implement linked list

c_os/user/lib/LinkedList.h

@@ -6,15 +6,17 @@
 
 template<typename T>
 class Wrapper {
+private:
+    T value = NULL;
+
 public:
     Wrapper(T value) : value(value) {}
 
-    T value;
+    Wrapper<T>* next = NULL;
-    Wrapper<T>* next;
+    Wrapper<T>* prev = NULL;
-    Wrapper<T>* prev;
 
-    // Allow implicit conversion to make the ListIterator dereferencing work
+    // Allow conversion to make the ListIterator dereferencing work
-    operator T() {
+    explicit operator T() {
         return value;
     }
 };
@@ -23,6 +25,8 @@ public:
 template<typename T>
 class LinkedListIterator : public ListIterator<T> {
 public:
+    using Type = typename ListIterator<T>::Type;
+
     LinkedListIterator& operator++() override {
         // ptr is of type Wrapper<T>*
         this->ptr = this->ptr->next;
@@ -31,44 +35,237 @@ public:
 };
 
 template<typename T>
-class LinkedList : public List<Wrapper<T>, LinkedListIterator<Wrapper<T>>> {
+class LinkedList : public List<T, LinkedListIterator<Wrapper<T>>> {
 public:
-    using Type = typename List<Wrapper<T>, LinkedListIterator<Wrapper<T>>>::Type;  // T is different from the List type (Wrapper<T>)
+    // Type is T
-                                                                                   // so take the type out of the base class
+    using Type = typename List<T, LinkedListIterator<Wrapper<T>>>::Type;  // T is different from the List type (Wrapper<T>)
-    using Iterator = typename List<Wrapper<T>, LinkedListIterator<Wrapper<T>>>::Iterator;
+    using Iterator = typename List<T, LinkedListIterator<Wrapper<T>>>::Iterator;
 
 private:
-    Type* head;
+    unsigned int num_elements = 0;
-    Type* tail;
+    typename Iterator::Type* head = NULL;
+    typename Iterator::Type* tail = NULL;
+
+    typename Iterator::Type* get_wrapper(unsigned int i) {
+        typename Iterator::Type* current = this->head;
+        unsigned int pos = 0;
+        while (current != NULL) {
+            if (pos == i) {
+                return current;
+            }
+
+            current = current->next;
+            pos = pos + 1;
+        }
+
+        return NULL;
+    }
 
 protected:
-    Type* begin_ptr() override {
+    typename Iterator::Type* begin_ptr() override {
         return this->head;
     }
 
-    Type* end_ptr() override {
+    typename Iterator::Type* end_ptr() override {
         return this->tail->next;
     }
 
 public:
-    LinkedList() : head(NULL), tail(NULL) {}
+    unsigned int insert_at(Type e, unsigned int i) override {
+        if (i > this->size()) {
+            return -1;
+        }
 
-    unsigned int insert(Type e) override {}
+        if (i == 0) {
-    unsigned int insert_at(Type e, unsigned int i) override {}
+            return this->insert_first(e);
+        }
 
-    Type remove_at(unsigned int i) override {}
+        if (i == this->size()) {
-    Type remove_first() override {}
+            return this->insert_last(e);
-    Type remove_last() override {}
+        }
-    bool remove(Type e) override {}
 
-    Type get(unsigned int i) const override {}
+        typename Iterator::Type* old_e = this->get_wrapper(i);
-    Type first() const override {}
+        typename Iterator::Type* new_e = new typename Iterator::Type(e);
-    Type last() const override {}
 
-    bool empty() const override {}
+        new_e->prev = old_e->prev;
-    unsigned int size() const override {}
+        new_e->next = old_e;
+        new_e->prev->next = new_e;
+        new_e->next->prev = new_e;
 
-    void print(OutStream& out) const override {}
+        this->num_elements = this->num_elements + 1;
+        return this->size();
+    }
+
+    unsigned int insert_first(Type e) override {
+        typename Iterator::Type* old_head = this->head;
+        this->head = new typename Iterator::Type(e);
+
+        this->head->prev = NULL;
+        this->head->next = old_head;
+        if (old_head != NULL) {
+            old_head->prev = this->head;
+        }
+
+        if (this->tail == NULL) {
+            this->tail = this->head;
+        }
+
+        this->num_elements = this->num_elements + 1;
+        return this->size();
+    }
+
+    unsigned int insert_last(Type e) override {
+        typename Iterator::Type* old_tail = this->tail;
+        this->tail = new typename Iterator::Type(e);
+
+        this->tail->next = NULL;
+        this->tail->prev = old_tail;
+        if (old_tail != NULL) {
+            old_tail->next = this->tail;
+        }
+
+        if (this->head == NULL) {
+            this->head = this->tail;
+        }
+
+        this->num_elements = this->num_elements + 1;
+        return this->size();
+    }
+
+    Type remove_at(unsigned int i) override {
+        if (this->empty() || i >= this->size()) {
+            return NULL;
+        }
+
+        if (i == 0) {
+            return this->remove_first();
+        }
+
+        if (i == this->size() - 1) {
+            return this->remove_last();
+        }
+
+        typename Iterator::Type* e = this->get_wrapper(i);
+        Type ret = (Type)*e;
+
+        e->next->prev = e->prev;
+        e->prev->next = e->next;
+
+        delete e;
+        this->num_elements = this->num_elements - 1;
+
+        return ret;
+    }
+
+    Type remove_first() override {
+        if (this->empty()) {
+            return NULL;
+        }
+
+        Type e = (Type)(*this->head);
+        typename Iterator::Type* old_head = this->head;
+
+        this->head = this->head->next;
+        if (this->head != NULL) {
+            this->head->prev = NULL;
+        } else {
+            this->tail = NULL;
+        }
+
+        delete old_head;
+        this->num_elements = this->num_elements - 1;
+
+        return e;
+    }
+
+    Type remove_last() override {
+        if (this->empty()) {
+            return NULL;
+        }
+
+        Type e = (Type)(*this->tail);
+        typename Iterator::Type* old_tail = this->tail;
+
+        this->tail = this->tail->prev;
+        if (this->tail != NULL) {
+            this->tail->next = NULL;
+        } else {
+            this->head == NULL;
+        }
+
+        delete old_tail;
+        this->num_elements = this->num_elements - 1;
+    }
+
+    bool remove(Type e) override {
+        unsigned int pos = 0;
+        typename Iterator::Type* wrapper = this->head;
+        while (wrapper != NULL) {
+            if ((Type)*wrapper == e) {
+                return remove_at(pos);
+            }
+
+            wrapper = wrapper->next;
+            pos++;
+        }
+    }
+
+    Type get(unsigned int i) const override {
+        if (i >= this->size()) {
+            return NULL;
+        }
+
+        if (i == 0) {
+            return (Type)*head;
+        }
+        if (i == this->size() - 1) {
+            return (Type)*tail;
+        }
+
+        typename Iterator::Type* wrapper = this->head;
+        for (unsigned int pos = 0; pos < i; ++pos) {
+            wrapper = wrapper->next;
+        }
+        return (Type)*wrapper;
+    }
+
+    Type first() const override {
+        if (this->empty()) {
+            return NULL;
+        }
+
+        return (Type)(*this->head);
+    }
+
+    Type last() const override {
+        if (this->empty()) {
+            return NULL;
+        }
+
+        return (Type)(*this->tail);
+    }
+
+    bool empty() const override {
+        return this->size() == 0;
+    }
+    unsigned int size() const override {
+        return this->num_elements;
+    }
+
+    void print(OutStream& out) const override {
+        if (this->empty()) {
+            out << "Print List (0 elements)" << endl;
+            return;
+        }
+
+        out << "Print List (" << dec << this->size() << " elements): ";
+        typename Iterator::Type* current = this->head;
+        while (current != NULL) {
+            out << dec << (Type)(*current) << " ";
+            current = current->next;
+        }
+        out << endl;
+    }
 };
 
 #endif