add blank linkedlist impl

c_os/user/lib/LinkedList.h

@@ -0,0 +1,74 @@
+#ifndef __LinkedLIST_INCLUDE_H_
+#define __LinkedLIST_INCLUDE_H_
+
+#include "user/lib/List.h"
+#include <cstddef>
+
+template<typename T>
+class Wrapper {
+public:
+    Wrapper(T value) : value(value) {}
+
+    T value;
+    Wrapper<T>* next;
+    Wrapper<T>* prev;
+
+    // Allow implicit conversion to make the ListIterator dereferencing work
+    operator T() {
+        return value;
+    }
+};
+
+// Implement linked traversal by extending the ListIterator
+template<typename T>
+class LinkedListIterator : public ListIterator<T> {
+public:
+    LinkedListIterator& operator++() override {
+        // ptr is of type Wrapper<T>*
+        this->ptr = this->ptr->next;
+        return *this;
+    }
+};
+
+template<typename T>
+class LinkedList : public List<Wrapper<T>, LinkedListIterator<Wrapper<T>>> {
+public:
+    using Type = typename List<Wrapper<T>, LinkedListIterator<Wrapper<T>>>::Type;  // T is different from the List type (Wrapper<T>)
+                                                                                   // so take the type out of the base class
+    using Iterator = typename List<Wrapper<T>, LinkedListIterator<Wrapper<T>>>::Iterator;
+
+private:
+    Type* head;
+    Type* tail;
+
+protected:
+    Type* begin_ptr() override {
+        return this->head;
+    }
+
+    Type* end_ptr() override {
+        return this->tail->next;
+    }
+
+public:
+    LinkedList() : head(NULL), tail(NULL) {}
+
+    unsigned int insert(Type e) override {}
+    unsigned int insert_at(Type e, unsigned int i) override {}
+
+    Type remove_at(unsigned int i) override {}
+    Type remove_first() override {}
+    Type remove_last() override {}
+    bool remove(Type e) override {}
+
+    Type get(unsigned int i) const override {}
+    Type first() const override {}
+    Type last() const override {}
+
+    bool empty() const override {}
+    unsigned int size() const override {}
+
+    void print(OutStream& out) const override {}
+};
+
+#endif