uses the Rust standard library. To disable this, disable the default
//! `no_std` feature. Without this feature, certain methods will not be available.
#![allow(unsafe_code)]
#![cfg_attr(coverage_nightly, feature(coverage_attribute))]
#![cfg_attr(not(any(feature = "std", test)), no_std)]
extern crate alloc;
use alloc::{collections::LinkedList, vec::Vec};
use core::{
cmp::Ordering,
fmt::{self, Debug, Formatter},
hash::{Hash, Hasher},
hint::unreachable_unchecked,
iter::{FromIterator, FusedIterator},
marker::PhantomData,
mem,
num::NonZeroUsize,
ops,
};
#[cfg(feature = "std")]
use std::collections::HashMap;
#[cfg(feature = "serde")]
mod serde;
/// Number type that's capable of representing [0, usize::MAX - 1]
#[repr(transparent)]
#[derive(Clone, Copy, Eq, Hash, Ord, PartialEq, PartialOrd)]
struct NonMaxUsize(NonZeroUsize);
impl Debug for NonMaxUsize {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
write!(f, "{}", self.get())
}
}
impl NonMaxUsize {
/// Convert an index to a usize
#[cfg_attr(mutants, mutants::skip)]
#[inline]
const fn get(&self) -> usize {
self.0.get() - 1
}
/// Create a new index from a usize, if `index` is `usize::MAX` then `None` is returned
#[inline]
const fn new(index: usize) -> Option<Self> {
match NonZeroUsize::new(index.wrapping_add(1)) {
Some(index) => Some(Self(index)),
None => None,
}
}
/// Create a new index from a usize, without checking if `index` is `usize::MAX`.
///
/// # Safety
///
/// `index` must not be `usize::MAX`
#[cfg(feature = "std")]
#[inline]
const unsafe fn new_unchecked(index: usize) -> Self {
Self(unsafe { NonZeroUsize::new_unchecked(index + 1) })
}
/// Add an unsigned integer to a index. Check for bound violation and return `None` if the result will be larger than or equal to `usize::MAX`
#[cfg(feature = "std")]
#[inline]
fn checked_add(&self, rhs: usize) -> Option<Self> {
self.0.checked_add(rhs).map(Self)
}
/// Subtract an unsigned integer from a index. Check for bound violation and return `None` if the result will be less than 0.
#[cfg(feature = "std")]
#[inline]
fn checked_sub(&self, rhs: usize) -> Option<Self> {
// Safety: `self` is less than `usize::MAX`, so `self - rhs` can only be less than `usize::MAX`
self
.get()
.checked_sub(rhs)
.map(|i| unsafe { Self::new_unchecked(i) })
}
#[cfg(feature = "std")]
#[inline]
const fn zero() -> Self {
Self(unsafe { NonZeroUsize::new_unchecked(1) })
}
}
impl PartialEq<usize> for NonMaxUsize {
fn eq(&self, other: &usize) -> bool {
self.get() == *other
}
}
impl PartialOrd<usize> for NonMaxUsize {
fn partial_cmp(&self, other: &usize) -> Option<Ordering> {
self.get().partial_cmp(other)
}
}
/// A semi-doubly linked list implemented with a vector.
///
/// This provides many of the benefits of an actual linked list with a few tradeoffs. First, due to the use of an
/// underlying vector, an individual insert operation may be O(n) due to allocating more space for the vector. However,
/// it is amortized O(1) and it avoids the frequent allocations that traditional linked lists suffer from.
///
/// Another tradeoff is that extending a traditional linked list with another list is O(1) but a vector based
/// implementation is O(n). Splicing has a similar disadvantage.
