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<main>
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<h1 id="filling-in-random-bits"><a class="header" href="#filling-in-random-bits">Filling In Random Bits</a></h1>
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<p>嘿，你不是说要做成精品吗？</p>
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<p>为了成为一个 "好 "系列，这里还有一些乱七八糟的东西：</p>
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<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
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</span><span class="boring">fn main() {
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</span>impl<T> LinkedList<T> {
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pub fn is_empty(&self) -> bool {
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self.len == 0
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}
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pub fn clear(&mut self) {
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// Oh look it's drop again
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while let Some(_) = self.pop_front() { }
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}
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}
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<span class="boring">}</span></code></pre></pre>
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<p>现在，我们已经有了一大堆大家都期待的特性需要实现：</p>
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<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
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</span><span class="boring">fn main() {
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</span>impl<T> Default for LinkedList<T> {
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fn default() -> Self {
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Self::new()
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}
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}
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impl<T: Clone> Clone for LinkedList<T> {
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fn clone(&self) -> Self {
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let mut new_list = Self::new();
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for item in self {
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new_list.push_back(item.clone());
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}
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new_list
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}
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}
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impl<T> Extend<T> for LinkedList<T> {
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fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
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for item in iter {
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self.push_back(item);
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}
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}
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}
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impl<T> FromIterator<T> for LinkedList<T> {
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fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
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let mut list = Self::new();
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list.extend(iter);
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list
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}
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}
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impl<T: Debug> Debug for LinkedList<T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_list().entries(self).finish()
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}
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}
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||
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impl<T: PartialEq> PartialEq for LinkedList<T> {
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fn eq(&self, other: &Self) -> bool {
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self.len() == other.len() && self.iter().eq(other)
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}
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fn ne(&self, other: &Self) -> bool {
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self.len() != other.len() || self.iter().ne(other)
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}
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}
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impl<T: Eq> Eq for LinkedList<T> { }
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impl<T: PartialOrd> PartialOrd for LinkedList<T> {
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fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
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self.iter().partial_cmp(other)
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}
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}
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impl<T: Ord> Ord for LinkedList<T> {
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fn cmp(&self, other: &Self) -> Ordering {
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self.iter().cmp(other)
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}
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}
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impl<T: Hash> Hash for LinkedList<T> {
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fn hash<H: Hasher>(&self, state: &mut H) {
|
||
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self.len().hash(state);
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||
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for item in self {
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||
