的boost ::支持ASIO :: async_read绑定编译错误

Question

我想不通，为什么我得到这个错误：

/usr/local/include/boost/asio/impl/read.hpp: In member function ‘void boost::asio::detail::read_op<AsyncReadStream, boost::asio::mutable_buffers_1, CompletionCondition, ReadHandler>::operator()(const boost::system::error_code&, size_t, int) [with AsyncReadStream = boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >, CompletionCondition = boost::asio::detail::transfer_at_least_t, ReadHandler = boost::function<void()(long unsigned int)>]’: 
/usr/local/include/boost/asio/impl/read.hpp:263: instantiated from ‘void boost::asio::async_read(AsyncReadStream&, const MutableBufferSequence&, CompletionCondition, ReadHandler) [with AsyncReadStream = boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >, MutableBufferSequence = boost::asio::mutable_buffers_1, CompletionCondition = boost::asio::detail::transfer_at_least_t, ReadHandler = boost::function<void()(long unsigned int)>]’ 
src/communicator/protocol/Command.cc:34: instantiated from here 
/usr/local/include/boost/asio/impl/read.hpp:215: error: no match for call to ‘(boost::function<void()(long unsigned int)>) (const boost::system::error_code&, const long unsigned int&)’ 
/usr/local/include/boost/function/function_template.hpp:1007: note: candidates are: typename boost::function1<R, T1>::result_type boost::function1<R, T1>::operator()(T0) const [with R = void, T0 = long unsigned int] 
make: *** [src/communicator/protocol/Command.o] Error 1 

这里我的课： Command.hh

namespace communicator {            
    namespace protocol {             
    namespace in {              
     class Command : public boost::enable_shared_from_this<Command> { 
     public:               
     ~Command();             

     typedef boost::shared_ptr<Command>  pointer;    

     void got_newline();           

     protected:              
     Command(tcp::socket& socket, structure::Client& client) :  
      m_socket(socket), m_client(client) {}; 

     void endParsing(); 

     tcp::socket&   m_socket;        

     structure::Client&  m_client;        
     char     m_newline[2];       
     private:        

     };                
    } 
} 

Command.cc ：

namespace communicator { 
    namespace protocol { 
    namespace in { 

     void Command::endParsing() { 
     boost::function<void()> cb = boost::bind(&Command::got_newline, 
              shared_from_this()); 
     boost::asio::async_read(m_socket, 
           boost::asio::buffer(m_newline, 2), 
           boost::asio::transfer_at_least(2), 
**ERROR POINTING THIS LINE**         cb); 
     } 

     void Command::got_newline() { 
     if (m_newline[0] == '\r' && m_newline[1] == '\n') { 
      std::cout << "End" << std::endl; 
      } 
     } 

    } 
    } 
} 

检查代码块上的“** Error pointing this line **”，这是它存在问题的原因......不知道为什么，一次又一次打破了我的头......

感谢您的帮助

我已删除了清楚起见，一些代码，如果你有任何问题，请不要犹豫

Answer 1

您完成处理程序的签名是不正确的，考虑这个例子

#include <boost/asio.hpp> 

#include <boost/function.hpp> 
#include <boost/bind.hpp> 

void 
foo() 
{ 

} 

int 
main() 
{ 
    boost::asio::io_service io_service; 
    boost::asio::ip::tcp::socket socket(io_service); 

    char buf[2]; 

    // this compiles file 
    boost::asio::async_read(
      socket, 
      boost::asio::buffer(buf), 
      boost::asio::transfer_at_least(2), 
      boost::bind(&foo) 
      ); 

    // this does not 
    boost::function<void()> cb = boost::bind(&foo); 
    boost::asio::async_read(
      socket, 
      boost::asio::buffer(buf), 
      boost::asio::transfer_at_least(2), 
      cb 
      ); 

} 

boost::bind是足够聪明的error或bytes_transferred参数不传递给您绑定的函数指针。 Asio图书馆的作者有一个detailed blog post关于使用绑定与图书馆。这是值得的阅读。

Answer 2

的async_ *操作需要回调函数不同的签名：

void handler(
    const boost::system::error_code& error, // Result of operation. 
    std::size_t bytes_transferred   // Number of bytes read. 
); 

请在有一些例子如何编写和调用这个回调处理程序的文档更深入的了解。