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<h1 id="final-code"><a class="header" href="#final-code">Final Code</a></h1>
<p>我真不敢相信，我居然让你坐在那里，听我从头开始重新实现 std::collections::LinkedList，一路上我犯了很多繁琐的小错误。</p>
<p>我做到了，书写完了，我终于可以休息了。</p>
<p>好了，下面是我们完整重写的 1200 行代码的全部内容。这应该与 <a href="https://github.com/contain-rs/linked-list/commit/5b69cc29454595172a5167a09277660342b78092">this commit</a> 的文本相同。</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>use std::cmp::Ordering;
use std::fmt::{self, Debug};
use std::hash::{Hash, Hasher};
use std::iter::FromIterator;
use std::marker::PhantomData;
use std::ptr::NonNull;
pub struct LinkedList&lt;T&gt; {
front: Link&lt;T&gt;,
back: Link&lt;T&gt;,
len: usize,
_boo: PhantomData&lt;T&gt;,
}
type Link&lt;T&gt; = Option&lt;NonNull&lt;Node&lt;T&gt;&gt;&gt;;
struct Node&lt;T&gt; {
front: Link&lt;T&gt;,
back: Link&lt;T&gt;,
elem: T,
}
pub struct Iter&lt;'a, T&gt; {
front: Link&lt;T&gt;,
back: Link&lt;T&gt;,
len: usize,
_boo: PhantomData&lt;&amp;'a T&gt;,
}
pub struct IterMut&lt;'a, T&gt; {
front: Link&lt;T&gt;,
back: Link&lt;T&gt;,
len: usize,
_boo: PhantomData&lt;&amp;'a mut T&gt;,
}
pub struct IntoIter&lt;T&gt; {
list: LinkedList&lt;T&gt;,
}
pub struct CursorMut&lt;'a, T&gt; {
list: &amp;'a mut LinkedList&lt;T&gt;,
cur: Link&lt;T&gt;,
index: Option&lt;usize&gt;,
}
impl&lt;T&gt; LinkedList&lt;T&gt; {
pub fn new() -&gt; Self {
Self {
front: None,
back: None,
len: 0,
_boo: PhantomData,
}
}
pub fn push_front(&amp;mut self, elem: T) {
// SAFETY: it's a linked-list, what do you want?
unsafe {
let new = NonNull::new_unchecked(Box::into_raw(Box::new(Node {
front: None,
back: None,
elem,
})));
if let Some(old) = self.front {
// Put the new front before the old one
(*old.as_ptr()).front = Some(new);
(*new.as_ptr()).back = Some(old);
} else {
// If there's no front, then we're the empty list and need
// to set the back too.
self.back = Some(new);
}
// These things always happen!
self.front = Some(new);
self.len += 1;
}
}
pub fn push_back(&amp;mut self, elem: T) {
// SAFETY: it's a linked-list, what do you want?
unsafe {
let new = NonNull::new_unchecked(Box::into_raw(Box::new(Node {
back: None,
front: None,
elem,
})));
if let Some(old) = self.back {
// Put the new back before the old one
(*old.as_ptr()).back = Some(new);
(*new.as_ptr()).front = Some(old);
} else {
// If there's no back, then we're the empty list and need
// to set the front too.
self.front = Some(new);
}
// These things always happen!
self.back = Some(new);
self.len += 1;
}
}
pub fn pop_front(&amp;mut self) -&gt; Option&lt;T&gt; {
unsafe {
// Only have to do stuff if there is a front node to pop.
self.front.map(|node| {
// Bring the Box back to life so we can move out its value and
// Drop it (Box continues to magically understand this for us).
let boxed_node = Box::from_raw(node.as_ptr());
let result = boxed_node.elem;
// Make the next node into the new front.
self.front = boxed_node.back;
if let Some(new) = self.front {
// Cleanup its reference to the removed node
(*new.as_ptr()).front = None;
} else {
// If the front is now null, then this list is now empty!
self.back = None;
}
self.len -= 1;
result
// Box gets implicitly freed here, knows there is no T.
})
}
}
pub fn pop_back(&amp;mut self) -&gt; Option&lt;T&gt; {
unsafe {
// Only have to do stuff if there is a back node to pop.
self.back.map(|node| {
// Bring the Box front to life so we can move out its value and
// Drop it (Box continues to magically understand this for us).
let boxed_node = Box::from_raw(node.as_ptr());
let result = boxed_node.elem;
// Make the next node into the new back.
self.back = boxed_node.front;
if let Some(new) = self.back {
// Cleanup its reference to the removed node
(*new.as_ptr()).back = None;
} else {
// If the back is now null, then this list is now empty!
self.front = None;
}
self.len -= 1;
result
// Box gets implicitly freed here, knows there is no T.
})
}
}
pub fn front(&amp;self) -&gt; Option&lt;&amp;T&gt; {
unsafe { self.front.map(|node| &amp;(*node.as_ptr()).elem) }
}
pub fn front_mut(&amp;mut self) -&gt; Option&lt;&amp;mut T&gt; {
unsafe { self.front.map(|node| &amp;mut (*node.as_ptr()).elem) }
}
pub fn back(&amp;self) -&gt; Option&lt;&amp;T&gt; {
unsafe { self.back.map(|node| &amp;(*node.as_ptr()).elem) }
}
pub fn back_mut(&amp;mut self) -&gt; Option&lt;&amp;mut T&gt; {
unsafe { self.back.map(|node| &amp;mut (*node.as_ptr()).elem) }
}
pub fn len(&amp;self) -&gt; usize {
self.len
}
pub fn is_empty(&amp;self) -&gt; bool {
self.len == 0
}
pub fn clear(&amp;mut self) {
// Oh look it's drop again
while self.pop_front().is_some() {}
}
pub fn iter(&amp;self) -&gt; Iter&lt;T&gt; {
Iter {
front: self.front,
back: self.back,
len: self.len,
_boo: PhantomData,
}
}
pub fn iter_mut(&amp;mut self) -&gt; IterMut&lt;T&gt; {
IterMut {
front: self.front,
back: self.back,
len: self.len,
_boo: PhantomData,
}
}
pub fn cursor_mut(&amp;mut self) -&gt; CursorMut&lt;T&gt; {
CursorMut {
list: self,
cur: None,
index: None,
}
}
}
impl&lt;T&gt; Drop for LinkedList&lt;T&gt; {
fn drop(&amp;mut self) {
// Pop until we have to stop
while self.pop_front().is_some() {}
}
}
impl&lt;T&gt; Default for LinkedList&lt;T&gt; {
fn default() -&gt; Self {
Self::new()
}
}
impl&lt;T: Clone&gt; Clone for LinkedList&lt;T&gt; {
fn clone(&amp;self) -&gt; Self {
let mut new_list = Self::new();
for item in self {
new_list.push_back(item.clone());
}
new_list
}
}
impl&lt;T&gt; Extend&lt;T&gt; for LinkedList&lt;T&gt; {
fn extend&lt;I: IntoIterator&lt;Item = T&gt;&gt;(&amp;mut self, iter: I) {
for item in iter {
self.push_back(item);
}
}
}
impl&lt;T&gt; FromIterator&lt;T&gt; for LinkedList&lt;T&gt; {
fn from_iter&lt;I: IntoIterator&lt;Item = T&gt;&gt;(iter: I) -&gt; Self {
let mut list = Self::new();
list.extend(iter);
list
}
}
impl&lt;T: Debug&gt; Debug for LinkedList&lt;T&gt; {
fn fmt(&amp;self, f: &amp;mut fmt::Formatter&lt;'_&gt;) -&gt; fmt::Result {
f.debug_list().entries(self).finish()
}
}
impl&lt;T: PartialEq&gt; PartialEq for LinkedList&lt;T&gt; {
fn eq(&amp;self, other: &amp;Self) -&gt; bool {
self.len() == other.len() &amp;&amp; self.iter().eq(other)
}
}
impl&lt;T: Eq&gt; Eq for LinkedList&lt;T&gt; {}
impl&lt;T: PartialOrd&gt; PartialOrd for LinkedList&lt;T&gt; {
fn partial_cmp(&amp;self, other: &amp;Self) -&gt; Option&lt;Ordering&gt; {
self.iter().partial_cmp(other)
}
}
impl&lt;T: Ord&gt; Ord for LinkedList&lt;T&gt; {
fn cmp(&amp;self, other: &amp;Self) -&gt; Ordering {
self.iter().cmp(other)
}
}
impl&lt;T: Hash&gt; Hash for LinkedList&lt;T&gt; {
fn hash&lt;H: Hasher&gt;(&amp;self, state: &amp;mut H) {
self.len().hash(state);
for item in self {
item.hash(state);
}
}
}
impl&lt;'a, T&gt; IntoIterator for &amp;'a LinkedList&lt;T&gt; {
type IntoIter = Iter&lt;'a, T&gt;;
type Item = &amp;'a T;
fn into_iter(self) -&gt; Self::IntoIter {
self.iter()
}
}
impl&lt;'a, T&gt; Iterator for Iter&lt;'a, T&gt; {
type Item = &amp;'a T;
fn next(&amp;mut self) -&gt; Option&lt;Self::Item&gt; {
// While self.front == self.back is a tempting condition to check here,
// it won't do the right for yielding the last element! That sort of
// thing only works for arrays because of &quot;one-past-the-end&quot; pointers.
