Boost ASIO: Coroutines

Abstract

Since version 1.54.0, Boost.Asio supports coroutines. While you could use Boost.Coroutine directly, explicit support of coroutines in Boost.Asio makes it easier to use them.

Coroutines let you create a structure that mirrors the actual program logic. Asynchronous operations don’t split functions, because there are no handlers to define what should happen when an asynchronous operation completes. Instead of having handlers call each other, the program can use a sequential structure.

从版本1.54.0开始，Boost。Asio支持协同程序。而您可以使用Boost。直接协程，在Boost中显式支持协程。Asio使它们更容易使用。

Demo

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace boost::asio;
using namespace boost::asio::ip;

io_service ioservice;
tcp::endpoint tcp_endpoint{tcp::v4(), 2014};
tcp::acceptor tcp_acceptor{ioservice, tcp_endpoint};
std::list tcp_sockets;

void do_write(tcp::socket &tcp_socket, yield_context yield)
{
  std::time_t now = std::time(nullptr);
  std::string data = std::ctime(&now);
  async_write(tcp_socket, buffer(data), yield);
  tcp_socket.shutdown(tcp::socket::shutdown_send);
}

void do_accept(yield_context yield)
{
  for (int i = 0; i < 2; ++i)
  {
    tcp_sockets.emplace_back(ioservice);
    tcp_acceptor.async_accept(tcp_sockets.back(), yield);
    spawn(ioservice, [](yield_context yield)
      { do_write(tcp_sockets.back(), yield); });
  }
}

int main()
{
  tcp_acceptor.listen();
  spawn(ioservice, do_accept);
  ioservice.run();
}

Asio boost:: Asio:: spawn()。传递的第一个参数必须是一个I/O服务对象。第二个参数是将作为协程的函数。这个函数必须接受boost::asio::yield_context类型的对象作为它的唯一参数。它必须没有返回值。例32.7使用do_accept()和do_write()作为协程。如果函数签名不同，如do_write()的情况，则必须使用std::bind或lambda函数等适配器。