浅析 boost::asio in C++20 coroutine 的调度器实现

Mon, 06 Apr 2026 12:00:00 +0800

引言

本文会从一个简易的 echo 回显服务的例子开始，解析各个类的实现和原理，解析 asio 在 C++20 coroutine 下的异步 I/O 全流程

echo_server.cpp

// ref https://www.boost.org/doc/libs/latest/doc/html/boost_asio/example/cpp20/coroutines/echo_server.cpp
#include <boost/asio.hpp>
#include <cstdio>

using boost::asio::ip::tcp;
using boost::asio::awaitable;
using boost::asio::co_spawn;
using boost::asio::detached;
using boost::asio::use_awaitable;
namespace this_coro = boost::asio::this_coro;

#if defined(BOOST_ASIO_ENABLE_HANDLER_TRACKING)
# define use_awaitable \
  boost::asio::use_awaitable_t(__FILE__, __LINE__, __PRETTY_FUNCTION__)
#endif

awaitable<void> echo(tcp::socket socket) {
  try {
    char data[1024];
    for (;;) {
      std::size_t n = co_await socket.async_read_some(boost::asio::buffer(data), use_awaitable);
      co_await async_write(socket, boost::asio::buffer(data, n), use_awaitable);
    }
  } catch (std::exception &e) {
    std::printf("echo Exception: %s\n", e.what());
  }
}

awaitable<void> listener() {
  auto executor = co_await this_coro::executor;
  tcp::acceptor acceptor(executor, {tcp::v4(), 55555});
  for (;;) {
    tcp::socket socket = co_await acceptor.async_accept(use_awaitable);
    co_spawn(executor, echo(std::move(socket)), detached);
  }
}

int main() {
  try {
    boost::asio::io_context io_context(1);
    boost::asio::signal_set signals(io_context, SIGINT, SIGTERM);
    signals.async_wait([&](auto, auto){ io_context.stop(); });

    co_spawn(io_context, listener(), detached);

    io_context.run();
  } catch (std::exception &e) {
    std::printf("Exception: %s\n", e.what());
  }
}

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浅析 boost::asio in C++20 coroutine 的调度器实现

引言