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fuchsia / third_party / rust / 972fef232ec0dd7a3f42091aa6f36cd68aeb3eef / . / library / alloc / src / collections / linked_list.rs
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//! A doubly-linked list with owned nodes.
//!
//! The `LinkedList` allows pushing and popping elements at either end
//! in constant time.
//!
//! NOTE: It is almost always better to use [`Vec`] or [`VecDeque`] because
//! array-based containers are generally faster,
//! more memory efficient, and make better use of CPU cache.
//!
//! [`Vec`]: crate::vec::Vec
//! [`VecDeque`]: super::vec_deque::VecDeque
#![stable(feature = "rust1", since = "1.0.0")]
use core::cmp::Ordering;
use core::hash::{Hash, Hasher};
use core::iter::FusedIterator;
use core::marker::PhantomData;
use core::ptr::NonNull;
use core::{fmt, mem};
use super::SpecExtend;
use crate::alloc::{Allocator, Global};
use crate::boxed::Box;
#[cfg(test)]
mod tests;
/// A doubly-linked list with owned nodes.
///
/// The `LinkedList` allows pushing and popping elements at either end
/// in constant time.
///
/// A `LinkedList` with a known list of items can be initialized from an array:
/// ```
/// use std::collections::LinkedList;
///
/// let list = LinkedList::from([1, 2, 3]);
/// ```
///
/// NOTE: It is almost always better to use [`Vec`] or [`VecDeque`] because
/// array-based containers are generally faster,
/// more memory efficient, and make better use of CPU cache.
///
/// [`Vec`]: crate::vec::Vec
/// [`VecDeque`]: super::vec_deque::VecDeque
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(test), rustc_diagnostic_item = "LinkedList")]
#[rustc_insignificant_dtor]
pub struct LinkedList<
T,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> {
head: Option<NonNull<Node<T>>>,
tail: Option<NonNull<Node<T>>>,
len: usize,
alloc: A,
marker: PhantomData<Box<Node<T>, A>>,
}
struct Node<T> {
next: Option<NonNull<Node<T>>>,
prev: Option<NonNull<Node<T>>>,
element: T,
}
/// An iterator over the elements of a `LinkedList`.
///
/// This `struct` is created by [`LinkedList::iter()`]. See its
/// documentation for more.
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Iter<'a, T: 'a> {
head: Option<NonNull<Node<T>>>,
tail: Option<NonNull<Node<T>>>,
len: usize,
marker: PhantomData<&'a Node<T>>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("Iter")
.field(&*mem::ManuallyDrop::new(LinkedList {
head: self.head,
tail: self.tail,
len: self.len,
alloc: Global,
marker: PhantomData,
}))
.field(&self.len)
.finish()
}
}
// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> Clone for Iter<'_, T> {
fn clone(&self) -> Self {
Iter { ..*self }
}
}
/// A mutable iterator over the elements of a `LinkedList`.
///
/// This `struct` is created by [`LinkedList::iter_mut()`]. See its
/// documentation for more.
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct IterMut<'a, T: 'a> {
head: Option<NonNull<Node<T>>>,
tail: Option<NonNull<Node<T>>>,
len: usize,
marker: PhantomData<&'a mut Node<T>>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("IterMut")
.field(&*mem::ManuallyDrop::new(LinkedList {
head: self.head,
tail: self.tail,
len: self.len,
alloc: Global,
marker: PhantomData,
}))
.field(&self.len)
.finish()
}
}
/// An owning iterator over the elements of a `LinkedList`.
///
/// This `struct` is created by the [`into_iter`] method on [`LinkedList`]
/// (provided by the [`IntoIterator`] trait). See its documentation for more.
///
/// [`into_iter`]: LinkedList::into_iter
#[derive(Clone)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct IntoIter<
T,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> {
list: LinkedList<T, A>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("IntoIter").field(&self.list).finish()
}
}
impl<T> Node<T> {
fn new(element: T) -> Self {
Node { next: None, prev: None, element }
}
fn into_element<A: Allocator>(self: Box<Self, A>) -> T {
self.element
}
}
// private methods
impl<T, A: Allocator> LinkedList<T, A> {
/// Adds the given node to the front of the list.
///
/// # Safety
/// `node` must point to a valid node that was boxed and leaked using the list's allocator.
/// This method takes ownership of the node, so the pointer should not be used again.
#[inline]
unsafe fn push_front_node(&mut self, node: NonNull<Node<T>>) {
// This method takes care not to create mutable references to whole nodes,
// to maintain validity of aliasing pointers into `element`.
unsafe {
(*node.as_ptr()).next = self.head;
(*node.as_ptr()).prev = None;
let node = Some(node);
match self.head {
None => self.tail = node,
// Not creating new mutable (unique!) references overlapping `element`.
Some(head) => (*head.as_ptr()).prev = node,
}
self.head = node;
self.len += 1;
}
}
/// Removes and returns the node at the front of the list.
#[inline]
fn pop_front_node(&mut self) -> Option<Box<Node<T>, &A>> {
// This method takes care not to create mutable references to whole nodes,
// to maintain validity of aliasing pointers into `element`.
self.head.map(|node| unsafe {
let node = Box::from_raw_in(node.as_ptr(), &self.alloc);
self.head = node.next;
match self.head {
None => self.tail = None,
// Not creating new mutable (unique!) references overlapping `element`.
Some(head) => (*head.as_ptr()).prev = None,
}
self.len -= 1;
node
})
}
/// Adds the given node to the back of the list.
///
/// # Safety
/// `node` must point to a valid node that was boxed and leaked using the list's allocator.
/// This method takes ownership of the node, so the pointer should not be used again.
#[inline]
unsafe fn push_back_node(&mut self, node: NonNull<Node<T>>) {
// This method takes care not to create mutable references to whole nodes,
// to maintain validity of aliasing pointers into `element`.
unsafe {
(*node.as_ptr()).next = None;
(*node.as_ptr()).prev = self.tail;
let node = Some(node);
match self.tail {
None => self.head = node,
// Not creating new mutable (unique!) references overlapping `element`.
Some(tail) => (*tail.as_ptr()).next = node,
}
self.tail = node;
self.len += 1;
}
}
/// Removes and returns the node at the back of the list.
#[inline]
fn pop_back_node(&mut self) -> Option<Box<Node<T>, &A>> {
// This method takes care not to create mutable references to whole nodes,
// to maintain validity of aliasing pointers into `element`.
self.tail.map(|node| unsafe {
let node = Box::from_raw_in(node.as_ptr(), &self.alloc);
self.tail = node.prev;
match self.tail {
None => self.head = None,
// Not creating new mutable (unique!) references overlapping `element`.
Some(tail) => (*tail.as_ptr()).next = None,
}
self.len -= 1;
node
})
}
/// Unlinks the specified node from the current list.
///
/// Warning: this will not check that the provided node belongs to the current list.
///
/// This method takes care not to create mutable references to `element`, to
/// maintain validity of aliasing pointers.
#[inline]
unsafe fn unlink_node(&mut self, mut node: NonNull<Node<T>>) {
let node = unsafe { node.as_mut() }; // this one is ours now, we can create an &mut.
