asio::async_write 的坑
同一个socket 的async_write操作内部是调用async_write_some 去执行的，在WriteDone之前，如果再次调用async_write 会导致 发送的stream顺序错乱， 典型复现是，
boost::asio::async_write(socket, buffer(xxx, 1024000), yield[ec]); boost::asio::async_write(socket, buffer(buf, 32), std::bind(&Session::write, this, std::placeholders::_1, std::placeholders::_2));
客户端收到的 数据就会乱掉，
解决方案：
添加发送队列就好了
void CAsioSession4S::HandleWriteDone(const boost::system::error_code &ec)
{
if (this->_sending != nullptr)
{
delete this->_sending;
this->_sending = nullptr;
}
//error will disconnected
if (ec)
{
while (!_sendQueue.empty())
{
delete _sendQueue.front();
_sendQueue.pop();
}
this->Disconnect();
return;
}
//检查发送队列
if (!_sendQueue.empty())
{
this->_sending = _sendQueue.front();
_sendQueue.pop();
boost::asio::async_write((*_socket.get()), this->_sending->send, std::bind(&CAsioSession4S::HandleWriteDone, this->shared_from_this(), std::placeholders::_1));
}
}