如何用C语言表示双向循环链表，请用代码展示

以下是用C语言表示双向循环链表的代码：

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* next;
    struct Node* prev;
};

struct Node* head = NULL;
struct Node* tail = NULL;

void insertAtEnd(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->next = NULL;
    newNode->prev = NULL;

    if (head == NULL) {
        head = newNode;
        tail = newNode;
        head->next = tail;
        tail->prev = head;
    }
    else {
        tail->next = newNode;
        newNode->prev = tail;
        tail = newNode;
        tail->next = head;
        head->prev = tail;
    }
}

void display() {
    struct Node* current = head;

    if (head == NULL) {
        printf("List is empty\n");
        return;
    }

    printf("Nodes of the circular doubly linked list: \n");

    do {
        printf("%d ", current->data);
        current = current->next;
    } while (current != head);
}

int main() {
    insertAtEnd(1);
    insertAtEnd(2);
    insertAtEnd(3);
    insertAtEnd(4);
    insertAtEnd(5);

    display();

    return 0;
}