// Not creating new mutable (unique!) references overlapping `element`.
match node.prev {
Some(prev) => unsafe { (*prev.as_ptr()).next = node.next },
// this node is the head node
None => self.head = node.next,
};
match node.next {
Some(next) => unsafe { (*next.as_ptr()).prev = node.prev },
// this node is the tail node
None => self.tail = node.prev,
};
self.len -= 1;
}
/// Splices a series of nodes between two existing nodes.
///
/// Warning: this will not check that the provided node belongs to the two existing lists.
#[inline]
unsafe fn splice_nodes(
&mut self,
existing_prev: Option<NonNull<Node<T>>>,
existing_next: Option<NonNull<Node<T>>>,
mut splice_start: NonNull<Node<T>>,
mut splice_end: NonNull<Node<T>>,
splice_length: usize,
) {
// This method takes care not to create multiple mutable references to whole nodes at the same time,
// to maintain validity of aliasing pointers into `element`.
if let Some(mut existing_prev) = existing_prev {
unsafe {
existing_prev.as_mut().next = Some(splice_start);
}
} else {
self.head = Some(splice_start);
}
if let Some(mut existing_next) = existing_next {
unsafe {
existing_next.as_mut().prev = Some(splice_end);
}
} else {
self.tail = Some(splice_end);
}
unsafe {
splice_start.as_mut().prev = existing_prev;
splice_end.as_mut().next = existing_next;
}
self.len += splice_length;
}
/// Detaches all nodes from a linked list as a series of nodes.
#[inline]
fn detach_all_nodes(mut self) -> Option<(NonNull<Node<T>>, NonNull<Node<T>>, usize)> {
let head = self.head.take();
let tail = self.tail.take();
let len = mem::replace(&mut self.len, 0);
if let Some(head) = head {
// SAFETY: In a LinkedList, either both the head and tail are None because
// the list is empty, or both head and tail are Some because the list is populated.
// Since we have verified the head is Some, we are sure the tail is Some too.
let tail = unsafe { tail.unwrap_unchecked() };
Some((head, tail, len))
} else {
None
}
}
#[inline]
unsafe fn split_off_before_node(
&mut self,
split_node: Option<NonNull<Node<T>>>,
at: usize,
) -> Self
where
A: Clone,
{
// The split node is the new head node of the second part
if let Some(mut split_node) = split_node {
let first_part_head;
let first_part_tail;
unsafe {
first_part_tail = split_node.as_mut().prev.take();
}
if let Some(mut tail) = first_part_tail {
unsafe {
tail.as_mut().next = None;
}
first_part_head = self.head;
} else {
first_part_head = None;
}
let first_part = LinkedList {
head: first_part_head,
tail: first_part_tail,
len: at,
alloc: self.alloc.clone(),
marker: PhantomData,
};
// Fix the head ptr of the second part
self.head = Some(split_node);
self.len = self.len - at;
first_part
} else {
mem::replace(self, LinkedList::new_in(self.alloc.clone()))
}
}
#[inline]
unsafe fn split_off_after_node(
&mut self,
split_node: Option<NonNull<Node<T>>>,
at: usize,
) -> Self
where
A: Clone,
{
// The split node is the new tail node of the first part and owns
// the head of the second part.
if let Some(mut split_node) = split_node {
let second_part_head;
let second_part_tail;
unsafe {
second_part_head = split_node.as_mut().next.take();
}
if let Some(mut head) = second_part_head {
unsafe {
head.as_mut().prev = None;
}
second_part_tail = self.tail;
} else {
second_part_tail = None;
}
let second_part = LinkedList {
head: second_part_head,
tail: second_part_tail,
len: self.len - at,
alloc: self.alloc.clone(),
marker: PhantomData,
};
// Fix the tail ptr of the first part
self.tail = Some(split_node);
self.len = at;
second_part
} else {
mem::replace(self, LinkedList::new_in(self.alloc.clone()))
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> Default for LinkedList<T> {
/// Creates an empty `LinkedList<T>`.
#[inline]
fn default() -> Self {
Self::new()
}
}
impl<T> LinkedList<T> {
/// Creates an empty `LinkedList`.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let list: LinkedList<u32> = LinkedList::new();
/// ```
#[inline]
#[rustc_const_stable(feature = "const_linked_list_new", since = "1.39.0")]
#[stable(feature = "rust1", since = "1.0.0")]
#[must_use]
pub const fn new() -> Self {
LinkedList { head: None, tail: None, len: 0, alloc: Global, marker: PhantomData }
}
/// Moves all elements from `other` to the end of the list.
///
/// This reuses all the nodes from `other` and moves them into `self`. After
/// this operation, `other` becomes empty.
///
/// This operation should compute in *O*(1) time and *O*(1) memory.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut list1 = LinkedList::new();
/// list1.push_back('a');
///
/// let mut list2 = LinkedList::new();
/// list2.push_back('b');
/// list2.push_back('c');
///
/// list1.append(&mut list2);
///
/// let mut iter = list1.iter();
/// assert_eq!(iter.next(), Some(&'a'));
/// assert_eq!(iter.next(), Some(&'b'));
/// assert_eq!(iter.next(), Some(&'c'));
/// assert!(iter.next().is_none());
///
/// assert!(list2.is_empty());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn append(&mut self, other: &mut Self) {
match self.tail {
None => mem::swap(self, other),
Some(mut tail) => {
// `as_mut` is okay here because we have exclusive access to the entirety
// of both lists.
if let Some(mut other_head) = other.head.take() {
unsafe {
tail.as_mut().next = Some(other_head);
other_head.as_mut().prev = Some(tail);
}
self.tail = other.tail.take();
self.len += mem::replace(&mut other.len, 0);
}
}
}
}
}
impl<T, A: Allocator> LinkedList<T, A> {
/// Constructs an empty `LinkedList<T, A>`.
///
/// # Examples
///
/// ```
/// #![feature(allocator_api)]
///
/// use std::alloc::System;
/// use std::collections::LinkedList;
///
/// let list: LinkedList<u32, _> = LinkedList::new_in(System);
/// ```
#[inline]
#[unstable(feature = "allocator_api", issue = "32838")]
pub const fn new_in(alloc: A) -> Self {
LinkedList { head: None, tail: None, len: 0, alloc, marker: PhantomData }
}
/// Provides a forward iterator.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut list: LinkedList<u32> = LinkedList::new();
///
/// list.push_back(0);
/// list.push_back(1);
/// list.push_back(2);
///
/// let mut iter = list.iter();
/// assert_eq!(iter.next(), Some(&0));
/// assert_eq!(iter.next(), Some(&1));
/// assert_eq!(iter.next(), Some(&2));
/// assert_eq!(iter.next(), None);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter(&self) -> Iter<'_, T> {
Iter { head: self.head, tail: self.tail, len: self.len, marker: PhantomData }
}
/// Provides a forward iterator with mutable references.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut list: LinkedList<u32> = LinkedList::new();
///
/// list.push_back(0);
/// list.push_back(1);
/// list.push_back(2);
///
/// for element in list.iter_mut() {
/// *element += 10;
/// }
///
/// let mut iter = list.iter();
/// assert_eq!(iter.next(), Some(&10));
/// assert_eq!(iter.next(), Some(&11));
/// assert_eq!(iter.next(), Some(&12));
/// assert_eq!(iter.next(), None);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter_mut(&mut self) -> IterMut<'_, T> {
IterMut { head: self.head, tail: self.tail, len: self.len, marker: PhantomData }
}
/// Provides a cursor at the front element.
