muduo源碼-base-Thread

1. Thread.h

Thread類是對線程的封裝，指定了線程狀態，要運行的任務（函數），名字，id等信息。調用start()->創建線程->構建ThreadData對象->傳入任務->運行。

class Thread : noncopyable
{
 public:
  // 指定thread運行函數類型   
  typedef std::function<void ()> ThreadFunc;
  // 構造函數，指定運行函數與名字
  explicit Thread(ThreadFunc, const string& name = string());
  // FIXME: make it movable in C++11
  ~Thread();

  void start();
  int join(); // return pthread_join()

  bool started() const { return started_; }
  // pthread_t pthreadId() const { return pthreadId_; }
  pid_t tid() const { return tid_; }
  const string& name() const { return name_; }

  static int numCreated() { return numCreated_.get(); }

 private:
  void setDefaultName();

  bool       started_;    // 是否已啓動
  bool       joined_;     // 是否已調用join()函數
  pthread_t  pthreadId_;  
  pid_t      tid_;
  ThreadFunc func_;       // 運行函數
  string     name_;       // 名字
  CountDownLatch latch_;  // 倒數計時，倒計時爲0時會通知所有等待現場

  static AtomicInt32 numCreated_;  // 記錄創建的線程數
};

AtomicInt32 Thread::numCreated_;

Thread::Thread(ThreadFunc func, const string& n)
  : started_(false),
    joined_(false),
    pthreadId_(0),
    tid_(0),
    func_(std::move(func)),
    name_(n),
    latch_(1)
{
  setDefaultName();
}

Thread::~Thread()
{
  if (started_ && !joined_)
  {
    pthread_detach(pthreadId_);
  }
}

void Thread::setDefaultName()
{
  int num = numCreated_.incrementAndGet();
  if (name_.empty())
  {
    char buf[32];
    snprintf(buf, sizeof buf, "Thread%d", num);
    name_ = buf;
  }
}

// 運行線程，線程
void Thread::start()
{
  assert(!started_);
  started_ = true;
  // FIXME: move(func_)
  // 創建線程，指定運行函數爲startThread，傳入ThreadData作爲參數
  // 真實運行的任務傳遞到了ThreadData中
  detail::ThreadData* data = new detail::ThreadData(func_, name_, &tid_, &latch_);
  if (pthread_create(&pthreadId_, NULL, &detail::startThread, data))
  {
    started_ = false;
    delete data; // or no delete?
    LOG_SYSFATAL << "Failed in pthread_create";
  }
  else  // pthread_create = 0 創建成功
  {
    // 等待打開門栓  
    latch_.wait();
    assert(tid_ > 0);
  }
}

int Thread::join()
{
  assert(started_);
  assert(!joined_);
  joined_ = true;
  return pthread_join(pthreadId_, NULL);
}

struct ThreadData
{
  typedef muduo::Thread::ThreadFunc ThreadFunc;
  ThreadFunc func_;   // 要運行的任務
  string name_;       // 線程名字
  pid_t* tid_;        // 線程id
  CountDownLatch* latch_;  // 門栓

  ThreadData(ThreadFunc func,
             const string& name,
             pid_t* tid,
             CountDownLatch* latch)
    : func_(std::move(func)),
      name_(name),
      tid_(tid),
      latch_(latch)
  { }

  // 真正線程運行的函數
  void runInThread()
  {
    *tid_ = muduo::CurrentThread::tid();
    tid_ = NULL;
    latch_->countDown();
    latch_ = NULL;

    muduo::CurrentThread::t_threadName = name_.empty() ? "muduoThread" : name_.c_str();
    ::prctl(PR_SET_NAME, muduo::CurrentThread::t_threadName);
    try
    {
      // 調用傳入的任務  
      func_();
      muduo::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
    }
  }
};

// 創建現場傳入的運行函數
void* startThread(void* obj)
{
  // 接收在thread.start()中傳入的參數  
  ThreadData* data = static_cast<ThreadData*>(obj);
  data->runInThread();
  delete data;
  return NULL;
}