feat: extend kmain with listInit and listEmpty

src/list.c

@@ -0,0 +1,61 @@
+#include "list.h"
+
+void listInit(ListNode* head)
+{
+    head->next = head;
+    head->prev = head;
+}
+
+bool listEmpty(const ListNode* head)
+{
+    return head->next == head;
+}
+
+void listInsertAfter(ListNode* pos, ListNode* newNode)
+{
+    newNode->prev = pos;
+    newNode->next = pos->next;
+    pos->next->prev = newNode;
+    pos->next = newNode;
+}
+
+void listInsertBefore(ListNode* pos, ListNode* newNode)
+{
+    listInsertAfter(pos->prev, newNode);
+}
+
+void listPushBack(ListNode* head, ListNode* newNode)
+{
+    listInsertBefore(head, newNode);
+}
+
+void listPushFront(ListNode* head, ListNode* newNode)
+{
+    listInsertAfter(head, newNode);
+}
+
+void listRemove(ListNode* node)
+{
+    node->prev->next = node->next;
+    node->next->prev = node->prev;
+    node->next = node;
+    node->prev = node;
+}
+
+usize listLen(const ListNode* head)
+{
+    usize count = 0;
+    for (const ListNode* cursor = head->next; cursor != head; cursor = cursor->next)
+        count++;
+    return count;
+}
+
+ListNode* listFront(const ListNode* head)
+{
+    return listEmpty(head) ? nullptr : head->next;
+}
+
+ListNode* listBack(const ListNode* head)
+{
+    return listEmpty(head) ? nullptr : head->prev;
+}