if self.len &gt; 0 {
// We could unwrap front, but this is safer and easier
self.front.map(|node| unsafe {
self.len -= 1;
self.front = (*node.as_ptr()).back;
&amp;(*node.as_ptr()).elem
})
} else {
None
}
}
fn size_hint(&amp;self) -&gt; (usize, Option&lt;usize&gt;) {
(self.len, Some(self.len))
}
}
impl&lt;'a, T&gt; DoubleEndedIterator for Iter&lt;'a, T&gt; {
fn next_back(&amp;mut self) -&gt; Option&lt;Self::Item&gt; {
if self.len &gt; 0 {
self.back.map(|node| unsafe {
self.len -= 1;
self.back = (*node.as_ptr()).front;
&amp;(*node.as_ptr()).elem
})
} else {
None
}
}
}
impl&lt;'a, T&gt; ExactSizeIterator for Iter&lt;'a, T&gt; {
fn len(&amp;self) -&gt; usize {
self.len
}
}
impl&lt;'a, T&gt; IntoIterator for &amp;'a mut LinkedList&lt;T&gt; {
type IntoIter = IterMut&lt;'a, T&gt;;
type Item = &amp;'a mut T;
fn into_iter(self) -&gt; Self::IntoIter {
self.iter_mut()
}
}
impl&lt;'a, T&gt; Iterator for IterMut&lt;'a, T&gt; {
type Item = &amp;'a mut T;
fn next(&amp;mut self) -&gt; Option&lt;Self::Item&gt; {
// While self.front == self.back is a tempting condition to check here,
// it won't do the right for yielding the last element! That sort of
// thing only works for arrays because of &quot;one-past-the-end&quot; pointers.
if self.len &gt; 0 {
// We could unwrap front, but this is safer and easier
self.front.map(|node| unsafe {
self.len -= 1;
self.front = (*node.as_ptr()).back;
&amp;mut (*node.as_ptr()).elem
})
} else {
None
}
}
fn size_hint(&amp;self) -&gt; (usize, Option&lt;usize&gt;) {
(self.len, Some(self.len))
}
}
impl&lt;'a, T&gt; DoubleEndedIterator for IterMut&lt;'a, T&gt; {
fn next_back(&amp;mut self) -&gt; Option&lt;Self::Item&gt; {
if self.len &gt; 0 {
self.back.map(|node| unsafe {
self.len -= 1;
self.back = (*node.as_ptr()).front;
&amp;mut (*node.as_ptr()).elem
})
} else {
None
}
}
}
impl&lt;'a, T&gt; ExactSizeIterator for IterMut&lt;'a, T&gt; {
fn len(&amp;self) -&gt; usize {
self.len
}
}
impl&lt;T&gt; IntoIterator for LinkedList&lt;T&gt; {
type IntoIter = IntoIter&lt;T&gt;;
type Item = T;
fn into_iter(self) -&gt; Self::IntoIter {
IntoIter { list: self }
}
}
impl&lt;T&gt; Iterator for IntoIter&lt;T&gt; {
type Item = T;
fn next(&amp;mut self) -&gt; Option&lt;Self::Item&gt; {
self.list.pop_front()
}
fn size_hint(&amp;self) -&gt; (usize, Option&lt;usize&gt;) {
(self.list.len, Some(self.list.len))
}
}
impl&lt;T&gt; DoubleEndedIterator for IntoIter&lt;T&gt; {
fn next_back(&amp;mut self) -&gt; Option&lt;Self::Item&gt; {
self.list.pop_back()
}
}
impl&lt;T&gt; ExactSizeIterator for IntoIter&lt;T&gt; {
fn len(&amp;self) -&gt; usize {
self.list.len
}
}
impl&lt;'a, T&gt; CursorMut&lt;'a, T&gt; {
pub fn index(&amp;self) -&gt; Option&lt;usize&gt; {
self.index
}
pub fn move_next(&amp;mut self) {
if let Some(cur) = self.cur {
unsafe {
// We're on a real element, go to its next (back)
self.cur = (*cur.as_ptr()).back;
if self.cur.is_some() {
*self.index.as_mut().unwrap() += 1;
} else {
// We just walked to the ghost, no more index
self.index = None;
}
}
} else if !self.list.is_empty() {
// We're at the ghost, and there is a real front, so move to it!
self.cur = self.list.front;
self.index = Some(0)
} else {
// We're at the ghost, but that's the only element... do nothing.
}
}
pub fn move_prev(&amp;mut self) {
if let Some(cur) = self.cur {
unsafe {
// We're on a real element, go to its previous (front)
self.cur = (*cur.as_ptr()).front;
if self.cur.is_some() {
*self.index.as_mut().unwrap() -= 1;
} else {
// We just walked to the ghost, no more index
self.index = None;
}
}
} else if !self.list.is_empty() {
// We're at the ghost, and there is a real back, so move to it!
self.cur = self.list.back;
self.index = Some(self.list.len - 1)
} else {
// We're at the ghost, but that's the only element... do nothing.