///
/// Lastly, the vector based implementation is likely to have better cache locality in general.
pub struct VecList<T> {
/// The backing storage for the list. This includes both used and unused indices.
entries: Vec<Entry<T>>,
/// The current generation of the list. This is used to avoid the ABA problem.
generation: u64,
/// The index of the head of the list.
head: Option<NonMaxUsize>,
/// The length of the list since we cannot rely on the length of [`VecList::entries`] because it includes unused
/// indices.
length: usize,
/// The index of the tail of the list.
tail: Option<NonMaxUsize>,
/// The index of the head of the vacant indices.
vacant_head: Option<NonMaxUsize>,
}
impl<T: Clone> Clone for VecList<T> {
fn clone(&self) -> Self {
Self {
entries: self.entries.clone(),
generation: self.generation,
head: self.head,
length: self.length,
tail: self.tail,
vacant_head: self.vacant_head,
}
}
fn clone_from(&mut self, source: &Self) {
self.entries.clone_from(&source.entries);
self.generation = source.generation;
self.head = source.head;
self.length = source.length;
self.tail = source.tail;
self.vacant_head = source.vacant_head;
}
}
impl<T> VecList<T> {
/// Returns an immutable reference to the value at the back of the list, if it exists.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert_eq!(list.back(), None);
///
/// list.push_back(0);
/// list.push_back(5);
/// assert_eq!(list.back(), Some(&5));
/// ```
#[must_use]
pub fn back(&self) -> Option<&T> {
let index = self.tail?.get();
match &self.entries[index] {
Entry::Occupied(entry) => Some(&entry.value),
_ => None,
}
}
/// Returns the index of the value at the back of the list, if it exists.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert_eq!(list.back_index(), None);
///
/// list.push_back(0);
/// let index = list.push_back(5);
/// assert_eq!(list.back_index(), Some(index));
/// ```
#[must_use]
pub fn back_index(&self) -> Option<Index<T>> {
let index = self.tail?;
let entry = self.entries[index.get()].occupied_ref();
let index = Index::new(index, entry.generation);
Some(index)
}
/// Returns a mutable reference to the value at the back of the list, if it exists.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert_eq!(list.back_mut(), None);
///
/// list.push_back(0);
/// list.push_back(5);
///
/// let mut back = list.back_mut().unwrap();
/// assert_eq!(back, &mut 5);
/// *back *= 2;
///
/// assert_eq!(list.back(), Some(&10));
/// ```
#[must_use]
pub fn back_mut(&mut self) -> Option<&mut T> {
let index = self.tail?.get();
match &mut self.entries[index] {
Entry::Occupied(entry) => Some(&mut entry.value),
_ => None,
}
}
/// Returns the capacity of the list.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let list: VecList<u32> = VecList::new();
/// assert_eq!(list.capacity(), 0);
///
/// let list: VecList<u32> = VecList::with_capacity(10);
/// assert_eq!(list.capacity(), 10);
/// ```
#[must_use]
pub fn capacity(&self) -> usize {
self.entries.capacity()
}
/// Removes all values from the list and invalidates all existing indices.
///
/// Complexity: O(n)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
///
/// list.push_back(5);
/// assert!(!list.is_empty());
///
/// list.clear();
/// assert!(list.is_empty());
/// ```
pub fn clear(&mut self) {
self.entries.clear();
self.generation = self.generation.wrapping_add(1);
self.head = None;
self.length = 0;
self.tail = None;
self.vacant_head = None;
}
/// Returns whether or not the list contains the given value.
///
/// Complexity: O(n)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert!(!list.contains(&0));
///
/// list.push_back(0);
/// assert!(list.contains(&0));
/// ```
#[must_use]
pub fn contains(&self, value: &T) -> bool
where
T: PartialEq,
{
self.iter().any(|entry| entry == value)
}
/// Creates a draining iterator that removes all values from the list and yields them in order.
