浅析 boost::asio in C++20 coroutine 的调度器实现
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()); } } ...