}
}
pub fn current(&amp;mut self) -&gt; Option&lt;&amp;mut T&gt; {
unsafe { self.cur.map(|node| &amp;mut (*node.as_ptr()).elem) }
}
pub fn peek_next(&amp;mut self) -&gt; Option&lt;&amp;mut T&gt; {
unsafe {
let next = if let Some(cur) = self.cur {
// Normal case, try to follow the cur node's back pointer
(*cur.as_ptr()).back
} else {
// Ghost case, try to use the list's front pointer
self.list.front
};
// Yield the element if the next node exists
next.map(|node| &amp;mut (*node.as_ptr()).elem)
}
}
pub fn peek_prev(&amp;mut self) -&gt; Option&lt;&amp;mut T&gt; {
unsafe {
let prev = if let Some(cur) = self.cur {
// Normal case, try to follow the cur node's front pointer
(*cur.as_ptr()).front
} else {
// Ghost case, try to use the list's back pointer
self.list.back
};
// Yield the element if the prev node exists
prev.map(|node| &amp;mut (*node.as_ptr()).elem)
}
}
pub fn split_before(&amp;mut self) -&gt; LinkedList&lt;T&gt; {
// We have this:
//
// list.front -&gt; A &lt;-&gt; B &lt;-&gt; C &lt;-&gt; D &lt;- list.back
// ^
// cur
//
//
// And we want to produce this:
//
// list.front -&gt; C &lt;-&gt; D &lt;- list.back
// ^
// cur
//
//
// return.front -&gt; A &lt;-&gt; B &lt;- return.back
//
if let Some(cur) = self.cur {
// We are pointing at a real element, so the list is non-empty.
unsafe {
// Current state
let old_len = self.list.len;
let old_idx = self.index.unwrap();
let prev = (*cur.as_ptr()).front;
// What self will become
let new_len = old_len - old_idx;
let new_front = self.cur;
let new_back = self.list.back;
let new_idx = Some(0);
// What the output will become
let output_len = old_len - new_len;
let output_front = self.list.front;
let output_back = prev;
// Break the links between cur and prev
if let Some(prev) = prev {
(*cur.as_ptr()).front = None;
(*prev.as_ptr()).back = None;
}
// Produce the result:
self.list.len = new_len;
self.list.front = new_front;
self.list.back = new_back;
self.index = new_idx;
LinkedList {
front: output_front,
back: output_back,
len: output_len,
_boo: PhantomData,
}
}
} else {
// We're at the ghost, just replace our list with an empty one.
// No other state needs to be changed.
std::mem::replace(self.list, LinkedList::new())
}
}
pub fn split_after(&amp;mut self) -&gt; LinkedList&lt;T&gt; {
// We have this:
//
// list.front -&gt; A &lt;-&gt; B &lt;-&gt; C &lt;-&gt; D &lt;- list.back
// ^
// cur
//
//
// And we want to produce this:
//
// list.front -&gt; A &lt;-&gt; B &lt;- list.back
// ^
// cur
//
//
// return.front -&gt; C &lt;-&gt; D &lt;- return.back
//
if let Some(cur) = self.cur {
// We are pointing at a real element, so the list is non-empty.
unsafe {
// Current state
let old_len = self.list.len;
let old_idx = self.index.unwrap();
let next = (*cur.as_ptr()).back;
// What self will become
let new_len = old_idx + 1;
let new_back = self.cur;
let new_front = self.list.front;
let new_idx = Some(old_idx);
// What the output will become
let output_len = old_len - new_len;
let output_front = next;
let output_back = self.list.back;
// Break the links between cur and next
if let Some(next) = next {
(*cur.as_ptr()).back = None;
(*next.as_ptr()).front = None;
}
// Produce the result:
self.list.len = new_len;
self.list.front = new_front;
self.list.back = new_back;
self.index = new_idx;
LinkedList {
front: output_front,
back: output_back,
len: output_len,
_boo: PhantomData,
}
}
} else {
// We're at the ghost, just replace our list with an empty one.
// No other state needs to be changed.
std::mem::replace(self.list, LinkedList::new())
}
}
pub fn splice_before(&amp;mut self, mut input: LinkedList&lt;T&gt;) {
// We have this:
//
// input.front -&gt; 1 &lt;-&gt; 2 &lt;- input.back
//
// list.front -&gt; A &lt;-&gt; B &lt;-&gt; C &lt;- list.back
// ^
// cur
//
//
// Becoming this:
//
// list.front -&gt; A &lt;-&gt; 1 &lt;-&gt; 2 &lt;-&gt; B &lt;-&gt; C &lt;- list.back
// ^
// cur
//
unsafe {
// We can either `take` the input's pointers or `mem::forget`
// it. Using `take` is more responsible in case we ever do custom
// allocators or something that also needs to be cleaned up!
if input.is_empty() {
// Input is empty, do nothing.
