muduo网络库源码学习————线程类

muduo库里面的线程类是使用基于对象的编程思想，源码目录为muduo/base，如下所示：
线程类头文件：

// Use of this source code is governed by a BSD-style license// that can be found in the License file.//// Author: Shuo Chen (chenshuo at chenshuo dot com)//线程类#ifndef MUDUO_BASE_THREAD_H#define MUDUO_BASE_THREAD_H#include <muduo/base/Atomic.h>#include <muduo/base/Types.h>#include <boost/function.hpp>#include <boost/noncopyable.hpp>#include <pthread.h>//线程类头文件namespace muduo{class Thread : boost::noncopyable{ public:  typedef boost::function<void ()> ThreadFunc;//函数适配接收的函数//线程构造函数，参数为回调函数和线程名称  explicit Thread(const ThreadFunc&, const string& name = string());//名称默认值为空的字符串类//线程析构函数  ~Thread();  void start();//启动线程  int join(); // return pthread_join()  bool started() const { return started_; }//线程是否已经启动  // pthread_t pthreadId() const { return pthreadId_; }  pid_t tid() const { return tid_; }//线程的真实pid  const string& name() const { return name_; }//线程的名称  static int numCreated() { return numCreated_.get(); }//已经启动的线程个数 private:  static void* startThread(void* thread);//现成的入口函数，调用runInThread函数  void runInThread();//调用回调函数func_  bool       started_;//线程是否已经启动  pthread_t  pthreadId_;//线程的pthread_t  pid_t      tid_;//线程真实的 pid  ThreadFunc func_;//线程的回调函数  string     name_;//线程的名称  static AtomicInt32 numCreated_;//已经创建的线程的个数，每当创建一个线程，该值就加一(原子整数类)};}#endif

线程类的实现文件：

// Use of this source code is governed by a BSD-style license// that can be found in the License file.//// Author: Shuo Chen (chenshuo at chenshuo dot com)//线程类实现文件#include <muduo/base/Thread.h>#include <muduo/base/CurrentThread.h>#include <muduo/base/Exception.h>//#include <muduo/base/Logging.h>//暂时不用日志文件，先注释掉#include <boost/static_assert.hpp>#include <boost/type_traits/is_same.hpp>#include <errno.h>#include <stdio.h>#include <unistd.h>#include <sys/syscall.h>#include <sys/types.h>#include <linux/unistd.h>namespace muduo{namespace CurrentThread{//__thread两个下划线是gcc 内置的线程局部存储设施//每个线程各有一个，并不会去共享他//缓存获取tid是为了提高获取tid的效率  __thread int t_cachedTid = 0;//线程真实pid的缓存，如果每次都用系统调用去获取pid,效率会低  __thread char t_tidString[32];//tid的字符串表示形式  __thread const char* t_threadName = "unknown";//线程的名称  const bool sameType = boost::is_same<int, pid_t>::value;//如果是相同类型，返回true  BOOST_STATIC_ASSERT(sameType);//编译时断言}namespace detail{pid_t gettid()//通过系统调用SYS_gettid获得tid{  return static_cast<pid_t>(::syscall(SYS_gettid));//类型转化为pid_t}void afterFork()//子进程调用的{  muduo::CurrentThread::t_cachedTid = 0;//当前线程pid赋值0  muduo::CurrentThread::t_threadName = "main";//名称赋值name  CurrentThread::tid();//进行缓存  // no need to call pthread_atfork(NULL, NULL, &afterFork);}class ThreadNameInitializer{ public:  ThreadNameInitializer()//构造函数  {    muduo::CurrentThread::t_threadName = "main";//线程名称赋为main，即为主线程名称    CurrentThread::tid();//缓存当前线程的pid    //#include <pthread.h>    //int pthread_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(void));      //调用fork时，内部创建子进程前在父进程中会调用prepare，      //内部创建子进程成功后，父进程会调用parent ，子进程会调用child    pthread_atfork(NULL, NULL, &afterFork);//如果使用fork函数，那么子进程会调用邋afterFork  }};ThreadNameInitializer init;}}using namespace muduo;void CurrentThread::cacheTid(){  if (t_cachedTid == 0)  {    t_cachedTid = detail::gettid();//调用gettid函数获得tid    int n = snprintf(t_tidString, sizeof t_tidString, "%5d ", t_cachedTid);//将tid格式化保存在t_tidString中    assert(n == 6);//断言长度是6，5d后面还有一个空格，所以是6    (void) n;//这一句主要是预防n没有使用从而产生警告  }}bool CurrentThread::isMainThread(){  return tid() == ::getpid();//查看tid是否等于当前进程id}AtomicInt32 Thread::numCreated_;//构造函数，初始化Thread::Thread(const ThreadFunc& func, const string& n) : started_(false), pthreadId_(0),tid_(0),func_(func),name_(n){  numCreated_.increment();//创建的线程的个数加一，为原子性操作}Thread::~Thread(){  // no join}void Thread::start(){  assert(!started_);  started_ = true;  //创建线程，startThread为线程的入口函数  errno = pthread_create(&pthreadId_, NULL, &startThread, this);  if (errno != 0)  {//日志   // LOG_SYSFATAL << "Failed in pthread_create";  }}int Thread::join(){  assert(started_);  return pthread_join(pthreadId_, NULL);}//线程的入口函数void* Thread::startThread(void* obj){//this指针传到obj  Thread* thread = static_cast<Thread*>(obj);//转化为线程基类的指针  thread->runInThread();//调用线程函数runInThread  return NULL;}//被线程的入口函数调用void Thread::runInThread(){  tid_ = CurrentThread::tid();//获取线程的tid  muduo::CurrentThread::t_threadName = name_.c_str();//缓存该线程的名称  try  {    func_();//调用回调函数    muduo::CurrentThread::t_threadName = "finished";  }  catch (const Exception& ex)//异常捕捉  {    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  }}

