Android SurfaceFlinger服务的消息循环过程源码分析
来源:互联网 发布:南方周末 知乎 编辑:程序博客网 时间:2024/06/05 09:45
目录(?)[+]
- SurfaceFlinger消息循环过程
- DisplayHardware对象创建过程
- EventThread线程启动过程
- 事件连接创建过程
- 事件连接Connection注册过程
- 事件连接Socket接收端注册过程
在Android SurfaceFlinger服务启动过程源码分析中详细分析了SurfaceFlinger的整个启动过程,我们知道,在SurfaceFlinger线程执行过程中,循环调用waitForEvent()函数等待消息事件的到来
- bool SurfaceFlinger::threadLoop()
- {
- waitForEvent();
- return true;
- }
bool SurfaceFlinger::threadLoop(){ waitForEvent(); return true;}
而waitForEvent函数则是调用SurfaceFlinger中的消息队列的waitMessage()函数来等待消息事件
- void SurfaceFlinger::waitForEvent() {
- mEventQueue.waitMessage();
- }
void SurfaceFlinger::waitForEvent() { mEventQueue.waitMessage();}通过跟踪代码发现,MessageQueue的waitMessage()函数则是调用Looper对象的pollOnce()函数来等待消息事件的
- void MessageQueue::waitMessage() {
- do {
- IPCThreadState::self()->flushCommands();
- int32_t ret = mLooper->pollOnce(-1);
- switch (ret) {
- case ALOOPER_POLL_WAKE:
- case ALOOPER_POLL_CALLBACK:
- continue;
- case ALOOPER_POLL_ERROR:
- ALOGE("ALOOPER_POLL_ERROR");
- case ALOOPER_POLL_TIMEOUT:
- // timeout (should not happen)
- continue;
- default:
- // should not happen
- ALOGE("Looper::pollOnce() returned unknown status %d", ret);
- continue;
- }
- } while (true);
- }
void MessageQueue::waitMessage() { do { IPCThreadState::self()->flushCommands(); int32_t ret = mLooper->pollOnce(-1); switch (ret) { case ALOOPER_POLL_WAKE: case ALOOPER_POLL_CALLBACK: continue; case ALOOPER_POLL_ERROR: ALOGE("ALOOPER_POLL_ERROR"); case ALOOPER_POLL_TIMEOUT: // timeout (should not happen) continue; default: // should not happen ALOGE("Looper::pollOnce() returned unknown status %d", ret); continue; } } while (true);}该函数无限循环执行,关于Looper的pollOnce()函数在Android应用程序消息循环源码分析有详细的分析过程。本文就针对SurfaceFlinger的消息队列MessageQueue展开讨论,分析SurfaceFlinger的消息队列创建过程。由于在Android SurfaceFlinger服务启动过程源码分析中对SurfaceFlinger的启动过程作了详细的介绍,这里只给出一些关键代码。
- void SurfaceFlinger::onFirstRef()
- {
- //消息队列初始化
- mEventQueue.init(this);
- //启动SurfaceFlinger线程
- run("SurfaceFlinger", PRIORITY_URGENT_DISPLAY);
- mReadyToRunBarrier.wait();
- }
void SurfaceFlinger::onFirstRef(){//消息队列初始化 mEventQueue.init(this);//启动SurfaceFlinger线程 run("SurfaceFlinger", PRIORITY_URGENT_DISPLAY); mReadyToRunBarrier.wait();}
SurfaceFlinger消息循环过程
- void MessageQueue::init(const sp<SurfaceFlinger>& flinger)
- {
- mFlinger = flinger;
- mLooper = new Looper(true);
- mHandler = new Handler(*this);
- }
void MessageQueue::init(const sp<SurfaceFlinger>& flinger){ mFlinger = flinger; mLooper = new Looper(true); mHandler = new Handler(*this);}在初始化消息队列MessageQueue时,为该消息队列创建了一个Looper对象和一个Handler对象。SurfaceFlinger,MessageQueue,Looper,Handler对象之间的关系如下:
在SurfaceFlinger的消息队列MessageQueue的初始化函数中,该该消息队列创建了一个Handler对象,一个Looper对象,Android应用程序消息循环源码分析中分析了Handler,Looper类的相关知识,不过前面介绍的Handler对象是Java层的Handler对象,这里定义的Handler是C++层面的,Looper对象也是C++层的,不过在Android应用程序消息循环源码分析文中对Looper对象有详细的分析,这里就不在重复介绍,重点介绍C++层定义的Handler的实现过程及使用方法。既然SurfaceFlinger的消息队列拥有一个Looper对象,这就说明SurfaceFlinger线程是一个消息循环线程。那么SurfaceFlinger是如何处理消息的呢?