///
/// The cursor is pointing to the "ghost" non-element if the list is empty.
#[inline]
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn cursor_front(&self) -> Cursor<'_, T, A> {
Cursor { index: 0, current: self.head, list: self }
}
/// Provides a cursor with editing operations at the front element.
///
/// The cursor is pointing to the "ghost" non-element if the list is empty.
#[inline]
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn cursor_front_mut(&mut self) -> CursorMut<'_, T, A> {
CursorMut { index: 0, current: self.head, list: self }
}
/// Provides a cursor at the back element.
///
/// The cursor is pointing to the "ghost" non-element if the list is empty.
#[inline]
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn cursor_back(&self) -> Cursor<'_, T, A> {
Cursor { index: self.len.checked_sub(1).unwrap_or(0), current: self.tail, list: self }
}
/// Provides a cursor with editing operations at the back element.
///
/// The cursor is pointing to the "ghost" non-element if the list is empty.
#[inline]
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn cursor_back_mut(&mut self) -> CursorMut<'_, T, A> {
CursorMut { index: self.len.checked_sub(1).unwrap_or(0), current: self.tail, list: self }
}
/// Returns `true` if the `LinkedList` is empty.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut dl = LinkedList::new();
/// assert!(dl.is_empty());
///
/// dl.push_front("foo");
/// assert!(!dl.is_empty());
/// ```
#[inline]
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn is_empty(&self) -> bool {
self.head.is_none()
}
/// Returns the length of the `LinkedList`.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut dl = LinkedList::new();
///
/// dl.push_front(2);
/// assert_eq!(dl.len(), 1);
///
/// dl.push_front(1);
/// assert_eq!(dl.len(), 2);
///
/// dl.push_back(3);
/// assert_eq!(dl.len(), 3);
/// ```
#[inline]
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_confusables("length", "size")]
pub fn len(&self) -> usize {
self.len
}
/// Removes all elements from the `LinkedList`.
///
/// This operation should compute in *O*(*n*) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut dl = LinkedList::new();
///
/// dl.push_front(2);
/// dl.push_front(1);
/// assert_eq!(dl.len(), 2);
/// assert_eq!(dl.front(), Some(&1));
///
/// dl.clear();
/// assert_eq!(dl.len(), 0);
/// assert_eq!(dl.front(), None);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn clear(&mut self) {
// We need to drop the nodes while keeping self.alloc
// We can do this by moving (head, tail, len) into a new list that borrows self.alloc
drop(LinkedList {
head: self.head.take(),
tail: self.tail.take(),
len: mem::take(&mut self.len),
alloc: &self.alloc,
marker: PhantomData,
});
}
/// Returns `true` if the `LinkedList` contains an element equal to the
/// given value.
///
/// This operation should compute linearly in *O*(*n*) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut list: LinkedList<u32> = LinkedList::new();
///
/// list.push_back(0);
/// list.push_back(1);
/// list.push_back(2);
///
/// assert_eq!(list.contains(&0), true);
/// assert_eq!(list.contains(&10), false);
/// ```
#[stable(feature = "linked_list_contains", since = "1.12.0")]
pub fn contains(&self, x: &T) -> bool
where
T: PartialEq<T>,
{
self.iter().any(|e| e == x)
}
/// Provides a reference to the front element, or `None` if the list is
/// empty.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut dl = LinkedList::new();
/// assert_eq!(dl.front(), None);
///
/// dl.push_front(1);
/// assert_eq!(dl.front(), Some(&1));
/// ```
#[inline]
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_confusables("first")]
pub fn front(&self) -> Option<&T> {
unsafe { self.head.as_ref().map(|node| &node.as_ref().element) }
}
/// Provides a mutable reference to the front element, or `None` if the list
/// is empty.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut dl = LinkedList::new();
/// assert_eq!(dl.front(), None);
///
/// dl.push_front(1);
/// assert_eq!(dl.front(), Some(&1));
///
/// match dl.front_mut() {
/// None => {},
/// Some(x) => *x = 5,
/// }
/// assert_eq!(dl.front(), Some(&5));
/// ```
#[inline]
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn front_mut(&mut self) -> Option<&mut T> {
unsafe { self.head.as_mut().map(|node| &mut node.as_mut().element) }
}
/// Provides a reference to the back element, or `None` if the list is
/// empty.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut dl = LinkedList::new();
/// assert_eq!(dl.back(), None);
///
/// dl.push_back(1);
/// assert_eq!(dl.back(), Some(&1));
/// ```
#[inline]
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn back(&self) -> Option<&T> {
unsafe { self.tail.as_ref().map(|node| &node.as_ref().element) }
}
/// Provides a mutable reference to the back element, or `None` if the list
/// is empty.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut dl = LinkedList::new();
/// assert_eq!(dl.back(), None);
///
/// dl.push_back(1);
/// assert_eq!(dl.back(), Some(&1));
///
/// match dl.back_mut() {
/// None => {},
/// Some(x) => *x = 5,
/// }
/// assert_eq!(dl.back(), Some(&5));
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn back_mut(&mut self) -> Option<&mut T> {
unsafe { self.tail.as_mut().map(|node| &mut node.as_mut().element) }
}
/// Adds an element first in the list.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut dl = LinkedList::new();
///
/// dl.push_front(2);
/// assert_eq!(dl.front().unwrap(), &2);
///
/// dl.push_front(1);
/// assert_eq!(dl.front().unwrap(), &1);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn push_front(&mut self, elt: T) {
let node = Box::new_in(Node::new(elt), &self.alloc);
let node_ptr = NonNull::from(Box::leak(node));
// SAFETY: node_ptr is a unique pointer to a node we boxed with self.alloc and leaked
unsafe {
self.push_front_node(node_ptr);
}
}
/// Removes the first element and returns it, or `None` if the list is
/// empty.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut d = LinkedList::new();
/// assert_eq!(d.pop_front(), None);
///
/// d.push_front(1);
/// d.push_front(3);
/// assert_eq!(d.pop_front(), Some(3));
/// assert_eq!(d.pop_front(), Some(1));
/// assert_eq!(d.pop_front(), None);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn pop_front(&mut self) -> Option<T> {
self.pop_front_node().map(Node::into_element)
}
/// Appends an element to the back of a list.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut d = LinkedList::new();
/// d.push_back(1);
/// d.push_back(3);
/// assert_eq!(3, *d.back().unwrap());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_confusables("push", "append")]
pub fn push_back(&mut self, elt: T) {
let node = Box::new_in(Node::new(elt), &self.alloc);
let node_ptr = NonNull::from(Box::leak(node));
// SAFETY: node_ptr is a unique pointer to a node we boxed with self.alloc and leaked
unsafe {
self.push_back_node(node_ptr);
}
}
/// Removes the last element from a list and returns it, or `None` if
/// it is empty.
