muduo库阅读（5）——线程

/* * 线程类 */namespace muduo{class Thread : boost::noncopyable{public:// 线程回调函数typedef boost::function<void ()> ThreadFunc;explicit Thread(const ThreadFunc&, const string& name = string());#ifdef __GXX_EXPERIMENTAL_CXX0X__explicit Thread(ThreadFunc&&, const string& name = string());#endif~Thread();// 启动线程void start();// 等待线程结束int join(); // return pthread_join()// 判断线程是否已经启动bool started() const { return started_; }// pthread_t pthreadId() const { return pthreadId_; }// 获取进程idpid_t tid() const { return *tid_; }// 获取线程的名字const string& name() const { return name_; }// 创建了多少个线程static int numCreated() { return numCreated_.get(); }private:void setDefaultName();bool       started_;// 是否已经开始执行bool       joined_;// 等待结束pthread_t  pthreadId_;// 线程idboost::shared_ptr<pid_t> tid_;// 线程idThreadFunc func_;// 线程函数（执行线程任务的地方）string     name_;// 线程的名字static AtomicInt32 numCreated_;// 已经创建的线程数量，是个静态对象};}

namespace muduo{/* * 当前线程 */namespace CurrentThread{// 线程id__thread int t_cachedTid = 0;// 线程id（字符串）__thread char t_tidString[32];__thread int t_tidStringLength = 6;// 默认的线程名__thread const char* t_threadName = "unknown";// 判断两个类型是否为同一类型const bool sameType = boost::is_same<int, pid_t>::value;BOOST_STATIC_ASSERT(sameType);}namespace detail{// 获取线程idpid_t gettid(){// 直接使用系统调用return static_cast<pid_t>(::syscall(SYS_gettid));}// 当一个进程调用了fork之后，子进程需要调用这个函数void afterFork(){muduo::CurrentThread::t_cachedTid = 0;// 当前线程是主线程muduo::CurrentThread::t_threadName = "main";// 获取线程idCurrentThread::tid();// no need to call pthread_atfork(NULL, NULL, &afterFork);}/* * 线程初始化类，在主线程中使用，在创建任何线程之前使用 */class ThreadNameInitializer{public:ThreadNameInitializer(){muduo::CurrentThread::t_threadName = "main";CurrentThread::tid();pthread_atfork(NULL, NULL, &afterFork);}};// 线程初始化对象ThreadNameInitializer init;/* * 线程数据结构 */struct ThreadData{typedef muduo::Thread::ThreadFunc ThreadFunc;// 回调函数ThreadFunc func_;// 线程名字string name_;// 线程id// weak_ptr不具有普通指针的行为，没有重载operator*和->,它的最大作用在于协助shared_ptr工作，像旁观者那样观测资源的使用情况.boost::weak_ptr<pid_t> wkTid_;ThreadData(const ThreadFunc& func,const string& name,const boost::shared_ptr<pid_t>& tid): func_(func),  name_(name),  wkTid_(tid){ }// 执行线程函数void runInThread(){// 获取线程idpid_t tid = muduo::CurrentThread::tid();boost::shared_ptr<pid_t> ptid = wkTid_.lock();if (ptid){*ptid = tid;ptid.reset();}muduo::CurrentThread::t_threadName = name_.empty() ? "muduoThread" : name_.c_str();// 这个系统调用指令是为进程制定而设计的，明确的选择取决于option// 这里就是设置线程的名字::prctl(PR_SET_NAME, muduo::CurrentThread::t_threadName);try{// 执行func_();// 执行完毕之后，将线程名字设置为finishedmuduo::CurrentThread::t_threadName = "finished";}catch (const Exception& ex){muduo::CurrentThread::t_threadName = "crashed";fprintf(stderr, "exception caught in Thread %s\n", name_.c_str());fprintf(stderr, "reason: %s\n", ex.what());fprintf(stderr, "stack trace: %s\n", ex.stackTrace());abort();}catch (const std::exception& ex){muduo::CurrentThread::t_threadName = "crashed";fprintf(stderr, "exception caught in Thread %s\n", name_.c_str());fprintf(stderr, "reason: %s\n", ex.what());abort();}catch (...){muduo::CurrentThread::t_threadName = "crashed";fprintf(stderr, "unknown exception caught in Thread %s\n", name_.c_str());throw; // rethrow}}};/* * 这个函数其实并没有多线程的作用 * 它是直接调用任务的执行函数，是阻塞的 * 它的主要作用是被线程类的start函数调用 */void* startThread(void* obj){// 获取线程数据ThreadData* data = static_cast<ThreadData*>(obj);// 执行线程函数data->runInThread();delete data;return NULL;}}}using namespace muduo;// 缓存线程idvoid CurrentThread::cacheTid(){if (t_cachedTid == 0){t_cachedTid = detail::gettid();t_tidStringLength = snprintf(t_tidString, sizeof t_tidString, "%5d ", t_cachedTid);}}// 判断是否为主线程bool CurrentThread::isMainThread(){// 主线程的线程id和进程id相同return tid() == ::getpid();}// 睡眠多少纳秒（usec是纳秒数）void CurrentThread::sleepUsec(int64_t usec){// timespec的第一个成员是妙，第二个成员是纳秒struct timespec ts = { 0, 0 };ts.tv_sec = static_cast<time_t>(usec / Timestamp::kMicroSecondsPerSecond);ts.tv_nsec = static_cast<long>(usec % Timestamp::kMicroSecondsPerSecond * 1000);// nanosleep是一个高精度的睡眠函数::nanosleep(&ts, NULL);}// 创建的线程的数量，用于计算一个进程当中线程的数量（由Thread库创建的线程）AtomicInt32 Thread::numCreated_;Thread::Thread(const ThreadFunc& func, const string& n): started_(false),  joined_(false),  pthreadId_(0),  tid_(new pid_t(0)),  func_(func),  name_(n){// 设置默认名字，并且使线程数量加一setDefaultName();}#ifdef __GXX_EXPERIMENTAL_CXX0X__Thread::Thread(ThreadFunc&& func, const string& n): started_(false),  joined_(false),  pthreadId_(0),  tid_(new pid_t(0)),  func_(std::move(func)),  name_(n){setDefaultName();}#endifThread::~Thread(){if (started_ && !joined_){// 线程分离，调用这个函数之后，线程就不受到控制了pthread_detach(pthreadId_);}}/* * 设置线程的默认名字 */void Thread::setDefaultName(){// 线程数量加一int num = numCreated_.incrementAndGet();if (name_.empty()){char buf[32];snprintf(buf, sizeof buf, "Thread%d", num);name_ = buf;}}/* * 启动线程 */void Thread::start(){// 断言线程还没有执行assert(!started_);started_ = true;// FIXME: move(func_)// 创建线程，调用了startThreaddetail::ThreadData* data = new detail::ThreadData(func_, name_, tid_);if (pthread_create(&pthreadId_, NULL, &detail::startThread, data)){started_ = false;delete data; // or no delete?LOG_SYSFATAL << "Failed in pthread_create";}}/* * 等待线程结束 */int Thread::join(){assert(started_);assert(!joined_);joined_ = true;return pthread_join(pthreadId_, NULL);}