muduo源码分析之TcpConnection

相关文件

muduo/net/TcpConnection.h
muduo/net/TcpConnection.cc

作用

TcpConnection是muduo中一个连接的抽象封装，表示"一次TCP连接"。
TcpConnection没有对外的用户接口，其对象由TcpServer创建。
在TcpServer中，当Acceptor接收新连接，TcpServer在回调函数中创建TcpConnection对象（参数是已经建好连接的socketfd）。
TcpConnection是muduo中最核心最复杂的类，主要包含一个Channel和一个Socket数据成员，即包含读事件、写事件、关闭连接等事件的回调函数。

TcpConnection源码分析

构造函数与连接建立

前面说到当Acceptor接收新连接，TcpServer在回调函数中创建TcpConnection对象（参数是已经建好连接的socketfd。将用户的连接回调函数connCb()注册到TcpConnection中，再通过TcpConnection::connnectEstablished()调用。

TcpServer创建TcpConnection设置回调函数：

//TcpServer.cc
void TcpServer::newConnection(int sockfd, const InetAddress& peerAddr)
{
  loop_->assertInLoopThread();
  EventLoop* ioLoop = threadPool_->getNextLoop();
  char buf[64];
  snprintf(buf, sizeof buf, "-%s#%d", ipPort_.c_str(), nextConnId_);
  ++nextConnId_;
  string connName = name_ + buf;

  LOG_INFO << "TcpServer::newConnection [" << name_
           << "] - new connection [" << connName
           << "] from " << peerAddr.toIpPort();
  InetAddress localAddr(sockets::getLocalAddr(sockfd));
  // FIXME poll with zero timeout to double confirm the new connection
  // FIXME use make_shared if necessary
  TcpConnectionPtr conn(new TcpConnection(ioLoop,
                                          connName,
                                          sockfd,
                                          localAddr,
                                          peerAddr));
  connections_[connName] = conn;
  conn->setConnectionCallback(connectionCallback_);
  conn->setMessageCallback(messageCallback_);
  conn->setWriteCompleteCallback(writeCompleteCallback_);
  conn->setCloseCallback(
      std::bind(&TcpServer::removeConnection, this, _1)); // FIXME: unsafe
  ioLoop->runInLoop(std::bind(&TcpConnection::connectEstablished, conn));//即上面设置的连接回调函数
}

TcpConnection构造函数
在构造函数中设置了自身Channel的回调函数

TcpConnection::TcpConnection(EventLoop* loop,
                             const string& nameArg,
                             int sockfd,
                             const InetAddress& localAddr,
                             const InetAddress& peerAddr)
  : loop_(CHECK_NOTNULL(loop)),
    name_(nameArg),
    state_(kConnecting),
    reading_(true),
    socket_(new Socket(sockfd)),
    channel_(new Channel(loop, sockfd)),
    localAddr_(localAddr),
    peerAddr_(peerAddr),
    highWaterMark_(64*1024*1024)
{
  channel_->setReadCallback(
      std::bind(&TcpConnection::handleRead, this, _1));
  channel_->setWriteCallback(
      std::bind(&TcpConnection::handleWrite, this));
  channel_->setCloseCallback(
      std::bind(&TcpConnection::handleClose, this));
  channel_->setErrorCallback(
      std::bind(&TcpConnection::handleError, this));
  LOG_DEBUG << "TcpConnection::ctor[" <<  name_ << "] at " << this
            << " fd=" << sockfd;
  socket_->setKeepAlive(true);
}

调用用户的连接回调函数

void TcpConnection::connectEstablished()
{
  loop_->assertInLoopThread();
  assert(state_ == kConnecting);
  setState(kConnected);
  channel_->tie(shared_from_this());
  channel_->enableReading();

  connectionCallback_(shared_from_this());
}

关闭连接

关闭连接时序图，其中的“X”表示TcpConnection通常在此析构

muduo中的关闭连接是被动关闭。即对方先关闭，本地read返回0,触发关闭逻辑。

void TcpConnection::handleRead(Timestamp receiveTime)
{
  loop_->assertInLoopThread();
  int savedErrno = 0;
  ssize_t n = inputBuffer_.readFd(channel_->fd(), &savedErrno);
  if (n > 0)
  {
    messageCallback_(shared_from_this(), &inputBuffer_, receiveTime);
  }
  else if (n == 0)
  {
    handleClose();  //关闭连接
  }
  else
  {
    errno = savedErrno;
    LOG_SYSERR << "TcpConnection::handleRead";
    handleError();
  }
}

void TcpConnection::handleClose()
{
  loop_->assertInLoopThread();
  LOG_TRACE << "fd = " << channel_->fd() << " state = " << stateToString();
  assert(state_ == kConnected || state_ == kDisconnecting);
  // we don‘t close fd, leave it to dtor, so we can find leaks easily.
  setState(kDisconnected);
  channel_->disableAll();

  TcpConnectionPtr guardThis(shared_from_this());
  connectionCallback_(guardThis);
  // must be the last line
  closeCallback_(guardThis);  //由TcpServer/Client注册，通知其移除连接指针
}

TcpServer/Client移除指针

void TcpServer::removeConnection(const TcpConnectionPtr& conn)
{
  // FIXME: unsafe
  loop_->runInLoop(std::bind(&TcpServer::removeConnectionInLoop, this, conn));
}

void TcpServer::removeConnectionInLoop(const TcpConnectionPtr& conn)
{
  loop_->assertInLoopThread();
  LOG_INFO << "TcpServer::removeConnectionInLoop [" << name_
           << "] - connection " << conn->name();
  size_t n = connections_.erase(conn->name());//移除
  (void)n;
  assert(n == 1);
  EventLoop* ioLoop = conn->getLoop();
  ioLoop->queueInLoop(
      std::bind(&TcpConnection::connectDestroyed, conn));
}

TcpConnection再收尾
connectDestroyed是TcpConnection析构前最后调用的一个成员函数，通知用户连接断开。

void TcpConnection::connectDestroyed()
{
  loop_->assertInLoopThread();
  if (state_ == kConnected)
  {
    setState(kDisconnected);
    channel_->disableAll();

    connectionCallback_(shared_from_this());
  }
  channel_->remove();//通知Poller取消对该通道的监听
}

muduo源码分析之TcpConnection

原文：https://www.cnblogs.com/Lj-ming/p/14806209.html