The Event loop discussed in the previous post runs continuously and uses a Time-heap data structure which we discuss today. we maintain the time-outs on a heap, the pending heap. When we want to run them, we put them on the doubly linked list mentioned earlier.  The timeouts are in a heap because it is an efficient way to organize them by order of expiring timeouts. In this implementation I'm looking at, the left and the right children point to similar events with timeouts greater than the parent.  The left differs from the right only in the timeoutcount. if the timeout count is even, it is steered to the right.
whenever new elements are inserted they are bubbled up and down the tree as necessary. After every add or delete, the tree is fixed up.
Timeouts have a link pointer that indicates which list it belongs to. Note that when the timeouts are on the list we reuse the storage for the left and right pointers to be the forward and backward pointers in the doubly linked list
As a test to the Timeout heap, we could make sure that the events are added once and in the correct position on the pending queue and that they are removed from the pending when they are on the expired list to be run and that they are added back to the pending heap and in the correct position for re-triggering. Their position as left or right should remain unchanged if no new nodes were added or deleted.
By doing the test on a controlled heap we know that the events are processed in sequence. In the real world, the events should be guaranteed to be executed if their timeout expired but their sequence could be arbitrary. The heaps are supposed to be short and therefore none of them is expected to be infinite.