///
/// This operation should compute in *O*(1) time.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut d = LinkedList::new();
/// assert_eq!(d.pop_back(), None);
/// d.push_back(1);
/// d.push_back(3);
/// assert_eq!(d.pop_back(), Some(3));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn pop_back(&mut self) -> Option<T> {
self.pop_back_node().map(Node::into_element)
}
/// Splits the list into two at the given index. Returns everything after the given index,
/// including the index.
///
/// This operation should compute in *O*(*n*) time.
///
/// # Panics
///
/// Panics if `at > len`.
///
/// # Examples
///
/// ```
/// use std::collections::LinkedList;
///
/// let mut d = LinkedList::new();
///
/// d.push_front(1);
/// d.push_front(2);
/// d.push_front(3);
///
/// let mut split = d.split_off(2);
///
/// assert_eq!(split.pop_front(), Some(1));
/// assert_eq!(split.pop_front(), None);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn split_off(&mut self, at: usize) -> LinkedList<T, A>
where
A: Clone,
{
let len = self.len();
assert!(at <= len, "Cannot split off at a nonexistent index");
if at == 0 {
return mem::replace(self, Self::new_in(self.alloc.clone()));
} else if at == len {
return Self::new_in(self.alloc.clone());
}
// Below, we iterate towards the `i-1`th node, either from the start or the end,
// depending on which would be faster.
let split_node = if at - 1 <= len - 1 - (at - 1) {
let mut iter = self.iter_mut();
// instead of skipping using .skip() (which creates a new struct),
// we skip manually so we can access the head field without
// depending on implementation details of Skip
for _ in 0..at - 1 {
iter.next();
}
iter.head
} else {
// better off starting from the end
let mut iter = self.iter_mut();
for _ in 0..len - 1 - (at - 1) {
iter.next_back();
}
iter.tail
};
unsafe { self.split_off_after_node(split_node, at) }
}
/// Removes the element at the given index and returns it.
///
/// This operation should compute in *O*(*n*) time.
///
/// # Panics
/// Panics if at >= len
///
/// # Examples
///
/// ```
/// #![feature(linked_list_remove)]
/// use std::collections::LinkedList;
///
/// let mut d = LinkedList::new();
///
/// d.push_front(1);
/// d.push_front(2);
/// d.push_front(3);
///
/// assert_eq!(d.remove(1), 2);
/// assert_eq!(d.remove(0), 3);
/// assert_eq!(d.remove(0), 1);
/// ```
#[unstable(feature = "linked_list_remove", issue = "69210")]
#[rustc_confusables("delete", "take")]
pub fn remove(&mut self, at: usize) -> T {
let len = self.len();
assert!(at < len, "Cannot remove at an index outside of the list bounds");
// Below, we iterate towards the node at the given index, either from
// the start or the end, depending on which would be faster.
let offset_from_end = len - at - 1;
if at <= offset_from_end {
let mut cursor = self.cursor_front_mut();
for _ in 0..at {
cursor.move_next();
}
cursor.remove_current().unwrap()
} else {
let mut cursor = self.cursor_back_mut();
for _ in 0..offset_from_end {
cursor.move_prev();
}
cursor.remove_current().unwrap()
}
}
/// Retains only the elements specified by the predicate.
///
/// In other words, remove all elements `e` for which `f(&e)` returns false.
/// This method operates in place, visiting each element exactly once in the
/// original order, and preserves the order of the retained elements.
///
/// # Examples
///
/// ```
/// #![feature(linked_list_retain)]
/// use std::collections::LinkedList;
///
/// let mut d = LinkedList::new();
///
/// d.push_front(1);
/// d.push_front(2);
/// d.push_front(3);
///
/// d.retain(|&x| x % 2 == 0);
///
/// assert_eq!(d.pop_front(), Some(2));
/// assert_eq!(d.pop_front(), None);
/// ```
///
/// Because the elements are visited exactly once in the original order,
/// external state may be used to decide which elements to keep.
///
/// ```
/// #![feature(linked_list_retain)]
/// use std::collections::LinkedList;
///
/// let mut d = LinkedList::new();
///
/// d.push_front(1);
/// d.push_front(2);
/// d.push_front(3);
///
/// let keep = [false, true, false];
/// let mut iter = keep.iter();
/// d.retain(|_| *iter.next().unwrap());
/// assert_eq!(d.pop_front(), Some(2));
/// assert_eq!(d.pop_front(), None);
/// ```
#[unstable(feature = "linked_list_retain", issue = "114135")]
pub fn retain<F>(&mut self, mut f: F)
where
F: FnMut(&T) -> bool,
{
self.retain_mut(|elem| f(elem));
}
/// Retains only the elements specified by the predicate.
///
/// In other words, remove all elements `e` for which `f(&mut e)` returns false.
/// This method operates in place, visiting each element exactly once in the
/// original order, and preserves the order of the retained elements.
///
/// # Examples
///
/// ```
/// #![feature(linked_list_retain)]
/// use std::collections::LinkedList;
///
/// let mut d = LinkedList::new();
///
/// d.push_front(1);
/// d.push_front(2);
/// d.push_front(3);
///
/// d.retain_mut(|x| if *x % 2 == 0 {
/// *x += 1;
/// true
/// } else {
/// false
/// });
/// assert_eq!(d.pop_front(), Some(3));
/// assert_eq!(d.pop_front(), None);
/// ```
#[unstable(feature = "linked_list_retain", issue = "114135")]
pub fn retain_mut<F>(&mut self, mut f: F)
where
F: FnMut(&mut T) -> bool,
{
let mut cursor = self.cursor_front_mut();
while let Some(node) = cursor.current() {
if !f(node) {
cursor.remove_current().unwrap();
} else {
cursor.move_next();
}
}
}
/// Creates an iterator which uses a closure to determine if an element should be removed.
///
/// If the closure returns true, then the element is removed and yielded.
/// If the closure returns false, the element will remain in the list and will not be yielded
/// by the iterator.
///
/// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
/// or the iteration short-circuits, then the remaining elements will be retained.
/// Use `extract_if().for_each(drop)` if you do not need the returned iterator.
///
/// Note that `extract_if` lets you mutate every element in the filter closure, regardless of
/// whether you choose to keep or remove it.
///
/// # Examples
///
/// Splitting a list into evens and odds, reusing the original list:
///
/// ```
/// #![feature(extract_if)]
/// use std::collections::LinkedList;
///
/// let mut numbers: LinkedList<u32> = LinkedList::new();
/// numbers.extend(&[1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15]);
///
/// let evens = numbers.extract_if(|x| *x % 2 == 0).collect::<LinkedList<_>>();
/// let odds = numbers;
///
/// assert_eq!(evens.into_iter().collect::<Vec<_>>(), vec![2, 4, 6, 8, 14]);
/// assert_eq!(odds.into_iter().collect::<Vec<_>>(), vec![1, 3, 5, 9, 11, 13, 15]);
/// ```
#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
pub fn extract_if<F>(&mut self, filter: F) -> ExtractIf<'_, T, F, A>
where
F: FnMut(&mut T) -> bool,
{
// avoid borrow issues.