} else if let Some(cur) = self.cur {
// Both lists are non-empty
let in_front = input.front.take().unwrap();
let in_back = input.back.take().unwrap();
if let Some(prev) = (*cur.as_ptr()).front {
// General Case, no boundaries, just internal fixups
(*prev.as_ptr()).back = Some(in_front);
(*in_front.as_ptr()).front = Some(prev);
(*cur.as_ptr()).front = Some(in_back);
(*in_back.as_ptr()).back = Some(cur);
} else {
// No prev, we're appending to the front
(*cur.as_ptr()).front = Some(in_back);
(*in_back.as_ptr()).back = Some(cur);
self.list.front = Some(in_front);
}
// Index moves forward by input length
*self.index.as_mut().unwrap() += input.len;
} else if let Some(back) = self.list.back {
// We're on the ghost but non-empty, append to the back
let in_front = input.front.take().unwrap();
let in_back = input.back.take().unwrap();
(*back.as_ptr()).back = Some(in_front);
(*in_front.as_ptr()).front = Some(back);
self.list.back = Some(in_back);
} else {
// We're empty, become the input, remain on the ghost
std::mem::swap(self.list, &amp;mut input);
}
self.list.len += input.len;
// Not necessary but Polite To Do
input.len = 0;
// Input dropped here
}
}
pub fn splice_after(&amp;mut self, mut input: LinkedList&lt;T&gt;) {
// We have this:
//
// input.front -&gt; 1 &lt;-&gt; 2 &lt;- input.back
//
// list.front -&gt; A &lt;-&gt; B &lt;-&gt; C &lt;- list.back
// ^
// cur
//
//
// Becoming this:
//
// list.front -&gt; A &lt;-&gt; B &lt;-&gt; 1 &lt;-&gt; 2 &lt;-&gt; C &lt;- list.back
// ^
// cur
//
unsafe {
// We can either `take` the input's pointers or `mem::forget`
// it. Using `take` is more responsible in case we ever do custom
// allocators or something that also needs to be cleaned up!
if input.is_empty() {
// Input is empty, do nothing.
} else if let Some(cur) = self.cur {
// Both lists are non-empty
let in_front = input.front.take().unwrap();
let in_back = input.back.take().unwrap();
if let Some(next) = (*cur.as_ptr()).back {
// General Case, no boundaries, just internal fixups
(*next.as_ptr()).front = Some(in_back);
(*in_back.as_ptr()).back = Some(next);
(*cur.as_ptr()).back = Some(in_front);
(*in_front.as_ptr()).front = Some(cur);
} else {
// No next, we're appending to the back
(*cur.as_ptr()).back = Some(in_front);
(*in_front.as_ptr()).front = Some(cur);
self.list.back = Some(in_back);
}
// Index doesn't change
} else if let Some(front) = self.list.front {
// We're on the ghost but non-empty, append to the front
let in_front = input.front.take().unwrap();
let in_back = input.back.take().unwrap();
(*front.as_ptr()).front = Some(in_back);
(*in_back.as_ptr()).back = Some(front);
self.list.front = Some(in_front);
} else {
// We're empty, become the input, remain on the ghost
std::mem::swap(self.list, &amp;mut input);
}
self.list.len += input.len;
// Not necessary but Polite To Do
input.len = 0;
// Input dropped here
}
}
}
unsafe impl&lt;T: Send&gt; Send for LinkedList&lt;T&gt; {}
unsafe impl&lt;T: Sync&gt; Sync for LinkedList&lt;T&gt; {}
unsafe impl&lt;'a, T: Send&gt; Send for Iter&lt;'a, T&gt; {}
unsafe impl&lt;'a, T: Sync&gt; Sync for Iter&lt;'a, T&gt; {}
unsafe impl&lt;'a, T: Send&gt; Send for IterMut&lt;'a, T&gt; {}
unsafe impl&lt;'a, T: Sync&gt; Sync for IterMut&lt;'a, T&gt; {}
#[allow(dead_code)]
fn assert_properties() {
fn is_send&lt;T: Send&gt;() {}
fn is_sync&lt;T: Sync&gt;() {}
is_send::&lt;LinkedList&lt;i32&gt;&gt;();
is_sync::&lt;LinkedList&lt;i32&gt;&gt;();
is_send::&lt;IntoIter&lt;i32&gt;&gt;();
is_sync::&lt;IntoIter&lt;i32&gt;&gt;();
is_send::&lt;Iter&lt;i32&gt;&gt;();
is_sync::&lt;Iter&lt;i32&gt;&gt;();
is_send::&lt;IterMut&lt;i32&gt;&gt;();
is_sync::&lt;IterMut&lt;i32&gt;&gt;();
fn linked_list_covariant&lt;'a, T&gt;(x: LinkedList&lt;&amp;'static T&gt;) -&gt; LinkedList&lt;&amp;'a T&gt; {
