我建议你看看Lars Bergstrom写的Rust patterns.
以下是实现双链接列表的代码,更新自@Yurume的Rust 1.12(未完全测试)
use std::mem;
use std::ptr;
pub struct List<T> {
list_head: Option<Box<Node<T>>>,
list_tail: Rawlink<Node<T>>,
}
struct Rawlink<T> { p: *mut T }
impl<T> Copy for Rawlink<T> {}
impl<T> Clone for Rawlink<T> {
fn clone(&self) -> Self { Rawlink { p: self.p } }
}
pub struct Node<T> {
next: Option<Box<Node<T>>>,
prev: Rawlink<Node<T>>,
value: T,
}
impl<T> List<T> {
pub fn is_empty(&self) -> bool {
self.list_head.is_none()
}
pub fn len(&self) -> usize {
let mut node = &self.list_head;
let mut i = 0;
loop {
match *node {
Some(ref n) => {
i+=1;
node=&n.next;
}
None => {
return i;
}
}
}
}
/// Create an empty DList
pub fn new() -> List<T> {
List{list_head: None, list_tail: Rawlink::none()}
}
pub fn push_front(&mut self, elt: T) {
self.push_front_node(Box::new(Node::new(elt)))
}
pub fn push_front_node(&mut self, mut new_head: Box<Node<T>>) {
match self.list_head {
None => {
self.list_tail = Rawlink::some(&mut new_head);
new_head.prev = Rawlink::none();
self.list_head = Some(new_head);
}
Some(ref mut head) => {
new_head.prev = Rawlink::none();
head.prev = Rawlink::some(&mut new_head);
mem::swap(head, &mut new_head);
head.next = Some(new_head);
}
}
}
/// Provide a forward iterator
#[inline]
pub fn iter<'a>(&'a self) -> ListIterator<'a, T> {
ListIterator{nelem: self.len(), head: &self.list_head, tail: self.list_tail}
}
}
impl<T> Node<T> {
fn new(v: T) -> Node<T> {
Node{value: v, next: None, prev: Rawlink::none()}
}
}
/// Rawlink is a type like Option<T> but for holding a raw pointer
impl<T> Rawlink<T> {
/// Like Option::None for Rawlink
fn none() -> Rawlink<T> {
Rawlink{p: ptr::null_mut()}
}
/// Like Option::Some for Rawlink
fn some(n: &mut T) -> Rawlink<T> {
Rawlink{p: n as *mut T}
}
/// Convert the `Rawlink` into an Option value
fn resolve_immut<'a>(&self) -> Option<&'a T> {
unsafe { self.p.as_ref() }
}
/// Convert the `Rawlink` into an Option value
fn resolve<'a>(&mut self) -> Option<&'a mut T> {
unsafe { self.p.as_mut() }
}
/// Return the `Rawlink` and replace with `Rawlink::none()`
fn take(&mut self) -> Rawlink<T> {
mem::replace(self, Rawlink::none())
}
}
pub struct ListIterator<'a, T: 'a> {
head: &'a Option<Box<Node<T>>>,
tail: Rawlink<Node<T>>,
nelem: usize,
}
impl<'a, A> Iterator for ListIterator<'a, A> {
type Item = &'a A;
#[inline]
fn next(&mut self) -> Option<&'a A> {
if self.nelem == 0 {
return None;
}
self.head.as_ref().map(|head| {
self.nelem -= 1;
self.head = &head.next;
&head.value
})
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
(self.nelem, Some(self.nelem))
}
}
impl<'a, A> DoubleEndedIterator for ListIterator<'a, A> {
#[inline]
fn next_back(&mut self) -> Option<&'a A> {
if self.nelem == 0 {
return None;
}
let tmp = self.tail.resolve_immut();
tmp.as_ref().map(|prev| {
self.nelem -= 1;
self.tail = prev.prev;
&prev.value
})
}
}
fn main() {
}
Playground