在前面的Android应用程序创建Surface过程源码分析中介绍了应用程序通过调用SurfaceFlinger为应用程序分配的Client对象的Binder远程代理对象的createSurface函数来创建一个Surface:
- sp<ISurface> Client::createSurface(
- ISurfaceComposerClient::surface_data_t* params,
- const String8& name,
- DisplayID display, uint32_t w, uint32_t h, PixelFormat format,
- uint32_t flags)
- {
- sp<MessageBase> msg = new MessageCreateSurface(mFlinger.get(),params, name, this, display, w, h, format, flags);
- mFlinger->postMessageSync(msg);
- return static_cast<MessageCreateSurface*>( msg.get() )->getResult();
- }
sp<ISurface> Client::createSurface( ISurfaceComposerClient::surface_data_t* params, const String8& name, DisplayID display, uint32_t w, uint32_t h, PixelFormat format, uint32_t flags){ sp<MessageBase> msg = new MessageCreateSurface(mFlinger.get(),params, name, this, display, w, h, format, flags); mFlinger->postMessageSync(msg); return static_cast<MessageCreateSurface*>( msg.get() )->getResult();}函数首先将请求创建的Surface参数封装为MessageCreateSurface对象,然后调用SurfaceFlinger的postMessageSync函数往SurfaceFlinger的消息队列中发送一个同步消息,当消息处理完后,通过调用消息msg的getResult()函数来得到创建的Surface。
- status_t SurfaceFlinger::postMessageSync(const sp<MessageBase>& msg,
- nsecs_t reltime, uint32_t flags) {
- //往消息队列中发送一个消息
- status_t res = mEventQueue.postMessage(msg, reltime);
- //消息发送成功后,当前线程等待消息处理
- if (res == NO_ERROR) {
- msg->wait();
- }
- return res;
- }
status_t SurfaceFlinger::postMessageSync(const sp<MessageBase>& msg, nsecs_t reltime, uint32_t flags) {//往消息队列中发送一个消息 status_t res = mEventQueue.postMessage(msg, reltime);//消息发送成功后,当前线程等待消息处理 if (res == NO_ERROR) { msg->wait(); } return res;}其实这里发送的并不是消息对象,而是一个Handler对象,MessageCreateSurface的继承关系如下所示:
- status_t MessageQueue::postMessage(const sp<MessageBase>& messageHandler, nsecs_t relTime)
- {
- const Message dummyMessage;
- //将messageHandler对象和dummyMessage消息对象发送到消息循环Looper对象中
- if (relTime > 0) {
- mLooper->sendMessageDelayed(relTime, messageHandler, dummyMessage);
- } else {
- mLooper->sendMessage(messageHandler, dummyMessage);
- }
- return NO_ERROR;
- }
status_t MessageQueue::postMessage(const sp<MessageBase>& messageHandler, nsecs_t relTime){ const Message dummyMessage;//将messageHandler对象和dummyMessage消息对象发送到消息循环Looper对象中 if (relTime > 0) { mLooper->sendMessageDelayed(relTime, messageHandler, dummyMessage); } else { mLooper->sendMessage(messageHandler, dummyMessage); } return NO_ERROR;}关于消息循环Looper对象的消息发送函数sendMessage的调用流程在Android应用程序消息循环源码分析已经有详细的分析。这里再次贴上关于消息插入代码:
- void Looper::sendMessageAtTime(nsecs_t uptime, const sp<MessageHandler>& handler,
- const Message& message) {
- size_t i = 0;
- { // acquire lock
- AutoMutex _l(mLock);
- //获取消息队列中保存的消息个数
- size_t messageCount = mMessageEnvelopes.size();
- //按时间排序,查找当前消息应该插入的位置
- while (i < messageCount && uptime >= mMessageEnvelopes.itemAt(i).uptime) {
- i += 1;
- }
- //将Message消息及消息处理Handler封装为MessageEnvelope对象,并插入到消息队列mMessageEnvelopes中
- MessageEnvelope messageEnvelope(uptime, handler, message);
- mMessageEnvelopes.insertAt(messageEnvelope, i, 1);
- if (mSendingMessage) {
- return;
- }
- } // release lock
- //唤醒消息循环线程以及时处理消息
- if (i == 0) {
- wake();
- }
- }