x
}
fn iter_covariant&lt;'i, 'a, T&gt;(x: Iter&lt;'i, &amp;'static T&gt;) -&gt; Iter&lt;'i, &amp;'a T&gt; {
x
}
fn into_iter_covariant&lt;'a, T&gt;(x: IntoIter&lt;&amp;'static T&gt;) -&gt; IntoIter&lt;&amp;'a T&gt; {
x
}
/// ```compile_fail,E0308
/// use linked_list::IterMut;
///
/// fn iter_mut_covariant&lt;'i, 'a, T&gt;(x: IterMut&lt;'i, &amp;'static T&gt;) -&gt; IterMut&lt;'i, &amp;'a T&gt; { x }
/// ```
fn iter_mut_invariant() {}
}
#[cfg(test)]
mod test {
use super::LinkedList;
fn generate_test() -&gt; LinkedList&lt;i32&gt; {
list_from(&amp;[0, 1, 2, 3, 4, 5, 6])
}
fn list_from&lt;T: Clone&gt;(v: &amp;[T]) -&gt; LinkedList&lt;T&gt; {
v.iter().map(|x| (*x).clone()).collect()
}
#[test]
fn test_basic_front() {
let mut list = LinkedList::new();
// Try to break an empty list
assert_eq!(list.len(), 0);
assert_eq!(list.pop_front(), None);
assert_eq!(list.len(), 0);
// Try to break a one item list
list.push_front(10);
assert_eq!(list.len(), 1);
assert_eq!(list.pop_front(), Some(10));
assert_eq!(list.len(), 0);
assert_eq!(list.pop_front(), None);
assert_eq!(list.len(), 0);
// Mess around
list.push_front(10);
assert_eq!(list.len(), 1);
list.push_front(20);
assert_eq!(list.len(), 2);
list.push_front(30);
assert_eq!(list.len(), 3);
assert_eq!(list.pop_front(), Some(30));
assert_eq!(list.len(), 2);
list.push_front(40);
assert_eq!(list.len(), 3);
assert_eq!(list.pop_front(), Some(40));
assert_eq!(list.len(), 2);
assert_eq!(list.pop_front(), Some(20));
assert_eq!(list.len(), 1);
assert_eq!(list.pop_front(), Some(10));
assert_eq!(list.len(), 0);
assert_eq!(list.pop_front(), None);
assert_eq!(list.len(), 0);
assert_eq!(list.pop_front(), None);
assert_eq!(list.len(), 0);
}
#[test]
fn test_basic() {
let mut m = LinkedList::new();
assert_eq!(m.pop_front(), None);
assert_eq!(m.pop_back(), None);
assert_eq!(m.pop_front(), None);
m.push_front(1);
assert_eq!(m.pop_front(), Some(1));
m.push_back(2);
m.push_back(3);
assert_eq!(m.len(), 2);
assert_eq!(m.pop_front(), Some(2));
assert_eq!(m.pop_front(), Some(3));
assert_eq!(m.len(), 0);
assert_eq!(m.pop_front(), None);
m.push_back(1);
m.push_back(3);
m.push_back(5);
m.push_back(7);
assert_eq!(m.pop_front(), Some(1));
let mut n = LinkedList::new();
n.push_front(2);
n.push_front(3);
{
assert_eq!(n.front().unwrap(), &amp;3);
let x = n.front_mut().unwrap();
assert_eq!(*x, 3);
*x = 0;
}
{
assert_eq!(n.back().unwrap(), &amp;2);
let y = n.back_mut().unwrap();
assert_eq!(*y, 2);
*y = 1;
}
assert_eq!(n.pop_front(), Some(0));
assert_eq!(n.pop_front(), Some(1));
}
#[test]
fn test_iterator() {
let m = generate_test();
for (i, elt) in m.iter().enumerate() {
assert_eq!(i as i32, *elt);
}
let mut n = LinkedList::new();
assert_eq!(n.iter().next(), None);
n.push_front(4);
let mut it = n.iter();
assert_eq!(it.size_hint(), (1, Some(1)));
assert_eq!(it.next().unwrap(), &amp;4);
assert_eq!(it.size_hint(), (0, Some(0)));
assert_eq!(it.next(), None);
}
#[test]
fn test_iterator_double_end() {
let mut n = LinkedList::new();
assert_eq!(n.iter().next(), None);
n.push_front(4);
n.push_front(5);
n.push_front(6);
let mut it = n.iter();
assert_eq!(it.size_hint(), (3, Some(3)));
assert_eq!(it.next().unwrap(), &amp;6);
assert_eq!(it.size_hint(), (2, Some(2)));
assert_eq!(it.next_back().unwrap(), &amp;4);
assert_eq!(it.size_hint(), (1, Some(1)));
assert_eq!(it.next_back().unwrap(), &amp;5);
assert_eq!(it.next_back(), None);
assert_eq!(it.next(), None);
}
#[test]
fn test_rev_iter() {
let m = generate_test();
for (i, elt) in m.iter().rev().enumerate() {
assert_eq!(6 - i as i32, *elt);
}
let mut n = LinkedList::new();
assert_eq!(n.iter().rev().next(), None);
n.push_front(4);
let mut it = n.iter().rev();
assert_eq!(it.size_hint(), (1, Some(1)));
assert_eq!(it.next().unwrap(), &amp;4);