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item.hash(state);
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}
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}
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}
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<span class="boring">}</span></code></pre></pre>
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|
|
<p>另一个有趣的话题是哈希本身。你看到我们如何将 <code>len</code> 写入散列的吗？这其实非常重要！如果集合不把 <code>len</code> 加入散列，很可能会意外的造成前缀碰撞。例如，一个集合包含 <code>["he", "llo"]</code> 另一个集合包含 <code>["hello"]</code>，我们该如何区分？如果没有把集合长度或其它"分隔符"加入到散列 ，这将毫无意义！会让意外哈希碰撞发生变得太容易，会导致严重的后果，所以还是照做吧！</p>
|
||
|
|
<p>好了，这是我们现在的代码：</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::ptr::NonNull;
|
||
|
|
use std::marker::PhantomData;
|
||
|
|
|
||
|
|
pub struct LinkedList<T> {
|
||
|
|
front: Link<T>,
|
||
|
|
back: Link<T>,
|
||
|
|
len: usize,
|
||
|
|
_boo: PhantomData<T>,
|
||
|
|
}
|
||
|
|
|
||
|
|
type Link<T> = Option<NonNull<Node<T>>>;
|
||
|
|
|
||
|
|
struct Node<T> {
|
||
|
|
front: Link<T>,
|
||
|
|
back: Link<T>,
|
||
|
|
elem: T,
|
||
|
|
}
|
||
|
|
|
||
|
|
pub struct Iter<'a, T> {
|
||
|
|
front: Link<T>,
|
||
|
|
back: Link<T>,
|
||
|
|
len: usize,
|
||
|
|
_boo: PhantomData<&'a T>,
|
||
|
|
}
|
||
|
|
|
||
|
|
pub struct IterMut<'a, T> {
|
||
|
|
front: Link<T>,
|
||
|
|
back: Link<T>,
|
||
|
|
len: usize,
|
||
|
|
_boo: PhantomData<&'a mut T>,
|
||
|
|
}
|
||
|
|
|
||
|
|
pub struct IntoIter<T> {
|
||
|
|
list: LinkedList<T>,
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T> LinkedList<T> {
|
||
|
|
pub fn new() -> Self {
|
||
|
|
Self {
|
||
|
|
front: None,
|
||
|
|
back: None,
|
||
|
|
len: 0,
|
||
|
|
_boo: PhantomData,
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn push_front(&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(&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(&mut self) -> Option<T> {
|
||
|
|
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(&mut self) -> Option<T> {
|
||
|
|
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(&self) -> Option<&T> {
|
||
|
|
unsafe {
|
||
|
|
self.front.map(|node| &(*node.as_ptr()).elem)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn front_mut(&mut self) -> Option<&mut T> {
|
||
|
|
unsafe {
|
||
|
|
self.front.map(|node| &mut (*node.as_ptr()).elem)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn back(&self) -> Option<&T> {
|
||
|
|
unsafe {
|
||
|
|
self.back.map(|node| &(*node.as_ptr()).elem)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn back_mut(&mut self) -> Option<&mut T> {
|
||
|
|
unsafe {
|
||
|
|
self.back.map(|node| &mut (*node.as_ptr()).elem)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn len(&self) -> usize {
|
||
|
|
self.len
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn is_empty(&self) -> bool {
|
||
|
|
self.len == 0
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn clear(&mut self) {
|
||
|
|
// Oh look it's drop again
|
||
|
|
while let Some(_) = self.pop_front() { }
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn iter(&self) -> Iter<T> {
|
||
|
|
Iter {
|
||
|
|
front: self.front,
|
||
|
|
back: self.back,
|
||
|
|
len: self.len,
|
||
|
|
_boo: PhantomData,
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn iter_mut(&mut self) -> IterMut<T> {
|
||
|
|
IterMut {
|
||
|
|
front: self.front,
|
||
|
|
back: self.back,
|
||
|
|
len: self.len,
|
||
|
|
_boo: PhantomData,
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
pub fn into_iter(self) -> IntoIter<T> {
|
||
|
|
IntoIter {
|
||
|
|
list: self
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T> Drop for LinkedList<T> {
|
||
|
|
fn drop(&mut self) {
|
||
|
|
// Pop until we have to stop
|
||
|
|
while let Some(_) = self.pop_front() { }
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T> Default for LinkedList<T> {
|
||
|
|
fn default() -> Self {
|
||
|
|
Self::new()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T: Clone> Clone for LinkedList<T> {
|
||
|
|
fn clone(&self) -> Self {
|
||
|
|
let mut new_list = Self::new();
|
||
|
|
for item in self {
|
||
|
|
new_list.push_back(item.clone());
|
||
|
|
}
|
||
|
|
new_list
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T> Extend<T> for LinkedList<T> {
|
||
|
|
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
|
||
|
|
for item in iter {
|
||
|
|
self.push_back(item);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
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
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T: Debug> Debug for LinkedList<T> {
|
||
|
|
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
|
|
f.debug_list().entries(self).finish()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T: PartialEq> PartialEq for LinkedList<T> {
|
||
|
|
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)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T: Eq> Eq for LinkedList<T> { }
|
||
|
|
|
||
|
|
impl<T: PartialOrd> PartialOrd for LinkedList<T> {
|
||
|
|
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
|
||
|
|
self.iter().partial_cmp(other)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T: Ord> Ord for LinkedList<T> {
|
||
|
|
fn cmp(&self, other: &Self) -> Ordering {
|
||
|
|
self.iter().cmp(other)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T: Hash> Hash for LinkedList<T> {
|
||
|
|
fn hash<H: Hasher>(&self, state: &mut H) {
|
||
|
|
self.len().hash(state);
|
||
|
|
for item in self {
|
||
|
|
item.hash(state);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<'a, T> IntoIterator for &'a LinkedList<T> {
|
||
|
|
type IntoIter = Iter<'a, T>;
|
||
|
|
type Item = &'a T;
|
||
|
|
|
||
|
|
fn into_iter(self) -> Self::IntoIter {
|
||
|
|
self.iter()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<'a, T> Iterator for Iter<'a, T> {
|
||
|
|
type Item = &'a T;
|
||
|
|
|
||
|
|
fn next(&mut self) -> Option<Self::Item> {
|
||
|
|
// 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 "one-past-the-end" pointers.
