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

typedef struct _List List;

struct _List {
	
	List *next;
	void *data;
	
};

typedef struct {

	List *head;
	List *tail;
	
} QUEUE;

static inline QUEUE *
queue_new ()
{
	QUEUE *q;

	q = malloc (sizeof (QUEUE));

	return (QUEUE *) q;
}

static inline void
queue_push (QUEUE *q, void *data) 
{
	List *n;

	n = malloc (sizeof (List));

	n->data = data;
	n->next = NULL;
	
	if (q->tail == NULL) {
		q->head = n;
	} else {
		q->tail->next = n;	
	}
	
	q->tail = n;
}

static inline void *
queue_pop (QUEUE *q)
{
	List *l;
	void *ret;
	
	if (q->head == NULL) {
		return NULL;
	}
	
	l = q->head;
	q->head = q->head->next;
	
	if (q->head == NULL) {
		q->tail = NULL;
	}
	
	ret = l->data;
	free (l);
	return ret;
}

int main (int argc, char **argv)
{
	QUEUE *q;
	char *s;
	
	q = queue_new ();

	queue_push (q, "sir");
	queue_push (q, "gicmo");
	queue_push (q, "miguel");

	while ((s = queue_pop (q)) != NULL) {
		printf ("%s\n", s);
	}
	printf ("-------\n");

	queue_push (q, "apfel");
	queue_push (q, "birne");

	printf ("%s\n", (char *) queue_pop (q));
	
	queue_push (q, "bannae");
	printf ("-------\n");

	while ((s = queue_pop (q)) != NULL) {
		printf ("%s\n", s);
	}

	
	return 0;
}