[C] A function to swap two adjacent nodes in a doubly-linked list.

swap.c

void	ls_swap(t_list **a)
{
	t_list *tmp;

	tmp = (*a);
	(*a) = (*a)->next;
	tmp->next = (*a)->next;
	if (tmp->next)
		tmp->next->prev = tmp;
	(*a)->prev = tmp->prev;
	tmp->prev = (*a);
	(*a)->next = tmp;
	if ((*a)->prev)
		(*a)->prev->next = (*a);
}