General Alternative: Event-Driven Systems

while (TRUE) {

event = GetNextEvent();

switch (event) {

case IncomingPacket:

HandlePacket();

break;

case DiskCompletion:

HandleDiskCompletion();

break;

case TimerExpired:

RunPeriodicTasks();

etc. etc. etc.

}

If handling an event requires waiting for I/O to complete, the thread arranges for another event to notify it of completion, and keeps going, e.g., asynchronous non-blocking I/O.

Structure the code as a single thread that responds to a series of events, each of which carries enough state to determine what is needed and “pick up where we left off”.

Question: in what order should events be delivered?

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