Add DoublyLinkedList data structure

luna/include/luna/LinkedList.h

@@ -0,0 +1,118 @@
+#pragma once
+#include <luna/Result.h>
+
+template <typename T> inline Result<T*> nonnull_or_error(T* ptr)
+{
+    return ptr == nullptr ? err(ENONE) : ptr;
+}
+
+template <typename T> class DoublyLinkedList;
+
+template <typename T> class DoublyLinkedListNode
+{
+
+  private:
+    DoublyLinkedListNode<T>* m_next_node;
+    DoublyLinkedListNode<T>* m_last_node;
+
+    void detach_from_list()
+    {
+        m_next_node->m_last_node = m_last_node;
+        m_last_node->m_next_node = m_next_node;
+    }
+
+    void add_to_list(DoublyLinkedListNode<T>* end_node)
+    {
+        end_node->m_next_node = this;
+        this->m_last_node = end_node;
+    }
+
+    friend class DoublyLinkedList<T>;
+};
+
+template <typename T> class DoublyLinkedList
+{
+  public:
+    void append(T* ptr)
+    {
+        DoublyLinkedListNode<T>* node = (DoublyLinkedListNode<T>*)ptr;
+        if (!m_start_node) m_start_node = node;
+        if (m_end_node) node->add_to_list(m_end_node);
+        m_end_node = node;
+
+        m_count++;
+    }
+
+    T* remove(T* ptr)
+    {
+        DoublyLinkedListNode<T>* node = (DoublyLinkedListNode<T>*)ptr;
+
+        if (node == m_end_node) m_end_node = node->m_last_node;
+        if (node == m_start_node) m_start_node = node->m_next_node;
+
+        node->detach_from_list();
+
+        m_count--;
+
+        return ptr;
+    }
+
+    Result<T*> first()
+    {
+        return nonnull_or_error((T*)m_start_node);
+    }
+
+    Result<T*> last()
+    {
+        return nonnull_or_error((T*)m_end_node);
+    }
+
+    Result<T*> next(T* item)
+    {
+        return nonnull_or_error(((DoublyLinkedListNode<T>*)item)->m_next_node);
+    }
+
+    Result<T*> previous(T* item)
+    {
+        return nonnull_or_error(((DoublyLinkedListNode<T>*)item)->m_last_node);
+    }
+
+    template <typename Callback> void for_each(Callback callback)
+    {
+        for (DoublyLinkedListNode<T>* node = m_start_node; node; node = node->m_next_node) { callback((T*)node); }
+    }
+
+    template <typename Callback> void for_each_reversed(Callback callback)
+    {
+        for (DoublyLinkedListNode<T>* node = m_end_node; node; node = node->m_last_node) { callback((T*)node); }
+    }
+
+    template <typename Callback> void for_each_after(T* start, Callback callback)
+    {
+        for (DoublyLinkedListNode<T>* node = ((DoublyLinkedListNode<T>*)start)->m_next_node; node;
+             node = node->m_next_node)
+        {
+            callback((T*)node);
+        }
+    }
+
+    template <typename Callback> void for_each_before(T* end, Callback callback)
+    {
+        for (DoublyLinkedListNode<T>* node = ((DoublyLinkedListNode<T>*)end)->m_last_node; node;
+             node = node->m_last_node)
+        {
+            callback((T*)node);
+        }
+    }
+
+    usize count()
+    {
+        return m_count;
+    }
+
+  private:
+    DoublyLinkedListNode<T>* m_start_node = nullptr;
+    DoublyLinkedListNode<T>* m_end_node = nullptr;
+
+    usize m_count = 0;
+};