assert_eq!(it.size_hint(), (0, Some(0)));
assert_eq!(it.next(), None);
}
#[test]
fn test_mut_iter() {
let mut m = generate_test();
let mut len = m.len();
for (i, elt) in m.iter_mut().enumerate() {
assert_eq!(i as i32, *elt);
len -= 1;
}
assert_eq!(len, 0);
let mut n = LinkedList::new();
assert!(n.iter_mut().next().is_none());
n.push_front(4);
n.push_back(5);
let mut it = n.iter_mut();
assert_eq!(it.size_hint(), (2, Some(2)));
assert!(it.next().is_some());
assert!(it.next().is_some());
assert_eq!(it.size_hint(), (0, Some(0)));
assert!(it.next().is_none());
}
#[test]
fn test_iterator_mut_double_end() {
let mut n = LinkedList::new();
assert!(n.iter_mut().next_back().is_none());
n.push_front(4);
n.push_front(5);
n.push_front(6);
let mut it = n.iter_mut();
assert_eq!(it.size_hint(), (3, Some(3)));
assert_eq!(*it.next().unwrap(), 6);
assert_eq!(it.size_hint(), (2, Some(2)));
assert_eq!(*it.next_back().unwrap(), 4);
assert_eq!(it.size_hint(), (1, Some(1)));
assert_eq!(*it.next_back().unwrap(), 5);
assert!(it.next_back().is_none());
assert!(it.next().is_none());
}
#[test]
fn test_eq() {
let mut n: LinkedList&lt;u8&gt; = list_from(&amp;[]);
let mut m = list_from(&amp;[]);
assert!(n == m);
n.push_front(1);
assert!(n != m);
m.push_back(1);
assert!(n == m);
let n = list_from(&amp;[2, 3, 4]);
let m = list_from(&amp;[1, 2, 3]);
assert!(n != m);
}
#[test]
fn test_ord() {
let n = list_from(&amp;[]);
let m = list_from(&amp;[1, 2, 3]);
assert!(n &lt; m);
assert!(m &gt; n);
assert!(n &lt;= n);
assert!(n &gt;= n);
}
#[test]
fn test_ord_nan() {
let nan = 0.0f64 / 0.0;
let n = list_from(&amp;[nan]);
let m = list_from(&amp;[nan]);
assert!(!(n &lt; m));
assert!(!(n &gt; m));
assert!(!(n &lt;= m));
assert!(!(n &gt;= m));
let n = list_from(&amp;[nan]);
let one = list_from(&amp;[1.0f64]);
assert!(!(n &lt; one));
assert!(!(n &gt; one));
assert!(!(n &lt;= one));
assert!(!(n &gt;= one));
let u = list_from(&amp;[1.0f64, 2.0, nan]);
let v = list_from(&amp;[1.0f64, 2.0, 3.0]);
assert!(!(u &lt; v));
assert!(!(u &gt; v));
assert!(!(u &lt;= v));
assert!(!(u &gt;= v));
let s = list_from(&amp;[1.0f64, 2.0, 4.0, 2.0]);
let t = list_from(&amp;[1.0f64, 2.0, 3.0, 2.0]);
assert!(!(s &lt; t));
assert!(s &gt; one);
assert!(!(s &lt;= one));
assert!(s &gt;= one);
}
#[test]
fn test_debug() {
let list: LinkedList&lt;i32&gt; = (0..10).collect();
assert_eq!(format!(&quot;{:?}&quot;, list), &quot;[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]&quot;);
let list: LinkedList&lt;&amp;str&gt; = vec![&quot;just&quot;, &quot;one&quot;, &quot;test&quot;, &quot;more&quot;]
.iter()
.copied()
.collect();
assert_eq!(format!(&quot;{:?}&quot;, list), r#&quot;[&quot;just&quot;, &quot;one&quot;, &quot;test&quot;, &quot;more&quot;]&quot;#);
}
#[test]
fn test_hashmap() {
// Check that HashMap works with this as a key
let list1: LinkedList&lt;i32&gt; = (0..10).collect();
let list2: LinkedList&lt;i32&gt; = (1..11).collect();
let mut map = std::collections::HashMap::new();
assert_eq!(map.insert(list1.clone(), &quot;list1&quot;), None);
assert_eq!(map.insert(list2.clone(), &quot;list2&quot;), None);
assert_eq!(map.len(), 2);
assert_eq!(map.get(&amp;list1), Some(&amp;&quot;list1&quot;));
assert_eq!(map.get(&amp;list2), Some(&amp;&quot;list2&quot;));
assert_eq!(map.remove(&amp;list1), Some(&quot;list1&quot;));
assert_eq!(map.remove(&amp;list2), Some(&quot;list2&quot;));
assert!(map.is_empty());
}
#[test]
fn test_cursor_move_peek() {
let mut m: LinkedList&lt;u32&gt; = LinkedList::new();
m.extend([1, 2, 3, 4, 5, 6]);
let mut cursor = m.cursor_mut();
cursor.move_next();
assert_eq!(cursor.current(), Some(&amp;mut 1));
assert_eq!(cursor.peek_next(), Some(&amp;mut 2));
assert_eq!(cursor.peek_prev(), None);
assert_eq!(cursor.index(), Some(0));
cursor.move_prev();
assert_eq!(cursor.current(), None);