void Looper::sendMessageAtTime(nsecs_t uptime, const sp<MessageHandler>& handler, const Message& message) { size_t i = 0; { // acquire lock AutoMutex _l(mLock);//获取消息队列中保存的消息个数 size_t messageCount = mMessageEnvelopes.size();//按时间排序,查找当前消息应该插入的位置 while (i < messageCount && uptime >= mMessageEnvelopes.itemAt(i).uptime) { i += 1; }//将Message消息及消息处理Handler封装为MessageEnvelope对象,并插入到消息队列mMessageEnvelopes中 MessageEnvelope messageEnvelope(uptime, handler, message); mMessageEnvelopes.insertAt(messageEnvelope, i, 1); if (mSendingMessage) { return; } } // release lock //唤醒消息循环线程以及时处理消息 if (i == 0) { wake(); }}到此消息发送就完成了,由于发送的是一个同步消息,因此消息发送线程此刻进入睡眠等待状态,而消息循环线程被唤醒起来处理消息,消息处理过程如下:
- //所有C++层的消息都封装为MessageEnvelope类型的变量并保存到mMessageEnvelopes链表中
- while (mMessageEnvelopes.size() != 0) {
- nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
- const MessageEnvelope& messageEnvelope = mMessageEnvelopes.itemAt(0);
- //处理当前时刻之前的所有消息
- if (messageEnvelope.uptime <= now) {
- {
- //取出处理该消息的Hanlder
- sp<MessageHandler> handler = messageEnvelope.handler;
- //取出该消息描述符
- Message message = messageEnvelope.message;
- //从mMessageEnvelopes链表中移除该消息
- mMessageEnvelopes.removeAt(0);
- //表示当前消息循环线程正在处理消息,处于唤醒状态,因此消息发送线程无需唤醒消息循环线程
- mSendingMessage = true;
- mLock.unlock();
- //调用该消息Handler对象的handleMessage函数来处理该消息
- handler->handleMessage(message);
- } // release handler
- mLock.lock();
- mSendingMessage = false;
- result = ALOOPER_POLL_CALLBACK;
- } else {
- // The last message left at the head of the queue determines the next wakeup time.
- mNextMessageUptime = messageEnvelope.uptime;
- break;
- }
- }
//所有C++层的消息都封装为MessageEnvelope类型的变量并保存到mMessageEnvelopes链表中while (mMessageEnvelopes.size() != 0) {nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);const MessageEnvelope& messageEnvelope = mMessageEnvelopes.itemAt(0);//处理当前时刻之前的所有消息if (messageEnvelope.uptime <= now) {{ //取出处理该消息的Hanldersp<MessageHandler> handler = messageEnvelope.handler;//取出该消息描述符Message message = messageEnvelope.message;//从mMessageEnvelopes链表中移除该消息mMessageEnvelopes.removeAt(0);//表示当前消息循环线程正在处理消息,处于唤醒状态,因此消息发送线程无需唤醒消息循环线程mSendingMessage = true;mLock.unlock();//调用该消息Handler对象的handleMessage函数来处理该消息handler->handleMessage(message);} // release handlermLock.lock();mSendingMessage = false;result = ALOOPER_POLL_CALLBACK;} else {// The last message left at the head of the queue determines the next wakeup time.mNextMessageUptime = messageEnvelope.uptime;break;}}消息处理过程就是调用该消息的Handler对象的handleMessage函数来完成,由于创建Surface时,往消息队列中发送的Handler对象类型为MessageCreateSurface,因此必定会调用该类的handleMessage函数来处理Surface创建消息。但该类并未实现
handleMessage函数,同时该类继承于MessageBase,由此可见其父类MessageBase必定实现了handleMessage函数:
- void MessageBase::handleMessage(const Message&) {
- this->handler();
- barrier.open();
- };
void MessageBase::handleMessage(const Message&) { this->handler(); barrier.open();};该函数首先调用其子类的handler()函数处理消息,然后唤醒消息发送线程,表明发往消息队列中的消息已得到处理,消息发送线程可以往下执行了。由于MessageCreateSurface是MessageBase的子类,因此该类必定实现了handler()函数来处理Surface创建消息:
- class MessageCreateSurface : public MessageBase {
- sp<ISurface> result;
- SurfaceFlinger* flinger;
- ISurfaceComposerClient::surface_data_t* params;
- Client* client;
- const String8& name;
- DisplayID display;
- uint32_t w, h;
- PixelFormat format;
- uint32_t flags;
- public:
- MessageCreateSurface(SurfaceFlinger* flinger,
- ISurfaceComposerClient::surface_data_t* params,
- const String8& name, Client* client,
- DisplayID display, uint32_t w, uint32_t h, PixelFormat format,
- uint32_t flags)
- : flinger(flinger), params(params), client(client), name(name),
