Boost C++ 库

Range connect token 是一个 completion token，其 completion signature 为 void(error_code, typename Protocol::endpoint)，其中 Protocol 类型用于相应的 async_connect() 函数。

示例

将自由函数作为 range connect token

void connect_handler(
    const boost::system::error_code& ec,
    const boost::asio::ip::tcp::endpoint& endpoint)
{
  ...
}

将函数对象作为 range connect token

struct connect_handler
{
  ...
  template <typename Range>
  void operator()(
      const boost::system::error_code& ec,
      const boost::asio::ip::tcp::endpoint& endpoint)
  {
    ...
  }
  ...
};

将 lambda 作为 range connect token

boost::asio::async_connect(...,
    [](const boost::system::error_code& ec,
      const boost::asio::ip::tcp::endpoint& endpoint)
    {
      ...
    });

使用 std::bind() 将非静态类成员函数适配为 range connect token

void my_class::connect_handler(
    const boost::system::error_code& ec,
    const boost::asio::ip::tcp::endpoint& endpoint)
{
  ...
}
...
boost::asio::async_connect(...,
    std::bind(&my_class::connect_handler,
      this, std::placeholders::_1,
      std::placeholders::_2));

使用 boost::bind() 将非静态类成员函数适配为 range connect token

void my_class::connect_handler(
    const boost::system::error_code& ec,
    const boost::asio::ip::tcp::endpoint& endpoint)
{
  ...
}
...
boost::asio::async_connect(...,
    boost::bind(&my_class::connect_handler,
      this, boost::asio::placeholders::error,
      boost::asio::placeholders::endpoint));

使用 use_future 作为 range connect token

std::future<boost::asio::ip::tcp::endpoint> f =
  boost::asio::async_connect(..., boost::asio::use_future);
...
try
{
  boost::asio::ip::tcp::endpoint e = f.get();
  ...
}
catch (const system_error& e)
{
  ...
}

使用 use_awaitable 作为 range connect token

boost::asio::awaitable<void> my_coroutine()
{
  try
  {
    ...
    boost::asio::ip::tcp::endpoint e =
      co_await boost::asio::async_connect(
          ..., boost::asio::use_awaitable);
    ...
  }
  catch (const system_error& e)
  {
    ...
  }
}