boost :: asio :: async_read_until问题

Question

我试图修改echo asio的echo服务器示例，当我尝试使用boost :: asio :: async_read_until时遇到了问题。下面的代码：

#include <cstdlib> 
#include <iostream> 
#include <boost/bind.hpp> 
#include <boost/asio.hpp> 

using boost::asio::ip::tcp; 

class session 
{ 
public: 
    session(boost::asio::io_service& io_service) 
    : socket_(io_service) 
    { 
    } 

    tcp::socket& socket() 
    { 
    return socket_; 
    } 

    void start() 
    { 
    std::cout<<"starting"<<std::endl; 
    boost::asio::async_read_until(socket_, boost::asio::buffer(data_, max_length), ' ', 
     boost::bind(&session::handle_read, this, 
      boost::asio::placeholders::error, 
      boost::asio::placeholders::bytes_transferred)); 
    } 

    void handle_read(const boost::system::error_code& error, 
     size_t bytes_transferred) 
    { 
    std::cout<<"handling read"<<std::endl; 
    if (!error) 
    { 
     boost::asio::async_write(socket_, 
      boost::asio::buffer(data_, bytes_transferred), 
      boost::bind(&session::handle_write, this, 
      boost::asio::placeholders::error)); 
    } 
    else 
    { 
     delete this; 
    } 
    } 

    void handle_write(const boost::system::error_code& error) 
    { 
    if (!error) 
    { 
    /* 
     socket_.async_read_some(boost::asio::buffer(data_, max_length), 
      boost::bind(&session::handle_read, this, 
      boost::asio::placeholders::error, 
      boost::asio::placeholders::bytes_transferred)); 
    */ } 
    else 
    { 
     delete this; 
    } 
    } 

private: 
    tcp::socket socket_; 
    enum { max_length = 1024 }; 
    char data_[max_length]; 
}; 

class server 
{ 
public: 
    server(boost::asio::io_service& io_service, short port) 
    : io_service_(io_service), 
     acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) 
    { 
    session* new_session = new session(io_service_); 
    acceptor_.async_accept(new_session->socket(), 
     boost::bind(&server::handle_accept, this, new_session, 
      boost::asio::placeholders::error)); 
    } 

    void handle_accept(session* new_session, 
     const boost::system::error_code& error) 
    { 
    if (!error) 
    { 
     new_session->start(); 
     new_session = new session(io_service_); 
     acceptor_.async_accept(new_session->socket(), 
      boost::bind(&server::handle_accept, this, new_session, 
      boost::asio::placeholders::error)); 
    } 
    else 
    { 
     delete new_session; 
    } 
    } 

private: 
    boost::asio::io_service& io_service_; 
    tcp::acceptor acceptor_; 
}; 

int main(int argc, char* argv[]) 
{ 
    try 
    { 
    if (argc != 2) 
    { 
     std::cerr << "Usage: async_tcp_echo_server <port>\n"; 
     return 1; 
    } 

    boost::asio::io_service io_service; 

    using namespace std; // For atoi. 
    server s(io_service, atoi(argv[1])); 

    io_service.run(); 
    } 
    catch (std::exception& e) 
    { 
    std::cerr << "Exception: " << e.what() << "\n"; 
    } 

    return 0; 
} 

问题是，当我尝试编译我得到这个奇怪的错误：

server.cpp：在成员函数“void会议::开始（）”： server.cpp ：27：错误：没有匹配函数调用'async_read_until（boost :: asio :: basic_stream_socket> &，boost :: asio :: mutable_buffers_1，char，boost :: _ bi :: bind_t，boost :: _ bi :: list3， boost :: arg < 1>（）（），boost :: arg < 2>（）（）>>）'

有人可以解释发生了什么事吗？从我可以告诉参数async_read_until是正确的。

谢谢！

Answer 1

async_read_until的第二个参数应该是streambuf object into which the data will be read。简单来说，您需要传递boost::asio::streambuf作为参考，而不是boost::asio::buffer的值。

Answer 2

const（in）正确性也可能导致此类错误消息。