From e9a51f8d528bd158b4caba4a96b875dd35d56725 Mon Sep 17 00:00:00 2001
From: Nilstrieb <nilstrieb@gmail.com>
Date: Sat, 7 Aug 2021 18:27:54 +0200
Subject: [PATCH] actually works lol

---
 src/linked_list.rs | 245 +++++++++++++++++++++++++++++----------------
 1 file changed, 157 insertions(+), 88 deletions(-)

diff --git a/src/linked_list.rs b/src/linked_list.rs
index dd3295e..b4404db 100644
--- a/src/linked_list.rs
+++ b/src/linked_list.rs
@@ -1,116 +1,149 @@
-use std::fmt::Debug;
+use std::fmt::{Debug, Formatter};
+use std::marker::PhantomData;
 use std::ptr::NonNull;
 
-type NodePtr<T> = Option<NonNull<Node<T>>>;
-
 /// A doubly linked list with unsafe :O, except it's kind of shit compared to the std one
-#[derive(Debug)]
 pub struct LinkedList<T> {
     start: Option<NonNull<Node<T>>>,
     end: Option<NonNull<Node<T>>>,
+    _maker: PhantomData<T>,
 }
 
-impl<T> Clone for LinkedList<T>
+impl<T> LinkedList<T> {
+    /// Creates a new empty Linked List
+    pub fn new() -> LinkedList<T> {
+        std::collections::LinkedList::new().push_front("hi");
+        Self {
+            start: None,
+            end: None,
+            _maker: PhantomData,
+        }
+    }
+
+    /// Prepend an element to the start of the list
+    pub fn push_front(&mut self, element: T) {
+        match self.start {
+            // empty list
+            None => {
+                let node = allocate_nonnull(Node {
+                    value: element,
+                    next: None,
+                    prev: None,
+                    _maker: PhantomData,
+                });
+                self.start = Some(node);
+                self.end = Some(node);
+            }
+            // at lest one element
+            Some(mut node) => {
+                let new = allocate_nonnull(Node {
+                    value: element,
+                    next: Some(node),
+                    prev: None,
+                    _maker: PhantomData,
+                });
+                // SAFETY: All pointers should always be valid
+                unsafe { node.as_mut() }.prev = Some(new);
+                self.start = Some(new);
+            }
+        }
+    }
+
+    pub fn insert_end(&mut self, element: T) {}
+
+    /// Random access over the list
+    pub fn get(&self, index: usize) -> Option<&T> {
+        fn get_inner<T2>(node: Option<&NonNull<Node<T2>>>, index: usize) -> Option<&Node<T2>> {
+            match node {
+                // SAFETY: All pointers should always be valid
+                Some(ptr) => match index {
+                    0 => unsafe { Some(ptr.as_ref()) },
+                    n => get_inner(unsafe { ptr.as_ref() }.next.as_ref(), n - 1),
+                },
+                None => None,
+            }
+        }
+        get_inner(self.start.as_ref(), index).map(|n| &n.value)
+    }
+
+    pub fn get_node(&self, index: usize) {}
+
+    /// Returns an iterator over the items
+    pub fn iter(&self) -> Iter<T> {
+        Iter::new(self)
+    }
+}
+
+impl<T> Debug for LinkedList<T>
 where
-    T: Clone,
+    T: Debug,
 {
-    fn clone(&self) -> Self {
-        todo!()
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.debug_list().entries(self.iter()).finish()
+    }
+}
+
+impl<T> Drop for LinkedList<T> {
+    fn drop(&mut self) {
+        let mut item = self.start;
+        while let Some(content) = item {
+            // SAFETY: All pointers should always be valid and created from a box
+            unsafe {
+                item = content.as_ref().next;
+                Box::from_raw(content.as_ptr());
+            }
+        }
     }
 }
 
