원형큐를 생성하면서 공유메모리를 설정해주는 라이브러리를 만들고 싶은데 질문좀 드릴게요..

#define SHARED_MEMORY_KEY 1234
 
int shmid;
void *shm_addr = (void *)0;
 
void CreateQueue(CircularQueue** queue, int capacity)
{	
	*queue = (CircularQueue*)malloc(sizeof(CircularQueue));
 
	(*queue)->nodes = (Node*)malloc(sizeof(Node)* (capacity + 1));
 
	(*queue)->capacity = capacity;
	(*queue)->front = 0;
	(*queue)->rear = 0;
 
  shmid = shmget((key_t)SHARED_MEMORY_KEY, sizeof(Node), 0666|IPC_CREAT);
 
  if(shmid == -1)
  {
    perror("shmget failed : ");
    exit(0);
  }
}
 
void DestroyQueue(CircularQueue* queue)
{
	free(queue->nodes);
	free(queue);
}
 
void Enqueue(CircularQueue* queue, char data[1400])
{
	int position = 0;
 
	if (queue->rear == queue->capacity + 1)
	{	
		queue->rear = 0;
		position = 0;
	}
	else
	  position = queue->rear++;
 
  shm_addr = shmat(shmid, (void *)0, 0);
  if(shm_addr == (void *)-1)
  {
    perror("shmat failed : ");
    exit(0);
  }
 
  data = (char *)shm_addr;
 
	queue->nodes[position].data = data;
}
 
ElementType Dequeue(CircularQueue* queue)
{
	int position = queue->front;
 
	if (position == queue->capacity)
		queue->front = 0;
	else
		queue->front++;
 
  shm_addr = shmat(shmid, (void *)0, 0);
  if(shm_addr == (void *)-1)
  {
    perror("shmat failed : ");
    exit(0);
  }
 
  queue = (CircularQueue *)shm_addr;
 
	return queue->nodes[position].data;
}
 
 
int GetSize(CircularQueue* queue)
{
 
	if (queue->front <= queue->rear)
		return queue->rear - queue->front;
	else
		return (queue->capacity + 1 - queue->front) + queue->rear;
}
 
int IsEmpty(CircularQueue* queue)
{
	return (queue->front == queue->rear);
}
 
 
int IsFull(CircularQueue* queue)
{
	if (queue->front < queue->rear)
		return (queue->rear - queue->front) == queue->capacity;
	else
		return (queue->rear + 1) == queue->front;
}