///
/// All values are removed even if the iterator is only partially consumed or not consumed at all.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// list.push_back(0);
/// list.push_back(5);
///
/// {
/// let mut iter = list.drain();
/// assert_eq!(iter.next(), Some(0));
/// assert_eq!(iter.next(), Some(5));
/// assert_eq!(iter.next(), None);
/// }
///
/// println!("{}", list.len());
/// assert!(list.is_empty());
/// ```
pub fn drain(&mut self) -> Drain<'_, T> {
Drain {
head: self.head,
remaining: self.length,
tail: self.tail,
list: self,
}
}
/// Returns an immutable reference to the value at the front of the list, if it exists.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert_eq!(list.front(), None);
///
/// list.push_front(0);
/// list.push_front(5);
/// assert_eq!(list.front(), Some(&5));
/// ```
#[must_use]
pub fn front(&self) -> Option<&T> {
let index = self.head?.get();
match &self.entries[index] {
Entry::Occupied(entry) => Some(&entry.value),
_ => None,
}
}
/// Returns the index of the value at the front of the list, if it exists.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert_eq!(list.front_index(), None);
///
/// list.push_front(0);
/// let index = list.push_front(5);
/// assert_eq!(list.front_index(), Some(index));
/// ```
#[must_use]
pub fn front_index(&self) -> Option<Index<T>> {
let index = self.head?;
let entry = self.entries[index.get()].occupied_ref();
let index = Index::new(index, entry.generation);
Some(index)
}
/// Returns a mutable reference to the value at the front of the list, if it exists.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert_eq!(list.front_mut(), None);
///
/// list.push_front(0);
/// list.push_front(5);
///
/// let mut front = list.front_mut().unwrap();
/// assert_eq!(front, &mut 5);
/// *front *= 2;
///
/// assert_eq!(list.front(), Some(&10));
/// ```
#[must_use]
pub fn front_mut(&mut self) -> Option<&mut T> {
let index = self.head?.get();
match &mut self.entries[index] {
Entry::Occupied(entry) => Some(&mut entry.value),
_ => None,
}
}
/// Returns an immutable reference to the value at the given index.
///
/// If the index refers to an index not in the list anymore or if the index has been invalidated, then [`None`] will
/// be returned.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// let index = list.push_front(0);
/// assert_eq!(list.get(index), Some(&0));
///
/// let index = list.push_front(5);
/// assert_eq!(list.get(index), Some(&5));
/// ```
#[must_use]
pub fn get(&self, index: Index<T>) -> Option<&T> {
match self.entries.get(index.index())? {
Entry::Occupied(entry) if entry.generation == index.generation => Some(&entry.value),
_ => None,
}
}
/// Returns an immutable reference to the value at the given index.
///
/// Complexity: O(1)
///
/// # Safety
///
/// Caller needs to guarantee that the index is in bound, and has never been removed from the
/// list. This function does not perform generation checks. So if an element is removed then a
/// new element is added at the same index, then the returned reference will be to the new
/// element.
#[must_use]
pub unsafe fn get_unchecked(&self, index: Index<T>) -> &T {
match unsafe { self.entries.get_unchecked(index.index()) } {
Entry::Occupied(entry) => &entry.value,
_ => unsafe { unreachable_unchecked() },
}
}
/// Returns a mutable reference to the value at the given index.
///
/// If the index refers to an index not in the list anymore or if the index has been invalidated, then [`None`] will
/// be returned.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// let index = list.push_front(0);
/// let value = list.get_mut(index).unwrap();
/// *value = 100;
/// assert_eq!(list.get(index), Some(&100));
/// ```
#[must_use]
pub fn get_mut(&mut self, index: Index<T>) -> Option<&mut T> {
match self.entries.get_mut(index.index())? {
Entry::Occupied(entry) if entry.generation == index.generation => Some(&mut entry.value),
_ => None,
}
}
/// Returns an mutable reference to the value at the given index.
///
/// # Safety
///
/// Caller needs to guarantee that the index is in bound, and has never been removed from the list.
/// See also: [`VecList::get_unchecked`].
///
/// Complexity: O(1)
#[must_use]
pub unsafe fn get_unchecked_mut(&mut self, index: Index<T>) -> &mut T {
match unsafe { self.entries.get_unchecked_mut(index.index()) } {
Entry::Occupied(entry) => &mut entry.value,
_ => unsafe { unreachable_unchecked() },
}
}
/// Returns the index of the value next to the value at the given index.