|
||
|
|
if self.len > 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;
|
||
|
|
&(*node.as_ptr()).elem
|
||
|
|
})
|
||
|
|
} else {
|
||
|
|
None
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
|
|
(self.len, Some(self.len))
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
|
||
|
|
fn next_back(&mut self) -> Option<Self::Item> {
|
||
|
|
if self.len > 0 {
|
||
|
|
self.back.map(|node| unsafe {
|
||
|
|
self.len -= 1;
|
||
|
|
self.back = (*node.as_ptr()).front;
|
||
|
|
&(*node.as_ptr()).elem
|
||
|
|
})
|
||
|
|
} else {
|
||
|
|
None
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<'a, T> ExactSizeIterator for Iter<'a, T> {
|
||
|
|
fn len(&self) -> usize {
|
||
|
|
self.len
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<'a, T> IntoIterator for &'a mut LinkedList<T> {
|
||
|
|
type IntoIter = IterMut<'a, T>;
|
||
|
|
type Item = &'a mut T;
|
||
|
|
|
||
|
|
fn into_iter(self) -> Self::IntoIter {
|
||
|
|
self.iter_mut()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<'a, T> Iterator for IterMut<'a, T> {
|
||
|
|
type Item = &'a mut T;
|
||
|
|
|
||
|
|
fn next(&mut self) -> Option<Self::Item> {
|
||
|
|
// 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 "one-past-the-end" pointers.
|
||
|
|
if self.len > 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;
|
||
|
|
&mut (*node.as_ptr()).elem
|
||
|
|
})
|
||
|
|
} else {
|
||
|
|
None
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
|
|
(self.len, Some(self.len))
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<'a, T> DoubleEndedIterator for IterMut<'a, T> {
|
||
|
|
fn next_back(&mut self) -> Option<Self::Item> {
|
||
|
|
if self.len > 0 {
|
||
|
|
self.back.map(|node| unsafe {
|
||
|
|
self.len -= 1;
|
||
|
|
self.back = (*node.as_ptr()).front;
|
||
|
|
&mut (*node.as_ptr()).elem
|
||
|
|
})
|
||
|
|
} else {
|
||
|
|
None
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<'a, T> ExactSizeIterator for IterMut<'a, T> {
|
||
|
|
fn len(&self) -> usize {
|
||
|
|
self.len
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T> IntoIterator for LinkedList<T> {
|
||
|
|
type IntoIter = IntoIter<T>;
|
||
|
|
type Item = T;
|
||
|
|
|
||
|
|
fn into_iter(self) -> Self::IntoIter {
|
||
|
|
self.into_iter()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T> Iterator for IntoIter<T> {
|
||
|
|
type Item = T;
|
||
|
|
|
||
|
|
fn next(&mut self) -> Option<Self::Item> {
|
||
|
|
self.list.pop_front()
|
||
|
|
}
|
||
|
|
|
||
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
||
|
|
(self.list.len, Some(self.list.len))
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T> DoubleEndedIterator for IntoIter<T> {
|
||
|
|
fn next_back(&mut self) -> Option<Self::Item> {
|
||
|
|
self.list.pop_back()
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
impl<T> ExactSizeIterator for IntoIter<T> {
|
||
|
|
fn len(&self) -> usize {
|
||
|
|
self.list.len
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
#[cfg(test)]
|
||
|
|
mod test {
|
||
|
|
use super::LinkedList;
|
||
|
|
|
||
|
|
#[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);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
<span class="boring">}</span></code></pre></pre>
|
||
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