c++ - Boost::asio async_write_some 与 async_send

Question

我刚才才注意到boost::asio中的async_write_some和async_send(第二次重载)函数是完全一样的:

async_write_some 定义:

...
template <typename ConstBufferSequence, typename WriteHandler>
  BOOST_ASIO_INITFN_RESULT_TYPE(WriteHandler,
      void (boost::system::error_code, std::size_t))
  async_write_some(const ConstBufferSequence& buffers,
      BOOST_ASIO_MOVE_ARG(WriteHandler) handler)
  {
    // If you get an error on the following line it means that your handler does
    // not meet the documented type requirements for a WriteHandler.
    BOOST_ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check;

    return this->get_service().async_send(this->get_implementation(),
        buffers, 0, BOOST_ASIO_MOVE_CAST(WriteHandler)(handler));
  }
...

async_send 定义:

...
template <typename ConstBufferSequence, typename WriteHandler>
  BOOST_ASIO_INITFN_RESULT_TYPE(WriteHandler,
      void (boost::system::error_code, std::size_t))
  async_send(const ConstBufferSequence& buffers,
      BOOST_ASIO_MOVE_ARG(WriteHandler) handler)
  {
    // If you get an error on the following line it means that your handler does
    // not meet the documented type requirements for a WriteHandler.
    BOOST_ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check;

    return this->get_service().async_send(
        this->get_implementation(), buffers, 0,
        BOOST_ASIO_MOVE_CAST(WriteHandler)(handler));
  }
...

为什么boost::asio 库中有两个相同的函数？有什么历史原因吗？

谢谢!

Answer 1

它们提供了两种不同的抽象:

• stream.async_write_some() 允许一般写入异步流 I/O 对象。例如，此抽象允许更高级别的 async_write()一般写入 ip::tcp::socket 的组合操作, ssl:stream , serial_port等。async_write_some() 成员函数是 AsyncWriteStream 的一部分类型要求。
• socket.async_send() 允许在不考虑协议(protocol)的情况下向套接字写入数据。例如，这种抽象允许一般写入 ip::tcp::socket，ip::udp::socket 、local::*_protocol::socket 和 generic::*_protocol::socket。 socket.async_send() 的出现与已建立的 BSD 套接字 API 非常接近。