EventDistributor.cc

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#include "EventDistributor.hh"
#include "EventListener.hh"
#include "Reactor.hh"
#include "RTScheduler.hh"
#include "Interpreter.hh"
#include "InputEventGenerator.hh"
#include "Thread.hh"
#include "ranges.hh"
#include "stl.hh"
#include "view.hh"
#include <cassert>
#include <chrono>
 
using std::string;
 
namespace openmsx {
 
EventDistributor::EventDistributor(Reactor& reactor_)
        : reactor(reactor_)
{
}
 
void EventDistributor::registerEventListener(
                EventType type, EventListener& listener, Priority priority)
{
        std::lock_guard<std::mutex> lock(mutex);
        auto& priorityMap = listeners[type];
        // a listener may only be registered once for each type
        assert(!contains(view::values(priorityMap), &listener));
        // insert at highest position that keeps listeners sorted on priority
        auto it = ranges::upper_bound(priorityMap, priority, LessTupleElement<0>());
        priorityMap.insert(it, {priority, &listener});
}
 
void EventDistributor::unregisterEventListener(
                EventType type, EventListener& listener)
{
        std::lock_guard<std::mutex> lock(mutex);
        auto& priorityMap = listeners[type];
        priorityMap.erase(rfind_if_unguarded(priorityMap,
                [&](auto& v) { return v.second == &listener; }));
}
 
void EventDistributor::distributeEvent(const EventPtr& event)
{
        // TODO: Implement a real solution against modifying data structure while
        //       iterating through it.
        //       For example, assign nullptr first and then iterate again after
        //       delivering events to remove the nullptr values.
        // TODO: Is it useful to test for 0 listeners or should we just always
        //       queue the event?
        assert(event);
        std::unique_lock<std::mutex> lock(mutex);
        if (!listeners[event->getType()].empty()) {
                scheduledEvents.push_back(event);
                // must release lock, otherwise there's a deadlock:
                //   thread 1: Reactor::deleteMotherBoard()
                //             EventDistributor::unregisterEventListener()
                //   thread 2: EventDistributor::distributeEvent()
                //             Reactor::enterMainLoop()
                condition.notify_all();
                lock.unlock();
                reactor.enterMainLoop();
        }
}
 
bool EventDistributor::isRegistered(EventType type, EventListener* listener) const
{
        return contains(view::values(listeners[type]), listener);
}
 
void EventDistributor::deliverEvents()
{
        static PriorityMap priorityMapCopy; // static to preserve capacity
        static EventQueue eventsCopy;       // static to preserve capacity
 
        assert(Thread::isMainThread());
 
        reactor.getInputEventGenerator().poll();
        reactor.getInterpreter().poll();
        reactor.getRTScheduler().execute();
 
        std::unique_lock<std::mutex> lock(mutex);
        // It's possible that executing an event triggers scheduling of another
        // event. We also want to execute those secondary events. That's why
        // we have this while loop here.
        // For example the 'loadstate' command event, triggers a machine switch
        // event and as reaction to the latter event, AfterCommand will
        // unsubscribe from the ols MSXEventDistributor. This really should be
        // done before we exit this method.
        while (!scheduledEvents.empty()) {
                assert(eventsCopy.empty());
                swap(eventsCopy, scheduledEvents);
                for (auto& event : eventsCopy) {
                        auto type = event->getType();
                        priorityMapCopy = listeners[type];
                        lock.unlock();
                        int blockPriority = Priority::LOWEST; // allow all
                        for (const auto& [priority, listener] : priorityMapCopy) {
                                // It's possible delivery to one of the previous
                                // Listeners unregistered the current Listener.
                                if (!isRegistered(type, listener)) continue;
 
                                if (priority >= blockPriority) break;
 
                                if (int block = listener->signalEvent(event)) {
                                        assert(block > priority);
                                        blockPriority = block;
                                }
                        }
                        lock.lock();
                }
                eventsCopy.clear();
        }
}
 
bool EventDistributor::sleep(unsigned us)
{
        std::chrono::microseconds duration(us);
        std::unique_lock<std::mutex> lock(cvMutex);
        return condition.wait_for(lock, duration) == std::cv_status::timeout;
}
 
} // namespace openmsx