let it = self.head;
let old_len = self.len;
ExtractIf { list: self, it, pred: filter, idx: 0, old_len }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<#[may_dangle] T, A: Allocator> Drop for LinkedList<T, A> {
fn drop(&mut self) {
struct DropGuard<'a, T, A: Allocator>(&'a mut LinkedList<T, A>);
impl<'a, T, A: Allocator> Drop for DropGuard<'a, T, A> {
fn drop(&mut self) {
// Continue the same loop we do below. This only runs when a destructor has
// panicked. If another one panics this will abort.
while self.0.pop_front_node().is_some() {}
}
}
// Wrap self so that if a destructor panics, we can try to keep looping
let guard = DropGuard(self);
while guard.0.pop_front_node().is_some() {}
mem::forget(guard);
}
}
#[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.len == 0 {
None
} else {
self.head.map(|node| unsafe {
// Need an unbound lifetime to get 'a
let node = &*node.as_ptr();
self.len -= 1;
self.head = node.next;
&node.element
})
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
(self.len, Some(self.len))
}
#[inline]
fn last(mut self) -> Option<&'a T> {
self.next_back()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
#[inline]
fn next_back(&mut self) -> Option<&'a T> {
if self.len == 0 {
None
} else {
self.tail.map(|node| unsafe {
// Need an unbound lifetime to get 'a
let node = &*node.as_ptr();
self.len -= 1;
self.tail = node.prev;
&node.element
})
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> ExactSizeIterator for Iter<'_, T> {}
#[stable(feature = "fused", since = "1.26.0")]
impl<T> FusedIterator for Iter<'_, T> {}
#[stable(feature = "default_iters", since = "1.70.0")]
impl<T> Default for Iter<'_, T> {
/// Creates an empty `linked_list::Iter`.
///
/// ```
/// # use std::collections::linked_list;
/// let iter: linked_list::Iter<'_, u8> = Default::default();
/// assert_eq!(iter.len(), 0);
/// ```
fn default() -> Self {
Iter { head: None, tail: None, len: 0, marker: Default::default() }
}
}
#[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.len == 0 {
None
} else {
self.head.map(|node| unsafe {
// Need an unbound lifetime to get 'a
let node = &mut *node.as_ptr();
self.len -= 1;
self.head = node.next;
&mut node.element
})
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
(self.len, Some(self.len))
}
#[inline]
fn last(mut self) -> Option<&'a mut T> {
self.next_back()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T> DoubleEndedIterator for IterMut<'a, T> {
#[inline]
fn next_back(&mut self) -> Option<&'a mut T> {
if self.len == 0 {
None
} else {
self.tail.map(|node| unsafe {
// Need an unbound lifetime to get 'a
let node = &mut *node.as_ptr();
self.len -= 1;
self.tail = node.prev;
&mut node.element
})
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> ExactSizeIterator for IterMut<'_, T> {}
#[stable(feature = "fused", since = "1.26.0")]
impl<T> FusedIterator for IterMut<'_, T> {}
#[stable(feature = "default_iters", since = "1.70.0")]
impl<T> Default for IterMut<'_, T> {
fn default() -> Self {
IterMut { head: None, tail: None, len: 0, marker: Default::default() }
}
}
/// A cursor over a `LinkedList`.
///
/// A `Cursor` is like an iterator, except that it can freely seek back-and-forth.
///
/// Cursors always rest between two elements in the list, and index in a logically circular way.
/// To accommodate this, there is a "ghost" non-element that yields `None` between the head and
/// tail of the list.
///
/// When created, cursors start at the front of the list, or the "ghost" non-element if the list is empty.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub struct Cursor<
'a,
T: 'a,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> {
index: usize,
current: Option<NonNull<Node<T>>>,
list: &'a LinkedList<T, A>,
}
#[unstable(feature = "linked_list_cursors", issue = "58533")]
impl<T, A: Allocator> Clone for Cursor<'_, T, A> {
fn clone(&self) -> Self {
let Cursor { index, current, list } = *self;
Cursor { index, current, list }
}
}
#[unstable(feature = "linked_list_cursors", issue = "58533")]
impl<T: fmt::Debug, A: Allocator> fmt::Debug for Cursor<'_, T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("Cursor").field(&self.list).field(&self.index()).finish()
}
}
/// A cursor over a `LinkedList` with editing operations.
///
/// A `Cursor` is like an iterator, except that it can freely seek back-and-forth, and can
/// safely mutate the list during iteration. This is because the lifetime of its yielded
/// references is tied to its own lifetime, instead of just the underlying list. This means
/// cursors cannot yield multiple elements at once.
///
/// Cursors always rest between two elements in the list, and index in a logically circular way.
/// To accommodate this, there is a "ghost" non-element that yields `None` between the head and
/// tail of the list.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub struct CursorMut<
'a,
T: 'a,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> {
index: usize,
current: Option<NonNull<Node<T>>>,
list: &'a mut LinkedList<T, A>,
}
#[unstable(feature = "linked_list_cursors", issue = "58533")]
impl<T: fmt::Debug, A: Allocator> fmt::Debug for CursorMut<'_, T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("CursorMut").field(&self.list).field(&self.index()).finish()
}
}
impl<'a, T, A: Allocator> Cursor<'a, T, A> {
/// Returns the cursor position index within the `LinkedList`.
///
/// This returns `None` if the cursor is currently pointing to the
/// "ghost" non-element.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn index(&self) -> Option<usize> {
let _ = self.current?;
Some(self.index)
}
/// Moves the cursor to the next element of the `LinkedList`.
///
/// If the cursor is pointing to the "ghost" non-element then this will move it to
/// the first element of the `LinkedList`. If it is pointing to the last
/// element of the `LinkedList` then this will move it to the "ghost" non-element.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn move_next(&mut self) {
match self.current.take() {
// We had no current element; the cursor was sitting at the start position
// Next element should be the head of the list
None => {
self.current = self.list.head;
self.index = 0;
}
// We had a previous element, so let's go to its next
Some(current) => unsafe {
self.current = current.as_ref().next;
self.index += 1;
},
}
}
/// Moves the cursor to the previous element of the `LinkedList`.
///
/// If the cursor is pointing to the "ghost" non-element then this will move it to
/// the last element of the `LinkedList`. If it is pointing to the first
/// element of the `LinkedList` then this will move it to the "ghost" non-element.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn move_prev(&mut self) {
match self.current.take() {
// No current. We're at the start of the list. Yield None and jump to the end.
None => {
self.current = self.list.tail;
self.index = self.list.len().checked_sub(1).unwrap_or(0);
}
// Have a prev. Yield it and go to the previous element.
Some(current) => unsafe {
self.current = current.as_ref().prev;
self.index = self.index.checked_sub(1).unwrap_or_else(|| self.list.len());
},
}
}
/// Returns a reference to the element that the cursor is currently
/// pointing to.
///
/// This returns `None` if the cursor is currently pointing to the
/// "ghost" non-element.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn current(&self) -> Option<&'a T> {
unsafe { self.current.map(|current| &(*current.as_ptr()).element) }
}
/// Returns a reference to the next element.
///
/// If the cursor is pointing to the "ghost" non-element then this returns
/// the first element of the `LinkedList`. If it is pointing to the last
/// element of the `LinkedList` then this returns `None`.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn peek_next(&self) -> Option<&'a T> {
unsafe {
let next = match self.current {
None => self.list.head,
Some(current) => current.as_ref().next,
};
next.map(|next| &(*next.as_ptr()).element)
}
}
/// Returns a reference to the previous element.
