Question

从this example开始，我想将async_read()替换为async_read_until()。

所以我查了this example，看到了async_read_until()的调用方式。我看到它被称为如下：

      boost::asio::async_read_until(socket_, response_, "\r\n",
      boost::bind(&client::handle_read_status_line, this,
        boost::asio::placeholders::error));

因此，与SSL客户端示例相比，我看到的唯一区别是response_是boost::asio::streambuf。所以我以相同的方式在我的类体中创建了该对象，然后在SSL客户端示例中，我替换了回调函数：

  boost::asio::async_read(socket_,
      boost::asio::buffer(reply_, bytes_transferred),
      boost::bind(&SSLClient::handle_read, this,
        boost::asio::placeholders::error,
        boost::asio::placeholders::bytes_transferred));

使用其他功能，并删除了bytes_transferred部分。它变成了：

    boost::asio::async_read_until(socket_, response_, "\r\n",
        boost::bind(&SSLClient::handle_read, this,
        boost::asio::placeholders::error));

但是......这不会编译。它给了我这些错误：

In file included from /usr/include/boost/bind.hpp:22:0,
                 from SSLClient.h:5,
                 from main.cpp:14:
/usr/include/boost/bind/bind.hpp: In instantiation of 'struct boost::_bi::result_traits<boost::_bi::unspecified, void (SSLClient::*)(const boost::system::error_code&, long unsigned int)>':
/usr/include/boost/bind/bind_template.hpp:15:48:   required from 'class boost::_bi::bind_t<boost::_bi::unspecified, void (SSLClient::*)(const boost::system::error_code&, long unsigned int), boost::_bi::list2<boost::_bi::value<SSLClient*>, boost::arg<1> (*)()> >'
SSLClient.h:99:51:   required from here
/usr/include/boost/bind/bind.hpp:69:37: error: 'void (SSLClient::*)(const boost::system::error_code&, long unsigned int)' is not a class, struct, or union type
     typedef typename F::result_type type;
                                     ^
In file included from main.cpp:14:0:
SSLClient.h:87:70: warning: unused parameter 'bytes_transferred' [-Wunused-parameter]
     void handle_write(const boost::system::error_code& error, size_t bytes_transferred)
                                                                      ^
In file included from /usr/include/boost/asio/impl/io_service.hpp:18:0,
                 from /usr/include/boost/asio/io_service.hpp:767,
                 from /usr/include/boost/asio/basic_io_object.hpp:19,
                 from /usr/include/boost/asio/basic_socket.hpp:20,
                 from /usr/include/boost/asio/basic_datagram_socket.hpp:20,
                 from /usr/include/boost/asio.hpp:21,
                 from SSLClient.h:6,
                 from main.cpp:14:
/usr/include/boost/asio/impl/read_until.hpp: In instantiation of 'typename boost::asio::async_result<typename boost::asio::handler_type<WriteHandler, void(boost::system::error_code, long unsigned int)>::type>::type boost::asio::async_read_until(AsyncReadStream&, boost::asio::basic_streambuf<Allocator>&, const string&, ReadHandler&&) [with AsyncReadStream = boost::asio::ssl::stream<boost::asio::basic_stream_socket<boost::asio::ip::tcp> >; Allocator = std::allocator<char>; ReadHandler = boost::_bi::bind_t<boost::_bi::unspecified, void (SSLClient::*)(const boost::system::error_code&, long unsigned int), boost::_bi::list2<boost::_bi::value<SSLClient*>, boost::arg<1> (*)()> >; typename boost::asio::async_result<typename boost::asio::handler_type<WriteHandler, void(boost::system::error_code, long unsigned int)>::type>::type = void; std::string = std::basic_string<char>]':
SSLClient.h:99:52:   required from here
/usr/include/boost/asio/impl/read_until.hpp:707:3: error: static assertion failed: ReadHandler type requirements not met
   BOOST_ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;
   ^
/usr/include/boost/asio/impl/write.hpp:615:3: error: no match for call to '(boost::_bi::bind_t<boost::_bi::unspecified, void (SSLClient::*)(const boost::system::error_code&, long unsigned int), boost::_bi::list2<boost::_bi::value<SSLClient*>, boost::arg<1> (*)()> >) (const boost::system::error_code&, const long unsigned int&)'
   BOOST_ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check;
   ^
Makefile:472: recipe for target 'main.o' failed
make: *** [main.o] Error 1
13:14:05: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project GNOMEClientCmd (kit: Qt 5.4.1)
When executing step "Make"
13:14:05: Elapsed time: 00:04.

所有我必须做的就是解决所有这些错误，只需按照async_read切换到async_read_until。如果我回到async_read，它编译得很好。我做错了什么？

如果您需要任何其他信息，请询问。感谢。

Answer 1

Q值。我做错了什么

你忽略了文档。

文档会告诉您async_read-until需要一个streambuf¹，而ReadHandler需要bytes_transferred占位符。

¹刚刚注意到你在散文中描述过;显示相关代码会更好。首选SSCCE SO

boost ASIO async_read_until不用ASIO ssl客户端示例

1 个答案: