+++ /dev/null
-// Rust-101, Part 16: Unsafe Rust, Drop
-// ====================================
-
-use std::ptr;
-use std::mem;
-use std::marker::PhantomData;
-
-
-// A node of the list consists of the data, and two node pointers for the predecessor and successor.
-struct Node<T> {
- next: NodePtr<T>,
- prev: NodePtr<T>,
- data: T,
-}
-// A node pointer is a *mutable raw pointer* to a node.
-type NodePtr<T> = *mut Node<T>;
-
-// The linked list itself stores pointers to the first and the last node. In addition, we tell Rust that this type
-// will own data of type `T`.
-pub struct LinkedList<T> {
- first: NodePtr<T>,
- last: NodePtr<T>,
- _marker: PhantomData<T>,
-}
-
-
-unsafe fn raw_into_box<T>(r: *mut T) -> Box<T> {
- mem::transmute(r)
-}
-fn box_into_raw<T>(b: Box<T>) -> *mut T {
- unsafe { mem::transmute(b) }
-}
-
-impl<T> LinkedList<T> {
- // A new linked list just contains null pointers. `PhantomData` is how we construct any `PhantomData<T>`.
- pub fn new() -> Self {
- LinkedList { first: ptr::null_mut(), last: ptr::null_mut(), _marker: PhantomData }
- }
-
- // This function adds a new node to the end of the list.
- pub fn push_back(&mut self, t: T) {
- // Create the new node, and make it a raw pointer.
- let new = Box::new( Node { data: t, next: ptr::null_mut(), prev: self.last } );
- let new = box_into_raw(new);
- // Update other pointers to this node.
- if self.last.is_null() {
- debug_assert!(self.first.is_null());
- // The list is currently empty, so we have to update the head pointer.
- unimplemented!()
- } else {
- debug_assert!(!self.first.is_null());
- // We have to update the `next` pointer of the tail node.
- unimplemented!()
- }
- // Make this the last node.
- self.last = new;
- }
-
- // **Exercise 16.1**: Add some more operations to `LinkedList`: `pop_back`, `push_front` and `pop_front`.
- // Add testcases for `push_back` and all of your functions. The `pop` functions should take `&mut self`
- // and return `Option<T>`.
-
- // Next, we are going to provide an iterator.
- pub fn iter_mut(&mut self) -> IterMut<T> {
- IterMut { next: self.first, _marker: PhantomData }
- }
-}
-
-
-pub struct IterMut<'a, T> where T: 'a {
- next: NodePtr<T>,
- _marker: PhantomData<&'a mut LinkedList<T>>,
-}
-
-impl<'a, T> Iterator for IterMut<'a, T> {
- type Item = &'a mut T;
-
- fn next(&mut self) -> Option<Self::Item> {
- // The actual iteration is straight-forward: Once we reached a null pointer, we are done.
- if self.next.is_null() {
- None
- } else {
- // Otherwise, we can convert the next pointer to a reference, get a reference to the data
- // and update the iterator.
- let next = unsafe { &mut *self.next };
- let ret = &mut next.data;
- unimplemented!()
- }
- }
-}
-
-
-// **Exercise 16.2**: Add a method `iter` and a type `Iter` providing iteration for shared references.
-// Add testcases for both kinds of iterators.
-
-// ## `Drop`
-
-impl<T> Drop for LinkedList<T> {
- // The destructor itself is a method which takes `self` in mutably borrowed form. It cannot own `self`, because then
- // the destructor of `self` would be called at the end of the function, resulting in endless recursion.
- fn drop(&mut self) {
- let mut cur_ptr = self.first;
- while !cur_ptr.is_null() {
- // In the destructor, we just iterate over the entire list, successively obtaining ownership
- // (`Box`) of every node. When the box is dropped, it will call the destructor on `data` if
- // necessary, and subsequently free the node on the heap.
- let cur = unsafe { raw_into_box(cur_ptr) };
- cur_ptr = cur.next;
- drop(cur);
- }
- }
-}
-
-// ## The End
-
projects / rust-101.git / blobdiff