Question

我在类中重载了shift运算符以提供输入。我在该方法中执行同步asio::write()，然后立即执行异步asio::async_read()。我的问题是班次超载需要成为我班上的朋友。

如果我将其提供给async_read：

void operator>>(const vector<unsigned char> input, Socket &socket) {
      const size_t size = input.size();
      const size_t bytes = asio::write(socket.connection_socket, asio::buffer(input, size));
      if (bytes != size) {
        const std::error_code ec;
        throw std::system_error(ec, fmt::format("Tried to send {0} bytes but sent {1} instead.", size, bytes));
      }
      asio::async_read(socket.connection_socket,
                       asio::buffer(socket.read_buffer),
                       std::bind(&Socket::handle_async_read,
                                 this,
                                 std::placeholders::_1));
    }

我收到错误：

error: invalid use of 'this' outside of a non-static member function

如果我将引用传递给socket：

void operator>>(const vector<unsigned char> input, Socket &socket) {
      const size_t size = input.size();
      const size_t bytes = asio::write(socket.connection_socket, asio::buffer(input, size));
      if (bytes != size) {
        const std::error_code ec;
        throw std::system_error(ec, fmt::format("Tried to send {0} bytes but sent {1} instead.", size, bytes));
      }
      asio::async_read(socket.connection_socket,
                       asio::buffer(socket.read_buffer),
                       std::bind(&Socket::handle_async_read,
                                 socket,
                                 std::placeholders::_1));
    }

我收到错误：

error: call to implicitly-deleted copy constructor of 'std::__1::__bind<void
      (databaseclient::internal::Socket::*)(std::__1::error_code &, unsigned long), databaseclient::internal::Socket &, std::__1::placeholders::__ph<1> &>'
  ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Answer 1

您正在绑定套接字的副本，这是非法的。

这样更好：

asio::async_read(socket.connection_socket,
                       asio::buffer(socket.read_buffer),
                       std::bind(&Socket::handle_async_read,
                                 std::ref(socket),
                                 std::placeholders::_1));

这甚至更好（因为绑定是不合时宜的）：

asio::async_read(socket.connection_socket,
                       asio::buffer(socket.read_buffer),
                       [&socket](auto const& ec, auto transferred) 
                       {
                         handle_async_read(socket, ec);
                       });

使用朋友方法

1 个答案: