[libcamera-devel] [PATCH v2 1/8] cam: event_loop: Add support for file descriptor events

[Laurent Pinchart]

Hi Kieran,

On Tue, Aug 03, 2021 at 11:35:34AM +0100, Kieran Bingham wrote:
> Hi Laurent,

Yes ? :-)

> On 30/07/2021 02:02, Laurent Pinchart wrote:
> > Extend the EventLoop class to support watching file descriptors for
> > read and write events.
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> >  src/cam/event_loop.cpp | 44 ++++++++++++++++++++++++++++++++++++++++++
> >  src/cam/event_loop.h   | 20 +++++++++++++++++++
> >  2 files changed, 64 insertions(+)
> > 
> > diff --git a/src/cam/event_loop.cpp b/src/cam/event_loop.cpp
> > index 6a4c47f287d0..e25784c083cf 100644
> > --- a/src/cam/event_loop.cpp
> > +++ b/src/cam/event_loop.cpp
> > @@ -10,6 +10,7 @@
> >  #include <assert.h>
> >  #include <event2/event.h>
> >  #include <event2/thread.h>
> > +#include <iostream>
> >  
> >  EventLoop *EventLoop::instance_ = nullptr;
> >  
> > @@ -26,6 +27,7 @@ EventLoop::~EventLoop()
> >  {
> >  	instance_ = nullptr;
> >  
> > +	events_.clear();
> >  	event_base_free(base_);
> >  	libevent_global_shutdown();
> >  }
> > @@ -58,6 +60,30 @@ void EventLoop::callLater(const std::function<void()> &func)
> >  	event_base_once(base_, -1, EV_TIMEOUT, dispatchCallback, this, nullptr);
> >  }
> >  
> > +void EventLoop::addEvent(int fd, EventType type,
> > +			 const std::function<void()> &callback)
> > +{
> > +	std::unique_ptr<Event> event = std::make_unique<Event>(callback);
> > +	short events = (type & Read ? EV_READ : 0)
> > +		     | (type & Write ? EV_WRITE : 0)
> > +		     | EV_PERSIST;
> > +
> > +	event->event_ = event_new(base_, fd, events, &EventLoop::Event::dispatch,
> > +				  event.get());
> > +	if (!event->event_) {
> > +		std::cerr << "Failed to create event for fd " << fd << std::endl;
> > +		return;
> > +	}
> > +
> > +	int ret = event_add(event->event_, nullptr);
> > +	if (ret < 0) {
> > +		std::cerr << "Failed to add event for fd " << fd << std::endl;
> > +		return;
> > +	}
> > +
> > +	events_.push_back(std::move(event));
> > +}
> > +
> >  void EventLoop::dispatchCallback([[maybe_unused]] evutil_socket_t fd,
> >  				 [[maybe_unused]] short flags, void *param)
> >  {
> > @@ -80,3 +106,21 @@ void EventLoop::dispatchCall()
> >  
> >  	call();
> >  }
> > +
> > +EventLoop::Event::Event(const std::function<void()> &callback)
> > +	: callback_(callback), event_(nullptr)
> > +{
> > +}
> > +
> > +EventLoop::Event::~Event()
> > +{
> > +	event_del(event_);
> > +	event_free(event_);
> > +}
> > +
> > +void EventLoop::Event::dispatch([[maybe_unused]] int fd,
> > +				[[maybe_unused]] short events, void *arg)
> > +{
> > +	Event *event = static_cast<Event *>(arg);
> > +	event->callback_();
> > +}
> > diff --git a/src/cam/event_loop.h b/src/cam/event_loop.h
> > index ba3ba3a4a675..57bb6fb34aa7 100644
> > --- a/src/cam/event_loop.h
> > +++ b/src/cam/event_loop.h
> > @@ -8,6 +8,7 @@
> >  #define __CAM_EVENT_LOOP_H__
> >  
> >  #include <functional>
> > +#include <memory>
> >  #include <list>
> >  #include <mutex>
> >  
> > @@ -18,6 +19,11 @@ struct event_base;
> >  class EventLoop
> >  {
> >  public:
> > +	enum EventType {
> > +		Read = 1,
> > +		Write = 2,
> > +	};
> > +
> >  	EventLoop();
> >  	~EventLoop();
> >  
> > @@ -28,13 +34,27 @@ public:
> >  
> >  	void callLater(const std::function<void()> &func);
> >  
> > +	void addEvent(int fd, EventType type,
> > +		      const std::function<void()> &handler);
> > +
> >  private:
> > +	struct Event {
> > +		Event(const std::function<void()> &callback);
> > +		~Event();
> > +
> > +		static void dispatch(int fd, short events, void *arg);
> > +
> > +		std::function<void()> callback_;
> > +		struct event *event_;
> > +	};
> > +
> >  	static EventLoop *instance_;
> >  
> >  	struct event_base *base_;
> >  	int exitCode_;
> >  
> >  	std::list<std::function<void()>> calls_;
> > +	std::list<std::unique_ptr<Event>> events_;
> >  	std::mutex lock_;
> >  
> >  	static void dispatchCallback(evutil_socket_t fd, short flags,
> > 

-- 
Regards,

Laurent Pinchart