[libcamera-devel] [PATCH v8 1/4] cam: event_loop: Add timer events to event loop

[Eric Curtin]

Extend the EventLoop class to support periodic timer events. This can be
used to run tasks periodically, such as handling the event loop of SDL.

Also delete all events in the list, before we event_base_loopbreak.

Signed-off-by: Eric Curtin <ecurtin at redhat.com>
---
 src/cam/event_loop.cpp | 33 +++++++++++++++++++++++++++++++++
 src/cam/event_loop.h   |  6 ++++++
 2 files changed, 39 insertions(+)

diff --git a/src/cam/event_loop.cpp b/src/cam/event_loop.cpp
index e25784c0..181c971c 100644
--- a/src/cam/event_loop.cpp
+++ b/src/cam/event_loop.cpp
@@ -47,6 +47,10 @@ int EventLoop::exec()
 void EventLoop::exit(int code)
 {
 	exitCode_ = code;
+	for (auto const &e : events_) {
+		event_del(e->event_);
+	}
+
 	event_base_loopbreak(base_);
 }
 
@@ -84,6 +88,35 @@ void EventLoop::addEvent(int fd, EventType type,
 	events_.push_back(std::move(event));
 }
 
+void EventLoop::toTimeval(const std::chrono::milliseconds d, struct timeval &tv)
+{
+	tv.tv_sec = std::chrono::duration_cast<std::chrono::seconds>(d).count();
+	tv.tv_usec = std::chrono::duration_cast<std::chrono::microseconds>(d).count();
+}
+
+void EventLoop::addTimerEvent(const std::chrono::milliseconds d,
+			      const std::function<void()> &callback)
+{
+	std::unique_ptr<Event> event = std::make_unique<Event>(callback);
+	event->event_ = event_new(base_, -1, EV_PERSIST, &EventLoop::Event::dispatch,
+				  event.get());
+	if (!event->event_) {
+		std::cerr << "Failed to create timer event" << std::endl;
+		return;
+	}
+
+	struct timeval tv;
+	toTimeval(d, tv);
+
+	int ret = event_add(event->event_, &tv);
+	if (ret < 0) {
+		std::cerr << "Failed to add timer event" << std::endl;
+		return;
+	}
+
+	events_.push_back(std::move(event));
+}
+
 void EventLoop::dispatchCallback([[maybe_unused]] evutil_socket_t fd,
 				 [[maybe_unused]] short flags, void *param)
 {
diff --git a/src/cam/event_loop.h b/src/cam/event_loop.h
index a4613eb2..89215dce 100644
--- a/src/cam/event_loop.h
+++ b/src/cam/event_loop.h
@@ -14,6 +14,8 @@
 
 #include <event2/util.h>
 
+using namespace std::chrono_literals;
+
 struct event_base;
 
 class EventLoop
@@ -37,6 +39,9 @@ public:
 	void addEvent(int fd, EventType type,
 		      const std::function<void()> &handler);
 
+	void addTimerEvent(const std::chrono::milliseconds d,
+			   const std::function<void()> &handler);
+
 private:
 	struct Event {
 		Event(const std::function<void()> &callback);
@@ -57,6 +62,7 @@ private:
 	std::list<std::unique_ptr<Event>> events_;
 	std::mutex lock_;
 
+	void toTimeval(const std::chrono::milliseconds d, struct timeval &tv);
 	static void dispatchCallback(evutil_socket_t fd, short flags,
 				     void *param);
 	void dispatchCall();
-- 
2.35.1