///
/// If the cursor is pointing to the "ghost" non-element then this returns
/// the last element of the `LinkedList`. If it is pointing to the first
/// element of the `LinkedList` then this returns `None`.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn peek_prev(&self) -> Option<&'a T> {
unsafe {
let prev = match self.current {
None => self.list.tail,
Some(current) => current.as_ref().prev,
};
prev.map(|prev| &(*prev.as_ptr()).element)
}
}
/// Provides a reference to the front element of the cursor's parent list,
/// or None if the list is empty.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
#[rustc_confusables("first")]
pub fn front(&self) -> Option<&'a T> {
self.list.front()
}
/// Provides a reference to the back element of the cursor's parent list,
/// or None if the list is empty.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
#[rustc_confusables("last")]
pub fn back(&self) -> Option<&'a T> {
self.list.back()
}
/// Provides a reference to the cursor's parent list.
#[must_use]
#[inline(always)]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn as_list(&self) -> &'a LinkedList<T, A> {
self.list
}
}
impl<'a, T, A: Allocator> CursorMut<'a, T, A> {
/// Returns the cursor position index within the `LinkedList`.
///
/// This returns `None` if the cursor is currently pointing to the
/// "ghost" non-element.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn index(&self) -> Option<usize> {
let _ = self.current?;
Some(self.index)
}
/// Moves the cursor to the next element of the `LinkedList`.
///
/// If the cursor is pointing to the "ghost" non-element then this will move it to
/// the first element of the `LinkedList`. If it is pointing to the last
/// element of the `LinkedList` then this will move it to the "ghost" non-element.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn move_next(&mut self) {
match self.current.take() {
// We had no current element; the cursor was sitting at the start position
// Next element should be the head of the list
None => {
self.current = self.list.head;
self.index = 0;
}
// We had a previous element, so let's go to its next
Some(current) => unsafe {
self.current = current.as_ref().next;
self.index += 1;
},
}
}
/// Moves the cursor to the previous element of the `LinkedList`.
///
/// If the cursor is pointing to the "ghost" non-element then this will move it to
/// the last element of the `LinkedList`. If it is pointing to the first
/// element of the `LinkedList` then this will move it to the "ghost" non-element.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn move_prev(&mut self) {
match self.current.take() {
// No current. We're at the start of the list. Yield None and jump to the end.
None => {
self.current = self.list.tail;
self.index = self.list.len().checked_sub(1).unwrap_or(0);
}
// Have a prev. Yield it and go to the previous element.
Some(current) => unsafe {
self.current = current.as_ref().prev;
self.index = self.index.checked_sub(1).unwrap_or_else(|| self.list.len());
},
}
}
/// Returns a reference to the element that the cursor is currently
/// pointing to.
///
/// This returns `None` if the cursor is currently pointing to the
/// "ghost" non-element.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn current(&mut self) -> Option<&mut T> {
unsafe { self.current.map(|current| &mut (*current.as_ptr()).element) }
}
/// Returns a reference to the next element.
///
/// If the cursor is pointing to the "ghost" non-element then this returns
/// the first element of the `LinkedList`. If it is pointing to the last
/// element of the `LinkedList` then this returns `None`.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn peek_next(&mut self) -> Option<&mut T> {
unsafe {
let next = match self.current {
None => self.list.head,
Some(current) => current.as_ref().next,
};
next.map(|next| &mut (*next.as_ptr()).element)
}
}
/// Returns a reference to the previous element.
///
/// If the cursor is pointing to the "ghost" non-element then this returns
/// the last element of the `LinkedList`. If it is pointing to the first
/// element of the `LinkedList` then this returns `None`.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn peek_prev(&mut self) -> Option<&mut T> {
unsafe {
let prev = match self.current {
None => self.list.tail,
Some(current) => current.as_ref().prev,
};
prev.map(|prev| &mut (*prev.as_ptr()).element)
}
}
/// Returns a read-only cursor pointing to the current element.
///
/// The lifetime of the returned `Cursor` is bound to that of the
/// `CursorMut`, which means it cannot outlive the `CursorMut` and that the
/// `CursorMut` is frozen for the lifetime of the `Cursor`.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn as_cursor(&self) -> Cursor<'_, T, A> {
Cursor { list: self.list, current: self.current, index: self.index }
}
/// Provides a read-only reference to the cursor's parent list.
///
/// The lifetime of the returned reference is bound to that of the
/// `CursorMut`, which means it cannot outlive the `CursorMut` and that the
/// `CursorMut` is frozen for the lifetime of the reference.
#[must_use]
#[inline(always)]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn as_list(&self) -> &LinkedList<T, A> {
self.list
}
}
// Now the list editing operations
impl<'a, T> CursorMut<'a, T> {
/// Inserts the elements from the given `LinkedList` after the current one.
///
/// If the cursor is pointing at the "ghost" non-element then the new elements are
/// inserted at the start of the `LinkedList`.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn splice_after(&mut self, list: LinkedList<T>) {
unsafe {
let (splice_head, splice_tail, splice_len) = match list.detach_all_nodes() {
Some(parts) => parts,
_ => return,
};
let node_next = match self.current {
None => self.list.head,
Some(node) => node.as_ref().next,
};
self.list.splice_nodes(self.current, node_next, splice_head, splice_tail, splice_len);
if self.current.is_none() {
// The "ghost" non-element's index has changed.
self.index = self.list.len;
}
}
}
/// Inserts the elements from the given `LinkedList` before the current one.
///
/// If the cursor is pointing at the "ghost" non-element then the new elements are
/// inserted at the end of the `LinkedList`.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn splice_before(&mut self, list: LinkedList<T>) {
unsafe {
let (splice_head, splice_tail, splice_len) = match list.detach_all_nodes() {
Some(parts) => parts,
_ => return,
};
let node_prev = match self.current {
None => self.list.tail,
Some(node) => node.as_ref().prev,
};
self.list.splice_nodes(node_prev, self.current, splice_head, splice_tail, splice_len);
self.index += splice_len;
}
}
}
impl<'a, T, A: Allocator> CursorMut<'a, T, A> {
/// Inserts a new element into the `LinkedList` after the current one.
///
/// If the cursor is pointing at the "ghost" non-element then the new element is
/// inserted at the front of the `LinkedList`.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn insert_after(&mut self, item: T) {
unsafe {
let spliced_node = Box::leak(Box::new_in(Node::new(item), &self.list.alloc)).into();
let node_next = match self.current {
None => self.list.head,
Some(node) => node.as_ref().next,
};
self.list.splice_nodes(self.current, node_next, spliced_node, spliced_node, 1);
if self.current.is_none() {
// The "ghost" non-element's index has changed.
self.index = self.list.len;
}
}
}
/// Inserts a new element into the `LinkedList` before the current one.
///
/// If the cursor is pointing at the "ghost" non-element then the new element is
/// inserted at the end of the `LinkedList`.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn insert_before(&mut self, item: T) {
unsafe {
let spliced_node = Box::leak(Box::new_in(Node::new(item), &self.list.alloc)).into();
let node_prev = match self.current {
None => self.list.tail,
Some(node) => node.as_ref().prev,
};
self.list.splice_nodes(node_prev, self.current, spliced_node, spliced_node, 1);
self.index += 1;
}
}
/// Removes the current element from the `LinkedList`.
