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


typedef struct node{
	void* data;
	struct node* next;
} NODE;

//Could be only head but it allows a complexity of O(1) instead of O(n) for insertion (where n would be the size of the chain)
typedef struct {
	NODE* head;
	NODE* tail;
} FIFO;

FIFO mkfifo ();
void enqueue(FIFO *lst ,void* el);
void* dequeue(FIFO *lst);

int main(void)
{
	int a = 5;
	int b = 12;
	FIFO fifo = mkfifo();

	enqueue(&fifo, &a);
	enqueue(&fifo, &b);
	int *c = dequeue(&fifo);
	int *d = dequeue(&fifo);

	printf("%d\n", *c);
	printf("%d\n", *d);
	
}

FIFO mkfifo (){
	return (FIFO) {NULL, NULL};
}

void enqueue(FIFO *lst ,void *el){
	NODE *new = calloc(1, sizeof(NODE));
	new->data = el;
	if(lst->tail != NULL)
		lst->tail->next = new;
	lst->tail = new;
	lst->head = lst->head == NULL ? new : lst->head;
}

void* dequeue(FIFO *lst){
	void* ret = lst->head->data;
	lst->head = lst->head->next;
	return ret;
}