///
/// If the index refers to an index not in the list anymore or if the index has been invalidated, then [`None`] will
/// be returned.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
///
/// let index_1 = list.push_back(0);
/// assert_eq!(list.get_next_index(index_1), None);
///
/// let index_2 = list.push_back(5);
/// assert_eq!(list.get_next_index(index_1), Some(index_2));
/// ```
#[must_use]
pub fn get_next_index(&self, index: Index<T>) -> Option<Index<T>> {
match self.entries.get(index.index())? {
Entry::Occupied(entry) if entry.generation == index.generation => {
let next_index = entry.next?;
let next_entry = self.entries[next_index.get()].occupied_ref();
Some(Index::new(next_index, next_entry.generation))
}
_ => None,
}
}
/// Returns the index of the value previous to the value at the given index.
///
/// If the index refers to an index not in the list anymore or if the index has been invalidated, then [`None`] will
/// be returned.
///
/// Complexity: O(1)
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
///
/// let index_1 = list.push_front(0);
/// assert_eq!(list.get_previous_index(index_1), None);
///
/// let index_2 = list.push_front(5);
/// assert_eq!(list.get_previous_index(index_1), Some(index_2));
/// ```
#[must_use]
pub fn get_previous_index(&self, index: Index<T>) -> Option<Index<T>> {
match self.entries.get(index.index())? {
Entry::Occupied(entry) if entry.generation == index.generation => {
let previous_index = entry.previous?;
let previous_entry = self.entries[previous_index.get()].occupied_ref();
Some(Index::new(previous_index, previous_entry.generation))
}
_ => None,
}
}
/// Connect the node at `index` to the node at `next`. If `index` is `None`, then the head will be
/// set to `next`; if `next` is `None`, then the tail will be set to `index`.
#[inline]
fn update_link(&mut self, index: Option<NonMaxUsize>, next: Option<NonMaxUsize>) {
if let Some(index) = index {
let entry = self.entries[index.get()].occupied_mut();
entry.next = next;
} else {
self.head = next
}
if let Some(next) = next {
let entry = self.entries[next.get()].occupied_mut();
entry.previous = index;
} else {
self.tail = index;
}
}
/// Move the node at `index` to after the node at `target`.
///
/// # Panics
///
/// Panics if either `index` or `target` is invalidated. Also panics if `index` is the same as `target`.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// let index_1 = list.push_back(0);
/// let index_2 = list.push_back(1);
/// let index_3 = list.push_back(2);
/// let index_4 = list.push_back(3);
///
/// list.move_after(index_1, index_3);
/// assert_eq!(list.iter().copied().collect::<Vec<_>>(), vec![1, 2, 0, 3]);
/// assert_eq!(list.iter().rev().copied().collect::<Vec<_>>(), vec![3, 0, 2, 1]);
/// ```
pub fn move_after(&mut self, index: Index<T>, target: Index<T>) {
let (previous_index, next_index) = match &self.entries[index.index()] {
Entry::Occupied(entry) if entry.generation == index.generation => {
(entry.previous, entry.next)
}
_ => panic!("expected occupied entry with correct generation at `index`"),
};
let target_next_index = match &self.entries[target.index()] {
Entry::Occupied(entry) if entry.generation == target.generation => entry.next,
_ => panic!("expected occupied entry with correct generation at `target`"),
};
if target.index == index.index {
panic!("cannot move after `index` itself");
}
if previous_index == Some(target.index) {
// Already in the right place
return;
}
self.update_link(previous_index, next_index);
self.update_link(Some(target.index), Some(index.index));
self.update_link(Some(index.index), target_next_index);
}
/// Move the node at `index` to before the node at `target`.