 #[derive(Debug)]
 pub struct Node<T> {
     value: T,
-    next: NodePtr<T>,
-    prev: NodePtr<T>,
-}
-
-impl<T> LinkedList<T> {
-    /// Creates a new empty Linked List
-    pub fn new() -> LinkedList<T> {
-        Self {
-            start: None,
-            end: None,
-        }
-    }
-
-    /// Prepend an element to the start of the list
-    pub fn prepend(&mut self, element: T) {
-        match self.start {
-            None => {
-                let node = allocate_nonnull(Node {
-                    value: element,
-                    next: None,
-                    prev: None,
-                });
-                self.start = Some(node);
-                self.end = Some(node);
-            }
-            Some(mut node) => {
-                let new = allocate_nonnull(Node {
-                    value: element,
-                    next: Some(node),
-                    prev: None,
-                });
-                unsafe { node.as_mut() }.prev = Some(new);
-            }
-        }
-    }
-
-    /// Random access over the list
-    pub fn get(&self, index: usize) -> Option<&T> {
-        dbg!(self);
-        Self::get_inner(self.start.as_ref(), index).map(|n| &n.value)
-    }
-
-    fn get_inner(node: Option<&NonNull<Node<T>>>, index: usize) -> Option<&Node<T>> {
-        if let Some(ptr) = node {
-            match index {
-                0 => unsafe { Some(ptr.as_ref()) },
-                n => LinkedList::get_inner(Some(ptr), n - 1),
-            }
-        } else {
-            None
-        }
-    }
+    next: Option<NonNull<Node<T>>>,
+    prev: Option<NonNull<Node<T>>>,
+    _maker: PhantomData<T>,
 }
 
 fn allocate_nonnull<T>(element: T) -> NonNull<T> {
     let mut boxed = Box::new(element);
-    NonNull::new(boxed.as_mut()).expect("Allocation returned null pointer")
+    // SAFETY: box is always non-null
+    unsafe { NonNull::new_unchecked(Box::leak(boxed)) }
 }
 
-impl<T> IntoIterator for LinkedList<T> {
-    type Item = T;
-    type IntoIter = IntoIter<T>;
+pub struct Iter<'a, T> {
+    item: Option<&'a Node<T>>,
+}
 
-    fn into_iter(self) -> Self::IntoIter {
-        todo!()
+impl<'a, T> Iter<'a, T> {
+    fn new(list: &'a LinkedList<T>) -> Self {
+        Self {
+            item: match list.start {
+                // SAFETY: All pointers should always be valid, the list lives as long as its items
+                Some(ref nn) => unsafe { Some(nn.as_ref()) },
+                None => None,
+            },
+        }
     }
 }
 
-pub struct IntoIter<T> {
-    item: NodePtr<T>,
-}
-
-impl<T> IntoIter<T> {
-    fn new(list: LinkedList<T>) -> Self {
-        Self { item: list.start }
-    }
-}
-
-impl<T> Iterator for IntoIter<T> {
-    type Item = T;
+impl<'a, T: Debug> Iterator for Iter<'a, T> {
+    type Item = &'a T;
 
     fn next(&mut self) -> Option<Self::Item> {
-        //let next = self.item.take();
-        //let ptr = match next {
-        //    None => return None,
-        //    Some(mut ptr) => unsafe { ptr.as_mut() },
-        //};
-
-        todo!()
+        let current = self.item;
+        match current {
+            Some(node) => {
+                self.item = match &node.next {
+                    Some(ref nn) => {
+                        // SAFETY: All pointers should always be valid
+                        unsafe { Some(nn.as_ref()) }
+                    }
+                    None => None,
+                };
+                Some(&node.value)
+            }
+            None => None,
+        }
     }
 }
 
@@ -121,12 +154,48 @@ mod test {
     #[test]
     fn random_access() {
         let mut list = LinkedList::new();
-        list.prepend("hallo");
-        list.prepend("test");
-        list.prepend("nice");
+        list.push_front("hallo");
+        list.push_front("test");
+        list.push_front("nice");
         assert_eq!(list.get(0), Some(&"nice"));
         assert_eq!(list.get(1), Some(&"test"));
         assert_eq!(list.get(2), Some(&"hallo"));
         assert_eq!(list.get(3), None);
     }
+
+    #[test]
+    fn iter_simple() {
+        let mut list = LinkedList::new();
+        list.push_front("hallo");
+        list.push_front("test");
+        list.push_front("nice");
+        let mut iter = list.iter();
+        assert_eq!(iter.next(), Some(&"nice"));
+        assert_eq!(iter.next(), Some(&"test"));
+        let val = iter.next();
+        assert_eq!(val, Some(&"hallo"));
+        assert_eq!(iter.next(), None);
+    }
+
+    #[test]
+    fn iterator() {
+        let mut list = LinkedList::new();
+        list.push_front("hallo");
+        list.push_front("test");
+        list.push_front("nice");
+        let vec = list.iter().collect::<Vec<_>>();
+        assert_eq!(vec[0], &"nice");
+        assert_eq!(vec[1], &"test");
+        assert_eq!(vec[2], &"hallo");
+        assert_eq!(vec.get(3), None);
+    }
+
+    #[test]
+    fn get_large_number() {
+        let mut list = LinkedList::new();
+        for i in 0..1000000 {
+            list.push_front(i);
+        }
+        assert_eq!(list.get(999999), Some(&0));
+    }
 }