Question

I’m working on a project that reads MIDI-data from an external USB-device. I don’t want to get too specific here, but this is roughly how it looks like:

I’ve got all my incoming MIDI-events stacked inside an object, let’s call it “in”. Now, to get the next MIDI-event from the stack, I first have to check if “in” has at least one event on the stack using a member function.

Is there a way to automatically process all the events on the stack as soon as there are new ones, without having to check everytime?
I’m thinking of something similar to an event-listener (sorry if this sounds stupid, I’m a beginner).

Answer 1

Is there a way to automatically process all the events on the stack as soon as there are new ones, without having to check everytime? I’m thinking of something similar to an event-listener (sorry if this sounds stupid, I’m a beginner).

When your are using stack the code may look like:

// producer
stack.push(midi_event);

// consumer
while(!stack.empty())
    process_event(stack.pop());

Instead of using the stack as a communication queue the producer can keep a pointer to the consumer (callback interface) and push the event directly to consumer like this:

// set-up the producer-consumer callback
Consumer consumer;
Producer producer(&consumer); // saves Consumer* into a member-variable
// start the event processing loop
while(producer_or_an_event_loop_object.wait_and_dispatch())
    ; // loop till wait_and_dispatch() returns false


// Producer::produce_event()
this->consumer->process_event(midi_event); 

Boost.signals library is designed for this kind of problem and has a nice tutorial on the subject.