///
/// # Panics
///
/// Panics if either `index` or `target` is invalidated. Also panics if `index` is the same as `target`.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// let index_1 = list.push_back(0);
/// let index_2 = list.push_back(1);
/// let index_3 = list.push_back(2);
/// let index_4 = list.push_back(3);
///
/// list.move_before(index_1, index_3);
/// assert_eq!(list.iter().copied().collect::<Vec<_>>(), vec![1, 0, 2, 3]);
/// assert_eq!(list.iter().rev().copied().collect::<Vec<_>>(), vec![3, 2, 0, 1]);
/// ```
pub fn move_before(&mut self, index: Index<T>, target: Index<T>) {
let (previous_index, next_index) = match &self.entries[index.index()] {
Entry::Occupied(entry) if entry.generation == index.generation => {
(entry.previous, entry.next)
}
_ => panic!("expected occupied entry with correct generation at `index`"),
};
let target_previous_index = match &self.entries[target.index()] {
Entry::Occupied(entry) if entry.generation == target.generation => entry.previous,
_ => panic!("expected occupied entry with correct generation at `target`"),
};
if target.index == index.index {
panic!("cannot move before `index` itself");
}
if next_index == Some(target.index) {
// Already in the right place
return;
}
self.update_link(previous_index, next_index);
self.update_link(Some(index.index), Some(target.index));
self.update_link(target_previous_index, Some(index.index));
}
/// Creates an indices iterator which will yield all indices of the list in order.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// list.push_front(0);
/// list.push_front(5);
///
/// let mut indices = list.indices();
/// let index = indices.next().unwrap();
/// assert_eq!(list.get(index), Some(&5));
///
/// let index = indices.next().unwrap();
/// assert_eq!(list.get(index), Some(&0));
///
/// assert_eq!(indices.next(), None);
/// ```
#[must_use]
pub fn indices(&self) -> Indices<'_, T> {
Indices {
entries: &self.entries,
head: self.head,
remaining: self.length,
tail: self.tail,
}
}
/// Inserts the given value after the value at the given index.
///
/// The index of the newly inserted value will be returned.
///
/// Complexity: amortized O(1)
///
/// # Panics
///
/// Panics if the index refers to an index not in the list anymore or if the index has been invalidated. This is
/// enforced because this function will consume the value to be inserted, and if it cannot be inserted (due to the
/// index not being valid), then it will be lost.
///
/// Also panics if the new capacity overflows `usize`.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// list.push_front(0);
/// let index_1 = list.push_front(5);
/// list.push_front(10);
///
/// let index_2 = list.insert_after(index_1, 1000);
/// assert_eq!(list.get_next_index(index_1), Some(index_2));
/// ```
pub fn insert_after(&mut self, index: Index<T>, value: T) -> Index<T> {
let next_index = match &mut self.entries[index.index()] {
Entry::Occupied(entry) if entry.generation == index.generation => entry.next,
_ => panic!("expected occupied entry with correct generation"),
};
let new_index = self.insert_new(value, Some(index.index), next_index);
let entry = self.entries[index.index()].occupied_mut();
entry.next = Some(new_index);
if Some(index.index) == self.tail {
self.tail = Some(new_index);
}
if let Some(next_index) = next_index {
self.entries[next_index.get()].occupied_mut().previous = Some(new_index);
}
Index::new(new_index, self.generation)
}
/// Inserts the given value before the value at the given index.
///
/// The index of the newly inserted value will be returned.
///
/// Complexity: amortized O(1)
///
/// # Panics
///
/// Panics if the index refers to an index not in the list anymore or if the index has been invalidated. This is
/// enforced because this function will consume the value to be inserted, and if it cannot be inserted (due to the
/// index not being valid), then it will be lost.
///
/// Also panics if the new capacity overflows `usize`.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// list.push_front(0);
/// let index_1 = list.push_front(5);
/// list.push_front(10);
///
/// let index_2 = list.insert_before(index_1, 1000);
/// assert_eq!(list.get_previous_index(index_1), Some(index_2));
/// ```
pub fn insert_before(&mut self, index: Index<T>, value: T) -> Index<T> {
let previous_index = match &mut self.entries[index.index()] {
Entry::Occupied(entry) if entry.generation == index.generation => entry.previous,
_ => panic!("expected occupied entry with correct generation"),
};
let new_index = self.insert_new(value, previous_index, Some(index.index));
let entry = self.entries[index.index()].occupied_mut();
entry.previous = Some(new_index);
if Some(index.index) == self.head {
self.head = Some(new_index);
}
if let Some(previous_index) = previous_index {
self.entries[previous_index.get()].occupied_mut().next = Some(new_index);
}
Index::new(new_index, self.generation)
}
/// Inserts the given value into the list with the assumption that it is currently empty.
