How to batch send unsent messages in asio

Question

There is an example in asio, which caches the sent messages in a deque. I think when there are too many unsent messages in this deque, such as 1000, I want to process it through constbuffersequence, that is, batch sending, so the following How should the code be changed, thank you!

   void deliver(const chat_message& msg)
   {
     bool write_in_progress = !write_msgs_.empty();
     write_msgs_.push_back(msg);
     if (!write_in_progress)
     {   
       boost::asio::async_write(socket_,
           boost::asio::buffer(write_msgs_.front().data(),
             write_msgs_.front().length()),
           boost::bind(&chat_session::handle_write, shared_from_this(),
             boost::asio::placeholders::error));
     }   
   }
 
   void handle_write(const boost::system::error_code& error)
   {
     if (!error)
     {   
       write_msgs_.pop_front();
       if (!write_msgs_.empty())
       {   
         boost::asio::async_write(socket_,
             boost::asio::buffer(write_msgs_.front().data(),
               write_msgs_.front().length()),
             boost::bind(&chat_session::handle_write, shared_from_this(),
               boost::asio::placeholders::error));
       }   
     }   
     else
     {   
       room_.leave(shared_from_this());
     }   
   }