include/boost/corosio/detail/dispatch_coro.hpp
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|---|---|---|---|
| 1 | // | ||
| 2 | // Copyright (c) 2026 Vinnie Falco (vinnie.falco@gmail.com) | ||
| 3 | // Copyright (c) 2026 Steve Gerbino | ||
| 4 | // | ||
| 5 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | ||
| 6 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | ||
| 7 | // | ||
| 8 | // Official repository: https://github.com/cppalliance/corosio | ||
| 9 | // | ||
| 10 | |||
| 11 | #ifndef BOOST_COROSIO_DETAIL_DISPATCH_CORO_HPP | ||
| 12 | #define BOOST_COROSIO_DETAIL_DISPATCH_CORO_HPP | ||
| 13 | |||
| 14 | #include <boost/corosio/io_context.hpp> | ||
| 15 | #include <boost/capy/continuation.hpp> | ||
| 16 | #include <boost/capy/ex/executor_ref.hpp> | ||
| 17 | #include <boost/capy/detail/type_id.hpp> | ||
| 18 | #include <coroutine> | ||
| 19 | |||
| 20 | namespace boost::corosio::detail { | ||
| 21 | |||
| 22 | /** Returns a handle for symmetric transfer on I/O completion. | ||
| 23 | |||
| 24 | Returns `c.h` when the executor's context is running on the | ||
| 25 | calling thread, so the awaiter resumes by symmetric transfer. | ||
| 26 | Otherwise the executor queues `c` and `noop_coroutine()` is | ||
| 27 | returned. An `io_context` executor is dispatched without type | ||
| 28 | erasure. | ||
| 29 | |||
| 30 | Callers in coroutine machinery should return the result | ||
| 31 | for symmetric transfer. Callers at the scheduler pump | ||
| 32 | level should call `.resume()` on the result. | ||
| 33 | |||
| 34 | @note A `dispatch` that throws calls `std::terminate`. | ||
| 35 | |||
| 36 | @param ex The executor to dispatch through. | ||
| 37 | @param c The continuation to dispatch. Must remain at a | ||
| 38 | stable address until dequeued by the executor. | ||
| 39 | |||
| 40 | @return A handle for symmetric transfer or `std::noop_coroutine()`. | ||
| 41 | */ | ||
| 42 | inline std::coroutine_handle<> | ||
| 43 | 490548x | dispatch_coro(capy::executor_ref ex, capy::continuation& c) noexcept | |
| 44 | { | ||
| 45 | // An exception from dispatch would leave the completed operation | ||
| 46 | // with nobody to resume or abandon its coroutine. | ||
| 47 | // A completion from another context must not resume the awaiter | ||
| 48 | // on this thread, so the fast path still asks the executor. | ||
| 49 | 490548x | if (auto const* io_ex = ex.target<io_context::executor_type>()) | |
| 50 | 489417x | return io_ex->dispatch(c); | |
| 51 | 1131x | return ex.dispatch(c); | |
| 52 | } | ||
| 53 | |||
| 54 | } // namespace boost::corosio::detail | ||
| 55 | |||
| 56 | #endif | ||
| 57 |