///
/// # Panics
///
/// Panics if the new capacity overflows `usize`.
fn insert_empty(&mut self, value: T) -> Index<T> {
let generation = self.generation;
let index = self.insert_new(value, None, None);
self.head = Some(index);
self.tail = Some(index);
Index::new(index, generation)
}
/// Inserts the given value into the list with its expected previous and next value indices.
///
/// # Panics
///
/// Panics if the new capacity overflows `usize`.
fn insert_new(
&mut self,
value: T,
previous: Option<NonMaxUsize>,
next: Option<NonMaxUsize>,
) -> NonMaxUsize {
self.length += 1;
if self.length == usize::max_value() {
panic!("reached maximum possible length");
}
match self.vacant_head {
Some(index) => {
self.vacant_head = self.entries[index.get()].vacant_ref().next;
self.entries[index.get()] =
Entry::Occupied(OccupiedEntry::new(self.generation, previous, next, value));
index
}
None => {
self.entries.push(Entry::Occupied(OccupiedEntry::new(
self.generation,
previous,
next,
value,
)));
NonMaxUsize::new(self.entries.len() - 1).unwrap()
}
}
}
/// Returns whether or not the list is empty.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert!(list.is_empty());
///
/// list.push_back(0);
/// assert!(!list.is_empty());
/// ```
#[must_use]
pub fn is_empty(&self) -> bool {
self.length == 0
}
/// Creates an iterator that yields immutable references to values in the list in order.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// list.push_back(0);
/// list.push_back(10);
/// list.push_back(200);
/// list.push_back(-10);
///
/// let mut iter = list.iter();
/// assert_eq!(iter.next(), Some(&0));
/// assert_eq!(iter.next(), Some(&10));
/// assert_eq!(iter.next(), Some(&200));
/// assert_eq!(iter.next(), Some(&-10));
/// assert_eq!(iter.next(), None);
/// ```
#[must_use]
pub fn iter(&self) -> Iter<'_, T> {
Iter {
entries: &self.entries,
head: self.head,
remaining: self.length,
tail: self.tail,
}
}
/// Creates an iterator that yields mutable references to values in the list in order.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// list.push_back(0);
/// list.push_back(10);
/// list.push_back(200);
/// list.push_back(-10);
///
/// let mut iter = list.iter_mut();
/// assert_eq!(iter.next(), Some(&mut 0));
/// assert_eq!(iter.next(), Some(&mut 10));
/// assert_eq!(iter.next(), Some(&mut 200));
/// assert_eq!(iter.next(), Some(&mut -10));
/// assert_eq!(iter.next(), None);
/// ```
#[must_use]
pub fn iter_mut(&mut self) -> IterMut<'_, T> {
IterMut {
entries: &mut self.entries,
head: self.head,
phantom: PhantomData,
remaining: self.length,
tail: self.tail,
}
}
/// Returns the number of values in the list.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// assert_eq!(list.len(), 0);
///
/// list.push_back(0);
/// list.push_back(1);
/// list.push_back(2);
/// assert_eq!(list.len(), 3);
/// ```
#[must_use]
pub fn len(&self) -> usize {
self.length
}
/// Creates a new list with no initial capacity.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// let index = list.push_back(0);
/// assert_eq!(list.get(index), Some(&0));
/// ```
#[must_use]
pub fn new() -> Self {
VecList::default()
}
/// Reorganizes the existing values to ensure maximum cache locality and shrinks the list such that the capacity is
/// exactly [`minimum_capacity`].
///
/// This function can be used to actually increase the capacity of the list.
///
/// Complexity: O(n)
///
/// # Panics
///
/// Panics if the given minimum capacity is less than the current length of the list.
///
/// # Examples
///
/// ```
/// use dlv_list::VecList;
///
/// let mut list = VecList::new();
/// let index_1 = list.push_back(5);
/// let index_2 = list.push_back(10);
/// let index_3 = list.push_front(100);
/// list.remove(index_1);
///
/// assert!(list.capacity() >= 3);
///
/// let mut map = list.pack_to(list.len() + 5);
/// assert_eq!(list.capacity(), 7);
/// assert_eq!(map.len(), 2);
///
/// let index_2 = map.remove(&index_2).unwrap();
/// let index_3 = map.remove(&index_3).unwrap();