...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Spawn a new coroutined-based thread of execution.
template< typename Executor, typename T, typename AwaitableExecutor, typename CompletionToken = DEFAULT> DEDUCED co_spawn( const Executor & ex, awaitable< T, AwaitableExecutor > a, CompletionToken && token = DEFAULT, constraint_t<(is_executor< Executor >::value||execution::is_executor< Executor >::value) &&is_convertible< Executor, AwaitableExecutor >::value > = 0);
The executor that will be used to schedule the new thread of execution.
The awaitable
object that is
the result of calling the coroutine's entry point function.
The completion token that will handle the notification that the thread of execution has completed. The function signature of the completion handler must be:
void handler(std::exception_ptr, T);
void(std::exception_ptr, T)
boost::asio::awaitable<std::size_t> echo(tcp::socket socket) { std::size_t bytes_transferred = 0; try { char data[1024]; for (;;) { std::size_t n = co_await socket.async_read_some( boost::asio::buffer(data), boost::asio::use_awaitable); co_await boost::asio::async_write(socket, boost::asio::buffer(data, n), boost::asio::use_awaitable); bytes_transferred += n; } } catch (const std::exception&) { } co_return bytes_transferred; } // ... boost::asio::co_spawn(my_executor, echo(std::move(my_tcp_socket)), [](std::exception_ptr e, std::size_t n) { std::cout << "transferred " << n << "\n"; });
The new thread of execution is created with a cancellation state that supports
cancellation_type::terminal
values only. To change the cancellation
state, call this_coro::reset_cancellation_state
.