c++ - boost ASIO async_read_until 不编译 ASIO ssl 客户端示例

Question

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

所以我查了一下this example ，并查看了如何调用 async_read_until()。我看到它的名称如下:

      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_ 是一个 boost::asio::streambuf。因此，我以相同的方式在我的类主体中创建了该对象，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));

与其他功能，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...这无法编译。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.

要获得所有这些错误，我所要做的就是按照说明从 async_read 切换到 async_read_until。如果我返回 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。谢谢。

Answer 1

Q. What Am I doing wrong

您忽略了文档。

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

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¹ 刚刚注意到您在散文中描述了这一点；显示相关代码效果更好。喜欢SSCCE就这样