Muduo学习笔记(一) 什么都不做的EventLoop

EventLoop

EventLoop的基本接口包括构造、析构、loop()。

One Loop Per Thread 一个线程只有一个EventLoop对象、如果当前线程创建了其他 EventLoop对象,则终止程序.

CurrentThread

CurrentThread 通过__thread 关键字和系统调用syscall() 保存获取线程的的pid(不通于线程tid，tid属于进程,进程内唯一,线程pid属于内核).

#ifndef _CURRENT_THREAD

#define _CURRENT_THREAD

#include <stdint.h>

#include <stdio.h>

#include <sys/syscall.h>

#include <pthread.h>

#include <unistd.h>

namespace CurrentThread

{

  // internal

  extern __thread int t_cachedTid;

  extern __thread char t_tidString[32];

  extern __thread int t_tidStringLength;

  extern __thread const char* t_threadName;

  inline int tid()

  {

    if (__builtin_expect(t_cachedTid == 0, 0))

    {

      if (t_cachedTid == 0)

      {

        t_cachedTid = static_cast<pid_t>(::syscall(SYS_gettid));

        t_tidStringLength = snprintf(t_tidString, sizeof t_tidString, "%5d ", t_cachedTid);

      }

    }

    return t_cachedTid;

  }

  inline const char* tidString() // for logging

  {

    return t_tidString;

  }

  inline int tidStringLength() // for logging

  {

    return t_tidStringLength;

  }

  inline const char* name()

  {

    return t_threadName;

  }

}

#endif

//CurrentThread.cpp

#include "CurrentThread.hh"

namespace CurrentThread

{

  __thread int t_cachedTid = 0;

  __thread char t_tidString[32];

  __thread int t_tidStringLength = 6;

  __thread const char* t_threadName = "unknown";

}

getEventLoopOfCurrentThread

每个线程至多有一个EventLoop对象,那么我们通过static 成员函数getEventLoopOfCurrentThread() 返回此对象.

EventLoop* EventLoop::getEventLoopOfCurrentThread()

{

  return t_loopInThisThread;

}

EventLoop 源代码

#ifndef NET_EVENTLOOP_H

#define NET_EVENTLOOP_H

#include "CurrentThread.hh"

class EventLoop

{

public:

	EventLoop();

	~EventLoop();

	void loop();

	void assertInLoopThread()

	{

		if(!isInloopThread())

		{

			abortNotInLoopThread();

		}

	}

	bool isInloopThread() const {return m_threadId == CurrentThread::tid(); }

	static EventLoop* getEventLoopOfCurrentThread();

private:

	EventLoop& operator=(const EventLoop&);

	EventLoop(const EventLoop&);

	void abortNotInLoopThread();

	bool m_looping;

	const pid_t m_threadId;

};

#endif

// EventLoop.cpp

#include "EventLoop.hh"

#include "Logger.hh"

#include <assert.h>

#include <poll.h>

__thread EventLoop* t_loopInThisThread = 0;

EventLoop::EventLoop()

	:m_looping(false),

  m_threadId(CurrentThread::tid())

{

  LOG_TRACE << "EventLoop Create " << this << " in thread " << m_threadId;

  if(t_loopInThisThread)

  {  //每个线程只有一个EventLoop对象 , 如果当前线程创建了其他 EventLoop对象,则终止程序.

    LOG_FATAL << "Anthor EventLoop " << t_loopInThisThread

              << " exists in this thread " << m_threadId;

  }

  else

  {

    t_loopInThisThread = this;

  }

}

EventLoop::~EventLoop()

{

  assert(!m_looping);

  t_loopInThisThread = NULL;

}

void EventLoop::loop()

{

  assert(!m_looping);

  assertInLoopThread();

  m_looping = true;

  LOG_TRACE << "EventLoop " << this << " start loopig";

  ::poll(NULL, 0, 3*1000);

  LOG_TRACE << "EventLoop " << this << " stop loopig";

  m_looping = false;

}

void EventLoop::abortNotInLoopThread()

{

  LOG_FATAL << "EventLoop::abortNotInLoopThread - EventLoop " << this

            << " was created in threadId_ = " << m_threadId

            << ", current thread id = " <<  CurrentThread::tid();

}

EventLoop* EventLoop::getEventLoopOfCurrentThread()

{

  return t_loopInThisThread;

}

测试程序

test1

正确的逻辑.

#include <errno.h>

#include "EventLoop.hh"

#include <thread>

int main()

{

  EventLoop testloop;

  testloop.loop();

  return 0;

}

./test.out

2018-10-25 20:01:03.287601 [TRACE] [EventLoop.cpp:12] [EventLoop] EventLoop Create 0x7FFF7B1E2780 in thread 2086

2018-10-25 20:01:03.287750 [TRACE] [EventLoop.cpp:36] [loop] EventLoop 0x7FFF7B1E2780 start loopig

2018-10-25 20:01:06.291622 [TRACE] [EventLoop.cpp:40] [loop] EventLoop 0x7FFF7B1E2780 stop loopig

test2

企图在当前线程启用其他线程创建的EventLoop对象

#include <errno.h>

#include "EventLoop.hh"

#include <thread>

EventLoop* g_loop;

void test()

{

  g_loop->loop();

}

int main()

{

  EventLoop testloop;

  //testloop.loop();

  g_loop = &testloop;

  std::thread test_thread(test);

  test_thread.join();

  return 0;

}

./test.out

2018-10-25 20:05:49.618701 [TRACE] [EventLoop.cpp:12] [EventLoop] EventLoop Create 0x7FFCA55A35F0 in thread 2114

2018-10-25 20:05:49.619057 [FATAL] [EventLoop.cpp:47] EventLoop::abortNotInLoopThread - EventLoop 0x7FFCA55A35F0 was created in threadId_ = 2114, current thread id = 2115

Aborted (core dumped)