assert_eq!(cursor.peek_next(), Some(&amp;mut 1));
assert_eq!(cursor.peek_prev(), Some(&amp;mut 6));
assert_eq!(cursor.index(), None);
cursor.move_next();
cursor.move_next();
assert_eq!(cursor.current(), Some(&amp;mut 2));
assert_eq!(cursor.peek_next(), Some(&amp;mut 3));
assert_eq!(cursor.peek_prev(), Some(&amp;mut 1));
assert_eq!(cursor.index(), Some(1));
let mut cursor = m.cursor_mut();
cursor.move_prev();
assert_eq!(cursor.current(), Some(&amp;mut 6));
assert_eq!(cursor.peek_next(), None);
assert_eq!(cursor.peek_prev(), Some(&amp;mut 5));
assert_eq!(cursor.index(), Some(5));
cursor.move_next();
assert_eq!(cursor.current(), None);
assert_eq!(cursor.peek_next(), Some(&amp;mut 1));
assert_eq!(cursor.peek_prev(), Some(&amp;mut 6));
assert_eq!(cursor.index(), None);
cursor.move_prev();
cursor.move_prev();
assert_eq!(cursor.current(), Some(&amp;mut 5));
assert_eq!(cursor.peek_next(), Some(&amp;mut 6));
assert_eq!(cursor.peek_prev(), Some(&amp;mut 4));
assert_eq!(cursor.index(), Some(4));
}
#[test]
fn test_cursor_mut_insert() {
let mut m: LinkedList&lt;u32&gt; = LinkedList::new();
m.extend([1, 2, 3, 4, 5, 6]);
let mut cursor = m.cursor_mut();
cursor.move_next();
cursor.splice_before(Some(7).into_iter().collect());
cursor.splice_after(Some(8).into_iter().collect());
// check_links(&amp;m);
assert_eq!(
m.iter().cloned().collect::&lt;Vec&lt;_&gt;&gt;(),
&amp;[7, 1, 8, 2, 3, 4, 5, 6]
);
let mut cursor = m.cursor_mut();
cursor.move_next();
cursor.move_prev();
cursor.splice_before(Some(9).into_iter().collect());
cursor.splice_after(Some(10).into_iter().collect());
check_links(&amp;m);
assert_eq!(
m.iter().cloned().collect::&lt;Vec&lt;_&gt;&gt;(),
&amp;[10, 7, 1, 8, 2, 3, 4, 5, 6, 9]
);
/* remove_current not impl'd
let mut cursor = m.cursor_mut();
cursor.move_next();
cursor.move_prev();
assert_eq!(cursor.remove_current(), None);
cursor.move_next();
cursor.move_next();
assert_eq!(cursor.remove_current(), Some(7));
cursor.move_prev();
cursor.move_prev();
cursor.move_prev();
assert_eq!(cursor.remove_current(), Some(9));
cursor.move_next();
assert_eq!(cursor.remove_current(), Some(10));
check_links(&amp;m);
assert_eq!(m.iter().cloned().collect::&lt;Vec&lt;_&gt;&gt;(), &amp;[1, 8, 2, 3, 4, 5, 6]);
*/
let mut m: LinkedList&lt;u32&gt; = LinkedList::new();
m.extend([1, 8, 2, 3, 4, 5, 6]);
let mut cursor = m.cursor_mut();
cursor.move_next();
let mut p: LinkedList&lt;u32&gt; = LinkedList::new();
p.extend([100, 101, 102, 103]);
let mut q: LinkedList&lt;u32&gt; = LinkedList::new();
q.extend([200, 201, 202, 203]);
cursor.splice_after(p);
cursor.splice_before(q);
check_links(&amp;m);
assert_eq!(
m.iter().cloned().collect::&lt;Vec&lt;_&gt;&gt;(),
&amp;[200, 201, 202, 203, 1, 100, 101, 102, 103, 8, 2, 3, 4, 5, 6]
);
let mut cursor = m.cursor_mut();
cursor.move_next();
cursor.move_prev();
let tmp = cursor.split_before();
assert_eq!(m.into_iter().collect::&lt;Vec&lt;_&gt;&gt;(), &amp;[]);
m = tmp;
let mut cursor = m.cursor_mut();
cursor.move_next();
cursor.move_next();
cursor.move_next();
cursor.move_next();
cursor.move_next();
cursor.move_next();
cursor.move_next();
let tmp = cursor.split_after();
assert_eq!(
tmp.into_iter().collect::&lt;Vec&lt;_&gt;&gt;(),
&amp;[102, 103, 8, 2, 3, 4, 5, 6]
);
check_links(&amp;m);
assert_eq!(
m.iter().cloned().collect::&lt;Vec&lt;_&gt;&gt;(),
&amp;[200, 201, 202, 203, 1, 100, 101]
);
}
fn check_links&lt;T: Eq + std::fmt::Debug&gt;(list: &amp;LinkedList&lt;T&gt;) {
let from_front: Vec&lt;_&gt; = list.iter().collect();
let from_back: Vec&lt;_&gt; = list.iter().rev().collect();
let re_reved: Vec&lt;_&gt; = from_back.into_iter().rev().collect();
assert_eq!(from_front, re_reved);
}
}
<span class="boring">}</span></code></pre></pre>
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