///
/// The element that was removed is returned, and the cursor is
/// moved to point to the next element in the `LinkedList`.
///
/// If the cursor is currently pointing to the "ghost" non-element then no element
/// is removed and `None` is returned.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn remove_current(&mut self) -> Option<T> {
let unlinked_node = self.current?;
unsafe {
self.current = unlinked_node.as_ref().next;
self.list.unlink_node(unlinked_node);
let unlinked_node = Box::from_raw_in(unlinked_node.as_ptr(), &self.list.alloc);
Some(unlinked_node.element)
}
}
/// Removes the current element from the `LinkedList` without deallocating the list node.
///
/// The node that was removed is returned as a new `LinkedList` containing only this node.
/// The cursor is moved to point to the next element in the current `LinkedList`.
///
/// If the cursor is currently pointing to the "ghost" non-element then no element
/// is removed and `None` is returned.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn remove_current_as_list(&mut self) -> Option<LinkedList<T, A>>
where
A: Clone,
{
let mut unlinked_node = self.current?;
unsafe {
self.current = unlinked_node.as_ref().next;
self.list.unlink_node(unlinked_node);
unlinked_node.as_mut().prev = None;
unlinked_node.as_mut().next = None;
Some(LinkedList {
head: Some(unlinked_node),
tail: Some(unlinked_node),
len: 1,
alloc: self.list.alloc.clone(),
marker: PhantomData,
})
}
}
/// Splits the list into two after the current element. This will return a
/// new list consisting of everything after the cursor, with the original
/// list retaining everything before.
///
/// If the cursor is pointing at the "ghost" non-element then the entire contents
/// of the `LinkedList` are moved.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn split_after(&mut self) -> LinkedList<T, A>
where
A: Clone,
{
let split_off_idx = if self.index == self.list.len { 0 } else { self.index + 1 };
if self.index == self.list.len {
// The "ghost" non-element's index has changed to 0.
self.index = 0;
}
unsafe { self.list.split_off_after_node(self.current, split_off_idx) }
}
/// Splits the list into two before the current element. This will return a
/// new list consisting of everything before the cursor, with the original
/// list retaining everything after.
///
/// If the cursor is pointing at the "ghost" non-element then the entire contents
/// of the `LinkedList` are moved.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn split_before(&mut self) -> LinkedList<T, A>
where
A: Clone,
{
let split_off_idx = self.index;
self.index = 0;
unsafe { self.list.split_off_before_node(self.current, split_off_idx) }
}
/// Appends an element to the front of the cursor's parent list. The node
/// that the cursor points to is unchanged, even if it is the "ghost" node.
///
/// This operation should compute in *O*(1) time.
// `push_front` continues to point to "ghost" when it adds a node to mimic
// the behavior of `insert_before` on an empty list.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn push_front(&mut self, elt: T) {
// Safety: We know that `push_front` does not change the position in
// memory of other nodes. This ensures that `self.current` remains
// valid.
self.list.push_front(elt);
self.index += 1;
}
/// Appends an element to the back of the cursor's parent list. The node
/// that the cursor points to is unchanged, even if it is the "ghost" node.
///
/// This operation should compute in *O*(1) time.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
#[rustc_confusables("push", "append")]
pub fn push_back(&mut self, elt: T) {
// Safety: We know that `push_back` does not change the position in
// memory of other nodes. This ensures that `self.current` remains
// valid.
self.list.push_back(elt);
if self.current().is_none() {
// The index of "ghost" is the length of the list, so we just need
// to increment self.index to reflect the new length of the list.
self.index += 1;
}
}
/// Removes the first element from the cursor's parent list and returns it,
/// or None if the list is empty. The element the cursor points to remains
/// unchanged, unless it was pointing to the front element. In that case, it
/// points to the new front element.
///
/// This operation should compute in *O*(1) time.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn pop_front(&mut self) -> Option<T> {
// We can't check if current is empty, we must check the list directly.
// It is possible for `self.current == None` and the list to be
// non-empty.
if self.list.is_empty() {
None
} else {
// We can't point to the node that we pop. Copying the behavior of
// `remove_current`, we move on to the next node in the sequence.
// If the list is of length 1 then we end pointing to the "ghost"
// node at index 0, which is expected.
if self.list.head == self.current {
self.move_next();
} else {
self.index -= 1;
}
self.list.pop_front()
}
}
/// Removes the last element from the cursor's parent list and returns it,
/// or None if the list is empty. The element the cursor points to remains
/// unchanged, unless it was pointing to the back element. In that case, it
/// points to the "ghost" element.
///
/// This operation should compute in *O*(1) time.
#[unstable(feature = "linked_list_cursors", issue = "58533")]
#[rustc_confusables("pop")]
pub fn pop_back(&mut self) -> Option<T> {
if self.list.is_empty() {
None
} else {
if self.list.tail == self.current {
// The index now reflects the length of the list. It was the
// length of the list minus 1, but now the list is 1 smaller. No
// change is needed for `index`.
self.current = None;
} else if self.current.is_none() {
self.index = self.list.len - 1;
}
self.list.pop_back()
}
}
/// Provides a reference to the front element of the cursor's parent list,
/// or None if the list is empty.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
#[rustc_confusables("first")]
pub fn front(&self) -> Option<&T> {
self.list.front()
}
/// Provides a mutable reference to the front element of the cursor's
/// parent list, or None if the list is empty.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn front_mut(&mut self) -> Option<&mut T> {
self.list.front_mut()
}
/// Provides a reference to the back element of the cursor's parent list,
/// or None if the list is empty.
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
#[rustc_confusables("last")]
pub fn back(&self) -> Option<&T> {
self.list.back()
}
/// Provides a mutable reference to back element of the cursor's parent
/// list, or `None` if the list is empty.
///
/// # Examples
/// Building and mutating a list with a cursor, then getting the back element:
/// ```
/// #![feature(linked_list_cursors)]
/// use std::collections::LinkedList;
/// let mut dl = LinkedList::new();
/// dl.push_front(3);
/// dl.push_front(2);
/// dl.push_front(1);
/// let mut cursor = dl.cursor_front_mut();
/// *cursor.current().unwrap() = 99;
/// *cursor.back_mut().unwrap() = 0;
/// let mut contents = dl.into_iter();
/// assert_eq!(contents.next(), Some(99));
/// assert_eq!(contents.next(), Some(2));
/// assert_eq!(contents.next(), Some(0));
/// assert_eq!(contents.next(), None);
/// ```
#[must_use]
#[unstable(feature = "linked_list_cursors", issue = "58533")]
pub fn back_mut(&mut self) -> Option<&mut T> {
self.list.back_mut()
}
}
/// An iterator produced by calling `extract_if` on LinkedList.
