的boost ::支持ASIO :: async_read綁定編譯錯誤

Question

我想不通，爲什麼我得到這個錯誤：

/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 

這裏我的課： 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; 
      } 
     } 

    } 
    } 
} 

檢查代碼塊上的「** Error pointing this line **」，這是它存在問題的原因......不知道爲什麼，一次又一次打破了我的頭......

感謝您的幫助

我已刪除了清楚起見，一些代碼，如果你有任何問題，請不要猶豫

Answer 1

您完成處理程序的簽名是不正確的，考慮這個例子

#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是足夠聰明的error或bytes_transferred參數不傳遞給您綁定的函數指針。 Asio圖書館的作者有一個detailed blog post關於使用綁定與圖書館。這是值得的閱讀。

Answer 2

的async_ *操作需要回調函數不同的簽名：

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

請在有一些例子如何編寫和調用這個回調處理程序的文檔更深入的瞭解。