CurrentThread头文件

// Use of this source code is governed by a BSD-style license// that can be found in the License file.//// Author: Shuo Chen (chenshuo at chenshuo dot com)#ifndef MUDUO_BASE_CURRENTTHREAD_H#define MUDUO_BASE_CURRENTTHREAD_Hnamespace muduo{//CurrentThread的名称空间namespace CurrentThread{  // internal  extern __thread int t_cachedTid;  extern __thread char t_tidString[32];  extern __thread const char* t_threadName;  void cacheTid();  inline int tid()  {    if (t_cachedTid == 0)//还没有缓存过    {//t_cachedTid初值 是0      cacheTid();//进行缓存    }    return t_cachedTid;//返回缓存的tid  }  inline const char* tidString() // for logging  {    return t_tidString;//返回tid的字符串表示形式  }  inline const char* name()  {    return t_threadName;//返回线程名称  }  bool isMainThread();//是否是主线程}}#endif

测试代码位于muduo/base/tests

//线程测试程序#include <muduo/base/Thread.h>#include <muduo/base/CurrentThread.h>#include <string>#include <boost/bind.hpp>#include <stdio.h>void threadFunc(){  printf("tid=%d\n", muduo::CurrentThread::tid());}void threadFunc2(int x){  printf("tid=%d, x=%d\n", muduo::CurrentThread::tid(), x);}class Foo{ public:  explicit Foo(double x) : x_(x)  {  }  void memberFunc()  {    printf("tid=%d, Foo::x_=%f\n", muduo::CurrentThread::tid(), x_);  }  void memberFunc2(const std::string& text)  {    printf("tid=%d, Foo::x_=%f, text=%s\n", muduo::CurrentThread::tid(), x_, text.c_str());  } private:  double x_;};int main(){//获取当前线程的pid(进程id 线程pid)  printf("pid=%d, tid=%d\n", ::getpid(), muduo::CurrentThread::tid());//创建一个线程对象，传递一个函数  muduo::Thread t1(threadFunc);  t1.start();//启动线程  t1.join();//threadFunc2带了一个参数，用boost::bind函数传递进去，最后是线程的名称，可以不传  muduo::Thread t2(boost::bind(threadFunc2, 42), "thread for free function with argument");  t2.start();  t2.join();//创建一个对象  Foo foo(87.53);//创建第三个线程(成员函数的话一定要用&)  muduo::Thread t3(boost::bind(&Foo::memberFunc, &foo), "thread for member function without argument");  t3.start();  t3.join();//创建第四个线程，这里传进去的函数是带参数的  muduo::Thread t4(boost::bind(&Foo::memberFunc2, boost::ref(foo), std::string("Shuo Chen")));  t4.start();  t4.join();//打印最后创建的线程总数  printf("number of created threads %d\n", muduo::Thread::numCreated());}

单独编译后运行结果如下：