#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
#[must_use = "iterators are lazy and do nothing unless consumed"]
pub struct ExtractIf<
'a,
T: 'a,
F: 'a,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> where
F: FnMut(&mut T) -> bool,
{
list: &'a mut LinkedList<T, A>,
it: Option<NonNull<Node<T>>>,
pred: F,
idx: usize,
old_len: usize,
}
#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
impl<T, F, A: Allocator> Iterator for ExtractIf<'_, T, F, A>
where
F: FnMut(&mut T) -> bool,
{
type Item = T;
fn next(&mut self) -> Option<T> {
while let Some(mut node) = self.it {
unsafe {
self.it = node.as_ref().next;
self.idx += 1;
if (self.pred)(&mut node.as_mut().element) {
// `unlink_node` is okay with aliasing `element` references.
self.list.unlink_node(node);
return Some(Box::from_raw_in(node.as_ptr(), &self.list.alloc).element);
}
}
}
None
}
fn size_hint(&self) -> (usize, Option<usize>) {
(0, Some(self.old_len - self.idx))
}
}
#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
impl<T: fmt::Debug, F> fmt::Debug for ExtractIf<'_, T, F>
where
F: FnMut(&mut T) -> bool,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("ExtractIf").field(&self.list).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> Iterator for IntoIter<T, A> {
type Item = T;
#[inline]
fn next(&mut self) -> Option<T> {
self.list.pop_front()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
(self.list.len, Some(self.list.len))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
#[inline]
fn next_back(&mut self) -> Option<T> {
self.list.pop_back()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {}
#[stable(feature = "fused", since = "1.26.0")]
impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
#[stable(feature = "default_iters", since = "1.70.0")]
impl<T> Default for IntoIter<T> {
/// Creates an empty `linked_list::IntoIter`.
///
/// ```
/// # use std::collections::linked_list;
/// let iter: linked_list::IntoIter<u8> = Default::default();
/// assert_eq!(iter.len(), 0);
/// ```
fn default() -> Self {
LinkedList::new().into_iter()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> FromIterator<T> for LinkedList<T> {
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
let mut list = Self::new();
list.extend(iter);
list
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> IntoIterator for LinkedList<T, A> {
type Item = T;
type IntoIter = IntoIter<T, A>;
/// Consumes the list into an iterator yielding elements by value.
#[inline]
fn into_iter(self) -> IntoIter<T, A> {
IntoIter { list: self }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T, A: Allocator> IntoIterator for &'a LinkedList<T, A> {
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, A: Allocator> IntoIterator for &'a mut LinkedList<T, A> {
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<T, A: Allocator> Extend<T> for LinkedList<T, A> {
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
<Self as SpecExtend<I>>::spec_extend(self, iter);
}
#[inline]
fn extend_one(&mut self, elem: T) {
self.push_back(elem);
}
}
impl<I: IntoIterator, A: Allocator> SpecExtend<I> for LinkedList<I::Item, A> {
default fn spec_extend(&mut self, iter: I) {
iter.into_iter().for_each(move |elt| self.push_back(elt));
}
}
impl<T> SpecExtend<LinkedList<T>> for LinkedList<T> {
fn spec_extend(&mut self, ref mut other: LinkedList<T>) {
self.append(other);
}
}
#[stable(feature = "extend_ref", since = "1.2.0")]
impl<'a, T: 'a + Copy, A: Allocator> Extend<&'a T> for LinkedList<T, A> {
fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
self.extend(iter.into_iter().cloned());
}
#[inline]
fn extend_one(&mut self, &elem: &'a T) {
self.push_back(elem);
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: PartialEq, A: Allocator> PartialEq for LinkedList<T, A> {
fn eq(&self, other: &Self) -> bool {
self.len() == other.len() && self.iter().eq(other)
}
fn ne(&self, other: &Self) -> bool {
self.len() != other.len() || self.iter().ne(other)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Eq, A: Allocator> Eq for LinkedList<T, A> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: PartialOrd, A: Allocator> PartialOrd for LinkedList<T, A> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
self.iter().partial_cmp(other)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Ord, A: Allocator> Ord for LinkedList<T, A> {
#[inline]
fn cmp(&self, other: &Self) -> Ordering {
self.iter().cmp(other)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Clone, A: Allocator + Clone> Clone for LinkedList<T, A> {
fn clone(&self) -> Self {
let mut list = Self::new_in(self.alloc.clone());
list.extend(self.iter().cloned());
list
}
/// Overwrites the contents of `self` with a clone of the contents of `source`.
///
/// This method is preferred over simply assigning `source.clone()` to `self`,
/// as it avoids reallocation of the nodes of the linked list. Additionally,
/// if the element type `T` overrides `clone_from()`, this will reuse the
/// resources of `self`'s elements as well.
fn clone_from(&mut self, source: &Self) {
let mut source_iter = source.iter();
if self.len() > source.len() {
self.split_off(source.len());
}
for (elem, source_elem) in self.iter_mut().zip(&mut source_iter) {
elem.clone_from(source_elem);
}
if !source_iter.is_empty() {
self.extend(source_iter.cloned());
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: fmt::Debug, A: Allocator> fmt::Debug for LinkedList<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Hash, A: Allocator> Hash for LinkedList<T, A> {
fn hash<H: Hasher>(&self, state: &mut H) {
state.write_length_prefix(self.len());
for elt in self {
elt.hash(state);
}
}
}
#[stable(feature = "std_collections_from_array", since = "1.56.0")]
impl<T, const N: usize> From<[T; N]> for LinkedList<T> {
/// Converts a `[T; N]` into a `LinkedList<T>`.
///
/// ```
/// use std::collections::LinkedList;
///
/// let list1 = LinkedList::from([1, 2, 3, 4]);
/// let list2: LinkedList<_> = [1, 2, 3, 4].into();
/// assert_eq!(list1, list2);
/// ```
fn from(arr: [T; N]) -> Self {
Self::from_iter(arr)
}
}
// Ensure that `LinkedList` and its read-only iterators are covariant in their type parameters.
#[allow(dead_code)]
fn assert_covariance() {
fn a<'a>(x: LinkedList<&'static str>) -> LinkedList<&'a str> {
x
}
fn b<'i, 'a>(x: Iter<'i, &'static str>) -> Iter<'i, &'a str> {
x
}
fn c<'a>(x: IntoIter<&'static str>) -> IntoIter<&'a str> {
x
}
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Send, A: Allocator + Send> Send for LinkedList<T, A> {}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Sync, A: Allocator + Sync> Sync for LinkedList<T, A> {}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Sync> Send for Iter<'_, T> {}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Sync> Sync for Iter<'_, T> {}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Send> Send for IterMut<'_, T> {}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Sync> Sync for IterMut<'_, T> {}
#[unstable(feature = "linked_list_cursors", issue = "58533")]
unsafe impl<T: Sync, A: Allocator + Sync> Send for Cursor<'_, T, A> {}
#[unstable(feature = "linked_list_cursors", issue = "58533")]
unsafe impl<T: Sync, A: Allocator + Sync> Sync for Cursor<'_, T, A> {}
#[unstable(feature = "linked_list_cursors", issue = "58533")]
unsafe impl<T: Send, A: Allocator + Send> Send for CursorMut<'_, T, A> {}
#[unstable(feature = "linked_list_cursors", issue = "58533")]
unsafe impl<T: Sync, A: Allocator + Sync> Sync for CursorMut<'_, T, A> {}