- display(display), w(w), h(h), format(format), flags(flags)
- {
- }
- sp<ISurface> getResult() const { return result; }
- virtual bool handler() {
- result = flinger->createSurface(params, name, client,display, w, h, format, flags);
- return true;
- }
- };
class MessageCreateSurface : public MessageBase {sp<ISurface> result;SurfaceFlinger* flinger;ISurfaceComposerClient::surface_data_t* params;Client* client;const String8& name;DisplayID display;uint32_t w, h;PixelFormat format;uint32_t flags;public:MessageCreateSurface(SurfaceFlinger* flinger,ISurfaceComposerClient::surface_data_t* params,const String8& name, Client* client,DisplayID display, uint32_t w, uint32_t h, PixelFormat format,uint32_t flags): flinger(flinger), params(params), client(client), name(name), display(display), w(w), h(h), format(format), flags(flags){}sp<ISurface> getResult() const { return result; }virtual bool handler() {result = flinger->createSurface(params, name, client,display, w, h, format, flags);return true;}};这里又调用SurfaceFlinger的createSurface函数来创建Surface,Surface的创建调用过程如下:
DisplayHardware对象创建过程
SurfaceFlinger线程启动后,首先会调用readyToRun()函数来完成一些线程运行前的准备工作
- status_t SurfaceFlinger::readyToRun()
- {
- // initialize the main display
- GraphicPlane& plane(graphicPlane(dpy));
- //创建DisplayHardware对象
- DisplayHardware* const hw = new DisplayHardware(this, dpy);
- plane.setDisplayHardware(hw);
- ...
- //创建EventThread线程对象
- mEventThread = new EventThread(this);
- mEventQueue.setEventThread(mEventThread);
- hw.startSleepManagement();
- mReadyToRunBarrier.open();
- return NO_ERROR;
- }
status_t SurfaceFlinger::readyToRun(){// initialize the main displayGraphicPlane& plane(graphicPlane(dpy));//创建DisplayHardware对象DisplayHardware* const hw = new DisplayHardware(this, dpy);plane.setDisplayHardware(hw);... //创建EventThread线程对象 mEventThread = new EventThread(this); mEventQueue.setEventThread(mEventThread); hw.startSleepManagement(); mReadyToRunBarrier.open(); return NO_ERROR;}在该函数中创建了两个对象:DisplayHardware对象和EventThread对象,同时将EventThread对象设置到消息队列MessageQueue中。MessageQueue消息队列在前面已经介绍了,它是在SurfaceFlinger线程启动前被创建的。
- DisplayHardware::DisplayHardware(
- const sp<SurfaceFlinger>& flinger,
- uint32_t dpy)
- : DisplayHardwareBase(flinger, dpy),
- mFlinger(flinger), mFlags(0), mHwc(0)
- {
- init(dpy);
- }
DisplayHardware::DisplayHardware( const sp<SurfaceFlinger>& flinger, uint32_t dpy) : DisplayHardwareBase(flinger, dpy), mFlinger(flinger), mFlags(0), mHwc(0){ init(dpy);}构造DisplayHardware对象前首先会调用其父类DisplayHardwareBase的构造函数
- DisplayHardwareBase::DisplayHardwareBase(const sp<SurfaceFlinger>& flinger,
- uint32_t displayIndex)
- {
- mScreenAcquired = true;
- mDisplayEventThread = new DisplayEventThread(flinger);
- }
DisplayHardwareBase::DisplayHardwareBase(const sp<SurfaceFlinger>& flinger, uint32_t displayIndex) { mScreenAcquired = true; mDisplayEventThread = new DisplayEventThread(flinger);}这里创建了一个DisplayEventThread线程对象,关于DisplayEventThread线程的执行过程,在后面分析。在DisplayHardware构造函数中,调用的它的init函数来初始化DisplayHardware对象
- void DisplayHardware::init(uint32_t dpy)
- {
- mNativeWindow = new FramebufferNativeWindow();
- framebuffer_device_t const * fbDev = mNativeWindow->getDevice();
- if (!fbDev) {
- ALOGE("Display subsystem failed to initialize. check logs. exiting...");
- exit(0);
- }
- ...
