Boost C++ 库

解析令牌是一个 完成令牌，其完成签名是 void(error_code, ip::basic_resolver_results<InternetProtocol>)， 针对指定的 InternetProtocol。

示例

作为解析令牌的自由函数

void resolve_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::results_type results)
{
  ...
}

解析令牌函数对象

struct resolve_handler
{
  ...
  void operator()(
      const boost::system::error_code& ec,
      boost::asio::ip::tcp::resolver::results_type results)
  {
    ...
  }
  ...
};

作为解析令牌的 Lambda 表达式

resolver.async_resolve(...,
    [](const boost::system::error_code& ec,
      boost::asio::ip::tcp::resolver::results_type results)
    {
      ...
    });

使用 std::bind() 改编为解析令牌的非静态类成员函数

void my_class::resolve_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::results_type results)
{
  ...
}
...
resolver.async_resolve(...,
    std::bind(&my_class::resolve_handler,
      this, std::placeholders::_1,
      std::placeholders::_2));

使用 boost::bind() 改编为解析令牌的非静态类成员函数

void my_class::resolve_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::results_type results)
{
  ...
}
...
resolver.async_resolve(...,
    boost::bind(&my_class::resolve_handler,
      this, boost::asio::placeholders::error,
      boost::asio::placeholders::results));

使用 use_future 作为解析令牌

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

使用 use_awaitable 作为解析令牌

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