From b79a04afa753d5cfda47faee9bb4fc7b46c78b01 Mon Sep 17 00:00:00 2001 From: Umang Jain Date: Fri, 4 Dec 2020 13:22:23 +0530 Subject: simple-cam: Provide event-loop backed by libevent libcamera moved its EventDispatcher and Timer API to its internal API, since providing an event loop to applications should not be the job of libcamera. Application utility like cam, were ported to use libevent, hence inspired from that, un-break simple-cam by using the similar implementation to replace the EventDispatcher and Timer functionality by libevent. Signed-off-by: Umang Jain Reviewed-by: Kieran Bingham Signed-off-by: Kieran Bingham --- event_loop.cpp | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ event_loop.h | 45 ++++++++++++++++++++++++++ meson.build | 2 ++ simple-cam.cpp | 35 +++++++++++++-------- 4 files changed, 168 insertions(+), 13 deletions(-) create mode 100644 event_loop.cpp create mode 100644 event_loop.h diff --git a/event_loop.cpp b/event_loop.cpp new file mode 100644 index 0000000..7b6ea65 --- /dev/null +++ b/event_loop.cpp @@ -0,0 +1,99 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Copyright (C) 2020, Google Inc. + * + * event_loop.cpp - Event loop based on cam + */ + +#include "event_loop.h" + +#include +#include +#include + +EventLoop *EventLoop::instance_ = nullptr; + +EventLoop::EventLoop() +{ + assert(!instance_); + + evthread_use_pthreads(); + event_ = event_base_new(); + instance_ = this; +} + +EventLoop::~EventLoop() +{ + instance_ = nullptr; + + event_base_free(event_); + libevent_global_shutdown(); +} + +int EventLoop::exec() +{ + exitCode_ = -1; + exit_.store(false, std::memory_order_release); + + while (!exit_.load(std::memory_order_acquire)) { + dispatchCalls(); + event_base_loop(event_, EVLOOP_NO_EXIT_ON_EMPTY); + } + + return exitCode_; +} + +void EventLoop::exit(int code) +{ + exitCode_ = code; + exit_.store(true, std::memory_order_release); + interrupt(); +} + +void EventLoop::interrupt() +{ + event_base_loopbreak(event_); +} + + +void EventLoop::timeoutTriggered(int fd, short event, void *arg) +{ + EventLoop *self = static_cast(arg); + self->exit(); +} + +void EventLoop::timeout(unsigned int sec) +{ + struct event *ev; + struct timeval tv; + + tv.tv_sec = sec; + tv.tv_usec = 0; + ev = evtimer_new(event_, &timeoutTriggered, this); + evtimer_add(ev, &tv); +} + +void EventLoop::callLater(const std::function &func) +{ + { + std::unique_lock locker(lock_); + calls_.push_back(func); + } + + interrupt(); +} + +void EventLoop::dispatchCalls() +{ + std::unique_lock locker(lock_); + + for (auto iter = calls_.begin(); iter != calls_.end(); ) { + std::function call = std::move(*iter); + + iter = calls_.erase(iter); + + locker.unlock(); + call(); + locker.lock(); + } +} diff --git a/event_loop.h b/event_loop.h new file mode 100644 index 0000000..003c3d8 --- /dev/null +++ b/event_loop.h @@ -0,0 +1,45 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Copyright (C) 2020, Google Inc. + * + * event_loop.h - Event loop based on cam's + */ +#ifndef __SIMPLE_CAM_EVENT_LOOP_H__ +#define __SIMPLE_CAM_EVENT_LOOP_H__ + +#include +#include +#include +#include + +struct event_base; + +class EventLoop +{ +public: + EventLoop(); + ~EventLoop(); + + void exit(int code = 0); + int exec(); + + void timeout(unsigned int sec); + void callLater(const std::function &func); + +private: + static EventLoop *instance_; + + static void timeoutTriggered(int fd, short event, void *arg); + + struct event_base *event_; + std::atomic exit_; + int exitCode_; + + std::list> calls_; + std::mutex lock_; + + void interrupt(); + void dispatchCalls(); +}; + +#endif /* __SIMPLE_CAM_EVENT_LOOP_H__ */ diff --git a/meson.build b/meson.build index c312f2c..4d580c2 100644 --- a/meson.build +++ b/meson.build @@ -8,12 +8,14 @@ project('simple-cam', 'c', 'cpp', # simple-cam.cpp is the fully commented application src_files = files([ 'simple-cam.cpp', + 'event_loop.cpp', ]) # Point your PKG_CONFIG_PATH environment variable to the # libcamera install path camera.pc file ($prefix/lib/pkgconfig/camera.pc) libcamera_deps = [ dependency('camera', required : true), + dependency('libevent_pthreads'), ] cpp_arguments = [ '-Wno-unused-parameter', ] diff --git a/simple-cam.cpp b/simple-cam.cpp index bfe30d7..6d1d84f 100644 --- a/simple-cam.cpp +++ b/simple-cam.cpp @@ -11,8 +11,13 @@ #include +#include "event_loop.h" + +#define TIMEOUT_SEC 3 + using namespace libcamera; std::shared_ptr camera; +EventLoop loop; /* * -------------------------------------------------------------------- @@ -21,13 +26,26 @@ std::shared_ptr camera; * For each Camera::requestCompleted Signal emitted from the Camera the * connected Slot is invoked. * + * The Slot is invoked in the CameraManager's thread, hence one should avoid + * any heavy processing here. The processing of the request shall be re-directed + * to the application's thread instead, so as not to block the CameraManager's + * thread for large amount of time. + * * The Slot receives the Request as a parameter. */ + +static void processRequest(Request *request); + static void requestComplete(Request *request) { if (request->status() == Request::RequestCancelled) return; + loop.callLater(std::bind(&processRequest, request)); +} + +static void processRequest(Request *request) +{ const Request::BufferMap &buffers = request->buffers(); for (auto bufferPair : buffers) { @@ -320,20 +338,11 @@ int main() * * In order to dispatch events received from the video devices, such * as buffer completions, an event loop has to be run. - * - * Libcamera provides its own default event dispatcher realized by - * polling a set of file descriptors, but applications can integrate - * their own even loop with the Libcamera EventDispatcher. - * - * Here, as an example, run the poll-based EventDispatcher for 3 - * seconds. */ - EventDispatcher *dispatcher = cm->eventDispatcher(); - Timer timer; - timer.start(3000); - while (timer.isRunning()) - dispatcher->processEvents(); - + loop.timeout(TIMEOUT_SEC); + int ret = loop.exec(); + std::cout << "Capture ran for " << TIMEOUT_SEC << " seconds and " + << "stopped with exit status: " << ret << std::endl; /* * -------------------------------------------------------------------- * Clean Up -- cgit v1.2.1