- // initialize the H/W composer
- mHwc = new HWComposer(mFlinger, *this, mRefreshPeriod);
- if (mHwc->initCheck() == NO_ERROR) {
- mHwc->setFrameBuffer(mDisplay, mSurface);
- }
- }
void DisplayHardware::init(uint32_t dpy){ mNativeWindow = new FramebufferNativeWindow(); framebuffer_device_t const * fbDev = mNativeWindow->getDevice(); if (!fbDev) { ALOGE("Display subsystem failed to initialize. check logs. exiting..."); exit(0); }... // initialize the H/W composer mHwc = new HWComposer(mFlinger, *this, mRefreshPeriod); if (mHwc->initCheck() == NO_ERROR) { mHwc->setFrameBuffer(mDisplay, mSurface); }}在这里仍然创建了两个对象,分别是FramebufferNativeWindow对象和HWComposer对象,同时将DisplayHardware对象保存到HWComposer的成员变量mEventHandler,接下来分析一下HWComposer对象的创建过程:
- HWComposer::HWComposer(
- const sp<SurfaceFlinger>& flinger,
- EventHandler& handler,
- nsecs_t refreshPeriod)
- : mFlinger(flinger),
- mModule(0), mHwc(0), mList(0), mCapacity(0),
- mNumOVLayers(0), mNumFBLayers(0),
- mDpy(EGL_NO_DISPLAY), mSur(EGL_NO_SURFACE),
- mEventHandler(handler),
- mRefreshPeriod(refreshPeriod),
- mVSyncCount(0), mDebugForceFakeVSync(false)
- {
- char value[PROPERTY_VALUE_MAX];
- property_get("debug.sf.no_hw_vsync", value, "0");
- //....
- if (needVSyncThread) {
- // we don't have VSYNC support, we need to fake it
- mVSyncThread = new VSyncThread(*this);
- }
- }
HWComposer::HWComposer( const sp<SurfaceFlinger>& flinger, EventHandler& handler, nsecs_t refreshPeriod) : mFlinger(flinger), mModule(0), mHwc(0), mList(0), mCapacity(0), mNumOVLayers(0), mNumFBLayers(0), mDpy(EGL_NO_DISPLAY), mSur(EGL_NO_SURFACE), mEventHandler(handler), mRefreshPeriod(refreshPeriod), mVSyncCount(0), mDebugForceFakeVSync(false){ char value[PROPERTY_VALUE_MAX]; property_get("debug.sf.no_hw_vsync", value, "0");//.... if (needVSyncThread) { // we don't have VSYNC support, we need to fake it mVSyncThread = new VSyncThread(*this); }}这里首先加载HWComposer硬件抽象模块,HWComposer硬件模块用于产生VSync信号,如果加载失败,说明需要使用软件来模拟产生VSync信号。当变量needVSyncThread为true时,就创建一个VSyncThread线程来模拟产生VSync信号。到处总结一下DisplayHardware对象构造过程中所创建的对象:
EventThread线程启动过程
- EventThread::EventThread(const sp<SurfaceFlinger>& flinger)
- : mFlinger(flinger),
- mHw(flinger->graphicPlane(0).editDisplayHardware()),
- mLastVSyncTimestamp(0),
- mVSyncTimestamp(0),
- mUseSoftwareVSync(false),
- mDeliveredEvents(0),
- mDebugVsyncEnabled(false)
- {
- }
EventThread::EventThread(const sp<SurfaceFlinger>& flinger) : mFlinger(flinger), mHw(flinger->graphicPlane(0).editDisplayHardware()), mLastVSyncTimestamp(0), mVSyncTimestamp(0), mUseSoftwareVSync(false), mDeliveredEvents(0), mDebugVsyncEnabled(false){}由于EventThread继承RefBase类,因此在第一次强引用该对象时,会自动调用其onFirstRef()函数
- void EventThread::onFirstRef() {
- mHw.setVSyncHandler(this);
- run("EventThread", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);
- }
void EventThread::onFirstRef() { mHw.setVSyncHandler(this); run("EventThread", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);}变量mHw在构造EventThread对象时被赋值为flinger->graphicPlane(0).editDisplayHardware(),在上一小节中创建的DisplayHardware对象通过plane.setDisplayHardware(hw)被保存到GraphicPlane的成员变量mHw中,函数graphicPlane(0)用于获取第0个显示屏GraphicPlane对象,然后调用GraphicPlane的editDisplayHardware()函数返回其成员变量mHw保存的对象指针,因此EventThread的成员变量mHw也保存了上一小节创建的DisplayHardware对象指针。mHw.setVSyncHandler(this)语句是将当前EventThread对象保存到DisplayHardware的成员变量mVSyncHandler中:
- void DisplayHardware::setVSyncHandler(const sp<VSyncHandler>& handler) {
- Mutex::Autolock _l(mLock);
- mVSyncHandler = handler;
- }
void DisplayHardware::setVSyncHandler(const sp<VSyncHandler>& handler) { Mutex::Autolock _l(mLock); mVSyncHandler = handler;}
事件连接创建过程
- mEventQueue.setEventThread(mEventThread);
mEventQueue.setEventThread(mEventThread);setEventThread()函数的执行过程如下:
- void MessageQueue::setEventThread(const sp<EventThread>& eventThread)
- {
- mEventThread = eventThread;
- mEvents = eventThread->createEventConnection();
- mEventTube = mEvents->getDataChannel();
- //将socket接收端添加到looper中监听,并且设置了事件处理回调函数cb_eventReceiver
- mLooper->addFd(mEventTube->getFd(), 0, ALOOPER_EVENT_INPUT,MessageQueue::cb_eventReceiver, this);
- }
void MessageQueue::setEventThread(const sp<EventThread>& eventThread){ mEventThread = eventThread; mEvents = eventThread->createEventConnection(); mEventTube = mEvents->getDataChannel();//将socket接收端添加到looper中监听,并且设置了事件处理回调函数cb_eventReceiver mLooper->addFd(mEventTube->getFd(), 0, ALOOPER_EVENT_INPUT,MessageQueue::cb_eventReceiver, this);}函数首先将创建的EventThread对象保存到消息队列MessageQueue的成员变量mEventThread中,然后调用EventThread对象的createEventConnection()函数创建一个事件连接Connection,Connection类是基于Binder进程间通信框架设计的,因此该对象可以实现跨进程传输,函数调用,其在Binder框架下的类关系图如下:
- sp<EventThread::Connection> EventThread::createEventConnection() const {
- return new Connection(const_cast<EventThread*>(this));
- }
sp<EventThread::Connection> EventThread::createEventConnection() const { return new Connection(const_cast<EventThread*>(this));}参数this指向已创建的EventThread对象
- EventThread::Connection::Connection(
- const sp<EventThread>& eventThread)
- : count(-1), mEventThread(eventThread), mChannel(new BitTube())
- {
- }
EventThread::Connection::Connection( const sp<EventThread>& eventThread) : count(-1), mEventThread(eventThread), mChannel(new BitTube()){}Connection构造过程中,将EventThread对象保存到Connection的成员变量mEventThread中,同时创建一个BitTube对象,并保存到Connection的成员变量mChannel中。BitTube对象的构造过程如下:
- BitTube::BitTube(): mSendFd(-1), mReceiveFd(-1)
- {
- int sockets[2];
- //创建一对socket
- if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets) == 0) {
- int size = SOCKET_BUFFER_SIZE;
- setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &size, sizeof(size));
- setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));
- setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &size, sizeof(size));
- setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));
- fcntl(sockets[0], F_SETFL, O_NONBLOCK);
- fcntl(sockets[1], F_SETFL, O_NONBLOCK);
- mReceiveFd = sockets[0];
- mSendFd = sockets[1];
- } else {
- mReceiveFd = -errno;
- ALOGE("BitTube: pipe creation failed (%s)", strerror(-mReceiveFd));
- }
- }
BitTube::BitTube(): mSendFd(-1), mReceiveFd(-1){ int sockets[2];//创建一对socket if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets) == 0) { int size = SOCKET_BUFFER_SIZE; setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &size, sizeof(size)); setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &size, sizeof(size)); setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &size, sizeof(size)); setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &size, sizeof(size)); fcntl(sockets[0], F_SETFL, O_NONBLOCK); fcntl(sockets[1], F_SETFL, O_NONBLOCK); mReceiveFd = sockets[0]; mSendFd = sockets[1]; } else { mReceiveFd = -errno; ALOGE("BitTube: pipe creation failed (%s)", strerror(-mReceiveFd)); }}socketpair函数创建了彼此相连的两个套接字。
事件连接Connection注册过程
- void EventThread::Connection::onFirstRef() {
- // NOTE: mEventThread doesn't hold a strong reference on us
- mEventThread->registerDisplayEventConnection(this);
- }
void EventThread::Connection::onFirstRef() { // NOTE: mEventThread doesn't hold a strong reference on us mEventThread->registerDisplayEventConnection(this);}该函数调用EventThread的registerDisplayEventConnection()函数将当前创建的Connection对象注册到EventThread线程对象中,以便EventThread线程可以将VSync信号事件分发给所有注册的Connection连接的另一端。
- status_t EventThread::registerDisplayEventConnection(
- const sp<EventThread::Connection>& connection) {
- Mutex::Autolock _l(mLock);
- //将创建的Connection对象添加到EventThread的成员变量mDisplayEventConnections向量中
- mDisplayEventConnections.add(connection);
- //如果EventThread线程正处于睡眠等待,则唤醒EventThread线程
- mCondition.broadcast();
- return NO_ERROR;
- }
status_t EventThread::registerDisplayEventConnection( const sp<EventThread::Connection>& connection) { Mutex::Autolock _l(mLock);//将创建的Connection对象添加到EventThread的成员变量mDisplayEventConnections向量中 mDisplayEventConnections.add(connection);//如果EventThread线程正处于睡眠等待,则唤醒EventThread线程 mCondition.broadcast(); return NO_ERROR;}到此EventThread线程就可以向已注册的Connection发送事件消息了,通过向Connection中的Socket发送端描述符写入数据,在Socket的接收端描述符中就可以接收到EventThread写入的数据。
事件连接Socket接收端注册过程
- mEventTube = mEvents->getDataChannel();
- //将socket接收端添加到SurfaceFlinger的消息队列中监控
- mLooper->addFd(mEventTube->getFd(), 0, ALOOPER_EVENT_INPUT,MessageQueue::cb_eventReceiver, this);
mEventTube = mEvents->getDataChannel();//将socket接收端添加到SurfaceFlinger的消息队列中监控mLooper->addFd(mEventTube->getFd(), 0, ALOOPER_EVENT_INPUT,MessageQueue::cb_eventReceiver, this);变量mEventTube指向创建的事件连接Connection对象中的BitTube对象
- sp<BitTube> EventThread::Connection::getDataChannel() const {
- return mChannel;//mChannel(new BitTube())
- }
sp<BitTube> EventThread::Connection::getDataChannel() const { return mChannel;//mChannel(new BitTube())}函数getFd()用于返回创建的Sockets对的接收端描述符
- int BitTube::getFd() const
- {
- return mReceiveFd;
- }
int BitTube::getFd() const{ return mReceiveFd;}mLooper->addFd(mEventTube->getFd(), 0, ALOOPER_EVENT_INPUT,MessageQueue::cb_eventReceiver, this)就是将Socket接收端文件描述符添加到消息循环Looper对象中,并且监听该文件描述符下的ALOOPER_EVENT_INPUT事件,当该Socket接收端接收到消息事件后,调用回调函数MessageQueue::cb_eventReceiver来处理该事件。关于向消息循环中添加监控句柄过程在Android应用程序消息循环源码分析中已经详细分析了,将Connection中的Socket接收端文件描述符注册到SurfaceFlinger的消息循环Looper中后,SurfaceFlinger的消息队列MessageQueue就可以接收到EventThread线程分发的事件消息了。
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